CD40–CD40 ligand protein–protein interface (CD40–CD40L PPI)

The CD40–CD40 ligand (CD40L) protein–protein interface is a fundamental costimulatory axis that regulates the interaction between antigen-presenting cells (APCs), such as dendritic cells, and activated T lymphocytes. CD40 is a cell surface receptor belonging to the tumor necrosis factor receptor (TNFR) superfamily, while its partner, CD40L (also known as CD154), is a type II transmembrane protein primarily expressed on activated CD4+ T cells [1]. The engagement of CD40 by CD40L on dendritic cells induces "licensing," which enhances the expression of MHC molecules and costimulatory ligands like CD80 and CD86, thereby facilitating the priming of cytotoxic T cells and the production of pro-inflammatory cytokines like IL-12 [2]. This pathway is pivotal in the pathogenesis of various autoimmune conditions and the rejection of transplanted organs, where excessive signaling leads to chronic inflammation [3]. Consequently, therapeutic strategies include antagonistic antibodies or fusion proteins designed to disrupt this interface to treat systemic lupus erythematosus and rheumatoid arthritis [4]. In oncology, agonistic antibodies targeting CD40 are being developed to bypass T cell help and directly activate APCs to mount an effective anti-tumor immune response [5]. However, early clinical trials of CD40L-targeting agents were hampered by thromboembolic complications due to the presence of CD40L on platelets, necessitating the design of safer, non-thrombogenic alternatives [6]. Sources: [1] UniProt (P25942, P29965) [2] PubMed (PMID: 15123776) [3] PubMed (PMID: 28213676) [4] ClinicalTrials.gov (NCT02730442) [5] PubMed (PMID: 30635337) [6] PubMed (PMID: 12610196)

Other names

CD40–CD154 interactionCD40–TNFSF5 complexCD40–CD40L axisCD40–CD40 ligand costimulatory pathway

Therapeutic agents either block the interface to prevent costimulatory signaling between T cells and antigen-presenting cells (immunosuppression) or act as agonists to CD40 to mimic the interaction and enhance immune activation (immunotherapy).