Other mammalian histocompatibility systems. Skin graft rejection and graft-versus-host reaction across I-subregion differences: are there many more than three H loci within the H-2 complex?

The data confirm an earlier finding by Klein et al. that the I region harbors a strong histocompatibility locus, which by exclusion might be assigned to the IA subregion. In addition, it appears that intercalated between the IA subregion and S region there is a minor H locus since (DBA/2 X 4R)F1 rejects skin of 2R in a chronic fashion. In another combination, HTT versus 7R, which differs for the IC, S, and G regions but may also differ for genes between the D and TL locus, a similar chronic rejection pattern was observed indicating minor H gene(s) within or closely linked to the H-2 complex. The data reported here are in concordance with very recently published results by Klein et al..