IL-35 is essential for protection against collagen-induced arthritis (CIA) following intervention with Escherichia coli colonization factor antigen I (CFA/I) fimbriae (116.2)

Mucosal intervention with CFA/I fimbriae effectively diminishes CIA by stimulation of TGF-β+ and IL-10+ regulatory CD39+CD4+ T cells (Tregs), resulting in suppression of Th1 and Th17 cells and IL-27. CFA/I also stimulates Tregs expressing p35 and EBI3 subunits simultaneously, suggesting an essential role of IL-35 in CFA/I-mediated protection. We hypothesize CFA/I fimbriae stimulate endogenous IL-35 production to facilitate protection against autoimmune disease. In testing the relevance of endogenous IL-35 for protection, oral delivery of recombinant CFA/I into EBI3-/- mice on day 14 after CIA induction was found ineffective against CIA compared to similarly treated WT mice, as evidenced by the lack of suppression of IL-17 and IFN-γ (the latter increased 5-fold ). CFA/I-treated EBI3-/- mice lacked enhanced CREB phosphorylation that, in turn, failed to stimulate the transcription of CD39 (apyrase). In fact, surface apyrase activity by EBI3-/- CD4+ T cells was uninduced. Because of the lack of induced CD39 expression, IL-10 production was greatly diminished. Clinical improvement of CIA in CFA/I-treated EBI3-/- mice required further intervention with recombinant IL-35, resulting in the induction of CD39+CD4+ T cells, enhanced TGF-β production, and reduction in IFN-γ and IL-17. Thus, in the absence of endogenous IL-35, mucosal CFA/I fimbriae intervention is ineffective against autoimmune arthritis. Supported by AT-004986.