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First published online 19 April 2005
doi: 10.1242/jcs.02316
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Research Article |
1 Department of Medicine, Palo Alto VA Medical Center, 3801 Miranda Avenue, 154J, Palo Alto, CA 94304, USA
2 Department of Pathology, Palo Alto VA Medical Center, 3801 Miranda Avenue, 154J, Palo Alto, CA 94304, USA
3 Stanford University School of Medicine Digestive Disease Center, Stanford, CA 94305, USA
* Author for correspondence (e-mail: mbishr{at}stanford.edu)
Accepted 10 February 2005
Keratin 8 (K8) is the major intermediate filament protein present in intestinal epithelia. Depending on the mouse genetic background, absence of K8 causes embryonic lethality or colonic hyperplasia and colitis. We studied disease progression, the inflammatory responses, and role of luminal bacteria in K8-null mice in order to characterize the intestinal pathology of K8-associated colitis. Colon lymphocytes were isolated for analysis of their phenotype and cytokine production, and vascular and lymphocyte adhesion molecule expression in K8/ mice of varying ages. K8/ mice had a marked increase in TCRß-positive/CD4-positive T cells infiltrating the colon lamina propria, in association with enhanced Th2 cytokine (IL-4, IL-5 and IL-13) production. K8/ mice show early signs of inflammation even prior to weaning, that increases with age, and their epithelial cells overexpress MHC class II antigens. The chronic colitis is related to increased CD4-positive infiltrating T cells displaying memory and naive phenotypes, and an altered vascular endothelium with aberrant expression of peripheral node addressin. Analysis of normal gut-specific homing molecules, reveals an increased number of
4ß7-positive cells and vascular mucosal addressin cell adhesion molecule-1 in K8-null colons. Antibiotic treatment markedly decreased colon inflammation and ion transporter AE1/2 mistargeting, indicating that luminal bacteria play an important role in the observed phenotype. Therefore, K8-null mice develop chronic spontaneous Th2-type colitis due to a primary epithelial rather than immune cell defect, which is amenable to antibiotic therapy. These mice provide a model to investigate epithelial-leukocyte and epithelial-microbial cross-talk.
Key words: Colitis, inflammatory bowel disease, intermediate filaments, Th2 cytokine
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