What’s so special about living in the farm?  Researchers knew that being born and raised in a farm provides a long-lasting protection for allergies. Indeed, children who are in contact with farm animals early on are less likely to develop atopic sensitization when they are adults (Grethe Elholm et al, 2013). The microbial environment provided by farm animals is crucial to induce this protective effect, although underlying immune mechanisms remain elusive.

The researchers from Swiss National Science Foundation (SNSF) study immunologic changes linked to protection of allergy. Strong activation of the innate immune system with microbial products may boost organisms to an immune status less prone to develop allergies.

Researchers bred mice colonies in both a farm cowshed and the university laboratory animal facility (AF). Then, they tested both sets of animals for skin contact allergy model. They also measured peripheral blood cells and cell cytokine production and characterized at various ages the gut microbiome of both populations.

The researchers tested contact hypersensitivity by applying the allergen FITC to the ears of the mice. Mice raised in the AF group developed three times more ear swelling than the farm mice (Christophe P. Frossard et al, 2017).  After that, they transferred some of the young AF mice to the farm. These resulted in AF mice with the same protection as being born on the farm. In addition, AF mice have better protection when they were moved to the farm early in life.

Next, the researchers examined the immune system of both group of populations. The immune systems of farm mice appeared to be activated earlier in life; they had a higher CD4+ T cell population, in particular CD4+CD25+FoxP3− (activated cells). The cytokine profile of mice from the farm was skewed towards an IL-17 and IL-22 secreting cell profile accompanied by increased IL-10 secretion. These differences were mostly seen within a specific age window between birth and 8 weeks of age.

The group next examined the gut microbes of the farm and AF mice. They reasoned that there may be a specific microbe that helps trigger immune tolerance in the farm mice. Interestingly, microbiome analysis showed differences between 4 and 20 weeks old mice and between farm and AF mice with an increased number of Murine mastadenovirus B in young farm mice exclusively. There was also a significant difference in the proportion of Lactobacillus, Alistipes, Reburial, Adlercreutzia, and Clostridium between the farm and AF mice.

According to the authors, “The farming environment provides a strong, allergy protective IL-22 stimulus and generates activated CD4+ T cells. Exposure to the farm environment early in their life may also provide a better protection for contact skin allergy. Whether a viral trigger might decisively influence protection for allergies remains to be determined”.

Other research from Aarhus University has demonstrated that adults who move to farming areas after have being living for a while in cities may reduce the symptoms of their hypersensitivities and allergies considerably (Grethe Elholm et al, 2013). 

The immune systems of people who work in farming are frequently exposed to a wide range of bacteria, fungi, pollen and other irritants which may trigger a response that protects them against hypersensitivity. Working in a farming environment may therefore serve to prevent or dampen hypersensitivity to the most widespread plant allergens: grass and birch pollen.

Surprisingly, the positive effect on the immune system is seen both in people who have lived in urban environments and in adults who were born and raised in farming areas.  Previously, the assumption was that only persons who had lived in farming areas while growing up would benefit from the environment's protective effect on the immune system. But now the study of Aarhus University demonstrated that it's not too late simply because you are an adult.

However, researcher simply recommends that people who suffer from allergies and hypersensitivities move to farms. Because they may also suffer from lung diseases such as asthma and would therefore become more ill due to the high concentrations of dust and particles found in stables and in agriculture in general.

This knowledge is now bringing researchers closer to discovering how to prevent allergies. The assumption is that the absence of environmental exposure does not protect against hypersensitivity. In general, exposure to the farming environment dampens the entire immune response to the environment because it stimulates the immune system.

 

COPYRIGHT: This article is property of We Speak Science, a nonprofit institution co-founded by Dr. Detina Zalli (Harvard University) and Dr. Argita Zalli (Imperial College London). This article is written by MSc. Gjena Dura (Molecular Biologist, BIO-V Food and Veterinary Laboratory)

REFERENCES: 

  • Christophe P. Frossard, Vladimir Lazarevic, Nadia Gaïa, Stefano Leo, Camille Doras, Walid Habre, Jacques Schrenzel, Danielle Burger, Philippe A. Eigenmann. The farming environment protects mice from allergen-induced skin contact hypersensitivity. Clinical & Experimental Allergy, 2017; DOI: 10.1111/cea.12905 <http://onlinelibrary.wiley.com/doi/10.1111/cea.12905/abstract>
  • Swiss National Science Foundation (SNSF). "How stable manure protects against allergies." ScienceDaily. ScienceDaily, 8 March 2017. <www.sciencedaily.com/releases/2017/03/170308083717.htm>.
  • https://www.readbyqxmd.com/read/28198584/the-farming-environment-protects-mice-from-allergen-induced-skin-contact-hypersensitivity
  • Grethe Elholm, Vivi Schlünssen, Gert Doekes, Ioannis Basinas, Bo Martin Bibby, Charlotte Hjort, Pernille Milvang Grønager, Øyvind Omland, Torben Sigsgaard. Become a farmer and avoid new allergic sensitization: Adult farming exposures protect against new-onset atopic sensitization. Journal of Allergy and Clinical Immunology, 2013; DOI: 10.1016/j.jaci.2013.07.003
  • Aarhus University. "The immune system benefits from life in the countryside." ScienceDaily. ScienceDaily, 30 September 2013. <www.sciencedaily.com/releases/2013/09/130930101841.htm>.