Stomach bacteria switch off human immune defenses to cause disease

Sep. 2, 2013 — Helicobacter pylori is a bacterium that establishes a life-long stomach infection in humans, which in some cases can lead to duodenal ulcers or stomach cancer. New research, presented at this week’s Society for General Microbiology Autumn Conference, gives us a clearer understanding of how these bacteria can manipulate the human immune system to survive in the mucosal lining of the stomach.Share This:Researchers from the University of Nottingham have shown that H. pylori is able to supress the body’s normal production of ‘human beta defensin 1’ (hβD1), an antimicrobial factor present in the stomach lining that helps prevent bacterial infection. By collecting stomach tissue biopsies from 54 patients at the Queens Medical Centre, Nottingham, the team showed that patients infected with H. pylori had ten times less hβD1 than uninfected patients. Those with the lowest amount of hβD1 had the most bacteria present in their stomach lining.The most damaging strains of H. pylori make a molecular syringe called the cagT4SS, through which bacterial products are injected into cells of the stomach lining. In vitro work using human gastric epithelial cell lines showed that this activates chemical pathways to suppress hβD1 production. These activated pathways are also involved in the stimulation of an inflammatory response, meaning that these H. …

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