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Infect. Immun., 03 1995, 840-846, Vol 63, No. 3
DM Delahooke, GR Barclay and IR Poxton
The stimulation of macrophages and monocytes by lipopolysaccharide (LPS)
results in the secretion of tumor necrosis factor (TNF), a cytokine which
is thought to play a pivotal role in subsequent host responses. Its
induction is thought to be facilitated by the binding of complexes of LPS
and LPS-binding protein to CD14. The LPS of Bacteroides species was
considered a weak endotoxin; however, in a recent study we have shown that
the biological activity and chemical composition of the LPS from
Bacteroides species are dependent on the extraction method. The present
study determines the capacity of LPS extracted by aqueous phenol (the
method for producing an LPS of high endotoxic activity) from four species
of Bacteroides to induce TNF. Induction was investigated from human
mononuclear leukocytes (MNL), THP- 1 cells (with and without enhancement by
vitamin D2 for CD14), and peritoneal macrophages from C3H/HeJ (LPS
nonresponder) and C3H/HeN (LPS responder) mice. Escherichia coli O18K- LPS,
a typical smooth LPS of heterogeneous molecular mass, was used as a control
throughout. The stimulation of TNF production by E. coli LPS was between
two- and fourfold more than that by Bacteroides LPS in MNL, in THP-1 cells
(with enhancement for CD14), and in peritoneal macrophages from C3H/HeN
mice. In THP-1 cells (without enhancement for CD14), there was no
significant difference in TNF production between E. coli and Bacteroides
LPSs. In peritoneal macrophages from C3H/HeJ mice, E. coli LPS stimulated
no TNF production, but there was no significant difference in TNF
production from peritoneal macrophages from C3H/HeJ and C3H/HeN mice by
Bacteroides LPS. In all cell populations, there was a peak of TNF
production after approximately 4 h of stimulation with all LPSs tested.
However, other peaks of TNF production were seen in MNL and THP-1 cells
(with enhancement for CD14) after stimulation with E. coli LPS only. In
stimulation assays in which Bacteroides LPS was together with but in excess
of E. coli LPS, it was found that TNF production from MNL and THP-1 cells
(with and without enhancement for CD14) was comparable to that of
Bacteroides LPS alone and not E. coli LPS alone. An anti-CD14 monoclonal
antibody did not inhibit Bacteroides LPS-stimulated TNF production.
However, E. coli LPS-stimulated TNF release was inhibited by an anti-CD14
monoclonal antibody, most noticeably in MNL and THP-1 cells (with
enhancement for CD14).(ABSTRACT TRUNCATED AT 400 WORDS)
Copyright © 1995, American Society for Microbiology
Tumor necrosis factor induction by an aqueous phenol-extracted lipopolysaccharide complex from Bacteroides species
Department of Medical Microbiology, University of Edinburgh Medical School, Scotland.
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