Immune response of mice to the Thy 1.1 antigen: intra H 2 mapping of the complementary Ir Thy 1 loci

The primary immune response to the Thy 1.1 antigen was measured by a plaque assay that detected cells producing antibodies lytic for AKR thymocytes. F₁ hybrids which were b/d heterozygous at the entire H 2 complex or at only some of its regions were studied. All F₁ hybrids which were b/d heterozygotes at the K, IA and possibly IB regions displayed a complementary effect of the alleles at the Ir Thy 1A and Ir Thy 1B loci. The complementary effect was indicated by the significantly higher responses of the F₁ hybrids than the responses of their parental strains. No complementary effect could be demonstrated in F₁ hybrids which were b/d heterozygous at the IB IC, S and D regions, but not at the K and IA regions. The results excluded participation of the IC, S and D regions in the phenomenon of the complementation. Furthermore, one of the Ir Thy 1 loci could be mapped to the left of the IB subregion, most likely in the IA subregion of the H 2 complex. The second Ir Thy 1 locus could be mapped to the left of the IC subregion in either the IA or IB subregion.