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.