title: Expression of T-cell-activating protein in peripheral lymphocyte subsets.
abstract: T-cell-activating protein (TAP) is an allelic 12-kDa membrane protein that participates in T-cell activation. Soluble anti-TAP monoclonal antibodies can trigger antigen-specific, major histocompatibility complex-restricted T-cell hybridomas to produce interleukin 2 and are mitogenic for normal T cells and thymocytes. TAP is expressed on 10% of thymocytes, which are mainly cortisone-resistant and mature. In the periphery, TAP is expressed on 70% of resting T cells but not on resting B cells. In this report, we analyze in detail the nature of TAP expression on peripheral lymphocyte subsets by immunofluorescence techniques. We show that all inducer (L3T4+) T cells are TAP+. In contrast, only 50% of Lyt-2+ T cells express detectable TAP. Functional studies demonstrated that at least part of the heterogeneity of TAP expression is present in the Lyt-2+ cytolytic T-cell (CTL) subset. Unstimulated CTL precursors are TAP- but are induced to express TAP in the effector state. Furthermore, this reflects actual synthesis of TAP, as TAP is detectable on activated Lyt-2+ CTLs passaged in vitro under conditions where passive acquisition can be ruled out. To extend this observation, we have studied the expression of TAP on activated T and B cells. Upon activation, all T and B cells became TAP+. Furthermore, the TAP molecules on B and T cells are indistinguishable by NaDodSO4/polyacrylamide gel electrophoresis. This suggests that TAP expression defines further heterogeneity of lymphocytes, with activation being one parameter influencing its expression.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D002454:Cell Differentiation; D003602:Cytotoxicity, Immunologic; D005434:Flow Cytometry; D008213:Lymphocyte Activation; D051379:Mice; D013601:T-Lymphocytes / Q000145:classification / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7
chemical_list: D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7