PDCD1 and cancer: The critical immune suppressive role for full-length PD-L1, bound on the membrane of cells or exosomes, is amply demonstrated both in animal models, where genetic deficiency or antibody blockade results in severe phenotypes, and in the success of cancer immunotherapy based on blockade of the PD-L1 – PD-1 interaction (Chamoto et al., 2017; Chen et al., 2018; Francisco et al., 2010; Sharpe and Pauken, 2018; Sun et al., 2018).