Programmed cell death protein 1 (PD-1), also known as cluster of differentiation 279 (CD279), belongs to the CD28 superfamily and is a cell surface protein that plays a critical role in mediating immune responses of T cells and pro-B cells. PD-1 is usually expressed on various T cells. Its ligands (PD-L1 or PD-L2) are often found in dendritic cells (DCs) or macrophages. The binding of PD-1 to its ligands can trigger the T cells' activation and tolerance in different types of diseases, such as autoimmune diseases and cancers. Moreover, pilot studies have revealed that the PD-1 can be treated as key immune checkpoint molecules and exerts a broader range of immune-regulatory roles in disease development. For instance, many studies have illustrated that the interaction between PD-1 and PD-L1/PD-L2 can protect the human body from diseases by killing pathogens or harmful cells. Therefore, PD-1 and its ligand have been considered as a new therapeutic strategy for disease immunotherapy.

Learn more: PD-1 Therapy