Macrophage scavenger receptors have been implicated both in the deposition of lipoprotein cholesterol in artery walls during the formation of atherosclerotic plaques and in host defense against pathogenic infections. The receptor's unusual ability to bind tightly to a very wide variety of ligands and its novel mosaic structure comprising (z-helical coiled-coil, collagenous and cysteine-rich domains are described. cholesterol and cholesteryl esters. The macrophages and smooth muscle cells in plaques are often filled with cholesteryl ester-rich foam-like fat droplets which give these foam cells a distinctive microscopic appearance. By protruding into the lumen of a coronary artery, a plaque can narrow the lumen and thus reduce blood flow (one cause of angina) and increase the likelihood of blockage by a blood clot (a major cause of heart attacks).