A new minor histocompatibility locus linked to H-3.

B10, BALB.B, and A.BY shared an allele at a new locus not shared by B10.LP-H-3b. This locus is linked to the minor histocompatibility gene, H-3, in the 5th linkage group of chromosome 2 of the mouse. The product of the new gene fits the criteria of a minor histocompatibility antigen, since it induced as well as served as a target for cytotoxic lymphocytes (CTL) and its presence accelerated skin graft rejection when compared with that caused by H-3.1. F1 complementation of skin graft rejection and generation of CTL indicated that A.BY and BALB.B do not share H-3a with B10 as previously reported but possess the c allele of their congenic partners A and BALB/c. Thus, B10.LP-H-3b and B10 differ from one another by at least 2 minor histocompatibility loci. The specificity of CTL developed in B10. LP-H-3b and appropriate F1 hybrids indicate that the lytic activity of CTL specific for H-3.1 was restricted to target cells possessing H-2Kb antigens; this contrasted to the H-2Db-restricted activity of CTL specific for the product of the new gene.