Heterogeneity of HLA-DR4 in the rheumatoid arthritis of a Chippewa band.

A high frequency of both rheumatoid arthritis (RA) and HLA-DR4 was found in a Chippewa Indian population. Multiple immunogenetic "variants" of HLA-DR4 were demonstrated, each showing a different response in mixed lymphocyte culture which corresponded to a serologic pattern of reactivity to a panel of non-DR4 B cell alloantisera. No DR4-bearing HLA haplotype or DR4 "variant" was common to subjects with RA, all of whom were DR4-positive. The implications are discussed.