HDL and immunomodulation: an emerging role of HDL against atherosclerosis.

Changes in plasma lipoprotein profiles, particularly low levels of high-density lipoprotein (HDL) cholesterol, are associated with several inflammatory and immune diseases, including atherosclerosis and rheumatoid arthritis, implying the potential link between HDL and immunity. Accumulating evidence suggests that HDL possesses anti-inflammatory effects and has an important function in host defense as part of the innate immune system. In addition, HDL inhibits the ability of antigen-presenting cells (APCs) to stimulate T cells. It is subsequently discovered that HDL or HDL-associated platelet-activating factor-acetylhydrolase can restore the emigratory process of monocyte-derived dendritic cells and thus result in resolution of inflammatory reactions in atherosclerotic plaques. Lipid rafts in plasma membrane are the key structure responsible for the immunomodulation effects of HDL, the remarkable ability of HDL to regulate innate and adaptive immune responses extends our understanding of its atheroprotective role, and provides new therapeutic approaches to atherosclerosis and other inflammatory conditions.