Unprecedented polymorphism of Mhc-DRB region configurations in rhesus macaques.

The rhesus macaque is an important model in preclinical transplantation research and for the study of chronic and infectious diseases, and so extensive knowledge of its MHC (MhcMamu) is needed. Nucleotide sequencing of exon 2 allowed the detection of 68 Mamu-DRB alleles. Although most alleles belong to loci/lineages that have human equivalents, identical Mhc-DRB alleles are not shared between humans and rhesus macaques. The number of -DRB genes present per haplotype can vary from two to seven in the rhesus macaque, whereas it ranges from one to four in humans. Within a panel of 210 rhesus macaques, 24 Mamu-DRB region configurations can be distinguished differing in the number and composition of loci. None of the Mamu-DRB region configurations has been described for any other species, and only one of them displays major allelic variation giving rise to a total of 33 Mamu-DRB haplotypes. In the human population, only five HLA-DRB region configurations were defined, which in contrast to the rhesus macaque exhibit extensive allelic polymorphism. In comparison with humans, the unprecedented polymorphism of the Mamu-DRB region configurations may reflect an alternative strategy of this primate species to cope with pathogens. Because of the Mamu-DRB diversity, nonhuman primate colonies used for immunological research should be thoroughly typed to facilitate proper interpretation of results. This approach will minimize as well the number of animals necessary to conduct experiments.