To better understand how PGE2 contributes to late inflammatory processes, we induced a self-limiting peritonitis in C57/BL6 mice by intraperitoneal (i.p.)injection of zymosan (5 mg/kg), and inhibited PGE2 synthesis by daily i.p. injections of the selective mPGES-1 inhibitor CIII (25 mg/kg)26 once the inflammatory response was established for 24 h (Fig. 1A). This evidence concerns the gene PTGES and peritonitis.