PD-1

Programmed cell death protein-1 (PD-1) is a type I transmembrane protein that widely exists in the T cell, B cell, NK cell, macrophage, and dendritic cell. PD-1 is a co-repressor for T cells. Its binding to programmed cell death ligand-1 (PD-L1) will obstruct the P13K/AKT pathway, down-regulating the expression of cell survival related genes and thereby inhibiting T cell proliferation, activation, and cytokine secretion. Some research found that PD-1 and PD-L1 are highly expressed in various tumors, including gastric cancer, lung cancer, liver cancer, kidney cancer, breast cancer, ovarian cancer, and cervical cancer, which are closely related to the occurrence and development of tumors. This may be because the binding of PD-1 in tumor infiltrating lymphocytes and PD-L1 in cancer cells can reduce immune activity against tumors to trigger immune escape. Therefore, PD-1/PD-L1 blocking immunotherapy has become an important tumor therapy method. In addition, PD-1 can serve as a diagnostic biomarker for angioimmunoblastic T-cell lymphoma.