Programmed Death-Ligand 1 Simoa

Programmed death ligand 1 (PD-L1), also known as B7-H1 or CD274, is the ligand for programmed cell death 1 (PD-1). PD-L1 is expressed constitutively at low levels on resting lymphocytes, antigen-presenting cells, and specific tissue islet cells. The normal function of PD-L1 is to maintain homeostasis and to control inflammatory responses. Thus, the ligation of PD-L1/PD-1 is a major mechanism for immune tolerance, immune exhaustion, and immune evasion. Aberrant expression of membrane bound PD-L1 on cancer cells and infiltrating leukocytes in the tumor microenvironment has been correlated with poor prognosis. Additionally, pathogens that can cause chronic infections also exploit this pathway by inducing overexpression of PD-L1 on the infected host cell. PD-L1 can also exist as a soluble protein. Th soluble PD-L1 (sPD-L1) can be released from both cancer cells and immune cells and is known to bind to membrane bound PD-1. While sPD-L1 is detectable in normal serum and the levels can increase with age, there are numerous studies examining sPD-L1 as a biomarker in cancer. Increased sPD-L1 has been associated with cancer clinical stage, poor prognosis, and increased mortality risk. Due to the role of PD-L1 to suppress T cell activation, there are several anti-PD-L1 antibody therapy (atezolizumab, durvalumab, and avelumab) approved for cancer therapy. However, predicting patient response to biologics is a major unmet need to improving efficacy of anti-PD-L1 therapeutics.

Swiss-Prot Accession Number: Q9NZQ7