CD19 and neoplasm: Given that blockage of the PD1–PD-L1 pathway has been reported to improve the anti-tumour activity of CAR-T cells24–27, we set out to develop an enhanced type of CAR-T cells by integrating an anti-CD19 CAR sequence into the PD1 gene (PD1-19bbz) (Fig. 1a and Extended Data Fig. 2m,o–q).