title: Cellular distrubtion, purification, and molecular nature of human Ia antigens.
abstract: Human Ia antigens were extensively purified (1390-fold increase in specific activity) in 32% yield from BRI 8 cells, a lymphoblastoid B-cell line. Purification was monitored by using allogeneic antisera arising by foetal-maternal stimulation. The product, a glycoprotein fraction, contained the Ia antigens, the HLA-A and -B antigens, and a glycoprotein of unknown function. The glycoprotein fraction was composed of four glycosylated polypeptides with molecular weights of 43,000, 39,000, 33,000, and 28,000, and beta2-microglobulin; no polypeptide was linked to another by disulphide bridges. The A and B antigens only were absorbed by antibody against beta2-microglobulin. The Ia antigens comprised one each of the 33,000 and 28,000 molecular weight glycosylated polypeptides noncovalently linked together. Thus, only these chains were absorbed by xenogeneic anti-Ia antisera and were cross-linked by dimethyl-3-3'-dithiobispropionimidate dihydrochloride. The dimeric molecule bound deoxycholate (0.26 g/g of protein) and, when solubilized in deoxycholate, has a molecular weight of 77,000. The Ia allo- and xeno-antigenic activities were labile to heating and proteolysis and are probably determined by the polypeptide structure. Xenogeneic specific anti-Ia antisera were raised in rabbits and mice by immunizing with the glycoprotein fraction. These antisera reacted with B lymphocytes and monocytes but not T lymphocytes and fibroblasts. Their Fab fragments blocked the cytotoxicity of the allogeneic antisera for B lymphocytes and were potent inhibitors of the mixed lymphocyte reaction.
mesh_terms: D000941:Antigens / Q000032:analysis / Q000302:isolation & purification; D002460:Cell Line; D003601:Cytotoxicity Tests, Immunologic; D000939:Epitopes; D006023:Glycoproteins / Q000032:analysis; D006801:Humans; D007106:Immune Sera; D007519:Isoantigens; D008968:Molecular Conformation; D008970:Molecular Weight; D010455:Peptides / Q000032:analysis; D001613:beta 2-Microglobulin / Q000032:analysis
chemical_list: D000941:Antigens; D000939:Epitopes; D006023:Glycoproteins; D007106:Immune Sera; D007519:Isoantigens; D010455:Peptides; D001613:beta 2-Microglobulin