The functional helper T cell repertoire specific for L-glutamic acid60-L-alanine30-L-tyrosine10 (GAT).

Experiments have been carried out to examine the potential helper T cell repertoire specific for the random terpolymer GAT on responder, nonresponder, and (responder x nonresponder)F1 murine strains. The ability of GAT-MBSA immunized T cells to collaborate with DNP-specific primary and secondary B lymphocytes of each strain in response to the antigen DNP-GAT was tested with the splenic fragment culture system. The results of these experiments show that there are GAT-specific T lymphocytes in the responder, nonresponder, and F1 strains but that these 3 GAT-specific T cell populations differ in their collaborative potential. In sum, these findings present new evidence that the nonresponder status to the terpolymer GAT is due, in part, to a functional deletion of helper T cells capable of recognizing the antigen in the context of the nonresponder haplotype. Further, a new responsive phenotype is evidenced when F1 secondary B cells are stimulated in nonresponder GAT-MBSA-primed recipients. In this case, rather than the IgG1 responses observed in such strain combinations to other antigens such as DNP-Hy or DNP-Gl phi 9, only IgM responses were obtained. This new phenotype may be the result of GAT-specific suppression of isotype switching by B cells bearing the nonresponder cell surface alloantigens.