Endotoxin tolerance: A review : Critical Care Medicine (original) (raw)
SCIENTIFIC REVIEWS
From Northwestern University, Department of Surgery, Chicago, IL.
Although endotoxin tolerance was initially thought to be a beneficial adaptive response, it may be a component or marker of the immune dysregulation that complicates management of patients with severe sepsis and organ dysfunction.
Address requests for reprints to: Michael A. West, MD, PhD, Northwestern University, Department of Surgery, 201 E. Huron, Galter 10-105, Chicago, IL 60611. E-mail: [email protected]
Abstract
Endotoxin tolerance was initially described when it was observed that animals survived a lethal dose of bacterial endotoxin if they had been previously treated with a sublethal injection. In animal models, two phases of endotoxin tolerance are described, an early phase associated with altered cellular activation and a late phase associated with the development of specific antibodies against the polysaccharide side chain of Gram-negative organisms. Recently, there has been a tremendous resurgence of interest in the mechanisms responsible for altered responsiveness to bacterial endotoxin. Host immune cells, particularly macrophages and monocytes, that are exposed to endotoxin for 3 to 24 hrs are rendered “tolerant” and manifest a profoundly altered response when rechallenged with bacterial endotoxin or lipopolysaccharide. The “lipopolysaccharide-tolerant” phenotype is characterized by inhibition of lipopolysaccharide-stimulated tumor necrosis factor production, altered interleukin-1 and interleukin-6 release, enhanced cyclooxygenase-2 activation, inhibition of mitogen-activated protein kinase activation, and impaired nuclear factor-κB translocation. Human monocytes and macrophages can be induced to become tolerant, and there is increasing evidence that monocytic cells from patients with systemic inflammatory response syndrome and sepsis have many characteristics of endotoxin tolerance.
© 2002 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins