PDCD1 and neoplasm: Blocking the PD-1/PD-L1 interaction with monoclonal antibodies restores T cell function, enhancing the immune system’s ability to detect and destroy cancer cells.386,387 The primary action of PD-1/PD-L1 inhibitors involves blocking the interaction between PD-1 on T cells and PD-L1 on tumor cells, which enhances T cell activation and promotes anti-tumor responses.