Anti-inflammatory liaisons: T regulatory cells and HDLThe report in this issue of the Journal of Lipid Research by Rueda et al. shows that the survival and viability of Tregs is improved by incubation with HDL. Previous research over the last 20 years had demonstrated that plasma HDL possessed anti-inflammatory properties (1–4). Much of the early work focused on HDL as a vehicle to carry oxidized lipid products to the liver for catabolism as well as to inhibit the oxidation of LDL. Because HDL was proposed to carry oxidized lipids for excretion, it was also suggested that HDL could go “bad,” or become pro-inflammatory if it was overloaded with oxidized products or if the particles were not removed by catabolism.
SAA: a link between cholesterol efflux capacity and inflammation?Serum amyloid A (SAA) concentration in plasma increases markedly following inflammation or infection, with the liver being the principal site of its synthesis. SAA was first reported to be associated with both human and animal HDLs in the late 1970s (1), but is also associated with other lipoprotein fractions (2, 3). Further studies showed that HDL particles isolated from endotoxin-treated mice contain up to two SAAs per apoA-I molecule (4). When SAA containing HDL was reinjected into mice it was cleared from the plasma more rapidly than apoA-I (5–8).