Increasing levels of circulating Th17 cells and interleukin-17 in rheumatoid arthritis patients with an inadequate response to anti-TNF-α therapy

Abstract

Introduction: The objective of this study was to investigate the effects of tumor necrosis factor (TNF)-α inhibitors on circulating T helper-type 17 (Th17) cells and Th17-related cytokines in patients with rheumatoid arthritis (RA).

Methods: The frequencies of circulating Th17 cells and serum levels of Th17-related cytokines were determined using flow cytometry analysis and ELISA, respectively, in 48 RA patients both before (baseline) and six months after anti-TNF-α therapy. Therapeutic response was evaluated using European League Against Rheumatism (EULAR) response criteria.

Results: Significantly higher baseline frequencies of circulating Th17 cells and serum levels of interleukin (IL)-6, IL-17, IL-21, IL-23 and TNF-α were observed in active RA patients than in 12 healthy controls (all P < 0.001). After anti-TNF-α therapy, 36 patients (75%) were EULAR responders (20 good responders and 16 moderate responders) and 12 (25.0%) were non-responders. The mean levels of circulating Th17 cells and IL-17 significantly decreased (1.13% vs. 0.79%; 43.1 pg/ml vs. 27.8 pg/ml; respectively, both P < 0.001) in parallel with clinical remission in responders. Levels of IL-6, IL-21, IL-23 and TNF-α were significantly decreased after anti-TNF-α therapy in responders. In contrast, the mean levels of circulating Th17 cells and IL-17 significantly increased after anti-TNF-α therapy (2.94% vs. 4.23%; 92.1 pg/ml vs. 148.6 pg/ml; respectively, both P < 0.05) in non-responders. Logistic regression analysis identified a high baseline level of IL-17 as a significant predictor of poor therapeutic response.

Conclusions: The beneficial effect of anti-TNF-α therapy might involve a decrease in Th17-related cytokines in responders, whereas rising levels of circulating Th17-cells and IL-17 were observed in patients with an inadequate response to anti-TNF-α therapy.

Figure 1

The comparison of circulating levels of Th17-cells and Th17-related cytokines between RA patients and HC. (A) Flow cytometric dot-plots of intracellular IL-17 production in Th cells obtained from peripheral blood of one representative patient with rheumatoid arthritis and healthy control. The comparison of circulating Th17 cells frequencies is shown (B) between 48 RA patients before starting anti-TNF-α therapy (baseline) and 12 HC. The comparison of baseline levels of serum IL-17 (C), IL-6 (D), IL-21 (E), and IL-23 (F) is shown between RA patients and HC. The horizontal line indicates median value. P-value was assessed by Mann-Whitney U test. HC, healthy control; IL, interleukin; RA, rheumatoid arthritis; Th17 cells, T helper-type 17 cells; TNF-α, tumor necrosis factor alpha.

Figure 2

The change in circulating levels of Th17-cells and Th17-related cytokines in EULAR responders and non-responders. The changes in (A) the frequencies of circulating Th17-cells (T helper-type 17 cells) and serum levels of (B) interleukin (IL)-17, (C) IL-6, (D) IL-21, (E) IL-23, and (F) tumor necrosis factor (TNF)-α in 36 responders and 12 non-responders to anti-TNF-α therapy according to European League Against Rheumatism (EULAR) response criteria. Bars represent the mean value and SEM. *P < 0.05, **P < 0.005, ***P < 0.001, versus before starting anti-TNF-α therapy, determined by the Wilcoxon signed rank test.#P < 0.01, non-responders versus responders.