title: Mechanism of action of cyclosporin A in vivo. I. Cyclosporin A fails to inhibit T lymphocyte activation in response to alloantigens.
abstract: Although cyclosporin A (Cy A) has been widely used clinically as a potent suppressor of organ allograft rejection and has been shown to block T lymphocyte activation in vitro by inhibiting the generation of interleukin 2 (IL-2) and other lymphokines, little direct evidence is available to support the view that the immunosuppressive effects of Cy A in vivo are mediated by a similar inhibition of the autocrine lymphokine cascade. We have used a quantitative assay for the assessment of the role of the IL-2/IL-2 receptor system in the activation of the draining popliteal lymph node population after the injection of allogeneic cells in the footpad to define the effects of Cy A on the early events of lymphocyte activation in vivo and to compare them with the effects of Cy A on lymphocyte activation in vitro. The administration of Cy A in vivo had no effect on alloantigen-induced increases in cell size, percentage of cells expressing the IL-2 receptor, the spontaneous or IL-2-driven proliferation of freshly explanted cells, or the induction of cytotoxic T lymphocyte activity. These findings raise major questions about the mechanism of action of Cy A in vivo and suggest that more experimentation is required to probe the mechanisms of Cy A-induced suppression of the response to allografts.
mesh_terms: D000818:Animals; D003524:Cyclosporins / Q000494:pharmacology*; D005260:Female; D007376:Interleukin-2 / Q000502:physiology; D007519:Isoantigens / Q000276:immunology*; D008198:Lymph Nodes / Q000166:cytology; D008213:Lymphocyte Activation / Q000187:drug effects*; D008214:Lymphocytes / Q000145:classification; D051379:Mice; D008807:Mice, Inbred BALB C / Q000276:immunology; D008810:Mice, Inbred C57BL / Q000276:immunology; D011971:Receptors, Immunologic / Q000096:biosynthesis; D015375:Receptors, Interleukin-2; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*
chemical_list: D003524:Cyclosporins; D007376:Interleukin-2; D007519:Isoantigens; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2