Used in immunological research to study B-cell activation and dendritic cell maturation. Serves as a ligand for CD40L in assays evaluating immune response pathways. Employed in the development of therapeutic antibodies targeting the CD40-CD40L interaction for autoimmune diseases and cancer immunotherapy. Supports the culture and expansion of antigen-presenting cells in vitro. Applied in ELISA and surface plasmon resonance (SPR) to measure binding affinity with interacting partners. Facilitates high-throughput screening of inhibitors or modulators of CD40 signaling.