Elevation of Serum IL-35 in Patients with Primary Sjögren's Syndrome

Interleukin-35 (IL-35) is a critical anti-inflammatory cytokine in autoimmune disease. In the current study, we aimed to investigate the serum IL-35 levels and its clinical association in patients with primary Sjögren's syndrome (pSS) and to investigate whether or not IL-35 participates in the pathogenesis of pSS. One hundred seventy-six pSS patients and 60 healthy controls (HCs) were recruited. Disease activity was assessed according to EULAR SS disease activity index. Serum IL-35 levels were quantified by enzyme-linked immunosorbent assay. The correlations between the serum IL-35 levels with the clinical parameters were analyzed by a Spearman's correlation test. The serum IL-35 levels in the patients with pSS were significantly increased compared with the HCs. The serum IL-35 levels were elevated in the patients with pSS. Strikingly, the serum IL-35 levels in pSS patients with short disease duration (<1 year) were significantly lower compared with HCs. However, the serum IL-35 levels in pSS patients with medium (1–2 year) and long disease duration (>2 years) were higher compared with HCs. We also found a positive correlation between expression of IL-35 and erythrocyte sedimentation rate, disease activity, and immunoglobulin G. Furthermore, the pSS patients with RF-positive showed high serum IL-35 levels. These findings suggest that IL-35 could play a key role in pSS pathogenesis. In addition, our results highlight the potential exploitation of IL-35 as a biomarker of disease activity and may represent a novel therapeutic agent for pSS.