PDCD1 and neoplasm: We measured the surface expression of immune checkpoint receptors in CART (n = 4) after repeated challenge with autologous tumor cells and found significantly lower levels of TIM3 (*, P < 0.05; **, P < 0.01, two-way ANOVA with the Tukey test; Fig. 4I; Supplementary Fig. S5E and S5F) and a trend toward lower PD-1 in CARζ/CPR41BB cells.