title: Identification of a novel 45-kDa cell surface molecule involved in activation of the human Jurkat T cell line.
abstract: This report describes a surface molecule, Tp45, which appears to be involved in interleukin 2 production and Ca2+ mobilization by Jurkat cells. The Tp45 molecule was identified by a monoclonal antibody, MX13, on the surface of either T3/TCR+ or T3/TCR- human T cell lines. Biochemical data showed that mAb MX13 precipitated a single polypeptide chain of 45 kDa both under reduced and nonreduced conditions from lysates of 125I-surface-labeled cells. Sequential immunodepletion experiments using lysates of 125I-labeled T3/TCR+ cells showed that Tp45 was distinct from the alpha chain of the TCR complex. However, incubation of such cells with either anti-T3 or anti-TCR monoclonal antibody induced complete modulation of both the T3/TCR complex and Tp45. Conversely, complete modulation of both Tp45 and the T3/TCR complex was observed after incubation with anti-Tp45 antibody. Functional studies showed that anti-Tp45 antibody induced high levels of interleukin 2 production in Jurkat cells. In addition, incubation of these cells with the antibody resulted in Ca2+ mobilization from internal stores. Anti-Tp45 antibody reacted with 3-19% peripheral blood (E-rosette-positive) T cells in individual donors. The magnitude of the proliferative response elicited by anti-Tp45 antibody for peripheral blood T cells was lower than that induced by an anti-T3 antibody. This observation is compatible with the idea that only a subpopulation of T cells is reactive with anti-Tp45. Multicolor flow cytometry analysis showed that the Tp45+ cells belong preferentially to the T8 subset.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000954:Antigens, Surface / Q000032:analysis* / Q000276:immunology; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D006801:Humans; D007376:Interleukin-2 / Q000096:biosynthesis; D008213:Lymphocyte Activation; D051379:Mice; D008811:Mice, Inbred DBA; D011948:Receptors, Antigen, T-Cell / Q000032:analysis / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D007376:Interleukin-2; D011948:Receptors, Antigen, T-Cell; D002118:Calcium