The Common Marmoset: A New World Primate Species with Limited Mhc Class II Variability

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 95; no. 20; pp. 11745 - 11750
• Main Authors: Antunes, Susana G., de Groot, Natasja G., Brok, Herbert, Doxiadis, Gaby, Alexandre A. L. Menezes, Otting, Nel, Bontrop, Ronald E.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 29.09.1998; National Acad Sciences; National Academy of Sciences
• Subjects: Alleles; Amino Acid Sequence; Animals; Base Sequence; Biological Sciences; Callithrix - genetics; Callithrix - immunology; Chimera - genetics; Chimera - immunology; Conserved Sequence; Disease; DNA - genetics; DNA Primers - genetics; Evolution; Exons; Female; Genes, MHC Class II; Genetic loci; Genetic Variation; Genetics; Haplotypes; Histocompatibility Antigens Class II - genetics; Infections; Male; Molecular Sequence Data; Molecules; Monkeys; Nucleotide sequences; Phylogeny; Polymerase Chain Reaction; Polymorphism, Genetic; Primates; Sequence Homology, Amino Acid; Sequence Homology, Nucleic Acid; T lymphocytes
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.95.20.11745

The common marmoset (Callithrix jacchus) is a New World primate species that is highly susceptible to fatal infections caused by various strains of bacteria. We present here a first step in the molecular characterization of the common marmoset's Mhc class II genes by nucleotide sequence analysis of the polymorphic exon 2 segments. For this study, genetic material was obtained from animals bred in captivity as well as in the wild. The results demonstrate that the common marmoset has, like other primates, apparently functional Mhc-DR and -DQ regions, but the Mhc-DP region has been inactivated. At the -DR and -DQ loci, only a limited number of lineages were detected. On the basis of the number of alleles found, the -DQA and -B loci appear to be oligomorphic, whereas only a moderate degree of polymorphism was observed for two of three Mhc-DRB loci. The contact residues in the peptide-binding site of the Caja-DRB1*03 lineage members are highly conserved, whereas the -DRB*W16 lineage members show more divergence in that respect. The latter locus encodes five oligomorphic lineages whose members are not observed in any other primate species studied, suggesting rapid evolution, as illustrated by frequent exchange of polymorphic motifs. All common marmosets tested were found to share one monomorphic type of Caja-DRB*W12 allele probably encoded by a separate locus. Common marmosets apparently lack haplotype polymorphism because the number of Caja-DRB loci present per haplotype appears to be constant. Despite this, however, an unexpectedly high number of allelic combinations are observed at the haplotypic level, suggesting that Caja-DRB alleles are exchanged frequently between chromosomes by recombination, promoting an optimal distribution of limited Mhc polymorphisms among individuals of a given population. This peculiar genetic make up, in combination with the limited variability of the major histocompatability complex class II repertoire, may contribute to the common marmoset's susceptibility to particular bacterial infections.