IL-35 is a newly discovered immunoregulatory cytokine that possesses the ability to inhibit CD4 + effector T cells and alleviate autoimmune diseases. The objective of this study was to investigate IL-35 levels in patients with primary Sjogren's syndrome (pSS) and explore the roles of IL-35 in the pathogenesis of pSS.
Thirty-four hospitalized patients with pSS were recruited, and 34 volunteers were enrolled as healthy controls. An ELISA was adopted to measure plasma IL-35 levels. The levels of P35 and EBI3 mRNAs in peripheral blood mononuclear cells (PBMCs) were determined using real-time quantitative PCR. The percentage of CD4 + EBI3 + T cells and CD19 + EBI3 + B cells was analysed using flow cytometry. Correlations between IL-35 levels, P35 and EBI3 mRNAs, numbers of CD4 + EBI3 + T cells, CD19 + EBI3 + B cells and clinical parameters were analysed.
Significantly lower plasma IL-35 levels, P35 and EBI3 mRNA levels, and percentages of CD4 + EBI3 + T cells but increased percentages of CD19 + EBI3 + B cells were observed in patients with pSS than in healthy controls. IL-35 levels, EBI3 mRNA expression and the percentage of CD4 + EBI3 + T cells exhibited negative correlations with the ESSDAI score, whereas levels of the IL-35 protein and EBI3 mRNA were negatively correlated with the ESR. Patients who were positive for anti-SSB antibodies presented with lower IL-35 levels and percentages of CD4 + EBI3 + T cells.
Based on these results, a decrease in the IL-35 levels may play an important role in the pathogenesis of pSS. IL-35 may act as a potential therapeutic agent against inflammation in patients with pSS.