In response to atherogenic factors secreted by endothelial cells and leukocytes, including platelet-derived growth factor (PDGF)-BB, endothelin-1, thrombin, and IL-1, VSMCs proliferate massively, migrate into the intima, and modify the inflammatory phenotype in atherosclerosis and thus are the main cell type associated with arterial intimal thickening 127. This evidence concerns the gene IL1B and atherosclerosis.