CD4 and juvenile idiopathic arthritis: Tregs were significantly increased in frequency in SF (19.4 ± 1.6% of SF CD4+ CD3+ cells vs 4.4 ± 0.4% of HC PB and 4.3 ± 0.3% of JIA PB CD3 + CD4+ cells, Fig. 5A), but in addition, five Treg clusters 4, 7, 9–11 were limited to SF, while Treg clusters 1, 5, 8, 12–14 predominated in PB (Fig. 5B and C).