Foam cell

Foam cells are cells in an atheroma derived from both macrophages and smooth muscle. In chronic hyperlipidemia, lipoproteins aggregate within the intima of blood vessels and become oxidized by the action of oxygen free radicals generated either by macrophages or endothelial cells. The macrophages engulf oxidized low-density lipoproteins (LDLs) by endocytosis via scavenger receptors, which are distinct from LDL receptors. The oxidized LDL accumulates in the macrophages and other phagocytes, which are then known as foam cells. Foam cells form the fatty streaks of the plaques of atheroma in the tunica intima of arteries.

Foam cells are not dangerous as such, but can become a problem when they accumulate at particular foci thus creating a necrotic centre of atherosclerosis. If the fibrous cap that prevents the necrotic centre from spilling into the lumen of a vessel ruptures, a thrombus can form which can lead to emboli occluding smaller vessels. The occlusion of small vessels results in ischemia, and contributes to stroke and myocardial infarction, two of the leading causes of cardiovascular-related death.