Tumor necrosis factor receptor superfamily member 5 (CD40)–CD40 ligand (CD40L) protein-protein interface (CD40–CD40L PPI)

The Tumor necrosis factor receptor superfamily member 5 (CD40)–CD40 ligand (CD40L) protein-protein interface is a fundamental costimulatory signaling axis within the immune system (UniProt: P25942, P29965). CD40 is a receptor expressed on B cells, dendritic cells, and macrophages, while its partner, CD40L (also known as CD154), is primarily expressed on activated T helper cells (PMID: 19144319). The physical interaction between these two proteins is essential for the "second signal" in B-cell activation, driving processes such as immunoglobulin class switching, germinal center formation, and the development of high-affinity memory B cells (PMID: 9486989). Beyond humoral immunity, this interface mediates the activation of antigen-presenting cells, enhancing their ability to prime T-cell responses and produce pro-inflammatory cytokines. Pathologically, overactivity of the CD40–CD40L pathway is a hallmark of various autoimmune diseases, including systemic lupus erythematosus and rheumatoid arthritis, and plays a significant role in the rejection of transplanted organs (PMID: 15162400). Therapeutic targeting of this interface aims to disrupt these costimulatory signals to induce immune tolerance or reduce inflammation. While early attempts to block CD40L with monoclonal antibodies like ruplizumab were associated with severe thromboembolic events due to CD40L expression on platelets, modern drug development has shifted toward anti-CD40 antibodies (e.g., iscalimab) or Fc-engineered anti-CD40L fragments (e.g., dapirolizumab pegol) to improve safety profiles (PMID: 30631114). In oncology, agonistic antibodies targeting CD40 are also being explored to stimulate anti-tumor immunity by activating dendritic cells and enhancing T-cell priming. Overall, the CD40–CD40L interface represents a high-value target for modulating immune responses across a broad spectrum of clinical indications.

Other names

CD40-CD154 interactionTNFRSF5-TNFSF5 interactionCD40-CD40L axisCD40-CD40 ligand complexCD154-CD40 interaction

Blockade of the costimulatory interaction between CD40 and CD40 ligand to inhibit B-cell activation and pro-inflammatory cytokine production (antagonism), or activation of CD40 to enhance anti-tumor immune responses (agonism).