Human PDL1

PDL1 is one of the ligands for PD-1 and plays a critical role in the regulation of T cell immunity. Mature human PDL1 protein is is expressed on inflammatory-activated immune cells including macrophages, T cells, and B cells, keratinocytes, endothelial and intestinal epithelial cells, as well as a variety of carcinomas and melanoma. The PD-1:PD-L1 interaction initiates a negative signaling cascade in T cells leading to inhibition of T cell activation. Many cancers exhibit upregulated PD-L1 protein expression, and several cancers with high levels of PD-L1 have been associated with increased tumor aggressiveness and poor prognosis. Using new therapeutics that block the PD-L1:PD-1 interaction has proven successful in the clinic for many cancer types and has sparked great interest in the field of cancer immunotherapy （1-5）.