Suppressive influences of IFN-α on IL-17 expression in human CD4+ T cells

We examined the direct effects of IFN-α on the development of Th17 with a system using immobilized anti-CD3, which permits activation of CD4+ T cells in the complete absence of accessory cells. Highly purified CD4+ T cells obtained from healthy donors were stimulated with immobilized anti-CD3 with or without IFN-α. IFN-α suppressed the production of IL-17 of immobilized anti-CD3-stimulated CD4+ T cells in a dose–response manner. Accordingly, IFN-α inhibited IL-17 mRNA expression in immobilized anti-CD3-stimulated CD4+ T cells. IFN-α did not affect the production of TGF-β or IL-6, but inhibited RORC mRNA expression of anti-CD3-stimulated CD4+ T cells. These results indicate that IFN-α suppresses IL-17 expression and Th17 differentiation through down-regulation of RORC mRNA expression. It is therefore suggested that these effects might play a role in the mode of action of IFN-α in the treatment of various inflammatory diseases.