Pathophysiology and Clinical Relevance of Endotoxin Tolerance in Humans

A number of diseases lead to a so called systemic inflammatory response syndrome (SIRS). This excessive response is self-destructive and leads to major complications of the initial disease: dysfunction of the microcirculation, systemic vasodilation, and increased capillary leakage and oedema. Animal studies have shown that pre-treatment with endotoxin (lipopolysaccharide or LPS) suppress the excessive immune response and when rechallenged, the animal survive a normally lethal dose of endotoxin. Besides a diminished cytokine response, an increased production of leucocytes in the bone marrow and an increased phagocytosis after pre-treatment with endotoxin is seen. The combination of these factors: diminished systemic inflammatory response and increased cellular immunity makes that endotoxin tolerance is a useful tool for preventing the complications after an excessive inflammatory response. Further, the presence of cross-tolerance has also been shown: Endotoxin tolerant mice survive more after induction of a normally lethal fungal infection. Endotoxin tolerance is also protective for ischemia/reperfusion injury in kidneys, heart and liver. Little data is known about endotoxin tolerance in human. The purpose of this study is to induce a state of tolerance through 2 different administration schedules and monitor the effect of tolerance on pro- and anti-inflammatory cytokines, other inflammatory parameters and different proteins involved in the signalling pathway. The effects of tolerance on vascular reactivity will be determined. Finally, the effect of tolerance on ischemia-reperfusion injury will be investigated.