PDCD1 and neoplasm: Despite PD-1 expression on a fraction of the parental CD19+ K562 cell line (Supplementary Fig. 3a), there was no difference in growth kinetics of CD19+ and CD19+ PD-L1+ cells either in vitro (Supplementary Fig. 3b) or in vivo (Supplementary Fig. 3c), suggesting that ectopic PD-L1 expression did not significantly alter intrinsic tumor growth in this model22.