title: Novel allele-specific, post-translational reduction in HLA class I surface expression in a mutant human B cell line.
abstract: Human B cell line .220 has a novel defect in HLA class I cell surface expression. Mutant .220 was derived from .184TGr, from which both copies of HLA-A and -B are deleted, and has less surface HLA-C than .184TGr. Transfer of class I genes into .220 revealed allele-specific reductions in surface expression: HLA-A1 and -B8 were 1 to 21% of normal; HLA-A11, -A24, and -B5 were moderately reduced; and HLA-A2, -A3, and -B7 were reduced little, if at all. Class I mRNA in .220(A1) and .220(B8) transferents is normal in size and at least normal in quantity. Surface expression of class I molecules was restored by fusing .220 transferents with mutant .174, which lacks the TAP-1 and -2 genes needed for transport of class I-binding peptides. Fusion of .220(A1) cells with beta 2-microglobulin-deficient Daudi cells also fully restored surface expression of class I molecules encoded by both parental cells, indicating beta 2-microglobulin is functional in .220. Pulse-chase experiments showed transgene-encoded HLA-A1 and -B8 alpha-chains are made in apparently normal amounts and associate with beta 2-microglobulin in .220. However, post-translational processing of the HLA-A1 and -B8 molecules is retarded in or before the Golgi apparatus, and immunoprecipitable HLA-A1 molecules disappear after their synthesis. The effects of these abnormalities on surface expression of class I molecules were reversed by incubating .220(A1) and .220(B8) cells at 21 degrees C, which greatly increased the amounts of cell surface HLA-A1 and -B8.
authors.affiliation: Laboratory of Genetics, University of Wisconsin, Madison 53706.
authors.forename: R
authors.initials: R
authors.lastname: Greenwood
authors.forename: Y
authors.initials: Y
authors.lastname: Shimizu
authors.forename: G S
authors.initials: GS
authors.lastname: Sekhon
authors.forename: R
authors.initials: R
authors.lastname: DeMars
mesh_terms: D000483:Alleles; D001402:B-Lymphocytes / Q000276:immunology*; D015152:Blotting, Northern; D002459:Cell Fusion; D002460:Cell Line; D006680:HLA Antigens / Q000096:biosynthesis* / Q000235:genetics; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D009154:Mutation / Q000235:genetics; D014176:Protein Biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D014162:Transfection
chemical_list: D006680:HLA Antigens; D015395:Histocompatibility Antigens Class I; D012333:RNA, Messenger