Specificity of antibody and helper T-cell responses to the isologous myeloma protein W3129 and its subunits.

The specificity of BALB/c antibodies and Th elicited by BALB/c myeloma protein W3129 (alpha, kappa) and its subunits was studied. Antibodies were detected with RIA and ELISA techniques. Th were demonstrated by their ability to augment a secondary anti-NIP antibody response in a Mitchison type assay of adoptive immunity. The major proportion of antibodies elicited by the complete W3129 was directed to an idiotypic determinant(s) that depended on assembled H + L chains. The determinant(s) was probably located in or near the antibody combining site because binding was hapten-inhibitable. A second minor antibody population bound an idiotypic determinant(s) on VW3129H expressed on isolated H-chain as well as on the complete myeloma protein. A third and very weakly reactive set of antibodies was specific for a C alpha antigenic site(s) which was expressed much more efficiently on free than on assembled alpha-chains. The antibody response to free kappa W3129 was directed to idiotypic determinants that were inaccessible in the complete molecule. By contrast, free kappa W3129 elicited Th that responded to an idiotypic determinant(s) on VW3129K; the determinant(s) was expressed on both the isolated chain and the complete W3129, suggesting that Th responded to an idiotope not recognized by B-cells. Priming with free alpha W3129 failed in four out of five experiments to induce Th that responded to the complete W3129, demonstrating that a major difference existed between VH and VL of W3129 regarding their immunogenicity for Th. Nevertheless, free alpha W3129 did elicit antibody responses that displayed high reactivity with the complete molecule, indicating that certain serologically defined antigenic sites on the surface of W3129 are also expressed on isolated alpha W3129. Thus, certain differences were detected as to the specificities of Th and B-cells for W3129 and its subunits since they recognized separate idiotopes located in the VL- or VH-region, respectively. The pattern of Th recognition of W3129 resembled that of another isologous myeloma protein, M315, but was unlike that of a third, J558, previously described from this laboratory.