PD-L1/CD274 Monoclonal antibody

PD-L1, also known as CD274 or B7H1, stands for programmed cell death ligand 1. It is a type I transmembrane protein that is thought to repress immune responses by binding to its receptor (PD1), thus inhibiting T-cell activation, proliferation, and cytokine production. It contains V-like and C-like immunoglobulin domains. PD-L1 expression is regulated by various cytokines, such as TNF-α or LPS (ISSN: 1848-7718). Increased expression of this protein in certain types of cancers, e.g., renal cell carcinoma or colon cancer, correlates with poor prognosis. 

What is the molecular weight of PD-L1? 

Depending on the isoform, the calculated molecular weight of the protein varies between 20 and 33 kDa (176-290 aa). 

What are the isoforms of PD-L1? 

According to NCBI, three different isoforms have been identified. There are significant differences in the untranslated and protein coding regions. 

What is the subcellular localization and tissue specificity of PD-L1? 

It is predicted to localize in the plasma membrane of various cell types, with a particularly high expression in placental trophoblast and subsets of immune cells. High levels of PD-L1 protein have also been detected in lung and colon tissues. 

What is the function of PD-L1 in immune responses? 

PD-L1 is critical for the induction and maintenance of immune self-tolerance during infection or inflammation in normal tissues. The interaction of PD-L1 and its receptors is responsible for preventing auto-immune phenotypes and balancing the overall immune response in situations such as pregnancy or tissue allografts. The interaction between PD-L1 and PD-1 or B7.1 starts an inhibitory signaling cascade, which results in the decreased proliferation of antigen-specific T-cells and increased survival of regulatory T-cells (PMID: 15240681). 

How can PD-L1's implication in cancer be used as a drug target? 

In certain tumors, high expression of PD-L1 serves as a stop-sign to inhibit the recognition of cancer cells by T-cells (PMID: 23087408). The interaction between PD-L1 and its receptors (PD1 and B7.1) is a mechanism for the tumor to evade the host immune response (PMID: 29357948). Several mAbs have been developed to target that interaction and thus prevent the inactivation of cytotoxic T-cells by the tumor (PMIDs: 23890059, 18173375).