Programmed cell death protein 1
Programmed cell death protein 1 (PD-1) (CD279 cluster of differentiation 279) is a protein encoded in humans by the PDCD1 gene. PD-1 is a cell surface receptor on T cells and B cells that has a role in regulating the immune system's response to the cells of the human body by down-regulating the immune system and promoting self-tolerance by suppressing T cell inflammatory activity.
Source: Wikipedia — Programmed cell death protein 1 (CC BY-SA 4.0)