Mechanisms of bacterial-epithelial interaction in Crohn’s disease

Sammanfattning: Crohn’s disease (CD) is believed to be initiated when an individual, who has agenetic predisposition either leading to a disturbance in the barrier functionand/or the innate immune system is exposed to triggering environmentalfactors, the most important being intraluminal bacteria. Genetic and functionalstudies have confirmed the Pattern-recognition receptors (PRRs), Nod2, TLR4and NALP3, as important mediators of the inflammatory process associatedwith disease progression. However, the mechanisms that link enteric bacteriaand barrier function in a background of genetic predisposition to CD are justbeginning to emerge. The general aim of this thesis was therefore to morethoroughly investigate the mechanisms of bacterial-epithelial interaction in CD.Here we present evidence suggesting that the small bowel is able to inducetranscytosis of antigens after short term exposure to Yersinia pseudotuberculosis. This suggests that small bowel enterocytes are able toattain follicle associated epithelial (FAE) abilities and contribute to the barrierdysfunction observed in CD. Furthermore we report a positive effect of anti-TNF? treatment (infliximab) on the translocation of adherent invasive E.coli (AIEC) across the colonic mucosa of patients suffering from severe CD.We also confirm the importance of the Nod-like receptors (NLRs) in thepathogenesis of CD by showing that combined polymorphisms in the genesencoding NALP3 and CARD8 confer susceptibility to CD among Swedish menand in addition to previous published results add a gender aspect on thegenotype-phenotype relationship in CD. Finally, we show that Nod2 is rapidlysubjected to ubiquitination followed by proteasomal degradation, henceproviding important clues about how NLR regulation might occur in the cell,suggesting that the ubiquitin-proteasome pathway is an important factor toconsider in the development of the disease.In conclusion we report novel insights into the bacterial-epithelial interactionsoccurring in CD and contribute important clues about the origin of this disease.ISBN: 978-