CTLA4 and neoplasm: Tumor-infiltrating PD-1+ CD8+ T cells in the A and D metaclusters had a terminally differentiated phenotype similar to that of FlowSOM cluster 5 that was characterized by high expression of genes encoding co-inhibitory molecules such as CTLA4, ENTPD1 (CD39), HAVCR2 (TIM-3), and LAG3, consistent with this population containing tumor-reactive cells (Figures 3E, 3F, and S4A).