PDCD1 and leukemia: Consistent with the prior preclinical studies in which PD-1 or PD-L1 blockade had an antileukemia effect (69, 70), we also observed modest reduction of in vivo growth of C1498FF–mPD-1H leukemia in WT mice following anti-mouse PD-1 (anti–mPD-1) mAb treatment compared with an isotype control (Figure 6A).