title: Characterization of the two heavy chains of the T3 complex on the surface of human T lymphocytes.
abstract: The T3 complex has been defined by a group of monoclonal antibodies which react with all human peripheral blood T lymphocytes and a subpopulation of thymocytes. This membrane structure includes glycoproteins of 44 (alpha), 37 (beta), 25 (gamma), and 20 kDa (delta) as well as a nonglycosylated polypeptide of 20 kDa (epsilon). The characterization of the alpha and beta chains has been of particular interest because they may constitute the T cell receptor for antigen. Here we show that the T3 complex prepared by immunoprecipitation from T lymphocytes of a leukemic patient (Sezary syndrome) displays an unusually strong association of the alpha and beta chains with the 20/25-kDa T3 proteins. The alpha and beta chains (48 and 44 kDa) were co-precipitated by anti-20-kDa T3 monoclonal antibodies as a disulfide-linked 90-kDa heterodimer. A minor 220-kDa multimer composed of proteins similar to the alpha and beta chains was also present in these immunoprecipitates. This multimer could be independently precipitated with a new monoclonal antibody WT-31, which detects the larger polypeptide chains of the T3 complex on all human T lymphocytes. After removal of N-linked oligosaccharides, both the alpha and beta chain were found to have 33-kDa peptide backbones with distinct isoelectric points. Using a monoclonal reagent T40/25, a 90-kDa heterodimer, consisting of 40- and 49-kDa chains with peptide backbones of 34 kDa was found to be T3-associated on the T leukemic cell line HPB-ALL. When the alpha and beta chains from the Sezary patient were compared with the corresponding chains from HPB-ALL by peptide mapping, large differences were observed. Taken together, the data presented here provide strong evidence that the T cell receptor for antigen is part of the T3 complex on the surface of human T lymphocytes.
mesh_terms: D000118:Acetylglucosaminidase / Q000378:metabolism; D000911:Antibodies, Monoclonal; D000941:Antigens / Q000097:blood*; D017252:CD3 Complex; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007945:Leukemia, Lymphoid / Q000097:blood; D046911:Macromolecular Substances; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D008698:Mesylates / Q000494:pharmacology; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis; D012751:Sezary Syndrome / Q000097:blood; D013601:T-Lymphocytes / Q000032:analysis*; D014357:Trypsin / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000941:Antigens; D017252:CD3 Complex; D046911:Macromolecular Substances; D008698:Mesylates; D010446:Peptide Fragments; D000118:Acetylglucosaminidase; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D014357:Trypsin; C012077:trifluoromethanesulfonic acid