Concanavalin A triggers T lymphocytes by directly interacting with their receptors for activation.
Anti-HLA-DR antibodies did not inhibit concanavalin A-(Con A) induced T cell proliferation or the generation of suppressor cells capable of inhibiting immunoglobulin synthesis in autologous mononuclear cells after pokeweed mitogen stimulation. Nylon-wool purified T cells (pretreated with anti-HLA-DR antibody and C) exposed to Con A acquired responsiveness to interleukin 2 (IL 2) and were able to absorb this growth factor, whereas nonlectin-treated cells did not respond to IL 2 and could not absorb it. In the presence of interleukin 1 (IL 1), Con A stimulated the synthesis of IL 2 in purified OKT4+ lymphocytes but not OKT8+ cells. However, in the absence of IL 1, neither resting OKT4+ nor Con A-treated OKT4+ cells produced IL 2. Con A by itself did not directly stimulate macrophages to synthesize IL 1, although it could do so in the presence of OKT4+ but not OKT8+ lymphocytes. In addition, Con A induced proliferation of purified T cells provided IL 1 was supplied to the cultures. Cyclosporin A rendered Con A-treated T cells unresponsive to IL 2, made lectin-stimulated OKT4+ lymphocytes unable to respond to IL 1, and inhibited the synthesis of IL 2. Furthermore, this drug abrogated the Con A-stimulated synthesis of IL 1 by acting on OKT4+ lymphocytes and not on macrophages. Finally, cyclosporin-A suppressed the proliferative response and the generation of suppressor T cells induced by Con A. The following are concluded: 1) HLA-DR antigens do not seem to play any role in the triggering of T cells by Con A, and macrophages participate in lectin-induced activation of T cells mainly by providing IL 1. 2) Cyclosporin-A inhibits activation of T cells by interfering with the mechanism by which Con A stimulates T lymphocytes. 3) Con A triggers T lymphocytes by directly interacting with their receptors for activation.
D000818:Animals; D000906:Antibodies; D000911:Antibodies, Monoclonal; D003208:Concanavalin A / Q000494:pharmacology*; D003524:Cyclosporins / Q000494:pharmacology; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D006801:Humans; D007375:Interleukin-1; D007376:Interleukin-2 / Q000096:biosynthesis; D008213:Lymphocyte Activation; D014176:Protein Biosynthesis; D011506:Proteins / Q000494:pharmacology; D011817:Rabbits; D011948:Receptors, Antigen, T-Cell / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology
D000906:Antibodies; D000911:Antibodies, Monoclonal; D003524:Cyclosporins; D000949:Histocompatibility Antigens Class II; D007375:Interleukin-1; D007376:Interleukin-2; D011506:Proteins; D011948:Receptors, Antigen, T-Cell; D003208:Concanavalin A