Mouse monoclonal anti-Ia antibodies recognize cross-reacting determinants expressed on distinct subsets of human Ia-like cell-surface molecules.
Human Ia-like cell-surface molecules from a homozygous HLA-DR (6/6) B lymphoblastoid cell line have been analyzed using five mouse anti-Ia m.Ab cross-reacting with HLA-DR antigens. The surface-iodinated molecules immunoprecipitated by these m.Ab were analyzed by SDS-PAGE under reducing conditions and by SDS-PAGE followed by isoelectrofocusing. As read from the different migration patterns, three distinct combinations of human Ia-like molecules were identified by these m.Ab. Three anti-I-E-reactive m.Ab immunoprecipitated two-chain molecules whose apparent mol. wt (32K, 29K) corresponded to those of the classical HLA-DR antigens. One m.Ab which on mouse cells recognized a determinant shared by the I-A and I-E molecules precipitated not only the 32-29K bands, but also a 26K band from human cell extracts. Finally, an I-A reactive m.Ab precipitated a complex set of polypeptides including in addition to the 32-29K bands, three additional chains of 30, 28 and 26K. Sequential immunoprecipitation demonstrated that removal of the classical 29-32K HLA-DR chains by an anti-I-E m.Ab did not affect the subsequent immunoprecipitation of the additional chains by the anti-I-A or the anti-I-A + I-E m.Abs. These patterns and those obtained by 2D-gels analysis which demonstrated the complexity of the 26K band are compatible with the coexpression of at least three different subsets of molecules: (1) Ia-like molecules of 29-32K, recognized by all the m.Ab used; (b) molecules of 28-30K recognized by the anti-I-A m.Ab and (c) molecules apparently constituted by 26K chains, precipitated by the anti-I-A m.Ab and by the anti-I-A + I-E m.Ab.
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000954:Antigens, Surface / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D002460:Cell Line; D011232:Chemical Precipitation; D003429:Cross Reactions; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes / Q000276:immunology*; D006023:Glycoproteins / Q000276:immunology; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D006801:Humans; D007518:Isoantibodies / Q000276:immunology; D051379:Mice
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D000939:Epitopes; D006023:Glycoproteins; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II; D007518:Isoantibodies