Activation of the CD40/CD40L system is considered a key step in the development of atherosclerosis and its complications and is associated with the synthesis of adhesion molecules and chemokines by monocytes/macrophages, endotheliocytes, platelet-leukocyte adhesion, increased expression of tissue factor and matrix metalloproteinases, and activation and proliferation of vascular smooth muscle cells [15,43,44]. The gene discussed is CD40LG; the disease is atherosclerosis.