Association of serum interleukin-17 and interleukin-23 levels with disease activity in Chinese patients with ankylosing spondylitis

BACKGROUND: Ankylosing spondylitis (AS) is a chronic arthritis with a pathogenesis which is not fully understood. A third subset of IL-17-producing T helper cells, called Th17 cells, has been discovered and characterized. We investigated whether IL-17 and IL-23, two Th17-related cytokines, play any roles in the pathogenesis of, and have any correlations with, disease activity and clinical manifestations in AS. METHODS: This cross-sectional study included 49 AS patients and 25 healthy control subjects. The serum IL-17 and IL-23 levels were measured using enzyme-linked immunosorbent assay kits. At the same time, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI) and Bath Ankylosing Spondylitis Patient Global Score (BAS-G) levels were measured, and physical examinations were performed on study participants to determine their extent of physical mobility. RESULTS: The serum IL-17 and IL-23 levels of the AS patients were significantly higher than those of the healthy controls. In the AS patients, the BASDAI scores had a better correlation with the serum IL-17 or IL-23 levels (IL-17, r = 0.351, p = 0.014; IL-23, r = 0.398, p = 0.005) than with ESR (r = 0.078, p = 0.600) and CRP (r = 0.012, p = 0.993). IL-17 or IL-23 correlate to the BASFI, BAS-G and parameters related to physical mobility. In the receiver operating characteristic (ROC) analysis, the serum IL-17 and IL-23 levels act better in discriminating patients with BASDAI≥4 (AUC value 0.88, p = 0.001) than ESR and CRP (AUC value 0.727, p = 0.008). CONCLUSION: Serum IL-17 and IL-23 levels were significantly higher in AS patients than in healthy controls and the levels correlate to disease activity measured by BASDAI scores, but not parameters of functional ability and spinal mobility. These results suggest the existence of a role of IL-17 and IL-23 in the pathogenesis of inflammation in AS.