PD-1/PD-L1

PD-1 (CD279) is a type I transmembrane protein composed of 288 amino acid residues, belonging to the CD28 family. It is widely expressed on a variety of immune cells, such as activated T cells, B cells, NK cells and DC cells. PD-L1 (CD274) is a ligand of PD-1, that is, a protein that can pair and bind to PD-1. It consists of 290 amino acid residues, mainly including short cytoplasmic tail region, transmembrane region, and IgV and IGC-like extracellular domains. PD-L1 is expressed in tumor cells and antigen presenting cells (APC). PD-1 and its ligand PD-L1 pathway control the induction and maintenance of immune tolerance in the tumor microenvironment. PD-1/PD-L1 activity is responsible for the activation, proliferation and cytotoxic secretion of T cells in cancer, thereby reducing the degenerate anti-tumor immune response.