Used in immunological research to study immune checkpoint pathways, particularly in the development and testing of cancer immunotherapies. Functions as a soluble receptor to block PD-L1/PD-L2 interactions, enabling assessment of T-cell activation and immune response modulation. Commonly employed in binding assays, protein-protein interaction studies, and in vitro functional assays to evaluate therapeutic antibodies targeting the PD-1 pathway. Also utilized in structural studies due to its tagged format, facilitating detection and purification.