Programmed death-ligand 1 (PD-L1) is a transmembrane protein that binds to the inhibitory receptor programmed death 1 receptor (PD-1), causing a down regulation of immune responses. PD-L1 is typically expressed on normal cells but has been observed in immune cells and tumor cells, see [1], while PD-1 is typically expressed on cytotoxic T-cells and other immune cells. Tumor cells can upregulate PD-L1 expression and avoid being attacked by the body’s immune system, making an interruption of the PD-1/PD-L1 interaction an attractive method for assisting the immune system in destroying tumor cells, see [2].
This APP can be used to determine the proportion of PD-L1 positive cells. It quantifies all cells and classifies PD-L1 positive cells based on brown/DAB positive membrane staining.