Effect of cyclosporin A on the production of interferon by human peripheral blood leukocytes in vitro

Differential effect of cyclosporin-A on the mixed-lymphocyte culture-induced proliferative and cytotoxic responses of T lymphocytes with different cell densities

We have analyzed the effect of cyclosporin-A (CsA) on the proliferative and cytotoxic responses induced by mixed-lymphocyte cultures (MLC-s) on low and high density T lymphocytes. Allogeneic stimulation had a different impact on the two subsets. Proliferative and cytotoxic responses were inversely correlated; i.e., high density cells proliferated but exerted low levels of cytotoxicity while the lytic activity of the low density subset was stronger and the proliferation was weak. CsA impaired the proliferative and cytotoxic responses of the high density T lymphocytes but influenced less markedly the response of the low density cells. In both subsets CsA inhibited the MLC-induced interleukin 2 (IL-2) production. The generation of specific cytotoxicity was markedly suppressed by CsA, whereas the generation of anomalous activity was less affected. Addition of exogenous IL-2 to the CsA-containing cultures fully restored the proliferation and the generation of nonspecific cytotoxicity. In contrast, addition of interferon gamma (IFN-gamma) restored neither of these responses. However, for complete restoration of the stimulation-specific cytotoxicity, addition of both lymphokines was required. Taken together these results suggest that the CsA-induced suppression of the lymphokine production has different consequences in the low and high density subsets; the expression of anomalous and specific cytotoxicities require different signals; CsA interferes with several steps in the T-cell activation.

Effect of cyclosporin A on immunity to Listeria monocytogenes

The effect of the immunosuppressive drug cyclosporin A (CS-A) on immunity to the facultative intracellular bacterium Listeria monocytogenes was investigated in unprimed and primed mice. Different treatment protocols were followed to evaluate the time dependence of CS-A-mediated immune suppression and the effect of CS-A on immunological memory to L. monocytogenes. The effect of CS-A was observed only during and after activation of T cell-mediated immunity, whereas early resistance exerted by macrophages assessed 6 and 70 min after challenge remained unaffected. CS-A suppressed efficient elimination of L. monocytogenes even when given after day 3 of a primary infection. This contrasts with findings in other models, including viral infections, where CS-A must be administered very early in an immune response to suppress it. CS-A suppressed antibacterial resistance in mice primed at various times before challenge; suppression of protection was time dependent and was virtually complete in livers, whereas CS-A-resistant memory persisted in spleens for up to 10 months.

Effects of cyclosporin A on humoral immune response and resistance against vesicular stomatitis virus in mice

The effect of cyclosporin A (CS-A) on the antiviral humoral response was studied by using vesicular stomatitis virus (VSV); VSV provided the opportunity to simultaneously assess both T-independent and T-dependent antibody responses. The T-independent anti-VSV immunoglobulin M (IgM) response was virtually unaffected, whereas the T-dependent primary anti-VSV IgG response was suppressed by CS-A; in contrast, the secondary IgG response was highly resistant to CS-A. Moreover, once the switch from IgM to IgG had occurred, the primary response also became refractory to suppression by CS-A. We concluded that the effect of CS-A on the primary anti-VSV antibody response was mediated via impairment of a T-dependent mechanism; in contrast, memory T cells or memory B cells or both were quite resistant to the suppressive effects of CS-A. CS-A treatment rendered mice highly susceptible to VSV infection; under CS-A treatment, mortality was 100% after infection via footpads, whereas immunocompetent mice survived. Since CS-A does not impair induction of early T-independent anti-VSV IgM neutralizing antibodies, this high mortality in CS-A treated mice illustrates the crucial role of CS-A-sensitive cells in resistance against VSV.

Cyclosporin A inhibits induction but not production of gamma interferon induced by Epstein-Barr virus

Cyclosporin A (CsA) interferes with various T-cell functions in vitro and is a potent inhibitor of T-cell-dependent reactions in vivo, such as graft rejection and control of virus infections. Since human gamma interferon (Hu IFN-gamma) is synthesized by T cells and has a controlling role in regulation of Epstein-Barr virus (EBV) infection, we have studied the effects of CsA on EBV-induced cellular Hu IFN-gamma release. CsA inhibited dose-dependently the EBV-induced Hu IFN-gamma response, studied at the cellular level in human blood lymphocytes. These effects were not due to toxicity of CsA, since at inhibitory levels cellular EBV infection measured as polyclonal IgM production proceeded unaffected. CsA did not affect the number of spontaneous Hu IFN-gamma-secreting cells, nor did it have any inhibitory effect if added after virus exposure. It is concluded that CsA inhibits induction but not production of cellular Hu IFN-gamma.

Effect of cyclosporin-A (CsA) on the ability of T lymphocyte subsets to inhibit the proliferation of autologous EBV-transformed B cells

We have analyzed the effect of Cyclosporin-A (CsA) on the in vitro suppression of Epstein-Barr virus (EBV)-induced B-cell proliferations separated on the basis of cell density. CsA abolished the growth-inhibitory capacity of high-density T cells but influenced only marginally the activity of low-density lymphocytes; this suggested that different mechanisms mediate suppression in the two subsets. Stimulation with irradiated EBV-transformed cells had a different impact on the activity of low- and high-density lymphocytes. Proliferative and cytotoxic responses were inversely correlated, i.e. high-density cells proliferated but exerted low cytotoxicity, while the lytic activity of the low-density subset was stronger in the absence of significant cell proliferation. Proliferation and generation of cytotoxicity were abrogated by CsA in both subsets. The activities could be restored by addition of exogenous IL-2, suggesting that the drug may interfere with the cascade of lymphokine--cell interactions which leads to activation of immune responses. From the analysis of athe CsA effects on the two subsets it seems that the high-density one contains specific memory T cells which are activated and proliferate upon encounter with EBV-infected cells. On the other hand, low-density lymphocytes are induced to release soluble factors with antiproliferative activity. The secretory function was resistant to the suppressive effect of CsA.

Effects of treatment with azathioprine and cyclosporin A on interferon-gamma production by peripheral blood leukocytes of renal allograft recipients

We have studied the concanavalin A (ConA)-induced interferon gamma (IFN-gamma) production of peripheral blood mononuclear cells (PBMC) of renal allograft recipients. Both under immunosuppressive treatment with azathioprine and with cyclosporin A (CsA) the PBMC of these patients proved deficient for IFN-gamma production when compared to those of healthy controls. After conversion from conventional azathioprine to CsA medication the ConA-induced IFN-gamma production increased.

Gamma interferon synthesis by human thymocytes and T lymphocytes inhibited by cyclosporin A

Cyclosporin A depresses the synthesis of gamma interferon by human thymocytes and T lymphocytes in vitro. This observation is of potential clinical significance because the long-term treatment of transplant patients with cyclosporin A, a widely used immunosuppressive agent, can give rise to B-cell lymphoma resulting from Epstein-Barr virus activation.