Used in immunological research to study T-cell activation and co-stimulatory signaling pathways. The recombinant human CD28 protein with Fc tag serves as a soluble form for binding studies with ligands such as CD80 and CD86, and is employed in protein-protein interaction assays, ELISA, and surface plasmon resonance (SPR) studies. Commonly used in the development and validation of therapeutic antibodies targeting the CD28 pathway. Supports the analysis of immune synapse formation and helps evaluate the functional activity of engineered T cells in immunotherapy research.