Elevated serum IL-35 levels in rheumatoid arthritis are associated with disease activity

To investigate serum interleukin (IL)- 35 levels in patients with rheumatoid arthritis (RA) and to describe the association between serum IL-35 levels and clinical parameters: erythrocyte sedimentation rate (ESR), C reactive protein (CRP), global health on Visual Analog Scale, Disease Activity Score in 28 joints based on ESR (DAS28-ESR), rheumatoid factor (RF) and anticyclic citrullinated peptide antibodies (ACPAs). The study included 129 patients with RA and 83 healthy controls. Serum IL-35 levels were detected by ELISA. ESR and CRP were measured by the Westergren method and the immune transmission turbidity method, respectively. RF and ACPA were measured using immunoturbidimetric assays and chemiluminescence analysis, respectively. The results showed that serum IL-35 levels were elevated in patients with RA. Univariate and multivariate analyses showed that the high serum IL-35 levels were correlated with low ESR and DAS28-ESR. These suggested that IL-35, an important anti-inflammatory cytokine, may participate in the regulation of the pathogenesis of RA, especially with disease activity.