Differential regulation of colony-stimulating factors and interleukin 2 production by cyclosporin A.

Stimulation of T lymphocytes with mitogens or antigens is followed by proliferation and lymphokine production. Although cyclosporin A (CsA), an immunosuppressive drug, has been shown to inhibit the production of certain lymphokines, including interleukin 2 (IL-2), interleukin 3 (IL-3), and gamma-interferon, its effect on the production of granulocyte/macrophage colony-stimulating factor (GM-CSF) has not been evaluated. In the current study, concanavalin A (Con A)-stimulated murine spleen cells secreted GM-CSF, IL-3, and IL-2, and in the presence of CsA (0.1-1.0 micrograms/ml), IL-2 and IL-3 activities were inhibited. In contrast, significant activity was detected when the CsA-treated culture supernatants were assayed on a cell line that is dependent on GM-CSF and/or IL-3. Similar CsA-resistant activity was observed when the EL-4 thymoma cells were stimulated with a phorbol ester [phorbol 12-myristate 13-acetate (PMA)] in the presence of CsA. The activity resistant to CsA was identified as GM-CSF by the ability of specific antibodies against murine recombinant GM-CSF to neutralize its activity. These findings indicate that GM-CSF, in contrast to IL-2 and IL-3, was not inhibited by CsA. In additional experiments, transfer blot of poly(A)+ RNA isolated from PMA-induced EL-4 cells in the presence or the absence of CsA was hybridized with GM-CSF and IL-2 cDNA probes. Expression of the GM-CSF gene in EL-4 cells was detected independent of CsA, whereas CsA inhibited the expression of the IL-2 gene. The present data show that production of IL-2 and IL-3, but not that of GM-CSF, is inhibited by CsA and suggest a differential control mechanism for lymphokine synthesis in T lymphocytes.