Interleukin 35 regulates interleukin 17 expression and T helper 17 in patients with proliferative diabetic retinopathy.

T helper 17 (Th17) cells regulate inflammatory processes and are implicated in pathogenesis of proliferative diabetic retinopathy (PDR) through modulation of interleukin-17 (IL-17). IL-35, anti-inflammatory factor, negatively mediates IL-17 expression and Th17 differentiation. In this study, the role of IL-35 in PDR was assessed. The results showed that IL-35 was down-regulated, while IL-17 was up-regulated, in peripheral blood mononuclear cells (PBMCs) of PDR patients. In addition, immunofluorescence analysis indicated that frequency of Th17 cells was enhanced in the PBMCs of PDR patients. However, incubation with IL-35 reduced the Th17 cell frequency and decreased the level of IL-17 in CD4 T lymphocytes. Moreover, the levels of transcription factors essential for Th17 differentiation, ROR α (retinoid-related orphan receptor alpha) and ROR γt, were reduced by IL-35 treatment. In conclusion, IL-35 reduced level of IL-17 and inhibited Th17 differentiation to protect against PDR.