Oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (OxPAPC) is a prototypic biologically active oxidized phospholipid first isolated from LDL minimally modified by oxidation (MM-LDL). OxPAPC is an active principle of MM-LDL that mimics several pro- and anti-inflammatory effects induced by oxidized lipoproteins. Oxidation of PAPC generates a mixture of oxidized phospholipids containing either fragmented or full- length oxygenated sn-2 residues. The best-characterized oxidatively fragmented species contain a five- carbon sn-2 residue bearing omega-aldehyde or omega-carboxyl groups. Oxydation of arachidonic acid residue also produces phospholipids containing esterified isoprostanes. Both fragmented and full-length oxygenated species can regulate immune reactions. Pro-inflammatory effects of OxPAPC include stimulation of endothelial cells to bind monocytes and induction of tissue clotting factor, IL-8, MCP-1, G-CSF and other mediators of atherothrombosis. Anti- inflammatory effects of OxPAPC are mediated by induction of protective enzymes such as heme oxygenase-1 as well as suppression of innate immune responses to bacterial lipopolysaccharide (LPS) due to inhibition of LPS recognition by LPS-binding protein (LBP) and CD14. OxPAPC is active in vivo and was shown to protect mice in several models of acute inflammation induced by bacterial products. In addition, oxidized phospholipids present in OxPAPC are recognised by scavenger receptor CD36 and auto-antibodies present in patients with anti-phospholipid syndrome.