ABSTRACT
<p><b>BACKGROUND</b>Interleukin-23 (IL-23) is a pro-inflammatory cytokine that is thought to be central to the development of autoimmune diseases. This study was conducted to determine whether or not the serum concentration of IL-23 is elevated in patients with rheumatoid arthritis (RA), and to determine the relationship between the IL-23 level and disease activity in RA patients.</p><p><b>METHODS</b>Serum samples were obtained from 59 patients with RA and 30 healthy controls. The clinical parameters of disease activity were determined, including the 28-joint disease activity score (DAS28), C-reactive protein (CRP), rheumatoid factor (RF) levels, and the degree of bony erosions based on X-rays. The levels of IL-23 and IL-17 were determined by enzyme-linked immunosorbent assay (ELISA). The correlations between the serum levels of IL-23 and disease activity parameters of patients with RA were determined.</p><p><b>RESULTS</b>The serum IL-23 level was significantly elevated in patients with RA compared to healthy controls. The serum IL-23 levels in the RA patients correlated with IL-17 and CRP levels, and the DAS28. The levels of IL-23 based on X-ray classification phase I, II, III, and IV were gradually elevated in RA patients.</p><p><b>CONCLUSIONS</b>The levels of serum IL-23 in RA patients were higher than in healthy controls. Thus, elevated serum IL-23 levels may be useful markers to detect active RA. In addition, IL-23 is involved in disease progression and bony erosions in patients with RA.</p>