Programmed cell death protein 1 Simoa

Programmed cell death-1 (PD-1), also known as CD279, is the receptor for two ligands, programmed death ligand 1 (PD-L1) and programmed death ligand 2 (PD-L2). Membrane bound PD-1 is expressed mainly on T cells and B cells and is upregulated on activated T cells after induction by antigen stimulation. This upregulation is a normal mechanism to prevent unregulated T cell activation and is a major mechanism for T cell exhaustion. However, in the cancer microenvironment, high expression of PD-1 from infiltrating T cells will lead to suppression of anti-cancer immune responses. Similar immune suppression mechanism has also been found during chronic infectious diseases. Membrane bound PD-1 have splice variants that can lead to soluble forms of PD-1 (sPD-1). Under normal circumstances and in healthy subjects, sPD-1 is not detectable. Only a handful of studies have conducted on correlating sPD-1 with cancer or infectious diseases. Circulating sPD-1 is elevated in certain types of cancer, and the level of sPD-1 can be affected by treatment. Additionally, for chronic viral infections such as HBV and HCC, sPD-1 has been correlated with viral load. In cancer, since over expression of membrane bound PD-1 can lead to suppression of T cell activity, several anti-PD-1 biologics (pembrolizumab, nivolumab, cemiplimab) are available for cancer. Patient response to anti-PD-1 is low across the population, a biomarker to predict responses to anti-PD-1 therapy is a critical need.

Swiss-Prot Accession Number: Q15116