Genetic mapping and immunogenetic characterization of theH- 2(fb) mutation in the mouse

Rejection of tailskin grafts exchanged between two male hybrids of the cross B10.M × B10.RIII(71NS) revealed a mutation in theH-2 ( f ) haplotype from the B10.M congenic line. Complementation studies with skin grafting and cell-mediated lympholysis showed the mutant, namedH-2 ( fb ), to be different from anotherH-2 ( f ) mutant,H-2 ( fa ), and further, that the HH-2 ( fb ) mutation occurred in theD end of theH-2 complex. Reciprocal skin grafts exchanged between mutant and normal mice were rejected. Hemagglutinating antibody reactive with B10.M cells was raised in the mutant mice. Mutant spleen cells responded weakly, but significantly, to wild-type cells in a mixed lymphocyte culture and in a graftversus-host assay, but no response was seen in the opposite direction. However, cytotoxic effector cells were generated against target cells in both directions in a cell-mediated lympholysis assay.