Unexpected expression of a unique mixed-isotype class II MHC molecule by transfected L-cells.
Class II (Ia) major histocompatibility complex (MHC) molecules are heterodimeric integral membrane proteins composed of non-covalently linked alpha and beta glycoprotein chains. Studies of both normal cells and L-cell transfectants have shown that neither alpha- nor beta-chains are found on the cell surface alone, and that alpha beta dimers are required for membrane expression. In both mouse and man, several distinct non-allelic alpha and beta genes exist. Analysis of Ia molecules by immunoprecipitation and two-dimensional gel electrophoresis has demonstrated apparently selective association of particular pairs of the various alpha- and beta-chains to form the expressed class II isotypes I-A and I-E (mouse) or DQ, DP and DR (human). Because the various alpha- or beta-chains encoded by distinct loci exist in many allelic forms within a species, such specific pairing suggests a special role for isotypically conserved regions of each chain in the association process. In attempting to localize such putative assembly-controlling regions using the technique of DNA-mediated gene transfer, various combinations of murine alpha and beta genes were introduced into L-cells. Here we report the unexpected observation, following transfection, of mixed-isotype (Ad beta Ea/k alpha) molecules on the L-cell membrane and document that the formation of this pair is strongly influenced by allelic polymorphism of the A beta chain.
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D000595:Amino Acid Sequence; D000818:Animals; D000954:Antigens, Surface / Q000235:genetics; D005786:Gene Expression Regulation; D006579:Heterozygote; D000949:Histocompatibility Antigens Class II / Q000235:genetics*; D007739:L Cells / Q000276:immunology; D046911:Macromolecular Substances; D008285:Major Histocompatibility Complex; D051379:Mice; D011110:Polymorphism, Genetic; D014162:Transfection
D000954:Antigens, Surface; D000949:Histocompatibility Antigens Class II; D046911:Macromolecular Substances