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Increased uptake of non-pathogenic E. coli via the follicle-associated epithelium in longstanding ileal Crohn's disease
Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine.
Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Surgery .
Department of Clinical and Experimental Medicine Linköping University.
Intestinal Disease Research Program McMaster University, Hamilton, Canada.
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2008 (English)In: Journal of Pathology, ISSN 0022-3417, Vol. 215, no 2, 135-144 p.Article in journal (Refereed) Published
Abstract [en]

In Crohn's disease (CD), inflammation is driven by luminal commensal micro-organisms, however, mechanisms of early phases of inflammation need further clarification. The earliest observable lesions of recurrent CD are microscopic erosions at the specialized follicle-associated epithelium (FAE), which lines the Peyer's patches. Therefore, our aim was to investigate the mucosal barrier to non-pathogenic bacteria in FAE of CD. The FAE of macroscopically normal ileum from patients with longstanding CD, ulcerative colitis, and controls was studied in Ussing chambers regarding electrophysiology and permeability to 51Cr-EDTA, horseradish peroxidase, and non-pathogenic E. coli strains. Transepithelial passage routes and uptake into dendritic cells were studied by confocal and electron microscopy. FAE of CD showed increased numbers of adherent bacteria, after E. coli exposure in Ussing chambers, as well as spontaneously in non-exposed archival surgical tissues. Further, we found increased uptake of fluorescent E. coli K-12 and HB101 across FAE of CD, but not in ulcerative colitis. Microscopy demonstrated intercellular and transcellular uptake of E. coli in CD, but only transcellular in controls. FAE exposed to E. coli demonstrated changes in conductance and 51Cr-EDTA permeability, suggesting that bacteria affected the paracellular pathway in CD mucosa. Following bacterial uptake, CD mucosa also demonstrated an increased percentage of E. coli co-localizing with dendritic cells, and augmented tissue release of TNF-α. Our data present novel insights into the pathophysiology of CD by demonstrating a previously unrecognized defect of FAE barrier to bacteria in ileal CD, leading to increased load of commensal bacteria to the inductive sites of mucosal immunity. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Place, publisher, year, edition, pages
2008. Vol. 215, no 2, 135-144 p.
Keyword [en]
Adult Aged Bacterial Adhesion *Bacterial Translocation Case-Control Studies Colitis, Ulcerative/immunology/microbiology Crohn Disease/genetics/immunology/*microbiology Dendritic Cells/microbiology Escherichia coli/*physiology Female Humans *Ileum Immunoen
National Category
Medical and Health Sciences
URN: urn:nbn:se:liu:diva-43367DOI: 10.1002/path.2337Local ID: 73653OAI: diva2:264226
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2009-12-11Bibliographically approved
In thesis
1. Mucosal dendritic cells in inflammatory bowel disease
Open this publication in new window or tab >>Mucosal dendritic cells in inflammatory bowel disease
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Crohn's disease, a chronic inflammation of the bowel, is a multi-factorial condition where uncontrolled immune responses to luminal bacteria occur in genetically predisposed individuals. The first observable clinical signs are small ulcers that form at a specialised form of epithelium, follicle-associated epithelium (FAB). The FAB covers immune inductive sites, Peyer's patches, which function primarily as sensory areas that sample the externaI gut environment. Dendritic cells are one of the key cells that are involved in sensing luminal contents and orchestrating the gut immune system.

The main aim of this thesis was to determine whether the barrier of the FAB is breached in Crohn's disease and if dysfunctional immune regulators, namely dendritic cells, playaroIe in initiating and/or maintaining the chronic intestinal inflammation.

Using biopsies and surgical specimens, we were able to show that in Crohn's disease, there was an increased transmucosaI transport of Escherichia coli compared to specimens from ulcerative colitis and non-inflammatory bowel disease (IBD) controIs. Dendritic cells internalised a higher percentage of bacteria that had translocated across the FAB in the Crohn's samples. Furthermore, significantly higher concentrations of TNF-u was released upon bacterial stimulation by tissues from patients with Crohn's disease than in controIs.

We went on to characterise the dendritic cells present in the Peyer's patches of patients with Crohn's disease. We found an accumulation of both immature and mature dendritic cells beneath the FAB, in the sub-epithelial dome (SED). Normally, mature dendritic cells migrate towards T cell-rich areas. However, we observed mature dendritic cells accumulating in the SED because they lacked the CCR7 migratory receptor. Furthermore, they were more prone to take-up bacteria, and produced TNF.

To study the function of mucosal dendritic cells, we performed isolation experiments and mixed Iymphocyte reactions. Dendritic cells from both the ileum and blood of patients with active Crohn's had reduced capacity for inducing T cell proliferation than non-IBD controIs. Blood dendritic cells of patients in remission had normalised function that was similar to dendritic cells from healthy controls.

The SAMPl/YitFc mice, considered an appropriate murine model for Crohn's disease, had an inherent permeability defect that increased with the chronicity of intestinaI inflammation. However unlike in human Crohn's disease, dendritic cells did not seem to playaroIe in murine ileitis.

This thesis highlights the accumulation of the actively surveying dendritic cells that are prone to bacterial internalisation, and points to their possible different functional roles in active versus in-active disease; thereby confirming dendritic cells as one ofthe key components in the pathogenesis ofCrohn's disease.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2009. 72 p.
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1129
Blood, Crohn's disease, dendritic cells, E. coli, FACS, follicle-associated, epithelium, human, ileum, mixed lymphocyte reaction, permeability, Peyer's patches, SAMP1/YitFc, Ussing chambers, villous epithelium
National Category
Medical and Health Sciences
urn:nbn:se:liu:diva-52234 (URN)978-91-7393-625-5 (ISBN)
Public defence
2009-05-19, Berzeliussalen, Hälsouniversitetet, Campus Valla, Linköpings universitet, Linköping, 13:00 (English)
Available from: 2009-12-11 Created: 2009-12-11 Last updated: 2009-12-11Bibliographically approved

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Keita, ÅsaSalim, Sa´adSöderkvist, PeterMagnusson, Karl-EricSöderholm, Johan D
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