| Title of Invention | "A DIABODY MOLECULE COMPRISING A FIRST POLYPEPTIDE CHAIN AND A SECOND POLYPEPTIDE CHAIN" |
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| Abstract | The present invention is directed to diabody molecules and uses thereof in the treatment of a variety of diseases and disorders, including immunological disorders, infectious disease, intoxication and cancers, The diabody molecules of the invention comprise two polypeptide chains that associate to form at least two epitope binding sites, which may recognize the same or different epitopes on the same or differing antigens. Additionally, the antigens may be from the same or different molecules. The individual polypeptide chains of the diabody molecule may be covalently bound through non-peptide bond covalent bonds, such as, but not limited to, disulfide bonding of cysteine residues located within each polypeptide chain. In particular embodiments, the diabody molecules of the present invention further comprise an Fc region, which allows antibody-like functionality to engineered into the molecule. |
| Full Text | [0001] This application claims the benefit of U.S. Provisional Application No, 60/671,657, filed April 15, 2005, which is hereby incorporated by reference in its entirety. 1. FIELD OF THE INVENTION [0002] The present invention is directed to diabody molecules and uses thereof in , the treatment of a variety of diseases and disorders, including immunological disorders and cancers. The diabody molecules of the invention comprise at least two polypeptide chains that associate to form at least two epitope binding sites, which may recognize the same or different epitopes. Additionally, the epitopes may be from the same or different molecules or located on the same or different cells. The individual polypeptide chains of the diabody molecule may be covalently bound through non-peptide bond covalent bonds, such as, but not limited to, disulfide bonding of cysteine residues located within each polypeptide chain. In particular embodiments, the diabody molecules of the present invention further comprise an Fc region, which allows antibody-like functionality to be engineered into the molecule. 2. BACKGROUND OF THE INVENTION [0003] The design of covalent diabodies is based on the single chain Fvconstruct (scFv) (Holliger et al., 1993, Proc. Natl. Acad. Sci. USA 90:6444-6448; herein incorporated by reference in its entirety). In an intact, unmodified IgG, the VL and VH domains are located on separate polypeptide chains, i.e., the light chain and the heavy chain, respectively. Interaction of an antibody light chain and an antibody heavy chain and, in particular, interaction of VL and VH domains forms one of the epitope binding sites of the antibody. In contrast, the scFv construct comprises a VL and VH domain of an antibody contained in a single polypeptide chain wherein the domains are separated by a flexible linker of sufficient length to allow self-assembly of the two domains into a functional epitope binding site. Where self assembly of the is impossible due to a linker of insufficient length (less than about 12 amino acid residues), two of the scFv constructs interact with each other to form a bivalent molecule, the VL of one chain associating with the VH of the other (reviewed in Marvin et al., 2005, Acta Pharmacol. Sin. 26:649-658). Moreover, addition of a cysteine residue to the c-terminus of the construct has been show to allow disulfide bonding of the polypeptide chains, stabilizing the resulting dimer without interfering with the binding characteristics of the bivalent molecule (see e.g., Olafsen et al., 2004, Prot. Engr. Des. Sel. 17:21-27). Further, where VL and VH domains of differing specificity are selected, not only a bivalent, but also a bispccific molecule may be constructed. [0004] Bivalent diabodies have wide ranging applications including therapy and immunodiagnosis. Bivalency allows for great flexibility in the design and engineering of diabody in various applications, providing enhanced avidity to multimeric antigens, the cross-linking of differing antigens, and directed targeting to specific cell types relying on the presence of both target antigens. Due to their increased valency, low dissociation rates and rapid clearance from the circulation (for diabodies of small size, at or below ~50 kDa), diabody molecules known in the art have also shown particular use in the filed of tumor imaging (Fitzgerald et al., 1997, Protein Eng, 10:1221). Of particular importance is the cross linking of differing cells, for example the cross linking of cytotoxic T cells to tumor cells (Staerz et al., 1985, Nature 314:628-631, and Holliger et al., 1996, Protein Eng. 9:299-305). Diabody epitope binding domains may also be directed to a surface determinant of any immune effector cell such as CD3, CD 16, CD32, or CD64, which are expressed on T lymphocytes, natural killer (NK) cells or other mononuclear cells, In many studies, diabody binding to effector cell determinants, e.g., Fey receptors (FcyR), was also found to activate the effector cell (Holliger et al., 1996, Protein Eng. 9:299-305; Holliger et al., 1999, Cancer Res. 59:2909-2916). Normally, effector cell activation is triggered by the binding of an antigen bound antibody to an effector cell via Fc-FcyR interaction; thus, in this regard, diabody molecules of the invention may exhibit Ig-like functionality independent of whether they comprise an Fc domain (e.g., as assayed in any efferctor function assay known in the art or exemplified herein (e.g., ADCC assay)). By cross-linking tumor and effector cells, the diabody not only brings the effector cell within the proximity of the tumor cells but leads to effective tumor killing (see e.g., Cao and Lam, 2003, Adv. Drug. Deliv. Rev. 55:171-197, hereby incorporated by reference herein in its entirety). 2.1 EFFECTOR CELL RECEPTORS AND THEIR ROLES IN THE IMMUNE SYSTEM [0005] In traditional immune function the interaction of antibody-antigen complexes with cells of the immune system results in a wide array of responses, ranging from effector functions such as antibody-dependent cytotoxicity, mast cell degranulation, and phagocytosis to immunomodulatory signals such as regulating lymphocyte proliferation and antibody secretion. All these interactions are initiated through the binding of the Fc domain of antibodies or immune complexes to specialized cell surface receptors on hematopoietic cells. The diversity of cellular responses triggered by antibodies and immune complexes results from the structural heterogeneity of Fc receptors. Fc receptors share structurally related an antigen binding domains which presumably mediate intracellular signaling. [0006] The Fey receptors, members of the immunoglobulin gene superfamily of proteins, are surface glycoproteins that can bind the Fey portion of immunoglobulin molecules. Each member of the family recognizes immunoglobulins of one or more isotypes through a recognition domain on the alpha chain of the Fey receptor. Fey receptors are defined by their specificity for immunoglobulin subtypes. Fey receptors for IgG are referred to as FcyR, for IgE as FcsR, and for IgA as FcaR. Different accessory cells bear Fey receptors for antibodies of different isotype, and the isotype of the antibody determines which accessory cells will be engaged in a given response (reviewed by Ravetch J.V. et al 1991, Annu. Rev. Immunol. 9: 457-92; Gerber J.S. et al. 2001 Microbes and Infection, 3: 131-139; Billadeau D.D. et al. 2002, The Journal of Clinical Investigation, 2(109): 161- 1681; Ravetch J.V. et al. 2000, Science, 290: 84-89; Ravetch J.V. et al, 2001 Annu. Rev. Immunol. 19:275-90; Ravetch J.V. 1994, Cell, 78(4): 553-60). The different Fey receptors, the cells that express them, and their isotype specificity is summarized in Table 1 (adapted from Immunobiology: The Immune System in Health and Disease, 4th ed. 1999, Elsevier Science Ltd/Garland Publishing, New York). [0007] Fey Receptors [0008] Each member of this family is an integral membrane glycoprotein, possessing extracellular domains related to a C2-set of immunoglobulin-related domains, a single membrane spanning domain and an intracytoplasmic domain of variable length. There are three known FcyRs, designated FcyRI(CD64), FcyRII(CD32), and FcyRIII(CD16). The three receptors are encoded by distinct genes; however, the extensive homology between the three family members suggest they arose from a common progenitor perhaps by gene duplication. [0009] FcyRII(CD32) [0010] FcyRII proteins are 40 kDa integral membrane glycoproteins which bind only the complexed IgG due to a low affinity for monomeric Ig (106 tvf1). This receptor is the most widely expressed FcyR, present on all hematopoietic cells, including monocytes, macrophages, B cells, NK. cells, neutrophils, mast cells, and platelets. FcyRII has only two immunoglobulin-like regions in its immunoglobulin binding chain and hence a much lower affinity for IgG than FcyRI. There are three human FcyRII genes (FcyRII-A, FcyRII-B, FcyRII-C), all of which bind IgG in aggregates or immune complexes. [0011] Distinct differences within the cytoplasmic domains of FcyRII-A and FcyRII-B create two functionally heterogenous responses to receptor ligation. The fundamental difference is that the A isoforra initiates intracellular signaling leading to cell activation such as phagocytosis and respiratory burst, whereas the B isoform initiates inhibitory signals, e.g., inhibiting B-cell activation. [0012] FcyRIIl(CD 16) [0013] Due to heterogeneity within this class, the size of FcyRIIl ranges between 40 and 80 kDa in mouse and man. Two human genes encode two transcripts, FcyRIIIA, an integral membrane glycoprotein, and FcyRIIIB, a glycosylphosphatidyl-inositol (GPI)- linked version. One murine gene encodes an FcyRIIl homologous to the membrane spanning human FcyRIIIA. The FcyRIIl shares structural characteristics with each of the other two FcyRs. Like FcyRH, FcyRIIl binds IgG with low affinity and contains the corresponding two extracellular Ig-like domains. FcyRIIIA is expressed in macrophagcs, mast cells and is the lone FcyR in NK cells. The GPI-linked FcyRIIIB is currently known to be expressed only in human neutrophils. [0014] Signaling through FcyRs [0015] Both activating and inhibitory signals are transduced through the FcyRs following ligation. These diametrically opposing functions result from structural differences among the different receptor isoforms. Two distinct domains within the cytoplasmic signaling domains of the receptor called immunoreceptor tyrosine based activation motifs (ITAMs) or immunoreceptor tyrosine based inhibitory motifs (ITIMS) account for the different responses. The recruitment of different cytoplasmic enzymes to these structures dictates the outcome of the FcyR-mediated cellular responses. ITAM-containing FcyR complexes include FcyRI, FcyRIIA, FcyRIIIA, whereas ITIM-containing complexes only include FcyRIIB, [0016] Human neutrophils express the FcyRIIA gene. FcyRIIA clustering via immune complexes or specific antibody cross-linking serves to aggregate ITAMs along with receptor-associated kinases which facilitate ITAM phosphorylation. ITAM phosphorylation serves as a docking site for Syk kinasc, activation of which results in activation of downstream substrates (e.g., PIsK). Cellular activation leads to release of proinflammatory mediators. [0017] The FcyRIIB gene is expressed on B lymphocytes; its extracellular domain is 96% identical to FcyRIIA and binds IgG complexes in an indistinguishable manner. The presence of an ITIM in the cytoplasmic domain of FcyRIIB defines this inhibitory subclass of FcyR. Recently the molecular basis of this inhibition was established. When co-ligated along with an activating FcyR, the ITIM in FcyRIIB becomes phosphorylated and attracts the SH2 domain of the inosital polyphosphate 5'-phosphatase (SHIP), which hydrolyzes phosphoinositol messengers released as a consequence of ITAM-containing FcyR-mediated tyrosine kinase activation, consequently preventing the influx of intracellular Ca""". Thus crosslinking of FcyRIIB dampens the activating response to FcyR ligation and inhibits cellular responsiveness. B cell activation, B cell proliferation and antibody secretion is thus aborted. TABLE 1. Receptors for the Fc Regions of Immunoglobulin Isotypes (Table 1 Removed) 3. SUMMARY OF THE INVENTION [0018] The present invention relates to covalent diabodies and/or covalent diabody molecules and to their use in the treatment of a variety of diseases and disorders including cancer, autoimmune disorders, allergy disorders and infectious diseases caused by bacteria, fungi or viruses. Preferably, the diabody of the present invention can bind to two different epitopes on two different cells wherein the first epitope is expressed on a different cell type than the second epitope, such that the diabody can bring the two cells together. [0019] In one embodiment, the present invention is directed to a covalent bispecific diabody, which diabody comprises a first and a second polypeptide chain, which first polypeptide chain comprises (i) a first domain comprising a binding region of a light chain variable domain of a first immunoglobulin (VL1) specific for a first epitope, (ii) a second domain comprising a binding region of a heavy chain variable domain of a second immunoglobulin (VH2) specific for a second epitope, and, optionally, (iii) a third domain comprising at least one cysteine residue, which first and second domains are covalently linked such that the first and second domains do not associate to form an epitope binding site; which second polypeptide chain comprises (i) a fourth domain comprising a binding region of a light chain variable domain of the second immunoglobulin (VL2), (ii) a fifth domain comprising a binding region of a heavy chain variable domain of the first immunoglobulin (VH1), and, optionally, (iii) a sixth domain comprising at least one cysteine residue, which fourth and fifth domains are covalently linked such that the fourth and fifth domains do not associate to form an epitope binding site; and wherein the first polypeptide chain and the second polypeptide chain are covalently linked, with the proviso that the covalent link is not a peptide bond; wherein the first domain and the fifth domain associate to form a first binding site (VL1)(VH1) that binds the first epitope; wherein the second domain and the fourth domain associate to form a second binding site (VL2)(VH2) that binds the second epitope. [0020] In another embodiment, the present invention is directed to a covalent bispecific diabody, which diabody comprises a first and a second polypeptide chain, which first polypeptide chain comprises (i) a first domain comprising a binding region of a light chain variable domain of a first immunoglobulin (VL1) specific for a first epitope, (ii) a second domain comprising a binding region of a heavy chain variable domain of a second immunoglobulin (VH2) specific for a second epitope and (iii) a third domain comprising an Fc domain or portion thereof, which first and second domains are covalently linked such that the first and second domains do not associate to form an epitope binding site; which second polypeptide chain comprises (i) a fourth domain comprising a binding region of a light chain variable domain of the second immunoglobulin (VL2), (ii) a fifth domain comprising a binding region of a heavy chain variable domain of the first immunoglobulin (VH1), which fourth and fifth domains are covalently linked such that the third and fourth domains do not associate to form an epitope binding site; and wherein the first polypeptide chain and the second polypeptide chain are covalently linked, with the proviso that the covalent link is not a peptide bond; wherein the first domain and the fifth domain associate to form a first binding site (VL1)(VH1) that binds the first epitope; wherein the second domain and the fourth domain associate to form a second binding site (VL2)(VH2) that binds the second epitope. [0021] In certain aspects, the present invention is directed to diabody molecule, which molecule comprises a first and a second polypeptide chain, which first polypeptide chain comprises (i) a first domain comprising a binding region of a light chain variable domain of a first immunoglobulin (VL1) specific for a first epitope, (ii) a second domain comprising a binding region of aheavy chain variable domain of a second immunoglobulin (VH2) specific for a second epitope and (iii) a third domain comprising an Fc domain or portion thereof, which first and second domains are covalently linked such that the first and second domains do not associate to form an epitope binding site; which second polypeptide chain comprises (i) a fourth domain comprising a binding region of a light chain variable domain of the second immunoglobulin (VL2), (ii) a fifth domain comprising a binding region of aheavy chain variable domain of the first immunoglobulin (VH1), and (iii) a sixth domain comprising at least one cysteine residue, which fourth and fifth domains are covalently linked such that the fourth and fifth domains do not associate to form an epitope binding site; and wherein the first polypeptide chain and the second polypeptide chain are covalently linked, with the proviso that the covalent link is not a peptide bond; wherein the first domain and the fifth domain associate to form a first binding site (VL1)(VH1) that binds the first epitope; wherein the second domain and the fourth domain associate to form a second binding site (VL2)(VH2) that binds the second epitope. [0022] In certain embodiments, the present invention is directed to a covalent bispecific diabody, which diabody is a dimer of diabody molecules, each diabody molecule comprising a first and a second polypeptide chain, which first polypeptide chain comprises (i) a first domain comprising a binding region of a light chain variable domain of a first unmunoglobuUn (VL1) specific for a first epitope, (ii) a second domain comprising a binding region of a heavy chain variable domain of a second immunoglobulin (VH2) 'specific for a second epitope and (iii) a third domain comprising an Fc domain or portion thereof, which first and second domains are covalently linked such that the first and second domains do not associate to form an epitope binding site; and which second polypeptide chain comprises (i) a fourth domain comprising a binding region of a light chain variable domain of the second immunoglobulin (VL2), (ii) a fifth domain comprising a binding region of a heavy chain variable domain of the first irnmunoglobulin (VH1), and (iii) a sixth domain comprising at least one cysteine residue, which fourth and fifth domains are covalently linked such that the fourth and fifth domains do not associate to form an epitope binding site; and wherein the first polypeptide chain and the second polypeptide chain of each diabody molecule are covalently linked, with the proviso that the covalent link is not a peptide bond; wherein the first domain and the fifth domain of each diabody molecule associate to form a first binding site (VL1)(VH1) that binds the first epitope; wherein the second domain and the fourth domain of each diabody molecule associate to form a second binding site (VL2)(VH2) that binds the second epitope. [0023] In yet other embodiments, the present invention is directed to a covalent tetrapecific diabody, which diabody is a dimer of diabody molecules, the first diabody molecule comprising a first and a second polypeptide chain, which first polypeptide chain comprises (i) a first domain comprising a binding region of a light chain variable domain of a first immunoglobulin (VL1) specific for a first epitope, (ii) a second domain comprising a binding region of a heavy chain variable domain of a second immunoglobulin (VH2) specific for a second epitope and (iii) a third domain comprising an Fc domain or portion thereof, which first and second domains are covalently linked such that the first and second domains do not associate to form an epitope binding site; and which second polypeptide chain comprises (i) a fourth domain comprising a binding region of a light chain variable domain of the second immunoglobulin (VL2), (ii) a fifth domain comprising a binding region of a heavy chain variable domain of the first immunoglobulin (VH1), and (iii) a sixth domain comprising at least one cysteine residue, which fourth and fifth domains are covalently linked such that the fourth and fifth domains do not associate to form an epitope binding site; and wherein the first polypeptide chain and the second polypeptide chain are covalently linked, with the proviso that the covalent link is not a peptide bond; wherein the first domain and the fifth domain associate to form a first binding site (VL1)(VH1) that binds the first epitope; wherein the second domain and the fourth domain associate to form a second binding site (VL2)(VH2) that binds the second epitope; and the second diabody molecule comprising a first and a second polypeptide chain, which first polypeptide chain comprises (i) a first domain comprising a binding region of a light chain variable domain of a third immunoglobulin (VL3) specific for a third epitope, (ii) a second domain comprising a binding region of a heavy chain variable domain of a fourth immunoglobulin (VH4) specific for a fourth epitope and (iii) a third domain comprising an Fc domain or portion thereof, which first and second domains are covalently linked such that the first and second domains do not associate to form an epitope binding site; and which second polypeptide chain comprises (i) a fourth domain comprising a binding region of a light chain variable domain of the fourth immunoglobulin (VL4), (5i) a fifth domain comprising a binding region of a heavy chain variable domain of the third immunoglobulin (VH3), and (iii) a sixth domain comprising at least one cysteine residue, which fourth and fifth domains are covalently linked such that the fourth and fifth domains do not associate to form an epitope binding site; and wherein the first polypeptide chain and the second polypeptide chain are covalently linked, with the proviso that the covalent link is not a peptide bond; wherein the first domain and the fifth domain associate to form a first binding site (VL3)(VH3) that binds the third epitope; wherein the second domain and the fourth domain associate to form a second binding site (VL4)(VH4) that binds the fourth epitope. [0024] In certain aspects of the invention the first epitope, second epitope, and where applicable, third epitope and fourth epitope can be the same. In other aspects, the first epitope, second epitope, and where applicable, third epitope and fourth epitope can each different from the other. In certain aspects of the invention comprising a third epitope binding domain, the first epitope and third epitope can be the same. In certain aspects of the invention comprising a fourth epitope binding domain, the first epitope and fourth epitope can be the same. In certain aspects of the invention comprising a third epitope binding domain, the second epitope and third epitope can be the same. In certain aspects of the invention comprising a fourth epitope binding domain, the second epitope and fourth epitope can be the same. In preferred aspects of the invention, the first eptitope and second epitope are different. In yet other aspects of the invention comprising a third epitope binding domain and a fourth epitope binding domain, the third epitope and fourth epitope can be different. It is to be understood that any combination of the foregoing is encompassed in the present invention. [0025] In particular aspects of the invention, the first domain and the fifth domain of the diabody or diabody molecule can be derived from the same immunoglobulin. In another aspect, the second domain and the fourth domain of the diabody or diabody molecule can be derived from the same immunoglobulin. In yet another aspect, the first domain and the fifth domain of the diabody or diabody molecule can be derived from a different immunoglobulin. In yet another aspect, the second domain and the fourth domain of the diabody or diabody molecule can be derived from a different immunoglobulin. It is to be understood that any combination of the foregoing is encompassed in the present invention. [0026] In certain aspects of the invention, the covalent linkage between the fist polypeptide chain and second polypeptide chain of the diabody or diabody molecule can be via a disulfide bond between at least one cysteine residue on the first polypeptide chain and at least one cysteine residue on the second polypeptide chain. The cysteine residues on the first or second polypeptide chains that are responsible for disulfide bonding can be found anywhere on the polypeptide chain including within the first, second, third, fourth, fifth and sixth domains. In a specific embodiment the cysteine residue on the first polypeptide chain is found in the first domain and the cysteine residue on the second polypeptide chain is found in the fifth domain. The first, second, fourth and fifth domains correspond to the variable regions responsible for binding. In preferred embodiments, the cysteine residues responsible for the disulfide bonding between the first and second polypeptide chains are located within the third and sixth domains, respectively. In a particular aspect of this embodiment, the third domain of the first polypeptide chain comprises the C-terminal 6 amino acids of the human kappa light chain, FNRGEC (SEQ ID N0:23), which can be encoded by the amino acid sequence (SEQ ID NO: 17). In another aspect of this embodiment, the sixth domain of the second polypeptide chain comprises the C-terminal 6 amino acids of the human kappa light chain, FNRGEC (SEQ ID NO:23), which can be encoded by the amino acid sequence (SEQ ID NO:17). In still another aspect of this embodiment, the third domain of the first polypeptide chain comprises the amino acid sequence VEPKSC (SEQ ID NO:79), derived from the hinge domain of a human IgG, and which can be encoded by the nucleotide sequence (SEQ ID N0:80). In another aspect of this embodiment, the sixth domain of the second polypeptide chain comprises the amino acid sequence VEPKSC (SEQ ID N0:79), derived from the hinge domain of a human IgG, and which can be encoded by the nucleotide sequence (SEQ ID N0:80). In certain aspects of this embodiment, the third domain of the first polypeptide chain comprises the C-terminal 6 amino acids of the human kappa light chain, FNRGEC (SEQ ID NO:23); and the sixth domain of the second polypeptide chain comprises the amino acid sequence VEPKSC (SEQ ID NO:79). In other aspects of this embodiment, the sixth domain of the second polypeptide chain comprises the C-terminal 6 amino acids of the human kappa light chain, FNRGEC (SEQ ID NO:23); and the third domain of the first polypeptide chain comprises the amino acid sequence VEPKSC (SEQ ID N0:79). In yet other aspects of this embodiment, the third domain of the first polypeptide chain comprises the C-terminal 6 amino acids of the human kappa light chain, FNRGEC (SEQ ID N0:23); and the sixth domain of the second polypeptide chain comprises a hinge domain. In other aspects of this embodiment, the sixth domain of the second polypeptide chain comprises the C-terminal 6 amino acids of the human kappa light chain, FNRGEC (SEQ ID N0:23); and the third domain of the first polypeptide chain comprises the hinge domain. In yet other aspects of this embodiment, the third domain of the first polypeptide chain comprises the C-terminal 6 amiiio acids of the human kappa light chain, FNRGEC (SEQ ID N0:23); and the sixth domain of the first polypeptide chain comprises an Fc domain, or portion thereof. In still other aspects of this embodiment, the sixth domain of the second polypeptide chain comprises the C-terminal 6 amino acids of the human kappa light chain, FNRGEC (SEQ ID N0:23); and the third domain of the first polypeptide chain comprises an Fc domain, or portion thereof. [0027] In other embodiments, the cysteine residues on the first or second polypeptide that are responsible for the disulfide bonding can be located outside of the first, second or third domains on the first polypeptide chain and outside of the fourth, fifth and sixth domain on the second polypeptide chain. In particular, the cysteine residue on the first polypeptide chain can be N-terminal to the first domain or can be C-tcrminal to the first domain. The cysteine residue on the first polypeptide chain can be N-tcrminal to the second domain or can be C-terminal to the second domain. The cysteine residue on the first polypeptide chain can be N-tcrminal to the third domain or can be C-terminal to the third domain. Further, the cysteine residue on the second polypeptide chain can be N-terminal to the fourth domain or can be C-terminal to the fourth domain. The cysteine residue on the second polypeptide chain can be N-terminal to the fifth domain or can be C-terminal to the fifth domain. Accordingly, the cysteine residue on the second polypeptide chain can be C- terminal to the sixth domain or can be N-terminal to the sixth domain. In a particular aspect, disulfide bond can between at least two cysteine residues on the first polypeptide chain and at least two cysteine residues on the second polypeptide chain. In a particular aspect, wherein the third domain and sixth domain do not comprise an Fc domain, or portion thereof, the cysteine residue can be at the C-terminus of the first polypeptide chain and at the C-terminus of the second polypeptide chain. It is to be understood that any combination of the foregoing is encompassed in the present invention. [0028J In specific embodiments of the invention described supra, the covalent diabody of the invention encompasses dimers of diabody molecules, wherein each diabody molecule comprises a first and second polypeptide chain. In certain aspects of this embodiment the diabody molecules can be covalently linked to form the dimer, with the proviso that the covalent linkage is not a peptide bond. In preferred aspects of this embodiment, the covalent linkage is a disulfide bond between at least one cysteine residue on the first polypeptide chain of each of the diabody molecules of the dimer. In yet more preferred aspects of this invention, the covalent linkage is a disulfide bond between at least one cysteine residue on the first polypeptide chain of each of the diabody molecules forming the dimer, wherein said at least one cysteine residue is located in the third domain of each first polypeptide chain. [0029] In certain aspects of the invention, the first domain on the first polypeptide chain can be N-terminal to the second domain or can be C-terminal to the second domain. The first domain on the first polypeptide chain can be N-terminal to the third domain or can be C-terminal to the third domain. The second domain on the first polypeptide chain can be N-terminal to the first domain or can be C-terminal to the first domain. Further, the second domain on the first polypeptide chain can be N-terminal to the third domain or can be C-terminal to the third domain. Accordingly, the third domain on the first polypeptide chain can be N-terminal to the first domain or can be C-terminal to the first domain. The third domain on the first polypeptide chain can be N-terminal to the second domain or can be C-terminal to the second domain. With respect to the second polypeptide chain, the fourth domain can be N-terminal to the fifth domain or can be C-terminal to the fifth domain. The fourth domain can be N-terminal to the sixth domain or can be C-terminal to the sixth domain. The fifth domain on the second polypeptide chain can be N-terminal to the fourth domain or can be C-terminal to the fourth domain. The fifth domain on the second polypeptide chain can be N-terminal to the sixth domain or can be C-terminal to the sixth domain. Accordingly the sixth domain on the second polypeptide chain can be N-terminal to the fourth domain or can be C-terminal to the fourth domain. The sixth domain on the second polypeptide chain can be N-terminal to the fifth domain or can be C-terminal to the fifth domain. It is to be understood that any combination of the foregoing is encompassed in the present invention. [0030] In certain embodiments, first domain and second domain can be located C- terminal to the third domain on the first polypeptide chain; or the first domain and second domain can be located N-terminal to the third domain on the first polypeptide chain. With respect to the second polypeptide chain, the fourth domain and fifth domain can be located C-terminal to the sixth domain, or the fourth domain and fifth domain can be located N-terminal to the sixth domain. In certain aspects of this embodiment, the present invention is directed to a covalent bispecific diabody, which diabody is a dimer of diabody molecules, each diabody molecule comprising a first and a second polypeptide chain, which first polypeptide chain comprises (5) a first domain comprising a binding region of a light chain variable domain of a first imrnunoglobulin (VL1) specific for a first epitope, (ii) a second domain comprising a binding region of a heavy chain variable domain of a second imrnunoglobulin (VH2) specific for a second epitope and (iii) a third domain comprising an Fc domain or portion thereof, which first and second domains are covalently linked such that the first and second domains do not associate to form an epitope binding site and wherein the third domain is located N-terminal to both the first domain and second domain; and which second polypeptide chain comprises (i) a fourth domain comprising a binding region of a light chain variable domain of the second immunoglobulin (VL2), (ii) a fifth domain comprising a binding region of a heavy chain variable domain of the first immunoglobulin (VH1), and (iii) a sixth domain comprising at least one cysteine residue, which fourth and fifth domains are covalently linked such that the fourth and fifth domains do not associate to form an epitope binding site; and wherein the first polypeptide chain and the second polypeptide chain of each diabody molecule are covalently linked, with the proviso that the covalent link is not a peptide bond; wherein the first domain and the fifth domain of each diabody molecule associate to form a first binding site (VL1)(VH1) that binds the first epitope; wherein the second domain and the fourth domain of each diabody molecule associate to form a second binding site (VL2)(VH2) mat binds the second epitope. [0031] In yet another embodiment, the present invention is directed to a covalent tetrapecific diabody, which diabody is a dimer of diabody molecules, the first diabody molecule comprising a first and a second polypeptide chain, which first polypeptide chain comprises (i) a first domain comprising a binding region of a light chain variable domain of a first immunoglobulin (VL1) specific for a first epitope, (ii) a second domain comprising a binding region of a heavy chain variable domain of a second immunoglobulin (VH2) specific for a second epitope and (iii) a third domain comprising an Fc domain or portion thereof, which first and second domains are covalently linked such that the first and second domains do not associate to form an epitope binding site and wherein the third domain is located N-terminal to both the first domain and second domain; and which second polypeptide chain comprises (i) a fourth domain comprising a binding region of a light chain variable domain of the second immunoglobulin (VL2), (ii) a fifth domain comprising a binding region of a heavy chain variable domain of the first immunoglobulin (VH1), and (iii) a sixth domain comprising at least one cysteine residue, which fourth and fifth domains are covalently linked such that the fourth and fifth domains do not associate to form an epitope binding site; and wherein the first polypeptide chain and the second polypeptide chain are covalently linked, with the proviso that the covalent link is not a peptide bond; wherein the first domain and the fifth domain associate to form a first binding site (VL1)(VH1) that binds the first epitope; wherein the second domain and the fourth domain associate to form a second binding site (VL2)(VH2) that binds the second epitope; and the second diabody molecule comprises a first and a second polypeptide chain, which first polypeptide chain comprises (i) a first domain comprising a binding region of a light chain variable domain of a third hnmunoglobulin (VL3) specific for a third epitope, (ii) a second domain comprising a binding region of a heavy chain variable domain of a fourth hnmunoglobulin (VH4) specific for a fourth epitope and (iii) a third domain comprising an Fc domahl or portion thereof, which first and second domains are covalently linked such that the first and second domains do not associate to form an epitope binding site and wherein the thkd domain is located N-terminal to both the first domain and second domain; and which second polypeptide chain comprises (i) a fourth domain comprising a binding region of a light chain variable domain of the fourth immunoglobulin (VL4), (ii) a fifth domain comprising a binding region of a heavy chain variable domain of the third immunoglobulin (VH3), and (iii) a sixth domain comprising at least one cysteine residue, which fourth and fifth domains are covalently linked such that the fourth and fifth domains do not associate to form an epitope binding site; and wherein the first polypeptide chain and the second polypeptide chain are covalently linked, with the proviso that the covalent link is not a peptide bond; wherein the first domain and the fifth domain associate to form a first binding site (VL3)(VH3) that binds the third epitope; wherein the second domain and the fourth domain associate to form a second binding site (VL4)(VH4) that binds the fourth epitope, [0032] As discussed above, the domains on the individual polypeptide chains are covalently linked, hi specific aspects, the covalent link between the first and second domahl, first and third domain, second and thkd domain, fourth and fifth domain, fourth and sixth domain, and/or fifth and sixth domain can be a peptide bond. In particular, the first and second domains, and the fourth and fifth domains can be separated by the thkd domaki and sixth domain, respectively, or by additional amino acid residues, so long as the first and second, and fourth and fifth domains do not associate to form a binding site. The number of amino acid residues can be 0, 1, 2, 3,4, 5, 6, 7, 8 or 9 amino acid residues. In one preferred aspect, the number of amino acid residues between the domains is 8. [0033] hi certain aspects of the invention, the domains of the first and second polypeptid chain comprising an Fc domain, i.e., optionally, the third and sixth domains, respectively, can further comprise a hinge domain such that the domain comprises a hinge-Fc region. In alternative embodiments, the first polypeptide chain or the second polypeptide chain can comprise a hinge domain without also comprising an Fc domain. The heavy chains, light chains, hinge regions, Fc domains, and/or hinge-Fc domains for use in the invention can be derived from any immunoglobulin type including IgA, IgD, IgE, IgG or IgM. In a preferred aspect, the immunoglobulin type is IgG, or any subtype thereof, i.e., IgGi, IgG2, IgGa or IgG4. In other aspects, the immunoglobulin from which the light and heavy chains are derived is humanized or chimerized. [0034] Further, the first epitope and second epitopes, and, where applicable, third epitope and fourth epitope, to which the diabody or diabody molecule binds can be different epitopes from the same antigen or can be different epitopes from different antigens. The antigens can be any molecule to which an antibody can be generated. For example, proteins, nucleic acids, bacterial toxins, cell surface markers, autoimmune markers, viral proteins, drugs, etc. In particular aspects, at least one epitope binding site of the diabody is specific for an antigen on a particular cell, such as a B-cell, a T-cell, a phagocytic cell, a natural killer (NK) cell or a dendritic cell. [0035] In certain aspects of the present embodiment, at least one epitope binding site of the diabody or diabody molecule is specific for a Fc receptor, which Fc receptor can be an activating Fc receptor or an inhibitory Fc receptor. In particular aspects, the Fc receptor is a Fey receptor, and the Fey receptor is a FcyRI, FcyRII or FcyRIII receptor. In more preferred aspects, the FcyRIII receptor is the FcyRIIIA (CD 16 A) receptor or the FcyRIIIB (CD16B) receptor, and, more preferably, the FcyRHI receptor is the FcyRIIIA (CD16A) receptor. In another preferred aspect, the FcyRII receptor is the FcyRII A (CDS 2 A) receptor or the FcyRIIB (CD32B) receptor, and more preferably the FcyRIIB (CD32B) receptor. In a particularly preferred aspect, one binding site of the diabody is specific for CD32B and the other binding site is specific for CD16A. In a specific embodiment of the invention, at least one epitope binding site of the diabody or diabody molecule is specific for an activating Fc receptor and at least one other site is specific for an inhibitory Fc receptor. In certain aspects of this embodiment the activating Fc receptor is CD32A and the inhibitory Fc receptor is CD32B. In other aspects of this embodiment the activating Fc receptor is BCR and the inhibitory Fc receptor is CD32B. In still other aspects of this embodiment, the activating Fc receptor is IgERI and the inhibitory Fc receptor is CD32B. [0036] In cases where one epitope binding site is specific for GDI 6A, the VL and VH domains can be the same as or similar to the VL and VH domains of the mouse antibody 3G8, the sequence of which has been cloned and is set forth herein. In other cases where one epitope binding site is specific for CD32A, the VL and VH domains can be the same as or similar to the VL and VH domains of the mouse antibody IV.3. In yet other cases where one epitope binding site is specific for CD32B, the VL and VH domains can be the same as or similar to the VL and VH domains of the mouse antibody 2B6, the sequence of which has been cloned and is set forth herein. It is to be understood that any of the VL or VH domains of the 3G8,2B6 and IV.3 antibodies can be used in any combination. The present invention is also directed to a bispecific diabody or diabody molecule wherein the first epitope is specific for CD32B, and the second epitope is specific for CD16A. [0037] In other aspects, an epitope binding site can be specific for a pathogenic antigen. As used herein, a pathogenic antigen is an antigen involved in a specific pathogenic disease, including cancer, infection and autoimmune disease. Thus, the pathogenic antigen can be a tumor antigen, a bacterial antigen, a viral antigen, or an autoimmune antigen. Exemplary pathogenic antigens include, but are not limited to lipopolysaccharide, viral antigens selected from the group consisting of viral antigens from human immunodeficiency virus, Adenovirus, Respiratory Syncitial Virus, West Nile Virus (e.g., El6 and/or E53 antigens) and hepatitis vims, nucleic acids (DNA and RNA) and collagen. Preferably, the pathogenic antigen is a neutralizing antigen. In a preferred aspect, where one epitope binding site is specific for CD16A or CD32A, the other epitope binding site is specific for a pathogenic antigen excluding autoimmune antigens. In yet another preferred aspect, where one epitope binding site is specific for CD32B, the other epitope binding site is specific for any pathogenic antigen. In specific embodiments, the diabody molecule of the invention binds two different antigen on the same cell, for example, one antigen binding site is specific for an activating Fc receptor while the other is specific for an inhibitory Fc receptor. In other embodiments, the diabody molecule binds two distinct viral neutralizing epitopes, for example, but not limited to, E16 and E53 of West Nile Virus. [0038] In yet another embodiment of the present invention, the diabodies of the invention can be used to treat a variety of diseases and disorders. Accordingly, the present invention is directed to a method for treating a disease or disorder comprising administering to a patient in need thereof an effective amount of a covalent diabody or diabody molecule of the invention in which at least one binding site is specific for a pathogenic antigen, such as an antigen expressed on the surface of a cancer cell or on the surface of a bacterium or virion and at least one other binding site is specific for a Fc receptor, e.g., CD16A. [0039] In yet another embodiment, the invention is directed to a method for treating a disease or disorder comprising administering to a patient in need thereof an effective amount of a diabody or diabody molecule of the invention, in which at least one binding site is specific for CD32B and at least one other binding site is specific for CD16A. [0040] In yet another embodiment, the invention is directed to a method for inducing immune tolerance to a pathogenic antigen comprising administering to a patient in need there an effective amount of a covalent diabody or dovalcnt diabody molecule of the invention, in which at least one binding site is specific for CD32B and at least one other binding site is specific for said pathogenic antigen. In aspects of this embodiment, the pathogenic antigen can be an allergen or another molecule to which immune tolerance is desired, such as a protein expressed on transplanted tissue. [0041] In yet another embodiment, the present invention is directed to a method for detoxification comprising administering to a patient in need thereof, an effective amount of a covalent diabody or diabody molecule of the invention, in which at least one binding site is specific for a cell surface marker and at least one other binding site is specific for a toxin. In particular aspects, the diabody of the invention administered is one where one binding site is specific for a cell surface marker such as an Fc and the other binding site is specific for a bacterial toxin or for a drug. In one aspect, the cell surface marker is not found on red blood cells. 3,1 DEFINITIONS [0042] Unless otherwise defined, all terms of art, notations and other scientific terms or terminology used herein are intended to have the meanings commonly understood by those of skill in the art to which this invention pertains. In some cases, terms with commonly understood meanings are defined herein for clarity and/or for ready reference, and the inclusion of such definitions herein should not necessarily be construed to represent a substantial difference over what is generally understood in the art. The practice of the present invention will employ, unless otherwise indicated, conventional techniques of molecular biology (including recombinant techniques), microbiology, cell biology, biochemistry, nucleic acid chemistry, and immunology, which are within the skill of the art. Such techniques are explained fully in the literature, such as, Current Protocols in Immunology (J. E. Coligan et ah, eds., 1999, including supplements through 2001); Current Protocols in Molecular Biology (F. M. Ausubel et al., eds., 1987, including supplements through 2001); Molecular Cloning: A Laboratory Manual, third edition (Sambrook and Russel, 2001); PCR: The Polymerase Chain Reaction, (Mullis et al., eds., 1994); The Immunoassay Handbook (D. Wild, ed., Stockton Press NY, 1994); Bioconjugate Techniques (Greg T. Hermanson, ed., Academic Press, 1996); Methods of Immunological Analysis (R. Masseyeff, W. H. Albert, andN. A. Staines, eds., Weinheim: VCH Verlags gesellschaft mbH, 1993), Harlow and Lane Using Antibodies: A Laboratory Manual Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1999; and Beaucage et al. eds., Current Protocols in Nucleic Acid Chemistry John Wiley & Sons, Inc., New York, 2000). [0043] As used herein, the terms "antibody" and "antibodies" refer to monoclonal antibodies, multispecific antibodies, human antibodies, humanized antibodies, synthetic antibodies, chimeric antibodies, polyclonal antibodies, camelized antibodies, single-chain Fvs (scFv), single chain antibodies, Fab fragments, F(ab') fragments, disulfide-linked bispecific Fvs (sdFv), intrabodies, and anti-idiotypic (anti-Id) antibodies (including, e.g., anti-Id and anti-anti-Id antibodies to antibodies of the invention), and epitope-binding fragments of any of the above. In particular, antibodies include immunoglobulin molecules and immunologically active fragments of immunoglobulin molecules, i.e., molecules that contain an antigen binding site. Immunoglobulin molecules can be of any type (e.g., IgG, IgE, IgM, IgD, IgA and IgY), class (e.g., IgGj, IgG2, IgG3, IgG4, IgAi and IgAa) or subclass. [0044] As used herein, the terms "immunospecifically binds," "immunospecifically recognizes," "specifically binds," "specifically recognizes" and analogous terms refer to molecules mat specifically bind to an antigen (e.g., eptiope or immune complex) and do not specifically bind to another molecule. A molecule that specifically binds to an antigen may bind to other peptides or polypeptides with lower affinity as determined by, e.g., immunoassays, BIAcore, or other assays known in the art. Preferably, molecules that specifically bind an antigen do not cross-react with other proteins. Molecules that specifically bind an antigen can be identified, for example, by immunoassays, BIAcore, or other techniques known to those of skill in the art. [0045] As used herein, immune complex, refers to a structure which forms when at least one target molecule and at least one heterologous Fey region-containing polypeptide bind to one another forming a larger molecular weight complex. Examples of immune complexes are antigen-antibody complexes which can be either soluble or particulate (e.g., an antigen/antibody complex on a cell surface.). [0046] As used herein, the terms "heavy chain," "light chain," "variable region," "framework region," "constant domain," and the like, have their ordinary meaning in the immunology art and refer to domains in naturally occurring immunoglobulins and the corresponding domains of synthetic (e.g., recombinant) binding proteins (e.g., humanized antibodies, single chain antibodies, chimeric antibodies, etc.). The basic structural unit of naturally occurring immunoglobulins (e.g., IgG) is a tetramer having two light chains and two heavy chains, usually expressed as a glycoprotein of about 150,000 Da. The amino-terminal ("N") portion of each chain includes a variable region of about 100 to 110 or more amino acids primarily responsible for antigen recognition. The carboxy-terminal ("C") portion of each chain defines a constant region, with light chains having a single constant domain and heavy chains usually having three constant domains and a hinge region. Thus, the structure of the light chains of an IgG molecule is n-V^-Ci-c and the structure of IgG heavy chains is n-VH-CHi-H-Cm-Cna-c (where H is the hinge region). The variable regions of an IgG molecule consist of the complementarity detenruning regions (CDRs), which contain the residues in contact with antigen and non-CDR segments, referred to as framework segments, which in general maintain the structure and determine the positioning of the CDR loops (although certain framework residues may also contact antigen). Thus, the VLand VHdomains have the structure n-FRl, CDR1, FR2, CDR2, FR3, CDR3, FR4-C. . [0047] When referring to binding proteins or antibodies (as broadly defined herein), the assignment of amino acids to each domain is in accordance with the definitions of Kabat, Sequences of Proteins of Immunological Interest (National Institutes of Health, •Bethesda, Md., 1987 and 1991). Amino acids from the variable regions of the mature heavy and light chains of immunoglobulins are designated by the position of an amino acid in the chain. Kabat described numerous amino acid sequences for antibodies, identified an amino acid consensus sequence for each subgroup, and assigned a residue number to each amino acid. Rabat's numbering scheme is extendible to antibodies not included in his compendium by aligning the antibody in question with one of the consensus sequences in Kabat by reference to conserved amino acids. This method for assigning residue numbers has become standard in the field and readily identifies amino acids at equivalent positions in different antibodies, including chimeric or humanized variants. For example, an amino acid at position 50 of a human antibody light chain occupies the equivalent position to an amino acid at position 50 of a mouse antibody light chain. [0048] As used herein, the term "heavy chain" is used to define the heavy chain of an IgG antibody. In an intact, native IgG, the heavy chain comprises the immunoglobulin domains VH, CHI, binge, CH2 and CHS. Throughout the,present specification, the numbering of the residues in an IgG heavy chain is that of the EU index as in Kabat et aL, Sequences of Proteins of Immunoloeical Interest'. 5th Ed. Public Health Service, NH1, MD (1991), expressly incorporated herein by references. The "EU index as in Kabat" refers to the numbering of the human IgGl EU antibody. Examples of the amino acid sequences containing human IgGl hinge, CH2 and CHS domains are shown in FIGS. 1A andlB as described, infra. FIGS. 1A and IB also set forth amino acid sequences of the hinge, CH2 and CH3 domains of the heavy chains of IgG2, IgGS and IgG4. The amino acid sequences of IgG2, IgGS and IgG4 isotypes are aligned with the IgGl sequence by placing the first and last cysteine residues of the respective hinge regions, which form the inter-heavy chain S-S bonds, in the same positions. For the IgG2 and IgG3 hinge region, not all residues are numbered by the Eu index. [0049] The "binge region" or "hinge domain" is generally defined as stretching from Glu2l6 to Pro230 of human IgGl. An example of the amino acid sequence of the human IgGl hinge region is shown in FIG. 1A (amino acid residues in FIG. 1A are numbered according to the Kabat system). Hinge regions of other IgG isotypes may be aligned with the IgGl sequence by placing the first and last cysteine residues forming inter-heavy chain S-S binds in the same positions as shown in FIG. 1A. [0050] As used herein, the term "Fc region," "Fc domain" or analogous terms are used to define a C-terminal region of an IgG heavy chain. An example of the amino acid sequence containing the human IgGl is shown in FIG. IB. Although boundaries may vary slightly, as numbered according to the Kabat system, the Fc domain extends from amino acid 231 to amino acid 447 (amino acid residues in FIG. IB are numbered according to the Kabat system). FIG. IB also provides examples of the amino acid sequences of the Fc regions of IgG isotypes IgG2, IgG3, and IgG4. [0051] The Fc region of an IgG comprises two constant domains, CH2 and CHS. The CH2 domain of a human IgG Fc region usually extends from amino acids 231 to amino acid 341 according to the numbering system of Kabat (FIG. IB). The CHS domain of a human IgG Fc region usually extends from amino acids 342 to 447 according to the numbering system of Kabat (FIG. IB). The CH2 domain of a human IgG Fc region (also referred to as "Cy2" domain) is unique in that it is not closely paired with another domain. Rather, two N-linked branched carbohydrate chains are interposed between the two CH2 domains of an intact native IgG. [0052] As used herein the terms "FcyR binding protein," "FcyR antibody," and "anti-FcyR antibody", are used interchangeably and refer to a variety of immunoglobulin-like or immunoglobulin-derived proteins. "FcyR binding proteins" bind FcyR via an interaction with VL and/or VH domains (as distinct from Fey-mediated binding). Examples of FcyR binding proteins include fully human, polyclonal, chimeric and humanized antibodies (e.g., comprising 2 heavy and 2 light chains), fragments thereof (e.g., Fab, Fab', F(ab')2, and Fv fragments), bifunctional or multifunctional antibodies (see, e.g., Lanzavecchia et al, 1987, Eur. J. Immunol. 17:105), single chain antibodies (see, e.g., Bird et at, 1988, Science 242:423-26), fusion proteins (e.g., phage display fusion proteins), "minibodies" (see, e.g., U.S. Patent No. 5,837,821) and other antigen binding proteins comprising a VL and/or VH domain or fragment thereof. In one aspect, the FcyRIIIA binding protein is a "tetrameric antibody" i.e., having generally the structure of a naturally occurring IgG and comprising variable and constant domains, i.e., two light chains comprising a VL domain and a light chain constant domain and two heavy chains comprising a VH domain and a heavy chain hinge and constant domains. [0053J As used herein the term "FcyR antagonists" and analogous terms refer to protein and non-proteinacious substances, including small molecules which antagonize at least one biological activity of an FcyR, Q.g., block signaling. For example, the molecules of the invention block signaling by blocking the binding of IgGs to an FcyR. [0054] As used herein, the term "derivative" in the context of polypeptides or proteins refers to a polypeptide or protein that comprises an amino acid sequence which has been altered by the introduction of amino acid residue substitutions, deletions or additions. The term "derivative" as used herein also refers to a polypeptide or protein which has been modified, i.e, by the covalent attachment of any type of molecule to the polypeptide or protein. For example, but not by way of limitation, an antibody may be modified, e.g., by glycosylation, acetylation, pegylation, phosphorylation, amidation, derivatization by known protecting/blocking groups, proteolytic cleavage, linkage to a cellular an antigen or other protein, etc. A derivative polypeptide or protein may be produced by chemical modifications using techniques known to those of skill in the art, including, but not limited to specific chemical cleavage, acetylation, fonnylation, metabolic synthesis of tunicamycin, etc. Further, a derivative polypeptide or protein derivative possesses a similar or identical function as the polypeptide or protein from which it was derived. [0055] As used herein, the term "derivative" in the context of a non-proteinaceous derivative refers to a second organic or inorganic molecule that is formed based upon the structure of a first organic or inorganic molecule. A derivative of an organic molecule includes, but is not limited to, a molecule modified, e.g., by the addition or deletion of a hydroxyl, methyl, ethyl, carboxyl or amine group. An organic molecxile may also be esterified, alkylated and/or phosphorylated. [0056] As used herein, the term "diabody molecule" refers to a complex of two or more polypeptide chains or proteins, each comprising at least one VL and one VH domain or fragment thereof, wherein both domains are comprised within a single polypeptide chain. In certain embodiments "diabody molecule" includes molecules comprising an Fc or a hinge-Fc domain. Said polypeptide chains in the complex may be the same or different, i.e., the diabody molecule may be a homo-multimer or a hetero-multimer. In specific aspects, "diabody molecule" includes dimers or tetramers or said polypeptide chains containing both a VL and VH domain. The individual polypeptide chains comprising the multimeric proteins may be covalently joined to at least one other peptide of the multimer by interchain disulfide bonds. {0057] As used herein, the terms "disorder" and "disease" are used interchangeably to refer to a condition in a subject. In particular, the term "autoimmune disease" is used interchangeably with the term "autoimmune disorder" to refer to a condition in a subject characterized by cellular, tissue and/or organ injury caused by an immunologic reaction of the subject to its own cells, tissues and/or organs. The term "inflammatory disease" is used interchangeably with the term "inflammatory disorder" to refer to a condition in a subject characterized by inflammation, preferably chronic inflammation. Autoimmune disorders may or may not be associated with inflammation. Moreover, inflammation may or may not be caused by an autoimmune disorder. Thus, certain disorders may be characterized as both autoimmune and inflammatory disorders. [0058] "Identical polypeptide chains" as used herein also refers to polypeptide chains having almost identical amino acid sequence, for example, including chains having one or more amino acid differences, preferably conservative amino acid substitutions, such that the activity of the two polypeptide chains is not significantly different [0059] As used herein, the term "cancer" refers to a neoplasm or tumor resulting from abnormal uncontrolled growth of cells. As used herein, cancer explicitly includes, leukemias and lymphomas. In some embodiments, cancer refers to a benign tumor, which has remained localized. In other embodiments, cancer refers to a malignant tumor, which has invaded and destroyed neighboring body structures and spread to distant sites. In some embodiments, the cancer is associated with a specific cancer antigen, [0060] As used herein, the term "irnmunornodulatory agent" and variations thereof refer to an agent that modulates a host's immune system. In certain embodiments, an immunomodulatory agent is an immunosuppressant agent. In certain other embodiments, an immunomodulatory agent is an immunostimulatory agent. Immunomodatory agents include, but are not limited to, small molecules, peptides, polypeptides, fusion proteins, antibodies, inorganic molecules, mimetic agents, and organic molecules. [0061] As used herein, the term "epitope" refers to a fragment of a polypeptide or protein or a non-protein molecule having antigenic or irnmunogenic activity in an animal, preferably in a mammal, and most preferably in a human. An epitope having immunogenic activity is a fragment of a polypeptide or protein that elicits an antibody response in an animal. An epitope having antigenic activity is a fragment of a polypeptide or protein to which an antibody immunospecifically binds as determined by any method well-known to one of skill in the art, for example by irnmunoassays. Antigenic epitopes need not necessarily be immunogenic. [0062] As used herein, the term "fragment" refers to a peptide or polypeptide comprising an amino acid sequence of at least 5 contiguous amino acid residues, at least 10 contiguous amino acid residues, at least 15 contiguous amino acid residues, at least 20 contiguous amino acid residues, at least 25 contiguous amino acid residues, at least 40 contiguous amino acid residues, at least 50 contiguous amino acid residues, at least 60 contiguous amino residues, at least 70 contiguous amino acid residues, at least contiguous 80 amino acid residues, at least contiguous 90 amino acid residues, at least contiguous 100 amino acid residues, at least contiguous 125 amino acid residues, at least 150 contiguous amino acid residues, at least contiguous 175 amino acid residues, at least contiguous 200 amino acid residues, or at least contiguous 250 amino acid residues of the amino acid sequence of another polypeptide. In a specific embodiment, a fragment of a polypeptide retains at least one function of the polypeptide. [0063] As used herein, the terms "nucleic acids" and "nucleotide sequences" include DNA molecules (e.g., cDNA or genomic DNA), RNA molecules (e.g., mRNA), combinations of DNA and RNA molecules or hybrid DNA/RNA molecules, and analogs of DNA or RNA molecules. Such analogs can be generated using, for example, nucleotide analogs, which include, but are not limited to, inosine or tritylated bases. Such analogs can also comprise DNA or RNA molecules comprising modified backbones that lend beneficial attributes to the molecules such as, for example, nuclease resistance or an increased ability to cross cellular membranes. The nucleic acids or nucleotide sequences can be single-stranded, double-stranded, may contain both single-stranded and double-stranded portions, and may contain triple-stranded portions, but preferably is double-stranded DNA. [0064] As used herein, a "therapeutically effective amount" refers to that amount of the therapeutic agent sufficient to treat or manage a disease or disorder. A therapeutically effective amount may refer to the amount of therapeutic agent sufficient to delay or .minimize the onset of disease, e.g., delay or minimize the spread of cancer. A therapeutically effective amount may also refer to the amount of the therapeutic agent that provides a therapeutic benefit in the treatment or management of a disease. Further, a therapeutically effective amount with respect to a therapeutic agent of the invention means the amount of therapeutic agent alone, or in combination with other therapies, that provides a therapeutic benefit in the treatment or management of a disease. [0065] As used herein, the terms "prophylactic agent" and "prophylactic agents" refer to any agent(s) which can be used in the prevention of a disorder, or prevention of recurrence or spread of a disorder. A prophylactically effective amount may refer to the amount of prophylactic agent sufficient to prevent the recurrence or spread of hyperproliferative disease, particularly cancer, or the occurrence of such in a patient, including but not limited to those predisposed to hyperproliferative disease, for example those genetically predisposed to cancer or previously exposed to carcinogens. A prophylactically effective amount may also refer to the amount of the prophylactic agent that provides a prophylactic benefit in the prevention of disease. Further, a prophylactically effective amount with respect to a prophylactic agent of the invention means that amount of prophylactic agent alone, or in combination with other agents, that provides a prophylactic benefit in the prevention of disease. [0066] As used herein, the terms "prevent", "preventing" and "prevention" refer to the prevention of the recurrence or onset of one or more symptoms of a disorder in a subject as result of the administration of a prophylactic or therapeutic agent. [0067] As used herein, the term "in combination" refers to the use of more than one prophylactic and/or therapeutic agents. The use of the term "hi combination" does not restrict the order in which prophylactic and/or therapeutic agents are administered to a subject with a disorder. A first prophylactic or therapeutic agent can be administered prior to (e.g., 5 minutes, 15 minutes, 30 minutes, 45 minutes, 1 hour, 2 hours, 4 hours, 6 hours, 12 hours, 24 hours, 48 hours, 72 hours, 96 hours, 1 week, 2 weeks, 3 weeks, 4 weeks, 5 weeks, 6 weeks, 8 weeks, or 12 weeks before), concomitantly with, or subsequent to (e.g., 5 minutes, 15 minutes, 30 minutes, 45 minutes, 1 hour, 2 hours, 4 hours, 6 hours, 12 hours, 24 hours, 48 hours, 72 hours, 96 hours, 1 week, 2 weeks, 3 weeks, 4 weeks, 5 weeks, 6 weeks, 8 weeks, or 12 weeks after) the administration of a second prophylactic or therapeutic agent to a subject with a disorder. [0068] "Effector function" as used herein is meant a biochemical event that results from the interaction of an antibody Fc region with an Fc receptor or an antigen. Effector functions include but are not limited to antibody dependent cell mediated cytotoxicity (ADCC), antibody dependent cell mediated phagocytosis (ADCP), and complement dependent cytotoxicity (CDC). Effector functions include both those that operate after the binding of an antigen and those that operate independent of antigen binding. [0069] "Effector cell" as used herein is meant a cell of the immune system that expresses orie or more Fc receptors and mediates one or more effector functions. Effector cells include but are not limited to monocytes, macrophages, neutrophils, dendritic cells, eosinophils, mast cells, platelets, B cells, large granular lymphocytes, Langerhans1 cells, natural killer (NK) cells, and may be from any organism including but not limited to humans, mice, rats, rabbits, and monkeys. [0070] As used herein, the term "specifically binds an immune complex" and analogous terms refer to molecules that specifically bind to an immune complex and do not specifically bind to another molecule. A molecule that specifically binds to an imrmme complex may bind to other peptides or polypeptides with lower affinity as determined by, e.g., immunoassays, BIAcore, or other assays known in the art. Preferably, molecules mat specifically bind an immune complex do not cross-react with other proteins. Molecules that specifically bind an immune complex can be identified, for example, by immunoassays, BIAcore, or other techniques known to those of skill in the art. [0071] A "stable fusion protein" as used herein refers to a fusion protein that undergoes minimal to no detectable level of degradation during production and/or storage as assessed using common biochemical and functional assays known to one skilled in the art, and can be stored for an extended period of time with no loss in biological activity, e.g., binding to FcyR. 4. BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 A-B AMINO ACID SEQUENCE OF HUMAN IgG CHI, HINGE and Fc REGIONS [0072] Figure 1 provides the amino acid sequences of human IgGl, IgG2, IgG3 and IgG4 hinge (A) and Fc (B) domains. (IgGl hinge domain (SEQ ID N0:l); IgG2 hinge domain (SEQ ID NO:2); IgG3 hinge domain (SEQ ID N0:3); IgG4 hinge domain (SEQ ID N0:4); IgGl Fc domain (SEQ ID N0:5); IgG2 Fc domain (SEQ ID N0:6); IgG3 Fc domain (SEQ ID NO:7); IgGl Fc domain (SEQ ID N0:8)). The amino acid residues shown in FIGS. 1A and IB are numbered according to the numbering system of Kabat EU. Isotypc sequences are aligned with the IgGl sequence by placing the first and last cysteine residues of the respective hinge regions, which form the inter-heavy chain S-S bonds, in the same positions. For figure IB, residues in the CH2 domain are indicated by +, while residues in the CHS domain are indicated by ~. FIG. 2 SCHEMATIC REPRESENTATION OF POLYPEPTIDE CHAINS OF COVALENT BIFUNCTIONAL DIABODIES [0073] Polypeptides of a covalent, bifunctional diabody consist of an antibody VL and an antibody VH domain separated by a short peptide linker. The 8 amiuo acid residue linker prevents self assembly of a single polypeptide chain into scFv constructs, and, instead, interactions between the VL and VH domains of differing polypeptide chains predominate. 4 constructs were created (each construct is described from the amino terminus ("n"), left side of the construct, to the carboxy terminus ("c"), right side of figure): construct (1) (SEQ ID N0:9) comprised, n-the VL domain Hu2B6 - linker (GGGSGGGG (SEQ ID NO: 10)) - the VH domain of Hu3G8 - and a C-terminal sequence (LGGC)-c; construct (2) (SEQ ID NO:11) comprised n-the VL domain Hu3G8 - linker (GGGSGGGG (SEQ ID NO: 10)) - the VH domain of Hu2B6 - and a C-terminal sequence (LGGC)-c; construct (3) (SEQ ID N0:12) comprised n-the VL domain Hu3G8 - linker (GGGSGGGG (SEQ ID NO: 10)) - the VH domain of Hu3G8 - and a C-terminal sequence (LGGC)-c; construct (4) (SEQ ID NO: 13) comprised n-the VL domain Hu2B6 - linker (GGGSGGGG (SEQ ID NO: 10)) - the VH domain of Hu2B6 - and a C-terminal sequence (LGGC)-c. FIG. 3 SDS-PAGE ANALYSIS OF AFFINITY PURIFIED DIABODIES [0074] Affinity purified diabodies were subjected to SDS-PAGE analysis under reducing (lanes 1-3) or non-reducing (lanes 4-6) conditions. Approximate molecular weights of the standard (in between lanes 3 and 4) are indicated. Lanes 1 and 4, h3G8 CMD; Lanes 2 and 5, h2B6 CMD; and Lanes 3 and 6, h2B6-h3G8 CBD. FIGS. 4 A-B SEC ANALYSIS OF AFFINITY PURIFIED DIABODIES [0075] Affinity purified diabodies were subjected to SEC analysis. (A) Elution profile of known standards: full-length IgG (~150 kDa), Fab fragment of IgG (~50 kDa), and scFv (-30 kDa); (B) Elution profile of h2b6 CMD, h3G8 CMD, and h2B6-ti3G8 CBD. FIG. 5 BINDING OF h2B6-h3G8 CBD TO sCD32B AND sCD16A [0076] The binding of h2B6-h3G8 CBD to sCD32B and sCD16A was assayed hi a sandwich ELISA. sCD32B was used as the target pro tern. The secondary probe was HRP conjugated sCD16A. h3G8 CMD, which binds CD16A, was used as control. FIGS. 6 A-C BIACORE ANALYSIS OF DIABODY BINDING TO sCD16A, SCD32B AND sCD32B [0077] The binding of h2B6-h3G8 CBD, h2B6 CMD and h3G8 CMD to sCD16A, sCD32B, and sCD32A (negative control) was assayed by SPR analysis. h3G8 scFv was also tested as a control. (A) Binding to sCD16; (B) Binding to sCD32B and (C) Binding to sCD32A. Diabodies were injected at a concentration of 100 NM, and scFv at a concentration of 200 nM, over receptor surfaces at a flow rate of 50 ml/min for 60 sec. FIGS. 7 A-C BIACORE ANALYSIS OF DIABODY BINDING TO sCD16A and sCD32B [0078] The binding of h2B6-h3G8 CBD, h2B6 CMD and h3G8 CMD to sCD16A, and sCD32B was assayed by SPR analysis. h3G8 scFv was also tested as a control, (A) Binding of to h3G8 CMD sCD16A; (B) Binding of h2B6-h3G8 CBD to sCD16A; (C) Binding of h3G8 scFv to sCD16A; (D) Binding of h2B6 CMD to sCD32B; and (E) Binding of h2B6-h3G8 CBD to sCD32B. Diabodies were injected at concentrations of 6.25-200 nM over receptor surfaces at a flow rate of 70 ml/min for 180 sec. FIG. 8 SCHEMATIC DEPICTING THE INTERACTION OF POLYPEPTIDE CHAINS COMPRISING VL AND VII DOMAINS TO FORM A COVALENT BISPECIFIC DIABODY MOLECULE [0079] NHa and COOH represent the amino-terminus and carboxy terminus, respectively of each polypeptide chain. S represents the C-terminal cysteine residue on each polypeptide chain. VL and VH indicate the variable light domain and variable heavy domain, respectively. Dotted and dashed lines are to distinguish between the two polypeptide chains and, in particular, represent the linker portions of said chains. h2B6 Fv and h3G8 Fv indicate an epitope binding site specific for CD32B and CD 16, respectively. FIG. 9 SCHEMATIC REPRESENTATION OF POLYPEPTIDE CHAINS CONTAINING Fc DOMAINS OF COVALENT BISPECIFIC DIABODEES [0080] Representation of polypeptide constructs of the diabody molecules of the invention (each construct is described from the araino terminus ("n"), left side of the construct, to the carboxy terminus ("c"), right side of figure). Construct (5) (SEQ ID N0:14) comprised, n-VL domain Hu2B6 - a first linker (GGGSGGGG (SEQ ID N0:10)) -the VH domain of Hu3G8 - a second linker (LGGC)- and a C-terminal Fc domain of human IgGl-c; construct (6) (SEQ ID N0:15) comprised n-the VL domain Hu3G8 - linker (GGGSGGGG (SEQ ID NO: 10)) - the VH domain of Hu2B6 - and second linker (LGGQ-and a C-terminal Fc domain of human IgGl-c; construct (7) (SEQ ID NO: 16) comprised n-the VL domain Hu2B6 - a first linker (GGGSGGGG (SEQ ID NO: 10)) - the VH domain of Hu3G8 - and a C-terminal sequence (LGGCFNRGEC) (SEQ ID NO: 17)-c; construct (8) (SEQ ID N0:18) comprised n-the VL domain Hu3G8 - linker (GGGSGGGG (SEQ ID N0:10)) - the VH domain of Hu2B6 - and second linker (LGGC)-and a C-terminal hinge/Fc domain of human IgGl (with amino acid substitution A215V)-c. FIG.10 BINDING OF DIABODY MOLECULES COMPRISING Fc DOMAINS TO sCD32B AND sCD16A [0081] The binding of diabody molecules comprising Fc domains to sCD32B and sCD16A was assayed in a sandwich ELISA. Diabodies assayed were produced by 3 recombinant expression systems: cotransfection of pMGX669 and pMGX674, expressing constructs 1 and 6, respectively; cotransfection of pMGX667 and pMGX676, expressing constructs 2 and 5, respectively; and cotransfection of pMGX674 and pMGX676, expressing constructs 5 and 6, respectively. sCD32B was used as the target protein. The secondary probe was HKP conjugated sCDl 6A. FIG. 11 SCHEMATIC DEPICTING THE INTERACTION OF TWO POLYPEPTIDE CHAINS EACH COMPRISING AN Fc DOMAIN TO FORM A BIVALENT, COVALENT DIABODY [0082] NH2 and COOH represent the amino-terminus and carboxy terminus, • respectively of each polypeptide chain. S represents the at least one disulfide bond between a cysteine residue in the second linker sequence of each polypeptide chain. VL and VH indicate the variable light domain and variable heavy domain, respectively. Dotted and dashed lines are to distinguish between the two polypeptide chains and, in particular, represent the first linker portions of said chains. CH2 and CH3 represent the CH2 and CH3 constant domains of an Fc domain. h2B6 Fv and h3G8 Fv Indicate an epitope binding site specific for CD32B and CD 16, respectively. FIG.12 BINDING OF DIABODY MOLECULES COMPRISING HTNGE/Fc DOMAINS TO sCD32B AND sCD16A [0083] The binding of diabody molecules comprising Fc domains to sCD32B and sCD16A was assayed in a sandwich ELISA. Diabodies assayed were produced by 4 recombinant expression systems: cotransfection of pMGX669 + pMGX674, expressing constructs 1 and 6, respectively; cotransfection of pMGX669 + pMGX678, expressing constructs 2 and 8, respectively; cotransfection of pMGX677 + pMGX674, expressing constructs 7 and 6, respectively; and cotransfection of pMGX677 + pMGX678, expressing constructs 7 and 8, respectively. sCD32B was used as the target protein. The secondary probe was HRP conjugated sCD16A. FIG. 13 SCHEMATIC DEPICTING THE INTERACTION OF POLYPEPTIDE CHAINS TO FORM A TETRAMERIC DIABODY MOLECULE [0084] NHz and COOH represent the amino-terminus and carboxy terminus, respectively of each polypeptide chain. S represents the at least one disulfide bond between a cysteine residue in the second linker sequence the Fc bearing, 'heavier,' polypeptide chain and a cysteine residue in the C-terminal sequence of the non-Fc bearing, 'lighter,' • polypeptide chain. VL and VH indicate the variable light domain and variable heavy domain, respectively. Dotted and dashed lines are to distinguish between polypeptide chains and, in particular, represent the first linker portions of said heavier chains or the linker of said lighter chains. CH2 and CH3 represent the CH2 and CHS constant domains of an Fc domain. h2B6 Fv and h3G8 Fv indicate an epitope binding site specific for CD32B and CD 16, respectively. FIG. 14 SCHEMATIC REPRESENTATION OF POLYPEPTIDES CHAINS CONTAINING Fc DOMAINS WHICH Form COVALENT BISPECIFIC DIABODIES [0085] Representation of polypeptide constructs which form the diabody molecules of the invention (each constaict is described from the amino terminus ("n"), left side of the construct, to the carboxy terminus ("c"), right side of figure). Construct (9) (SEQ ID NO: 19) comprised n-a Hinge/Fc domain of human IgGl - the VL domain Hu3G8 - linker (GGGSGGGG (SEQ ID NO: 10)) - the VH domain of Hu2B6 - linker (GGGSGGGG (SEQ ID NO:10))- and a C-terminal LGGC sequence-c; construct (10) (SEQ ID NO:20) comprised n-an Fc domain of human IgGl - the VL domain Hu3G8 - linker (GGGSGGGG (SEQ ED NO: 10)) - the VH domain of Hu2B6 - linker (GGGSGGGG (SEQ ID NO: 10))-and a C-terminal LGGC sequence-c; construct (11) (SEQ ID NO:21) comprised n-the VL domain Hu2B6 (G105C) - linker (GGGSGGGG (SEQ ID N0:10)) - the VH domain of Hu3G8 - and a C-terminal hinge/Fc domain of human IgGl with amino acid substitution A21SV-c; construct (12) (SEQ ID NO:22) comprised n-the VL domain Hu3G8 - linker (GGGSGGGG (SEQ ID NO: 10)) - the VH domain of Hu2B6 (G44C) - and a C-terminal FNRGEC (SEQ ID NO:23) sequence-c. FIG. 15 A-B SDS-PAGE AND WESTERN BLOT ANALYSIS OF AFFINITY TETRAMERIC DIABODIES [0086] . Diabodies produced by recombinant expression systems cotransfected with vectors expressing constructs 10 and 1, constructs 9 and 1, and constructs 11 and 12 were subjected to SDS-PAGE analysis non-reducing conditions (A) and Western Blot analysis using goat anti-human IgGl H+L as the probe (B). Proteins in the SDS-PAGE gel were visualized with Simply Blue Safestain (Invitrogen). For both panels A and B, diabody molecules comprising constructs 10 and 1, constructs 9 and 1, and constructs 11 and 12A are in lanes 1,2 and 3, respectively. FIG.16 BINDING OF DIABODY MOLECULES COMPRISING Fc DOMAINS AND ENGINEERED INTERCHAIN DISULFIDE BONDS TO sCD32B AND sCD16A [0087] The binding of diabody molecules comprising Fc domains and engineered disulfide bonds between the 'lighter' and 'heavier' polypeptide chains to sCD32B and sCD16A was assayed in a sandwich ELISA. Diabodies assayed were produced by 3 recombinant expression systems: expressing constructs 1 and 10, expressing constructs 1 and 9, and expressing constructs 11 and 12, respectively. sCD32B was used as the target protein. The secondary probe was HRP conjugated sCD16A. Binding of h3G8 was used as control. FIG. 17 SCHEMATIC REPRESENTATION OF POLYPROTEIN PRECURSOR OF DIABODY MOLECULE AND SHCEMATIC REPRESENTATION OF POLYPEPTIDE CHAINS CONTAINING LAMBDA LIGHT CHAIN AND/OR HINGE DOMAINS [0088] Representation of polypeptide constructs which comprise the diabody molecules of the invention (each construct is described from the amino terminus ("n"), left side of the construct, to the carboxy terminus ("c"), right side of figure). Construct (13) (SEQ ID NO:97) comprised, n-VL domain 3G8 - a first linker (GGGSGGGG (SEQ ID N0:10)) - the VH domain of 2.4G2VH - a second linker (LGGQ- rurin recognition site (RAKR (SEQ ID NO:95))-VL domain of 2.4G2- a third linker (GGGSGGG (SEQ ID NO:10)-VH domain of 3G8- and a C-terminal LGGC domain; (nucleotide sequence encoding SEQ ID NO:97 is provided in SEQ ID NO:98). Construct (14) (SEQ ID NO.99) comprised, n-VL domain 3G8 - a first linker (GGGSGGGG (SEQ ED NO: 10)) - the VH domain of 2.4G2VH - a second linker (LGGC)- furin recognition site (RAKR (SEQ ID NO:95))-FMD (Foot and Mouth Disease Virus Protease C3) site-VL domain of 2.4G2- a third linker (GGGSGGG (SEQ ID NO:10)-VH domain of 3G8- and a C-terminal LGGC domain; (nucleotide sequence encoding SEQ ID N0:99 is provided in SEQ ID NO:100). Construct (15) (SEQ ID NO: 101) comprised, n-VL domain Hu2B6 - a linker (GGGSGGGG (SEQ ID N0:10)) - the VH domain of Hu3G8-and a C-terminal FNRGEC (SEQ ID NO:23) domain; (nucleotide sequence encoding SEQ ID N0:101 is provided in SEQ ID NO:102). Construct (16) (SEQ ID NO: 103) comprised, n-VL domain Hu3G8 - a linker (GGGSGGGG (SEQ ID NO: 10)) - the VH domain of Hu2B6-and a C-terminal VEPKSC (SEQ ID NO:79) domain; (nucleotide sequence encoding SEQ ID N0:103 is provided in SEQ ID NO:104). FIG. 18 BINDING OF DIABODY MOLECULES DERIVED FROM A POLYPROTEIN PRECURSOR MOLECULE TO mCD32B AND sCD16A [0089] The binding of diabody molecules derived from the polyprotein precursor molecule construct 13 (SEQ ID NO:97) to murine CD32B (mCD32B) and soluble CD16A (sCD16A) was assayed in a sandwich ELISA. mCD32B was used as the target protein. The secondary probe was biotin conjugated sCD16A. FIG.19 BINDING OF DIABODY MOLECULES COMPRISING LAMBDA CHAIN AND/OR HINGE DOMAINS TO sCD32B AND sCDlfiA [0090] The binding of diabody molecules comprising domains derived from the C- terminus of the human lambda light chain and/or the hinge domain of IgG to sCD32B and sCD16A was assayed and compared to the diabody comprising constructs 1 and 2 (FIG. 5) in a sandwich ELISA. Diabodies assayed were produced by the recombinant expression system expressing constructs 15 and 16 (SEQ ID NOrlOl and SEQ ID NO:103, respectively). sCD32B was used as the target protein. The secondary probe was HRP conjugated sCD16A. Bars with small boxes represent the construct 15/16 combination while bars with large boxes represent construct 1/2 combination. 5. DESCRIPTION OF THE PREFERRED EMBODIMENTS [0091] Each polypeptide chain of the diabody molecule comprises a VL domain and a VH domain, which are covalently linked such that the domains are constrained from self assembly. Interaction of two of the polypeptide chains will produce two VL-VH pairings, forming two eptipoe binding sites, i.e., a bivalent molecule. Neither the VH or VL domain is constrained to any position within the polypeptide chain, i.e., restricted to the amino (N) or carboxy (C) teminus, nor are the domains restricted in their relative positions to one another, i.e., the VL domain may be N-terminal to the VH domain and vice-versa. The only restriction is that a complimentary polypeptide chain be available in order to form functional diabody. Where the VL and VH domains are derived from the same antibody, the two complimentary polypeptide chains may be identical. For example, where the binding domains are derived from an antibody specific for epitope A (i.e., the binding domain is formed from a VLA-VHA interaction), each polypeptide will comprise a VHA and a VLA. Homodimerization of two polypeptide chains of the antibody will result in the formation two VLA-VHA binding sites, resulting in a bivalent monospecific antibody. Where the VL and VH domains are derived from antibodies specific for different antigens, formation of a functional bispecific diabody requires the interaction of two different polypeptide chains, i.e., formation of a heterodimer. For example, for a bispecific diabody, one polypeptide chain will comprise a VLA and a VLa; homodimerization of said chain will result in the formation of two VLA-VHB binding sites, either of no binding or of unpredictable binding. In contrast, where two differing polypeptide chains are free to interact, e.g., in a recombinant expression system, one comprising a VLA and a VHa and the other comprising a VLB and a VHA, two differing binding sites will form: VLA-VHA and VLu-VHu. For all diabody polypeptide chain pairs, the possibly of misalignment or mis- binding of the two chains is a possibility, i.e., interaction of VL-VL or VH-VH domains; however, purification of functional diabodies is easily managed based on the irnmunospecificity of the properly dimerized binding site using any affinity based method known hi the are or exemplified herein, e.g., affinity chromatography. [0092] In other embodiments, one or more of the polypeptide chains of the diabody comprises an Fc domain. Fc domains in the polypeptide chains of the diabody molecules preferentially dimerize, resulting in the formation of a diabody molecule that exhibits immunoglobulin-like properties, e.g., Fc-FcyR, interactions. Fc comprising diabodies may be dimers, e.g., comprised of two polypeptide chains, each comprising a VH domain, a VL domain and an Fc domain. Dimerization of said polypeptide chains results in a bivalent diabody comprising an Fc domain, albeit with a structure distinct from that of an unmodified bivalent antibody (FIG.l 1). Such diabody molecules will exhibit altered phenotypes relative to a wild-type immunoglobulin, e.g., altered serum half-life, binding properties, etc. In other embodiments, diabody molecules comprising Fc domains may be tetramers. Such tertramers comprise two 'heavier' polypeptide chains, i.e. a polypeptide chain comprising a VL, aVH and an Fc domain, and two 'lighter' polypeptide chains, i.e., polypeptide chain comprising a VL and a VH. Said lighter and heavier chains interact to form a monomer, and said monomers interact via their unpaired Fc domains to form an Ig-like molecule. Such an Ig-like diabody is tetravalent and may be monospecific, bispecific or tetraspecific. [0093] The at least two binding sites of the diabody molecule can recognize the same or different epitopes. Different epitopes can be from the same antigen or epitopes from different antigens. In one embodiment, the epitopes are from different cells. In another embodiment, the epitopes are cell surface antigens on the same cell or virus. The epitopes binding sites can recognize any antigen to which an antibody can be generated. For example, proteins, nucleic acids, bacterial toxins, cell surface markers, autoimmune markers, viral proteins, drugs, etc. In particular aspects, at least one epitope binding site of the diabody is specific for an antigen on a particular cell, such as a B-cell or T-cell, a phagocytotic cell, a natural killer (NK) cell or a dendritic cell. [0094] Each domain of the polypcptide chain of the diabody, z. e., the VL, VH and FC domain may be separated by a peptide linker. The peptide linker may be 0,1,2, 3,4, 5, 6,7,8, or 9. amino acids. In certain embodiments the amino acid linker sequence is GGGSGGGG (SEQ ID NO: 10) encoded by the nucleic acid sequence (SEQ ID N0:76), [0095] In certain embodiments, each polypeptide chain of the diabody molecule is engineered to comprise at least one cysteine residue that will interact with a counterpart at least one cysteine residue on a second polypeptide chain of the invention to form an interchain disulfide bond. Said interchain disulfide bonds serve to stabilize the diabody molecule, improving expression and recovery in recombinant systems, resulting in a stable and consistent formulation as well as improving the stability of the isolated and/or purified product in vivo. Said at least one cysteine residue may be introduced as a single amino acid or as part of larger amino-acid sequence, e.g. hinge domain, in any portion of the polypeptide chain. In a specific embodiment, said at least one cysteine residue is engineered to occur at the C-terminus of the polypeptide chain. In some embodiments, said at least one cysteine residue in introduced into the polypeptide chain within the amino acid sequence LGGC. In a specific embodiment, the C-terminus of the polypeptide chain comprising the diabody molecule of the invention comprises the amino acid sequence LGGC. In another embodiment, said at least one cysteine residue is introduced into the polypeptide within an amino acid sequence comprising a hinge domain, e.g. SEQ ID NO:1 or SEQ ID N0:4. In a specific embodiment, the C-terminus of a polypeptide chain of the diabody molecule of the invention comprises the amino acid sequence of an IgG hinge domain, e.g. SEQ ID NO: 1. In another embodiment, the C-terminus of a polypeptide chain of a diabody molecule of the invention comprises the amino acid sequence VEPKSC (SEQ ID NO:79), which can be encoded by nucleotide sequence (SEQ ID N0:80). In other embodiments, said at least one cysteine residue in introduced into the polypeptide chain within the ammo acid sequence LGGCFNRGEC (SEQ ID NO: 17), which can be encoded by the nucleotide sequence (SEQ ID N0:78). In a specific embodiment, the C-terminus of a polypeptide chain comprising the diabody of the invention comprises the amino acid sequence LGGCFNRGEC (SEQ ID NO: 17), which can be encoded by the nucleotide sequence (SEQ ID N0:78). In yet other embodiments, said at least one cysteine residue in introduced into the polypeptide chain within the amino acid sequence FNRGEC (SEQ ID N0:23), which can be encoded by the nucleotide sequence (SEQ ID NO-.77). In a specific embodiment, the C-terminus of a polypeptide chain comprising the diabody of the invention comprises the amino acid sequence FNRGEC (SEQ ID NO:23), which can be encoded by the nucleotide sequence (SEQ ID N0:77). [0096] In certain embodiments, the diabody molecule comprises at least two polypeptide chains, each of which comprise the amino acid sequence LGGC and are covalently linked by a disulfide bond between the cysteine residues in said LGGC sequences. In another specific embodiment, the diabody molecule comprises at least two polypeptide chains, one of which comprises the sequence FNRGEC (SEQ ID NO:23) while the other comprises a hinge domain (containing at least one cysteine residue), wherein said at least two polypeptide chains are covalently linked by a disulfide bond between the cysteine residue in FNRGEC (SEQ ID NO:23) and a cysteine residue in the hinge domain. In particular aspects, the cysteine residue responsible for the disulfide bond located in the hinge domain is Cys-128 (as numbered according to Kabat EU; located in the hinge domain of an unmodified, intact IgG heavy chain) and the counterpart cysteine residue in SEQ ID NO:23 is Cys-214 (as numbered according to Kabat EU; located at the C-terminus of an unmodified, intact IgG light chain) (Elkabetz et al., 2005, J. Biol. Chem. 280:14402-14412; hereby incorporated by reference herein in its entirety). In yet other embodiments, the at least one cysteine residue is engineered to occur at the N-terminus of the amino acid chain. In still other embodiments, the at least one cysteine residue is engineered to occur in the linker portion of the polypeptide chain of the diabody molecule. In further embodiments, the VH or VL domain is engineered to comprise at least one amino acid modification relative to the parental VH or VL domain such that said amino acid modification comprises a substitution of a parental amino acid with cysteine. [0097] The invention encompasses diabody molecules comprising an Fc domain or portion thereof (e.g. a CH2 domain, or CH3 domain). The Fc domain or portion thereof may be derived from any immunoglobulin isotype or allotype including, but not limited to, IgA, IgD, IgG, IgE and IgM. In preferred embodiments, the Fc domain (or portion thereof) is derived from IgG. In specific embodiments, the IgG isotype is IgGl, IgG2, IgG3 or IgG4 or an allotype thereof. In one embodiment, the diabody molecule comprises an Fc domain, which Fc domain comprises a CH2 domain and CH3 domain independently selected from any immunoglobulin isotype (i.e. an Fc domain comprising the CH2 domain derived from IgG and the CH3 domain derived form IgE, or the CH2 domain derived from IgGl and the CHS domain derived from IgG2, etc.). Said Fc domain may be engineered into a polypeptide chain comprising the diabody molecule of the invention in any position relative to other domains or portions of said polypeptide chain (e.g., the Fc domain, or portion thereof, may be c-terminal to both the VL and VH domains of the polypeptide of the chain; may be n-terminal to both the VL and VH domains; or may be N-terminal to one domain and c-terminal to another (i.e., between two domains of the polypeptide chain)). [0098] The present invention also encompasses molecules comprising a hinge domain. The hinge domain be derived from any immunoglobulin isotype or allotype including IgA, IgD, IgG, IgE and IgM. In preferred embodiments, the hinge domain is derived from IgG, wherein the IgG isotype is IgGl, IgG2, IgG3 or IgG4, or an allotpye thereof. Said hinge domain may be engineered into a polypeptide chain comprising the diabody molecule together with an Fc domain such that the diabody molecule comprises a hinge-Fc domain. In certain embodiments, the hinge and Fc domain are independently selected from any immunoglobulin isotype known in the art or exemplified herein. In other embodiments the hinge and Fc domain are separated by at least one other domain of the polypeptide chain, e.g., the VL domain. The hinge domain, or optionally the hinge-Fc domain, may be engineered in to a polypeptide of the invention in any position relative to other domains or portions of said polypeptide chain. In certain embodiments, a polypeptide chain of the invention comprises a hinge domain, which hinge domain is at the C-terminus of the polypeptide chain, wherein said polypeptide chain does not comprise an Fc domain. In yet other embodiments, a polypeptide chain of the invention comprises a hinge-Fc domain, which hinge-Fc domain is at the C-terminus of the polypeptide chain. In further embodiments, a polypeptide chain of the invention comprises a hinge-Fc domain, which hinge-Fc domain is at the N-terminus of the polypeptide chain. [0099] As discussed above, the invention encompasses multimers of polypeptide chains, each of which polypeptide chains comprise a VH and VL domain. In certain aspects, the polypeptide chains in said multimers further comprise an Fc domain. Dimerization of the Fc domains leads to formation of a diabody molecule that exhibits irnmunoglobulin-like functionality, i.e., Fc mediated function (e.g., Fc-FcyR interaction, complement binding, etc.). In certain embodiments, the VL and VH domains comprising each polypeptide chain have the same specificity, and said diabody molecule is bivalent and monospecific. In other embodiments, the VL and VH domains comprising each polypeptide chain have differing specificity and the diabody is bivalent and bispecific. [00100] In yet other embodiments, diabody molecules of the invention encompass tetramers of polypeptide chains, each of which polypeptide chain comprises a VH and VL domain. In certain embodiments, two polypeptide chains of the tetramer further comprise an Fc domain. The tetramer is therefore comprised of two 'heavier' polypeptide chains, each comprising a VL, VH and Fc domain, and two 'lighter' polypeptide chains, comprising a VL and VH domain. Interaction of a heavier and lighter chain into a bivalent monomer coupled with dimerization of said monomers via the Fc domains of the heavier chains will lead to formation of a tetravalent immunoglobulin-like molecule (exemplified in Example 6.2 and Example 6.3). In certain aspects the monomers are the same, and the tetravalent diabody molecule is monospecific or bispecific. In other aspects the monomers are different, and the tetra valent molecule is bispecific or tetraspecific. [00101] Formation of a tetraspecific diabody molecule as described supra requires the interaction of four differing polypeptide chains. Such interactions are difficult to achieve with efficiency within a single cell recombinant production system, due to the many variants of potential chain mispairings. One solution to increase the probability of mispairings, is to engineer "knobs-into-holes" type mutations into the desired polypeptide chain pairs. Such mutations favor heterodimerization over homodimerization. For example, with respect to Fc-Fc-interactions, an amino acid substitution (preferably a substitution with an amino acid comprising a bulky side group forming a 'knob', e.g., tryptophan) can be introduced into the CH2 or CHS domain such that steric interference will prevent interaction with a similarly mutated domain and will obligate the mutated domain to pair with a domain into which a complementary, or accommodating mutation has been engineered, i.e., 'the hole' (e.g., a substitution with glycine). Such sets of mutations can be engineered into any pair of polypeptides comprising the diabody molecule, and further, engineered into any portion of the polypeptides chains of said pair. Methods of protein engineering to favor heterodimerization over homodimerization are well known in the art, in particular with respect to the engineering of immunoglobulin-like molecules, and are encompassed herein (see e.g., Ridgway et al., 1996, Protein Engr. 9:617-621, Atwell et al., 1997, J. Mol. Biol. 270: 26-35, and Xie et al., 2005, J. Immunol. Methods 296:95-101; each of which is hereby incorporated herein by reference in its entirety). [00102] The invention also encompasses diabody molecules comprising variant Fc or variant hinge-Fc domains (or portion thereof), which variant Fc domain comprises at least one amino acid modification (e.g. substitution, insertion deletion) relative to a comparable wild-type Fc domain or hinge-Fc domain (or portion thereof). Molecules comprising variant Fc domains or hinge-Fc domains (or portion thereof) (e.g., antibodies) normally have altered phenotypes relative to molecules comprising wild-type Fc domains or hinge-Fc domains or portions thereof. The variant phenotype may be expressed as altered serum half-life, altered stability, altered susceptibility to cellular enzymes or altered effector function as assayed in an NK dependent or macrophage dependent assay. Fc domain variants identified as altering effector function are disclosed in International Application W004/063351, U.S. Patent Application Publications 2005/0037000 and 2005/0064514, U.S. Provisional Applications 60/626,510, filed November 10, 2004, 60/636,663, filed December 15,2004, and 60/781,564, filed March 10, 2006, and U.S. Patent Applications 11/271,140, filed November 10,2005, and 11/305,787, filed December 15,2005, concurrent applications of the Inventors, each of which is incorporated by reference in its entirety. [00103] The bispecific diabodies of the invention can simultaneously bind two separate and distinct epitopes. In certain embodiments the epitopes are from the same antigen. In other embodiments, the epitopes are from different antigens. In preferred embodiments, at least one epitope binding site is specific for a determinant expressed on an immune effector cell (e.g. CDS, CD 16, CD32, CD64, etc.) which are expressed on T lymphocytes, natural killer (NK) cells or other mononuclear cells. In one embodiment, the diabody molecule binds to the effector cell determinant and also activates said effector cell. In this regard, diabody molecules of the invention may exhibit Ig-like functionality independent of whether they further comprise an Fc domain (e.g., as assayed in any effector function assay known in the art or exemplified herein (e.g., ADCC assay). In certain embodiments the bispecific diabody of the invention binds both a cancer antigen on a tumor cell and an effector cell determinant while activating said cell. In alternative embodiments, the bispecific diabody or diabody molecule of the invention may inhibit activation of a target, e.g., effector, cell by simultaneously binding, and thus linking, an activating and inhibitory receptor on the same cell (e.g., bind both CD32A and CD32B, BCR and CD32B, or IgERI and CD32B) as described supra (see, Background Section). In a further aspect of this embodiment, the bispecific diabody may exhibit anti-viral properties by simultaneously binding two neutralizing epitopes on a virus (e.g., RSV epitopes; WNV epitopes such as E16andE53). [00104] In certain embodiments, bispecific diabody molecules of the invention offer unique opportunities to target specific cell types. For example, the bispecific diabody or diabody molecule can be engineered to comprise a combination of epitope binding sites that recognize a set of antigens unique to a target cell or tissue type. Additionally, where either or both of the individual antigens is/are fairly common separately in other tissue and/or cell types, low affinity biding domains can be used to construct the diabody or diabody molecule. Such low affinity binding domains will be unable to bind to the individual epitope or antigen with sufficient avidity for therapeutic purposes. However, where both epitopes or antigens are present on a single target cell or tissue, the avidity of the diabody or diabody molecule for the cell or tissue, relative to a cell or tissue expressing only one of the antigens, will be increased such that said cell or tissue can be effectively targeted by the invention. Such a bispecific molecule can exhibit enhanced binding to one or both of its target antigens on cells expressing both of said antigens relative to a monospecific diabody or an antibody with a specificity to only one of the antigens. [00105] Preferably, the binding properties of the diabodies of the invention are characterized by in vitro functional assays for determining binding activity and/or one or more FcyR mediator effector cell functions (mediated via Fc-FcyR interactions or by the immunospecific binding of a diabody molecule to an FcyR) (See Section 5.4.2 and 5.4.3). The affinities and binding properties of the molecules, e.g., diabodies, of the invention for an FcyR can be determined using in vitro assays (biochemical or immunological based assays) known in the art for determining binding domain-antigen or Fc-FcyR interactions, i.e., specific binding of an antigen to a binding domain or specific binding of an Fc region to an FcyR, respectively, including but not limited to ELISA assay, surface plasmon resonance assay, immunoprecipitation assays (See Section 5.4.2). In most preferred embodiments, the molecules of the invention have similar binding properties in in vivo models (such as those described and disclosed herein) as those in in vitro based assays. However, the present invention does not exclude molecules of the invention that do not exhibit the desired phenotype in in vitro based assays but do exhibit the desired phenotype in vivo. [00106] hi some embodiments, molecules of the invention are engineered to comprise an altered glycosylation pattern or an altered glycoform relative to the comparable portion of the template molecule. Engineered glycoforms may be useful for a variety of purposes, including, but not limited to, enhancing effector function. Engineered glycoforms may be generated by any method known to one skilled in the art, for example by using engineered or variant expression strains, by co-expression with one or more enzymes, for example, DI N-acetylglucosaminyltransferase III (GnTIl 1), by expressing a diabody of the invention in various organisms or cell lines from various organisms, or by modifying carbohydrate(s) after the diabody has been expressed and purified. Methods for generating engineered glycoforms are known in the art, and include but are not limited to those described in Umana et al, 1999, Nat. Biotechnol 17:176-180; Davies etal, 2001 Biotechnol Bioeng 74:288-294; Shields et al, 2002, J Biol Chem 277:26733-26740; Shinkawa et al., 2003, J Biol Chem 278:3466-3473) US 6,602,684; USSN 10/277,370; USSN 10/113,929; PCT WO 00/61739A1; PCT WO 01/292246A1; PCT WO 02/311140A1; PCT WO 02/30954A1; Potillegent™ technology (Biowa, Inc. Princeton, NJ); GlycoMAb™ glycosylation engineering technology (GLYCART biotechnology AG, Zurich, Switzerland); each of which is incorporated herein by reference in its entirety. See, e.g., WO 00061739; EA01229125; US 20030115614; Okazald et al, 2004, JMB, 336: 1239-49 each of which is incorporated herein by reference in its entirety. [00107] The invention further encompasses incorporation of unnatural amino acids to generate the diabodies of the invention. Such methods are known to those skilled in the art such as those using the natural biosynthetic machinery to allow incorporation of unnatural amino acids into proteins, see, e.g., Wang et al, 2002 Chem. Comm, 1: 1-11; Wang et al, 2001, Science, 292: 498-500; van Hest et al, 2001. Chem. Comm. 19: 1897-1904, each of which is incorporated herein by reference in its entirety. Alternative strategies focus on the enzymes responsible for the biosynthesis of amino acyl-tRNA, see, e.g., Tang et al., 2001, J. Am. Chem. 123(44): 110S9-11090; Kiick et al., 2001, FEES Lett 505(3): 465; each of which is incorporated herein by reference in its entirety. [00108] In some embodiments, the invention encompasses methods of modifying a VL.VH or Fc domain of a molecule of the invention by adding or deleting a glycosylation site. Methods for modifying the carbohydrate of proteins are well known in the art and encompassed within the invention, see, e.g., U.S. Patent No. 6,218,149; EP 0 359 096 Bl; U.S. Publication No. US 2002/0028486; WO 03/035835; U.S. Publication No. 2003/0115614; U.S. Patent No. 6,218,149; U.S. Patent No. 6,472,511; all of which arc incorporated herein by reference in their entirety. 5.1 DIABODY BINDING DOMAINS [00109] The diabodies of the present invention comprise antigen binding domains generally derived from immunoglobulins or antibodies. The antibodies from which the binding domains used hi the methods of the invention are derived may be from any animal origin including birds and mammals (e.g., human, non-human primate, murine, donkey, sheep, rabbit, goat, guinea pig, camel, horse, or chicken). Preferably, the antibodies are human or humanized monoclonal antibodies. As used herein, "human" antibodies include antibodies having the amino acid sequence of a human immunoglobulin and include antibodies isolated from human immunoglobulin libraries or libraries of synthetic human irnmunoglobulin coding sequences or from mice that express antibodies from human genes. {00110] The invention contemplates the use of any antibodies known in the art for the treatment and/or prevention of cancer, autoimmune disease, inflammatory disease or infectious disease as source of binding domains for the diabodies of the invention. Non-limiting examples of known cancer antibodies are provided in section 5.7.1 as well as other antibodies specific for the listed target antigens and antibodies against the cancer antigens listed hi section 5.6.1; nonlimiting' examples of known antibodies for the treatment and/or prevention of autoimmune disease and inflammatory disease are provided in section 5.7.2. as well as antibodies against the listed target antigens and antibodies against the antigens listed in section 5.6.2; in other embodiments antibodies against epitopes associated with infectious diseases as listed in Section 5.6.3 can be used. In certain embodiments, the antibodies comprise a variant Fc region comprising one or more amino acid modifications, which have been identified by the methods of the invention to have a conferred effector function and/or enhanced affinity for FcyRIIB and a decreased affinity for FcyRIHA relative to a comparable molecule comprising a wild type Fc region, A non-limiting example of the antibodies that are used for the treatment or prevention of inflammatory disorders which can be engineered according to the invention is presented in Table 9, and a non-limiting example of the antibodies mat are used for the treatment or prevention of autoimmune disorder is presented in Table 10. [00111] For some uses, including in vivo use of antibodies in humans and in vitro detection assays, it may be preferable to use diabodies with variable domains derived from human, chimeric or humanized antibodies. Variable domains from completely human antibodies are particularly desirable for therapeutic treatment of human subjects. Human antibodies can be made by a variety of methods known in the art including phage display methods described above using antibody libraries derived from human immunoglobulin sequences. See also U.S. Patent Nos. 4,444,887 and 4,716,111; and International Publication Nos. WO 98/46645, WO 98/50433, WO 98/24893, WO 98/16654, WO 96/34096, WO 96/33735, and WO 91/10741; each of which is incorporated herein by reference in its entirety. [00112] A humanized antibody is an antibody, a variant or a fragment thereof which is capable of binding to a predetermined antigen and which comprises a framework region having substantially the amino acid sequence of a human immunoglobulin and a CDR having substantially the amino acid sequence of a non-human immunoglobulin. A humanized antibody may comprise substantially all of at least one, and typically two, variable domains in which all or substantially all of the CDR regions correspond to those of a non- human immunoglobulin (i.e., donor antibody) and all or substantially all of the framework regions are those of a human immunoglobulin consensus sequence. [00113] The framework and CDR regions of a humanized antibody need not correspond precisely to the parental sequences, e.g., the donor CDR or the consensus framework may be mutagenized by substitution, insertion or deletion of at least one residue so that the CDR or framework residue at that site does not correspond to either the consensus or the donor antibody. Such mutations, however, are preferably not extensive. Usually, at least 75% of the humanized antibody residues will correspond to those of the parental framework region (FR) and CDR sequences, more often 90%, and most preferably greater than 95%. Humanized antibodies can be produced using variety of techniques known in the art, including but not limited to, CDR-grafting (European Patent No. EP 239,400; International Publication No. WO 91/09967; and U.S. Patent Nos. 5,225,539, 5,530,101, and 5,585,089), veneering or resurfacing (European Patent Nos. EP 592,106 and EP 519,596; Padlan, 1991, Molecular Immunology 28(4/5):4S9-498; Studoicka et al., 1994, Protein Engineering 7(6):805-814; and Roguska et al., 1994, Proc Natl Acad Sci USA 91:969-973), chain shuffling (U.S. Patent No. 5,565,332), and techniques disclosed in, e.g., U.S. Patent Nos. 6,407,213, 5,766,886, 5,585,089, International Publication No. WO 9317105, Tan etal, 2002, J. Immunol. 169:1119-25, Caldas et al., 2000, Protein Eng. 13:353-60, Morea et al, 2000, Methods 20:267-79, Baca et al, 1997, J. Biol. Chern. 272:10678-84, Roguska et al, 1996, Protein Eng. 9:895-904, Couto et al, 1995, Cancer Res. 55 (23 Supp):5973s-5977s, Couto et al, 1995, Cancer Res. 55:1717-22, Sandhu, 1994, Gene 150:409-10, Pedersen et al, 1994, J. Mol. Biol. 235:959-73, Jones et al, 1986, Nature 321:522-525, Riechmann et al, 1988,Nature 332:323, and Presto, 1992, Curr. Op. Struct. Biol. 2:593-596. Often, framework residues in the framework regions will be substituted with the corresponding residue from the CDR donor antibody to alter, preferably improve, antigen binding. These framework substitutions are identified by methods well known in the art, e.g., by modeling of the interactions of the CDR and framework residues to identify framework residues important for antigen binding and sequence comparison to identify unusual framework residues at particular positions. (See, e.g.,- Queen et al, U.S. Patent No. 5,585,089; U.S. Publication Nos. 2004/0049014 and 2003/0229208; U.S. Patent Nos. 6,350,861; 6,180,370; 5,693,762; 5,693,761; 5,585,089; and 5,530,101 and Riechmann et al, 1988, Nature 332:323, all of which are incorporated herein by reference in their entireties.). [00114] In a most preferred embodiment, the humanized binding domain specifically binds to the same epitope as the donor murine antibody. It will be appreciated by one skilled in the art that the invention encompasses CDR grafting of antibodies in general. Thus, the donor and acceptor antibodies may be derived from animals of the same species and even same antibody class or sub-class. More usually, however, the donor and acceptor antibodies are derived from animals of different species. Typically the donor antibody is a non-human antibody, such as a rodent MAb, and the acceptor antibody is a human antibody. [00115] In some embodiments, at least one CDR from the donor antibody is grafted onto the human antibody. In other embodiments, at least two and preferably all three CDRs of each of the heavy and/or light chain variable regions are grafted onto the human antibody. The CDRs may comprise the Kabat CDRs, the structural loop CDRs or a combination thereof. In some embodiments, the invention encompasses a humanized FcyRIIB antibody comprising at least one CDR grafted heavy chain and at least one CDR-grafted light chain. [00116] The diabodies used in the methods of the invention include derivatives that are modified, i.e., by the covalent attachment of any type of molecule to the diabody. For example, but not by way of limitation, the diabody derivatives include diabodies that have been modified, e.g., by glycosylation, acetylation, pegylation, phosphorylation, amidation, derivatization by known protecting/blocking groups, proteolytic cleavage, linkage to a cellular ligand or other protein, etc. Any of numerous chemical modifications may be carried out by known techniques, including, but not limited to, specific chemical cleavage, acetylation, formylation, metabolic synthesis of tunicamycin, etc. Additionally, the derivative may contain one or more non-classical amino acids. [00117] A chimeric antibody is a molecule in which different portions of the antibody are derived from different immunoglobulin molecules such as antibodies having a variable region derived from a non-human antibody and a human immunoglobulin constant region. Methods for producing chimeric antibodies are known hi the art. See e.g., Morrison, 1985, Science 229:1202; Oi et al, 1986, BioTechniques 4:214; Gillies et al, 1989, J. Immunol. Methods 125:191-202; and U.S. PatentNos. 6,311,415, 5,807,715,4,816,567, and 4,816,397, which are incorporated herein by reference in their entirety. [00118] Often, framework residues in the framework regions will be substituted with the corresponding residue from the CDR donor antibody to alter, preferably improve, antigen binding. These framework substitutions are identified by methods well known m the art, e.g., by modeling of the interactions of the CDR and framework residues to identify framework residues important for antigen binding and sequence comparison to identify unusual framework residues at particular positions. (See, e.g., U.S. Patent No. 5,585,089; and Riechmann et al, 1988, Nature 332:323, which are incorporated herein by reference in their entireties.) [00119] Monoclonal antibodies from which binding domains of the diabodies of the invention can be prepared using a wide variety of techniques known in the art including the use of hybridoma, recombinant, and phage display technologies, or a combination thereof. For example, monoclonal antibodies can be produced using hybridoma techniques including those known in the art and taught, for example, in Harlow et al, Antibodies: A Laboratory Manual, (Cold Spring Harbor Laboratory Press, 2nd ed. 1988); Hammerling, et al, in: Monoclonal Antibodies and T-Cell Hybridomas, pp. 563-681 (Elsevier, N.Y., 1981) (both of which are incorporated by reference in their entireties). The term "monoclonal antibody" as used herein is not limited to antibodies produced through hybridoma technology. The term "monoclonal antibody" refers to an antibody that is derived from a single clone, including any eukaryotic, prokaryotic, or phage clone, and not the method by which it is produced. [00120] Methods for producing and screening for specific antibodies using hybridoma technology are routine and well known in the art. In a non-limiting example, mice can be immunized with an antigen of interest or a cell expressing such an antigen. Once an immune response is detected, e.g., antibodies specific for the antigen are detected hi the mouse serum, the mouse spleen is harvested and splenocytes isolated. The splenocytes are then fused by well known techniques to any suitable myeloma cells. Hybridomas are selected and cloned by limiting dilution. The hybridoma clones are then assayed by methods known in the art for cells that secrete antibodies capable of binding the antigen. Ascites fluid, which generally contains high levels of antibodies, can be generated by inoculating mice intraperitoneally with positive hybridoma clones. Antigens of interest include, but are not limited to, antigens associated with the cancers provided in section 5.8.1, antigens associated with the autoimmune diseases and inflammatory diseases provided in section 5.8.2, antigens associated with the infectious diseases provided in section 5.8.3, and the toxins provided in section 5.8.4, [00121] Antibodies can also be generated using various phage display methods known hi the art. In phage display methods, functional antibody domains are displayed on • the surface of phage particles which carry the polynucleotide sequences encoding them. In a particular embodiment, such phage can be utilized to display antigen binding domains, such as Fab and Fv or disulfide-bond stabilized Fv, expressed from a repertoire or combinatorial antibody library (e.g., human or murine). Phage expressing an antigen binding domain that binds the antigen of interest can be selected or identified with antigen, e.g., using labeled antigen or antigen bound or captured to a solid surface or bead. Phage used in these methods are typically filamentous phage, including fd and Ml3. The antigen binding domains are expressed as a recombinantly fused protein to either the phage gene III or gene VDI protein. Examples of phage display methods that can be used to make the immunoglobulins, or fragments thereof, of the present invention include those disclosed in Brinkman et al, J. Immunol. Methods, 182:41-50,1995; Ames et al, J. Immunol. Methods, 184:177-186,1995; Kettleborough et al, Eur. J. Immunol., 24:952-958, 1994; Persic et al, Gene, 187:9-18, 1997; Burton et al, Advances in Immunology, 57:191-280,1994; PCT Application No. PCT/GB91/01134; PCT Publications WO 90/02809; WO 91/10737; WO 92/01047; WO 92/18619; WO 93/11236; WO 95/15982; WO 95/20401; and U.S. PatentNos. 5,698,426; 5,223,409; 5,403,484; 5,580,717; 5,427,908; 5,750,753; 5,821,047; 5,571,698; 5,427,908; 5,516,637; 5,780,225; 5,658,727; 5,733,743 and 5,969,108; each of which is incorporated herein by reference in its entirety. [00122] Phage display technology can be used to increase the affinity of an antibody for its antigen. This technique would be useful in obtaining high affinity antibodies. The technology, referred to as affinity maturation, employs mutagenesis or CDR walking and re- selection using the cognate antigen to identify antibodies that bind with higher affinity to the antigen when compared with the initial or parental antibody (See, e.g.,Glaser et al, 1992, J. Immunology 149:3903). Mutagenizing entire codons rather than single nucleotides results in a semi-randomized repertoire of amino acid mutations. Libraries can be constructed consisting of a pool of variant clones each of which differs by a single amino acid alteration in a single CDR and which contain variants representing each possible amino acid substitution for each CDR residue. Mutants with increased binding affinity for the antigen can be screened by contacting the immobilized mutants with labeled antigen. Any screening method known in the art can be used to identify mutant antibodies, with increased avidity to the antigen (e.g., ELISA) (See Wu et al., 1998, Proc Natl. Acad Sci. USA 95:6037; Yelton et al., 1995, J. Immunology 155:1994). CDR walking which randomizes the light chain is also possible (See Schier et al., 1996, J. Mol. Bio. 263:551). [00123] The present invention also encompasses the use of binding domains comprising the amino acid sequence of any of the binding domains described herein or known in the art with mutations (e.g., one or more amino acid substitutions) in the framework or CDR regions. Preferably, mutations in these binding domains maintain or enhance the avidity and/or affinity of the binding domains for FcyRIIB to which they immunospecifically bind, Standard techniques known to those skilled in the art (e.g., immunoassays) can be used to assay the affinity of an antibody for a particular antigen. [00124] Standard techniques known to those skilled in the art can be used to introduce mutations in the nucleotide sequence encoding an antibody, or fragment thereof, including, e.g., site-directed mutagenesis and PCR-mediated mutagenesis, which results in amino acid substitutions. Preferably, the derivatives include less than 15 amino acid substitutions, less than 10 amino acid substitutions, less than 5 amino acid substitutions, less than 4 amino acid substitutions, less than 3 amino acid substitutions, or less than 2 amino acid substitutions relative to the original antibody or fragment thereof. In a preferred embodiment, the derivatives have conservative amino acid substitutions made at one or more predicted non-essential amino acid residues. 5.1.1 DIABODIES COMPRISING EFTIOPE BINDING SITES WHICH IMMUNOSPECIFICALLY BIND FcyRIIB [00125] In a particular embodiment, at least one of the binding domains of the diabodies of the invention agonizes at least one activity of FcyRIIB. In one embodiment of the invention, said activity is inhibition of B cell receptor-mediated signaling. In another embodiment, the binding domain inhibits activation of B cells, B cell proliferation, antibody production, intracellular calcium influx of B cells, cell cycle progression, or activity of one or more downstream signaling molecules in the FcyRIIB signal transduction pathway. In yet another embodiment, the binding domain enhances phosphorylation of FcyRIIB or SHIP recruitment. In a further embodiment of the invention, the binding domain inhibits MAP kinase activity or Akt recruitment in the B cell receptor-mediated signaling pathway. In another embodiment, the binding domain agonizes FcyRIIB-mediated inhibition of FceRI signaling. In a particular embodiment, said binding domain inhibits FceRI-induced mast cell activation, calcium mobilization, degranulation, cytokine production, or serotonin release. In another embodiment, the binding domains of the invention stimulate phosphorylation of FcyRIIB, stimulate recruitment of SHIP, stimulate SHIP phosphorylation and its association with She, or inhibit activation of MAP kinase family members (e.g., Erkl, Erk2, JNK, p38, etc.). In yet another embodiment, the binding domains of the invention enhance tyrosine phosphorylation of p62dok and its association with SHIP and rasGAP. In another embodiment, the binding domains of the invention inhibit FcyR-mediated phagocytosis in monocytes or macrophages. [00126] In another embodiment, the binding domains antagonize at least one activity of FcyRIIB. In one embodiment, said activity is activation of B cell receptor-mediated signaling, In a particular embodiment, the binding domains enhance B cell activity, B cell proliferation, antibody production, intracellular calcium influx, or activity of one or more downstream signaling molecules in the FcyRIIB signal transduction pathway. In yet another particular embodiment, the binding domains decrease phosphorylation of FcyRIIB or SHIP recruitment. In a further embodiment of the invention, the binding domains enhance MAP kinase activity or Akt recruitment in the B cell receptor mediated signaling pathway. In another embodiment, the binding domains antagonize FcyRIIB-rnediated inhibition of FceRI signaling. In a particular embodiment, the binding domains enhance FceRI-induced mast cell activation, calcium mobilization, degranulation, cytokine production, or serotonin release. In another embodiment, the binding domains inhibit phosphorylation of FcyRIIB, inhibit recruitment of SHIP, inhibit SHIP phosphorylation and its association with She, enhance activation of MAP kinase family members (e.g., Erkl, Erk2, JNK, p38, etc.). In yet another embodiment, the binding domains inhibit tyrosine phosphorylation of p62dok and its association with SHIP and rasGAP. In another embodiment, the binding domains enhance FcyR-mediated phagocytosis in monocytes or macrophages. In another embodiment, the binding domains prevent phagocytosis, clearance of opsonized particles by splenic macrophages. [00127] In other embodiments, at least one of the binding domains can be used to target the diabodies of the invention to cells that express FcyRIIB. [00128] In one particular embodiment, one of the binding domains is derived from a mouse monoclonal antibody produced by clone 2B6 or 3H7, having ATCC accession numbers PTA-4591 and PTA-4592, respectively. Hybridomas producing antibodies 2B6 and 3H7 have been deposited with the American Type Culture Collection (10801 University Blvd., Manassas, VA. 20110-2209) on August 13,2002 under the provisions of the Budapest Treaty on the International Recognition of the Deposit of Microorganisms for the Purposes of Patent Procedures, and assigned accession numbers PTA-4591 (for hybridoma producing 2B6) and PTA-4592 (for hybridoma producing 3H7), respectively, and are incorporated herein by reference. In a preferred embodiment, the binding domains are human or have been humanized, preferably are derived from a humanized version of the antibody produced by clone 3H7 or 2B6. [00129] The invention also encompasses diabodies with binding domains from other antibodies, that specifically bind FcyRIIB, preferably human FcyRIIB, more preferably native human FcyRIIB, that are derived from clones including but not limited to 1D5, 2E1, 2H9, 2D11, and 1F2 having ATCC Accession numbers, PTA-5958, PTA-5961, PTA-5962, PTA-5960, and PTA-5959, respectively. Hybridomas producing the above-identified clones were deposited under the provisions of the Budapest Treaty with the American Type Culture Collection (10801 University Blvd., Manassas, VA. 20110-2209) on May 7,2004, and are incorporated herein by reference. In preferred embodiments, the binding domains from the antibodies described above are humanized. [00130] In a specific embodiment, the binding domains used hi the diabodies of the present invention are from an antibody or an antigen-binding fragment thereof (e.g., comprising one or more complementarity determining regions (CDRs), preferably all 6 CDRs) of the antibody produced by clone 2B6, 3H7, IDS, 2E1, 2H9, 2D11, or 1F2. In another embodiment, the binding domain binds to the same epitope as the mouse monoclonal antibody produced from clone 2B6, 3H7, IDS, 2E1, 2H9,2D11, or 1F2, respectively and/or competes with the mouse monoclonal antibody produced from clone 2B6,3H7, IDS, 2E1,2H9, 2D11, or 1F2 as determined, e.g., in an ELISA assay or other appropriate competitive immunoassay, and also binds FcyRIIB with a greater affinity than the binding domain binds FcyRIIA. [00131] The present invention also encompasses diabodies with binding domains comprising an amino acid sequence of a variable heavy chain and/or variable light chain that is at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 99% identical to the amino acid sequence of the variable heavy chain and/or light chain of the mouse monoclonal antibody produced by clone 2B6, 3H7, 1D5} 2E1,2H9, 2D11, or 1F2. The present invention further encompasses diabodies with binding domains that specifically bind FcyRIIB with greater affinity than said antibody or fragment thereof binds FcyRIIA, and that comprise an amino acid sequence of one or more CDRs that is at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 99% identical to the amino acid sequence of one or more CDRs of the mouse monoclonal antibody produced by clone 2B6, 3H7,1D5, 2E1,2H9,2D11, or 1F2. The determination of percent identity of two amino acid sequences can be determined by any method known to one skilled in the art, including BLAST protein searches. [00132] The present invention also encompasses the use of diabodies containing binding domains that specifically bind FcyRIIB with greater affinity than binding domain binds FcyRIIA, which are encoded by a nucleotide sequence that hybridizes to the nucleotide sequence of the mouse monoclonal antibody produced by clone 2B6, 3H7, 1D5, 2E1,2H9, 2D11, or 1F2 under stringent conditions, hi a preferred embodiment, the binding domain specifically binds FcyRIIB with greater affinity than FcyRIIA, and comprises a variable light chain and/or variable heavy chain encoded by a nucleotide sequence that hybridizes under stringent conditions to the nucleotide sequence of the variable light chain and/or variable heavy chain of the mouse monoclonal antibody produced by clone 2B6, 3H7,1D5,2E1,2H9, 2D11, or 1F2 under stringent conditions. In another preferred embodiment, the binding domains specifically bind FcyRIIB with greater affinity than FcyRIIA, and comprise one or more CDRs encoded by a nucleotide sequence that hybridizes under stringent conditions to the nucleotide sequence of one or more CDRs of the mouse monoclonal antibody produced by clone 2B6, 3H7, 1D5,2E1, 2H9, 2D11, or 1F2. Stringent hybridization conditions include, but are not limited to, hybridization to filter-bound DNA in 6X sodium chloride/sodium citrate (SSC) at about 45 °C followed by one or more washes in 0.2X SSC/0.1% SDS at about 50-65°C, highly stringent conditions such as hybridization to filter-bound DNA in 6X SSC at about 45°C followed by one or more washes in 0.1X SSC/0.2% SDS at about 60°C, or any other stringent hybridization conditions known to those skilled in the art (see, for example, Ausubel, F.M. et al, eds. 1989 Current Protocols in Molecular Biology, vol. 1, Green Publishing Associates, Inc. and John Wiley and Sons, Inc., NY at pages 6.3.1 to 6.3.6 and 2.10.3, incorporated herein by reference). [00133] The present invention also encompasses the use of binding domains comprising the amino acid sequence of any of the binding domains described above with mutations (e.g., one or more amino acid substitutions) in the framework or CDR regions. Preferably, mutations in these binding domains maintain or enhance the avidity and/or affinity of the binding domains for FcyRIIB to which they immunospecifically bind. Standard techniques known to those skilled in the art (e.g., immunoassays) can be used to assay the affinity of an antibody for a particular antigen. [00134] Standard techniques known to those skilled in the art can be used to introduce mutations in the nucleotide sequence encoding an antibody, or fragment thereof, including, e.g., site-directed mutagenesis and PCR-mediated mutagenesis, which results in amino acid substitutions. Preferably, the derivatives include less than 15 amino acid substitutions, less than 10 amino acid substitutions, less than 5 amino acid substitutions, less than 4 amino acid substitutions, less than 3 amino acid substitutions, or less than 2 ammo acid substitutions relative to the original antibody or fragment thereof. In a preferred embodiment, the derivatives have conservative amino acid substitutions made at one or more predicted non-essential amino acid residues. ! [00135] In preferred embodiments, the binding domains are derived from humanized antibodies. A humanized FcyRJIB specific antibody may comprise substantially all of at least one, and typically two, variable domains in which all or substantially all of the CDR regions correspond to those of a non-human immunoglobulin (i.e., donor antibody) and all or substantially all of the framework regions are those of a human immunoglobulin consensus sequence. [00136] The diabodies of present invention comprise humanized variable domains specific for FcyRIIB in which one or more regions of one or more CDRs of the heavy and/or light chain variable regions of a human antibody (the recipient antibody) have been substituted by analogous parts of one or more CDRs of a donor monoclonal antibody which specifically binds FcyRIIB, with a greater affinity than FcyRIIA, e.g., a monoclonal antibody produced by clone 2B6, 3H7,1D5,2E1,2H9,2D11, or 1F2. In other embodiments, the humanized antibodies bind to the same epitope as 2B6, 3H7,1D5,2E1, 2H9,2D11, or 1F2, respectively. [00137] In a preferred embodiment, the CDR regions of the humanized FcyRIIB binding domain are derived from a murine antibody specific for FcyRIIB. In some embodiments, the humanized antibodies described herein comprise alterations, including but not limited to amino acid deletions, insertions, modifications, of the acceptor antibody, i.e., human, heavy and/or light chain variable domain framework regions that are necessary for retaining binding specificity of the donor monoclonal antibody. In some embodiments, the framework regions of the humanized antibodies described herein does not necessarily consist of the precise amino acid sequence of the framework region of a natural occurring human antibody variable region, but contains various alterations, including but not limited to amino acid deletions, insertions, modifications that alter the property of the humanized antibody, for example, improve the binding properties of a humanized antibody region that is specific for the same target as the murine FcyRIIB specific antibody. In most preferred embodiments, a minimal number of alterations are made to the framework region in order to avoid large-scale introductions of non-human framework residues and to ensure minimal immunogenicity of the humanized antibody in humans. The donor monoclonal antibody is preferably a monoclonal antibody produced by clones 2B6, 3H7,1D5, 2E1,2H9,2D11, or 1F2. [00138] In a specific embodiment, the binding domain encompasses variable domains of a CDR-grafted antibody which specifically binds FcyRIIB with a greater affinity than said antibody binds FcyRIIA, wherein the CDR-grafted antibody comprises a heavy chain variable region domain comprising framework residues of the recipient antibody and residues from the donor monoclonal antibody, which specifically binds FcyRIIB with a greater affinity than said antibody binds FcyRIIA, e.g., monoclonal antibody produced from clones 2B6,3H7, IDS, 2E1,2H9,2D11, or 1F2. In another specific embodiment, the diabodies of the invention comprise variable domains from a CDR-grafted antibody which specifically binds FcyRIIB with a greater affinity than said antibody binds FcyRUA, wherein the CDR-grafted antibody comprises a light chain variable region domain comprising framework residues of the recipient antibody and residues from the donor monoclonal antibody, which specifically binds FcyRIIB with a greater affinity than said antibody binds FcyRIIA, e.g., monoclonal antibody produced from clones 2B6, 3H7, IDS, 2El,2H9,2Dll,orlF2. [00139] The humanized anti- FcyRIIB variable domains used hi the invention may have a heavy chain variable region comprising the amino acid sequence of CDR1 (SEQ ID N0:24 or SEQ ID N0:25) and/or CDR2 (SEQ ID N0:26 or SEQ ID N0:27) and/or CDR3 (SEQ ID N0:28 or SEQ ID N0:29) and/or a light chain variable region comprising the amino acid sequence of CDR1 (SEQ ID NO:32 or SEQ ID N0:33) and/or a CDR2 (SEQ ID N0:34, SEQ ID N0:35, SEQ ID N0:36, or SEQ ID N0:37) and/or CDR3 (SEQ ID N0:38 orSEQIDNO:39). [00140] In one specific embodiment, the diabody comprises variable domains from a humanized 2B6 antibody, wherein the VH region consists of the FR segments from the human germline VH segment VH1-18 (Matsuda et al, 1998, J. Exp. Med. 188:2151062) and JH6 (Ravetch et al., 1981, Cell 27(3 Pt. 2): 583-91), and one or more CDR regions of the 2B6 VH, having the amino acid sequence of SED ID NO:24, SEQ ID N0:26, or SEQ ID NO:28. In one embodiment, the 2B6 VH has the amino acid sequence of SEQ ID NO:40. In another embodiment the 2B6 VH domain has the amino acid sequence of Hu2B6VH, SEQ ID N0:87, and can be encoded by the nucleotide sequence of SEQ ID NO:88. In another specific embodiment, the diabody further comprises a VL region, which consists of the FR segments of the human germline VL segment VK-A26 (Lautner-Rieske et al, 1992, Eur. J. Immunol. 22:1023-1029) and JK4 (Hieter et al., 1982, J. Biol. Chem. 257:1516-22), and one or more CDRregions of 2B6VL, having the amino acid sequence of SEQ ID N0:32, SEQ ID N0:34, SEQ ID NO:35, SEQ ID NO:36, and SEQ ID N0:38. In one embodiment, the 2B6 VL has the amino acid sequence of SEQ ID NO:41; SEQ ID N0:42, or SEQ ID NO:43. In a specific embodiment, the 2B6 VL has the amino acid sequence of Hu2B6VL, SEQ ID N0:89, and can be encoded by the nucleotide sequence provided in SEQ ID N0:90. [00141] In another specific embodiment, the diabody has variable domains from a humanized 3H7 antibody, wherein the VH region consists of the FR segments from a human germline VH segment and the CDR regions of the 3H7 VH, having the amino acid sequence of SED ID NO. 37. hi another specific embodiment, the humanized 3H7 antibody further comprises a VL regions, which consists of the FR segments of a human germline VL segment and the CDR regions of 3H7VL, having the amino acid sequence of SEQIDNO:44. [00142] In particular, binding domains immunospecifically bind to extracellular domains of native human FcyRIIB, and comprise (or alternatively, consist of) CDR sequences of 2B6, 3H7, IDS, 2E1, 2H9, 2D11, or 1F2, in any of the following combinations: a VH CDR1 and a VL CDR1; a VH CDR1 and a VL CDR2; a VH CDR1 and a VL CDR3; a VH CDR2 and a VL CDRl; VH CDR2 and VL CDR2; a VH CDR2 and a VL CDR3; a VH CDR3 and a VH CDRl; a VH CDR3 and a VL CDRl; a VH CDR3 and aVL CDR3; a VHl CDRl, a VH CDR2 and a VL CDRl; a VH CDRl, a VH CDR2 and a VL CDR2; a VH CDRl, a VH CDR2 and a VL CDR3; a VH CDR2, a VH CDRS and a VL CDRl, a VH CDR2, a VH CDR3 and a VL CDR2; a VH CDR2, a VH CDR2 and a VL CDR3; a VH CDRl, a VL CDRl and a VL CDR2; a VH CDRl, a VL CDRl and a VL CDR3; a VH CDR2, a VL CDRl and a VL CDR2; a VH CDR2, a VL CDRl and a VL CDR3; a VH CDR3, a VL CDRl and a VL CDR2; a VH CDR3, a VL CDRl and a VL CDR3; a VH CDRl, a VH CDR2, a VH CDR3 and a VL CDRl; a VH CDRl, a VH CDR2, a VH CDR3 and a VL CDR2; a VH CDRl, a VH CDR2, a VH CDR3 and a VL CDR3; a VH CDRl, a VH CDR2, a VL CDRl and a VL CDR2; a VH CDRl, a VH CDR2, a VL CDRl and a VL CDR3; a VH CDRl, a VH CDR3, a VL CDRl and a VL CDR2; a VH CDRl, a VH CDR3, a VL CDRl and a VL CDR3; a VH CDR2, a VH CDR3, a VL CDRl and a VL CDR2; a VH CDR2, a VH CDR3, a VL CDRl and a VL CDR3; a VH CDR2, a VH CDR3, a VL CDR2 and a VL CDR3; a VH CDRl, a VH CDR2, a VH CDR3, a VL CDRl and a VL CDR2; a VH CDRl, a VH CDR2, a VH CDR3, a VL CDRl and a VL CDR3; aVHCDRl, a VH CDR2, a VL CDRl, a VL CDR2, and a VL CDR3; a VH CDRl, a VH CDR3, a VL CDRl, a VL CDR2, and a VL CDR3; a VH CDR2, a VH CDR3, a VL CDRl, a VL CDR2, and a VL CDR3; or any combination thereof of the VH CDRs and VL CDRs disclosed herein. [00143] Antibodies for deriving binding domains to be included in the diabodies of the invention may be further characterized by epitope mapping, so that antibodies may be selected that have the greatest specificity for FcyRIIB compared to FcyRIIA. Epitope mapping methods of antibodies are well known in the art and encompassed within the methods of the invention. In certain embodiments fusion proteins comprising one or more regions of FcyRIIB may be used in mapping the epitope of an antibody of the invention. In a specific embodiment, the fusion protein contains the amino acid sequence of a region of an FcyRIIB fused to the Fc portion of human IgG2, Each fusion protein may further comprise amino acid substitutions and/or replacements of certain regions of the receptor with the corresponding region from a homolog receptor, e.g., FcyRIIA, as shown in Table 2 below. pMGX125 and pMGX132 contain the IgG binding site of the FcyRIIB receptor, the former with the C-terminus of FcyRIIB and the latter with the C-terminus of FcyRIIA and can be used to differentiate C-terminus binding. The others have FcyRIIA substitutions in the IgG binding site and either the FcyllA or FcyllB N-terminus. These molecules can help determine the part of the receptor molecule where the antibodies bind. Table 2. List of the fusion proteins that may be used to investigate the epitope of the monoclonal anti-FcyRIIB antibodies. Residues 172 to 180 belong to the IgG binding site of FcyRIIA and B. The specific amino acids from FcyRIIA sequence are in bold. (Table Removed) [00144] The fusion proteins may be used in any biochemical assay for determination of binding to an anti-FcyRIIB antibody of the invention, e.g., an ELISA. In other embodiments, further confirmation of the epitope specificity may be done by using peptides with specific residues replaced with those from the FcyRIIA sequence. [00145] The antibodies can be characterized using assays for identifying the function of the antibodies of the invention, particularly the activity to modulate Fey RUB signaling. For example, characterization assays of the invention can measure phosphorylation of tyrosine residues in the ITIM motif of FcyRIIB, or measure the inhibition of B cell receptor-generated calcium mobilization. The characterization assays of the invention can be cell-based or cell-free assays. [00146] It has been well established in the art that in mast cells coaggregation of FcyRIIB with the high affinity IgE receptor, FceRI, leads to inhibition of antigen-induced degranulation, calcium mobilization, and cytokine production (Metcalfe D.D. et al. 1997, Physiol. Rev. 77:1033; Long E.O. 1999 Annu Rev. Immunol 17: 875). The molecular details of this signaling pathway have been recently elucidated (Ott V. L., 2002, J. Immunol. 162(9):4430-9). Once coaggregated with FceRI, FcyRIIB is rapidly phosphorylated on tyrosine in its ITIM motif, and then recruits Src Homology-2 containing inositol-5-phosphatase (SHIP), an SH2 domain-containing inosital polyphosphate 5- phosphatase, which is in turn phosphorylated and associates with She and p62dok (p62dok is the prototype of a family of adaptor molecules, which includes signaling domains such as an aminoterminal pleckstrin homology domain (PH domain), a PTB domain, and a carboxy terminal region containing PXXP motifs and numerous phosphorylation sites (Carpino et a/., 1997 Cell, 88: 197; Yamanshi et at, 1997, Cell, 88:205). [00147] The anti-FcyRIIB antibodies for use in the invention may likewise be characterized for ability to modulate one or more IgE mediated responses. Preferably, cells lines co-expressing the high affinity receptor for IgE and the low affinity receptor for FcyRHB will be used in characterizing the anti-FcyRIIB antibodies hi modulating IgE mediated responses. In a specific embodiment, cells from a rat basophilic leukemia cell line (RBL-H23; Barsumian E.L. et al. 1981 Eur. J. Immunol.l 1:317, which is incorporated herein by reference hi its entirety) transfected with full length human FcyRIIB will be used. RBL-2H3 is a well characterized rat cell line that has been used extensively to study the signaling mechanisms following IgE-mediated cell activation. When expressed in RBL-2H3 cells and coaggregated with FceRI, FcyRIIB inhibits FcePJ-induced calcium mobilization, degranulation, and cytokine production (Malbec et al., 1998, J. Immunol. 160:1647; Daeron etal., 1995 J. Clin. Invest. 95:577; Ott et al, 2002 J. of Immunol. 168:4430-4439). [00148] Antibodies for use in the invention may also be characterized for inhibition of FceRI induced mast cell activation. For example, cells from a rat basophilic leukemia cell line (RBL-H23; Barsumian E.L. et al, 1981 Eur. J. Immunol. 11:317) that have been transfected with FcyRIIB are sensitized with IgE and stimulated either with F(ab')a fragments of rabbit anti-mouse IgG, to aggregate FceRI alone, or with whole rabbit anti- mouse IgG to coaggregate FcyRIIB and FcsRI. In this system, indirect modulation of down stream signaling molecules can be assayed upon addition of antibodies of the invention to the sensitized and stimulated cells. For example, tyrosine phosphorylation of FcyRIIB and recruitment and phosphorylation of SHIP, activation of MAP kinase family members, , including but not limited to Erkl, Erk2, INK, or p38; and tyrosine phosphorylation of p62dok and its association with SHIP and RasGAP can be assayed. [00149] One exemplary assay for determining the inhibition of FceRI induced rnast cell activation by the antibodies of the invention can comprise of the following: transfecting RBL-H23 cells with human FcyRIIB; sensitizing the RBL-H23 cells with IgE; stimulating RBL-H23 cells with either F(ab')2 of rabbit anti-mouse IgG (to aggregate FceRI alone and elicit FceRI-mediated signaling, as a control), or stimulating RBL-H23 cells with whole rabbit anti-mouse IgG to (to coaggregate FcyRIIB and FcsRJ, resulting in inhibition of FceRI-mediated signaling). Cells that have been stimulated with whole rabbit anti-mouse IgG antibodies can be further pre-incubated with the antibodies of the invention. Measuring FceRI-dependent activity of cells that have been pre-incubated with the antibodies of the invention and cells that have not been pre-incubated with the antibodies of the invention, and comparing levels of FceRI-dependent activity in these cells, would indicate a modulation of FceRI-dependent activity by the antibodies of the invention. [00150] The exemplary assay described above can be for example, used to identify antibodies that block ligand (IgG) binding to FcyRIIB receptor and antagonize FcyRHB-mediated inhibition of FceRI signaling by preventing coaggregating of FcyRIIB and FceRI. This assay likewise identifies antibodies that enhance coaggregation of FcyRIIB and FceRI and agonize FcyRIIB-mediated inhibition of FceRI signaling by promoting coaggregating of FcyRIIB and FceRI. [00151] In some embodiments, the anti-FcyRIIB diabodies, comprising the epitope binding domains of anti-FcyRIIB antibodies identified described herein or known in the art, of the invention are characterized for their ability to modulate an IgE mediated response by monitoring and/or measuring degranulation of mast cells or basophils, preferably hi a cell-based assay. Preferably, mast cells or basophils for use in such assays have been engineered to contain human FcyRIIB using standard recombinant methods known to one skilled in the art. In a specific embodiment the anti-FcyRIIB antibodies of the invention are characterized for their ability to modulate an IgE mediated response in a cell-based (3-hexosaminidase (enzyme contained in the granules) release assay. P-hexosaminidase release from mast cells and basophils is a primary event in acute allergic and inflammatory condition (Aketani et al., 2001 Immunol. Lett. 75: 185-9; Aketani et al., 2000 Anal. Chem. 72: 2653-8). Release of other inflammatory mediators including but not limited to serotonin and histamine may be assayed to measure an IgE mediated response in accordance with the methods of the invention. Although not intending to be bound by a particular mechanism of action, release of granules such as those containing p-hexosaminidase from mast cells and basophils is an intracellular calcium concentration dependent process that is initiated by the cross-linking of FcyRIs with multivalent antigen. [00152]' The ability to study human mast cells has been limited by the absence of suitable long term human mast cell cultures. Recently two novel stem cell factor dependent human mast cell lines, designated LAD 1 and LAD2, were established from bone marrow aspirates from a patient with mast cell sarcoma/leukemia ( Kirshenbaum et al., 2003, Leukemia research, 27:677-82, which is incorporated herein by reference in its entirety.). Both cell lines have been described to express FceRI and several human mast cell markers. LAD 1 and 2 cells can be used for assessing the effect of the antibodies of the invention on IgE mediated responses. In a specific embodiment, cell-based P-hexosaminidase release assays such as those described supra may be used hi LAD cells to determine any modulation of the IgE-mediated response by the anti-FcyRUB antibodies of the invention. In an exemplary assay, human mast cells, e.g., LAD 1, are pruned with chimeric human IgE anti-nitrophenol (NP) and challenged with BSA-NP, the polyvalent antigen, and cell degranulation is monitored by measuring the p-hexosaminidase released in the supernatant (Kirshenbaum et al, 2003, Leukemia research, 27:677-682, which is incorporated herein by reference in its entirety). [00153] In some embodiments, if human mast cells have a low expression of endogenous FcyRIIB, as determined using standard methods known hi the art, e.g., FACS staining, it may be difficult to monitor and/or detect differences in the activation of the inhibitory pathway mediated by the anti-FcyRIIB diabodies of the invention. The invention thus encompasses alternative methods, whereby the FcyRIIB expression may be upregulated using cytokines and particular growth conditions. FcyRIIB has been described to be highly up-regulated hi human monocyte cell lines, e.g., THP1 and U937, (Tridandapani et al., 2002, J. Biol. Chem., 277(7): 5082-5089) and in primary human monocytes (Pricop et al, 2001, J. of Immunol., 166: 531-537) by IL4. Differentiation of U937 cells with dibutyryl cyclic AMP has been described to increase expression of FcyRII (Cameron et al, 2002 Immunology Letters 83, 171-179). Thus the endogenous FcyRIIB expression in human mast cells for use hi the methods of the invention may be up-regulated using cytokines, e.g., IL-4, IL-13, in order to enhance sensitivity of detection. [00154] The anti-FcyRIIB diabodies can also be assayed for inhibition of B-cell receptor (BCR)-mediated signaling. BCR-mediated signaling can include at least one or more down stream biological responses, such as activation and proliferation of B cells, antibody production, etc. Coaggregation of FcyRIIB and BCR leads to inhibition of cell cycle progression and cellular survival. Further, coaggregation of FcyRIIB and BCR leads to inhibition of BCR-mcdiated signaling. [00155] Specifically, BCR-mediated signaling comprises at least one or more of the following: modulation of down stream signaling molecules (e.g., phosphorylation state of FcyRIIB, SHIP recruitment, localization of Btk and/or PLCy, MAP kinase activity, recruitment of Akt (anti-apoptotic signal), calcium mobilization, cell cycle progression, and cell proliferation. [00156] Although numerous effector functions of FcyRIIB-mediated 'inhibition of BCR signaling are mediated through SHIP, recently it has been demonstrated that lipopolysaccharide (LPS)-activated B cells from SHIP deficient mice exhibit significant FcyRIIB-mediated inhibition of calcium mobilization, Ins(l,4,5)P3 production, and Erk and Akt phosphorylation (Brauweiler A. et at, 2001, Journal of Immunology, 167(1): 204-211). Accordingly, ex vivo B cells from SHIP deficient mice can be used to characterize the antibodies of the invention. One exemplary assay for determining FcyRIIB-mediated inhibition of BCR signaling by the antibodies of the invention can comprise the following: isolating splenic B cells from SHIP deficient mice, activating said cells with lipopolysachharide, and stimulating said cells with either F(ab')2 anti-IgM to aggregate BCR or with anti-IgM to coaagregate BCR with FcyRIIB. Cells that have been stimulated with intact anti-IgM to coaggregate BCR with FcyRIIB can be further pre-incubated with the antibodies of the invention. FcyRIIB-dependent activity of cells can be measured by standard techniques known in the art. Comparing the level of FcyRIIB-dependent activity in cells that have been pre-incubated with the antibodies and cells that have not been pre-incubated, and comparing the levels would indicate a modulation of FcyRIIB-dependent activity by the antibodies. [00157] Measuring FcyRIIB-dependent activity can include, for example, measuring intracellular calcium mobilization by flow cytometry, measuring phosphorylation of Akt and/or Erk, measuring BCR-mcdiated accumulation of PI(3,4,5)?3, or measuring FcyRIIB-mediated proliferation B cells. [00158] The assays can be used, for example, to identify diabodies or anti-FcyRHB antibodies for use in the invention that modulate FcyRIIB-mediated inhibition of BCR signaling by blocking the ligand (IgG) binding site to FcyRIIB receptor and antagonizing FcyRIIB-mediated inhibition of BCR signaling by preventing coaggregation of FcyRIIB and BCR. The assays can also be used to identify antibodies that enhance coaggregation of FcyRIIB and BCR and agonize FcyRIIB-mediated inhibition of BCR signaling. [00159] The anti-FcyRIIB antibodies can also be assayed for FcyRII-mediated signaling in human monocytes/macrophages. Coaggregation of FcyRIIB with a receptor bearing the immunoreceptor tyrosine-based activation motif (ITAM) acts to down-regulate FcyR-mediated phagocytosis using SHIP as its effector (Tridandapani et al. 2002, J. Biol. Chem. 277(7):5082-9). Coaggregation of FcyRIIA with FcyRIIB results in rapid phosphorylation of the tyrosine residue on FcyRIIB's ITIM motif, leading to an enhancement hi phosphorylation of SHIP, association of SHIP with She, and phosphorylation of proteins having the molecular weight of 120 and 60-65 kDa. In addition, coaggregation of FcyRIIA with FcyRIIB results in down-regulation of phosphorylation of Akt, which is a serine-threonine kinase that is involved In cellular regulation and serves to suppress apoptosis. [00160] The anti-FcyRIIB diabodies can also be assayed for inhibition of FcyR- mediated phagocytosis hi human monocytes/macrophages. For example, cells from a human monocytic cell line, THP-1 can be stimulated either with Fab fragments of mouse monoclonal antibody IV.3 against FcyRH and goat anti-mouse antibody (to aggregate FcyRIIA alone), or with whole IV.3 mouse monoclonal antibody and goat anti-mouse antibody (to coaggregate FcyRIIA and FcyRIIB). In this system, modulation of down stream signaling molecules, such as tyrosine phosphorylation of FcyRIIB, phosphorylation of SHOP, association of SHIP with She, phosphorylation of Akt, and phosphorylation of proteins having the molecular weight of 120 and 60-65 kDa can be assayed upon addition of molecules of the invention to the stimulated cells. In addition, FcyRIIB-dependent phagocytic efficiency of the monocyte cell line can be directly measured in the presence and absence of the antibodies of the invention. 3 [00161] Another exemplary assay for determining inhibition of FcyR-mediated phagocytosis in human monocytes/macrophages by the antibodies of the invention can comprise the following: stimulating THP-1 cells with either Fab of IV.3 mouse anti-FcyRII antibody and goat anti-mouse antibody (to aggregate FcyRIIA alone and elicit FcyRIIA-mediated signaling); or with mouse anti-FcyRII antibody and goat anti-mouse antibody (to coaggregate FcyRIIA and FcyRIIB and inhibiting FcyRIIA-mediated signaling. Cells that have been stimulated with mouse anti-FcyRTI antibody and goat anti-mouse antibody can be further pre-incubated with the molecules of the invention. Measuring FcyRHA-dependent activity of stimulated cells that have been pre-incubated with molecules of the invention and cells that have not been pre-incubated with the antibodies of the invention and comparing levels of FcyRIIA-dependent activity hi these cells would indicate a modulation of FcyRIIA-dependent activity by the antibodies of the invention. [00162] The exemplary assay described can be used for example, to identify binding domains that block ligand binding of FcyRIIB receptor and antagonize FcyRIIB-mediated inhibition of FcyRIIA signaling by preventing coaggregation of FcyRIIB and FcyRIIA. This assay likewise identifies binding domains that enhance coaggregation of FcyRIIB and FcyRIIA and agonize FcyRIIB-mediated Inhibition of FcyRIIA signaling. [00163] The FcyRIIB binding domains of interest can be assayed while comprised I antibodies by measuring the ability of THP-1 cells to phagocytose fluoresceinated IgG-opsonized sheep red blood cells (SRBC) by methods previously described (Tridandapani et at, 2000, J. Biol. Chem. 275: 20480-7). For example, an exemplary assay for measuring phagocytosis comprises of: treating THP-1 cells with the antibodies of the invention or with a control antibody that does not bind to FcyRII, comparing the activity levels of said cells, wherein a difference in the activities of the cells (e.g., resetting activity (the number of THP-1 cells binding IgG-coated SRBC), adherence activity (the total number of SRBC bound to THP-1 cells), and phagocytic rate) would indicate a modulation of FcyRIIA-dependent activity by the antibodies of the invention. This assay can be used to identify, for example, antibodies that block ligand binding of FcyRIIB receptor and antagonize FcyRIIB-mediated inhibition of phagocytosis. This assay can also identify antibodies that enhance FcyRIIB-mediated inhibition of FcyPJIA signaling. [00164] In a preferred embodiment, the binding domains modulate FcyRIIB- dependent activity in human monocytes/macrophages in at least one or more of the following ways: modulation of downstream signaling molecules (e.g., modulation of phosphorylation state of FcyRIIB, modulation of SHIP phosphorylation, modulation of SHIP and She association, modulation of phosphorylation of Akt, modulation of phosphorylation of additional proteins around 120 and 60-65 kDa) and modulation of phagocytosis. 5.1.2 CD16A BINDING DOMAINS [00165] The following section discusses GDI6A binding proteins which can be used as sources for light and heavy chain variable regions for covalent diabody production. In the present invention CD16A binding proteins includes molecules comprising VL and VH domains of anti-CD16A antibodies, which VH and VL domains are used in the production of the diabodies of the present invention. [00166] A variety of CD16A binding proteins may be used in connection with the present invention. Suitable CD16A binding proteins include human or humanized monoclonal antibodies as well as CD16A binding antibody fragments (e.g., scFv or single chain antibodies, Fab fragments, minibodies) and another antibody-like proteins that bind to CD16A via an interaction with a light chain variable region domain, a heavy chain variable region domain, or both. [00167] In some embodiments, the CD16A binding protein for use according to the invention comprises a VL and/or VH domain that has one or more CDRs with sequences derived from a non-human anti-CD 16A antibody, such as a mouse anti-CD 16A antibody, and one or more framework regions with derived from framework sequences of one or more human immunoglobulins. A number of non-human anti-CD16A monoclonal antibodies, from which CDR and other sequences may be obtained, are known (see, e.g., Tamm and Schmidt, 1996, J. Imm. 157:1576-81; Fleit et al., 1989, p.159; LEUKOCYTE TYPING II: HUMAN MYELOID AND HEMATOPOIETIC CELLS, Reinherz et al., eds. New York: Springer-Verlag; 1986; LEUCOCYTE TYPING III: WHITE CELL DIFFERENTIATION ANTIGENS McMichael A J, ed., Oxford: Oxford University Press, 1986); LEUKOCYTE TYPING IV: WHITE CELL DIFFERENTIATION ANTIGENS, Kapp et al., eds. Oxford Univ. Press, Oxford; LEUKOCYTE TYPING V: WHITE CELL DIFFERENTIATION ANTIGENS, Schlossman et al., eds. Oxford Univ. Press, Oxford; LEUKOCYTE TYPING VI: WHITE CELL DIFFERENTIATION ANTIGENS, Kishimoto, ed. Taylor & Francis. In addition, as shown in the Examples, new GDI 6A binding proteins that recognize human CD16A expressed on cells can be obtained using well known methods for production and selection of monoclonal antibodies or related binding proteins (e.g., hybridoma technology, phage display, and the like). See, for example, O'Connel et al,, 2002, J. Mol. Biol. 321:49-56; Hoogenboom and Chames, 2000, Imm. Today 21:371078; Krebs et al., 2001, J. Imm. Methods 254:67-84; and other references cited herein. Monoclonal antibodies from a non-human species can be chimerized or humanized using techniques using techniques of antibody humanization known in the art. [00168] Alternatively, fully human antibodies against CD16A can be produced using transgenic animals having elements of a human immune system (see, e.g., U.S. Pat. Nos. 5,569,825 and 5,545,806), using human peripheral blood cells (Casali et al., 1986, Science 234:476), by screening a DNA library from human B cells according to the general protocol outlined by Huse et al., 1989, Science 246:1275, and by other methods. [00169] In a preferred embodiment, the binding donor is from the 3G8 antibody or a humanized version thereof, e.g., such as those disclosed in U.S. patent application publication 2004/0010124, which is incorporated by reference herein in its entirety. It is contemplated that, for some purposes, it may be advantageous to use CD16A binding proteins that bind the CD16A receptor at the same epitope bound by 3G8, or at least sufficiently close to this epitope to block binding by 3G8. Methods for epitope mapping and competitive binding experiments to identify binding proteins with the desired binding properties are well known to those skilled in the art of experimental immunology. See, for example, Harlow and Lane, cited supra; Stahl ct al., 1983, Methods in Enzymology 9:242-53; Kirkland et al., 1986, J. Immunol. 137:3614-19; Morel et al., 1988, Molec. Immunol. 25:7-15; Cheung et al., 1990, Virology 176:546-52; and Moldenhauer et al., 1990, Scand. J. Immunol. 32:77-82. For instance, it is possible to determine if two antibodies bind to the same site by using one of the antibodies to capture the antigen on an ELISA plate and then measuring tEe ability of the second antibody to bind to the captured antigen. Epitope comparison can also be achieved by labeling a first antibody, directly or indirectly, with an enzyme, radionuclide or fluorophore, and measuring the ability of an uulabeled second antibody to inhibit the binding of the first antibody to the antigen on cells, in solution, or on a solid phase. [00170] It is also possible to measure the ability of antibodies to block the binding of the CD16A receptor to immune complexes formed on ELISA plates. Such immune complexes are formed by first coating the plate with an antigen such as fluorescein, then applying a specific anti-fluorescein antibody to the plate. This immune complex then serves as the ligand for soluble Fc receptors such as sFcRIIIa. Alternatively a soluble immune complex may be formed and labeled, directly or indirectly, with an enzyme radionuclide or fluorophore. The ability of antibodies to inhibit the binding of these labeled immune complexes to Fc receptors on cells, in solution or on a solid phase can then be measured. [00171] CD 16A binding proteins of the invention may or may not comprise a human immunoglobulin Fc region. Fc regions are not present, for example, in scFv binding proteins. Fc regions are present, for example, in human or humanized tetrameric monoclonal IgG antibodies. As described supra, in some embodiments of the present invention, the CD16A binding protein includes an Fc region that has an altered effector function, e.g., reduced affinity for an effector ligand such as an Fc receptor or Cl component of complement compared to the unaltered Fc region (e.g., Fc of naturally occurring IgGl, proteins). In one embodiment the Fc region is not glycosylated at the Fc region amino acid corresponding to position 297. Such antibodies lack Fc effector function. [00172] Thus, the CD16A binding protein may not exhibit Fc-mediated binding to an effector ligand such as an Fc receptor or the Cl component of complement due to the absence of the Fc domain in the binding protein while, in other cases, the lack of binding or effector function is due to an alteration in the constant region of the antibody. 5.1.2.1 CD16A Binding Proteins Comprising CDR Sequences Similar to a mAb 3G8 CDR Sequences. [00173] CD 16A binding proteins that can be used in the practice of the invention include proteins comprising a CDR sequence derived from (i.e., having a sequence the same as or similar to) the CDRs of the mouse monoclonal antibody 3G8. Complementary cDNAs encoding the heavy chain and light chain variable regions of the mouse 3G8 monoclonal antibody, including the CDR encoding sequences, were cloned and sequenced as described. The nucleic acid and protein sequences of 3G8 are provided below. Using the mouse variable region and CDR sequences, a large number of chimeric and humanized monoclonal antibodies, comprising complementary determining regions derived from 3G8 CDRs were produced and their properties analyzed. To identify humanized antibodies that bind CD16A with high affinity and have other desirable properties, antibody heavy chains comprising a VH region with CDRs derived from 3G8 were produced and combined (by coexpression) with antibody light chains comprising a VL region with CDRs derived from 3O8 to produce a tetrameric antibody for analysis. Properties of the resulting tetrameric antibodies were determined as described below. As described below, CD16A binding proteins comprising 3G8 CDRs, such as the humanized antibody proteins described herein, may be used according to the invention. 5.1.2.1.1 VH Region [00174] In one aspect, the CD16A binding protein of the invention may comprise a heavy chain variable domain in which at least one CDR (and usually three CDRS) have the sequence of a CDR (and more typically all three CDRS) of the mouse monoclonal antibody 3G8 heavy chain and for which the remaining portions of the binding protein are substantially human (derived from and substantially similar to, the heavy chain variable region of a human antibody or antibodies). [00175] In an aspect, the invention provides a humanized 3G8 antibody or antibody fragment containing CDRs derived from the 3G8 antibody in a substantially human framework, but in which at least one of the CDRs of the heavy chain variable domain differs in sequence from the corresponding mouse antibody 3G8 heavy chain CDR. For example, in one embodiment, the CDR(S) differs from the 3G8 CDR sequence at least by having one or more CDR substitutions shown known in the art to affect binding of 3G8 to CD16A, as known in the art or as disclosed in Tables 3 and 4A-H. Suitable CD 16 binding proteins may comprise 0, 1,2, 3, or 4, or more of these substitutions (and often have from 1 to 4 of these substitutions) and optionally can have additional substitutions as well. Table 3. VH Domain Substitutions Table 4A. VH Sequences Derived from 3G8 VH (Table 4A Removed) "•Letters in Table 4A refer to sequences in Tables 4 B-H. TABLE 4B Fill (Table 4B Removed) TABLE 4D FR2 (Table 4E Removed) TABLE 4E CDR2 TABLE 4F FR3 (Table 4F Removed) TABLE 4G CDR3 TABLE 4H FR4 (Table 4H Removed) [00176] In one embodiment, a CD16A binding protein may comprise a heavy chain variable domain sequence that is the same as, or similar to, the VH domain of the Hu3G8VH-l construct, the sequence of which is provided in SEQ ID N0:70. For example, the invention provides a CD 16A binding protein comprising a VH domain with a sequence that (1) differs from the VH domain of Hu3G8VH-l (SEQ ID NO:70) by zero, one, or more than one of the CDR substitutions set forth in Table 1; (2) differs from the VH domain of Hu3G8VH-l by zero, one or more than one of the framework substitutions set forth in Table 1; and (3) is at least about 80% identical, often at least about 90%, and sometimes at least about 95% identical, or even at least about 98% identical to the Hu3G8VH-l VH sequence at the remaining positions. [00177] Exemplary VH domains of CD 16 binding proteins of the invention have the sequence of 3G8VH, Hu3G8VH-5 and Hu3G8VH-22 (SEQ ID NO:81, SEQ ID NO.71 and SEQ ID N0:72, respectively)e, Examplary nucleotide sequences encoding the sequences of 3G8VH and Hu3G8VH-5 (SEQ ID NO:81 and SEQ ID NOJ1, respectively) are provided by SEQ ID N0:82 and SEQ ID N0:83, respectively. [00178] The VH domain may have a sequence that differs from that of Hu3G8VH-l (SEQ ID NO:70) by at least one, at least two, at least three, at least four 4, at least five, or at least six of the substitutions shown in Table 3. These substitutions are believed to result in increased affinity for CD 16 A and/or reduce the immunogenicity of a CD 16 A binding protein when administered to humans. In certain embodiments, the degree of sequence identity with the Hu3G8VH-l VH domain at the remaining positions is at least about 80%, at least about 90%, at least about 95% or at least about 98%. [00179] For illustration and not limitation, the sequences of a number of CD 16A building protein VH domains is shown in Table 4. Heavy chains comprising these sequences fused to a human Cyl constant region were coexpressed with the hu3G8VL-l light chain (described below) to form tetrameric antibodies, and binding of the antibodies to CD16A was measured to assess the effect of ammo acid substitutions compared to the hu3G8VH-l VH domain. Constructs in which the VH domain has a sequence of hu3G8VH-l, 2,1, 4, 5, 8,12,14,16,17,18,19,20,22,23, 24,25,26, 27, 28,29, 30, 31, 32, 33,34,35, 36,37,42, 43, 44 and 45 showed high affinity binding, with hu3G8VH-6 and -40 VH domains showing intermediate binding. CD16A binding proteins comprising the VH domains of hu3G8VH-5 and hu3G8VH-22 (SEQ ID NO:71 and SEQ ID NO:72, respectively) are considered to have particularly favorable binding properties. 5.1.2.2 VL Region [00180] Similar studies were conducted to identify light chain variable domain sequences with favorable binding properties. In one aspect, the invention provides a CD16A binding protein containing a light chain variable domain in which at least one CDR (and usually three CDRs) has the sequence of a CDR (and more typically all three CDRs) of the mouse monoclonal antibody 3G8 light chain and for which the remaining portions of the binding protein are substantially human (derived from and substantially similar to, the heavy chain variable region of a human antibody or antibodies). [00181] hi one aspect, the invention provides a fragment of a humanized 3G8 antibody containing CDRs derived from the 3G8 antibody in a substantially human framework, but hi which at least one of the CDRs of the light chain variable domain differs in sequence from the mouse monoclonal antibody 3G8 light chain CDR. In one embodiment, the CDR(s) differs from the 3G8 sequence at least by having one or more amino acid substitutions in a CDR, such as, one or more substitutions shown in Table 2 (e.g., arginine at position 24 in CDRl; serine at position 25 in CDRl; tyrosine at position 32 in CDRl; leucine at position 33 in CDRl; aspartic acid, tryptophan or serine at position 50 in CDR2; serine at position 53 in CDR2; alanine or glutamine at position 55 in CDR2; threonine at position 56 in CDR2; serine at position 93 in CDR3; and/or threonine at position 94 in CDR3). In various embodiments, the variable domain can have 0,1,2,3,4, 5, or more of these substitutions (and often have from 1 to 4 of these substitutions) and optionally, can have additional substitutions as well. [00182] In one embodiment, a suitable CD16A binding protein may comprise a light chain variable domain sequence that is the same as, or similar to, the VL domain of the Hu3G8VL-l (SEQ ID NO:73) construct, the sequence of which is provided in Table 6. For example, the invention provides a CD16A binding protein comprising a VL domain with a sequence that (1) differs from the VL domain of Hu3G8VL-l (SEQ ID NO:73) by zero, one, or more of the CDR substitutions set forth in Table 5; (2) differs from the VL domain of Hu3G8VL-l by zero, one or more of the framework substitutions set forth in Table 5; and (3) is at least about 80% identical, often at least about 90%, and sometimes at least about 95% identical, or even at least about 98% identical to the Hu3G8VL-l VL sequence (SEQ ID NO:73) at the remaining positions. Table 5. 3G8 VL Domain Substitutions Table 6. VL Sequences Derived from 3G8 VL* *Letters in Table 6A refer to sequences in Tables 6B-H. TABLE 6C CDR1 (Table 6C Removed) TABLE 6D FR2 (Table 6D Removed) TABLE 6E CDR2 (Table 6E Removed) TABLE 6F FR3 (Table 6F Removed) TABLE 6G CDR3 TABLE 611 FR4 (Table 6G Removed) [00183] Exemplary VL domains of CD 16 binding proteins of the invention have the sequence of 3G8VL, Hu3G8VL-l or Hu3G8VL-43, (SEQ IDNO:84, SEQ IDNO:73 and SEQ ID N0:74, respectively) as shown in Tables 5 and 6. Exemplary nucleotide sequences encoding 3G8VL (SEQ ID NO:84) and Hu3G8VL-l (SEQ ID NO:73) are provided in SEQ ID N0:85 and SEQ ID NO:86, respectively. [00184] The VL domain may have a sequence that differs from that of Hu3G8VL- 1 (SEQ ID N0:73) by zero, one, at least two, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, or at least 9 of the substitutions shown in Table 2. These substitutions are believed to result in increased affinity for CD16A and/or reduce the immunogenicity of a CD16A binding protein when administered to humans. In certain embodiments, the degree of sequence identity at the remaining positions is at least about 80%, at least about 90% at least about 95% or at least about 98%. [00185] For illustration and not limitation, the sequences of a number of CD 16 A binding proteins VL domains is shown in Table 6. Light chains comprising these sequences fused to a human CK. constant domain were coexpressed with a Hu3G8VH heavy chain (described above) to form tetrameric antibodies, and the binding of the antibodies to CD16A was measured to assess the effect of arnino acid substitutions compared to the Hu3G8VL-l VL domain (SEQ ID N0;73). Constructs in which the VL domain has a sequence of hu3G8VL-l, 2, 3,4, 5,10,16, 18,19,21,22,24,27, 28, 32,33,34, 35, 36, 37, and 42 showed high affinity binding and hu3G8VL-15,17,20,23,25,26,29,30,31, 38, 39,40 and 41 showed intermediate binding. CD16A binding proteins comprising the VL domains of hu3G8VL-l, hu3G8VL-22, and hu3G8VL-43 are considered to have particularly favorable binding properties (SEQ ID NO:73, SEQ ID NO:75 and SEQ ID N0:74, respectively). 5.1.2.2.1 Combinations of VL and/or VII Domains [00186] As is known in the art and described elsewhere herein, imrnunoglobulin light and heavy chains can be recombinantly expressed under conditions in which they associate to produce a diabody, or can be so combined in vitro. It will thus be appreciated that a 3G8- derived VL-domain described herein can be combined a 3G8-derived VH-domain described herein to produce a CD16A binding diabody, and all such combinations are contemplated. [00187] For illustration and not for limitation, examples of useful CD16A diabodies are those comprising at least one VH domain and at least one VL domain, where the VH domain is from hu3G8VH-l, hu3G8VH-22 or hu3G8VH-5 (SEQ ID NO:70, SEQ ID N0:72 and SEQ ID NO:71, respectively) and the VL domain is from hu3G8VL-l, hu3G8VL-22 or hu3G8VL-43 (SEQ ID NO:73, SEQ ID NO:75 and SEQ ID NO:43, respectively). In particular, humanized antibodies that comprise hu3G8VH-22 (SEQ ID NO:22) and either, hu3G8VL-l, hu3G8VL-22 or hu3G8VL-43 (SEQ ID NO:73, SEQ ID N0:72 and SEQ ID NO:74, respectively), or hu3G8VH-5 (SEQ ID NO:71) and hu3G8VL-l (SEQ ID N0:73) have favorable properties. [00188] It will be appreciated by those of skill that the sequences of VL and VH domains described here can be further modified by art-known methods such as affinity maturation (see Schier et al., 1996, J. Mol. Biol. 263:551-67; Daugherty et al., 1998, Protein Eng. 11:825-32; Boder et al., 1997, Nat. Biotechnol. 15:553-57; Boder et al., 2000, Proc. Natl. Acad. Sci. U.S.A 97:10701-705; Hudson and Souriau, 2003, Nature Medicine 9:129-39). For example, the GDI 6A binding proteins can be modified using affinity maturation techniques to identify proteins with increased affinity for CD16A and/or decreased affinity for GDI6B. [00189] One exemplary CD 16 binding protein is the mouse 3G8 antibody. Amino acid sequence comprising the VH and VL domains of humanized 3G8 are described in FIGS. 2, 9,14 and set forth in SEQ ID NO:9, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID N0:14, SEQ ID N0:15, SEQ ID NO:16S SEQ ID N0:18, SEQ ID N0:19, SEQ ID N0:20, SEQ ID N0:21, SEQ ID N0:22, SEQ ID NO:70, SEQ ID N0:71, SEQ ID NO:72, SEQ ID NO:73andSEQIDNO:74. 5.2 DIABODIES COMPRISING Fc REGIONS OR PORTIONS THEREOF [00190] The invention encompasses diabody molecules comprising Fc domains or portions thereof (e.g., a CH2 or CHS domain). In certain embodiments the Fc domain, or portion(s) thereof, comprises one or more constant domain(s) of the Fc region of IgG2, IgG3 or IgG4 (e.g., CH2 or CHS). In other embodiments, the invention encompasses molecules comprising and Fc domain or portion therof, wherein said Fc domain or portion thereof comprises at least one amino acid modification (e.g. substitution) relative to a comparable wild-type Fc domain or portion thereof. Variant Fc domains are well known in the art, and are primarily used to alter the phenotype of the antibody comprising said variant Fc domain as assayed in any of the binding activity or effector function assays well known in the art, e.g. ELISA, SPR analysis, or ADCC. Such variant Fc domains, or portions thereof, have use in the present invention by conferring or modifying the effector function exhibited by a diabody molecule of the invention comprising an Fc domain (or portion thereof) as functionally assayed, e.g., in anNK dependent or macrophage dependent assay. Fc domain variants identified as altering effector function are disclosed in International Application W004/063351, U.S. Patent Application Publications 2005/0037000 and 2005/0064514, U.S. Provisional Applications 60/626,510, filed November 10,2004, 60/636,663, filed December 15,2004, and 60/781,564, filed March 10, 2006, and U.S. Patent Applications 11/271,140, filed November 10, 2005, and 11/305,787, filed December 15,2005, concurrent applications of the Inventors, each of which is incorporated by reference hi its entirety. [00191] In other embodiments, the invention encompasses the use of any Fc variant known in the art, such as those disclosed in Duncan et al, 1988, Nature 332:563-564; Lund et al., 1991, J. Immunol 147:2657-2662; Lund et al, 1992, Mol Immunol 29:53-59; Alegre et al, 1994, Transplantation 57:1537-1543; Hutchins et al., 1995, Proc Natl. Acad Sci U S A 92:11980-11984; Jefferis et al, 1995, Immunol Lett. 44:111-117; Lund et al, 1995, Faseb J 9:115-119; Jefferis et al, 1996, Immunol Lett 54:101-104; Lund et al, 1996, J Immunol 157:49634969; Armour et al, 1999, Eur J Immunol 29:2613-2624; Idusogie et al, 2000, J Immunol 164:41784184; Reddy et al, 2000, J Immunol 164:1925-1933; Xu et al, 2000, Cell Immunol 200:16-26; Idusogie et al, 2001, J Immunol 166:2571-2575; Shields et al, 2001, J Biol Chem 276:6591-6604; Jefferis et al, 2002, Immunol Lett 82:57-65; Presta et al., 2002, Biochem Soc Trans 30:487-490); US 5,624,821; US 5,885,573; US 6,194,551; PCT WO 00/42072; PCT WO 99/58572; each of which is incorporated herein by reference in its entirety. [00192] In certain embodiments, said one or more modifications to the amino acids of the Fc region reduce the affinity and avidity of the Fc region and, thus, the diabody molecule of the invention, for one or more FcyR receptors. In a specific embodiment, the invention encompasses diabodies comprising a variant Fc region, or portion thereof, wherein said variant Fc region comprises at least one amino acid modification relative to a wild type Fc region, which variant Fc region only binds one FcyR, wherein said FcyR is FcyRHIA. In another specific embodiment, the invention encompasses diabodies comprising a variant Fc region, or portion thereof, wherein said variant Fc region comprises at least one amino acid modification relative to a wild type Fc region, which variant Fc region only binds one FcyR, wherein said FcyR is FcyRIIA. In another specific embodiment, the invention encompasses diabodies comprising a variant Fc region, or portion thereof, wherein said variant Fc region comprises at least one amino acid modification relative to a wild type Fc region, which variant Fc region only binds one FcyR, wherein said FcyR is FcyRIIB. In certain embodiments, the invention encompasses molecules comprising a variant Fc domain wherein said variant confers or mediates increased ADCC activity and/or an increased binding to FcyRIIA (CD32A), relative to a molecule comprising no Fc domain or comprising a wild-type Fc domain, as measured using methods known to one skilled in the art and described herein. In alternate embodiments, the invention encompasses molecules comprising a variant Fc domain wherein said variant confers or mediates decreased ADCC activity (or other effector function) and/or an increased binding to FcyRIIB (CD32B), relative to a molecule comprising no Fc domain or comprising a wild-type Fc domain, as measured using methods known to one skilled in the art and described herein. [00193] The invention also encompasses the use of an Fc domain comprising domains or regions from two or more IgG isotypes. As known in the art, amino acid modification of the Fc region can profoundly affect Fc-mediated effector function and/or binding activity. However, these alterations in functional characteristics can be further refined and/or manipulated when implemented in the context of selected IgG isotypes. Similarly, the native characteristics of the isotype Fc may be manipulated by the one or more amino acid modifications. The multiple IgG isotypes (i.e., IgGl, IgG2, IgG3 and IgG4) exhibit differing physical and functional properties including serum half-life, complement fixation, FcyR binding affinities and effector function activities (e.g. ADCC, CDC) due to differences in the amino acid sequences of their hinge and/or Fc domains. In certain embodiments, the amino acid modification and IgG Fc region are independently selected based on their respective, separate binding and/or effector function activities in order to engineer a diabody with desired characteristics. In most embodiments, said amino acid modifications and IgG hinge/Fc regions have been separately assayed for binding and/or effector function activity as described herein or known in the art in an the context of an IgGl. In certain embodiments, said amino acid modification and IgG hinge/Fc region display similar functionality, e.g., increased affinity for FcyRIIA, when separately assayed for FcyR binding or effector function in the context of the diabody molecule or other Fc-containing molecule (e.g. and immunoglobulin). The combination of said amino acid modification and selected IgG Fc region then act additively or, more preferably, synergistically to modify said functionality in the diabody molecule of the invention, relative to a diabody molecule of the invention comprising a wild-type Fc region. In other embodiments, said amino acid modification and IgG Fc region display opposite functionalities, e.g., increased and decreased, respectively, affinity for FcyRIIA, when separately assayed for FcyR binding and/or effector function in the context of the diabody molecule or other Fc containing molecule (e.g., an immunoglobulin) comprising a wild-type Fc region as described herein or known in the art; the combination of said "opposite" amino acid modification and selected IgG region then act to selectively temper or reduce a specific functionality in the diabody of the invention relative to a diabody of the invention not comprising an Fc region or comprising a wild-type Fc region of the same isotype. Alternatively, the invention encompasses variant Fc regions comprising combinations of amino acid modifications known in the art and selected IgG regions that exhibit novel properties, which properties were not detectable when said modifications and/or regions were independently assayed as described herein. [00194] The functional characteristics of the multiple IgG isotypes, and domains thereof, are well known in the art. The amino acid sequences of IgGl, IgG2, IgG3 and IgG4 are presented in FIGS. 1A-1B. Selection and/or combinations of two or more domains from specific IgG isotypes for use in the methods of the invention may be based on any known parameter of the parent istoypes including affinity to FcyR (Table 7; Flesch and Neppert, 1999, J. Clin. Lab. Anal. 14:141-156; Chappel et ah, 1993, J. Biol. Chem. 33:25124-25131; Chappel et al., 1991, Proc.Natl. Acad. Sci. USA 88:9036-9040, each of which is hereby incorporated by reference in its entirety). For example, use of regions or domains from IgG isotypes that exhibit limited or no binding to FcyRIIB, e.g., IgG2 or IgG4, may find particular use where a diabody is desired to be engineered to maximize binding to an activating receptor and minimize binding to an inhibitory receptor. Similarly, use of Fc regions or domains from IgG isotypes known to preferentially bind Clq or FcyRfflA, e.g., IgG3 (Bruggemann et al., 1987, J. Exp. Med 166:1351-1361), may be combined with Fc amino acid modifications of known in the art to enhance ADCC, to engineer a diabody molecule such that effector function activity, e.g., complement activation or ADCC, is maximized. Table 7. General characteristics of IgG binding to FcyR, adapted from FIcsch and Ncppcrt, 1999, J. Clin. Lab. Anal. 14:141-156 (Table 7 Removed) binds only complexed IgG [00195] 5.3 MOLECULAR CONJUGATES [00196] The diabody molecules of the invention may be rccombinantly fused or chemically conjugated (including both covalently and non-covalently conjugations) to heterologous polypeptides (i.e., an unrelated polypeptide; or portion thereof, preferably at least 10, at least 20, at least 30, at least 40, at least 50, at least 60, at least 70, at least 80, at least 90 or at least 100 amino acids of the polypeptide to generate fusion proteins. The fusion does not necessarily need to be direct, but may occur through linker sequences. [00197] Further, the diabody molecules of the invention (i.e., polypeptides) may be conjugated to a therapeutic agent or a drug moiety that modifies a given biological response. As an alternative to direct conjugation, owing to the multiple epitope binding sites on the multivalent, e.g., tetravalent, diabody molecules of the invention, at least one binding region of the diabody may be designed to bind the therapeutic agent or desired drug moiety without affecting diabody binding. [00198] Therapeutic agents or drug moieties are not to be construed as limited to classical chemical therapeutic agents. For example, the drug moiety may be a protein or polypeptide possessing a desired biological activity. Such proteins may include, for example, a toxin such as abrin, ricin A, pseudomonas exotoxin (Le., PE-40), or diphtheria toxin, ricin, gelonin, and pokeweed antiviral protein, a protein such as tumor necrosis factor, interferons including, but not limited to, a-interferon (IFN-a), p-interferon (IFN-P), nerve growth factor (NGF), platelet derived growth factor (PDGF), tissue plasminogen activator (TPA), an apoptotic agent (e.g., TNF-a, TNF-P, AIM I as disclosed in PCT Publication No. WO 97/33899), AIM E (see, PCT Publication No. WO 97/34911), Fas ligand (Takahashi et al, J. Immunol, 6:1567-1574,1994), and VEGI (PCT Publication No. WO 99/23105), a thrombotic agent or an anti-angiogenie agent (e.g., angiostatin or endostatin), or a biological response modifier such as, for example, a lymphokine (e.g., interleukin-1 ("IL-1"), interleukin-2 ("IL-2"), interleukin-6 ("IL-6"), granulocyte macrophage colony stimulating factor ("GM-CSF"), and granulocyte colony stimulating factor ("G-CSF"), macrophage colony stimulating factor, ("M-CSF"), or a growth factor (e.g., growth hormone ("GH"); proteases, or ribonucleases. [00199] The diabody molecules of the invention (/. e., polypeptides) can be fused to marker sequences, such as a peptide to facilitate purification. In preferred embodiments, the marker amino acid sequence is a hexa-histidine peptide, such as the tag provided in apQE vector (QIAGEN, Inc., 9259 Eton Avenue, Chatsworth, CA, 91311), among others, many of which are commercially available. As described in Gentz et al, 1989, Proc. Natl. Acad. Sci. USA, 86:821-824, for instance, hexa-histidine provides for convenient purification of the fusion protein. Other peptide tags useful for purification include, but are not limited to, the hemagglutinin "HA" tag, which corresponds to an epitope derived from the influenza hemagglutinin protein (Wilson et al., Cell, 37:767 1984) and the "flag" tag (Knappik et al, Biotechniques, 17(4):754-761, 1994). [00200] Additional fusion proteins may be generated through the techniques of gene- shuffling, motif-shuffling, exon-shuffling, and/or codon-shuffling (collectively referred to as "DNA shuffling"). DNA shuffling may be employed to alter the activities of molecules of the invention (e.g., epitope binding sites with higher affinities and lower dissociation rates). See, generally, U.S. Patent Nos. 5,605,793; 5,811,238; 5,830,721; 5,834,252; and 5,837,458, and Patten e/ al., 1997, Curr. Opinion Biotechnol. 8:724-33; Harayama, 1998, Trends Biotechnol. 16:76; Hansson, et al, 1999, J. Uol BioL 287:265; and Lorenzo and Blasco, 1998, BioTechniques 24:308 (each of these patents and publications are hereby incorporated by reference in its entirety). The diabody molecules of the invention, or the nucleic acids encoding the molecules of the invention, may be further altered by being subjected to random mutagenesis by error-prone PCR, random nucleotide insertion or other methods prior to recombination. One or more portions of a polynucleotide encoding a molecule of the invention, may be recombined with one or more components, motifs, sections, parts, domains, fragments, etc. of one or more heterologous molecules. [00201] The present invention also encompasses diabody molecules of the invention conjugated to or immunospecifically recognizing a diagnostic or therapeutic agent or any other molecule for which serum half-life is desired to be increased/decreased and/or targeted to a particular subset of cells. The molecules of the invention can be used diagnostically to, for example, monitor the development or progression of a disease, disorder or infection as part of a clinical testing procedure to, e.g., determine the efficacy of a given treatment regimen. Detection can be facilitated by coupling the molecules of the invention to a detectable substance or by the molecules immunospecifically recognizing the detectable substance. Examples of detectable substances include various enzymes, prosthetic groups, fluorescent materials, luminescent materials, biolumincscent materials, radioactive materials, positron emitting metals, and nonradioactive paramagnetic metal ions. The detectable substance may be coupled or conjugated either directly to the molecules of the invention or indirectly, through an intermediate (such as, for example, a linker known in the art) using techniques known in the art, or the molecule may immunospecifically recognize the detectable substance: immunospecifically binding said substance. See, for example, U.S. Patent No. 4,741,900 for metal ions which can be conjugated to antibodies for use as diagnostics according to the present invention. Such diagnosis and detection can be accomplished designing the molecules to immunospecifically recognize the detectable substance or by coupling the molecules of the invention to detectable substances including, but not limited to, various enzymes, enzymes including, but not limited to, horseradish peroxidase, alkaline phosphatase, beta-galactosidase, or acetylcholinestcrase; prosthetic group complexes such as, but not limited to, streptavidin/biotin and avidin/biotin; fluorescent materials such as, but not limited to, umbelliferone, fluorescein, fluorescein isothiocyanate, rhodamine, dichlorotriazinylamine fluorescein, dansyl chloride or phycoerythrin; luminescent material such as, but not limited to, luminol; bioluminescent materials such as, but not limited to, luciferase, luciferin, and aequorin; radioactive material such as, but not limited to, bismuth (213Bi), carbon (14C), chromium (51Cr), cobalt (57Co), fluorine (18F), gadolinium (!53Gd, I59Gd), gallium (68Ga, 67Ga), germanium (68Gc), holmium (r66Ho), indium (H5In, 113In7112In, niln), iodine (131I, U5I, ml, ml), lanthanium (140La), lutetium (177Lu), manganese (54Mn), molybdenum (99Mo), palladium (103Pd), phosphorous (32P), praseodymium (142Pr), promcthium (H9Pm), rhenium (l86Re, 188Re), rhodium (losRh), ruthemium (97Ru), samarium (153Sm), scandium (47Sc), selenium (75Se), strontium (85Sr), sulfur (35S), technetium (99Tc), thallium (201Ti), tin (113Sn, I17Sn), tritium (3H), xenon (133Xe), ytterbium (169Yb, 175Yb), yttrium (90Y), zinc (65Zn); positron emitting metals using various positron emission tomographies, and nonradioactive paramagnetic metal ions. [00202] The diabody molecules of the invention may immunospecifically recognize or be conjugated to a therapeutic moiety such as a cytotoxin (e.g., a cytostatic or cytocidal agent), a therapeutic agent or a radioactive element (e.g., alpha-emitters, gamma-emitters, etc.}. Cytotoxins or cytotoxic agents include any agent that is detrimental to cells. Examples include paclitaxol, cytochalasin B, gramicidin D, ethidium bromide, emetine, mitomycin, etoposide, tenoposide, vincristine, vinblastine, colchicin, doxorubicin, daunorubicin, dihydroxy anthracin dione, mitoxantrone, mithramycin, actinomycin D, 1-dehydrotestosteronej glucocorticoids, procaine, tetracaine, Hdocaine, propranolol, and puromycin and analogs or homologs thereof. Therapeutic agents include, but are not limited to, antimetabolites (e.g., methotrexate, 6-mercaptopurine, 6-thioguanine, cytarabine, 5-fluorouracil decarbazine), alkylating agents (e.g., mechlorethamine, thioepa chlorambucil, melphalan, carmustine (BSNU) and lomustine (CCNU), cyclothosphamide, busulfan, dibromomannitol, streptozotocin, mitomycin C, and cisdichlorodiamine platinum (H) (DDP) cisplatin), anthracyclines (e.g., daunorubicin (formerly daunomycin) and doxorubicin), antibiotics (e.g., dactinomycin (formerly actinomycin), bleomycin, mithramycin, and anthramycin (AMC), and anti-mitotic agents (e.g., vincristine and vinblastine). [00203] Moreover, a diabody molecule of the invention can be conjugated to or be designed to immunospecifically recognize therapeutic moieties such as a radioactive materials or macrocyclic chclators useful for conjugating radiometal ions (see above for examples of radioactive materials). In certain embodiments, the macrocyclic chelator is l,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid (DOTA) which can be attached to the polypeptide via a linker molecule. Such linker molecules are commonly known in the art and described in Denardo et al, 1998, Clin Cancer Res. 4:2483-90; Peterson et al, 1999, Bioconjug. Chem. 10:553; and Zimmerman et al, 1999, Nucl Med. Biol 26:943-50 each of which is incorporated herein by reference in their entireties. [00204] Techniques for conjugating such therapeutic moieties to polypeptides, including e.g., Fc domains, arc well known; see, e.g., Arnon et al, "Monoclonal Antibodies For Immunotargeting Of Drugs In Cancer Therapy", in Monoclonal Antibodies And Cancer Therapy, Reisfeld et al. (eels.), 1985, pp. 243-56, Alan R. Liss, Inc.); Hellstrom et al, "Antibodies For Drug Delivery", in Controlled Drug Delivery (2nd Ed.), Robinson et al (eds.), 1987, pp. 623-53, Marcel Dekkcr, Inc.); Thorpe, "Antibody Carriers Of Cytotoxic Agents In Cancer Therapy: A Review", in Monoclonal Antibodies '84: Biological And Clinical Applications, Pinchera et al. (eds,), 1985, pp. 475-506); "Analysis, Results, And Future Prospective Of The Therapeutic Use Of Radiolabeled Antibody In Cancer Therapy", in Monoclonal Antibodies For Cancer Detection And Therapy^ Baldwin et al. (eds.), 1985, pp. 303-16, Academic Press; and Thorpe et al.Jmmunol. Rev., 62:119-58, 1982. [00205] The diabody molecule of the invention may be administered with or without a therapeutic moiety conjugated to it, administered alone, or in combination with cytotoxic factor(s) and/or cytokine(s) for use as a therapeutic treatment. Where administered alone, at least one epitope of a multivalent, e.g., tetravalent, diabody molecule may be designed to immunospecifically recognize a therapeutic agent, e.g., cytotoxic factor(s) and/or cytokine(s), which may be administered concurrently or subsequent to the molecule of the invention. In this manner, the diabody molecule may specifically target the therapeutic agent in a manner similar to direct conjugation. Alternatively, a molecule of the invention, can be conjugated to an antibody to form an antibody heteroconjugate as described by Segal in U.S. Patent No. 4,676,980, which is incorporated herein by reference in its entirety. Diabody molecules of the invention may also be attached to solid supports, which are particularly useful for immunoassays or purification of the target antigen. Such solid supports include, but are not limited to, glass, cellulose, polyacrylamide, nylon, polystyrene, polyvinyl chloride or polypropylene. 5.4 CHARACTERIZATION OF BINDING OF DIABODY MOLECULES [00206] The diabody molecules of the present invention may be characterized in a variety of ways. In particular, molecules of the invention may be assayed for the ability to immunospecifically bind to an antigen, e.g., FcPJIIA or FcRIIB, or, where the molecule comprises an Fc domain (or portion thereof) for the ability to exhibit Fc-FcyR interactions, i.e. specific binding of an Fc domain (or portion thereof) to an FcyR. Such an assay may be performed in solution (e.g., Houghten, Bio/Techniques, 13:412-421, 1992), on beads (Lam, Nature, 354:82-84,1991, on chips (Fodor, Nature, 364:555-556,1993), on bacteria (U.S. Patent No. 5,223,409), on spores (U.S. Patent Nos. 5,571,698; 5,403,484; and 5,223,409), onplasmids (Cull etal,Proc. Natl. Acad. Sci. USA, 89:1865-1869,1992) oronphage (Scott and Smith, Science, 249:386-390,1990; Devlin, Science, 249:404-406, 1990; Cwirla etal, Proc. Natl. Acad. Sci. USA, 87:6378-6382,1990; andFelici, J. Mol Biol, 222:301-310,1991) (each of these references is incorporated by reference herein in its entirety). Molecules that have been identified to immunospecifically bind to an antigen, e.g., FcyRIILA, can then be assayed for their specificity and affinity for the antigen. [00207] Molecules of the invention that have been engineered to comprise multiple epitope binding domains may be assayed for immunospecific binding to one or more antigens (e.g., cancer antigen and cross-reactivity with other antigens (e.g., FcyR)) or, where the molecules comprise am Fc domain (or portion thereof) for Fc-FcyR interactions by any method known in the art. Immunoassays which can be used to analyze immunospecific binding, cross-reactivity, and Fc-FcyR interactions include, but are not limited to, competitive and non-competitive assay systems using techniques such as western blots, radioimmunoassays, ELISA (enzyme linked immunosorbent assay), "sandwich" immunoassays, immunoprecipitation assays, precipitin reactions, gel diffusion precipitin reactions, immunodiffusion assays, agglutination assays, complement-fixation assays, immunoradiometric assays, fluorescent immunoassays, protein A immunoassays, to name but a few. Such assays are routine and well known in the art (see, e.g., Ausubel et al, eds, 1994, Current Protocols in Molecular Biology, Vol. 1, John Wiley & Sons, me., New York, which is incorporated by reference herein in its entirety). [00208] The binding affinity and the off-rate of antigen-binding domain interaction or Fc-FcyR interaction can be determined by competitive binding assays. One example of a competitive binding assay is a radioimmunoassay comprising the incubation of labeled antigen, such as tetrameric FcyR (e.g., 3H or 125I, see Section 5.4.1) with a molecule of interest (e.g., molecules of the present invention comprising multiple epitope binding domains in the presence of increasing amounts of unlabeled epitope, such as tetrameric FcyR(see Section 5.4.1), and the detection of the molecule bound to the labeled antigen. The affinity of the molecule of the present invention for an antigen and the binding off-rates can be determined from the saturation data by Scatchard analysis. [00209] The affinities and binding properties of the molecules of the invention for an antigen or FcyR may be initially determined using in vitro assays (biochemical or immunological based assays) known in the art for antigen-binding domain or Fc-FcyR, interactions, including but not limited to ELISA assay, surface plasmon resonance assay, immunoprecipitation assays. Preferably, the binding properties of the molecules of the invention are also characterized by in vitro functional assays for determining one or more FcyR mediator effector cell functions, as described in section 5.4.2. In most preferred embodiments, the molecules of the invention have similar binding properties in in vivo models (such as those described and disclosed herein) as those in in vitro based assays. However, the present invention does not exclude molecules of the invention that do not exhibit the desired phenotype in in vitro based assays but do exhibit the desired phenotype in vivo. [00210] In some embodiments, screening and identifying molecules comprising multiple epitope binding domains and, optionally, Fc domains (or portions thereof) are done functional based assays, preferably in a high throughput manner. The functional based assays can be any assay known in the art for characterizing one or more FcyR mediated effector cell functions such as those described herein in Sections 5.4.2 and 5.4.3. Non-limiting examples of effector cell functions that can be used in accordance with the methods of the invention, include but are not limited to, antibody-dependent cell mediated cytotoxicity (ADCC), antibody-dependent phagocytosis, phagocytosis, opsonization, opsouophagocytosis, cell binding, resetting, Clq binding, and complement dependent cell mediated cytotoxicity, [00211] In a preferred embodiment, BIAcore kinetic analysis is used to determine the binding on and off rates of molecules of the present invention to an antigen or and FcyR. BIAcore kinetic analysis comprises analyzing the binding and dissociation of an antigen or FcyR from chips with immobilized molecules (e.g., molecules comprising epitope binding domains or Fc domains (or portions thereof), respectively) on their surface. BIAcore analysis is described in Section 5.4.3. [00212] Preferably, fluorescence activated cell sorting (FACS), using any of the techniques known to those skilled in the art, is used for immunological or functional based assay to characterize molecules of the invention. Flow sorters are capable of rapidly examining a large number of individual cells that have been bound, e.g., opsonized, by molecules of the invention (e.g., 10-100 million cells per hour) (Shapiro et al, Practical Flow Cytornetry, 1995). Additionally, specific parameters used for optimization of diabody behavior, include but are not limited to, antigen concentration (i.e., FcyR tetrameric complex, see Section 5.4.1), kinetic competition time, or FACS stringency, each of which may be varied in order to select for the diabody molecules comprising molecules of the invention which exhibit specific binding properties, e.g., concurrent binding to multiple epitopes. Flow cytometers for sorting and examining biological cells are well known in the art. Known flow cytometers are described, for example, in U.S. Patent Nos. 4,347,935; 5,464,581; 5,483,469; 5,602,039; 5,643,796; and 6,211,477; the entire contents of which are incorporated by reference herein. Other known flow cytometers are the FACS Vantage™ system manufactured by Becton Dickinson and Company, and the COP AS™ system manufactured by Union Biometrica. [00213] Characterization of target antigen binding affinity or Fc-FcyR binding affinity, and assessment of target antigen or FcyR density on a cell surface may be made by methods well known in the art such as Scatchard analysis or by the use of kits as per manufacturer's instructions, such as Quantum™ Simply Cellular ® (Bangs Laboratories, Inc., Fishers, IN). The one or more functional assays can be any assay known in the art for characterizing one or more FcyR mediated effector cell function as known to one skilled in the art or described herein. In specific embodiments, the molecules of the invention comprising multiple epitope binding domains and, optionally, and Fc domain (or portion thereof) are assayed in an ELISA assay for binding to one or more target antigens or one or more FcyRs, e.g., FcyRIIIA, FcyRIIA, FcyRIIA; followed by one or more ADCC assays. In some embodiments, the molecules of the invention are assayed further using a surface plasmon resonance-based assay, e.g., BIAcore. Surface plasmon resonance-based assays are well known in the art, and are further discussed in Section 5.4.3, and exemplified herein, e.g., in Example 6.1. [00214] In most preferred embodiments, the molecules of the invetion comprising multiple epitope binding domains and, optionally, and Fc domain (or portion thereof) is further characterized in an animal model for interaction with a target antigen (e.g., an FcyR) or for Fc-FcyR interaction. Where Fc-FcyR interactions are to be assessed, preferred animal models for use in the methods of the invention are, for example, transgenic mice expressing human FcyRs, e.g., any mouse model described in U.S. Patent No. 5,877,397, and 6,676,927 which are incorporated herein by reference in their entirety. Further transgenic mice for use in such methods include, but are not limited to, nude knockout FcyRIIIA mice carrying human FcyRIIIA; nude knockout FcyRIIIA mice carrying human FcyRIIA; nude knockout FcyRIIIA mice carrying human FcyRIIB and human FcyRIIIA; nude knockout FcyRIIIA mice carrying human FcyRIIB and human FcyRIIA; nude knockout FcyRIIIA and FcyRIIA mice carrying human FcyRIIIA and FcyRIIA and nude knockout FcyRIIIA, FcyRIIA and FcyRIIB mice carrying human FcyRIIIA, FcyRIIA and FcyRIIB. 5.4.1 BINDING ASSAYS COMPRISING FcyR [00215] Characterization of binding to FcyR by molecules comprising an Fc domain (or portion thereof) and/or comprising epitope binding domain specific for an FcyR may be done using any FcyR, including but not limited to polymorphic variants of FcyR. In some embodiments, a polymorphic variant of FcyRIIIA is used, which contains a phenylalanine at position 158. In other embodiments, characterization is done using a polymorphic variant of FcyRfflA which contains a valine at position 158. FcyRHIA 158V displays a higher affinity for IgGl than 158F and an increased ADCC activity (see, e.g., Koene et al, 1997, Blood, 90:1109-14; VfuetaL, 1997, J. din. Invest. 100:1059-70, both of which are incorporated herein by reference ha their entireties); this residue in fact directly interacts with the lower hinge region of IgGl as recently shown by IgGl-FeyRIIIA co-crystallization studies, see, e.g., Sonderman et al, 2000, Nature, 100: 1059-70, which is incorporated herein by reference in its entirety. Studies have shown that in some cases, therapeutic antibodies have improved efficacy in FcyRIIIA-158V homozygous patients. For example, humanized anti-CD20 monoclonal antibody Rituximab was thcrapeutically more effective inFcyRIIIA158V homozygous patients compared to FcyRIIIA 158F homozygous patients (See, e.g., Cartron et al, 2002 Blood, 99(3): 754-8). In other embodiments, therapeutic molecules comprising this region may also be more effective on patients heterozygous for FcyRJIIA-158V and FcyRIIIA- 158F, and in patients with FcyRIIA-131H, Although not intending to be bound by a particular mechanism of action, selection of molecules of the invention with alternate allotypes may provide for variants that once engineered into therapeutic diabodies will be clinically more efficacious for patients homozygous for said allotype. [00216] An FcyR binding assay was developed for determining the binding of the molecules of the invention to FcyR, and, in particular, for determining binding of Fc domains to FcyR. The assay allowed detection and quantitation of Fc-FcyR interactions, despite the inherently weak affinity of the receptor for its ligand, e.g., in the micromolar range for FcyRJIB and FcyRIIIA. The method is described in detail in International Application W004/063351 and U.S. Patent Application Publications 2005/0037000 and 2005/0064514, each of which is hereby incorporated by reference in its entirety. Briefly, the method involves the formation of an FcyR complex that may be sued in any standard immunoassay known in the art, e.g., FACS, ELISA, surface plasmon resonance, etc. Additionally, the FcyR complex has an improved avidity for an Fc region, relative to an uncomplexed FcyR. According to the invention, the preferred molecular complex is a tetrameric immune complex, comprising: (a) the soluble region of FcyR (e.g., the soluble region of FcyRIIIA, FcyRIIA or FcyRIIB); (b) a biotinylated 15 amino acid AVITAG sequence (AVITAG) operably linked to the C-terminus of the soluble region of FcyR (e.g., the soluble region of FcyRTIIA, FcyRIIA or FcyRIIB); and (c) streptavidin-phycoerytlirin (SA-PE); in a molar ratio to form a tetrameric FcyR complex (preferably in a 5:1 molar ratio). The fusion protein is biotinylated enzymatically, using for example, the E.coli Bir A enzyme, a biotin ligase which specifically biotinylates a lysine residue in the 15 amino acid AVITAG sequence. The biotinylated soluble FcyR proteins are then mixed with SA-PE in a IX SA-PE.-5X biotinylated soluble FcyR molar ratio to form a tetrameric FcyR complex. [00217] Polypeptides comprising Fc regions have been shown to bind the tetrameric FcyR complexes with at least an 8-fold higher affinity than the monomeric uncomplexed FcyR. The binding of polypeptidcs comprising Fc regions to the tetrameric FcyR complexes may be determined using standard techniques known to those skilled in the art, such as for example, fluorescence activated cell sorting (FACS), radioimmunoassays, ELISA assays, etc. [00218] The invention encompasses the use of the immune complexes comprising molecules of the invention, and formed according to the methods described above, for determining the functionality of molecules comprising an Fc region in cell-based or cell-free assays. [00219] As a matter of convenience, the reagents may be provided in an assay kit, i.e., a packaged combination of reagents for assaying the ability of molecules comprising an Fc regions to bind FcyR tetrameric complexes. Other forms of molecular complexes for use in determining Fc-FcyR interactions are also contemplated for use in the methods of the invention, e.g., fusion proteins formed as described in U.S. Provisional Application 60/439,709, filed on January 13, 2003; which is incorporated herein by reference in its entirety. 5.4.2 FUNCTIONAL ASSAYS OF MOLECULES WITH VARIANT HEAVY CHAINS [00220] The invention encompasses characterization of the molecules of the invention comprising multiple epitope binding domains and, optionally, Fc domains (or portions thereof) using assays known to those skilled in the art for identifying the effector cell function of the molecules. In particular, the invention encompasses characterizing the molecules of the invention for FcyR-mediated effector cell function. Additionally, where at least one of the target antigens of the diabody molecule of the invention is an FcyR, binding of the FcyR by the diabody molecule may serve t,o activate FcyR-mediated pathways similar to those activated by FcyR-Fc binding. Thus, where at least one eptiope binding domain of the diabody molecule recognizes an FcyR, the diabody molecule may elicit FcyR-mediated effector cell function without containing an Fc domain (or portion thereof), or without concomitant Fc-FcyR binding. Examples of effector cell functions that can be assayed in accordance with the invention, include but are not limited to, antibody-dependent cell mediated cytotoxicity, phagocytosis, opsonization, opsonophagocytosis, Clq binding, and complement dependent cell mediated cytotoxicity. Any cell-based or cell free assay known to those skilled in the art for determining effector cell function activity can be used (For effector cell assays,'see Perussia et at, 2000, Methods Mol Biol. 121:179-92; Baggiolini et at., 1998 Experientia, 44(10): 841-8; Lehmann etal., 2000 J. Immunol. Methods, 243(1-2): 229-42; Brown EJ. 1994, Methods Cell Biol, 45: 147-64; Munn et al, 1990 J. Exp. Med., 172:231-237, Abdul-Majid et al, 2002 Sccmd. J, Immunol 55: 70-81; Ding et al, 1998, Immunity 8:403-411, each of which is incorporated by reference herein hi its entirety). [00221] In one embodiment, the molecules of the invention can be assayed for FcyR- mediated phagocytosis in human monocytes. Alternatively, the FcyR-mediated phagocytosis of the molecules of the invention may be assayed in other phagocytes, e.g., neutrophils (polymorphonuclear leuckocytes; PMN); human peripheral blood monocytes, monocyte-derived macrophages, which can be obtained using standard procedures known to those skilled in the art (e.g., see Brown EJ. 1994, Methods Cell Biol, 45: 147-164). In one embodiment, the function of the molecules of the invention is characterized by measuring the ability of THP-1 cells to phagocytose fluoresceinated IgG-opsonized sheep red blood cells (SRBC) by methods previously described (Tridandapani et al, 2000, J. Biol. Chem, 275:20480-7). [00222] Another exemplary assay for determining the phagocytosis of the molecules of the invention is an antibody-dependent opsonophagocytosis assay (ADCP) which can comprise the following: coating a target bioparticle such as Escherichia co/z-labeled FITC (Molecular Probes) or Staphylococcus aureus-FTTC with (i) wild-type 4-4-20 antibody, an antibody to fluorescein (See Bedzyk et al, 1989, J. Biol Chem, 264(3): 1565-1569, which is incorporated herein by reference in its entirety), as the control antibody for FcyR-dependent ADCP; or (ii) 4-4-20 antibody harboring the D265A mutation that knocks out binding to FcyRIII, as a background control for FcyR-dependent ADCP (iii) a diabody comprising the epitope binding domain of 4-4-20 and an Fc domain and/or an cpitopc binding domain specific for FcyRIII; and forming the opsonized particle; adding any of the opsonized particles described (i-iii) to THP-1 effector cells (a monocytic cell line available from ATCC) at a 1:1,10:1, 30:1, 60:1, 75:1 or a 100: 1 ratio to allow FcyR-mediated phagocytosis to occur; preferably incubating the cells and E. co//-FITC/antibody at 37°C for 1.5 hour; adding trypan blue after incubation (preferably at room temperature for 2-3 min.) to the cells to quench the fluorescence of the bacteria that are adhered to the outside of the cell surface without being internalized; transferring cells into a FACS buffer (e.g., 0.1%, BSA in PBS, 0.1%, sodium azide), analyzing the fluorescence of the THP1 cells using FACS (e.g., BD FACS Calibur). Preferably, the THP-1 cells used in the assay are analyzed by FACS for expression of FcyR on the cell surface. THP-1 cells express both CD32A and CD64. CD64 is a high affinity FcyR that is blocked in conducting the ADCP assay in accordance with the methods of the invention. The THP-1 cells are preferably blocked with 100 jag/mL soluble IgGl or 10% human serum. To analyze the extent of ADCP, the gate is preferably set on THP-1 cells and median fluorescence intensity is measured. The ADCP activity for individual mutants is calculated and reported as a normalized value to the wild type chMab 4-4-20 obtained. The opsonized particles are added to THP-1 cells such that the ratio of the opsonized particles to THP-1 cells is 30:1 or 60:1. In most preferred embodiments, the ADCP assay is conducted with controls, such as E. co//-FITC hi medium, E. co//-FITC and THP-1 cells (to serve as FcyR-independent ADCP activity), E. coli-FITC, THP-1 cells and wild-type 4-4-20 antibody (to serve as FcyR-dependent ADCP activity), E co/z-FITC, THP-1 cells, 4-4-20 D265A (to serve as the background control for FcyR-dependent ADCP activity). [00223] In another embodiment, the molecules of the invention can be assayed for FcyR-mediated ADCC activity in effector cells, e.g., natural killer cells, using any of the standard methods known to those skilled in the art (See e.g., Perussia et al, 2000, Methods Mol Biol 121: 179-92; Weng et al., 2003, J. Clin. Oncol. 21:3940-3947; Ding et al, Immunity, 1998, 8:403-11). An exemplary assay for determining ADCC activity of the molecules of the invention is based on a 51Cr release assay comprising of: labeling target cells with [51Cr]Na2CrC-4 (this cell-membrane permeable molecule is commonly used for labeling since it binds cytoplasmic proteins and although spontaneously released from the cells with slow kinetics, it is released massively following target cell necrosis); opsonizing the target cells with the molecules of the invention comprising variant heavy chains; combining the opsonized radiolabeled target cells with effector cells in a microtitre plate at an appropriate ratio of target cells to effector cells; incubating the mixture of cells for 16-18 hours at 37°C; collecting supernatants; and analyzing radioactivity. The cytotoxicity of the molecules of the invention can then be determined, for example using the following formula: % lysis - (experimental cpm - target leak cpm)/(detergent lysis cpm - target leak cpm) x 100%. Alternatively, % lysis =(ADCC-AICC)/(maximum release-spontaneous release). Specific lysis can be calculated using the formula: specific lysis = % lysis with the molecules of the Invention - % lysis in the absence of the molecules of the invention. A graph can be generated by varying either the target: effector cell ratio or antibody concentration. [00224] Preferably, the effector cells used in the ADCC assays of the invention arc peripheral blood mononuclear cells (PBMC) that are preferably purified from normal human blood, using standard methods known to one skilled in the art, e.g., using Ficoll-Paque density gradient centrifugation. Preferred effector cells for use in the methods of the invention express different FcyR activating receptors. The invention encompasses, effector cells, THP-1, expressing FcyRI, FcyRIIA and FcyRIIB, and monocyte derived primary macrophages derived from whole human blood expressing both FcyRIIIA and FcyRIIB, to determine if heavy chain antibody mutants show increased ADCC activity and phagocytosis relative to wild type IgGl antibodies. [00225] The human monocyte cell line, THP-1, activates phagocytosis through expression of the high affinity receptor FcyRI and the low affinity receptor FcyRIIA (Flcit et al., 1991, J. Leuk. Biol. 49: 556). THP-1 cells do not constitutively express FcyRIIA or FcyRIIB. Stimulation of these cells with cytokines effects the FcR expression pattern (Pricop et al., 2000 J. Immunol. 166: 531-7). Growth of THP-1 cells in the presence of the cytokine IL4 induces FcyRIIB expression and causes a reduction in FcyRIIA and FcyRI expression. FcyRIIB expression can also be enhanced by increased cell density (Tridandapani et al, 2002, J. Biol Chem. 277: 5082-9). In contrast, it has been reported that IFNy can lead to expression of FcyRIIIA (Pearse et al, 1993 PNAS USA 90: 4314-8). The presence or absence of receptors on the cell surface can be determined by FACS using common methods known to one skilled in the art. Cytokine induced expression of FcyR on the cell surface provides a system to test both activation and inhibition in the presence of FcyRIIB. If THP-1 cells are unable to express the FcyRIIB the invention also encompasses another human monocyte cell line, U937. These cells have been shown to terminally differentiate into macrophages in the presence of IFNy and TNF (Koren et al, 1979, Nature 279:328-331). [00226], FcyR dependent tumor cell killing is mediated by macrophage and NK cells in mouse tumor models (Clynes et al, 1998, PNAS USA 95: 652-656). The invention encompasses the use of elutriated monocytes from donors as effector cells to analyze the efficiency Fc mutants to trigger cell cytotoxicity of target cells in both phagocytosis and ADCC assays. Expression patterns of FcyRI, FcyRIIIA, and FcyRIIB are affected by different growth conditions. FcyR expression from frozen elutriated monocytes, fresh elutriated monocytes, monocytes maintained in 10% FBS, and monocytes cultured in FBS + GM-CSF and or in human scrum may be determined using common methods known to tiiose skilled in the art. For example, cells can be stained with FcyR specific antibodies and analyzed by FACS to determine FcR profiles. Conditions that best mimic macrophage in vivo FcyR expression is then used for the methods of the invention. [00227] In some embodiments, the invention encompasses the use of mouse cells especially when human cells with the right FcyR profiles are unable to be obtained. In some embodiments, the invention encompasses the mouse macrophage cell line RAW264.7(ATCC) which can be transfected with human FcyRIIIA and stable transfectants isolated using methods known in the art, see, e.g., Ralph et al., L Immunol. 119: 950-4). Transfectants can be quantitated for FcyRIIIA expression by FACS analysis using routine experimentation and high expressors can be used in the ADCC assays of the invention. In other embodiments, the invention encompasses isolation of spleen peritoneal macrophage expressing human FcyR from knockout transgenic mice such as those disclosed herein. [00228] Lymphocytes may be harvested from peripheral blood of donors (PBM) using a Ficoll-Paque gradient (Pharmacia). Within the isolated mononuclear population of cells the majority of the ADCC activity occurs via the natural killer cells (NK) containing FcyRIIIA but not FcyRIIB on their surface. Results with these cells indicate the efficacy of the mutants on triggering NK cell ADCC and establish the reagents to test with elutriated monocytes. [00229] Target cells used in the ADCC assays of the invention include, but are not limited to, breast cancer cell lines, e.g., SK-BR-3 with ATCC accession number HTB-30 (see, e.g., Tremp et al, 1976, Cancer Res. 33-41); B-lymphocytes; cells derived from Burkitts lymphoma, e.g., Raji cells with ATCC accession number CCL-86 (see, e.g., Epstein et al, 1965, J. Nail. Cancer Inst. 34: 231-240), and Daudi cells with ATCC accession number CCL-213 (see, e.g., Klein et al, 1968, Cancer Res. 28: 1300-10). The target cells must be recognized by the antigen binding site of the diabody molecule to be assayed. [00230] The ADCC assay is based on the ability of NK cells to mediate cell death via an apoptotic pathway. NK cells mediate cell death in part by FcyRIIIA's recognition of an IgG Fc domain bound to an antigen on a cell surface. The ADCC assays used in accordance with the methods of the invention may be radioactive based assays or fluorescence based assays. The ADCC assay used to characterize the molecules of the invention comprising variant Fc regions comprises labeling target cells, e.g., SK-BR-3, MCF-7, OVCAR3, Raji, Daudi cells, opsonizing target cells with an antibody that recognizes a cell surface receptor on the target cell via its antigen binding site; combining the labeled opsonized target cells and the effector cells at an appropriate ratio, which can be determined by routine experimentation; harvesting the cells; detecting the label in the supernatant of the lysed target cells, using an appropriate detection scheme based on the label used. The target cells may be labeled either with a radioactive label or a fluorescent label, using standard methods known in the art. For example the labels include, but are not limited to, [SICr]Na2Cr04; and the acetoxymethyl ester of the fluorescence enhancing ligand, 2,2':6',2"-terpyridine-6-6"-dicarboxylate (IDA). [00231] In a specific preferred embodiment, a time resolved fluorimetric assay is used for measuring ADCC activity against target cells that have been labeled with the acetoxymethyl ester of the fluorescence enhancing ligand, 2,2':6>,2"-terpvridine-6-6"-dicarboxylate (TDA). Such fluorimetric assays are known in the art, e.g., see, Dlomberg etal, 1996, Journal of Immunological Methods, 193: 199-206; which is incorporated herein by reference in its entirety. Briefly, target cells are labeled with the membrane permeable acetoxymethyl diester of TDA (bis(acetoxymethyl) 2,2':6',2"-terpyridine-6-6"-dicarboxylate, (BATDA), which rapidly diffuses across the cell membrane of viable cells. Intracellular esterases split off the ester groups and the regenerated membrane impermeable TDA molecule is trapped inside the cell. After incubation of effector and target cells, e.g., for at least two hours, up to 3.5 hours, at 37°C, under 5% CC>2, the TDA released from the lysed target cells is chelated with Eu3+ and the fluorescence of the Europium-TDA chelates formed is quantitated in a time-resolved fluorometer (e.g., Victor 1420, Perkin Elmer/Wallace). [00232] In another specific embodiment, the ADCC assay used to characterize the molecules of the invention comprising multiple epitope binding sites and, optionally, an Fc domain (or portion thereof) comprises the following steps: Preferably 4-5x106 target cells (e.g., SK-BR-3, MCF-7, OVCAR3, Raji cells) are labeled with bis(acetoxymethyl) 2,2':6',2"-terpyridine-t-6"-dicarboxylate (DELFIA BATDA Reagent, Perkin Elmer/Wallac). For optimal labeling efficiency, the number of target cells used in the ADCC assay should preferably not exceed 5xl06. BATDA reagent is added to the cells and the mixture is incubated at 37°C preferably under 5% CCh, for at least 30 minutes. The cells are then washed with a physiological buffer, e.g., PBS with 0.125 mM sulfinpyrazole, and media containing 0.125 mM sulfmpyrazole. The labeled target cells are then opsonized (coated) with a molecule of the invention comprising an epitope binding domain specific for FcyRIIA and, optionally, an Fc domain (or portion thereof). In preferred embodiments, the molecule used in the ADCC assay is also specific for a cell surface receptor, a tumor antigen, or a cancer antigen. The diabody molecule of the invetion may specifically bind any cancer or tumor antigen, such as those listed in section 5.6.1. The target cells in the ADCC asstiy are chosen according to the epltope binding sites engineered into the diabody of the invention, such that the diabody binds a cell surface receptor of the target cell specifically. [00233J Target cells are added to effector cells, e.g., PBMC, to produce effectontarget ratios of approximately 1:1, 10:1, 30:1, 50:1, 75:1, or 100:1. The effector and target cells are incubated for at least two hours, up to 3.5 hours, at 37°C, under 5% COz. Cell supcrnatants are harvested and added to an acidic europium solution (e.g., DELFIA Europium Solution, Perkin Elmer/Wallac). The fluorescence of the Europium-TDA chelates formed is quantitated in a time-resolved fluorometer (e.g., Victor 1420, Perkin Elmer/Wallac). Maximal release (MR) and spontaneous release (SR) are determined by incubation of target cells with 1% TX-100 and media alone, respectively. Antibody independent cellular cytotoxicity (AICC) is measured by incubation of target and effector cells in the absence of a test molecule, e.g., diabody of the invention. Each assay is preferably performed in triplicate. The mem percentage specific lysis is calculated as: Experimental release (ADCC) - AICC)/(MR-SR) x 100. [00234] The invention encompasses assays known in the art, and exemplified herein, to characterize the binding of Clq and mediation of complement dependent cytotoxicity (CDC) by molecules of the invention comprising Fc domains (or portions thereof). To determine Clq binding, a Clq binding ELISA may be performed. An exemplary assay may comprise the following: assay plates may be coated overnight at 4C with polypeptide comprising a molecule of the invention or starting polypeptide (control) in coating buffer. The plates may then be washed and blocked. Following washing, an aliquot of human Clq may be added to each well and incubated for 2 hrs at room temperature. Following a further wash, 100 uL of a sheep anti-complement Clq peroxidase conjugated antibody may be added to each well and incubated for 1 hour at room temperature. The plate may again be washed with wash buffer and 100 ul of substrate buffer containing OPD,(O-phenylenediamine dihydrochloride (Sigma)) may be added to each well. The oxidation reaction, observed by the appearance of a yellow color, may be allowed to proceed for 30 minutes and stopped by the addition of 100 ul of 4.5 NH2 SO4. The absorbance may then read at (492-405) nm. [00235] To assess complement activation, a complement dependent cytotoxicity (CDC) assay may be performed, e.g. as described in Gazzano-Santoro et al., J. Immunol. Methods 202:163 (1996), which is incorporated herein by reference in its entirety. Briefly, various concentrations of the molecule comprising a (variant) Fc domain (or portion thereof) and human complement may be diluted with buffer. Cells which express the antigen to which the diabody molecule binds may be diluted to a density of about 1x10 cells/ml. Mixtures of the diabody molecules comprising a (variant) Fc domain (or portion thereof), diluted human complement and cells expressing the antigen may be added to a flat bottom tissue culture 96 well plate and allowed to incubate for 2 hrs at 37C. and 5% C02 to facilitate complement mediated cell lysis. 50 uL of alamar blue (Accumed International) may then be added to each well and incubated overnight at 37 C. The absorbance is measured using a 96-well fluorometer with excitation at 530 mn and emission at 590 run. The results may be expressed in relative fluorescence units (RFU). The sample concentrations may be computed from a standard curve and the percent activity as compared to nonvariant molecule, i.e., a molecule not comprising an Fc domain or comprising anon-variant Fc domain, is reported for the variant of interest. 5.4.3 OTHER ASSAYS [00236] The molecules of the invention comprising multiple epitope binding domain and, optionally, an Fc domain may be assayed using any surface plasmon resonance based assays known in the art for characterizing the kinetic parameters of an antigen-binding domain or Fc-FcyR binding. Any SPR instrument commercially available including, but not limited to, BIAcore Instruments, available from Biacore AB (Uppsala, Sweden); lAsys instruments available from Affinity Sensors (Franklin, MA.); IBIS system available from Windsor Scientific Limited (Berks, UK), SPR-CELLIA systems available from Nippon Laser and Electronics Lab (Hokkaido, Japan), and SPR Detector Spreeta available from Texas Instruments (Dallas, TX) can be used in the instant invention. For a review of SPR- based technology see Mullet et al, 2000, Methods 22: 77-91; Dong et al., 2002, Review in Mol. Biotech, 82: 303-23; Fivash et al, 1998, Current Opinion in Biotechnology 9: 97-101; Rich et al., 2000, Current Opinion in Biotechnology 11: 54-61; all of which are incorporated herein by reference in their entirety. Additionally, any of the SPR instruments and SPR based methods for measuring protein-protein interactions described in U.S. Patent No.'s 6,373,577; 6,289,286; 5,322,798; 5,341,215; 6,268,125 are contemplated in the methods of the invention, all of which are incorporated herein by reference in their entirety. [00237] Briefly, SPR based assays involve immobilizing a member of a binding pan- on a surface, and monitoring its interaction with the other member of the binding pair in solution in real time. SPR is based on measuring the change in refractive index of the solvent near the surface that occurs upon complex formation or dissociation. The surface onto which the immobilization occur is the sensor chip, which is at the heart of the SPR technology; it consists of a glass surface coated with a thin layer of gold and forms the basis for a range of specialized surfaces designed to optimize the binding of a molecule to the surface. A variety of sensor chips are commercially available especially from the companies listed supra, all of which may be used in the methods of the invention. Examples of sensor chips include those available from DIAcore AB, Inc., e.g., Sensor Chip CMS, SA, NTA, and HPA. A molecule of the invention may be immobilized onto the surface of a sensor chip using any of the immobilization methods and chemistries known in the art, including but not limited to, direct covalent coupling via amine groups, direct covalent coupling via sulfhydryl groups, biotin attachment to avidin coated surface, aldehyde coupling to carbohydrate groups, and attachment through the histidine tag with NTA chips. [00238] In some embodiments, the kinetic parameters of the binding of molecules of the invention comprising multiple epitope binding sites and, optionally, and Fc domain, to an antigen or an FcyR may be determined using a BIAcore instrument (e.g., BIAcore instrument 1000, BIAcore Inc., Piscataway, NJ). As discussed supra, see section 5.4.1, any FcyR can be used to assess the binding of the molecules of the invention either where at least one epitope binding site of the diabody molecule immunospecifically recognizes an FcyR, and/or where the diabody molecule comprises an Fc domain (or portion thereof). In a specific embodiment the FcyR is FcyRIIIA, preferably a soluble monomeric FcyRIIIA. For example, in one embodiment, the soluble monomeric FcyRIIIA is the extracellular region of FcyRIIIA joined to the linker-AVITAG sequence (see, U.S. Provisional Application No. 60/439,498, filed on January 9, 2003 (Attorney Docket No. 11183-004-888) and U.S. Provisional Application No. 60/456,041 filed on March 19, 2003, which are incorporated herein by reference in their entireties). In another specific embodiment, the FcyR is FcyRIIB, preferably a soluble dimeric FcyRIlB. For example in one embodiment, the soluble dimeric FcyRIIB protein is prepared in accordance with the methodology described hi U.S. Provisional application No. 60/439,709 filed on January 13, 2003, which is incorporated herein by reference in its entirety. [00239] For all immunological assays, FcyR recognition/binding by a molecule of the invention may be effected by multiple domains: hi certain embodiments, molecules of the invention immunospecifically recognize an FcyR via one of the multiple epitope binding domains; in yet other embodiments, where the molecule of the invetion comprises an Fc domain (or portion thereof), the diabody molecule may immunospecifically recognize an FcyR via Fc-FcyR interactions; in yet further embodiments, where a molecule of the invetion comprises both an Fc domain (or portion thereof) and an epitope binding site that immunospecifically recognizes an FcyR, the diabody molecule may recognize an FcyR via one or both of an epitope binding domain and the Fc domain (or portion thereof). An exemplary assay for determining the kinetic parameters of a molecule comprising multiple epitope binding domains and, optionally, and Fc domain (or portion thereof) to an antigen and/or an FcyR using a BIAcore instrument comprises the following: a first antigen is immobilized on one of the four flow cells of a sensor chip surface, preferably through amine coupling chemistry such that about 5000 response units (RU) of said first antigen is immobilized on the surface. Once a suitable surface is prepared, molecules of the invention that immunospecifically recognize said first antigen are passed over the surface, preferably by one minute injections of a 20 jag/mL solution at a 5 uL/mL flow rate. Levels of molecules of the invention bound to the surface at this stage typically ranges between 400 and 700 RU. Next, dilution series of a second antigen (e.g., FcyR) or FcyR receptor in HBS-P buffer (20mM HEPES, 150 mMNaCl, 3mM EDTA, pH 7.5) are injected onto the surface at 100 uL/min Regeneration of molecules between different second antigen or receptor dilutions is carried out preferably by single 5 second injections of lOOmM NaHCOa pH 9.4; 3M NaCl. Any regeneration technique known in the art is contemplated in the method of the invention. [00240] Once an entire data set is collected, the resulting binding curves are globally fitted using computer algorithms supplied by the SPR instrument manufacturer, e.g., BIAcore, Inc. (Piscataway, NJ). These algorithms calculate both the Kon and Koff, from which the apparent equilibrium binding constant, Kd is deduced as the ratio of the two rate constants (i.e., Kofj/Kon). More detailed treatments of how the individual rate constants are derived can be found in the BIAevaluaion Software Handbook (BIAcore, Inc., Piscataway, NJ). The analysis of the generated data may be done using any method known in the art. For a review of the various methods of interpretation of the kinetic data generated see Myszka, 1997, Current Opinion in Biotechnology 8: 50-7; Fisher et al, 1994, Current Opinion in Biotechnology 5: 389-95; O'Shannessy, 1994, Current Opinion in Biotechnology, 5:65-71; Chaikene/a/., 1992, Analytical Biochemistry, 201: 197-210; Morton etal, 1995, Analytical Biochemistry 227: 176-85; O'Shannessy et al, 1996, Analytical Biochemistry 236: 275-83; all of which are incorporated herein by reference in their entirety. [00241] In preferred embodiments, the kinetic parameters determined using an SPR analysis, e.g., BIAcore, may be used as a predictive measure of how a molecule of the invention will function in a functional assay, e.g., ADCC. An exemplary method for predicting the efficacy of a molecule of the invention based on kinetic parameters obtained from an SPR analysis may comprise the following: determining the Revalues for binding of a molecule of the invention to FcyRIIIA and FcyRIIB (via an epitope binding domain and/or an Fc domain (or portion thereof)); plotting (1) Koff (wt)/Koff (mut) for FcyRIIIA; (2) Koff (mut)/K0ff (wt) for FcyRIIB against the ADCC data. Numbers higher than one show a decreased dissociation rate for FcyRIIIA and an increased dissociation rate for FcyRIIB relative to wild type; and possess and enhanced ADCC function. 5.5 METHODS OF PRODUCING DIABODY MOLECULES OF THE INVENTION [00242] The diabody molecules of the present invention can be produced using a variety of methods well known in the art, including de novo protein synthesis and recornbinant expression of nucleic acids encoding the binding proteins. The desired nucleic acid sequences can be produced by recornbinant methods (e.g., PCR mutagenesis of an earlier prepared variant of the desired polynucleotide) or by solid-phase DNA synthesis. Usually recombinant expression methods are used. In one aspect, the invention provides a polynucleotide that comprises a sequence encoding a CD16A VH and/or VL; in another aspect, the invention provides a polynucleotide that comprises a sequence encoding a CD32B VH and/or VL. Because of the degeneracy of the genetic code, a variety of nucleic acid sequences encode each immunoglobulin amino acid sequence, and the present invention includes all nucleic acids encoding the binding proteins described herein. 5.5.1 POLYNUCLEOTIDES ENCODING MOLECULES OF THE INVENTION. [00243J The present invention also includes polynucleotides that encode the molecules of the invention, including the polypeptides and antibodies. The polynucleotides encoding the molecules of the invention may be obtained, and the nucleotide sequence of the polynucleotides determined, by any method known in the art. [00244] Once the nucleotide sequence of the molecules that are identified by the methods of the invention is determined, the nucleotide sequence may be manipulated using methods well known in the art, e.g., recombinant DNA techniques, site directed mutagenesis, PCR, etc. (see, for example, the techniques described in Sambrook et al., 2001, Molecular Cloning, A Laboratory Manual, 3rd Ed., Cold Spring Harbor Laboratory, Cold Spring Harbor, NY; and Ausubel et al, eds., 1998, Current Protocols in Molecular Biology, John Wiley & Sons, NY, which are both incorporated by reference herein in their entireties), to generate, for example, antibodies having a different amino acid sequence, for example by generating amino acid substitutions, deletions, and/or insertions. K one embodiment, human libraries or any other libraries available in the art, can be screened by standard techniques known in the art, to clone the nucleic acids encoding the molecules of the invention. 5.5.2 RECOMBINANT EXPRESSION OF MOLECULES OF THE INVENTION [00246] Once a nucleic acid sequence encoding molecules of the invention (i.e., antibodies) has been obtained, the vector for the production of the molecules may be produced by recombinant DNA technology using techniques well known in the art. Methods which are well known to those skilled in the art can be used to construct expression vectors containing the coding sequences for the molecules of the invention and appropriate transcriptional and translational control signals. These methods include, for example, in vitro recombinant DNA techniques, synthetic techniques, and in vivo genetic recombination. (See, for example, the techniques described in Sambrook et a!., 1990, Molecular Cloning. A Laboratory, Manual, 2d Ed., Cold Spring Harbor Laboratory, Cold Spring Harbor, NY and Ausubel et al. eds., 1998, Current PrQtocolsJn Molecular Biology. John Wiley & Sons, NY). [00247] An expression vector comprising the nucleotide sequence of a molecule identified by the methods of the invention can be transferred to a host cell by conventional techniques (e.g., electroporation, liposomal transfection, and calcium phosphate precipitation) and the transfected cells are then cultured by conventional techniques to produce the molecules of the invention. In specific embodiments, the expression of the molecules of the invention is regulated by a constitutive, an inducible or a tissue, specific promoter. [00248] The host cells used to express the molecules identified by the methods of the invention may be either bacterial cells such as Escherichia coli, or, preferably, eukaryotic cells, especially for the expression of whole recombinant immunoglobulin molecule. In particular, mammalian cells such as Chinese hamster ovary cells (CHO), in conjunction with a vector such as the major intermediate early gene promoter element from human cytomegalovirus is an effective expression system for immunoglobulins (Foecking et al, 1998, Gene 45:101; Cockett et al, 1990, Bio/Technology 8:2). [00249] A variety of host-expression vector systems may be utilized to express the molecules identified by the methods of the invention. Such host-expression systems represent vehicles by which the coding sequences of the molecules of the invention may be produced and subsequently purified, but also represent cells which may, when transformed or transfected with the appropriate nucleotide coding sequences, express the molecules of the invention in situ. These include, but are not limited to, microorganisms such as bacteria (e.g., E. coll and B. subtilis) transformed withrecombinant bacteriophage DNA, plasmid DNA or cosmid DNA expression vectors containing coding sequences for the molecules identified by the methods of the invention; yeast (e.g., Saccharomyces Pichid) transformed with recombinant yeast expression vectors containing sequences encoding the molecules identified by the methods of the invention; insect cell systems infected with recombinant virus expression vectors (e.g., baclovirus) containing the sequences encoding the molecules identified by the methods of the invention; plant cell systems infected with recombinant virus expression vectors (e.g., cauliflower mosaic virus (CaMV) and tobacco mosaic virus (TMV) or transformed with recombinant plasmid expression vectors (e.g., Ti plasmid) containing sequences encoding the molecules identified by the methods of the invention; or mammalian cell systems (e.g., COS, CHO, BHK, 293,293T, 3T3 cells, lymphotic cells (see U.S. 5,807,715), Per C.6 cells (human retinal cells developed by Crucell) harboring recombinant expression constructs containing promoters derived from the genome of mammalian cells (e.g., metallothionein promoter) or from mammalian viruses (e.g., the adenovirus late promoter; the vaccinia virus 7.5K promoter). [00250] In bacterial systems, a number of expression vectors may be advantageously selected depending upon the use intended for the molecule being expressed. For example, when a large quantity of such a protein is to be produced, for the generation of pharmaceutical compositions of an antibody, vectors which direct the expression of high levels effusion protein products that are readily purified may be desirable. Such vectors include, but are not limited, to the E. coll expression vector pUR278 (Ruther et al., 1983, EMBO J. 2:1791), in which the antibody coding sequence may be ligated individually into the vector in frame with the lac Z coding region so that a fusion protein is produced; pIN vectors (Inouye & Inouye, 1985, Nucleic Acids Res. 13:3101-3109; Van Heeke & Schuster, 1989, J. Biol Chem. 24:5503-5509); and the like. pGEX vectors may also be used to express foreign polypeptides as fusion proteins with glutathione S-transferase (GST). In general, such fusion proteins are soluble and can easily be purified from lysed cells by adsorption and binding to a matrix glutathione-agarose beads followed by elution in the presence of free glutathione. The pGEX vectors are designed to include thrombin or factor Xa protease cleavage sites so that the cloned target gene product can be released from the GST moiety. [00251], In an insect system, Autographa californica nuclear polyhedrosis virus (AcNPV) is used as a vector to express foreign genes. The virus grows in Spodoptera frugiperda cells. The antibody coding sequence may be cloned individually into non- essential regions (e.g., the polyhedrin gene) of the virus and placed under control of an AcNPV promoter (e.g., the polyhedrin promoter). [00252] In mammalian host cells, a number of viral-based expression systems may be utilized. In cases where an adenovirus is used as an expression vector, the antibody coding sequence of interest may be ligated to an adenovirus transcription/translation control complex, e.g., the late promoter and tripartite leader sequence. This chimeric gene may then be inserted in the adenovirus genome by in vitro or in vivo recombination. Insertion in a non-essential region of the viral genome (e.g., region El or E3) will result in a recombinant virus that is viable and capable of expressing the immunoglobulin molecule in infected hosts (e.g., see Logan & Shenk, 1984, Proc. Natl. Acad. Sci. USA 81:355-359). Specific initiation signals may also be required for efficient translation of inserted antibody coding sequences. These signals include the ATG initiation codon and adjacent sequences. Furthermore, the initiation codon must be in phase with the reading frame of the desired coding sequence to ensure translation of the entire insert. These exogenous translational control signals and initiation codons can be of a variety of origins, both natural and synthetic. The efficiency of expression may be enhanced by the inclusion of appropriate transcription enhancer elements, transcription terminators, etc. (see Bittner et al, 1987, Methods in Enzymol. 153:51 -544). [00253] In addition, a host cell strain may be chosen which modulates the expression of the inserted sequences, or modifies and processes the gene product in the specific fashion desired. Such modifications (e.g., glycosylation) and processing (e.g., cleavage) of protein products may be important for the function of the protein. For example, in certain embodiments, the polypeptides comprising a diabody molecule of the invention may be expressed as a single gene product (e.g., as a single polypeptide chain, i.e., as a polyprotein precursor), requiring proteolytic cleavage by native or recombinant cellular mechanisms to form the separate polypeptides of the diabody molecules of the invention. The invention thus encompasses engineering a nucleic acid sequence to encode a polyprotein precursor molecule comprising the polypeptides of the invention, which includes coding sequences capable of directing post translational cleavage of said polyprotein precursor. Post-translational cleavage of the polyprotein precursor results in the polypeptides of the invention. The post translational cleavage of the precursor molecule comprising the polypeptides of the invention may occur in vivo (i.e., within the host cell by native or recombinant cell systems/mechanisms, e.g. furin cleavage at an appropriate site) or may occur in vitro (e.g. incubation of said polypeptide chain in a composition comprising proteases or peptidases of known activity and/or in a composition comprising conditions or 'reagents known to foster the desired proteolytic action). Purification and modification of recombinant proteins is well known in the art such that the design of the polyprotein precursor could include a number of embodiments readily appreciated by a skilled worker. Any known proteases or peptidases known in the art can be used for the described modification of the precursor molecule, e.g., thrombin (which recognizes the amino acid sequence LVPRAQS (SEQ ID NO:91)), or factor Xa (which recognizes the amino acid sequence I(E/D)GRA (SEQ ID NO:92) (Nagani et al., 1985, PNAS USA 82:7252-7255, and reviewed in Jenny et al, 2003, Protein Expr. Purif. 31:1-11, each of which is incorporated by reference herein in its entirety)), enterokinase (which recognizes the amino acid sequence DDDDKA (SEQ ID NO:93) (Collins-Racie et al., 1995, Biotechnol. 13:982-987 hereby incorporated by reference herein in its entirety)), furin (which recognizes the amino acid sequence RXXRA, with a preference for RX(K/R)RA (SEQ ID NO:94 and SEQ ID NO:95, respectively) (additional R at P6 position appears to enhance cleavage)), and AcTEV (which recognizes the amino acid sequence ENLYFQAQ (SEQ ID N0:96) (Parks et al., 1994, Anal. Biochem. 216:413 hereby incorporated by reference herein in its entirety)) and the Foot and Mouth Disease Virus Protease C3. See for example, section 6.4, supra. [00254] Different host cells have characteristic and specific mechanisms for the post- translational processing and modification of proteins and gene products. Appropriate cell lines or host systems can be chosen to ensure the correct modification and processing of the foreign protein expressed. To this end, eukaryotic host cells which possess the cellular machinery for proper processing of the primary transcript, glycosylation, and phosphorylation of the gene product may be used. Such mammalian host cells include but are not limited to CHO, VERY, BHK, Hela, COS, MDCK, 293, 293T, 3T3, WI38, BT483, Hs578T, HTB2, BT20 and T47D, CRL7030 and Hs578Bst. [00255] For long-term, high-yield production of recombinant proteins, stable expression is preferred. For example, cell lines which stably express an antibody of the invention may be engineered. Rather than using expression vectors which contain viral origins of replication, host cells can be transformed with DNA controlled by appropriate expression control elements (e.g., promoter, enhancer, sequences, transcription terminators, polyadenylation sites, etc.}, and a selectable marker. Following the introduction of the foreign DNA, engineered cells may be allowed to grow for 1-2 days in an enriched media, and then are switched to a selective media. The selectable marker in the recombinant plasmid confers resistance to the selection and allows cells to stably integrate the plasmid into their chromosomes and grow to form foci which in turn can be cloned and expanded into cell lines.' 'l/his method may advantageously be used to engineer cell lines which express the antibodies of the invention. Such engineered cell lines may be particularly useful in screening and evaluation of compounds that interact directly or indirectly with the molecules of the invention. [00256] A number of selection systems may be used, including but not limited to the herpes simplex virus thymidine kinase (Wigler et al, 1977, Cell 11: 223), hypoxanthine- guanine phosphoribosyltransferase (Szybalska & Szybalski, 1992, Proc. Natl. Acad. Sci. USA 48:202), and adenine phosphoribosyltransferase (Lowy et al, 1980, Cell 22: 817) genes can be employed in tk-, hgprt- or aprt- cells, respectively. Also, antimetabolite resistance can be used as the basis of selection for the following genes: dhfr, which confers resistance to methotrexate (Wigler etal, 1980, Proc. Natl. Acad. Sci. USA 77:357; O'Hare etal, 1981, Proc. Natl Acad. Sci. USA 78: 1527); gpt, which confers resistance to mycophenolic acid (Mulligan & Berg, 1981, Proc. Natl. Acad. Sci. USA 78: 2072); neo, which confers resistance to the aminoglycoside G-418 Clinical Pharmacy 12: 488-505; Wu and Wu, 1991, 3:87-95; Tolstoshev, 1993, Ann. Rev. Pharmacol. ToxicoL 32:573-596; Mulligan, 1993, Science 260:926-932; and Morgan and Anderson, 1993, Ann, Rev. Biochem. 62:191-217; May, 1993, TIB TECH 11(5): 155-215). Methods commonly known in the art of recombinant DNA technology which can be used are described in Ausubel et al. (eds.), 1993, Current Protocols in Molecular Biology, John Wiley & Sons, NY; Kriegler, . 1990, Gene Transfer and Expression. A Laboratory Manual. Stockton Press, NY; and in Chapters 12 and 13, Dracopoli et al (eds), 1994, Current Protocols in Human Genetics. John Wiley & Sons, NY.; Colberre-GarapineM/., 1981, J. Mol Biol 150:1; andhygro, which confers resistance to hygromycin (Santerre et al, 1984, Gene 30:147). [00257] The expression levels of a molecule'of the invention can be increased by vector amplification (for a review, see Bebbington and Hentschel, The use of vectors based on gene amplification for the expression of cloned genes in mammalian cells in DNA cloning. Vol. 3 (Academic Press, New York, 1987). When a marker in the vector system expressing an antibody is amplifiablc, increase in the level of inhibitor present in culture of host cell will increase the number of copies of the marker gene. Since the amplified region is associated with the nucleotide sequence of a polypeptide of the diabody molecule, production of the polypeptide will also increase (Grouse et al, 1983, Mol Cell Biol 3:257). [00258] The host cell may be co-transfected with two expression vectors of the invention, the first vector encoding the first polypeptide of the diabody molecule and the second vector encoding the second polypeptide of the diabody molecule. The two vectors may contain identical selectable markers which enable equal expression of both polypeptides. Alternatively, a single vector may be used which encodes both polypeptides. The coding sequences for the polypeptides of the molecules of the invention may comprise cDNA or genomic DNA. [00259] Once a molecule of the invention (i. e., diabodies) has been recombinantly expressed, it may be purified by any method known in the art for purification of polypeptides, polyproteins or diabodies (e.g., analogous to antibody purification schemes based on antigen selectivity) for example, by chromatography (e.g., ion exchange, affinity, particularly by affinity for the specific antigen (optionally after Protein A selection where the diabody molecule comprises an Fc domain (or portion thereof)), and sizing column chromatography), centrifugation, differential solubility, or by any other standard technique for the purification of polypeptides, polyproteins or diabodies. 5.6 PROPHYLACTIC AND THERAPEUTIC METHODS [00260] The molecules of the invention are particularly useful for the treatment and/or prevention of a disease, disorder or infection where an effector cell function (e.g., ADCC) mediated by FcyR is desired (e.g., cancer, infectious disease). As discussed supra, the diabodies of the invetion may exhibit antibody-like functionality in eliciting effector function although the diabody molecule does not comprise and Fc domain. By comprising at least one epitope binding domain that immunospecifically recognizes an FcyR, the diabody molecule may exibit FcyR binding and activity analogous to Fc-FcyR interactions. For example, molecules of the invention may bind a cell surface antigen and an FcyR (e.g., FcyRIIIA) on an immune effector cell (e.g., NK cell), stimulating an effector function (e.g., ADCC, CDC, phagocytosis, opsonization, etc.) against said cell. [00261] In other embodiments, the diabody molecule of the invention comprises an Fc domain (or portion thereof). In such embodiments, the Fc domain may further comprise at least one amino acid modification relative to a wild-type Fc domain (or portion thereof) and/or may comprise domains from one or more IgG isotypes (e.g., IgGl, IgG2, IgG3 or IgG4). Molecules of the invetion comprising variant Fc domains may exhibit conferred or altered phenotypes relative to molecules comprising the wild type Fc domain such as an altered or conferred effector function activity (e.g., as assayed in an NK dependent or macrophage dependent assay). In said embodiments, molecules of the invention with conferred or altered effector function activity are useful for the treatment and/or prevention of a disease, disorder or infection where an enhanced efficacy of effector function activity is desired. In certain embodiments, the diabody molecules of the invention comprising an Fc domain (or portion thereof) mediate complement dependent cascade. Fc domain variants identified as altering effector function are disclosed in International Application WO04/063351, U.S. Patent Application Publications 2005/0037000 and 2005/0064514, U.S. Provisional Applications 60/626,510, filed November 10,2004, 60/636,663, filed December 15,2004, and 60/781,564, filed March 10,2006, and U.S. Patent Applications 11/271,140, filed November 10,2005, and 11/305,787, filed December 15, 2005, concurrent applications of the Inventors, each of which is incorporated by reference in its entirety. [00262] The invention encompasses methods and compositions for treatment, prevention or management of a cancer in a subject, comprising administering to the subject a therapeutically effective amount of one or more molecules comprising one or more epitope binding sites, and optionally, an Fc domain (or portion thereof) engineered in accordance with the invention, which molecule further binds a cancer antigen. Molecules of the invention are particularly useful for the prevention, inhibition, reduction of growth or regression of primary tumors, metastasis of cancer cells, and infectious diseases. Although not intending to be bound by a particular mechanism of action, molecules of the invention mediate effector function resulting in tumor clearance, tumor reduction or a combination thereof. In alternate embodiments, the diabodies of the invention mediate therapeutic activity by cross-linking of cell surface antigens and/or receptors and enhanced apoptosis or negative growth regulatory signaling. [00263] Although not intending to be bound by a particular mechanism of action, the diabody molecules of the invention exhibit enhanced therapeutic efficacy relative to therapeutic antibodies known in the art, in part, due to the ability of diabody to immunospecifically bind a target cell which expresses a particular antigen (e.g., FcyR) at reduced levels, for example, by virtue of the ability of the diabody to remain on the target cell longer due to an improved avidity of the diabody-cpitopc interaction. [00264] The diabodies of the invention with enhanced affinity and avidity for antigens (e.g., FcyRs) are particularly useful for the treatment, prevention or management of a cancer, or another disease or disorder, in a subject, wherein the Fc7Rs are expressed at low levels in the target cell populations. As used herein, FcyR expression in cells is defined in terms of the density of such molecules per cell as measured using common methods known to those skilled in the art. The molecules of the invention comprising multiple epitope binding sites and, optionally, and FcyR (or portion thereof) preferably also have a conferred or an enhanced avidity and affinity and/or effector function in cells which express a target antigen, e.g., a cancer antigen, at a density of 30,000 to 20,000 molecules/cell, at a density of 20,000 to 10,000 molecules/cell, at a density of 10,000 molecules/cell or less, at a density of 5000 molecules/cell or less, or at a density of 1000 molecules /cell or less. The molecules of the invention have particular utility in treatment, prevention or management of a disease or disorder, such as cancer, in a sub-population, wherein the target antigen is expressed at low levels in the target cell population. [00265] The molecules of the invention may also be advantageously utilized in combination with other therapeutic agents known in the art for the treatment or prevention of diseases, such as cancer, autoimmune disease, inflammatory disorders, and infectious diseases. In a specific embodiment, molecules of the invention may be used in combination with monoclonal or chimeric antibodies, lymphokines, or hematopoietic growth factors (such as, e.g., IL-2, IL-3 and IL-7), which, for example, serve to increase the number or activity of effector cells which interact with the molecules and, increase immune response. The molecules of the invention may also be advantageously utilized in combination with one or more drugs used to treat a disease, disorder, or infection such as, for example anti-cancer agents, anti-inflammatory agents or anti-viral agents, e.g., as detailed in Section 5.7. 5.6.1 CANCERS [00266] The invention encompasses methods and compositions for treatment or prevention of cancer in a subject comprising administering to the subject a therapeutically effective amount of one or more molecules comprising multiple epitope binding domains. In some embodiments, the invention encompasses methods and compositions for the treatment or prevention of cancer in a subject with FcyR polymorphisms such as those homozygous for the FyRIIIA-158V or FcyRIIIA-158F alleles. hi some embodiments, the invention encompasses engineering at least one epitope binding domain of the diabody molecule to immunospecifically bind FcyRIIIA (158F). In other embodiments, the invention encompasses engineering at least one epitope binding domain of the diabody molecule to immunospecifically bind FcyRIIIA (158V). [00267] The efficacy of standard monoclonal antibody therapy depends on the FcyR polymorphism of the subject (Carton etal., 2002 Blood, 99:'754-8; Weng etal, 2003 JClin engineered to comprise a variant Fc domain that exhibits enhanced affinity to FcyR (relative to a wild type Fc domain) on effector cells. The engineered molecules of the invention provide better immunotherapy reagents for patients regardless of their FcyR polymorphism. [00268] Diabody molecules engineered in accordance with the invention are tested by ADCC using either a cultured cell line or patient derived PMBC cells to determine the ability of the Fc mutations to enhance ADCC. Standard ADCC is performed using methods disclosed herein. Lymphocytes are harvested from peripheral blood using a Ficoll-Paque gradient (Pharmacia). Target cells, i.e., cultured cell lines or patient derived cells, are loaded with Europium (PerkinElmer) and incubated with effectors for 4 hrs at 37°C. Released Europium is detected using a fluorescent plate reader (Wallac). The resulting ADCC data indicates the efficacy of the molecules of the invention to trigger NK cell mediated cytotoxicity and establish which molecules can be tested with both patient samples and elutriated monocytes. Diabody molecules showing the greatest potential for eliciting ADCC activity are then tested in an ADCC assay using PBMCs from patients. PBMC from healthy donors are used as effector cells. [00269] Accordingly, the invention provides methods of preventing or treating cancer characterized by a cancer antigen by engineering the diabody molecule to immunospecifically recognize said cancer antigen such that the diabody molecule is itself cytotoxic (e.g., via crosslinking of surface receptors leading to increased apoptosis or downregulation of proliferative signals) and/or comprises an Fc domain, according to the invention, and/or mediates one or more effector function (e.g., ADCC, phagocytosis). The diabodies that have been engineered according to the invention are useful for prevention or treatment of cancer, since they have an cytotoxic activity (e.g., enhanced tumor cell killing and/or enhanced for example, ADCC activity or CDC activity). [00270] Cancers associated with a cancer antigen may be treated or prevented by administration of a diabody that binds a cancer antigen and is cytotoxic, and/or has been engineered according to the methods of the invention to exhibit effector function. For example, but not by way of limitation, cancers associated with the following cancer antigens may be treated or prevented by the methods and compositions of the invention: KS 1/4 pan-carcinoma antigen (Perez and Walker, 1990, J. Immunol. 142:32-37; Bumal, 1988, Hybridoma 7(4):407-415), ovarian carcinoma antigen (CA125) (Yu et at, 1991, Cancer Res. 51(2):48-475), prostatic acid phosphate (Tailor et al, 1990, Nucl. Acids Res. 18(1):4928), prostate specific antigen (Henttu and Vihko, 1989, Biochem. Diophys. Res. Comm. 10(2):903-910; Israeli etal, 1993, Cancer Res. 53:227-230), melanoma-associated antigen p97(Estin era/., l9S9,J.Natl. Cancer Instit. 81(6):445-44), melanoma antigen gp75 (Vijayasardahl et a/.,'l990, J. Exp. Med. 171(4):1375-1380), high molecular weight melanoma antigen (HMW-MAA) (Natali et al, 1987, Cancer 59:55-3; Mittelman et al, 1990, J. Clin. Invest. 86:2136-2144)), prostate specific membrane antigen, carcinoembryonic antigen (CEA) (Foon et al, 1994, Proc. Am. Soc. Clin. Oncol 13:294), polymorphic epithelial mucin antigen, human milk fat globule antigen, Colorectal tumor-associated antigens such as: CEA, TAG-72 (Yokata et al, 1992, Cancer Res. 52:3402-3408), CO17-1A (Ragnhammar etal., 1993, Int. J. Cancer 53:751-758); GIGA 19-9 (Herlynef a/., 1982, J. Clin. Immunol. 2:135), CTA-1 and LEA, Burkitt's lymphoma antigen-38.13, CD19 (Ghetie etal, 1994, Blood 83:1329-1336), humanB-lymphoma antigen-CD20 (Reff et al, 1994, Blood 83:435-445), CD33 (Sgouros et al, 1993, J. Nucl. Med. 34:422-430), melanoma specific antigens such as ganglioside GD2 (Saleh et al, 1993, J-Immunol., 151, 3390-3398), ganglioside GD3 (Shitaraera/., 1993, Cancer Immunol. Immunother. 36:373-380), ganglioside GM2 (Livingstone/al, 1994, J. Clin. Oncol 12:1036-1044), ganglioside GM3 (Eoonetal., 1993, Cancer Res. 53:5244-5250), tumor-specific transplantation type of cell-surface antigen (TSTA) such as virally-induced tumor antigens including T-antigen DNA tumor viruses and envelope antigens of RNA tumor viruses, oncofetal antigen-alpha-fetoprotein such as CEA of colon, bladder tumor oncofetal antigen (Hellstrom et al, 1985, Cancer. Res. 45:2210-2188), differentiation antigen such as human lung carcinoma antigen L6, L20 (Hellstrom et al., 1986, Cancer Res. 46:3917-3923), antigens of fibrosarcoma, human leukemia T cell antigen-Gp37 (Bhattacharya-Chatterjee et al, 1988, J. oflmmun. 141:1398-1403), neoglycoprotein, sphingolipids, breast cancer antigen such as EGFR (Epidermal growth factor receptor), HER2 antigen (plSS™1*2), polymorphic epithelial mucin (PEM) (Hilkens et al, 1992, Trends in Bio. Chem. Sci. 17:359), malignant human lymphocyte antigen-APO-1 (Bernhard et al, 1989, Science 245:301-304), differentiation antigen (Feizi, 1985, Nature 314:53-57) such as I antigen found in fetal erthrocytes and primary endoderm, I(Ma) found in gastric adenocarcinomas, Ml 8 and M39 found in breast epithelium, SSEA-1 found in myeloid cells, VEP8, VEP9, Myl, VIM-D5,and Dj56-22 found in colorectal cancer, TRA-1-85 (blood group H), C14 found in colonic adenocarcinoma, F3 found in lung adenocarcinoma, AH6 found hi gastric cancer, Y hapten, Le* found in embryonal carcinoma cells, TL5 (blood group A), EGF receptor found in A431 cells , EI scries (blood group B) found in pancreatic cancer, FC10.2 found in embryonal carcinoma cells, gastric adenocarcinoma, CO-514 (blood group Lea) found in adenocarcinoma, NS-10 found in adenocarcinomas, CO-43 (blood group Leb), G49, EGF receptor, (blood group ALeb/Ley) found in colonic adenocarcinoma, 19.9 found in colon cancer, gastric cancer mucins, TsA? found in myeloid cells, R24 found in melanoma, 4.2, GD3, Dl.l, OFA-1, GM2, OFA-2, GD2, M 1:22:25:8 found in embryonal carcinoma cells and SSEA-3, SSEA-4 found in 4-8-ccll stage embryos. In another embodiment, the antigen is a T cell receptor derived peptide from a cutaneous T cell lymphoma (see Edelson, 1998, The Cancer Journal 4:62). [00271] Cancers and related disorders that can be treated or prevented by methods and compositions of the present invention include, but are not limited to, the following: Leukemias including, but not limited to, acute leukemia, acute lymphocytic leukemia, acute myelocytic leukemias such as myeloblastic, promyelocytic, myelomonocytic, monocytic, erythroleukemia leukemias and myelodysplastic syndrome, chronic leukemias such as but not limited to, chronic myelocytic (granulocytic) leukemia, chronic lymphocytic leukemia, hairy cell leukemia; polycythemia vera; lymphomas such as but not limited to Hodgkin's disease, non-Hodgkin's disease; multiple myelomas such as but not limited to smoldering multiple myeloma, nonsecretory myeloma, osteosclerotic myeloma, plasma cell leukemia, solitary plasmacytoma and extramedullary plasmacytoma; WaldenstrcJm's macroglobulinemia; monoclonal gammopathy of undetermined significance; benign monoclonal gammopathy; heavy chain disease; bone and connective tissue sarcomas such as but not limited to bone sarcoma, osteosarcoma, chondrosarcoma, Swing's sarcoma, malignant giant cell tumor, fibrosarcoma of bone, chordoma, pcriosteal sarcoma, soft-tissue sarcomas, angiosarcorna (hemangiosarcoma), fibrosarcoma, Kaposi's sarcoma, leiomyosarcoma, liposarcoma, lymphangiosarcoma, neurilemmoma, rhabdomyosarcoma, synovial sarcoma; brain tumors including but not limited to, glioma, astrocytoma, brain stem glioma, ependymoma, oligodendroglioma, nonglial tumor, acoustic ncurinoma, craniopharyngioma, medulloblastoma, meningioma, pineocytoma, pineoblastoma, primary brain lymphoma; breast cancer including, but not limited to, adenocarcinoma, lobular (small cell) carcinoma, intraductal carcinoma, medullary breast cancer, mucinous breast cancer, tubular breast cancer, papillary breast cancer, Paget's disease, and inflammatory breast cancer; adrenal cancer, including but not limited to, pheochromocytom and adrenocortical carcinoma; thyroid cancer such as but not limited to papillary or follicular thyroid cancer, medullary thyroid cancer and anaplastic thyroid cancer; pancreatic cancer, including but not limited to, insulinoma, gastrinoma} glucagonoma, vipoma, somatostatin-secreting tumor, and carcinoid or islet cell tumor; pituitary cancers including but not limited to, Gushing's disease, prolactin-secreting tumor, acromegaly, and diabetes insipius; eye cancers including but not limited to, ocular melanoma such as iris melanoma, choroidal melanoma, and cilJiary body melanoma, and retinoblastoma; vaginal cancers, including but not limited to, squamous cell carcinoma, adenocarcinoma, and melanoma; vulvar cancer, including but not limited to, squamous cell carcinoma, melanoma, adenocarcinoma, basal cell carcinoma, sarcoma, and Paget's disease; cervical cancers including but not limited to, squamous cell carcinoma, and adenocarcinoma; uterine cancers including but not limited to, endometrial carcinoma and uterine sarcoma; ovarian cancers including but not limited to, ovarian epithelial carcinoma, borderline tumor, germ cell tumor, and stromal tumor; esophageal cancers including but not limited to, squamous cancer, adenocarcinoma, adenoid cyctic carcinoma, mucoepidermoid carcinoma, adenosquamous carcinoma, sarcoma, melanoma, plasmacytoma, verrucous carcinoma, and oat cell (small cell) carcinoma; stomach cancers including but not limited to, adenocarcinoma, fungating (polypoid), ulcerating, superficial spreading, diffusely spreading, malignant lymphoma, liposarcoma, fibrosarcoma, and carcinosarcoma; colon cancers; rectal cancers; liver cancers including but not limited to hepatocellular carcinoma and hepatoblastoma, gallbladder cancers including but not limited to, adenocarcinoma; cholangiocarcinomas including but not limited to, pappillary, nodular, and diffuse; lung cancers including but not limited to, non-small cell lung cancer, squamous cell carcinoma (epidermoid carcinoma), adenocarcinoma, large-cell carcinoma and small-cell lung cancer; testicular cancers including but not limited to, germinal tumor, seminoma, anaplastic, classic (typical), spermatocytic, nonseminoma, embryonal carcinoma, teratoma carcinoma, choriocarcinoma (yolk-sac tumor), prostate cancers including but not limited to, adenocarcinoma, leiomyosarcoma, and rhabdomyosarcoma; penal cancers; oral cancers including but not limited to, squamous cell carcinoma; basal cancers; salivary gland cancers including but not limited to, adenocarcinoma, mucoepidermoid carcinoma, and adenoidcystic carcinoma; pharynx cancers including but not limited to, squamous cell cancer, and verrucous; skin cancers including but not limited to, basal cell carcinoma, squamous cell carcinoma and melanoma, superficial spreading melanoma, nodular melanoma, lentigo malignant melanoma, acral lentiginous melanoma; kidney cancers including but not limited to, renal cell cancer, adenocarcinoma, hypernephroma, fibrosarcoma, transitional cell cancer (renal pelvis and/ or uterer); Wilms' tumor; bladder cancers including but not limited to, transitional cell carcinoma, squamous cell cancer, adenocarcinoma, carcinosarcoma. In addition, cancers include myxosarcoma, osteogenic sarcoma, endotheliosarcoma, lymphangioendotheliosarcoma, mesothelioma, synovioma, hemangioblastoma, epithelial carcinoma, cystadenocarcinoma, bronchogenic carcinoma, sweat gland carcinoma, sebaceous gland carcinoma, papillary carcinoma and papillary adenocarcinomas (for a review of such disorders, see Fishman et al, 1985, Medicine, 2d Ed,, J.B. Lippincott Co., Philadelphia and Murphy et al., 1997, Informed Decisions: The Complete Book of Cancer Diagnosis, Treatment, and Recovery, Viking Penguin, Penguin Books U.S.A., Inc., United States of America). [00272] Accordingly, the methods and compositions of the invention are also useful in the treatment or prevention of a variety of cancers or other abnormal proliferative diseases, including (but not limited to) the following: carcinoma, including that of the bladder, breast, colon, kidney, liver, lung, ovary, pancreas, stomach, prostate, cervix, thyroid and skin; including squamous cell carcinoma; hematopoietic tumors of lymphoid lineage, including leukemia, acute lymphocytic leukemia, acute lymphoblastic leukemia, B-cell lymphoma, T-cell lymphoma, Burketts lymphoma; hematopoietic tumors of myeloid lineage, including acute and chronic myelogenous leukemias and promyelocytic leukemia; tumors of mesenchymal origin, including fibrosarcoma and rhabdomyoscarcoma; other tumors, including melanoma, seminoma, tetratocarcinoma, neuroblastoma and glioma; tumors of the central and peripheral nervous system, including astrocytoma, neuroblastoma, glioma, and schwannomas; tumors of mesenchymal origin, including fibrosafcoma, rhabdomyoscarama, and osteosarcoma; and other tumors, including melanoma, xenoderma pegmentosum, keratoactanthoma, seminoma, thyroid follicular cancer and teratocarcinoma. It is also contemplated that cancers caused by aberrations in apoptosis would also be treated by the methods and compositions of the invention. Such cancers may include but not be limited to follicular lymphomas, carcinomas with p53 mutations, hormone dependent tumors of the breast, prostate and ovary, and precancerous lesions such as familial adenomatous polyposis, and myelodysplastic syndromes. In specific embodiments, malignancy or dysproliferative changes (such as metaplasias and dysplasias), or hyperproliferative disorders, are treated or prevented by the methods and compositions of the invention in the ovary, bladder, breast, colon, lung, skin, pancreas, or uterus. In other specific embodiments, sarcoma, melanoma, or leukemia is treated or prevented by the methods and compositions of the invention. [00273] In a specific embodiment, a molecule of the invention (e.g., a diabody comprising multiple epitope binding domains and, optionally, and Fc domain (or portion thereof)) inhibits or reduces the growth of cancer cells by at least 99%, at least 95%, at least 90%, at least 85%, at least 80%, at least 75%, at least 70%, at least 60%, at least 50%, at least 45%, at least 40%, at least 45%, at least 35%, at least 30%, at least 25%, at least 20%, or at least 10% relative to the growth of cancer cells in the absence of said molecule of the invention. [00274] In a specific embodiment, a molecule of the invention (e.g., a diabody comprising multiple epitope binding domains and, optionally, and Fc domain (or portion thereoFjyiciils cells or inhibits or reduces the growth of cancer cells at least 5%, at least 10%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 60%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 100% better than the parent molecule. 5.6.2 AUTOIMMUNE DISEASE AND INFLAMMATORY DISEASES [00275] In some embodiments, molecules of the invention comprise an epitope binding domain specific for FcyRIIB and or/ a variant Fc domain (or portion thereof), engineered according to methods of the invention, which Fc domain exhibits greater affinity for FcyRIIB and decreased affinity for FcyRIIIA and/or FcyRIIA relative to a wild-type Fc domain. Molecules of the invention with such binding characteristics are useful in regulating the immune response, e.g., in inhibiting the immune response in connection with autoimmune diseases or inflammatory diseases. Although not intending to be bound by any mechanism of action, molecules of the invention with an affinity for Fey RUB and/or comprising an Fc domain with increased affinity for FcyRIIB and a decreased affinity for FcyRIIIA and/or FcyRIIA may lead to dampening of the activating response to FcyR and inhibition of cellular responsiveness, and thus have therapeutic efficacy for treating and/or preventing an autoimmune disorder. [00276] The invention also provides methods for preventing, treating, or managing one or more symptoms associated with an inflammatory disorder in a subject further comprising, administering to said subject a therapeutically or prophylactically effective amount of one or more anti-inflammatory agents. The invention also provides methods for preventing, treating, or managing one or more symptoms associated with an autoimmune disease further comprising, administering to said subject a therapeutically or prophylactically effective amount of one or more immunomodulatory agents. Section 5.7 provides non-limiting examples of anti-inflammatory agents and immunomodulatory agents. [00277] Examples of autoimmune disorders that may be treated by administering the molecules of the present invention include, but are not limited to, alopecia areata, ankylosing spondylitis, antiphospholipid syndrome, autoimmune Addison's disease, autoimmune diseases of the adrenal gland, autoimmune hemolytic anemia, autoimmune hepatitis, autoimmune oophoritis and orchitis, autoimmune thrombocytopenia, Behcet's disease, bullous pemphigoid, cardiomyopathy, celiac sprue-dermatitis, chronic fatigue immune dysfunction syndrome (CFIDS), chronic inflammatory demyelinating polyneuropathy, Churg-Strauss syndrome, cicatrical pemphigoid, CREST syndrome, cold agglutinin disease, Crohn's disease, discoid lupus, essential mixed cryoglobulinemia, fibromyalgia-fibromyositis, glomerulonephritis, Graves' disease, Guillain-Barre, Hashimoto's thyroiditis, idiopathic pulmonary fibrosis, idiopathic thrombocytopenia purpura (ITP), IgA neuropathy, juvenile arthritis, lichen planus, lupus erthematosus, Meniere's disease, mixed connective tissue disease, multiple sclerosis, type 1 or immune- mediated diabetes mellitus, myasthenia gravis, pemphigus vulgaris, pernicious anemia, polyarteritis nodosa, polychrondritis, polyglandular syndromes, polymyalgia rheumatica, polymyositis and dermatomyositis, primary agammaglobulinernia, primary biliary cirrhosis, psoriasis, psoriatic arthritis, Raynauld's phenomenon, Reiter's syndrome, Rheumatoid arthritis, sarcoidosis, scleroderma, Sjb'gren's syndrome, stiff-man syndrome, systemic lupus erythematosus, lupus erythematosus, takayasu arteritis, temporal arteristis/ giant cell arteritis, ulcerative colitis, uveitis, vasculitides such as dermatitis herpetiformis vasculitis, vitiligo, and Wegener's granulomatosis. Examples of inflammatory disorders include, but are not limited to, asthma, encephilitis, inflammatory bowel disease, chronic obstructive pulmonary disease (COPD), allergic disorders, septic shock, pulmonary fibrosis, undifferentitated spondyloarthropathy, undiffcrentiated arthropathy, arthritis, inflammatory osteolysis, and chronic inflammation resulting from chronic viral or bacteria infections. As described herein in Section 2.2.2, some autoimmune disorders are associated with an inflammatory condition. Thus, there is overlap between what is considered an autoimmune disorder and an inflammatory disorder. Therefore, some autoimmune disorders may also be characterized as inflammatory disorders. Examples of inflammatory disorders which can be prevented, treated or managed in accordance with the methods of the invention include, but are not limited to, asthma, encephilitis, inflammatory bowel disease, chronic obstructive pulmonary disease (COPD), allergic disorders, septic shock, pulmonary fibrosis, undifferentitated spondyloarthropathy, undifferentiated arthropathy, arthritis, inflammatory osteolysis, and chronic inflammation resulting from chronic viral or bacteria infections. [00278] Molecules of the invention comprising at least one epitope binding domain specific for FcyRIIB and/or a variant Fc domain with an enhanced affinity for FcyRIIB and a decreased affinity for FcyRIIIA can also be used to reduce the inflammation experienced by animals, particularly mammals, with inflammatory disorders. In a specific embodiment, a molecule of the invention reduces the inflammation in an animal by at least 99%, at least 95%, at least 90%, at least 85%, at least 80%, at least 75%, at least 70%, at least 60%, at least 50%, at least 45%, at least 40%, at least 45%, at least 35%, at least 30%, at least 25%, at least 20%, or at least 10% relative to the inflammation in an animal, which is not administered the said molecule. " [00279] Molecules of the invention comprising at least one epitope binding domain specific for FcyRUB and/or a variant Fc domain with an enhanced affinity for FcyRIIB and a decreased affinity for FcyRIIIA can also be used to prevent the rejection of transplants. 5.6.3 INFECTIOUS DISEASE [00280] The invention also encompasses methods for treating or preventing an infectious disease in a subject comprising administering a therapeutically or prophylatically effective amount of one or more molecules of the invention comprising at least one epitope binding domain specific for an infectious agent associated with said infectious disease. In certain embodiments, the molecules of the invention are toxic to the infectious agent, enhance immune response against said agent or enhance effector function against said agent, relative to the immune response in the absence of said molecule. Infectious diseases that can be treated or prevented by the molecules of the invention are caused by infectious agents including but not limited to viruses, bacteria, fungi, protozae, and viruses. [00281] Viral diseases that can be treated or prevented using the molecules of the invention in conjunction with the methods of the present invention include, but are not limited to, those caused by hepatitis type A, hepatitis type B, hepatitis type C, influenza, varicella, adenovirus, herpes simplex type I (HSV-I), herpes simplex type II (HSV-E), rinderpest, rhinovirus, echovirus, rotavirus, respiratory syncytial virus, papilloma virus, papova virus, cytomegalovirus, echinovirus, arbovirus, huntavirus, coxsackie virus, mumps virus, measles vims, rubella virus, polio virus, small pox, Epstein Barr virus, human immunodeficiency virus type I (HIV-I), human immunodeficiency virus type n (HIV-II), and agents of viral diseases such as viral miningitis, encephalitis, dengue or small pox. [00282] Bacterial diseases that can be treated or prevented using the molecules of the invention in conjunction with the methods of the present invention, that are caused by bacteria include, but are not limited to, mycobacteria rickettsia, mycoplasma, neisseria, S, pneumonia, Borrelia burgdorferi (Lyrne disease), Bacillus antracis (anthrax), tetanus, streptococcus, staphylococcus, mycobacterium, tetanus, pertissus, cholera, plague, diptheria, chlamydia, S. aureus and legionella. [00283] Protozoal diseases that can be treated or prevented using the molecules of the invention in conjunction with the methods of the present invention, that are caused by protozoa include, but are not limited to, leishmania, kokzidioa, trypanosoma or malaria. [00284] Parasitic diseases that can be treated or prevented using the molecules of the invention in conjunction with the methods of the present invention, that are caused by parasites include, but are not limited to, chlamydia and rickettsia. ' [UU285] "According to one aspect of the invention, molecules of the invention comprising at least one epitope binding domain specific for an infectious agent exhibit an antibody effector function towards said agent, e.g., a pathogenic protein. Examples of infectious agents include but are not limited to bacteria (e.g., Escherichia coll, Klebsidla pneumoniae, Staphylococcus aureus, Enterococcusfaecials, Candida albicans, Proteus vulgaris, Staphylococcus viridans, and Pseudomonas aeruginosa), a pathogen (e.g., B-lymphotropic papovavirus (LPV); Bordatella pertussis; Borna Disease virus (BDV); Bovine coronavirus; Choriomeningitis virus; Dengue virus; a virus, E. coli; Ebola; Echovirus 1; Echovirus-11 (EV); Endotoxin (LPS); Enteric bacteria; Enteric Orphan vims; Enteroviruses ; Feline leukemia virus; Foot and mouth disease virus; Gibbon ape leukemia virus (GALV); Gram-negative bacteria; Heliobacter pylori; Hepatitis B virus (HBV); Herpes Simplex Virus; HTV-1; Human cytomegalovirus; Human coronovirus; Influenza A, B & C ; Legionella; Leishmania mexicana; Listeria monocytogenes; Measles virus; Meningococcus; Morbilliviruses; Mouse hepatitis virus; Murine leukemia virus; Murine gamma herpes virus; Murine retrovirus; Murine coronavirus mouse hepatitis virus; Mycobacterium avium-M; Neisseria gonorrhoeae; Newcastle disease virus; Parvovirus B19; Plasmodium falciparurn; Pox Virus; Pseudomonas; Rotavirus; Samonella typhiurium; Shigella; Streptococci; T-cell lymphotropic virus 1; Vaccinia virus). 5.6.4 DETOXIFICATION [00286] The invention also encompasses methods of detoxification in a subject exposed to a toxin (e.g., a toxic drug molecule) comprising administering a therapeutically or prophylatically effective amount of one or more molecules of the invention comprising at least one epitope binding domain specific for the toxic drug molecule. In certain embodiments, binding of a molecule of the invention to the toxin reduces or eliminates the adverse physiological effect of said toxin. In yet other embodiments, binding of a diabody of the invention to the toxin increases or enhances elimination, degradation or neutralization of the toxin relative to elimination, degradation or neutralization in the absence of said diabody. Immunotoxicothcrapy in accordance with the methods of the invention can be used to treat overdoses or exposure to drugs including, but not limited to, digixin, PCP, cocaine, colchicine, and tricyclic antideprcssants. 5.7 COMBINATION THERAPY [00287] The invention further encompasses administering the molecules of the invention in combination with other therapies known to those skilled in the ait for the treatment or prevention of cancer, autoimmune disease, infectious disease or intoxication, including but not limited to, current standard and experimental chemotherapies, hormonal therapies, biological therapies, immunotherapies, radiation therapies, or surgery, hi some embodiments, the molecules of the invention may be administered in combination with a therapeutically or prophylactically effective amount of one or more agents, therapeutic antibodies or other agents known to those skilled in the art for the treatment and/or prevention of cancer, autoimmune disease, infectious disease or intoxication. [00288] In certain embodiments, one or more molecule of the invention is administered to a mammal, preferably a human, concurrently with one or more other therapeutic agents useful for the treatment of cancer. The term "concurrently" is not limited to the administration of prophylactic or therapeutic agents at exactly the same tune, but rather it is meant that a molecule of the invention and the other agent are administered to a mammal in a sequence and within a time interval such that the molecule of the invention can act together with the other agent to provide an increased benefit than if they were administered otherwise. For example, each prophylactic or therapeutic agent (e.g., chemotherapy, radiation therapy, hormonal therapy or biological therapy) may be administered at the same time or sequentially in any order at different points in tune; however, if not administered at the same time, they should be administered sufficiently close in time so as to provide the desired therapeutic or prophylactic effect. Each therapeutic agent can be administered separately, in any appropriate form and by any suitable route, hi various embodiments, the prophylactic or therapeutic agents are administered less than 1 hour apart, at about 1 hour apart, at about 1 hour to about 2 hours apart, at about 2 hours to about 3 hours apart, at about 3 hours to about 4 hours apart, at about 4 hours to about 5 hours apart, at about 5 hours to about 6 hours apart, at about 6 hours to about 7 hours apart, at about 7 hours to about 8 hours apart, at about 8 hours to about 9 hours apart, at about 9 hours to about 10 hours apart, at about 10 hours to about 11 hours apart, at about 11 hours to about 12 hours apart, no more than 24 hours apart or no more than 48 hours apart. In preferred embodiments, two or more components are administered within the same patient visit. [00289] hi other embodiments, the prophylactic or therapeutic agents are administered at about 2 to 4 days apart, at about 4 to 6 days apart, at about 1 week part, at about 1 to 2 weeks apart, or more than 2 weeks apart. In preferred embodiments, the prophylactic or therapeutic agents are administered in a time frame where both agents are still active. One skilled in the art would be able to determine such a tune frame by determining the half life of the administered agents. [00290] In certain embodiments, the prophylactic or therapeutic agents of the invention are cyclically administered to a subject. Cycling therapy involves the administration of a first agent for a period of time, followed by the administration of a second agent and/or third agent for a period of time and repeating this sequential administration. Cycling therapy can reduce the development of resistance to one or more of the therapies, avoid or reduce the side effects of one of the therapies, and/or improves the efficacy of the treatment. [00291] In certain embodiments, prophylactic or therapeutic agents are administered in a cycle of less than about 3 weeks, about once every two weeks, about once every 10 days or about once every week. One cycle can comprise the administration of a therapeutic or prophylactic agent by infusion over about 90 minutes every cycle, about 1 hour every cycle, about 45 minutes every cycle. Each cycle can comprise at least 1 week of rest, at least 2 weeks of rest, at least 3 weeks of rest. The number of cycles administered is from about 1 to about 12 cycles, more typically from about 2 to about 10 cycles, and more typically from about 2 to about 8 cycles. [00292] In yet other embodiments, the therapeutic and prophylactic agents of the invention are administered in metronomic dosing regimens, either by continuous infusion or frequent administration without extended rest periods. Such metronomic administration can involve dosing at constant intervals without rest periods. Typically die therapeutic agents, in particular cytotoxic agents, are used at lower doses. Such dosing regimens encompass the chronic daily administration of relatively low doses for extended periods of time. In preferred embodiments, the use of lower doses can minimize toxic side effects and eliminate rest periods. In certain embodiments, the therapeutic and prophylactic agents are delivered by chronic low-dose or continuous infusion ranging from about 24 hours to about 2 days, to about 1 week, to about 2 weeks, to about 3 weeks to about 1 month to about 2 months, to about 3 months, to about 4 months, to about 5 months, to about 6 months. The scheduling of such dose regimens can be optimized by the skilled oncologist. [00293] In other embodiments, courses of treatment are administered concurrently to a mammal, i.e., individual doses of the therapeutics are administered separately yet within a tune interval such that molecules of the invention can work together with the other agent or agents. For example, one component may be administered one time per week in combination with the other components that may be administered one time every two weeks or one time every three weeks. In other words, the dosing regimens for the therapeutics are carried out concurrently even if the therapeutics are not administered simultaneously or within the same patient visit. When used in combination with other prophylactic and/or therapeutic agents, the molecules of the invention and the prophylactic and/or therapeutic agent can act additively or, more preferably, synergistically. In one embodiment, a molecule of the invention is administered concurrently with one or more therapeutic agents in the same pharmaceutical composition. In another embodiment, a molecule of the invention is administered concurrently with one or more other therapeutic agents in separate pharmaceutical compositions. In still another embodiment, a molecule of the invention is administered prior to or subsequent to administration of another prophylactic or therapeutic agent. The invention contemplates administration of a molecule of the invention in combination with other prophylactic or therapeutic agents by the same or different routes of administration, e.g., oral and parenteral. In certain embodiments, when a molecule of the invention is administered concurrently with another prophylactic or therapeutic agent that potentially produces adverse side effects including, but not limited to, toxicity, the prophylactic or therapeutic agent can advantageously be administered at a dose that falls below the threshold that the adverse side effect is elicited. [00295] The dosage amounts and frequencies of administration provided herein are encompassed by the terms therapeutically effective and prophylactically effective. The dosage and frequency further will typically vary according to factors specific for each patient depending on the specific therapeutic or prophylactic agents administered, the severity and type of cancer, the route of administration, as well as age, body weight, response, and the past medical history of the patient. Suitable regimens can be selected by one skilled in the art by considering such factors and by following, for example, dosages reported in the literature and recommended in the Physician's Desk Reference (56th ed., 2002). 5.7.1 ANTI-CANCER AGENTS [00296] In a specific embodiment, the methods of the invention encompass the administration of one or more molecules of the invention with one or more therapeutic agents used for the treatment and/or prevention of cancer. In one embodiment, angiogenesis inhibitors may be administered in combination with the molecules of the invention. Angiogenesis inhibitors that can be used in the methods and compositions of the invention include but are not limited to: Angiostatin (plasminogen fragment); antiangiogenic antithrombin III; Angiozyme; ABT-627; Bay 12-9566; Benefm; Bevacizumab; BMS-275291; cartilage-derived inhibitor (GDI); CAI; CD59 complement fragment; CEP-7055; • Col 3; Combretastatin A-4; Endostatin (collagen XVIII fragment); Fibronectin fragment; Gro-betaj Halofuginone; Heparinases; Heparin hexasaccharide fragment; HMV833; Human chorionic gonadotropin (hCG); IM-862; Interferon alpha/beta/gamma; Interferon inducible protein (IP-10); Interleukin-12; Kringle 5 (plasminogen fragment); Marimastat; Metalloproteinase inhibitors (TIMPs); 2-Methoxyestradiol; MMI270 (CGS 27023A); MoAb MC-1C11; Neovastat; NM-3; Panzem; PI-88; Placental ribonuclease inhibitor; Plasminogen activator inhibitor; Platelet factor-4 (PF4); Prinomastat; Prolactin 16kDa fragment; Proliferin-related protein (PRP); PTK 787/ZK 222594; Retinoids; Solimastat; Squalamine; SS 3304; SU 5416; SU6668; SU11248; Tetrahydrocortisol-S; tetrathiomolybdate; thalidomide; Thrombospondin-1 (TSP-1);,TNP-470; Transforming growth factor-beta (TGF-b); Vasculostatin; Vasostatin (calreticulin fragment); ZD6126; ZD 6474; farnesyl transferase inlu'bitors (FTI); and bisphosphonates. [00297] Anti-cancer agents that can be used in combination with the molecules of the invention in the various embodiments of the invention, including pharmaceutical compositions and dosage forms and kits of the invention, include, but are not limited to: acivicin; aclarubicin; acodazole hydrochloride; acronine; adozelesin; aldesleukin; altretamine; ambomycin; ametantrone acetate; aminoglutethimide; amsacrine; anastrozole; anthramycin; asparaginase; asperlin; azacitidine; azetepa; azotomycin; batimastat; benzodepa; bicalutamide; bisantrene hydrochloride; bisnatide dimesylate; bizelesin; bleomycin sulfate; brequinar sodium; bropirimine; busulfan; cactinomycin; calusterone; caracemide; carbethner; carboplatin; carmustine; carubicin hydrochloride; carzelesin; cedefingol; chlorambucil; cirolemycin; cisplatin; cladribine; crisnatolmesylatc; cyclophosphamide; cytarabine; dacarbazine; dactinomycin; daunorubicin hydrochloride; decitabine; dexonnaplatin; dezaguanine; dezaguanine mesylate; diaziquone; docetaxel; doxorubicin; doxorubicin hydrochloride; droloxifene; droloxifene citrate; dromostanolone propionate; duazomycin; edatrexate; eflornithine hydrochloride; elsamitrucin; enloplatin; enpromate; epipropidine; epirubicin hydrochloride; erbulozole; esorubicin hydrochloride; estramustine; estram'ustine phosphate sodium; etanidazole; etoposide; etoposide phosphate; etoprine; fadrozole hydrochloride; fazarabinc; fenretmide; floxuridine; fludarabine phosphate; fluorouracil; flurocitabine; fosquidone; fostriecin sodium; gemcitabine; gemcitabine hydrochloride; hydroxyurea; idarubicin hydrochloride; ifosfamide; ilmofosine; interleukin II (including recombinant interleukin II, or r!L2), interferon alfa-2a; interferon alfa-2b; interferon alfa-nl ; interferon alfa-n3; interferon beta-I a; interferon gamma-I b; iproplatin; irinotecan hydrochloride; lanreotide acetate; letrozole; leuprolide acetate; liarozole hydrochloride; lometrexol sodium; lomustine; losoxantrone hydrochloride; masoprocol; maytansine; mcchlorethamine hydrochloride; megestrol acetate; mclengcslrol acetate; melphalan; menogaril; mercaptopurine; methotrexate; methotrexate sodium; metoprine; meturedepa; mitindomide; mitocarcin; mitocromin; mitogillin; mitomalcin; mitomycin; mitosper; mitotane; mitoxantrone hydrochlonde; mycophenolic acid; nocodazole; nogalamycin; ormaplatin; oxisuran; paclitaxel; pegaspargase; peliomycin; pentamustine; peplomycin sulfate; perfosfamide; pipobroman; piposulfan; piroxantrone hydrochloride; plicamycin; plomestane; porfimer sodium; porfiromycin; prednimustine; procarbazine hydrochloride; puromycin; puromycin hydrochloride; pyrazofurin; riboprine; rogletimide; safmgol; safmgol hydrochloride; semustine; simtrazene; sparfosate sodium; sparsomycin; spirogermanium hydrocMoride; spiromustine; spiroplatin; streptonigrin; streptozocin; sulofenur; talisomycin; tecogalan sodium; tegafur; teloxantrone hydrochloride; temoporfin; teniposide; teroxirone; testolactone; thiamiprine; thioguanine; thiotepa; tiazofurin; tirapazamine; torcmifene citrate; trestolone acetate; triciribine phosphate; trimetrexate; trimetrexate glucuronate; triptorelin; tubulozole hydrochloride; uracil mustard; uredepa; vapreotide; verteporfm; vinblastine sulfate; vincristine sulfate; vindesine; vindesine sulfate; vinepidine sulfate; vinglycinate sulfate; vinleurosine sulfate; vinorelbine tartrate; vinrosidine sulfate; vinzolidine sulfate; vorozole; zeniplatin; zinostatin; zorubicin hydrochloride. Other anti-cancer drugs include, but are not limited to: 20-epi-l,25 dihydroxyvitaminDS; 5-ethynyluracil; abiraterone; aclarubicin; acylfulvene; adecypenol; adozelesin; aldesleukin; ALL-TK antagonists; altretamine; ambamustine; amidox; amifostine; aminolevulinic acid; amrubicin; amsacrine; anagrelide; anastrozole; andrographolide; angiogenesis inhibitors; antagonist D; antagonist G; antarelix; anti-dorsalizing morphogenetic protein-1; antiandrogen, prostatic carcinoma; antiestrogen; antineoplaston; antisense oligonucleotides; aphidicolin glycinate; apoptosis gene modulators; apoptosis regulators; apurinic acid; ara-CDP-DL-PTBA; arginine deaminase; asulacrine; atamestane; atrimustine; axinastatin 1; axinastatin 2; axinastatin 3; azasetron; azatoxin; azatyrosine; baccatin III derivatives; balanol; batimastat; BCR/ABL antagonists; beuzochlorins; benzoylstaurosporine; beta lactam derivatives; beta-alethine; betaclamycin B; betulinic acid; bFGF inhibitor; bicalutamide; bisantrene; bisaziridinylspermine; bisnafide; bistratene A; bizelesin; breflate; bropirimme; budotitane; buthionine sulfoximine; calcipotriol; calphostin C; camptothecin derivatives; canarypox IL-2; capecitabine; carboxamide-amico-triazole; carboxyamidotriazole; CaRest M3; CARN 700; cartilage derived inhibitor; carzelesin; casein kinase inhibitors (ICOS); castanospermine; cecropin B; cetrorelix; chlorlns; chloroquinoxaline sulfonamide; cicaprost; cis-porphyrin; cladribine; clomifene analogues; clotrimazole; collismycin A; collismycin B; combretastatin A4; combretastatin analogue; conagcnin; crambescidin 816; crisnatol; cryptophycin 8; cryptophycia A derivatives; curacin A; cyclopentanthraquinones; cycloplatam; cypemycin; cytarabine ocfosfate; cytolytic factor; cytostatin; dacliximab; decitabine; dehydrodidemnin B; desloreliii; dexamethasone; dcxifosfamide; dexrazoxane; dexverapamil; diaziquone; didemnin B; didox; diethylnorspermine; dihydro-5-azacytidine; dihydrotaxol, 9-; dioxamycin; diphenyl spiromustine; docetaxel; docosanol; dolasetron; doxifluridine; droloxifene; dronabinol; duocarmycin SA; ebselen; ecomustine; edelfosine; edrecolomab; eflornithine; elemene; emitefur; epirubicin; epristeride; estramustine analogue; estrogen agonists; estrogen antagonists; etanidazole; etoposide phosphate; exemestane; fadrozole; fazarabine; fenretiuide; filgrastim; finasteride; flavopiridol; flezelastine; fluasterone; fludarabine; fluorodaunorunicin hydrochloride; forfenimex; formestane; fostriecin; fotemustine; gadolinium texaphyrin; gallium nitrate; galocitabine; ganirelix; gelatinase inhibitors; gemcitabine; glutathione inhibitors; hepsulfam; heregulin; hexamethylene bisacetamide; hypericin; ibandronic acid; idarubicin; idoxifene; idramantone; ilmofosine; ilomastat; imidazoacridones; imiquimod; immunostimulantpeptides; insulin-like growth factor-1 receptor inhibitor; interferon agonists; interferons; interlcukins; iobcnguane; iododoxorubicin; ipomeanol, 4-; iroplact; irsogladine; isobengazole; isohomohalicondrin B; itasetron; jasplakinolide; kalialalide F; lamellarin-N triacetate; lanreotide; leinamycin; lenograstim; lentinan sulfate; leptolstatin; letrozole; leukemia inhibiting factor; leukocyte alpha interferon; leuprolide+estrogen-fprogesterone; leuprorelin; levamisole; Harozole; linear polyamine analogue; lipophilic disaccharide peptide; lipophilic platinum compounds; lissoclinamide 7; lobaplatin; lombricine; lometrexol; lonidamine; losoxantrone; lovastatin; loxoribine; lurtotecan; lutetium texaphyrin; lysofylline; lytic peptides; maitansine; mannostatin A; marimastat; masoprocol; maspin; matrilysin inhibitors; matrix metalloproteinase inhibitors; menogaril; merbarone; meterelin; methioninasc; metoclopramide; MIF inhibitor; mifepristone; miltefosine; mirimostim; mismatched double stranded RNA; mitoguazone; mitolactol; mitomycin analogues; mitonafide; mitotoxin fibroblast growth factor-saporin; mitoxantrone; mofarotene; molgramostirn; monoclonal antibody, human chorionic gonadotrophin; monophosphoryl lipid A+myobactcrium cell wall sk; mopidamol; multiple drug resistance gene inhibitor; multiple tumor suppressor 1-based therapy; mustard anticancer agent; mycaperoxide B; mycobacterial cell wall extract; myriaporone; N-acetyldinaline; N-substituted benzamides; nafavelin; nagrestip; naloxone+pentazocine; napavin; naphterpin; nartograstim; nedaplatin; nemorubicin; neridronic acid; neutral endopeptidase; nilutamide; nisamycin; nitric oxide modulators; nitroxide antioxidant; nitioillyn; 06-benzylguanine; octreotide; olcicenone; oligonucleotidcs; onapristone; ondansetron; ondansetron; oracin; oral cytokine inducer; ormaplatin; osaierone; oxaliplatin; oxaunomycin; paclitaxel; paclitaxel analogues; paclitaxel derivatives; palauamine; palmitoylrhizoxin; pamidronic acid; panaxytriol; panomifene; parabactin; pazelliptine; pegaspargase; peldesine; pentosan polysulfate sodium; pentostatin; pentrozole; perflubron; perfosfamide; perillyl alcohol; phenazinomycin; phenylacetate; phosphatase inhibitors; picibanil; pilocarpine hydrochloride; pirarubicin; piritrexim; placetin A; placetin B; plasminogen activator inhibitor; platinum complex; platinum compounds; platinum-triamine complex; porfimer sodium; porfiromycin; prednisone; propyl bis-acridone; prostaglandin J2; proteasome inhibitors; protein A-based immune modulator; protein kinase C inhibitor; protein kinase C inhibitors, microalgal; protein tyrosine phosphatase inhibitors; purine nucleoside phosphorylase inhibitors; purpurins; pyrazoloacridine; pyridoxylated hemoglobin polyoxyethylene conjugate; raf antagonists; raltitrexed; ramosetron; ras farnesyl protein transferase inhibitors; ras inhibitors; ras-GAP inhibitor; retelliptine demethylated; rhenium Re 186 etidronate; rhizoxin; ribozymes; RII retinamide; rogletimide; rohitukine; romurtide; roquinimex; rubiginone Bl; ruboxyl; safingol; saintopin; SarCNU; sarcophytol A; sargramostim; Sdi 1 mimetics; semustine; senescence derived inhibitor 1; sense oligonucleotides; signal transduction inhibitors; signal transduction modulators; single chain antigen binding protein; sizofiran; sobuzoxane; sodium borocaptate; sodium phenylacetate; solverol; somatomedin binding protein; sonermin; sparfosic acid; spicamycin D; spiromustine; splenopentin; spongistatin 1; squalamine; stem cell inhibitor; stem-cell division inhibitors; stipiamide; stromelysin inhibitors; sulfinosine; superactive vasoactive intestinal peptide antagonist; suradista; suramin; swainsonine; synthetic glycosaminoglycans; tallimustine; tamoxifen methiodide; tauromustine; tazarotene; tecogalan sodium; tegafur; tellurapyrylium; telomerase inhibitors; temoporfin; temozolomide; teniposide; tetrachlorodecaoxide; tetrazomine; thaliblastine; thiocoraline; thrombopoietin; thrombopoietin mimetic; thymalfasin; thymopoietin receptor agonist; thymotrinan; thyroid stimulating hormone; tin ethyl etiopurpurin; tirapazamine; titanocene bichloride; topsentin; toremifene; totipotent stem cell factor; translation inhibitors; tretinoin; triacetyluridine; triciribine; trimetrexate; triptorelin; tropisetron; turosteride; tyrosine kinase inhibitors; tyrphostins; UBC inhibitors; ubenimex; urogenital sinus-derived growth inhibitory factor; urokinase receptor antagonists; vapreotide; variolin B; vector system, erythrocyte gene therapy; velaresol; veramine; verdins; verteporfin; vinorelbine; vinxaltine; vitaxin; vorozole; zanoterone; zeniplatin; zilascorb; and zinostatin stimalamer. Preferred additional anti-cancer dnigs are 5-fluorouracil and leucovorin. [00298] Examples of therapeutic antibodies that can be used in methods of the invention include but are not limited to ZENAPAX® (daclizumab) (Roche Pharmaceuticals, Switzerland) which is an immunosuppressive, humanized anti-CD25 monoclonal antibody t for the prevention of acute renal allograft rejection; PANOREX™ which is a murine and-17-IA cell surface antigen IgG2a antibody (Glaxo Wellcome/Centocor); BEC2 which is a murine anti-idiotype (GD3 epitope) IgG antibody (ImClone System); IMC-C225 which is a chimeric anti-EGFR IgG antibody (ImClone System); VITAXIN™ which is a humanized anti-aVp3 integrin antibody (Applied Molecular Evolution/Medlmmune); Smart Ml 95 which is a humanized anti-CD33 IgG antibody (Protein Design Lab/Kanebo); LYMPHOCIDE™ which is a humanized anti-CD22 IgG antibody (Immunomedics); ICM3 is a humanized anti-ICAM3 antibody (ICOS Pharm); IDEC-114 is a primatied anti-CD80 antibody (IDEC Pharm/Mitsubishi); IDEC-131 is a humanized anti-CD40L antibody (IDEC/Eisai); EDEC-151 is aprimatized anti-CD4 antibody (IDEC); IDEC-152 is a primatized anti-CD23 antibody (IDEC/Seikagaku); SMART anti-CD3 is a humanized anti-CD3 IgG (Protein Design Lab); 5G1.1 is a humanized anti-complement factor 5 (C5) antibody (Alexion Pharm); D2E7 is a humanized anti-TNF-a antibody (CAT/BASF); CDP870 is a humanized anti-TNF-a Fab fragment (Celltech); IDEC-151 is a primatized anti-CD4 IgGl antibody (IDEC Pharm/SmithKline Bcecham); MDX-CD4 is a human anti-CD4 IgG antibody (Medarex/Eisai/Genmab); CDP571 is a humanized anti-TNF-a IgG4 antibody (Celltech); LDP-02 is a humanized anti-a4p7 antibody (LeukoSite/Gcnentcch); OrthoClone OKT4A is a humanized anti-CD4 IgG antibody (Ortho Biotech); ANTOVA™ is a humanized anti-CD40L IgG antibody (Biogen); ANTEGREN™ is a humanized anti-VLA-4 IgG antibody (Elan); and CAT-152 is a human anti-TGF-p2 antibody (Cambridge Ab Tech). Other examples of therapeutic antibodies that can be used in accordance with the invention are presented in Table 8. (Table Removed) 5.7.2 IMMUNOMODULATORY AGENTS AND ANTI-INFLAMMATORY AGENTS [00299] The present invention provides methods of treatment for autoimmune diseases and inflammatory diseases comprising administration of the molecules of the invention in conjunction with other treatment agents. Examples of immunomodulatory agents include, but are not limited to, methothrexate, ENBREL, REMCADE™, leflunomide, cyclophosphamide, cyclosporinc A, and macrolide antibiotics (e.g., FK506 (tacrolimus)), methylprednisolone (MP), corticosteroids, steriods, mycophenolate mofetil, rapamycin (sirolimus), mizoribine, deoxyspergualin, brequinar, malononitriloamindes (e.g., leflunamide), T cell receptor modulators, and cytokine receptor modulators. [00300] Anti-inflammatory agents have exhibited success in treatment of inflammatory and autoimmune disorders and are now a common and a standard treatment for such disorders. Any anti-inflammatory agent well-known to one of skill in the art can be used in the methods of the invention. Non-limiting examples of anti-inflammatory agents include non-steroidal anti-inflammatory drugs (NSAIDs), steroidal anti-inflammatory drugs, beta-agonists, anticholingeric agents, and methyl xanthines. Examples of NSAIDs include, but are not limited to, aspirin, ibuprofen, celecoxib (CELEBREX™), diclofenac (VOLTAREN™), etodolac (LODINE™), fenoprofen (NALFON™), indomethacin (INDOCIN™), ketoralac (TORADOL™), oxaprozin (DAYPRO™), nabumentone (RELAFEN™), sulindac (CLINORIL™), tolmentin (TOLECTIN™), rofecoxib (VIOXX™), naproxen (ALEVE™, NAPROSYN™), ketoprofen (ACTRON™) and nabumetone (RELAFEN™). Such NSAIDs function by inhibiting a cyclooxgenase enzyme (e.g., COX-1 and/or COX-2). Examples of steroidal anti-inflammatory drugs include, but are not limited to, glucocorticoids, dexamethasone (DECADRON™), cortisone, hydrocortisone, prednisone (DELTASONE™), prednisolone, triamcinolone, azulfidine, and eicosanoids such as prostaglandins, thromboxanes, and leulcotrienes. [00301] A non-limiting example of the antibodies that can be used for the treatment or prevention of inflammatory disorders in conjunction with the molecules of the invention is presented in Table 9, and a non-limiting example of the antibodies that can used for the treatment or prevention, of autoimmune disorder is presented in Table 10. Table 9: Therapeutic antibodies for the treatment of inflammatory diseases (Table 9 Removed) Table 10: Therapeutic antibodies for the treatment of autoimmune disorders (Table 10 Removed) 5.7.3 AGENTS FOR USE IN THE TREATMENT OF INFECTIOUS DISEASE [00302] In some embodiments, the molecules of the invention may be administered in combination with a therapeutically or prophylactically effective amount of one or additional therapeutic agents known to those skilled in the art for the treatment and/or prevention of an infectious disease. The invention contemplates the use of the molecules of the invention in combination with antibiotics known to those skilled in the art for the treatment and or prevention of an infectious disease. Antibiotics that can be used in combination with the molecules of the invention include, but are not limited to, macrolide (e.g., tobramycin (Tobi®)), a cephalosporin (e.g., cephalexin (Keflex®), ccphradine (Velosef®), cefuroxime (Ceftin®), cefprozil (Cefzil®), cefaclor (Ceclor®), cefixirne (Suprax®) or cefadroxil (Duricef®)), a clarithromycin (e.g., clarithromycin (Biaxin®)), an erythromycin (e.g., erythromycin (EMycin®)), a penicillin (e.g., penicillin V (V-Cillin K® or Pen Vee K®)) or a quinolone (e.g., ofloxacin (Floxin®), ciprofloxacin (Cipro®) or norfloxacin (Noroxin®)),aminoglycoside antibiotics (e.g., apramycin, arbekacin, bambermycins, butirosin, dibekacin, neomycin, neomycin, undecylenate, netilmicin, paromomycin, ribostamycin, sisomicin, and spectinomycin), amphenicol antibiotics (e.g., azidamfenicol, chloramphenicol, florfenicol, and thiamphenicol), ansamycin antibiotics (e.g., rifamide and rifampin), carbacephems (e.g., loracarbef), carbapenems (e.g., biapenem and imipenem), cephalosporins (e.g., cefaclor, cefadroxil, cefamandole, cefatrizine, cefazedone, cefozopran, cefpimizole, cefpiramide, and cefpirome), cephamycins (e.g., cefbuperazone, cefmetazole, and cefminox), monobactams (e.g., aztreonam, carumonam, and tigemonam), oxacephems (e.g., flomoxef, and moxalactam), penicillins (e.g., amdinocillin, amdinocillin pivoxil, amoxicillin, bacampicillin, benzylpenicillinic acid, " benzylpenicillin sodium, epiciiim, fenbenicillin, floxacillin, penamccillin, penethamate hydriodide, penicillin o-benethamine, penicillin 0, penicillin V, penicillin V benzathine, penicillin V hydrabamine, penimepicycline, and phencihicillin potassium), lincosamides (e.g., clindamycin, and lincomycin), amphomycin, bacitracin, capreomycin, colistin, enduracidin, enviomycin, tetracyclines (e.g., apicycline, chlortetracycline, clomocycline, and demeclocycline), 2,4-diamhiopyrimidines (e.g., brodimoprim), nitrofurans (e.g., furaltadone, and furazolium chloride), quinolones and analogs thereof (e.g., cinoxacin,, clinafloxacin, flumequine, and grepagloxacin), sulfonamides (e.g., acetyl sulfamethoxypyrazine, benzylsulfamide, noprylsulfamide, phthalylsulfacetamide, sulfachrysoidine, and sulfacytine), sulfones (e.g., diathymosulfone, glucosulfone sodium, and solasulfone), cycloserine, mupirocin and tuberin. [00303] In certain embodiments, the molecules of the invention can be administered in combination with a therapeutically or prophylactically effective amount of one or more antifungal agents. Antirungal agents that can be used in combination with the molecules of the invention include but are not limited to amphotericin B, itraconazole, ketoconazole, fluconazole, intrathecal, flucytosine, miconazole, butoconazole, clotrimazole, nystatin, terconazole, tioconazole, ciclopirox, econazole, haloprogrin, naftitlne, terbinafme, undecylenate, and griseofuldin. [00304] In some embodiments, the molecules of the invention can be administered in combination with a therapeutically or prophylactically effective amount of one or more antiviral agent. Useful anti-viral agents that can be used in combination with the molecules of the invention include, but are not limited to, protease inhibitors, nucleoside reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors and nucleoside analogs. Examples of antiviral agents include but are not limited to zidovudine, acyclovir, gangcyclovir, vidarabine, idoxuridine, trifluridine, and ribavirin, as well as foscarnet, amantadine, rimantadine, saquinavir, indinavir, amprenavir, lopinavir, ritonavir, the alpha-interferons; adefovir, clevadine, entecavir, pleconaril. 5.8 VACCINE THERAPY [00305] The invention further encompasses using a composition of the invention to induce an immune response against an antigenic or immunogenic agent, including but not limited to cancer antigens and infectious disease antigens (examples of which are disclosed infra). The vaccine compositions of the invention comprise one or more antigenic or immunogenic agents to which an immune response is desired, wherein the one or more antigenic or immunogenic agents is coated with a variant antibody of the invention that has an enhanced affinity to FcyRIILA.. The vaccine compositions of the invention arc particularly effective in eliciting an immune response, preferably a protective immune response against the antigenic or immunogenic agent. [00306] In some embodiments, the antigenic or immunogenic agent in the vaccine compositions of the invention comprise a virus against which an immune response is desired. The viruses may be recombinant or chimeric, and are preferably attenuated, Production of recombinant, chimeric, and attenuated viruses may be performed using standard methods known to one skilled in the art. The invention encompasses a live recombinant viral vaccine or an inactivated recombinant viral vaccine to be formulated in accordance with the invention. A live vaccine may be preferred because multiplication in the host leads to a prolonged stimulus of similar kind and magnitude to that occurring in natural infections, and therefore, confers substantial, long-lasting immunity. Production of such live recombinant virus vaccine formulations may be accomplished using conventional methods involving propagation of the virus in cell culture or in the allantois of the chick embryo followed by purification. [00307] In a specific embodiment, the recombinant virus is non-pathogenic to the subject to which it is administered. In this regard, the use of genetically engineered viruses for vaccine purposes may require the presence of attenuation characteristics in these strains. The introduction of appropriate mutations (e.g., deletions) into the templates used for transfection may provide the novel viruses with attenuation characteristics. For example, specific missense mutations which are associated with temperature sensitivity or cold adaptation can be made into deletion mutations. These mutations should be more stable than the point mutations associated with cold or temperature sensitive mutants and reversion frequencies should be extremely low. Recombinant DNA technologies for engineering recombinant viruses are known in the art and encompassed in the invention. For example, techniques for modifying negative strand RNA viruses are known hi the art, see, e.g., U.S. Patent No. 5,166,057, which is incorporated herein by reference in its entirety. [00308] Alternatively, chimeric viruses with "suicide" characteristics may be constructed for use in the intradermal vaccine formulations of the invention. Such viruses would go through only one or a few rounds of replication within the host. When used as a vaccine, the recombinant virus would go through limited replication cycle(s) and induce a sufficient level of immune response but it would not go further in the human host and cause disease. Alternatively, inactivated (killed) virus may be formulated in accordance with the invention. Inactivated vaccine formulations may be prepared using conventional techniques to "kill" the chimeric viruses. Inactivated vaccines are "dead" in the sense that their infectivity has been destroyed. Ideally, the infectivity of the virus is destroyed without affecting its immunogenicity. In order to prepare inactivated vaccines, the chimeric virus may be grown in cell culture or in the allantois of the chick embryo, purified by zonal ultracentrifugation, inactivated by formaldehyde or p-propiolactone, and pooled. [00309] In certain embodiments, completely foreign epitopes, including antigens derived from other viral or non-viral pathogens can be engineered into the virus for use in the intradermal vaccine formulations of the invention. For example, antigens of non-related viruses such as HIV (gp!60, gp!20, gp41) parasite antigens (e.g., malaria), bacterial or fungal antigens or tumor antigens can be engineered into the attenuated strain. [00310] Virtually any heterologous gene sequence may be constructed into the chimeric viruses of the invention for use in the intradermal vaccine formulations. Preferably, heterologous gene sequences are moieties and peptides that act as biological response modifiers. Preferably, epitopes that induce a protective immune response to any of a variety of pathogens, or antigens that bind neutralizing antibodies may be expressed by or as part of the chimeric viruses. For example, heterologous gene sequences that can be constructed into the chimeric viruses of the invention include, but are not limited to, influenza and parainfluenza hemagglutinin neuraminidase and fusion glycoproteins such as the HN and F genes of human PIV3. In yet another embodiment, heterologous gene sequences that can be engineered into the chimeric viruses include those that encode proteins with immuno-modulating activities. Examples of immuno-modulating proteins include, but are not limited to, cytokines, interferon type 1, gamma interferon, colony stimulating factors, interleukin -1, -2, -4, -5, -6, -12, and antagonists of these agents. [00311] In yet other embodiments, the invention encompasses pathogenic cells or viruses, preferably attenuated viruses, which express the variant antibody on their surface. [00312] In alternative embodiments, the vaccine compositions of the invention comprise a fusion polypeptide wherein an antigenic or immunogenic agent is operau'vely linked to a variant antibody of the invention that has an enhanced affinity for FcyRUIA. Engineering fusion polypeptides for use in the vaccine compositions of the invention is performed using routine recombinant DNA technology methods and is within the level of ordinary skill. [00313] The invention further encompasses methods to induce tolerance in a subject by administering a composition of the invention. Preferably a composition suitable for inducing tolerance in a subject, comprises an antigenic or immunogenic agent coated with a variant antibody of the invention, wherein the variant antibody has a higher affinity to FcyRIIB. Although not intending to be bound by a particular mechanism of action, such compositions are effective in inducing tolerance by activating the FcyRIIB mediatated inhibitory pathway. S.9 COMPOSITIONS AND METHODS OF ADMINISTERING [00314] The invention provides methods and pharmaceutical compositions comprising molecules of the invention (i.e., diabodies) comprising multiple epitopc binding domains and, optionally, an Fc domain (or portion thereof). The invention also provides methods of treatment, prophylaxis, and amelioration of one or more symptoms associated with a disease, disorder or infection by administering to a subject an effective amount of a fusion protein or a conjugated molecule of the invention, or a pharmaceutical composition comprising a fusion protein or a conjugated molecule of the invention. In a preferred aspect, an antibody, a fusion protein, or a conjugated molecule, is substantially purified (i.e., substantially free from substances that limit its effect or produce undcsired side-effects). In a specific embodiment, the subject is an animal, preferably a mammal such as non-primate (e.g., cows, pigs, horses, cats, dogs, rats etc.} and a primate (e.g., monkey such as, a cynomolgous monkey and a human). In a preferred embodiment, the subject is a human. In yet another preferred embodiment, the antibody of the invention is from the same species as the subject. [00315] Various delivery systems are known and can be used to administer a composition comprising molecules of the invention, e.g., encapsulation in liposomes, microparticles, microcapsules, recombinant cells capable of expressing the antibody or fusion protein, receptor-mediated endocytosis (See, e.g., Wu and Wu, 1987, J. Biol. Chem. 262:4429-4432), construction of a nucleic acid as part of a retro viral or other vector, etc. Methods of administering a molecule of the invention include, but are not limited to, parenteral administration (e.g., intradermal, intramuscular, intraperitoneal, intravenous and subcutaneous), epidural, and mucosal (e.g., intranasal and oral routes). In a specific embodiment, the molecules of the invention are administered intramuscularly, intravenously, or subcutaneously. The compositions may be administered by any convenient route, for example, by infusion or bolus injection, by absorption through epithelial or mucocutaneous linings (e.g., oral mucosa, rectal and intestinal mucosa, etc.} and may be administered together with other biologically active agents. Administration can be systemic or local. In addition, pulmonary administration can also be employed, e.g., by use of an inhaler or nebulizer, and formulation with an aerosolizing agent. See, e.g., U.S. Patent Nos. 6,019,968; 5,985, 320; 5,985,309; 5,934,272; 5,874,064; 5,855,913; 5,290,540; and 4,880,078; and PCT Publication Nos. WO 92/19244; WO 97/32572; WO 97/44013; WO 98/31346; and WO 99/66903, each of which is incorporated herein by reference in its entirety. [00316] The invention also provides that the molecules of the invention, are packaged in a hermetically sealed container such as an ampoule or sachette indicating the quantity of antibody. In one embodiment, the molecules of the invention are supplied as a dry sterilized lyophilized powder or water free concentrate in a hermetically sealed container and can be reconstituted, e.g., with water or saline to the appropriate concentration for administration to a subject. Preferably, the molecules of the invention are supplied as a dry sterile lyophilized powder in a hermetically sealed container at a unit dosage of at least 5 mg, more preferably at least 10 mg, at least 15 mg, at least 25 mg, at least 35 mg, at least 45 mg, at least 50 mg, or at least 75 mg. The lyophilized molecules of the invention should be stored at between 2 and 8°C in their original container and the molecules should be administered within 12 hours, preferably within 6 hours, within 5 hours, within 3 hours, or within 1 hour after being reconstituted, hi an alternative embodiment, molecules of the invention are supplied in liquid form in a hermetically sealed container indicating the quantity and concentration of the molecule, fusion protein, or conjugated molecule. Preferably, the liquid form of the molecules of the invention are supplied in a hermetically sealed container at least 1 mg/ml, more preferably at least 2.5 mg/ml, at least 5 mg/ml, at least 8 mg/ml, at least 10 mg/ml, at least 15 mg/kg, at least 25 mg/ml, at least 50 mg/ml, at least 100 mg/ml, at least 150 mg/ml, at least 200 mg/ml of the molecules. [00317] The amount of the composition of the invention which will be effective in the treatment, prevention or amelioration of one or more symptoms associated with a disorder can be determined by standard clinical techniques. The precise dose to be employed in the formulation will also depend on the route of administration,'and the seriousness of the condition, and should be decided according to the judgment of the practitioner and each patient's circumstances. Effective doses may be extrapolated from dose-response curves derived from in vitro or animal model test systems. [00318] For diabodies encompassed by the invention, the dosage administered to a patient is typically 0.0001 mg/kg to 100 mg/kg of the patient's body weight. Preferably, the dosage administered to a patient is between 0.0001 mg/kg and 20 mg/kg, 0.0001 mg/kg and 10 mg/kg, 0.0001 mg/kg and 5 mg/kg, 0.0001 and 2 mg/kg, 0.0001 and 1 mg/kg, 0.0001 mg/kg and 0.75 mg/kg, 0.0001 mg/kg and 0.5 mg/kg, 0.0001 mg/kg to 0.25 mg/kg, 0.0001 to 0.15 mg/kg, 0.0001 to 0.10 mg/kg, 0.001 to 0.5 mg/kg, 0.01 to 0.25 mg/kg or 0.01 to 0.10 mg/kg of the patient's body weight. The dosage and frequency of administration of diabodies of the invention may be reduced or altered by enhancing uptake and tissue penetration of the diabodies by modifications such as, for example, lipidation. [00319] In one embodiment, the dosage of the molecules of the invention administered to a patient are O.Olmg to lOOOmg/day, when used as single agent therapy. In another embodiment the molecules of the invention are used in combination with other therapeutic compositions and the dosage administered to a patient are lower than when said molecules are used as a single agent therapy. [00320] In a specific embodiment, it may be desirable to administer the pharmaceutical compositions of the invention locally to the area in need of treatment; this may be achieved by, for example; and not by way of limitation, local infusion, by injection, or by means of an implant, said implant being of a porous, non-porous, or gelatinous material, including membranes, such as sialastic membranes, or fibers. Preferably, when administering a molecule of the invention, care must be taken to use materials to which the molecule does not absorb. [00321] In another embodiment, the compositions can be delivered in a vesicle, in particular a liposome (See Langer, Science 249:1527-1533 (1990); Treat et al, in Liposomes in the Therapy of Infectious Disease and Cancer. Lopez-Bercstein and Fidler (eds.), Liss, New York, pp. 353- 365 (1989); Lopez-Berestein, ibid., pp. 3 17-327; see generally ibid.). [00322] In yet another embodiment, the compositions can be delivered in a controlled release or sustained release system. Any technique known to one of skill in the art can be used to produce sustained release formulations comprising one or more molecules of the invention. See, e.g., U.S. Patent No. 4,526,938; PCT publication WO 91/05548; PCT publication WO 96/20698; Ning et al., 1996, "Intratumoral Radioimmunotheraphy of a Human Colon Cancer Xenograft Using a Sustained-Release Gel," Radiotherapy & Oncology 39:179-189, Song et al., 1995, "Antibody Mediated Lung Targeting of Long-Circulating Emulsions," PDA Journal of Pharmaceutical Science & Technology 50:372-397; Cleek et al, 1997, "Biodegradable Polymeric Carriers for a bFGF Antibody for Cardiovascular Application," Pro. Int'l. Symp. Control. Rel. Bioact. Mater. 24:853-854; and Lam et al, 1997, "Microencapsulation of Rccombinant Humanized Monoclonal Antibody for Local Delivery," Proc. Int'l Symp. Control Rel Bioact. Mater. 24:759-760, each of which is incorporated herein by reference in its entirety. In one embodiment, a pump may be used in a controlled release system (See Langer, supra; Sefton, 1987, CRC Grit. Ref. Biomed. Eng. 14:20; Buchwald et al, 1980, Surgery 88:507; and Saudek et al., 1989, N. Engl J. Med. 321:574). In another embodiment, polymeric materials can be used to achieve controlled release of antibodies (see e.g., Medical Applications of Controlled Release. Longer and Wise (eds.), CRC Pres., Boca Raton, Florida (1974); Controlled Drug Bioavailability, Drug Product Design and Performance, Smolen and Ball (eds.), Wiley, New York (1984); Ranger and Peppas, 1983, J., Macromol. Sci. Rev. Macromol Chem. 23:61; See also Levy et al, 1985, Science 228:190; During et al, 1989, Ann. Neurol. 25:351; Howard etal, 1989, J. Newosurg. 1 1:105); U.S. Patent No. 5,679,377; U.S. Patent No. 5,916,597; U.S. Patent No. 5,912,015; U.S. Patent No. 5,989,463; U.S. Patent No. 5,128,326; PCT Publication No. WO 99/15154; and PCT Publication No. WO 99/20253). Examples of polymers used in sustained release formulations include, but are not limited to, poly(2-hydroxy ethyl methacrylate), poly(methyl methacrylate), poly(acrylic acid), poly(ethylene-co-vinyl acetate), poly(methacrylic acid), polyglycolides (PLG), polyanhydrides, poly(N-vinyl pyrrolidone), poly(vinyl alcohol), polyacrylamide, poly(ethylene glycol), polylactides (PLA), poly(lactide-co-glycolides) (PLGA), and polyorthoesters. In yet another embodiment, a controlled release system can be placed in proximity of the therapeutic target (e.g., the lungs), thus requiring only a fraction of the systemic dose (see, e.g., Goodson, in Medical Applications of Controlled Release, supra, vol. 2, pp. 115-138 (1984)). In another embodiment, polymeric compositions useful as controlled release implants are used according to Dunn et al. (See U.S. 5,945,155). This particular method is based upon the therapeutic effect of the in situ controlled release of the bioactive material from the polymer system. The implantation can generally occur anywhere within the body of the patient in need of therapeutic treatment. In another embodiment, a non-polymeric sustained delivery system is used, whereby a non-polymeric implant in the body of the subject is used as a drug delivery system. Upon implantation in the body, the organic solvent of the implant will dissipate, disperse, or leach from the composition into surrounding tissue fluid, and the non-polymeric material will gradually coagulate or precipitate to form a solid, microporous matrix (See U.S. 5,888,533). [00323] Controlled release systems are discussed in the review by Langer (1990, Science 249:1527-1533). Any technique known to one of skill in the art can be used to produce sustained release formulations comprising one or more therapeutic agents of the invention. See, e.g., U.S. Patent No. 4,526,938; International Publication Nos. WO 91/05548 and WO 96/20698; Ning et al, 1996, Radiotherapy & Oncology 39:179-189; Song etal, 1995, PDA Journal of Pharmaceutical Science & Technology 50:372-397; Cleek et al., 1997, Pro. Int'l. Symp. Control. Rel. Bioact. Mater. 24:853-854; and Lam et al., 1997, Proc. Int'l. Symp. Control Rel. Bioact. Mater. 24:759-760, each of which is incorporated herein by reference in its entirety. [00324] In a specific embodiment where the composition, of the invention is a nucleic acid encoding a diabody of the invention, the nucleic acid can be administered in vivo to promote expression of its encoded diabody, by constructing it as part of an appropriate nucleic acid expression vector and administering it so that it becomes intracellular, e.g., by use of a retroviral vector (See U.S. Patent No. 4,980,286), or by direct injection, or by use of microparticle bombardment (e.g., a gene gun; Biolistic, Dupont), or coating with lipids or cell-surface receptors or transfecting agents, or by administering it in linkage to a homeobox-like peptide which is known to enter the nucleus (See e.g., Joliot et al, 1991, Proc. Natl Acad. Sci. USA 88:1864-1868), etc., Alternatively, a nucleic acid can be introduced intracellularly and incorporated within host cell DNA for expression by homologous recombination. [00325] Treatment of a subject with a therapeutically or prophylactically effective amount of molecules of the invention can include a single treatment or, preferably, can include a series of treatments. In a preferred example, a subject is treated with molecules of the invention in the range of between about 0.1 to 30 mg/kg body weight, one time per week for between about 1 to 10 weeks, preferably between 2 to 8 weeks, more preferably between about 3 to 7 weeks, and even more preferably for about 4, 5, or 6 weeks. In other embodiments, the pharmaceutical compositions of the invention are administered once a day, twice a day, or three times a day. In other embodiments, the pharmaceutical compositions are administered once a week, twice a week, once every two weeks, once a month, once every six weeks, once every two months, twice a year or once per year. It will also be appreciated that the effective dosage of the molecules used for treatment may increase or decrease over the course of a particular treatment. 5.9.1 PHARMACEUTICAL COMPOSITIONS [00326] The compositions of the invention include bulk drug compositions useful in the manufacture of pharmaceutical compositions (e.g., impure or non-sterile compositions) and pharmaceutical compositions (i.e., compositions that arc suitable for administration to a subject or patient) which can be used in the preparation of unit dosage forms. Such compositions comprise a prophylactically or therapeutically effective amount of a prophylactic and/or therapeutic agent disclosed herein or a combination of those agents and a pharmaceutically acceptable carrier. Preferably, compositions of the invention comprise a prophylactically or therapeutically effective amount of one or more molecules of the invention and a pharmaceutically acceptable carrier. [00327] The invention also encompasses pharmaceutical compositions comprising a diabody molecule of the invention and a therapeutic antibody (e.g., tumor specific monoclonal antibody) that is specific for a particular cancer antigen, and a pharmaceutically acceptable carrier. [00328] In a specific embodiment, the term "pharmaceutically acceptable" means approved by a regulatory agency of the Federal or a state government or listed in the U.S. Pharmacopeia or other generally recognized pharmacopeia for use in animals, and more particularly in humans. The term "carrier" refers to a diluent, adjuvant (e.g., Freund's adjuvant (complete and incomplete), excipient, or vehicle with which the therapeutic is administered. Such pharmaceutical carriers can be sterile liquids, such as water and oils, including those of petroleum, animal, vegetable or synthetic origin, such as peanut oil, soybean oil, mineral oil, sesame oil and the like. Water is a preferred carrier when the pharmaceutical composition is administered intravenously. Saline solutions and aqueous dextrose and glycerol solutions can also be employed as liquid carriers, particularly for injectable solutions. Suitable pharmaceutical excipients include starch, glucose, lactose, sucrose, gelatin, malt, rice, flour, chalk, silica gel, sodium stearate, glycerol monostearate, talc, sodium chloride, dried skim milk', glycerol, propylene, glycol, water, ethanol and the like. The composition, if desired, can also contain minor amounts of wetting or emulsifying agents, or pH buffering agents. These compositions can take the form of solutions, suspensions, emulsion, tablets, pills, capsules, powders, sustained-release formulations and the like. [00329] Generally, the ingredients of compositions of the invention are supplied either separately or mixed together in unit dosage form, for example, as a dry lyophilized powder or water free concentrate in a hermetically sealed container such as an ampoule or sachette indicating the quantity of active agent. Where the composition is to be administered by infusion, it can be dispensed with an infusion bottle containing sterile pharmaceutical grade water or saline. Where the composition is administered by injection, an ampoule of sterile water for injection or saline can be provided so that the ingredients may be mixed prior to administration. [00330] The compositions of the invention can be formulated as neutral or salt forms. Pharmaceutically acceptable salts include, but are not limited to those formed with anions such as those derived from hydrochloric, phosphoric, acetic, oxalic, tartaric acids, etc., and those formed with cations such as those derived from sodium, potassium, ammonium, calcium, ferric hydroxides, isopropylamine, triethylamine, 2-ethyIamino ethanol, histidine, procaine, etc. 5.9.2 GENE THERAPY [00331] In a specific embodiment, nucleic acids comprising sequences encoding molecules of the invention, are administered to treat, prevent or ameliorate one or more symptoms associated with a disease, disorder, or infection, by way of gene therapy. Gene therapy refers to therapy performed by the administration to a subject of an expressed or expressible nucleic acid. In this embodiment of the invention, the nucleic acids produce their encoded antibody or fusion protein that mediates a therapeutic or prophylactic effect. [00332] Any of the methods for gene therapy available in the art can be used according to the present invention. Exemplary methods are described below. [00333] For general reviews of the methods of gene therapy, see Goldspiel ct al, 1993, Clinical Pharmacy 12:488-505; Wu and Wu, 1991, Biotherapy 3:87-95; Tolstoshev, 1993, Ann. Rev. Pharmacol. Toxicol 32:573-596; Mulligan, Science 260:926-932 (1993); and Morgan and Anderson, 1993, Ann. Rev. Biochem. 62:191-217; May, 1993, TIBTECH 11(5):155-215. Methods commonly known in the art of recombinant DNA technology which can be used are described in Ausubel et al. (eds.), Current Protocols in Molecular Biology. John Wiley & Sons, NY (1993); and Kriegler, Gene Transfer and Expression, A Laboratory Manual. Stockton Press, NY (1990). [00334] In a preferred aspect, a composition of the invention comprises nucleic acids encoding a diabody of the invention, said nucleic acids being part of an expression vector that expresses the antibody in a suitable host. In particular, such nucleic acids have promoters, preferably heterologous promoters, operably linked to the antibody coding region, said promoter being inducible or constitutive, and, optionally, tissue-specific. In another particular embodiment, nucleic acid molecules are used in which the antibody coding sequences and any other desired sequences are flanked by regions that promote homologous recombination at a desired site in the genome, thus providing for intrachromosomal expression of the antibody encoding nucleic acids (Koller and Smithies, 1989, Proc. Natl Acad. Sci. USA 86:8932-8935; and Zijlstra et al, 1989, Nature 342:435-438). [00335] In another preferred aspect, a composition of the invention comprises nucleic acids encoding a fusion protein, said nucleic acids being a part of an expression vector that expresses the fusion protein in a suitable host. In particular, such nucleic acids have promoters, preferably heterologous promoters, operably linked to the coding region of a fusion protein, said promoter being inducible or constitutive, and optionally, tissue-specific. In another particular embodiment, nucleic acid molecules are used in which the coding sequence of the fusion protein and any other desired sequences are flanked by regions that promote homologous recombination at a desired site in the genome, thus providing for intrachromosomal expression of the fusion protein. [00336] Delivery of the nucleic acids into a subject may be either direct, in which case the subject is directly exposed to the nucleic acid or nucleic acid-carrying vectors, or indirect, in which case, cells are first transformed with the nucleic acids in vitro, then transplanted into the subject. These two approaches are known, respectively, as in vivo or ex vivo gene therapy. [00337] In a specific embodiment, the nucleic acid sequences are directly administered in vivo, where it is expressed to produce the encoded product. This can be accomplished by any of numerous methods known in the art, e.g., by constructing them as part of an appropriate nucleic acid expression vector and administering it so that they become intracellular, e.g., by infection using defective or attenuated retroviral or other viral vectors (see U.S. Patent No. 4,980,286), or by direct injection of naked DNA, or by use of microparticle bombardment (e.g., a gene gun; Biolistic, Dupont), or coating with lipids or cell-surface receptors or transfecting agents, encapsulation in liposomes, microparticles, or microcapsules, or by administering them in linkage to a peptide which is known to enter the nucleus, by administering it in linkage to a an antigen subject to receptor-mediated endocytosis (See, e.g., Wu and Wu, 1987, J. Biol. Chem. 262:4429-4432) (which can be used to target cell types specifically expressing the receptors), etc. In another embodiment, nucleic acid-an antigen complexes can be formed in which the an antigen comprises a fusogenic viral peptide to disrupt endosomes, allowing the nucleic acid to avoid lysosomal degradation. In yet another embodiment, the nucleic acid can be targeted in vivo for cell specific uptake and expression, by targeting a specific receptor (See, e.g., PCT Publications WO 92/06180; WO 92/22635; W092/20316; W093/14188; WO 93/20221). Alternatively, the nucleic acid can be introduced intracellularly and incorporated within host cell DNA for expression, by homologous recombination (Koller and Smithies, 1989, Proc. Natl. Acad. Sci. USA 86:8932-8935; and Zijlstra et al, 1989, Nature 342:435-438). [00338] In a specific embodiment, viral vectors that contain nucleic acid sequences encoding a molecule of the invention (e.g., a diabody or a fusion protein) are used. For example, a retroviral vector can be used (See Miller et al., 1993, Meth. Enzymol. 217:581-599). These retroviral vectors contain the components necessary for the correct packaging of the viral genome and integration into the host cell DNA. The nucleic acid sequences encoding the antibody or a fusion protein to be used in gene therapy are cloned into one or more vectors, which facilitates delivery of the nucleotide sequence into a subject. More detail about retroviral vectors can be found in Boesen et al, (1994, Biotherapy 6:291-302), which describes the use ot a retroviral vector to deliver the mdr 1 gene to hematopoietic stem cells in order to make the stem cells more resistant to chemotherapy. Other references illustrating the use of retroviral vectors in gene therapy are: Clowes et al., 1994, J. Clin. Invest. 93:644-651; Klein et al, 1994, Blood 83:1467-1473; Salmons and Gunzbcrg, 1993, Human Gene Therapy 4:129-141; and Grossman and Wilson, 1993, Curr. Opin, in Genetics andDevel. 3:110-114. [00339] Adenoviruses are other viral vectors that can be used in gene therapy. Adenoviruses are especially attractive vehicles for delivering genes to respiratory epithelia. Adenoviruses naturally infect respiratory epithelia where they cause a mild disease. Other targets for adenovirus-based delivery systems are liver, the central nervous system, endothelial cells, and muscle. Adenoviruses have the advantage of being capable of infecting non-dividing cells. Kozarsky and Wilson (Current Opinion in Genetics and Development 3:499-503, 1993, present a review of adenovirus-based gene therapy. Bout et al, (Human Gene Therapy, 5:3-10, 1994) demonstrated the use of adenovirus vectors to transfer genes to the respiratory epithelia of rhesus monkeys. Other instances of the use of adenoviruses in gene therapy can be found in Rosenfeld et al, 1991, Science 252:431-434; Rosenfeld et al, 1992, Cell 68:143-155; Mastrangeli et al, 1993, J. Clin. Invest. 91:225-234; PCT Publication W094/12649; and Wang et al, 1995, Gene Therapy 2:775-783. In a preferred embodiment, adenovirus vectors are used. [00340] Adeno-associated virus (AAV) has also been proposed for use in gene therapy (see, e.g.,Walsh et al, 1993, Proc. Soc. Exp. Biol Med. 204:289-300 and U.S. Patent No. 5,436,146). [00341] Another approach to gene therapy involves transferring a gene to cells in tissue culture by such methods as electroporation, lipofection, calcium phosphate mediated transfection, or viral infection. Usually, the method of transfer includes the transfer of a selectable marker to the cells. The cells are then placed under selection to isolate those cells that have taken up and are expressing the transferred gene. Those cells are then delivered to a subject. [00342] In this embodiment, the nucleic acid is introduced into a cell prior to administration in vivo of the resulting recombinant cell. Such introduction can be carried out by any method known hi the art, Including but not limited to, transfection, electroporation, microinjcction, infection with a viral or bacteriophage vector, containing the nucleic acid sequences, cell fusion, chromosome-mediated gene transfer, microcellmediated gene transfer, spheroplast fusion, etc. Numerous techniques are known in the art for the introduction of foreign genes into cells (See, e.g., Loeffler and Behr, 1993, 'Methl'Enzymol. 217:599-618, Cohen et al, 1993, Meth. Enzymol. 217:618-644; and CItn. Pharma. Thei: 29:69-92,1985) and may be used in accordance with the present invention, provided that the necessary developmental and physiological functions of the recipient cells are not disrupted. The technique should provide for the stable transfer of the nucleic acid to the cell, so that the nucleic acid is expressible by the cell and preferably heritable and expressible by its cell progeny. [00343] The resulting recombinant cells can be delivered to a subject by various methods known in the art. Recombinant blood cells (e.g., hematopoietic stem or progenitor cells) are preferably administered intravenously. The amount of cells envisioned for use depends on the desired effect, patient state, etc., and can be determined by one skilled in the art. [00344] Cells into which a nucleic acid can be introduced for purposes of gene therapy encompass any desired, available cell type, and include but are not limited to epithelial cells, endothelial cells, keratinocytes, fibroblasts, muscle cells, hepatocytes; blood cells such as T lymphocytes, B lymphocytes, monocytes, macrophages, neutrophils, eosinophils, megakaryocytes, granulocytes; various stem or progenitor cells, in particular hematopoietic stem or progenitor cells, e.g., as obtained from bone marrow, umbilical cord blood, peripheral blood, fetal liver, etc. [00345] In a preferred embodiment, the cell used for gene therapy is autologous to the subject. [00346] In an embodiment in which recombinant cells are used in gene therapy, nucleic acid sequences encoding an antibody or a fusion protein are introduced into the cells such that they are expressible by the cells or their progeny, and'the recombinant cells are then administered in vivo for therapeutic effect. In a specific embodiment, stem or progenitor cells are used. Any stem and/or progenitor cells which can be isolated and maintained in vitro can potentially be used in accordance with this embodiment of the present invention (See e.g., PCT Publication WO 94/08598; Stemple and Anderson, 1992, Cell! 1:973-985; Rheinwald, 1980, Meth. Cell Bio. 21A:229; and Pittelkow and Scott, 1986, Afoyo Clinic Proc. 61:771). [00347] In a specific embodiment, the nucleic acid to be introduced for purposes of gene therapy comprises an inducible promoter operably linked to the coding region, such that expression of the nucleic acid is controllable by controlling the presence or absence of the appropriate inducer of transcription. KITS [00348] The invention provides a pharmaceutical pack or kit comprising one or more containers filled with the molecules of the invention. Additionally, one or more other prophylactic or therapeutic agents useful for the treatment of a disease can also be included in the pharmaceutical pack or Icit. The invention also provides a pharmaceutical pack or kit comprising one or more containers filled with one or more of the ingredients of the pharmaceutical compositions of the invention. Optionally associated with such container(s) can be a notice in the form prescribed by a governmental agency regulating the manufacture, use or sale of pharmaceuticals or biological products, which notice reflects approval by the agency of manufacture, use or sale for human administration. [00349] The present invention provides kits that can be used in the above methods. In one embodiment, a kit comprises one or more molecules of the invention. In another embodiment, a kit further comprises one or more other prophylactic or therapeutic agents useful for the treatment of cancer, in one or more containers. In another embodiment, a Icit further comprises one or more cytotoxic antibodies that bind one or more cancer antigens associated with cancer. In certain embodiments, the other prophylactic or therapeutic agent is a chemotherapeutic. In other embodiments, the prophylactic or therapeutic agent is a biological or hormonal therapeutic. 5.10 CHARACTERIZATION AND DEMONSTRATION OF THERAPEUTIC UTILITY [00350] Several aspects of the pharmaceutical compositions, prophylactic, or therapeutic agents of the invention are preferably tested in vitro, in a cell culture system, and in an animal model organism, such as a rodent animal model system, for the desired therapeutic activity prior to use in humans. For example, assays which can be used to determine whether administration of a specific pharmaceutical composition is desired, include cell culture assays in which a patient tissue sample is grown in culture, and exposed to or otherwise contacted with a pharmaceutical composition of the invention, and the effect of such composition upon the tissue sample is observed. The tissue sample can be obtained by biopsy from the patient. This test allows the identification of the therapeutically most effective prophylactic or therapeutic molecule(s) for each individual patient. In various specific embodiments, in vitro assays can be carried out with representative cells of cell types involved in an autoimmune or inflammatory disorder (e.g., T cells), to determine if a pharmaceutical composition of the invention has a desired effect upon such cell types. [00351] Combinations of prophylactic and/or therapeutic agents can be tested in suitable animal model systems prior to use in humans. Such animal model systems include, but are not limited to, rats, mice, chicken, cows, monkeys, pigs, dogs, rabbits, etc. Any animal system well-known in the art may be used. In a specific embodiment of the invention, combinations of prophylactic and/or therapeutic agents are tested in a mouse model system. Such model systems are widely used and well-known to the skilled artisan. Prophylactic and/or therapeutic agents can be administered repeatedly. Several aspects of the procedure may vary. Said aspects include the temporal regime of administering the prophylactic and/or therapeutic agents, and whether such agents are administered separately or as an admixture. [00352] Preferred animal models for use in the methods of the invention are, for example, transgenic mice expressing human FcyRs on mouse effector cells, e.g., any mouse model described in U.S. 5,877,396 (which is incorporated herein by reference in its entirety) can be used in the present invention. Transgenic mice for use in the methods of the invention include, but are not limited to, mice carrying human FcyRIIIA; mice carrying human FcyRIIA; mice carrying human FcyRIIB and human FcyRIIIA; mice carrying human FcyRIIB and human FcyRIIA. Preferably, mutations showing the highest levels of activity in the functional assays described above will be tested for use in animal model studies prior to use in humans. Sufficient quantities of antibodies may be prepared for use in animal models using methods described supra, for example using mammalian expression systems and purification methods disclosed and exemplified herein. [00353] Mouse xenograft models may be used for examining efficacy of mouse antibodies generated against a tumor specific target based on the affinity and specificity of the epitope bing domains of the diabody molecule of the invention and the ability of the diabody to elicit an immune response (Wu et al., 2001, Trends Cell Biol. 11: S2-9). Transgenic mice expressing human FcyRs on mouse effector cells are unique and are tailor-made animal models to test the efficacy of human Fc-FcyR interactions. Pairs of FcyRIIIA, FcyRIIIB and FcyRIIA transgenic mouse lines generated in the lab of Dr. Jeffrey Ravetch (Through a licensing agreement with Rockefeller U. and Sloan Kettering Cancer center) can be used such as those listed in the Table 11 below. Table 11: Mice Strains (Table 11 Removed) [00354] The anti-inflammatory activity of the combination therapies of invention can be determined by using various experimental animal models of inflammatory arthritis known in the art and described in Crofford L.J. and Wilder R.L., "Arthritis and Autoimmunjty in Animals", in Arthritis and Allied Conditions: A Textbook of Rheumatology, McCarty et a/.(eds.), Chapter 30 (Lee and Febiger, 1993). Experimental and spontaneous animal models of inflammatory arthritis and autoimmune rheumatic diseases can also be used to assess the and-inflammatory activity of the combination therapies of invention. The following are some assays provided as examples, and not by limitation. [00355] The principle animal models for arthritis or inflammatory disease known in the art and widely used include: adjuvant-induced arthritis rat models, collagen-induced arthritis rat and mouse models and antigen-induced arthritis rat, rabbit and hamster models, all described in Crofford L.J. and Wilder R.L., "Arthritis and Autoimmunity in Animals", in Arthritis and Allied Conditions: A Textbook of Rheumatology, McCarty et «/.(eds.), Chapter 30 (Lee and Febiger, 1993), incorporated herein by reference in its entirety. [00356] The anti-inflammatory activity of the combination therapies of invention can be assessed using a carrageenan-induced arthritis rat model. Carrageenan-induccd arthritis has also been used in rabbit, dog and pig in studies of chronic arthritis or inflammation. Quantitative histomorphometric assessment is used to determine therapeutic efficacy. The methods for using such a carrageenan-induced arthritis model is described in Hansra P. et al, "Carrageenan-induced Arthritis in the Rat," Inflammation, 24(2): 141-155, (2000). Also commonly used are zymosan-induced inflammation animal models as known and described in the art. [00357] The anti-inflammatory activity of the combination therapies of invention can also be assessed by measuring the inhibition of carrageenan-induced paw edema in the rat, using a modification of the method described in Winter C. A. et al, "Carrageenan-induced Edema in Hind Paw of the Rat as an Assay for Anti-inflammatory Drugs" Proc. Soc. Exp. Biol Med. Ill, 544-547, (1962). This assay has been used as a primary in vivo screen for the anti-inflammatory activity of mostNSAIDs, and is considered predictive of human efficacy. The anti-inflammatory activity of the test prophylactic or therapeutic agents is expressed as the percent inhibition of the increase in hind paw weight of the test group relative to the vehicle dosed control group. [00358] Additionally, animal models for inflammatory bowel disease can also be used to assess the efficacy of the combination therapies of invention (Kim et al,, 1992, Scand. J. Gastroentrol. 27:529-537; Strober, 1985, Dig. Dis. Sci. 30(12 Suppl):3S-10S). Ulcerative cholitis and Crohn's disease are human inflammatory bowel diseases that can be induced hi animals. Sulfated polysaccharides including, but not limited to amylopectin, carrageen, amylopectin sulfate, and dextran sulfate or chemical irritants including but not limited to trinitrobenzenesulphonic acid (TNBS) and acetic acid can be administered to animals orally to induce inflammatory bowel diseases. [00359] Animal models for autoimmune disorders can also be used to assess the efficacy of the combination therapies of invention. Animal models for autoimmune disorders such as type 1 diabetes, thyroid autoimmunity, systemic lupus eruthematosus, and glomerulonephritis have been developed (Flanders et al, 1999, Autoimmunity 29:235-246; Kroghera/., 1999, Btochimie 81:511-515; Foster, 1999, Semin. Nephrol. 19:12-24). [00360] Further, any assays known to those skilled in the art can be used to evaluate the prophylactic and/or therapeutic utility of the combinatorial therapies disclosed herein for autoimmune and/or inflammatory diseases. [00361] Toxicity and efficacy of the prophylactic and/or therapeutic protocols of the instant invention can be determined by standard pharmaceutical procedures in cell cultures or experimental animals, e.g., for determining the LDso (the dose lethal to 50% of the population) and the EDso (the dose therapeutically effective in 50% of the population). The dose ratio between toxic and therapeutic effects is the therapeutic index and it can be expressed as the ratio LDso/EDso. Prophylactic and/or therapeutic agents that exhibit large therapeutic indices are preferred. While prophylactic and/or therapeutic agents that exhibit toxic side effects may be used, care should be taken to design a delivery system that targets such agents to the site of affected tissue in order to minimize potential damage to uninfected cells and, thereby, reduce side effects. [00362] The data obtained from the cell culture assays and animal studies can be used in formulating a range of dosage of the prophylactic and/or therapeutic agents for use in humans. The dosage of such agents lies preferably within a range of circulating concentrations that include the EDso with little or no toxiciry. The dosage may vary within this range depending upon the dosage form employed and the route of administration utilized. For any agent used in the method of the invention, the therapeutically effective dose can be estimated initially from cell culture assays. A dose may be formulated in animal models to achieve a circulating plasma concentration range that includes the ICso (i.e., the concentration of the test compound that achieves a half-maximal inhibition of symptoms) as determined in cell culture. Such information can be used to more accurately determine useful doses in humans. Levels in plasma may be measured, lor example, by high performance liquid chromatography. [00363] The anti-cancer activity of the therapies used in accordance with the present invention also can be determined by using various experimental animal models for the study of cancer such as the SCID mouse model or transgenic mice or nude mice with human xenografts, animal models, such as hamsters, rabbits, etc. known in the art and described in Relevance of Tumor Models for Anticancer Drug Development (1999, eds. Fiebig and Burger); Contributions to Oncology (1999, Karger); The Nude Mouse in Oncology Research (1991, eds, Boven and Winograd); and Anticancer Drug Development Guide (1997 ed. Teicher), herein incorporated by reference in their entireties, [00364] Preferred animal models for determining the therapeutic efficacy of the molecules of the invention are mouse xenograft models. Tumor cell lines that can be used as a source for xenograft tumors include but are not limited to, SKBR3 and MCF7 cells, which can be derived from patients with breast adenocarcinoma. These cells have both erbB2 and prolactin receptors. SKBR3 cells have been used routinely in the art as ADCC and xenograft rumor models. Alternatively, OVCAR3 cells derived from a human ovarian adenocarcinoma can be used as a source for xenograft tumors. [00365] The protocols and compositions of the invention are preferably tested in vitro, and then in vivo, for the desired therapeutic or prophylactic activity, prior to use in humans. Therapeutic agents and methods may be screened using cells of a tumor or malignant cell line. Many assays standard in the art can be used to assess such survival and/or growth; for example, cell proliferation can be assayed by measuring 3H-thyrm'dine incorporation, by direct cell count, by detecting changes in transcriptional activity of known genes such as proto-oncogenes (e.g., fos, myc) or cell cycle markers; cell viability can be assessed by trypan blue staining, differentiation can be assessed visually based on changes hi morphology, decreased growth and/or colony formation in soft agar or tubular network formation in three-dimensional basement membrane or extracellular matrix preparation, etc. [00366] Compounds for use in therapy can be tested in suitable animal model systems prior to testing in humans, including but not limited to in rats, mice, chicken, cows, monkeys, rabbits, hamsters, etc., for example, the animal models described above. The compounds can then be used in the appropriate clinical trials. [00367] Further, any assays known to those skilled in the art can be used to evaluate the prophylactic and/or therapeutic utility of the combinatorial therapies disclosed herein for treatment or prevention of cancer, inflammatory disorder, or autoimmune disease. 6. EXAMPLES 6.1 DESIGN AND CHARACTERIZATION OF COVALENT BISPECIFIC DIABODIES [00368] A monospecific covalent diabody and a bispecific covalent diabody were constructed to asses the recombinant production, purification and binding characteristics of each. The affinity purified diabody molecules that were produced by the recombinant expression systems described herein were found by SDS-PAGE and SEC analysis to consist of a single dimerc species. ELISA and SPR analysis further revealed that the covalent bispecific diabody exhibited affinity for both target antigens and could bind both antigens simultaneously. [00369] Materials and Methods; [00370] Construction ami Design of Polypeptide Molecules: Nucleic acid expression vectors were designed to produce four polypeptide constructs, schematically represented in FIG. 2 . Construct 1 (SEQ ID N0:9) comprised the VL domain of humanized 2B6 antibody , which recognizes FcyRIIB, and the VH domain of humained 3G8 antibody, which recognizes FcyRIIIA. Construct 2 (SEQ ID NO:11) comprised the VL domain of Hu3G8 and the VH domain of Hu2B6. Construct 3 (SEQ ID NO: 12) comprised the VL domain of Hu3G8 and the VH domain of Hu3G8. Construct 4 (SEQ ID NO: 13) comprised the VL domain of Hu2B6 and the VH domain of Hu2B6. [00371] PCR and Expression Vector Construction: The coding sequences of the VL or VH domains were amplified from template DNA using forward and reverse primers designed such that the intial PCR products would contain overlapping sequences, allowing overlapping PCR to generate the coding sequences of the desired polypeptide constructs. [00372] Initial PCR amplification of template DNA: Approximately 35 ng of template DNA, e.g. light chain and heavy chain of antibody of interest; 1 ul of lOuM forward and reverse primers; 2.5 ul of lOx pfuUltra buffer (Stratagene, Inc.); 1 ul of 10 mM dNTP; 1 ul of 2.5 units/ul of pfuUltra DNA polymerase (Stratagene, Inc.); and distilled water to 25 ul total volume were gently mixed in a microfuge tube and briefly spun in a microcentrifuge to collect the reaction mixture at the bottom of the tube. PCR reactions were performed using GeneAmp PCR System 9700 (PE Applied Biosystem) and the following settings: 94°C, 2 minutes; 25 cycles of 94°C, each 15 seconds; 58°C, 30 seconds; and 72°C, 1 minute. [00373] The VL of Hu2B6 was amplified from the light chain of Hu2B6 using forward and reverse primers SEQ ID NO: 57 and SEQ ID N0:58, respectively. The VH of Hu2B6 was amplified from the heavy chain of Hu2B6 using forward and reverse primers S'EQ ID NO: 59 and SEQ ID N0:60, respectively. The VL of Hu3G8 was amplified from the light chain of Hu3G8 using forward and reverse primers SEQ ID NO: 57 and SEQ ID N0:61, respectively. The VH of Hu3G8 was amplified from the heavy chain of Hu3G8 using forward and reverse primers SEQ ID NO: 62 and SEQ ID N0:63, respectively. [00374] PCR products were electrophoresed on a 1% agarose gel for 30 minutes at 120 volts. PCR products were cut from the gel and purified using MinElute GE1 Extraction Kit (Qiagen, Inc.). [00375] Overlapping PCR: Intitial PCR products were combined as described below and amplified using the same PCR conditions described for initial amplification of template DNA. Products of overlapping PCR were also purified as described supra. [00376] The nucleic acid sequence encoding construct 1, SEQ ID N0:9 (shown schematically in FIG. 2), was amplified by combining the PCR products of the amplifications of VL Hu2B6 and VH Hu3G8, and forward and reverse primers SEQ ID N0:57 and SEQ ID NO:63, respectively. The nucleic acid sequence encoding construct 2, SEQ ID NO:11 (shown schematically in FIG. 2), was amplified by combining the PCR products of the amplifications of VL Hu3G8 and VH Hu2B6, and forward and reverse primers SEQ ID NO:57 and SEQ ID N0:60, respectively. The nucleic acid sequence encoding construct 3, SEQ ID N0:12 (shown schematically in FIG. 2), was amplified by combining the PCR products of the amplifications of VL Hu3G8 and VH Hu3G8, and forward and reverse primers SEQ ID N0:57 and SEQ ID NO:63, respectively. The nucleic acid sequence encoding construct 4, SEQ ID NO: 13 (shown schematically in FIG. 2), was amplified by combining the PCR products of the amplifications of VL Hu2B6 and VH Hu2B6, and forward and reverse primers SEQ ID NO:57 and SEQ ID NO:60, respectively. [00377] The forward primers of the VL domains (i.e., SEQ ID N0:57) and reverse primers of the VH domains (i.e., SEQ ID N0:60 and SEQ ID N0:63) contained unique restriction sites to allow cloning of the final product into an expression vector. Purified overlapping PCR products were digested with restriction endonucleases Nhc I and EcoR I, and cloned into the pCIneo mammalian expression vector (Promega, Inc.). The plasmids encoding constructs were designated as identified in Table 12: Table 12. PLASMID CONSTRUCTS (Table Removed) [00378] " Polypeptide/diabody Expression: pMGX0669, encoding construct i.was cotransfected with pMGX0667, encoding construct 2, in HEK-293 cells using Lipofectamine 2000 according to the manufacturer's directions (Invitrogen). Co-transfection of tliese two plasmids was designed to lead to the expression of a covalent bispecific diabody (CBD) immunospecific for both FcvPJIB and FcyRIIIA (the h2B6-h3G8 diabody). pMGX0666 and pMGX0668, encoding constructs 3 and 4, respectively, were separately transfected into HEK-293 cells for expression of a covalent monospecific diabody (CMD), immunospecific for FcyRIIIA (h3G8 diabody) and FcyRIIB (h2B6 diabody), respectively. Following three days in culture, secreted products were purified from the conditioned media. [00379] Purification: Diabodies were captured from the conditioned medium using the relevant antigens coupled to CNBr activated Sepharose 4B. The affinity Sepharose resin was equilibrated in 20 mM Tris/HCl, pH 8.0 prior to loading. After loading, the resin was washed with equilibration buffer prior to elution. Diabodies were eluted from the washed resin using 50 mM Glycine pli 3.0. Eluted diabodies were immediately neutralized with 1M Tris/HCl pH 8.0 and concentrated using a centrifugation type concentrator. The concentrated diabodies were further purified by size exclusion chromatography using a Superdex 200 column equilibrated in PBS. [00380] SEC: Size exclusion chromatography was used to analyze the approximate size and heterogeneity of the diabodies eluted from the column. SEC analysis was performed on a GE healthcare Superdex 200HR 10/30 column equilibrated with PBS. Comparison with the elution profiles of a full length IgG (~150 kDa), an Fab fragment (~50 kDa) and a single chain Fv (-30 kDa) were used as controls). [00381] ELISA: The binding of eluted and purified diabodies was characterized by ELISA assay, as described in 5.4.2. 50 ul/well of a 2 ug/ml solution of sCD32B-Ig was coated on 96-well Maxisorp plate in Carbonate buffer at 4°C over night. The plate was washed three times with PBS-T (PBS, 0.1% Tween 20) and blocked by 0.5% BSA hi PBS-T for 30 minutes at room temperature. Subsequently, h2B6-h3G8 CBD, h2B6 CMD, or h3GS CMD were diluted into the blocking buffer in a serial of two-fold dilutions to generate a range of diabody concentrations, from 0.5 ug/ml to 0.001 ug/ml. The plate was then incubated at room temperature for 1 hour. After washing with PBS-T three tunes, 50 ul/well of 0.2 ug/ml sCD16A-Biotin was added to each well. The plate was again incubated at room temperature for 1 hour. After washing with PBS-T three times, 50 ul/well of a 1:5000 dilution of HRP conjugated streptavidin (Amersham Pharmacia Biotech) was used for detection. The HRP-streptavidin was allowed to incubate for 45 minutes at room temperature. "The plate was washed with PBS-T three times and developed using 80 ul/well of 1MB substrate. After a 10 minute incubation, the HRP-TMB reaction was stopped by adding 40 ul/well of 1% H2S04. The OD450 nm was read by using a 96-well plate reader and SOFTmax software, and results plotted using GraphPadPrism 3.03 software. [00382] BIAcore Assay: The kinetic parameters of the binding of eluted and purified diabodies were analyzed using a BIAcore assay (BIAcore instrument 1000, BIAcore Inc., Piscataway, NJ.) and associated software as described in section 5.4.3. [00383] sCD16A, sCD32B or sCD32A (negative control) were immobilized on one of the four flow cells (flow cell 2) of a sensor chip surface through ainine coupling chemistry (by modification of carboxymethyl groups with mixture of NHS/EDC) such that about 1000 response units (RU) of either receptor was immobilized on the surface. Following this, the unreacted active esters were "capped off with an injection of 1M Et-NH2. Once a suitable surface was prepared, covalent bispecific diabodies (h2B6-h3G8 CBD) or covalent monospecific diabodies (h2B6 CMD or h3G8 CMB) were passed over the surface by 180 second injections of a 6.25-200nM solution at a 70 mL/min flow rate. h3G8 scFV was also tested for comparison. [00384] Once an entire data set was collected, the resulting binding curves were globally fitted using computer algorithms supplied by the manufacturer, BIAcore, Inc. (Piscataway, NJ). These algorithms calculate both the Kon and K0ir, from which the apparent equilibrium binding constant, KD is deduced as the ratio of the two rate constants (i.e., Kog/Kon). More detailed treatments of how the individual rate constants arc derived can be found in the BIAevaluaion Software Handbook (BIAcore, Inc., Piscataway, NJ). [00385] Association and dissociation phases were fitted separately. Dissociation rate constant was obtained for interval 32-34 sec of the 180 sec dissociation phase; association phase fit was obtained by a 1:1 Langmuir model and base fit was selected on the basis Rmax and chi2 criteria for the bispecific diabodies and scFv; Bivalent analyte fit was used for CMD binding. [00386] Results [00387] SDS-PAGE analysis under non-reducing conditions revealed that the purified product of the h3G8 CMD, h2B6 CMD and h2B6-h3G8 CBD expression systems were each a single species with an estimated molecular weight of approximately 50 IcDa (FIG. 3, lanes 4, 5 and 6, respectively). Under reducing conditions, the product purified from either of the CMD expression systems ran as a single band (lanes 1 and 2), while the product purified from the h2B6-h3G8 CBD system was revealed to be 2 separate proteins (FIG. 3, lane 3). All polypeptides purified from the expression system and visualized by SDS-PAGE under reducing conditions migrated at approximately 28 kDa. [00388] SEC analysis of each of the expression system products also revealed a single molecular species (FIG. 4B), each of which eluted at the same approximate time as an Fab fragment of IgG (~50kDa) (FIG. 4A). The results indicate that affinity purified product was a homogenous covalent homodimer for the case of CMD expression system and a homogenous covalent heterodimer for the case of the h2B6-h3G8 CBD. [00389] An ELISA sandwich assay was used to test binding of the h2B6-h3G8 CBD for specificity to either or both of CD32B and/or CD16A (FIG. 5). CD32B served as the target antigen and CD16A was used as the secondary probe. The positive signal in the ELIZA revealed that the heterodimeric h2B6-h3G8 CBD had specificity for both antigens. Similar testing of the h3G8 CMD (which should not bind CD32B) showed no signal. [00390] SPR analysis indicated that h3G8 CMD immunospecifically recognized sCD16 but not sCD32B, that h2B6 CMD immunospecifically recognized sCD32B but not sCD16, and that h2B6-h3G8 CBD immunospecifically recognized both sCD16 and sCD32B (FIGS. 6A-B). None of the diabodies tested bound the control receptor, sCD32A (FIG. 6C). [00391] SPR analysis was also used to estimate the kinetic and equilibrium constants of the CMDs and h2B6-h3G8 CBD to sCD16 and/or sCD32B. Results were compared to the same constants calculated for an h3G8 scFV. FIGS. 7A-E show the graphical results of the SPR analysis. The kinetic on and off rates, as well as the equilibrium constant, calculated from the results depicted in FIG. 7 are provided in Table 13. Table 13. Kinetic and Equilibrium Constants Calculated from BIAcore Data. (Table 13 Removed) [00392] Coupled with the results of the ELISA analysis, the studies confirm that the h2B6-h3G8 covalent heterodimer retained specificity for both CD32B and CD16, and was capable of binding both antigens simultaneously. The molecule is schematically represented in FIG. 8. 6.2 DESIGN AND CHARACTERIZATION OF COVALENT BISPECIFIC DIABODIES COMPRISING Fc DOMAINS [00393] In an effort to create an IgG like molecule, i.e., comprising an Fc domain, one of the polypeptides comprising the hetcrodimeric CBD molecule presented in Example 6.1 was modified to further comprise an Fc domain (creating a 'heavier' and 'lighter' chain, analogous to an antibody heavy and light chain). The heterodimeric bispeciilc molecule would then contain an Fc domain that will dimerize with a homologous molecule, forming a tetrameric IgG-like molecule with tetravalency (i.e, formed by dimerization via the Fc domains of the heterodimeric bispecific molecules). Interestingly, such tetrameric molecules were not detected in the conditioned media of recombinant expression systems using functional assays, e.g., testing the conditioned media for imrnunospecific binding to target antigens. Instead, only a dimeric molecule, comprising monomers consisting of a VL, VH and Fc domain, were detected in such functional assays. To test whether stability of the theoretical tetrameric structure was at issue, polypeptides comprising the Fc domain were engineered to further comprise a hinge region while the polypeptides comprising the 'lighter' chain were engineered to further comprise the 6 C-terminal amino acids of the constant domain of the human kappa light chain. When such reengineered 'heavier' and 'lighter; chains were co-expressed in the recombinant expression systems, functional assays detected diabody molecules that were able to immunospecifically bind both of the target antigens and anti-Fc antibodies. [00394] Materials and Methods [00395] Construction and Design of Potypeptide Molecules: Nucleic acid expression vectors were designed to produce modified versions of constructs 1 and 2 presented in Example 6.1. Construct 5 (SEQ ID NO: 14) and 6 (SEQ ID NO: 15), were created by engineering construct 1 and 2, respectively to further comprise an Fc domain. Construct 7 (SEQ ID NO: 16) was created by engineering construct 1 was to further comprise the sequence FNRGEC (SEQ ID NO: 23) at its C-terminus. Construct 8 (SEQ ID N0:18) was created by engineering construct 2 to further comprise a hinge region and Fc domain (comprising V215A mutation). Schematic representation of constructs 5-8 is shown in FIG. 9. [00396] PCR and Expression Vector Construction: All PCR and PCR product purification protocols were as described in Example 6.1 Plasmids pMGX0669 and pMGX0667 served as templates for the coding sequences of constructs 1 and 2, respectively. The coding sequences for the of HulgG Fc domain and/or hinge domain were SEQ ID N0:5 or SEQ ID N0:l and SEQ ID NO:5, respectively. The coding sequences of the template DNAs were amplified using forward and reverse primers such that the PCR products would contain overlapping sequences, allowing overlapping PCR to generate the coding sequences of the desired products. [00397] The coding sequence of construct 1 was amplified from pMGX0669 using forward and reverse primers SEQ ID NO:57 and SEQ ID N0:64, respectively. The coding sequence of construct 2 was amplified from pMGX0667 using forward and reverse primers SEQ ID N0:57 and SEQ ID NO:65, respectively. HulgG hinge-Fc was amplified using forward and reverse primers SEQ ID NO:67 and SEQ ID N0:68, respectively. Construct 7 (SEQ ID NO: 16) was amplified from pMGX0669 using forward and reverse primers SEQ ID NO:57 and SEQ ID NO:69. [00398] Overlapping PCR: Initial PCR products were combined as described below, amplified and purified as described in example 6.1. [00399] The nucleic acid sequence encoding construct 5, SEQ ID NO: 14 (shown schematically in FIG. 9), was amplified by combining the PCR products of the amplifications of construct 1 and HulgG Fc, and forward and reverse primers SEQ ID N0:57 and SEQ ID N0:66, respectively. The nucleic acid sequence encoding construct 6, SEQ ID NO: 15 (shown schematically in FIG. 9), was amplified by combining the PCR products of the amplifications of construct 2 and HulgG Fc, and forward and reverse primers SEQ ID N0:57 and SEQ ID NO:66, respectively. The nucleic acid sequence encoding construct 8, SEQ ID NO:18 (shown schematically in FIG. 9), was amplified by combining the PCR products of the amplifications of construct 2 and HulgG hinge-Fc, and forward and reverse primers SEQ ID N0:57 and SEQ ID N0:68, respectively. [00400] Final products were cloned into pCIneo mammalian expression vector (Promega, Inc.) as previously described. The plasmid encoding constructs were designated as identified in Table 14: Table 14. PLASMID CONSTRUCTS (Table 14 Removed) [00401] Polypeptide/diabody Expression: Four separate cotransfections into in HEK- 293 cells using Lipofectamine 2000, as described in section 6.1, were performed: pMGX0669 and pMGX0674, encoding constructs 1 and 6, respectively;; pMGX0667 and "pMGXCT676, encoding constructs 2 and 5, respectively; and pMGX0677 and pMGX0678, encoding constructs 7 and 8, respectively. [00402] Co-transfection of these plasmids was designed to lead to the expression of a bispecific diabody (CBD) of tetravalency with IgG-like structure, immunospecific for both FcyRIIB and FcyRHIA, An additional cotransfection was also performed: pMGX0674 and pMGX0676, encoding constructs 6 and 5, respectively. Following three days in culture, conditioned media was harvested. The amount of secreted product in the conditioned media was quantitiated by anti IgG Fc ELISA using purified Fc as a standard. The concentrations of product in the samples was then normalized based on the quantitation, and the normalized samples used for the remaining assays. [00403] ELISA: The binding of diabody molecules secreted into the medium was assayed by sandwich ELISA as described, supra. Unless indicated, CD32B was used to coat the plate, i.e., as the target protein, and HRP- conjugated CD 16 was used as the probe. [00404] Results [00405] An ELISA assay was used to test the normalized samples from the recombinant expression systems comprising constructs 1 and 6 (pMGX669-pMGX674), constructs 2 and 5 (pMGX667-pNGX676) and constructs 5 and 6 (pMGX674-pMGX676) for expression of diabody molecules capable of simultaneous binding to CD32B and CD16A (FIG. 10). The ELISA data indicated that co-transfection with constructs 1 and 6 or co-transfection with constructs 2 and 5 failed to produce a product that could bind either or both antigens (FIG. 10, D and A, respectively). However, co-transfection of constructs 5 and 6 lead to secretion of a product capable of binding to both CD32B and CD 16 antigens. The latter product was a dimer of constructs 5 and 6, containing one binding site for each antigen with a structure schematically depicted in FIG. 11. [00406] In order to drive formation of an IgG like heterotetrameric structure, the coding sequence for six additional amino acids was appended to the C-terminal of construct 1, generating construct 7 (SEQ ID NO:16 and shown schematically in FIG. 9). The six additional amino acids, FNRGEC (SEQ ID NO.23), were derived from the C-terminal end of the the Kappa light chain and normally interact with the upper hinge domain of the heavy chain, in an IgG molecule. A hinge domain was then engineered into construct 6, generating construct 8 (SEQ ID NO: 18 and FIG. 9). Construct 8 additionally comprised an amino-acid mutation hi the upper hinge region, A215V. Expression plasmids encoding construct 7 and construct 8, pMGX677 and pMGX678, respectively, were then cotransfected into HEK-293 cells and expressed as described. [00407] Diabody molecules produced from the recombinant expression system comprising constructs 7 and 8 (pMGX0677 + pMGX0678), were compared in an ELISA assay for binding to CD32B and CD16A to diabody molecules produced from expression systems comprising constructs 1 and 6 (pMGX669 + pMGX674), constructs 2 and 8 (pMGX669 + pMGX67S), and constructs 6 and 7 (pMGX677 + pMGX674) (FIG. 12). [00408] As before, the molecule produced by the expression system comprising constructs 1 and 6 (pMGX669 + pMGX674) proved unable to bind both CD32A and CD16A (FIG. 10 and FIG. 12). In contrast, the product from the co-expression of either constructs 7 and 6 (pMGX0677 + pMGX0674) or from the co-expression of constructs 7 and 8 (pMGX0677-pMGX0678) were able to bind both CD32B and GDI6 (FIG. 12). It is noted that construct 7 is analogous to construct 1, with the exception that construct 7 comprises the C-terminal sequence FNRGEC (SEC ID N0:23); and that construct 8 is analogous to construct 6, except that construct 8 comprises a hinge domain and the mutation A215V. The data indicate that the addition of the 6 extra amino-acids from the C-terminus of the C-kappa light chain (FNRGEC; SEQ ID NO:23) to the non-Fc bearing, 'lighter,' chain helped stabilize the formation of the tetrameric IgG-like diabody molecules, regardless of whether the corresponding heavier chain comprised a hinge domain (i.e., pMGX0677 + pMGX0674 and pMGX0677-pMGX0678, FIG. 12). The addition of the hinge domain to the Fc bearing 'heavier' polypeptide, without the addition of the FNRGEC (SEQ ID NO:23) C-terminal sequence to the corresponding 'lighter' chain, was apparently unable to effect similar stabilization (i.e., lack of binding by product of co-transfectibn of constructs 2 and 8 (pMGX669 + pMGX678)). The structure of the tetrameric diabody molecule is schematically represented in FIG. 13. 6.3 EFFECT OF DOMAIN ORDER AND ADDITIONAL DISULFIDE BONDS ON FORMATION OF TETRAMERIC IgG-LIKE DIABODY [00409] The effect of additional stabilization between the 'lighter' and 'heavier' polypeptide chains of the tetrameric IgG-like diabody molecule was investigated by substitution of selected residues on the polypeptide chains with cysteines. The additional cysteine residues provide for additional disulfide bonds between the 'heavier' and 'lighter' chains. Additionally, domain order on binding activity was investigated by moving the Fc domain or the hinge-Fc domain from the C-terminal end of the polypeptide chain to the N-terminus. Although the binding activity of the molecule comprising the additional disulfide bonds was not altered relative to earlier constructed diabody molecules with such bonds, transferring the Fc or hinge-Fc domain to the N-terminus of the 'heavier' polypeptide chain comprising the diabody surprisingly improved binding affinity and/or avidity of the bispecific molecule to one or both of its target antigens. [00410] Materials and Methods [00411] ConstriictionandDesisn ofPnlypeptide Molecules: Nucleic acid expression vectors were designed to produce modified versions of constructs 5, 6 and 8 presented in Example 6.2. Construct 9 (SEQ ID N0:19) and construct 10 (SEQ ID N0:20) (both shown schematically in FIG. 13) were analogous to constructs 8 and 6, with the exception that Fc domain or hinge-Fc domain, respectively, was shifted from the C-terminus of the polypeptide to the N-terminus. Additionally all Fc domains used were wild-type IgGl Fc domains. Construct 11, SEQ ID N0:21, (shown schematically in FIG. 14) was analogous to construct 2 from Example 6.1 except that the C-terminus was designed to further comprise the sequence FNRGEC (SEQ ID N0:23). Construct 12, SEQ ID NO:22 (shown schematically in FIG. 14) was analogous to construct 5 from Example 6.2 except that the Fc domain further comprised a hinge region. Also, for constructs 11 and 12, the 2B6 VL domain and 2B6 VH domain comprised a single amino acid modification (G105C and G44C, respectively) such that a glycine in each domain was replaced by cysteine. [00412] PCR and Expression Vector Construction; All PCR and PCR product purification protocols were as described hi Example 6.1 and 6.2 [00413] Overlapping PCR: Final products were constructed, amplified and purified using methods described in example 6.1 and example 6.2. [00414] Final products were cloned into pCIneo mammalian expression vector (Promega, Inc.) as previously described. The plasmid encoding constructs were designated as identified in Table 15: Table 15. PLASMID CONSTRUCTS (Table Removed) [00415] Polypeptide/diabody Expression: Three separate cotransfcctions in to in HEK-293 cells using Lipofectamine 2000, as described hi section 6.1, were performed: pMGX0669 and pMGX0719, encoding constructs 1 and 9, respectively; pMGX0669 and pMGX0718, encoding constructs 1 and 10, respectively; and pMGX0617 and pMGX0717, encoding constructs 11 and 12, respectively. Co-transfection of these plasmids was 'designed to lead to the expression of a bispecific diabody (CBD) of tetravalency with IgG- like structure, immunospccific for both FcyRIIB and FcyRIIIA. Following three days in culture, conditioned media was harvested. The amount of secreted product in the conditioned media was quantitiated by anti IgG Fc ELISA using purified Fc as a standard. The concentrations of product in the samples was then normalized based on the quantitation, and the normalized samples used for the remaining assays. [00416] ELISA: The binding of diabody molecules secreted into the medium was assayed by sandwich ELISA as described, supra. Unless indicated, CD32B was used to coat the plate, i.e., as the target protein, and HRP- conjugated CD 16 was used as the probe. [00417] Western Blot: Approximately 15 ml of conditioned medium form the three above-described cotransfections were analyzed by SDS-PAGE under non-reducing conditions. One gel was stained with Simply Blue Safestain (Invitrogen) and an identical gel was transferred to PVDF membrane (Invitrogen) using standard transfer methods. After transfer, the membrane was blocked with 5% dry skim milk in IX PBS. The membrane was then incubated in 10 ml of 1:8,000 diluted HRP conjugated Goat anti human IgGl H+L in 2% dry skim milk 1XPBS/0.1% Tween 20 at room temperature for 1 hr with gentle agitation. Following a wash with IX PBS/0.3% Tween 20, 2X 5 mm each, then 20 min at room temperature, the membrane was developed with ECL Western blotting detection system (Amersham Biosciences) according to the manufacturer's instructions. The film was developed in X-ray processor. [00418] Results [00419] Conditioned media from the recombinant expression systems comprising constructs 1 and 9; constructs 1 and 10; and constructs 11 and 12 were analyzed by SDS- PAGE (under non reducing conditions) analysis and Western-blotting (using an anti-IgG as the probe). Western blot revealed that the product from the systems comprising constructs 11 and 12 or comprising constructs 9 and 1 predominately formed a single species of molecule of approximately 150 kDa (FIG. 14, lanes 3 and 2, respectively). Both of these products have engineered internal disulfide bonds between the 'lighter' and 'heavier' chains comprising the diabody. In contrast, the molecule without engineered internal disulfide bonds between the 'lighter' and 'heavier' chains, formed of constructs 10 and 1, formed at least two molecular species of molecular weights -75 and ~100 kDa (FIG. 14, lane 1). [00420] Despite the results of the Western Blot, each of the three products was found capable of binding both CD32A and CD 16 (FIG. 15). Surprisingly, relative to the product comprising a C-temiinal hinge-Fc domain (formed of constructs 11 and 12), the product from both systems wherein the Fc (or Fc-hinge) domain was at the ammo terminus of the Fc containing polypeptide chain (i.e., the 'heavier' chain) (constructs 9+1 and constructs 10+1) demonstrated enhanced affinity and/or avidity to one or both of its target peptides (/. e. CD32B and/or CD16). 6.4 EFFECT OF INTERNAL/EXTERNAL CLEAVAGE SITE ON PROCESSING OF POLYPROTEIN PRECURSOR AND EXPRESSION OF COVALENT BISPECIFIC DIABODY; DESIGN AND CHARACTERIZATION OF BISPECIFIC DIABODY COMPRISING PORTIONS OF HUMAN IgG LAMBDA CHAIN AND HINGE DOMAIN [00421] As described herein, the individual polypeptide chains of the diabody or diabody molecule of the invention may be expressed as a single polyprotein precursor molecule. The ability of the recombinant systems described in Examples 6.1-6.3 to properly process and express a functional CBD from such a polyprotein precursor was tested by engineering a nucleic acid to encode, both the first and second polypeptide chains of a CBD separated by an internal cleavage site, in particular, a furin cleavage site. Functional, CBD was isolated from the recombinant system comprising the polyprotein precursor molecule. [00422] .As discussed in Example 6.3, addition of the 6 C-terminal amino acids from the human kappa light chain, FNRGEC (SEQ ID NO:23), was found to stabilize diabody formation — presumably through enhanced inter-chain interaction between the domains comprising SEQ ID N0:23 and those domains comprising an Fc domain or a hinge-Fc domain. The stabilizing effect of this lambda chain/Fc like interaction was tested in CBD wherein neither polypeptide chain comprised an Fc domain. One polypeptide chain of the diabody was engineered to comprise SEQ ID NO:23 at its C-terminus; the partner polypeptide chain was engineered to comprise the amino acid sequence VEPKSC (SEQ ID N0:79), which was derived from the hinge domain of an IgG. Comparison of this CBD to that comprised of constructs 1 and 2 (from example 6.1) revealed that the CBD comprising the domains derived from hinge domain and lambda chain exhibited slightly greater affinity to one or both of its target epitopes. [00423] Materials and Methods • Construction and Design of Polypeptide Molecides:_ Polyprotein precursor: Nucleic acid expression vectors were designed to produce 2 poyprotein precursor molecules, both represented chematically in FIG. 17. Construct 13 (SEQ ID N0:97) comprised from the N-termimis of the polypeptide chain, the VL domain of 3GS, the VH domain of 2.4G2 (which binds mCD32B), a furin cleavage site, the VL domain of 2.4G2 and the VH domain of 3G8. The nucleotide sequence encoding construct 13 is provided in SEQ SEQ ID N0:98. Construct 14 (SEQ ID N0:99) (FIG. 17), comprised from the N-terminus of the polypeptide chain, the VL domain of 3G8, the VH domain of 2.4G2 (which binds mCD32B), a furin cleavage site, a FMD (Foot and Mouth Disease Virus Protease C3) site, the VL domain of 2.4G2 and the VH domain of 3G8. The nucleotide sequence encoding construct 14 is provided in SEQ ID NO: 100. [00425] Nucleic acid expression vectors were designed to produce modified versions of constructs 1 and 2 presented in Example 6.1. Construct 15 (SEQ ID N0:101) (FIG. 17) was analagous to construct 1 (SEQ ID N0:9), presented in example 6.1, with the exception that the C-terminus of contract 15 comprised the amino acid sequence FNRGEC (SEQ ID N0:23). The nucleic acid sequence encoding construct 15 is provided in SEQ ID NO: 102. Construct 16 (SEQ ID NO: 103) (FIG. 17) was analogous to construct 2, presented in Example 6.1, with the exception that the C-terminus of construct 16 comprised the amino acid sequence VEPSK (SEQ ID N0:79). The nucleic acid sequence encoding construct 16 is provided in SEQ ID NO: 104. [00426] PCR and Expression Vector Construction; All PCR and PCR product purification protocols were as described in Example 6.1 and 6.2 [00427] Overlapping PCR: Final products were constructed, amplified and purified using methods described in example 6.1 and example 6.2 with appropriate primers [00428] Final products were cloned into pCIneo mammalian expression vector (Promega, Inc.) as previously described. The plasmid encoding constructs were designated as identified in Table 16: Table 16. PLASMID CONSTRUCTS (Table 16 Removed) [00429] Polypeptide/'diabody Expression: One transfection and one cotransfection into in HEK-293 cells using Lipofectamine 2000, as described in section 6.1, were performed: single: pMGX0750, encoding construct 13; and cotranfection: pMGX0752 and pMGX0753, encoding constructs 15 and 16, respectively. Following three days in culture, conditioned media was harvested, and secreted product affinity purified as described. [00430] ELISA: The binding of diabody molecules secreted into the medium was assayed by sandwich ELISA as described, supra. Murine CD32B was used to coat the plate, i.e., as the target protein, and HRP- conjugated CD16A was used as the probe for the product of the co-transfection of constructs 15 and 16. mCD32B was used as the target protein and biotin-conjugated CD16A was used as the probe for the recombinant system comprising construct 13. [00431] Results [00432] Conditioned media from the recombinant expression systems comprising constructs 13 was analysed by sandwich ELISA. The ELISA assay tested the binding of the CBD for specificity to either or both of mCD32B and/or CD16 (FIG. 18). CD32B served as the target antigen and GDI 6A was used as the secondary probe. The positive signal in the ELISA revealed that the heterodimeric h2.4G2-h3G8 CBD produced from the polyprotein precursor had specificity for both antigens. [00433] Similarly, the purified product generated by cotransfection of the vectors encoding constructs 15 and 16 was tested in an ELISA assay and compared to the product comprised of contructs 1 and 2 (Example 6.1). CD32B served as the target antigen and CD16A was used as the secondary probe. As with the product comprised of constructs 1 and 2, the product of constructs 15 and 16 was found to be capable of simultaneously binding CD32B and CD16A. In fact, the product of constructs 15 and 16 showed slightly enhanced affinity for one or both of the target antigens, i,e. CD32B or CD16A. This is perhaps due to increased stability and or fidelity (relative to a wild type VH-VL domain interaction) of the interchain association afforded by the interaction of the lambda chain region, FNRGEC (SEQ ID N0:23) and hinge region VEPKSC (SEQ ID NO:79), which is absent in the product comprised of constructs 1 and 2. [00434] Many modifications and variations of this invention can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. The specific embodiments described herein are offered by way of example only, and the Invention is to be limited only by the teims of the appended claims, along with the full scope of equivalents to which such claims are entitled. Such modifications are intended to fall within the scope of the appended claims. [00435] All references, patent and non-patent, cited herein are incorporated herein by reference in their entireties and for all purposes to the same extent as if each individual publication or patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety for all purposes. WE CLAIM: 1. A diabody molecule comprising a first polypeptide chain and a second polypeptide chain, wherein: (a) said first polypeptide chain comprises: (i) a first domain comprising a binding region of a light chain variable domain of a first immunoglobulin (VL1) specific for a first epitope, (ii) a second domain comprising a binding region of a heavy chain variable domain of a second immunoglobulin (VH2) specific for a second epitope, and (iii) a third domain comprising either a hinge region, an Fc domain or portion thereof, or both a hinge region and an Fc domain or portion thereof, which first domain and second domain are covalently linked such that the first domain and second domain do not associate to form an epitope binding site; and (b) said second polypeptide chain comprises: (i) a fourth domain comprising a binding region of a light chain variable domain of the second immunoglobulin (VL2), (ii) a fifth domain comprising a binding region of a heavy chain variable domain of the first immunoglobulin (VH1), and (iii) a sixth domair comprising either the amino acid sequence of at least the C-terminal 2 to 8 amino acid residues of a human light chain constant domain, or an Fc domain, which fourth domain and fifth domain are covalently linked such that the fourth domain and fifth domain do not associate to form an epitope binding site; and wherein: (1) said first domain and said fifth domain associate to form a first binding site (VL1)(VH1) that binds said first epitope; and (2) said second u main and said fourth domain associate to form a second binding site (VL2)(VH2) that binds the second epitope. 2. A diabody molecule comprising a first polypeptide chain and a second polypeptide chain, wherein: (a) said first polypeptide chain comprises: (i) a first domain comprising a binding region of a light chain variable domain of a first immunoglobulin (VL1) specific for a first epitope, (ii) a second domain comprising a binding region of a heavy chain variable domain of a second immunoglobulin (VH2) specific for a second epitope, and (iii) a third domain comprising either a hinge region, an Fc domain or portion thereof, or a hinge region and an Fc domain or portion thereof, which first domain and second domain are covalently linked such that the first domain and second domain do not associate to form an epitope binding site; and (b) said second polypeptide chain comprises: (i) a fourth domain comprising a binding region of a light chain variable domain of the second immunoglobulin (VL2), (ii) a fifth domain comprising a binding region of a heavy chain variable domain of the first immunoglobulin (VH1), which fourth domain and fifth domain are covalently linked such that the fourth and fifth domains do not associate to form an epitope binding site; and wherein: (1) said first domain and said fifth domain associate to form a first binding site (VL1)(VH1) that binds said first epitope; (2) said second domain and said fourth domain associate to form a second binding site (VL2)(VH2) that binds the second epitope; and (3) said third domain is N-terminal to both the first domain and the second domain. 3. The diabody molecule of claim 1 or 2, wherein the first polypeptide chain and the second polypeptide chain are covalently linked via at least one disulfide bond between at least one cysteine residue outside of the first domain and the second domain on the first polypeptide chain and at least one cysteine residue outside of the fourth domain and the fifth domain on the second polypeptide chain. 4. The diabody molecule of any of claims 1, 2, or 3 wherein said molecule comprises at least one amino acid modification of the first domain relative to a wild-type first domain and at least one amino acid modification of the fifth domain relative to a wild-type fifth domain, which said at least one amino acid modification in each of the first domain and fifth domain comprises a substitution with cysteine such that first polypeptide chain and the second polypeptide chain are covalently linked via a disulfide bond between said substituted cysteine residue in the first domain and said substituted cysteine residue in the fifth domain. 5. A diabody molecule comprise. i a first and a second polypeptide chain, wherein: (a) said first polypeptide chain comprises: (i) a first domain comprising a binding region of a light chain variable domain of a first immunoglobulin (VL1) specific for a first epitope, and (ii) a second domain comprising a binding region of a heavy chain variable domain of a second immunoglobulin (VH2) specific for a second epitope, which first domain and seco, d domain are covalently linked such that the first domain and second domain do not associate to form an epitope binding site; and (b) said second polypeptide chain comprises: (i) a third domain comprising a binding region of a light chain variable domain of the second immunoglobulin (VL2), and (ii) a fourth domain comprising a binding region of a heavy chain variable domain of the first immunoglobulin (VH1), which third domain and fourth domain are covalently linked such that the third domain and fourth domain do ;\ot associate to form an epitope binding site; and wherein: (1) said first domain and said third domain associate to form a first binding site (VL1)(VH1) that binds the first epitope, which epitope binding site is specific for CD32B; (2) said second domain and said fourth domain associate to form a second binding site (VL2)(VH2) that binds the second epitope, which epitope binding site is specific for CD 16; and (3) said first polypeptide chain and said second polypeptide chain are covalently linked via a disulfide bond between at least one cysteine residue outside of the first domain and the second domain on the first polypeptide chain and at least one cysteine residue outside of the third domain and the fourth domain on the second polypeptide chain, which cysteine residue on the first polypeptide chain is not at the C-terminus of the first polypeptide chain and cysteine residue on the second polypeptide chain is not at the C-terminus of the second polypeptide chain, 6. The diabody molecule of any of claims 1-5, wherein the first immunoglobulin or second immunoglobulin is a human immunoglobulin, which human immunoglobulin is an IgA, IgE, IgD, IgG or IgM. 7. The diabody molecule of claim 6, wherein the human immunoglobulin is an IgG, which IgG is selected from the list consisting of IgG 1, IgG2, IgG3 and IgG4. 8. The diabody molecule of any of claims 1-7, wherein the Fc domain is a human Fc domain. 9. The diabody molecule of any of claims 1-8, wherein at least one epitope binding site is specific for an FcyRI, FcyRII or FcyRIII receptor. 10. The diabody molecule of claim 9, wherein the Fey receptor is a FcyRIII receptor, which FcyRIII receptor is FcyRIIIA (CD16A) receptor or FcyRIIIB (CD16B) receptor. 11. The diabody molecule of claim 10, wherein the FcyRIII receptor is FcyRIIIA (CD 16A) receptor. 12. The diabody molecule of claim 9, wherein the Fey receptor is a FcyRtl receptor, which FcyRII receptor is FcyRII A (CD32A) receptor or Fey RUB (CD32B) receptor. 13. The diabody molecule of claim 12, wherein the FcyRII receptor is the FcyRIIB (CD32B) receptor. 14. The diabody molecule of any of claims 1-13, wherein the second epitope binding site is specific for a pathogenic antigen. 15. The diabody molecule of any of claims 1-13, wherein the second epitope binding site is specific for a toxin or a drug. 16. The diabody molecule of claim 9, wherein said diabody has an epitope binding site specific for CD32B and an epitope binding site is specific for CD16A. 17. The diabody molecule of any f>f claims 1-2, wherein the third domain comprises a variant Fc region, which variant Fc region comprises at least one amino acid modification relative to the wild type Fc region. 18. The diabody molecule of any of claims 1-17, which molecule is a dimer, said dimer comprising (a) a first monomer comprising a set of said first polypeptide chain and said second polypeptide chain; and (b) a second monomer comprising a set of said first polypeptide chain and said second polypeptide chain wherein said first and second monomers are covalently linked via at least one disulfide bond between at least one cysteine residue in the third domain of the first polypeptide chain of each monomer. 19. A nucleic acid molecule comprising a nucleotide sequence encoding the first polypeptide chain of the diabody molecule of any of claims 1-18. 20. A nucleic acid molecule comnrising a nucleotide sequence encoding the second polypeptide chain of the diabody molecule of any of claims 1-18. 21. A host cell comprising the nucleic acid molecule of claim 19 or 20. |
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| Patent Number | 278072 | |||||||||
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| Indian Patent Application Number | 8211/DELNP/2007 | |||||||||
| PG Journal Number | 52/2016 | |||||||||
| Publication Date | 16-Dec-2016 | |||||||||
| Grant Date | 09-Dec-2016 | |||||||||
| Date of Filing | 24-Oct-2007 | |||||||||
| Name of Patentee | MACROGENICS, INC. | |||||||||
| Applicant Address | 1500 EAST GUDE DRIVE, ROCKVILLE, MARYLAND 20850-5307, U.S.A. | |||||||||
Inventors:
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| PCT International Classification Number | A61K 39/395 | |||||||||
| PCT International Application Number | PCT/US2006/014481 | |||||||||
| PCT International Filing date | 2006-04-17 | |||||||||
PCT Conventions:
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