IR GENE-FUNCTION IN AN I-A SUBREGION MUTANT B6.C-H-2BM12

The B6.C-H-2bm12 (bm12) [mouse] strain has a mutation in the I-A subregion of the murine H-2 complex; it is characterized by a loss of serologically detected Ia antigens, and a strong graft rejection and mixed lymphocyte response between parent and mutant. It was presumed that the mutation affected the Ia-l gene, and to determine the relationship of Ia antigens and Ir genes, the immune responses of mutant and parent were compared. The immune responses to poly-(LTyr,LGlu)-poly(DLAla).sbd.poly(LLys), poly(Phe,Glu)poly(DLAla).sbd.poly(LLys), and poly(His,Glu)-poly(DLAla).sbd.poly(LLys) in parent and mutant were the same, indicating that Ia-l and the Ir genes for these antigens are not identical. By contrast, C57BL/6 gave a good response; the mutant strain, however, was unable to generate cytotoxic T lymphocytes to the male-specific H-Y antigen-a response under I-A subregion Ir gene control, which now must be considered to be the Ia-l gene. Complementary Ir genes in the H-2b haplotype for the H-Y immune response could be detected when the bm12 mutant was used.