2023-09-29 18:00:00
In experiments with mice, germ-free animals did not show any stronger allergic reactions than their microbe-accustomed counterparts.
Excessive hygiene in rich industrialized nations may not be a significant cause of allergies, explains a team of researchers with Austrian participation. In experiments with mice, animals kept germ-free did not show more allergic reactions (e.g. to house dust mites) than mice that were exposed to a wide variety of microbes from birth. The study was published 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 states that early contact with different germs in childhood reduces the risk of later allergic diseases. It is believed that this makes the immune system more tolerant and less likely to overreact when it encounters house dust mite droppings and mugwort pollen, for example. Susanne Vrtala and Huey-Jy Huang from the Institute of 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” react to allergy triggers. The wildling mice are genetically identical to conventional laboratory mice, but were transplanted as embryos into “wild” mouse mothers, carried to term and born by them. As a result, they had contact with a variety of microbes from an early age.
The wildlings’ immune systems reacted similarly strongly to the tests as in the “pure” laboratory mice. When they were exposed to allergens, the wildlings also showed “robust signs of pathogenic inflammatory reactions and allergic immune responses,” according to the specialist publication. 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 triggers them,” Coquet told Science Immunology. This may be possible in special cases, but probably not a general rule. “Our study shows that general and widespread exposure to microbes may not have the clearly positive effects that we would like,” said Nylen.
According to researchers not involved in the study, the test results cannot completely invalidate the hygiene hypothesis. “In immunological studies, it must always be clearly emphasized that the immune response is different in mice and humans,” explained Eva Untersmayr-Elsenhuber, who also works at the Institute for Pathophysiology and Allergy Research at Meduni Vienna, 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.
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