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Mucosal dendritic cells in inflammatory bowel disease
Linköping University, Department of Clinical and Experimental Medicine, Surgery . Linköping University, Faculty of Health Sciences.
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.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1129
Keyword [en]
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
Identifiers
URN: urn:nbn:se:liu:diva-52234ISBN: 978-91-7393-625-5 (print)OAI: oai:DiVA.org:liu-52234DiVA: diva2:280722
Public defence
2009-05-19, Berzeliussalen, Hälsouniversitetet, Campus Valla, Linköpings universitet, Linköping, 13:00 (English)
Opponent
Supervisors
Available from: 2009-12-11 Created: 2009-12-11 Last updated: 2009-12-11Bibliographically approved
List of papers
1. Increased uptake of non-pathogenic E. coli via the follicle-associated epithelium in longstanding ileal Crohn's disease
Open this publication in new window or tab >>Increased uptake of non-pathogenic E. coli via the follicle-associated epithelium in longstanding ileal Crohn's disease
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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.

Keyword
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
Identifiers
urn:nbn:se:liu:diva-43367 (URN)10.1002/path.2337 (DOI)73653 (Local ID)73653 (Archive number)73653 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2009-12-11Bibliographically approved
2. CD83(+)CCR7(-) Dendritic Cells Accumulate in the Subepithelial Dome and Internalize Translocated Escherichia coli HB101 in the Peyers Patches of Heal Crohns Disease
Open this publication in new window or tab >>CD83(+)CCR7(-) Dendritic Cells Accumulate in the Subepithelial Dome and Internalize Translocated Escherichia coli HB101 in the Peyers Patches of Heal Crohns Disease
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2009 (English)In: American Journal of Pathology, ISSN 0002-9440, Vol. 174, no 1, 82-90 p.Article in journal (Refereed) Published
Abstract [en]

Recurrent Crohns disease originates with small erosions in the follicle-associated epithelium overlying the Peyers patches. Animal studies have illustrated mucosal immune regulation by dendritic cells located in the subepithelial dome. The aim of this study was to characterize the dendritic cells at this specific site in patients with Crohns disease. Heal tissues were obtained after surgery performed on Crohns patients; ileal samples from noninflammatory bowel disease and ulcerative colitis served as standard and inflammatory controls, respectively. Flow cytometry of isolated intestinal mononuclear cells showed a larger subset of dendritic cells in Crohns samples compared with controls. This finding was corroborated by confocal microscopy, showing enhanced infiltrates of cells positive for the dendritic cell markers, DC-SIGN(+) and CD83(+), in the subepithelial dome. Moreover, the CD83(+) cells in Crohns tissues showed reduced expression of the lymph node migratory receptor, CCR7, possibly contributing to the high numbers of dendritic cells. After exposure to nonpathogenic Escherichia coli in Ussing chambers, dendritic cells in the subepithelial dome of Crohns disease demonstrated increased co-localization with translocated bacteria. Immunohistochemical results revealed that DC-SIGN(+) cells in Crohns tissues were found to express toll-like receptor 4 and produce tumor necrosis factor-a. In conclusion, nonmigrating dendritic cells that accumulate in the subepithelial dome and internalize nonpathogenic bacteria may be important for the onset and perpetuation of mucosal inflammation in Crohns disease.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-16424 (URN)10.2353/ajpath.2009.080273 (DOI)
Available from: 2009-01-23 Created: 2009-01-23 Last updated: 2009-12-11Bibliographically approved
3. T-cell expansion capacity of Dendritic cells isolated from patients wiht Chron's disease
Open this publication in new window or tab >>T-cell expansion capacity of Dendritic cells isolated from patients wiht Chron's disease
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Aphtoid lesions at the follicle-associated epithelium (FAE) are one of the earliest observable signs of recurrent ileal Crohn’s disease (CD). In an earlier study, we found an abnormal accumulation of dendritic cells (DCs) situated beneath the FAE, in the sub-epithelial dome (SED) of patients with CD. These DCs were prone to E.coli uptake. The aim here was to isolate and characterise DCs from patients with CD and determine their functional properties in T-cell expansion. Initially, DCs were isolated from eleal mucosa and blood of 5 CD patients and 5 patients with non-IBD disorders, via magnetic bead separation. DCs were also isolated from blood of 5 patients in long-term remission and 5 healthy volunteers, via FACS sorting and separation. Mixed lymphocyte reaction was performed on the isolated DCs and expansion of T-cells was recorded. DCs that were isolated from blood were also characterised via FACS analysis. DCs from patients with active CD had the tendency of having lower T-cell expansion capacity than DCs from non-IBD controls. The capacity to stimulate T-cells proliferation was restored to similar levels as healthy controls in DCs isolated from patients in remission. However, there was more than 10-fold increase in myeloid (CD11c+) DCs present in the peripheral blood mononuclear cells of CD than in healthy controls. The myeloid DCs were primarily immature (CD83-) and expressed the lymph node migratory receptor CCR7. This population of DCs may be responsible for inducing a tolerogenic or regulatory effect. Our results hint to a complex immune-regulatory mechanism where DCs at different stages of chronic inflammation exert different immune-modulatory effects.

Keyword
Blood, E.coli LF82, FACS, IBD, ileum, mixed lymphhocyte reaction
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-52228 (URN)
Available from: 2009-12-11 Created: 2009-12-11 Last updated: 2009-12-11Bibliographically approved
4. Barrier defect in the follicle-associated epithelium of SAMP1/YitFc mice demonstrates vulnerability to adherent-invasive Escherichia coli LF82
Open this publication in new window or tab >>Barrier defect in the follicle-associated epithelium of SAMP1/YitFc mice demonstrates vulnerability to adherent-invasive Escherichia coli LF82
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

SAMP1/YitFc mice are a unique murine model for Crohn’s disease (CD) as they develop spontaneous intestinal inflammation without chemical or genetic manipulations. Inflammation is primarily located in the distal ileum, which is the hallmark location for CD. It is at the distal ileum of CD where small erosions that develop at the follicle-associated epithelium (FAE) and are one of the earliest observable lesions in recurrent ileitis. In the report, we studied the intestinal permeability defect and examined the role of dendritic cells (DCs) in the SAMP1/YitFc mice ileitis. Segments of FAE and VE from 11 and 27 weeks old SAMP1/YitFc mice and AKR control background stains were mounted on Ussing chambers. Electrical conductivity and permeability to 51Cr-EDTA, horseradish peroxidise (HRP) and E.coli HB101 and LF82 were recorded. There was ileal permeability to 51Cr-EDTA and HRP in the 27 weeks old SAMP1/YitFc mice. Both E.coli HB101 and LF82 increased conductance by two-folds in FAE and VE of SAMP1/YitFc mice. Furthermore, both bacterial strains increased tissue conductance and 51Cr-EDTA passage. There was greater passage of E.coli LF82 in the 27 week old DAMP1/YitFc mice than in controls. Confocal microscopy revealed a high number of CD11c+ DCs in the sub-epithelial dome (SED) area, though there was no difference between the SAMP1/YitFc mice than the AKR controls. Immunofluorescence characterisation also did not reveal any phenotypic difference in DCs between the mice strains. These results show that SAMP1/YitFc mice have a barrier defect, which was more pronounced in the FAE of older mice, and demonstrate a mucosal sensitivity bacteria. It also confirms that this model of chronic ileitis is primarily a defect in permeability defect and not DCs.

Keyword
52Cr-EDTA, dentric cells, E.coli, HRP, permeability, Ussing chanbers
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-52233 (URN)
Available from: 2009-12-11 Created: 2009-12-11 Last updated: 2009-12-11Bibliographically approved

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Salim, Sa'ad Yislam

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