Their results confirm 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.
The hygiene hypothesis states that modern hygiene measures have led to a lack of exposure to infectious agents, which is important for the normal maturation of the immune system. Scientists from the University of Zurich and the University Medical Center of the Johannes Gutenberg University Mainz now reveal that the increase in asthma could be put down to the specific disappearance of the gastric bacterium Helicobacter pylori from Western societies.
Helicobacter pylori is resistant to gastric acid. According to estimates, around half of the world’s population might be infected with the bacteria. The affliction often has no symptoms, but under certain conditions can cause gastritis, gastric and duodenal ulcers, and stomach cancer. Consequently, Helicobacter 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 Helicobacter 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 Helicobacter pylori until they had reached adulthood, however, had a much weaker defense.
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 Helicobacter pylori was killed off in them with the aid of antibiotics after the sensitization phase.
MEDICA.de; Source: University Medical Center of the Johannes Gutenberg University Mainz