Studies on fd fragments of human immunoglobulins. III. Immunogenic properties of gamma chains, myeloma fd gamma, and myeloma fd1 alpha.

Earlier studies on antisera against Fab of pooled human IgG and IgA myeloma proteins disclosed the presence of class-specific Fd antibodies, the demonstration of which required interaction of heavy and light chains. To extend our knowledge about the antigenic structure of the Fd fragment of human immunoglobulins, antisera were prepared in rabbits against gamma chains of pooled IgG and of four IgG1 myeloma proteins, and Fd gamma fragment and a cyanogen bromide-produced CH1 preparation of an IgG1 myeloma protein, and an Fd' alpha fragment of an IgA1 myeloma protein. No antigenic determinants exclusively confined to the CH1 region of intact human IgG could be demonstrated with these antisera. The antigenic structure of CH1 intact immunoglobulins may thus only be defined by light-chain-dependent determinants.