Immunogenetic analysis of H-2 mutations. IV. Mapping of and immune reactions to the H-2fa mutation.

H-2fa is a spontaneous mutation that occurred in an (A.CA X A)F1 female mouse and was later transferred on an A-strain background [congenic line A.CA (M506) or M506]. Skin grafts exchanged between M506 and A.CA strains are rejected within 4 weeks after grafting. Significant reaction is observed when these two strains are used as responders and stimulators in mixed lymphocyte culture or in a splenomegaly graft-versus-host assay. The mutant antigen induces strong cell-mediated lymphocytotoxicity. The mutation maps in the K end of the H-2 complex. The capacity of mutant antigens to induce relatively strong lymphocyte proliferation is explained by hypothesizing that the T-cell receptors reacting with K- or D-region products can more easily recognize subtle than drastic alloantigenic differences.