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.