Sharing of Individual Antigenic Determinants Between a  G and a  M Protein in the Same Myeloma Serum

Two lambda proteins, one a γM and the other a γG3, were isolated from the same human myeloma serum and were shown to share individual antigenic (idiotypic) specificity when tested with several antisera prepared against the intact proteins and pepsin digested fragments. These shared determinants were localized to the heavy chains and the combinational structure of the heavy plus light chains. Shared individual determinants of the light chains were also demonstrated utilizing antisera prepared against the isolated light chains. These results indicate that the light chains and the variable regions of the heavy chains of the two proteins are extremely similar. The peptide map and mobility differences in the light chains indicate that they are not identical.