Affiliation:
1. Divisions of Gastroenterology1 and
2. Institute of Infections and Immunity,2 University Hospital, Queen’s Medical Centre, Nottingham NG7 2UH, United Kingdom
3. Immunology3 and
Abstract
ABSTRACT
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.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Cited by
65 articles.
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