title: Lyt-2 and lyt-3 antigens are on two different polypeptide subunits linked by disulfide bonds. Relationship of subunits to T cell cytolytic activity.
abstract: Lyt-2 and Lyt-3 antigens are carried on separate disulfide-bonded subunits of the same cell surface macromolecules. These are present on thymocytes in a variety of multimeric forms consisting of disulfide-bonded dimers, tetramers, and hexamers of pairwise combinations of three subunits (30,000, 34,000, and 38,000 Mr). From reduced and alkylated Nonidet-P40 thymus extracts, a monoclonal anti-Lyt-3 precipitates only the 30,000 Mr subunit, but not the 30,000 Mr subunit. Almost all of the Lyt-2 and Lyt-3 subunits on the cell are covalently linked by disulfide bonds. However, small amounts of free Lyt-3 subunit was seen in some experiments. Similarly, small amounts of Lyt-2-3- material, consisting of dimers of the 38,000 and 34,000 Mr subunits were identified. Each of the three subunits migrated with a basic charge (pI greater than 8) on two-dimensional gels. Cytotoxic effector cells that are blocked by anti-Lyt-2 and anti-3 can be treated with trypsin and other arginine-specific proteases to remove these antigens. At low concentrations of these proteases, Lyt-3 antigens are selectively removed. After selective removal of Lyt-3 antigens, cytotoxic effector cells are still active and blocking of activity by anti-Lyt-3 is significantly reduced, whereas blocking of activity by anti-Lyt-2 is significantly increased. Neither Lyt-2 nor Lyt-3 is allelically excluded on thymocytes or T cells. These results suggested that the Lyt-2, Lyt-3 macromolecules are associated with but do not serve as the T cell antigen receptor.
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D000954:Antigens, Surface / Q000235:genetics; D003602:Cytotoxicity, Immunologic; D004220:Disulfides; D000939:Epitopes; D006579:Heterozygote; D007111:Immunity, Cellular; D007518:Isoantibodies; D007526:Isoelectric Point; D046911:Macromolecular Substances; D051379:Mice; D008970:Molecular Weight; D011487:Protein Conformation; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000954:Antigens, Surface; D004220:Disulfides; D000939:Epitopes; D007518:Isoantibodies; C029805:Lyt antibodies; D046911:Macromolecular Substances