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Infection and Immunity, November 1998, p. 5372-5378, Vol. 66, No. 11
Department of Microbiology,
Received 30 December 1997/Returned for modification 10 March
1998/Accepted 20 August 1998
It is thought that lipopolysaccharide (LPS) from gram-negative
bacteria contributes significantly to the pathogenesis of septic shock.
In vitro studies to address the mechanisms involved in this process
have often investigated human monocytes or mouse macrophages, since
these cells produce many of the mediators found in septic patients.
Targeting of these mediators, especially tumor necrosis factor alpha
(TNF-
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Mechanisms Involved in the Pathogenesis of Sepsis
Are Not Necessarily Reflected by In Vitro Cell Activation
Studies

), has been pursued as a means of reducing mortality in sepsis.
Two experimental approaches were designed to test the assumption that
in vitro studies with macrophages accurately predict in vivo mechanisms
of LPS pathogenesis. In the first approach, advantage was taken of the
fact that on consecutive days after injection of thioglycolate into
mice, increased numbers of macrophages could be harvested from the
peritoneum. These cells manifested markedly enhanced levels of in vitro
TNF-
, interleukin 6 (IL-6), and nitric oxide production in response
to LPS. In D-galactosamine-sensitized mice, however,
thioglycolate treatment significantly decreased mortality due to LPS,
as well as levels of circulating TNF-
and IL-6. Anti-TNF-
treatment confirmed this cytokine's role in the observed lethality. In
a second experimental approach, we compared the mouse
macrophage-stimulating potencies of different LPS preparations with
their lethalities to mice. In these studies, the in vitro macrophage-stimulating profiles presented by rough-LPS and smooth-LPS preparations were the reverse of their relative lethal potencies in
vivo. In conclusion, peritoneal macrophages appear not to be the major
cells responsible for the overall host response during endotoxic shock.
These findings underscore the importance of verifying the
correlation of in vivo systems with in vitro systems when attributing
specific functions to a cell type.
*
Corresponding author. Mailing address: Department of
Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, 3901 Rainbow Blvd., 1000 Wahl Hall East, Kansas City,
KS 66160. Phone: (913) 588-1380. Fax: (913) 588-1388. E-mail: dmorriso{at}kumc.edu.
Present address: Immunology and Respiratory Medicine, National
Jewish Center, Denver, CO 80206.
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