How stomach bacteria switch off human immune defences to cause disease
Washington: Researchers have identified how stomach bacteria can manipulate the human immune system to survive in the mucosal lining of the stomach.
Researchers from the University of Nottingham have shown that Helicobacter pylori- a bacterium that establishes a life-long stomach infection in humans- is able to supress the body`s normal production of `human beta defensin 1` (h beta D1), 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 h beta D1 than uninfected patients. Those with the lowest amount of h beta D1 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 h beta D1 production.
These activated pathways are also involved in the stimulation of an inflammatory response, meaning that these H. pylori strains are able to survive and colonise more abundantly, while continuing to cause tissue damage over many decades. Previous research suggests that chronic inflammation of the stomach lining is strongly linked to gastric cancer.
The study was presented at Society for General Microbiology Autumn Conference.