CD4 and juvenile idiopathic arthritis: Only T-cell cluster 4 (CD4-PD−1highTIGIT+, Figs. 4G, 6C) showed a statistical difference in PB when analysed against clinical activity, with increased frequency in PB samples from active compared to inactive JIA (0.11 ± 0.03% of CD3+ in inactive JIA PB vs 0.24 ± 0.04% of CD3+ in active JIA PB, P = 0.0054, Fig. 6C).