Asymmetry in the serological response and mixed lymphocyte reactions between C57Bl/6 and the congenic mutant C57Bl/6.CH-2ba [H(Zl)].

Asymmetry in the relationship between the H-2K mutant strain C57Bl/6.CH-2ba (H-2ba) and the wild-type congenic C57Bl/6 has been demonstrated both in MLR and serologically by haemagglutination. MLR between these strains, when B6 was the responder, was as strong as that toward allogeneic stimulator cells: H-2ba was regularly less responsive toward B6. Responses in both directions were increased, in terms of augmented proliferative responses, by prior immunization. In this context the MLR resembles that towards minor H-locus antigens rather than those controlled by the H-2 locus. Immunization of (H-2ba X BALB/c)F1 hybridgs with B6 lymphoid cells induced the production of a haemagglutinating antibody not directed toward any known H-2 specificity. The B6 haemagglutinogen, termed He, was present on B6 lymphoid as well as red blood cells. Segregation studies of F2 and back-cross progeny of (H-2ba X BALB/c)F1 hybrids suggest that the response to He is controlled by two Ir genes, one of which is linked to H-2.