Lipid mediator metabolism initiated by sPLA2. The major phospholipid of the outer leaflet of the plasma membrane is PC. Cleavage of PC by sPLA2 thus results in the release of a free fatty acid, such as AA and lyso-PC, which has recently been shown to activate DCs. AA can be metabolized by COX and the respective synthase toward PGE2, which cooperates with TNF-α in DC maturation.