title: Biochemical characterization of a p43,12 complex: comparison with human and murine class I molecules.
abstract: A monoclonal antibody designated as C21 reacting with a p43,12 complex was developed against human thymocytes. It stained predominantly the early hematopoietic cells of the lymphoid lineage and also thymocytes, peripheral B-cells and activated T- and B-cells similarly to OKT10. The heavy chain of this antigen was a glycoprotein of Mr 43,000 (p43). Sequential immunoprecipitation with C21 and OKT10 antibodies indicated that they both reacted with an identical heavy-chain molecule. This observation was further documented by two-dimensional analysis. Monoclonal antibody C21 was used to probe a p43,12 complex further. Structural polymorphism of the p43 heavy chain isolated from T- and B-cells of different individuals was not detected by chymotryptic peptide mapping, although molecules from these cell types possessed a different charge on two-dimensional gels. An unusual observation was made regarding this complex on MOLT4 cells. The light chain co-precipitated from these cells was 12,000 daltons and had a pI distinct from that of beta 2-microglobulin but similar to the pI of the beta t molecule. Comparison between chymotryptic peptide maps of the p43 heavy chain and those of the human and murine class I molecules such as HLA, T6, H-2K, Qa-2 and TL revealed no apparent homology. We have shown, however, that the peptide backbone of p43, as studied by both tunicamycin treatment of cells and endoglycosidase F digestion of immunoprecipitates, was identical in size to that of murine Qa-1. These results suggest that the p43 antigen may be homologous to murine Qa-1 or another class I antigen encoded in the murine TL:Qa region.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000941:Antigens / Q000032:analysis*; D002241:Carbohydrates / Q000032:analysis; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D006413:Hematopoietic System / Q000276:immunology; D006801:Humans; D007123:Immunoelectrophoresis, Two-Dimensional; D007942:Leukemia, Experimental / Q000276:immunology; D008223:Lymphoma / Q000276:immunology; D008285:Major Histocompatibility Complex; D051379:Mice; D008815:Mice, Inbred Strains; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D000941:Antigens; D002241:Carbohydrates