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| Exploring Allergies in 'Dirty' Mice: Challenging the Hygiene Hypothesis |
The concept of the hygiene hypothesis, which suggests that exposure to microbes may reduce the risk of developing allergies, has gained traction over recent decades. However, a groundbreaking study published in Science Immunology by researchers at the Karolinska Institutet challenges this hypothesis. Their findings indicate that mice exposed to high levels of infectious agents from birth may possess an equal or possibly higher propensity to develop allergic immune responses compared to their "clean" laboratory counterparts.
The idea that microbes could play a role in allergy prevention has been a subject of considerable interest. Previous studies have proposed that certain infections might suppress the production of inflammatory antibodies to allergens and modify the behavior of T cells associated with allergies. It has even been suggested that beneficial gut bacteria might have the ability to dampen inflammation in various parts of the body.
Intriguingly, the researchers conducted a comparative analysis of allergic immune responses in "dirty" wildling mice and their conventional laboratory counterparts. They discovered scant evidence that the antibody response was altered or that T cell functions underwent significant changes. Furthermore, the anti-inflammatory responses triggered by beneficial gut bacteria did not appear to possess the capability to curb allergic immune responses. In fact, when exposed to allergens, the wildling mice exhibited robust indications of pathological inflammation and allergic reactions.
Jonathan Coquet, a co-author of the study and Associate Professor at the Department of Microbiology, Tumor, and Cell Biology at the Karolinska Institutet, emphasized that the results challenged the notion that "dirty" lifestyles prevent allergies while "clean" lifestyles promote them. He acknowledged that specific contexts might support this idea but suggested it wasn't a universal rule.
These wildling mice, although genetically identical to their laboratory counterparts, live under seminatural conditions and experience substantial microbial exposure from birth. Coquet noted that the immune systems of these wildling mice better mimic the human immune system, offering hope that they could bring us closer to understanding how microbes impact the body.
This study not only contributes to our comprehension of the origins of allergies but also carries potential clinical implications. In clinical trials, researchers and clinicians have recently explored the use of experimental infections to treat patients with inflammatory diseases. Methods such as infecting individuals with worms or performing fecal transplantations have been proposed as tools to combat these conditions. Additionally, newborns delivered via C-section have undergone maternal fecal transplantation and bacterial supplementation to promote healthy gut bacteria and future well-being.
Susanne Nylén, another co-author of the study and Associate Professor at the Department of Microbiology, Tumor, and Cell Biology at the Karolinska Institutet, emphasized that while this research field holds promise for leveraging infections and microbes to promote health, it remains in its infancy. This study serves as a reminder that broad exposure to microbes may not consistently yield the anticipated beneficial effects.
The research was led by Junjie Ma and Egon Urgard in Jonathan Coquet's group, in collaboration with Professor Stephan Rosshart at University Medical Center Freiburg in Germany and Susanne Nylén at the Karolinska Institutet. Several other research groups at the Karolinska Institutet and elsewhere also contributed to this work, including the teams of Assistant Professors Itziar Martinez Gonzalez and Juan Du at the Department of Microbiology, Tumor, and Cell Biology.
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