Used in immunological research to study immune checkpoint pathways, particularly the PD-1/PD-L1 interaction that regulates T-cell activation and tolerance. Commonly employed in binding assays, ELISA, and surface plasmon resonance (SPR) to measure interactions with PD-1 and other binding partners. Supports development and testing of therapeutic antibodies and inhibitors targeting the PD-L1 pathway for cancer immunotherapy. The Fc tag allows for easy detection and purification, and enables cross-linking or immobilization on Fc receptor-coated surfaces. Also used in cell-based assays to modulate immune responses and evaluate T-cell suppression or activation.