Immune Response of Mice to Thy-1.1 Antigen: Genetic Control by Alleles at the <i>Ir-5</i> Locus Loosely Linked to the <i>H-2</i> Complex

Abstract

Abstract The primary response of mice to Thy-1.1 antigen was measured by means of a plaque assay detecting cells which produce antibodies lytic for AKR thymocytes. It was found that F1 hybrids between the low responder strains C57BL/6J, C57BL/10J, or B10.T and the DBA/2J strain produced significantly more plaque-forming cells per spleen than either parental strain. In backcross populations of these three F1 hybrids to C57BL/6J, C57BL/10J, or B10.T parents, 16.1 to 21% of H-2 heterozygotes were low responders as was the H-2 homozygous parent. These low responder H-2 heterozygotes, when mated to the C57BL/6J parent, produced 70.2% low responder H-2 heterozygotes, whereas when mated to the DBA/2J parent they produced only 5.7% low responder H-2 heterozygotes. The data obtained were interpreted as evidence for the existence of the locus designated Ir-5, which participates in the control of the immune response to the Thy-1.1 antigen together with loci belonging to the I region of the H-2 complex designated Ir-Thy-1. From the recombination frequency between the Ir-5 locus, the H-2 complex, and the T locus in the (B10.T × DBA2/J)F1 × B10.T backcross population, the relative position of the Ir-5 locus has been estimated. This locus falls about 19 map units to the right of the H-2 complex.