In contrast, CD40 is upregulated in various inflammatory disorders and, through ligand engagement, CD40 triggers pro-inflammatory responses in endothelial cells, vascular smooth muscle cells and epithelial cells that play a key role in the pathogenesis of various disorders such as inflammatory bowel disease, systemic lupus erythematosus, rheumatoid arthritis, multiple sclerosis, graft rejection, and atherosclerosis (22, 23). Here, CD40 is linked to atherosclerosis.