Used in immunological research to study T cell and NK cell activation pathways. Serves as a binding partner in protein-protein interaction assays, particularly in checkpoint signaling studies. Commonly applied in ELISA, surface plasmon resonance (SPR), and flow cytometry to analyze receptor-ligand interactions. The His tag facilitates easy purification and detection, making it suitable for in vitro assays and structural studies. Also utilized in the development and validation of therapeutic antibodies targeting immune checkpoints.