PDCD1 and neoplasm: TRAC-B2M-PD1 triple- and TRAC-B2M double-knockout GD2 CAR T cells lysed tumor targets at a similar efficacy, while non-CAR transduced, TRAC-B2M-PD1 triple-, and TRAC-B2M double-knockout T cells showed no cytotoxicity, indicating the need for antigen specificity by the CAR and the inability for allogeneic cytotoxicity due to a lack of a TCR (Figure 4B).