title: Analysis of isolated and combined effects of calcium ionophore and phorbol ester on T lymphocyte activation.
abstract: Isolated and combined effects of the calcium ionophore A23187 and of the protein kinase C activator phorbol myristate acetate (PMA) on T cell activation parameters were analysed on unprimed Balb/c lymph node T lymphocytes (LNL). High doses of PMA were mitogenic for resting T cells, but non-mitogenic doses of PMA induced T cell proliferation in combination with A23187, which was non-mitogenic by itself. Mitogenesis induced by a combination of A23187 and PMA (A23187/PMA) showed the following characteristics: it was not abolished after extensive depletion of accessory cells; purified L3T4+, but not Lyt2+ T cells responded in the absence of accessory cells; mitogenesis was completely blocked by a mixture of two monoclonal antibodies directed to the murine interleukin 2 (IL-2) receptor (7D4/3C7mAbs); cyclosporin A, dibutyril cyclic AMP, and T cell K+ channel blockers quinine and verapamil all blocked mitogenesis. A marked synergism between A23187 and PMA was noted in induction of T cell enlargement, IL-2 release, and induction of IL-2 responsiveness. No synergism was noted in IL-2 receptor expression, A23187 and PMA being able to induce IL-2 receptors alone. Calcium ionophore induced IL-2 receptor expression, but failed to induce IL-2 release and IL-2 responsiveness. Addition of A23187/PMA to the IL-2-dependent CTL-L clone did not result in cell proliferation. Addition of A23187/PMA to Con A-activated T cell blasts leads to a vigorous proliferative response. This response is blocked by 7D4/3C7 mAbs, indicating a role for endogenously produced IL-2 in this case. The results indicate that T cell mitogenesis by A23187/PMA is IL-2-dependent, and suggest a critical role for protein kinase C in IL-2 release and induction of IL-2 responsiveness. In addition, the data suggest distinct, but co-operative pathways of IL-2 receptor induction, controlled by elevated Ca2+ alone and by protein kinase C. Subsequent intracellular events of T cell activation by A23187/PMA may be quite similar to those triggered by Con A, since both kinds of stimulation are blocked by agents such as cyclosporin A, dbcAMP and K+ channel blockers.
mesh_terms: D000818:Animals; D000001:Calcimycin / Q000494:pharmacology*; D004357:Drug Synergism; D005260:Female; D007376:Interleukin-2 / Q000096:biosynthesis; D008213:Lymphocyte Activation / Q000187:drug effects*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D011971:Receptors, Immunologic / Q000032:analysis; D015375:Receptors, Interleukin-2; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D007376:Interleukin-2; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2; D000001:Calcimycin; D013755:Tetradecanoylphorbol Acetate