The MHC-E locus is the most well conserved of all known primate class I histocompatibility genes

Leslie A. Knapp, Luis F. Cadavid, David I. Watkins

Research output: Contribution to journalArticlepeer-review

67 Scopus citations


The HLA-E locus is characterized by limited polymorphism and low levels of cell surface expression. However, the function of the products of this nonclassical MHC class I gene remains unknown. To evaluate the conservation of the MHC-E locus throughout anthropoid primate evolution, we identified the homologue of the HLA-E locus in six different New World monkey species. Full- length sequencing of MHC-E cDNAs in four unrelated cotton-top tamarins (Saguinus oedipus) revealed no evidence for polymorphism. Using the PCR, denaturing gradient gel electrophoresis, and direct sequencing, we also identified MHC-E alleles in five other New World monkey species, representing all extant platyrrhine families. In contrast to all other classical and nonclassical MHC class I genes in primates, the rate of synonymous nucleotide substitution is much greater than the rate of nonsynonymous nucleotide substitution within exons 2 and 3 encoding the peptide binding region (PBR) in MHC-E genes. The PBR of the MHC-E molecule, therefore, has evolved under purifying selective pressures, and the very unusual evolutionary history of this ancient gene provides further evidence that the products of the HLA-E locus serve a critical immunological function. Given the remarkable conservation of the PBR during primate evolution, this critical immunological function is probably related to the peptide binding ability of the MHC-E protein.

Original languageEnglish (US)
Pages (from-to)189-196
Number of pages8
JournalJournal of Immunology
Issue number1
StatePublished - Jan 1 1998
Externally publishedYes

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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