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Immune mechanisms of the farm effect identified
Numerous studies have already linked excessive hygiene in everyday life to health disadvantages, with a particular focus on the increased risk of autoimmune diseases and allergies. In return, advantages of living in agricultural environments were found here, which are attributed to the increased contact with microbial life forms. Scientists at the University Hospital of Geneva have now examined the underlying immune mechanisms in more detail in a current study.
Growing up on the farm offers long-lasting protection against allergies, whereby life in the microbial environment of farm animals is crucial to induce this protective effect, explains the research team led by Philippe Eigenmann from the University Hospital Geneva. Which immune mechanisms are responsible for this remains so far unclear. The researchers have now tried to find this out using a mouse model and published their results in the journal "Clinical & Experimental Allergy".
Hygiene as the cause of illnesses?
Thorough hygiene can minimize the transmission of infectious diseases, but the lack of utilization of the immune system also leads to an increased risk of autoimmune diseases and allergies, according to the core statement of the so-called hygiene hypothesis. Hay fever, asthma, neurodermatitis and numerous other diseases are therefore to be seen in connection with excessive hygiene. However, living in an agricultural environment has a protective effect here, as confirmed in the current study.
Colonies of mice studied on the farm and in the laboratory
The scientists used a mouse model to study the effects of the microbial environment in agricultural life and the immunological changes associated with protection against allergies. A colony of mice was bred on a farm with a cowshed and a colony in the laboratory at the Geneva University Hospital. The researchers exposed mice from both sites to a contact allergen and observed the reaction. The blood cells and cell cytokine production in both populations were also assessed, Eigenmann and colleagues report. In addition, the gut microbiome was characterized at different ages.
Reduced susceptibility to allergies
According to the researchers, the mice that were born on the farm were less prone to allergies than mice that were bred in the laboratory. Moving mice from the laboratory to the farm also had a positive effect on the susceptibility to allergies. Overall, the farm mice showed an earlier "immune activation with a higher CD4 + T cell population, in particular CD4 + CD25 + FoxP3- (activated cells)" compared to the laboratory mice, write the Geneva researchers. The cytokine profile of mice on the farm is much different. The differences are most pronounced within a certain age window between birth and eight weeks of age. The microbiome analysis also showed considerable differences in the mice from the land and from the laboratory.
"The agricultural environment requires a strong, allergy-protecting IL-22 stimulus and generates activated CD4 + T cells," the scientists report of their analysis of the immune mechanisms. Exposure to the agricultural environment also resulted in better protection against contact allergies. The extent to which viral causes have an impact needs to be clarified in further studies. (fp)