Beta 2-microglobulin from serum associates with MHC class I antigens on the surface of cultured cells.
Beta 2-microglobulin (beta 2-m) is a highly conserved polypeptide (12,000 molecular weight; 12K) noncovalently associated with the heavy chain (45-48K) of the major histocompatibility complex (MHC) class I antigens. Its synthesis is required for expression of the HLA-A/B and H-2K/D heavy chains at the cell surface; beta 2-m is also associated with the human cell-surface antigens T6 and M241 isolated from thymocytes. However, on the T leukaemic cell line MOLT-4 some of the T6 antigens contain a different 12K subunit, termed beta t (refs 3, 7, 8). Purified human beta 2-m can exchange partially both with human beta 2-m associated with HLA-antigens, and with mouse beta 2-m associated with murine alloantigens. As MOLT-4 cells were grown in the presence of fetal calf serum (FCS) and as serum is known to contain some free beta 2-m, we examined whether beta t was bovine beta 2-m which had replaced endogenous beta 2-m on the surface of the cell. Here we show both that beta 2-m from FCS or human serum (HuS) used in cell culture can exchange with beta 2-m on the cell surface, and that beta t is in fact bovine beta 2-m.
D000818:Animals; D000954:Antigens, Surface / Q000235:genetics*; D002417:Cattle; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D006680:HLA Antigens / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D007945:Leukemia, Lymphoid / Q000276:immunology; D008285:Major Histocompatibility Complex; D008970:Molecular Weight; D001613:beta 2-Microglobulin / Q000276:immunology*
D000954:Antigens, Surface; D006680:HLA Antigens; D001613:beta 2-Microglobulin