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Infection and Immunity, November 1998, p. 5462-5469, Vol. 66, No. 11
Divisions of
Gastroenterology1 and
Immunology3 and
Institute of
Infections and Immunity,2 University
Hospital, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom
Received 17 February 1998/Returned for modification 23 April
1998/Accepted 20 August 1998
We have previously shown that Clostridium difficile
toxin A induces detachment of human colonic epithelial cells from the basement membrane and subsequent cell death by apoptosis.
Because these cells require adhesion-dependent signalling from the
extracellular matrix for survival, their detachment from the basement
membrane by other means also induces apoptosis. The role of
toxin A in the induction of apoptosis therefore remains to be
determined. In addition, sensitivities to C. difficile
toxin A of lamina propria lymphocytes, macrophages, and eosinophils,
which lie below the surface epithelium, are not known. In contrast to
epithelial cells, these lamina propria cells do not require
adhesion-dependent signalling from the extracellular matrix for
survival, and this may allow the mechanisms of toxin A-induced cell
death to be further investigated. The aim of this study was to
investigate the effect of purified C. difficile toxin
A on human colonic lamina propria T cells, macrophages, and
eosinophils. We show that C. difficile toxin A induces
loss of viability in isolated colonic lamina propria cell preparations
containing the three different cell types in a dose- and time-dependent
fashion. Exposure to high concentrations of the toxin led to loss of
macrophages within 72 h. T-lymphocyte and eosinophil cell death
was prominent at later time points and occurred by apoptosis.
Exposure to toxin A also induced the production of tumor necrosis
factor alpha by the isolated colonic lamina propria cells. However, the
presence of neutralizing antibodies to this cytokine did not influence
C. difficile toxin A-induced T-cell apoptosis.
Moreover, purified T cells also underwent apoptosis following
exposure to toxin A, implying that apoptosis occurred as a
consequence of a direct interaction between T cells and the toxin. Our
studies suggest that C. difficile toxin A is capable of suppressing human colonic mucosal immune responses by inducing early
loss of macrophages followed by T-cell apoptosis.
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Effect of Clostridium difficile Toxin A on Human
Colonic Lamina Propria Cells: Early Loss of Macrophages Followed
by T-Cell Apoptosis
*
Corresponding author. Mailing address: Division of
Gastroenterology, University Hospital, Queen's Medical Centre,
Nottingham NG7 2UH, United Kingdom. Phone: 44-115-970 9918. Fax:
44-115-942 2232. E-mail:
muzyrm{at}mmn1.medical.nottingham.ac.uk.
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