Inhibition of mitogen-induced lymphokine production by cyclosporin A

Cyclosporin A prevents induction of the interleukin 2 receptor gene in cultured murine thymocytes

Blast formation and mitotic activation of G0-arrested mouse thymocytes were triggered by the addition of concanavalin A plus interleukin 2 (IL-2) to the culture medium. When added alone, Con A induces within 6 hr a complex reprogramming ("priming") that comprises the activation of the IL-2 receptor gene. The primed thymocytes are competent to interact with IL-2 and to respond to its growth-promoting effect, which corresponds to blast formation and mitotic activation. Cyclosporin A, an immunosuppressive cyclic peptide of fungal origin, prevents in T lymphocytes the activation of a set(s) of genes encoding lymphokines and the IL-2 receptor but does not affect their expression once they have been activated. The biomedical implications of these observations are discussed.

Cyclosporin A: pharmacologic activity on the immune system and effects in clinical organ transplantation

The recently discovered fungal metabolite cyclosporin A (CsA) is a potent immunosuppressant that is effective in preventing transplantation rejection due to allografts and even xenografts. Due to its influence on the biological activity of T-helper lymphocytes CsA's mechanism of action includes inhibition of cell-mediated cytolysis and delayed-type hypersensitivity (DTH) reaction. In addition to studies of the molecular mechanism of action, data on the pharmacokinetics of CsA are given. CsA does not cause anti-mitotic and/or cytotoxic effects. The side effects of the agent are relatively mild and appear to be reversible. CsA has been successfully used clinically in renal, bone-marrow, heart, heart-lung, liver, and pancreas transplantation. The application of the compound in organ transplantation appears to be superior to conventional immunosuppressive therapy.

Effects of cyclosporin A (CyA) and methylprednisolone (MP) on the immune response. I. T-cell-activating factor abrogates CyA- but not MP-induced suppression of antigen-induced lymphokine production

The influence of cyclosporin A (CyA) and methylprednisolone (MP) on the elaboration of the human lymphokine, leukocyte migration inhibitory factor (LIF) was investigated. Both CyA and MP at pharmacological concentrations inhibited the release of LIF from immune lymphocytes challenged by recall antigen. By contrast, the release of LIF in response to polyclonal activation by phytohaemagglutinin A was not affected by CyA or by MP. CyA and MP had no effect on the production of the monokine, T-lymphocyte-activating factor (TAF) by stimulated blood monocytes. However, addition of partially purified TAF to antigen-stimulated lymphocytes completely abrogated the inhibitory effect of CyA, but not that of MP. Thus, CyA and MP affect antigen-induced production of LIF by immune lymphocytes by different mechanisms.

Cyclosporin a inhibits T cell-mediated augmentation of mouse natural killer activity

Cyclosporin A (CSA) in vitro inhibited the spontaneous cytotoxic activity of mouse spleen cells against YAC target cells in a 4 hr 51Cr release assay. While natural killer (NK) cells were inhibited directly by CSA, these suppressive effects were largely reversible by coculture of effector cells for an optimal period with polyinosinic-polycytidylic acid (Poly I:C) or lipopolysaccharide (LPS). In contrast concanavalin A (Con A), in the presence of CSA, was unable to augment NK activity. The supernatant, however, of mouse spleen cells cultured with Con A was fully able to augment the NK the activity by freshly cultured spleen cells in the presence of CSA. The results indicate that CSA inhibits NK activity by two distinct mechanisms: a) a direct inactivation of NK cells and b) a suppression of production or release of an NK-activating factor from T cells, but not B cells or macrophages.