Programmed cell death protein 1, also known asPD-1andCD279(cluster of differentiation279), is a cell surface receptor that plays an important role in down-regulating the immune system and promoting self tolerance by suppressing T cell inflammatory activity. PD-1 is an immune checkpoint and guards against autoimmunity through a dual mechanism of promotingapoptosis(programmed cell death) inantigenspecific T-cells inlymph nodeswhile simultaneously reducing apoptosis inregulatory T cells(anti-inflammatory, suppressive T cells).
So PD-1 inhibits the immune system. This prevents autoimmune diseases, but it can also prevent the immune system from killing cancer cells.
A new class of drugs that block PD-1, thePD-1 inhibitors, activate the immune system to attack tumors and are therefore used with varying success to treat some types of cancer.
PD-L1, the ligand for PD1, is highly expressed in several cancers and hence the role of PD1 in cancer immune evasion is well established.Monoclonal antibodiestargeting PD-1 that boost theimmune systemare being developed for the treatment ofcancer.Many tumor cells express PD-L1, an immunosuppressive PD-1 ligand; inhibition of the interaction between PD-1 and PD-L1 can enhance T-cell responsesin vitroand mediate preclinical antitumor activity. This is known asimmune checkpoint blockade.
Combination therapy using both anti-PD1 along with anti-CTLA4therapeutics have emerged as important tumor treatments within the field ofcheckpoint inhibition