Used to measure levels of PD-L1 (programmed death-ligand 1) in human biological samples such as serum, plasma, or cell culture supernatants. This ELISA kit is commonly applied in cancer research and immunology studies to monitor immune checkpoint activity. It helps assess the expression of PD-L1, a protein involved in suppressing immune responses, which is often overexpressed by tumor cells to evade detection by the immune system. The kit supports drug development and evaluation of immunotherapies targeting the PD-1/PD-L1 pathway. It is also used in clinical research to explore biomarkers for response to checkpoint inhibitors and in studies of autoimmune diseases and chronic infections where immune regulation is altered.