Used in immunological research to study the regulation of T-cell activation and immune responses. Functions as a soluble receptor ligand to modulate signaling pathways involved in autoimmune diseases and cancer immunotherapy. Employed in binding assays and protein-protein interaction studies to evaluate checkpoint inhibitor targets. Supports development of therapeutic antibodies by serving as a target antigen in immunoassay development and validation. Commonly used in ELISA, SPR, and flow cytometry applications to assess binding kinetics and specificity.