title: Influence of allelic polymorphism on the assembly and surface expression of class II MHC (Ia) molecules.
abstract: Cell surface Ia expression was examined following transfection of murine alpha and beta class II major histocompatibility complex (MHC) genes into L cells. Although haplotype-matched (e.g., Ak beta Ak alpha) gene pairs yielded high expression in primary transfectants, haplotype-mismatched pairs (e.g., Ak beta Ad alpha) gave unexpectedly low expression. RNA analysis revealed a requirement for greater A beta, and particularly A alpha transcript levels in haplotype-mismatched vs. haplotype-matched transfectants with similar levels of membrane Ia. A beta allelic control of this assembly/expression process was mapped to the NH2-terminal (beta 1) domain, the locus of high intraspecies polymorphism. These data on the effects of allelic variation on Ia levels provide a possible explanation for the strong linkage disequilibrium of A alpha and A beta genes and may account for the current molecular organization of the I region of the MHC.
mesh_terms: D000483:Alleles; D000818:Animals; D001402:B-Lymphocytes; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology*; D005802:Genes, MHC Class II; D008040:Genetic Linkage; D014644:Genetic Variation; D000949:Histocompatibility Antigens Class II / Q000235:genetics*; D007739:L Cells; D008223:Lymphoma; D051379:Mice; D011110:Polymorphism, Genetic; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D000949:Histocompatibility Antigens Class II; D012333:RNA, Messenger