Figure 1.

Model of action of anti-PD-1/PD-L1 immunotherapy in tumor cells—T cells interaction theory. Tumor cells that express PD-L1 suppress cytotoxic function of PD-1 positive activated T cells through the PD-L1/PD-1 interaction. Therefore, the blockade of this pathway by anti-PD-1 drugs or by anti-PD-L1 drugs enables T cells to counterattack tumor cells.