The programmed death-1 receptor (PD-1) and its ligands PD-L1 and PD-L2 are central components of immune checkpoint mechanisms in cancer and are key targets for immunotherapy. PD-1, a transmembrane receptor found on various immune cells such as activated T cells, Tregs, B cells, NK cells, and myeloid cells, interacts with PD-L1 and PD-L2, which are expressed on a wide range of cells. This interaction plays a crucial role in immune regulation by promoting cell death. Blocking the PD-1/PD-L1 pathway has demonstrated enhanced anti-tumor responses in cancers like pancreatic carcinoma, melanoma, and colon carcinoma. Combining PD-1 blockade with CTLA-4 antibody treatments has led to significant tumor regression in many patients. The critical role of PD-1 in modulating immune responses within the tumor microenvironment highlights its potential as a target for cancer immunotherapy, offering greater efficacy and fewer side effects compared to CTLA-4 blockade.

Abbreviations:

PD-L1, programmed cell death 1 ligand 1, B7H1, PDCD1LG1, CD274 molecule, PDCD1L1, B7 homolog 1, CD274 antigen, PDCD1 ligand 1