Interleukin-32γ: Possible association with the activity and development of nephritis in patients with systemic lupus erythematosus

Aim Growing evidence suggests that interleukin (IL)-32 is a cytokine involved in various autoimmune diseases. We aimed to investigate whether IL-32 gamma is involved in systemic lupus erythematosus (SLE), particularly in patients with lupus nephritis (LN). Method Sera from SLE patients without LN (n = 47), LN patients (n = 19) and healthy controls (n = 10) were collected. The serum concentrations of inflammatory cytokines, including tumor necrosis factor-alpha, interferon-gamma, IL-6, IL-18, and IL-32 gamma, were measured using enzyme-linked immunosorbent assay. Clinical parameters at the time of sampling were obtained from medical records, and correlations between IL-32 gamma and clinical parameters were analyzed by Spearman correlation analysis. Immunohistochemistry evaluating IL-32 expression was performed in renal tissues of LN patients and healthy controls. Results Among the cytokines measured in sera, the level of IL-32 gamma was higher in LN patients than in SLE patients without LN and in healthy controls. Among clinical parameters, concentrations of C3/C4 were lower and erythrocyte sedimentation rate, C-reactive protein, anti-double-stranded DNA (anti-dsDNA) antibodies, and SLE Disease Activity Index-2000 (SLEDAI-2K) were higher in LN patients than in SLE patients without LN. IL-32 gamma level was negatively correlated with C3/C4 and positively correlated with anti-dsDNA antibodies and the renal component of SLEDAI-2K. In LN patients, IL-32 gamma level was positively correlated with the activity and chronicity indices. IL-32 expression was significantly higher in renal tissues of LN patients than in healthy controls. Conclusion IL-32 gamma could be associated with the activity and development of LN in SLE.