Separation of the immune response genes for LDH-B and MOPC-173. I. Description of an immune response defect in B10.BASR1.

Abstract

By using the intra-I-region recombinant mouse strain, B10.BASR1 (H-2as4), the immune response (Ir) genes for LDH-B and MOPC-173 were genetically and serologically separated, as assayed by T cell proliferation. Previous work demonstrated that the H-2s and H-2b strains respond to LDH-B and MOPC-173, whereas the H-2a and H-2k strains failed to respond due to haplotype-specific suppression of I-Ak-activated T helper cells by I-Ek-activated T suppressor cells. In the experiments reported here, B10.BASR1 mice, which lack I-Ek expression, mounted a significant T cell proliferative response to MOPC-173 but not to LDH-B. Separation of the Ia determinants used in restricting these two antigen responses was further confirmed when pretreatment of B10.S(9R) (A alpha sA beta sE beta sJk) macrophages with A.TL anti-B10.HTT (anti-A beta sE beta sJs) serum absorbed with B10.BASR1 spleen cells blocked the LDH-B response but not the MOPC-173 response. Unabsorbed serum blocked both antigen responses. The primary immunogenic determinant recognized by LDH-B or MOPC-173 immune T cells was not present on both antigens, as MOPC-173-primed T cells and LDH-B-primed T cells responded only to the priming antigen. Lastly, by using the A beta mutant strain, B6CH-2bm12, it was shown that the Ir gene and Ia determinants affected by this mutation had no effect on the LDH-B and MOPC-173 proliferative responses. These results suggest the possibility of an intragenic recombinatorial event in either the A alpha or A beta chain resulting in the separation of these two immune response gene functions.