Introduction: Systemic lupus erythematosus (SLE) is a prototypic systemic autoimmune disease characterized by various immunological abnormalities, including dysregulated activation of both T and B lymphocytes. The etiology of this immunological disorder has not been clearly elucidated. Aberrant production and imbalance of T-helper (Th) cell cytokines have been implicated in the pathogenesis of autoimmunity. The aim of this study is to evaluate the level of Th1 cytokines interleukin-18 (IL-18) and osteopontin (OPN) in SLE patients and their correlation with the disease activity.
Methods: The study included 24 patients with SLE and 20 age- and sex- matched control subjects. The disease activity was evaluated with the SLE disease activity index (SLEDAI). Plasma OPN and IL-18 concentrations were measured in patients and control groups using an enzyme linked immunosorbent assay.
Results: Plasma OPN and IL-18 concentrations were significantly higher in SLE patients than in the control group (P < 0.001). OPN and IL-18 concentrations correlated positively and significantly with SLEDAI scores in SLE patients (r = 0.831, P < 0.001 and r = 0.826, P < 0.001 respectively). In addition, there was a highly significant positive correlation between OPN and IL-18 levels (r = 0.75, P < 0.001).
Conclusion: The circulating IL-18 and OPN concentrations were significantly elevated in SLE patients and correlated with the SLEDAI score. This suggests a crucial role for Th1 cytokines in the inflammatory processes and tissue damage in SLE disease. Both cytokines my act as potential disease markers for monitoring of SLE disease activity and therapeutic efficacy.
Keywords: SLE, Th-1, SLEDAI, osteopontin, IL-18