PDCD1 and neoplasm: Interestingly, PD-1 blockade did not lead to a significant increase in the PD-1high hHER2-CAR-T cell number at the tumor site (Figure 5H), suggesting that the anti-PD-1 blocking antibody augmented the cytotoxic capability of PD-1high hHER2-CAR-T cells in vivo but not the recruitment and/or retention of the T cells at the tumor site.