Common individual antigenic determinants in five of eight BALB-c IgA myeloma proteins that bind phosphoryl choline.

Eight IgA myeloma proteins derived from independently induced plasma-cytomas in genetically similar inbred BALB/c mice are functionally related by their binding of phosphoryl choline-containing antigens (Pneumococcus C polysaccharide or Lactobacillus antigen). Each protein resembles a single species of immunoglobulin in antibody. The proteins are characterized by highly sensitive myeloma-specific antisera prepared by immunizing mice of other inbred strains with the BALB/c myeloma proteins. Individual or myeloma-specific determinants located on Fab fragments were found on three of the proteins that were unique for that protein and did not react with any other IgA protein among over 70 tested. Remarkably, five of the proteins shared two common myeloma-specific determinants which were specific for this group of five proteins. These results suggest that the five functionally and genetically related proteins sharing the same myeloma-specific determinants might also be structurally similar.