Innate Immunity and Asthma Risk in Amish and Hutterite in Farm Children

The Amish and Hutterites are U.S. agricultural populations whose lifestyles are remarkably similar in many respects but whose farming practices are distinct. For example, Amish follow traditional farming practices whereas Hutterites use industrialized farming practices. The two populations also show intriguing disparities in the prevalence of asthma. However, little is known about the immune responses underlying these disparities.

Authors [see article below] studied environmental exposures, genetic ancestry, and immune profiles among 30 Amish and 30 Hutterite children (aged 7-14), measuring levels of allergens and endotoxins and assessing the microbiome composition of indoor dust samples. Whole blood was collected to measure serum IgE levels, cytokine responses, and gene expression, and peripheral blood leukocytes were phenotyped with flow cytometry. Effects of dust extracts obtained from Amish and Hutterite homes on immune and airway responses were assessed in a mouse model of experimental allergic asthma.

Despite the similar genetic ancestries and lifestyles of Amish and Hutterite children, prevalence of asthma was 4 times lower, and allergic sensitization was 6 times lower, in the Amish, whereas median endotoxin levels in Amish house dust was 6.8 times higher. Differences in microbial composition were also observed in dust samples from Amish and Hutterite homes. Profound differences in the proportions, phenotypes, and functions of innate immune cells were also found between the two groups of children. In a mouse model of experimental allergic asthma––the intranasal instillation of dust extracts from Amish, but not Hutterite, homes significantly inhibited airway hyperreactivity and eosinophilia. These protective effects were abolished in mice that were deficient in MyD88 and Trif, molecules that are critical in innate immune signaling.

These results––in humans and mice––indicate that the (dirtier) Amish environment provides protection against asthma by engaging and shaping the innate immune response. This is further evidence in favor of “a little bit of dirt” in the child’s environment appears to be more healthy (with respect to protection against asthma) … than “living in a sterile bubble” during childhood (which is what hover-parents are increasingly doing these days …..

N Engl J Med 4 Aug 2o16; 375: 411–421 (mainarticle)  and  pp 477–479 [editorial]

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