Expression of the W6/32 HLA epitope by cells of rat, mouse, human and other species: critical dependence on the interaction of specific MHC heavy chains with human or bovine beta 2-microglobulin.
The HLA class I epitope W6/32 is conformationally dependent on both heavy chain and beta 2-microglobulin (beta 2M). Previously, the W6/32 epitope has been detected in humans and other primates as well as from bovine sources. Two controversial reports suggest the W6/32 epitope is constitutively expressed by either normal or transformed murine cells expressing the Db allele. Here we show that the appearance of the W6/32 epitope in murine cells results from the association of either the Db or Kd gene products with either bovine or human beta 2M. We use congenic mouse strains and hybrid H-2 class I genes between Db and Kb to map the W6/32 epitope to particular amino acid residues in the alpha 2 domain. Subsequently, we show that beta 2M exchange is not confined to murine or human cells in vitro but can be detected after beta 2M injection into a mouse. The data presented suggests that beta 2M exchange takes place at the cell surface under physiological conditions and indicates that MHC class I heavy chains are in an equilibrium between the bound and unbound form of beta 2M.
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D000939:Epitopes / Q000096:biosynthesis / Q000235:genetics* / Q000276:immunology; D005786:Gene Expression Regulation; D005805:Genes, MHC Class I; D006183:H-2 Antigens / Q000235:genetics; D006680:HLA Antigens / Q000096:biosynthesis / Q000235:genetics* / Q000276:immunology; D006801:Humans; D007739:L Cells; D051379:Mice; D008969:Molecular Sequence Data; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D013045:Species Specificity; D001613:beta 2-Microglobulin / Q000502:physiology*
D000939:Epitopes; D006183:H-2 Antigens; D006680:HLA Antigens; D011994:Recombinant Proteins; D001613:beta 2-Microglobulin