Platelet-activating factor
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A platelet-activating factor, also known as a PAF or paf-acether is a potent phospholipid activator and mediator of many leucocyte functions, including platelet aggregation, inflammation, and anaphylaxis.
It is produced in response to specific stimuli by a variety of cell types, including neutrophils, basophils, platelets, and endothelial cells. Several molecular species of platelet-activating factor have been identified which vary in the length of the O-alkyl side chain. It is an important mediator of bronchoconstriction.
Its alkyl group is connected by an ether linkage at the C1 carbon to a sixteen carbon chain. The acyl group at the C2 carbon is an acetate unit whose short length increases the solubility of PAF, allowing it to function as a soluble signal messenger.
It causes platelets to aggregate and blood vessels to dilate. At a concentration of 10^-12 M, PAF causes life threatening inflammation of the airways to induce asthma like symptoms. Toxins such as fragments of destroyed bacteria induce the synthesis of PAF, which causes a drop in blood pressure and reduced volume of blood pumped by the heart, which leads to shock and maybe death.
It was discovered by French immunologist Jacques Benveniste in 1970.
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