– CD40 ligand or CD40L, also called CD154,  is a protein that is primarily expressed on activated T cells and is a member of the TNF superfamily of molecules. It binds to CD40 (protein) on antigen-presenting cells (APC), which leads to many effects depending on the target cell type. In total CD40L has three binding partners: CD40, α5β1 integrin and αIIbβ3. CD154 acts as a costimulatory molecule and is particularly important on a subset of T cells called T follicular helper cells. CD40 Ligand Protein (Primary Amine Labeling), Human, Recombinant (His & Flag), Biotinylated is expressed in HEK293 mammalian cells with N-His-Flag tag. The predicted molecular weight is 52.4 kDa and the accession number is P29965.