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1Institute for Hygiene and Infectious Diseases of Animals, Justus-Liebig-University, D-35392 Giessen, Germany 2,3Division of Microbiology2 and Division of Immunology & Pathology3, Institute for Animal Health, Compton Laboratory, Compton, Berkshire RG20 7NN, UK
Correspondence Christian Menge christian.menge{at}vetmed.uni-giessen.de
Received November 6, 2003
Accepted January 28, 2004
Ruminants are a major reservoir of enterohaemorrhagic Escherichia coli (EHEC), which cause acute gastroenteritis in humans with potentially life-threatening sequelae. The mechanisms underlying EHEC persistence in ruminant hosts are poorly understood. EHEC produce several cytotoxins that inhibit the proliferation of bovine lymphocytes in vitro and influence EHEC persistence in calves, suggesting that bacterial suppression of mucosal inflammation may be important in vivo. In order to address this hypothesis, intraepithelial lymphocytes (IEL) obtained from ligated intestinal loops of five 914 day old calves were characterized 12 h after inoculation with E. coli strains. Loops were inoculated with an EHEC O103 : H2 strain, an isogenic
stx1 mutant incapable of producing Shiga toxin 1 (Stx1) and a porcine non-pathogenic E. coli strain. The IEL mainly comprised activated CD2+ CD3+ CD6+ CD8
+ T cells and resembled IEL obtained from the intestinal mucosa of orally challenged calves. Forty per cent of all IEL were potentially sensitive to Stx1 in that they expressed the receptor for Stx1. Nevertheless, analysis of IEL from inoculated loops failed to detect a significant effect of the different E. coli strains on proliferative capacity, natural killer cell activity or the cytokine mRNA profile. However, the EHEC wild-type strain reduced the percentage of CD8
+ T cells in the ileal mucosa compared with loops inoculated with the
stx1 mutant. This shift in IEL composition was not associated with inhibition of IEL proliferation in situ, since the majority of the IEL from all loops were in the G0/G1 phase of the cell cycle. These studies indicate that the ligated ileal loop model will be a useful tool to dissect the mechanisms underlying suppression of mucosal inflammation by EHEC in the reservoir host.
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