Researchers say circulating mononuclear cells (the largest type of white blood cell) and lymphocytes, exist in a proinflammatory state in obese persons known to be at increased risk of developing heart disease, diabetes, or both.
In the Injury Theory, it's damage to the arterial endothelium, followed by platelet activation, then smooth muscle cell migration to injury, then macrophages, with resulting "foam cells." Engorged foam cells burst, starting the injury cycle all over again