FOXP3 and juvenile idiopathic arthritis: Proportions of IL-17 producing CD4+ (median 0.8% vs. 0.3%) and FoxP3+CD4+ cells (median 2.85% vs. 0.6%) were higher in JIA compared to HC (p = 0.002, respectively) whereas cells characterizing the natural occurring Treg phenotype (FoxP3+, CD25+, CD127−) were on a similar level as in HC.