Characterization of a B lymphoblastoid cell line mutant that secretes HLA-A2.
HLA-A2 antigen mutants were obtained previously from the B lymphoblastoid cell line T5-1 by mutagenesis followed by immunoselection. Here we present biochemical studies of one particular mutant, clone 8.14.1. These cells synthesize two forms of HLA-A2: a minor form, which remains cell-associated at all times, and an abundant form, which is secreted. The former appears by SDS-PAGE to be slightly larger than T5-1 HLA-A2, whereas the latter appears to be 4000 to 5000 daltons smaller. In vitro translation and in vivo pulse-chase studies suggest that these species are not related to each other by post-translational processing. Proteolytic digestion studies localize the resulting structural alteration in the mobility difference between wild-type and secreted HLA-A2 to a region near the carboxy terminus of the HLA-A2 heavy chain; however, their extreme carboxy termini appear similar, if not identical. We suggest that the secreted form may result from a pattern of RNA splicing in which the exon encoding the hydrophobic, membrane-spanning region is frequently deleted.
D000911:Antibodies, Monoclonal / Q000276:immunology; D000937:Antigen-Antibody Reactions; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D002460:Cell Line; D011232:Chemical Precipitation; D002850:Chromatography, Gel; D002999:Clone Cells / Q000276:immunology / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006680:HLA Antigens / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification; D015789:HLA-A2 Antigen; D006801:Humans; D009154:Mutation; D014176:Protein Biosynthesis
D000911:Antibodies, Monoclonal; D006680:HLA Antigens; D015789:HLA-A2 Antigen