PD-1/PD-Ls signaling pathway and the application of anti-PD-1/PD-Ls antibodies in cancer therapy

Programmed death-1(PD-1)is a major co-suppression receptor expressed on T cells. Binding with its ligands(PD-L1 and PD-L2), PD-1 can inhibit T cell proliferation, activation and cytokine secretion. In normal organs, PD-1/PD-Ls signaling pathway plays an important role in maintaining immune tolerance, while suppressing T cell immune response and promoting tumor immune escape during tumorigenesis. This article reviews the research progress on PD-1/PD-Ls signaling pathway from the structure and expression of PD-1/PD-Ls, the mechanism of the signaling pathway as well as the expression characteristics of soluble form of PD-1/PD-L1(sPD-1/sPD-L1), and summarizes the categories of anti-PD-1/ PD-Ls antibodies and their clinical trials in cancer immunotherapy.