Serum Levels of IL-17, IL-6, TNF-α and Disease Activity in Patients with Rheumatoid Arthritis

Abstract

Objective: The aim of this study was to evaluate serum levels of interleukin (IL)-17, IL-6, and tumor necrosis factor alpha (TNF-α) in RA patients and to assess the correlation of these cytokines with clinical and laboratory parameters. Materials and Methods: 48 patients with RA and 35 healthy volunteers were enrolled in the study. Disease activity was determined by disease activity score (DAS28) in patients with RA. Patients with RA were categorized as mild (DAS28≤3.2), moderate (3.2 0.05). Serum IL-6 levels were significantly elevated in RA patients compared with controls (P<0.001). The increasing trend in mean serum IL-6 levels across group with mild, moderate, and severe disease activity was significant (P<0.001, respectively). In RA patients, serum IL-6 concentrations were significantly correlated with ESR, CRP, DAS28, and VAS (r=0.371, P=0.009; r=0.519, P<0.001; r=0.536, P<0.001; r=0.539, P<0.001, respectively). Also, Serum IL-17 concentrations demonstrated significant correlations with ESR, CRP, but not DAS28 (r=0.349, P=0.015; r=0.299, P=0.039; r=0.274, P=0.060, respectively). Serum TNF-α showed no significant correlation with disease activity indices. Conclusions: This study showed that patients with RA had significantly increased cytokine level for IL-6, but not IL-17 and TNF-α and high level of serum IL-6 cytokine was associated with disease activity. However, further follow-up studies involving large samples are required to clarify precise role of these cytokines in disease development and progress.