A bacterium that causes the 'farm effect,' where children raised in rural areas or on farms are less likely to develop allergies or asthma, has been identified.
For decades, it has been known that children raised in rural areas or near farms are less likely to develop allergies, asthma, and hay fever. New research has identified the bacteria that cause this phenomenon, known as the 'farm effect.'
Gram-Positive Bacteria and the Inverse Association between Farm Exposure and Childhood Asthma | NEJM Evidence
The farm effect – clearer than ever | LMU Hospital
https://www.lmu-klinikum.de/newscenter/press-releases/the-farm-effect-clearer-than-ever/3aac34865e847223
'Natural Protection From Asthma And Allergies': Scientists Isolate Bacteria Behind The Immune System Farm Effect : ScienceAlert
https://www.sciencealert.com/natural-protection-from-asthma-and-allergies-scientists-isolate-bacteria-behind-the-immune-system-farm-effect
The hygiene hypothesis posits that a child's hygienic environment is linked to the development of their immune system. It was proposed in response to the dramatic increase in allergies, asthma, and hay fever among children in industrialized European countries. According to the hygiene hypothesis, children who are not exposed to many microorganisms and viruses in their environment during their early years are more prone to immune system dysfunction and excessive inflammatory responses.
In contrast, children in rural areas who have more opportunities to interact with nature, especially those raised on farms where livestock are kept, are known to experience far fewer similar immune system problems. This is called the farm effect, and it is believed that children's immune systems are trained to avoid excessive inflammatory responses by constantly battling bacteria, their 'sparkling partners,' in the air of livestock barns.
However, the hygiene hypothesis and the farm effect are based solely on observational studies and have not been definitively proven. Therefore, a research team led by Markus Ege, an epidemiologist at the University Hospital of Munich in Germany, conducted research to identify the bacteria and related microbial metabolites that cause the farm effect.
The research team collected samples of nasal mucus and dust from the mattresses of 1,018 elementary school children living in rural southern Germany. They also collected dust samples from cowsheds from 47 children living on farms.
Then, based on state-of-the-art genetic and metabolic analysis of the collected samples, nine types of
Julia Pagani of the Institute for Asthma and Allergy Prevention at the University of Munich, the lead author of the paper, says, 'For example, Romboutsia timonensis and Glutamicibacter arilaitensis . These Gram-positive bacteria mediate two-thirds of the overall effect in asthma prevention and half of the effect against hay fever and atopic dermatitis.'
These bacteria originate from the digestive tract of cattle and produce substances such as kynurenine , xanthine , alpha-linolenic acid , and stearidonic acid . When humans inhale these compounds, they are recognized by aromatic hydrocarbon receptors (AhR) and peroxisome proliferator-activated receptor gamma (PPARγ), which are receptors on human respiratory tract cells.
These receptors have multiple functions, including those related to the immune system, and it is believed that they prevent excessive inflammatory responses. In their paper, the research team stated, 'High levels of AhR activation are harmful, but moderate levels, such as those caused by inhaling bacterial metabolites in a cattle barn, are beneficial.'
While these research findings do not prove a causal relationship, they reveal a biological chain of events: 'Cattle → Barn air → Bacteria → Metabolites → Human receptors → Defense against asthma, etc.'
The research team stated, 'This new discovery can be used by laboratory researchers to elucidate the molecular and cellular mechanisms of the farm effect. This opens up the possibility of developing drugs that mimic the farm effect without children actually having to spend time in a cowshed.'
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