title: A novel 90-kDa polypeptide (Tp90) possibly involved in an antigen-independent pathway of T cell activation.
abstract: A novel surface molecule, Tp90, is described which appears to be involved in an antigen-independent pathway of human T lymphocyte activation. The Tp90 molecule was identified by a monoclonal antibody (mAb), MX20, obtained from a fusion using spleen cells of a mouse immunized with cells from two T cell leukemia lines, Jurkat and HPB-ALL. Biochemical data show that Tp90 is distinct and physically independent from the structures already known to be involved in T cell activation, namely T11, T44 or T3/TCR. These results were confirmed by antibody-induced antigen modulation experiments. Modulation of Tp90 had no effect on the expression of T3 and of the T cell receptor. Conversely, the expression of Tp90 was not affected by modulation of the T3/TCR molecular complex by either anti-T3 or anti-TCR antibody. Functional studies showed that anti-Tp90 mAb MX20 induced high levels of interleukin 2 production in Jurkat cells. Modulation of the T3/TCR complex significantly decreased the response of Jurkat cells to stimulation by antibody MX20, suggesting that the T3/TCR complex regulates the ability of the Tp90 molecule to induce IL 2 synthesis. In addition to its effect on Jurkat cells, anti-Tp90 mAb was found to be mitogenic for peripheral blood T cells. As the magnitude of the proliferative response elicited by anti-Tp90 mAb was lower than that induced by anti-T3 mAb, the possibility was considered that only a subpopulation of T cells is reactive with anti-Tp90. Indeed as determined by FACS analyses, only 3-14% of E-rosette-positive cells were stained with mAb MX20. In addition, multicolor flow cytometry analysis showed that the Tp90+ cells belong preferentially to the CD8 subset.
mesh_terms: D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000276:immunology; D000918:Antibody Specificity; D000954:Antigens, Surface / Q000032:analysis* / Q000276:immunology / Q000302:isolation & purification; D001666:Binding Sites, Antibody; D002460:Cell Line; D002469:Cell Separation; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D006801:Humans; D007376:Interleukin-2 / Q000096:biosynthesis; D008213:Lymphocyte Activation; D010455:Peptides / Q000302:isolation & purification; D011233:Precipitin Tests; D011863:Radioimmunoassay; D013601:T-Lymphocytes / Q000145:classification / Q000276:immunology*; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7
chemical_list: D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D007376:Interleukin-2; D010455:Peptides; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7