Interleukin-35 as a New Biomarker of Renal Involvement in Lupus Nephritis Patients.

Systemic lupus erythematosus (SLE) is an autoimmune connective tissue disease with a wide range of clinical presentations. Lupus nephritis (LN) is the most serious manifestation of SLE. Interleukin-35 (IL-35), a member of the interleukin-12 family, has been identified as a novel anti-inflammatory cytokine. In the past ten years, the role of IL-35 in inflammatory and autoimmune diseases has been studied extensively. Serum IL-35 levels, however, have not been studied in LN patients. The aim of the study was to determine serum IL-35 levels in SLE patients with and without nephritis, and their clinical values. The study was carried out on 120 SLE patients, which comprised 80 LN patients and 40 SLE patients without nephritis. SLE disease activity was measured according to Systemic Lupus Erythematosus Disease Activity Index-2 k (SLEDAI-2 k). Statistical evaluation was based on Mann-Whitney U-test, t-test, chi-square test, Spearman rank correlation test and Pearson's correlation test. The result showed that active SLE patients (n = 65) have lower serum IL-35 levels, compared to inactive SLE patients (n = 55, P < 0.001). Furthermore, serum IL-35 levels were significantly lower in LN patients (n = 80) than SLE patients without nephritis (n = 40, P = 0.013). Serum IL-35 levels had significant correlations with SLEDAI-2k (r = -0.626, P < 0.001) in SLE patients and estimated glomerular filtration rate (eGFR) (r = 0.348, P = 0.002) in LN patients. These results indicate that IL-35 is a potential biomarker of renal involvement in LN patients.