Apolipoprotein A1 (ApoA1) is a 28 kDa glycoprotein that is the major protein component of high density lipoprotein (HDL) particles. HDL particles play a central role in the reverse transport of cholesterol from peripheral tissues to the liver. HDL is known as “good cholesterol” due to its ability to facilitate the removal of cholesterol from macrophage foam cells in atherosclerotic plaques and thereby retard the progression of disease. ApoA1 is secreted from hepatocytes with variable amounts of lipidation.