Cluster 9 (CD8+, Supplementary Fig. S7A) denotes a small fraction of T cells with high expression of HLA-DR and CD39 but low CD226 expression (0.04% ± 0.21 of SF, 0.0% of HC/JIA PB T cells, Fig. 4E and G). Here, ENTPD1 is linked to juvenile idiopathic arthritis.