PDCD1 and neoplasm: Besides, PD-1-deficient CD19-specific CAR-T cells showed elevated anti-tumor activity against and improved clearance of CD19+ PD-L1+ K562 myelogenous leukemia cells in NOD-SCID-IL-2Rγ−/− (NSG) mice compared to the conventional CD19-specific CAR-T cell [121].