Evidence for an HLA-C-like locus in the orangutan Pongo pygmaeus

HLA-B and C are related class I genes which are believed to have arisen by duplication of a common ancestor. Previous study showed the presence of ort hologues for both HLA-B and C in African apes but only for HLA-B in Asian a pes. These observations suggested that the primate C locus evolved subseque nt to the divergence of the Pongidae and Hominidae. From an analysis of ora ngutan Tengku two HLA-C-like alleles (Popy C*0101 and Popy C*0201) were def ined as well as three HLA-B-like (Popy-B) alleles. By contrast, no Popy-C a lleles were obtained from orangutan Hati, although three Popy-B alleles wer e defined, Thus an HLA-C-like locus exists in the orangutan (as well as a d uplicated B locus), implying that the primate C locus evolved prior to the divergence of the Pongidae and Hominidae and is at least 12-13 million year s old. Uncertain is whether all orangutan MHC haplotypes contain a C locus, as the failure to find C alleles in some individuals could be due to a mis pairing of HLA-C-specific primers with certain Popy-C alleles, These result s raise the possibilities that other primate species have a C locus and tha t the regulation of natural killer cells by C allotypes evolved earlier in primate evolution than has been thought.