Abstract: The invention features methods of producing an antibody in the milk of a transgenic mammal. The methods include providing a transgenic mammal whose somatic and germ cells comprise a sequence encoding an exogenous heavy chain variable region or antigen binding fragment thereof, at least one heavy chain constant region, or a fragment thereof, and a hinge region, operably linked to a promoter which directs expression in mammary epithelial cells, wherein said hinge region has been altered from the hinge region normally associated with the heavy chain constant region. The invention also features transgenic mammals, methods of producing these mammals, compositions comprising such antibodies, and nucleic acids encoding the antibodies.

Abstract: The current invention features methods for reliably and controllably separating immunoglobulin half antibodies from immunoglobulin whole antibodies, as well as purified immunoglobulin half antibody preparations and purified immunoglobulin whole antibody preparations while preserving biological activity. These dissociated half antibodies can be chromatographically separated from whole antibodies. There are four known subclasses of IgG molecules: IgG1; IgG2; IgG3; and IgG4. IgG4 molecules differ from the other IgG isotypes in that the disulfide bonds that link the two heavy chain subunits together do not always form. Due to the non-covalent interactions that hold the heavy chain subunits together, the heterogeneity of IgG4 molecules is not apparent following gel filtration of purified IgG4 protein.