Used in immunological research to study T-cell activation and regulation. Acts as a co-stimulatory molecule that binds to GITR on T cells, enhancing effector T cell function while suppressing regulatory T cell activity. Applied in cancer immunotherapy development to modulate immune responses. Also utilized in autoimmune disease research to understand immune tolerance mechanisms. Commonly employed in ELISA, cell-based assays, and protein-protein interaction studies due to its tagged Fc region, enabling easy detection and purification.