Studies on the antigenic properties of the Fd-fragment of a human G-myeloma protein (Daw)

The present investigation deals with an immunochemical approach in studies on the structure of Fd-fragments of human immunoglobulins. Rabbits were immunized with a preparation of Fd-fragment of a human G-myeloma protein (Daw) [1]. Detailed studies on the reactions of the rabbit antiserum with a panel of antigens demonstrated that antibodies were obtained against an idiotypic site on the Fd- or the Fab-fragment of the Daw immunoglobulin molecule. No antibodies against any common region of the Fd-fragment could be detected in immunodiffusion experiments with the antigens used, a finding confirmed by the outcome of various haemagglutinating experiments. Structural implications of these findings are discussed.