PDCD1 and neuroblastoma: The TRAC-B2M-PD1 triple-knockout GD2 CAR T cells were the only group that showed over 70% and 85% cytotoxicity at 60 and 72 h, respectively (Figure 4C), suggesting that the knockout of PD-1 may increase the potency for GD2 CAR T cells against neuroblastoma.