Unusual HLA-DR,DQ haplotypes found in South African families of black, Asian Indian, and mixed ancestral origin.

Four non-Caucasoid families with the unusual HLA-DR,DQ haplotypes DRw17,DQw7; DR9,DQw2; DR4,DQw2; and DR4,DQw5 were studied. All four haplotypes showed identical serological patterns to those seen with the equivalent Caucasoid antigens, but no HLA-Dw specificities could be assigned. TaqI restriction fragment length polymorphism (RFLP) patterns observed using DRB, DQB, and DQA probes showed that the DRw17,DQw7 haplotype may have originated from a homologous crossover between a DRw17,DQw2 haplotype and a haplotype with DQw7. The results obtained for the DR9,DQw2 and DR4,DQw2 haplotypes suggest that these could have resulted from recombination events with an ancestral "black" DQw2 haplotype. From the RFLP data, it is difficult to postulate the origin of the DR4,DQw5 haplotype being from a single recombination event.