CD40, also known as Tumor necrosis factor receptor superfamily member 5 (TNFRSF5), is a 32 kDa cell surface receptor expressed by B-cells, dendritic cells, macrophages and other antigen-presenting cells. CD40 consists of N-terminal extracellular domain and C-terminal transmembrane domain. The mouse CD40 shares 61.2% of sequence identity with human CD40. Interaction between CD40 and CD40L activates antigen-presenting B-cells to produce antibody. CD40 is expressed in multiple cancer cell lines including lymphomas and myeloma.
