Used in immunological research to study natural killer (NK) cell regulation by interacting with major histocompatibility complex (MHC) class I molecules. Enables detection and quantification of KIR receptor interactions through ELISA, flow cytometry, and surface plasmon resonance. Supports development of therapeutic antibodies and immune checkpoint modulators targeting NK cell activity in cancer and autoimmune diseases. The Fc tag facilitates purification and enhances stability in assay systems.