Interferon alpha inhibits antigen-specific production of proinflammatory cytokines and enhances antigen-specific transforming growth factor beta production in antigen-induced arthritis

Introduction: Interferon alpha (IFN-alpha) has a complex role in autoimmunity, in that it may both enhance and prevent inflammation. We have previously shown that the presence of IFN-alpha at sensitization protects against subsequent antigen-triggered arthritis. To understand this tolerogenic mechanism, we performed a descriptive, hypothesis-generating study of cellular and humoral responses associated with IFN-alpha-mediated protection against arthritis. Methods: Arthritis was evaluated at day 28 in mice given a subcutaneous injection of methylated bovine serum albumin (mBSA), together with Freund adjuvant and 0 to 5,000 U IFN-alpha at days 1 and 7, followed by intraarticular injection of mBSA alone at day 21. The effect of IFN-alpha on mBSA-specific IgG1, IgG2a, IgG2b, IgA, and IgE was evaluated by enzyme-linked immunosorbent assay (ELISA). Cytokines in circulation and in ex vivo cultures on mBSA restimulation was evaluated with ELISA and Luminex, and the identity of cytokine-producing cells by fluorescence-activated cell sorting (FACS) analysis. Results: Administration of IFN-alpha protected mice from arthritis in a dose-dependent manner but had no effect on antigen-specific antibody levels. However, IFN-alpha did inhibit the initial increase of IL-6, IL-10, IL-12, and TNF, and the recall response induced by intraarticular mBSA challenge of IL-1 beta, IL-10, IL-12, TNF, IFN-gamma, and IL-17 in serum. IFN-alpha decreased both macrophage and CD4(+) T cell-derived IFN-gamma production, whereas IL-17 was decreased only in CD4(+) T cells. Ex vivo, in mBSA-restimulated spleen and lymph node cell cultures, the inhibitory effect of in vivo administration of IFN-alpha on proinflammatory cytokine production was clearly apparent, but had a time limit. An earlier macrophage-derived, and stronger activation of the antiinflammatory cytokine transforming growth factor beta (TGF-beta) was observed in IFN-alpha-treated animals, combined with an increase in CD4(+) T cells producing TGF-beta when arthritis was triggered by mBSA (day 21). Presence of IFN-alpha at immunizations also prevented the reduction in TGF-beta production, which was induced by the intraarticular mBSA injection triggering arthritis in control animals. Conclusions: Administration of IFN-a has a profound effect on the cellular response to mBSA plus adjuvant, but does not affect antigen-specific Ig production. By including IFN-alpha at immunizations, spleen and lymph node cells inhibit their repertoire of antigen-induced proinflammatory cytokines while enhancing antiinflammatory TGF-beta production, first in macrophages, and later also in CD4(+) T cells. On intraarticular antigen challenge, this antiinflammatory state is reenforced, manifested as inhibition of proinflammatory recall responses and preservation of TGF-beta levels. This may explain why IFN-alpha protects against antigen-induced arthritis.