Our trauma research center program entitled, "Trauma Primes Cells" is based on the fundamental hypothesis that prior exposure to multiple, sequential, sublethal cellular insults primes constructive or destructive pathways of cellular responses of subsequent injury. A major objective is to design therapy that will reduce the incidence of multiple organ failure. Although a number of inflammatory cascades have been incriminated in the pathogenesis of multiple organ failure (MOF), diffuse PMN-mediated tissue injury remains an attractive unifying concept. We have developed a sequential insult rodent model in which the priming event consisted of superior mesenteric arterial (SMA) clamping for 45 minutes followed by 6 hours of reperfusion. Following this priming event, activation was induced with a low dose of endotoxin (2.5 mg/kg). We believe that these studies support our hypothesis: mesenteric ischemic/reperfusion primes circulating PMNs. When these have been activated they can then be provoked by endotoxin to provoke distant organ injury. Primed PMNs are released from the postischemic mesenteric bed and enter the systemic circulation. They subsequently sequester in the pulmonary vascular bed where they are relatively harmless until they are activated by low dose endotoxin. These activated PMNs then migrate across the endothelium cell and release reactive oxygen metabolites.