It has long been thought that early contact with various germs has a beneficial effect on the immune system. A new study now makes this clear: experiments with mice showed that animals kept germ-free did not show stronger allergic reactions (for example to house dust mites) than mice exposed to a wide variety of microbes from birth.
Excessive hygiene in rich industrialized countries may not be a significant trigger for allergies, the research team with Austrian participation explains in the journal ‘Science Immunology’. A team led by Jonathan Coquet and Susanne Nylen from the Karolinska Institute in Stockholm (Sweden) tested the so-called ‘hygiene hypothesis’ in mice. It is stated that early contact with various germs in childhood reduces the risk of later allergic diseases.
Early contact important for the immune system?
It is believed that this makes the immune system more tolerant and less likely to overreact when, for example, it comes into contact with dust mite feces and mugwort pollen. Susanne Vrtala and Huey-Jy Huang from the Institute for Pathophysiology and Allergy Research at the Medical University of Vienna were also involved in the study.
The researchers compared how germ-free laboratory mice and ‘wildling mice’ respond to allergic triggers. The wildling mice are genetically identical to conventional laboratory mice, but were transplanted as embryos into ‘wild’ mouse mothers, carried and born by them. As a result, they came into contact with all kinds of microbes at an early age.
Wildlings also reacted strongly to allergens
During the tests, the wildlings’ immune systems responded just as strongly as those of the ‘pure’ laboratory mice. When exposed to allergens, the wildlings also showed “strong signs of pathogenic inflammatory responses and allergic immune responses,” the specialized publication said. Despite being colonized with natural microorganisms, they were not immune to allergic reactions.
“So you can’t just say: a dirty lifestyle stops allergies and cleanliness causes them,” Coquet told Science Immunology. This may be possible in special cases, but this is probably not a general rule. “Our research shows that general and widespread exposure to microbes may not have the clear positive effects we would like,” says Nylen.
Hygiene hypothesis not yet completely debunked
According to researchers not involved in the study, the test results cannot completely disprove the hygiene hypothesis. “In immunological studies it should always be clearly emphasized that the immune response is different in mice and humans,” Eva Untersmayr-Elsenhuber, who also works at the Institute for Pathophysiology and Allergy Research in Meduni Vienna, explained to the German “Science Media Center.” .
Mouse models are relevant to investigate mechanisms, but the data must always be confirmed in patients,” said the doctor.
Source: Krone
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