Abstract: Methods for producing and using bispecific antibodies formed by leucine zippers are provided. Leucine zippers capable of preferentially forming heterodimers are respectively linked to epitope binding components comprising different binding specificities. Bispecific antibodies are formed by pairwise association of the leucine zippers, forming a heterodimer which links the two distinct epitope binding components. Heterodimerization can occur by interaction of the two leucine zipper regions, forming a bispecific antibody. Such a bispecific antibody may be further stabilized by the formation of intermolecular chemical bonds, such as disulfide bonds, between the two monomeric subunits. Subsequent to the formation of such intermolecular bonds between the monomeric subunits, the leucine zippers may be removed or retained. Bispecific antibodies produced by these methods are substantially pure and may be produced in high yields and on a large scale.

Abstract: The invention provides mutated IgG2 constant regions and anti-CD3 antibodies incorporating the same. Such antibodies specifically bind to the CD3 antigen on T-cells but induce reduced mitogenic response compared with otherwise identical antibodies bearing natural IgG2 constant regions. The antibodies can be used for treating disorders requiring immune suppression with fewer side effects than result from treatment with prior anti-CD3 antibodies.