Background/Purpose: There is accumulating evidence that the Th17-signaling axis, particularly interleukin-17 (IL-17), plays an important role in the pathogenesis of ankylosing spondylitis (AS). Furthermore, biologics targeting IL-17 have shown clinical efficacy  inactive AS. The purpose of the current study was to investigate the association of IL-17A and IL-17F serum levels with clinical, laboratory and radiographic parameters in patients with AS.

Methods: 50 anti-TNF-naïve patients with AS, as defined by the modified New York criteria, with symptom duration of ≤10 years and clinically active disease (BASDAI ≥4), were selected from German Spondyloarthritis Inception Cohort (GESPIC) for this study. Available spinal radiographs (baseline and after 2 years, n=28) were scored according to the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS), by two independent blinded readers. Baseline serum levels of IL-17A and IL-17F were measured by the ultra-sensitive Erenna Immunoassay (Singulex, Almeda, CA).

Results: The mean (±SD) serum levels of IL-17A and IL-17F in the studied population were 0.87±1.48 pg/ml and 7.36±20.8 pg/ml, respectively. There was a significant correlation of serum cytokine levels with each other: Spearman’s rho = 0.490, p<0.001. Serum level of IL-17A showed a significant correlation with the serum level of C-reactive protein: rho = 0.327, p = 0.020, while IL-17F correlated with erythrocyte sedimentation rate: rho = 0.331, p = 0.026. Also, there was a negative correlation of IL-17A with patients’ age: -0.318, p = 0.025. Serum IL-17A level was significantly higher in HLA-B27 positive patients (n=39): 1.01±1.65 pg/ml vs. 0.36±0.24 pg/ml in negative ones, p = 0.021. Similar trend was observed also for IL-17F: 8.29±23.43 pg/ml vs. 4.08±3.80 pg/ml, respectively, p=0.29. A trend for a higher IL-17A serum level was found in patients with peripheral arthritis (n=7): 1.45±1.74 pg/ml vs. 0.79±1.44 pg/ml in patients without arthritis, p=0.37. No correlation between IL-17 serum levels and either symptom duration, sex, presence of enthesitis, levels of BASDAI and BASFI, smoking status, or presence and progression of structural damage in the spine was found.

Conclusion: IL-17 serum levels correlate with markers of systemic inflammation in patients with clinically active AS. IL-17A is significantly elevated in HLA-B27 positive patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/interleukin-17-serum-levels-are-associated-with-markers-of-systemic-inflammation-in-patients-with-active-ankylosing-spondylitis/