PDCD1 and neoplasm: In this model, PD-L1 forms only a temporal molecular shield to protect PD-L1+ tumor cells, and the cytolytic function of T cells against other PD-L1− tumor cells with the same antigen is not impaired (77), likely because a close proximity between PD-1–PD-L1 and immunologic synapses is required for PD-L1 function to disturb the T-cell receptor (TCR)–major histocompatibility complex (MHC) interaction.