Infection with the gastric bacterium Helicobacter pylori provides reliable protection against allergy-induced asthma, according to immunologists from the University of Zurich.
The results confirmed the hypothesis recently put forward that the dramatic increase in allergic diseases in industrial societies is linked to the rapid disappearance of specific micro-organisms that populate the human body.
Scientists from the University of Zurich and the University Medical Center of the Johannes Gutenberg University Mainz have now revealed that the increase in asthma could be put down to the specific disappearance of the gastric bacterium Helicobacter pylori (H. pylori) from Western societies.
H. pylori is resistant to gastric acid. The affliction often has no symptoms, but under certain conditions can cause gastritis, gastric and duodenal ulcers, and stomach cancer. Consequently, H. pylori is often killed off with antibiotics as a precaution, even if the patient does not have any complaints.
For their study, the researchers infected mice with H. pylori bacteria. If the mice were infected at the age of a few days old, they developed immunological tolerance to the bacterium and even reacted insignificantly - if at all - to strong, asthma-inducing allergens. Mice that were not infected with H. pylori until they had reached adulthood, however, had a much weaker defence.
"Early infection impairs the maturation of the dendritic cells and triggers the accumulation of regulatory T-cells that are crucial for the suppression of asthma," said Anne Muller, a professor of molecular cancer research at the University of Zurich, explaining the protective mechanism.
If regulatory T-cells were transferred from infected to uninfected mice, they too enjoyed effective protection against allergy-induced asthma. However, mice that had been infected early also lost their resistance to asthma-inducing allergens if H. pylori were killed off in them with the aid of antibiotics after the sensitisation phase.
The study has been published in the prestigious Journal of Clinical Investigation.