The bacteria in house dust make the difference - what constitutes the farm effect?

Allergic diseases have become widespread diseases in recent decades due to the dramatic increase in the number of new cases. This trend is particularly noticeable in urban agglomerations. The situation is different to rural regions, where farming is still traditionally rural. The so-called farmer studies impressively elucidate that farmer children who still have direct contact with farm animals and consume non-processed products from these animals from childhood on are protected from allergic diseases such as bronchial asthma. In a recently published study, which was conducted in Finland as part of the Europe-wide long-term PASTURE/LUKAS study, the underlying relationships could now be further broken down. With the participation of the Biobank Marburg, the study team has now reported in the renowned journal "Nature Medicine" that the microbial composition of indoor air in children's homes plays a decisive role in protecting them against asthma. The team led by Juha Pekkanen from Kuopio/Finland, together with other European colleagues, examined farmers' and non-farmers' children for allergies and asthma and took house dust samples from the homes of these children. The investigation of the microbial composition of the house dust revealed that the composition and diversity of the bacteria and fungal spores contained in the house dust contribute significantly to asthma protection. The more similar the composition of the so-called house dust microbiota is to that of farmhouse dust, the greater the childhood protection against asthma. Even children who do not grow up on farms are protected against asthma if the indoor air contains a farm-like house dust microbiota. Data from the German Gabriela study, which was similar in design to the PASTURE/LUKAS study, confirmed these findings. The Marburg group contributed to these results by determination of cytokines in immune-stimulated blood samples taken from the study children. These messenger substances formed by immune cells after contact with environmental factors can have either an inflammatory or anti-inflammatory effect. In the blood of the children who breathed in the asthma-protective house dust at home, significantly fewer inflammatory cytokines were found than in the blood of the remaining children. The study supports the hypothesis that early and prolonged contact with a diverse bacterial environment favors the development of a balanced immune system and can prevent excessive reactions of the immunological defence. Bacterial components from the natural environment are thus moving into the focus of the prevention of allergic as well as autoimmune diseases and could in future offer new clinically applicable possibilities for the prevention of chronic inflammatory diseases.
Reference: Farm-like indoor microbiota in non-farm homes protects children from asthma development Kirjavainen PV, Karvonen AM, Adams RI, Täubel M, Roponen M, Tuoresmäki P, Loss G, Jayaprakash B, Depner M, Ege MJ, Renz H, Pfefferle PI, Schaub B, Lauener R, Hyvärinen A, Knight R, Heederik DJJ, by Mutius E, Pekkanen J. Nat Med. 2019 Jun 17. doi: 10.1038/s41591-019-0469-4.