 CD40 is constitutively expressed by antigen presenting cells, including dendritic cells, B cells and macrophages.It can also be expressed by endothelial cells, smooth muscle cells, fibroblasts and epithelial cells.Consistent with its widespread expression on normal cells, CD40 is also expressed on a wide range of tumor cells, including non-Hodgkin's and Hodgkin's lymphomas, myeloma and some carcinomas including nasopharynx, bladder, cervix, kidney and ovary.