Fig. 4
From: Trends and advances in tumor immunology and lung cancer immunotherapy
The mechanism of PD-1/PD-L1 pathway. Programmed cell death-1 (PD-1) receptor is expressed on the surface of activated T cells, B cells, monocytes, NK cells, and many TILs. Its ligand, PD-L1 is expressed on the surface of resting T cells, B cells, dendritic cells, macrophages, vascular endothelial cells, and pancreatic islet cells. The binding between PD-1 and PD-L1 leads to transmitting of an inhibitory signal into the T cell which reduces cytokine production and suppresses T-cell proliferation. PDL-1 is over expressed on tumor cells by which PD-1/PD-L1 interaction inhibits the proliferation, survival, and effector function of CTL and thus induces apoptosis of tumor-infiltrating T cells