Platelet-activating factor is a potent phospholipid activator and mediator of many leukocyte 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.It causes platelets to aggregate and blood vessels to dilate. Thus it is important to the process of hemostasis. 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.