Effect of interleukin (IL)-35 on IL-17 expression and production by human CD4+ T cells

Background Interleukin (IL)-17 produced by mainly T helper 17 (Th17) cells may play an important destructive role in chronic periodontitis (CP). Thus, anti-inflammatory cytokines, such as IL-35, might have a beneficial effect in periodontitis by inhibiting differentiation of Th17 cells. Th17 differentiation is regulated by the retinoic acid receptor-related orphan receptor (ROR) α (encoded by RORA ) and ROR γ t (encoded by RORC ). However, the role of IL-35 in periodontitis is not clear and the effect of IL-35 on the function of Th17 cells is still incompletely understood. Therefore, we investigated the effects of IL-35 on Th17 cells. Methods Peripheral blood mononuclear cells (PBMCs) were sampled from three healthy volunteers and three CP patients and were analyzed by flow cytometry for T cell population. Th17 cells differentiated by a cytokine cocktail (recombinant transforming growth factor- β , rIL-6, rIL-1 β , anti-interferon (IFN)- γ , anti-IL-2 and anti-IL-4) from PBMCs were cultured with or without rIL-35. IL17A (which usually refers to IL-17), RORA and RORC mRNA expression was analyzed by quantitative polymerase chain reaction, and IL-17A production was determined by enzyme-linked immunosorbent assay. Results The proportion of IL-17A + CD4 + slightly increased in CP patients compared with healthy controls, however, there were no significant differences in the percentage of IL-17A + CD4 + as well as IFN- γ + CD4 + and Foxp3 + CD4 + T cells between healthy controls and CP patients. IL17A , RORA and RORC mRNA expression was significantly increased in Th17 cells induced by the cytokine cocktail, and the induction was significantly inhibited by addition of rIL-35 (1 ng/mL). IL-17A production in Th17 cells was significantly inhibited by rIL-35 addition (1 ng/mL). Discussion The present study suggests that IL-35 could directly suppress IL-17 expression via ROR α and ROR γ t inhibition and might play an important role in inflammatory diseases such as periodontitis.