Amish children’s exposures protect against asthma through reprogramming innate immunity

Iowa research finds house dust differences between communities affects immune development

By probing the differences between two farming communities—the Amish of Indiana and the Hutterites of South Dakota—an interdisciplinary team of researchers, including Peter Thorne, professor and head of the University of Iowa’s Department of Occupational and Environmental Health, found that specific aspects of the Amish environment are associated with changes to immune cells that protect children from developing asthma.

In the Aug. 4, 2016, issue of The New England Journal of Medicine, the researchers showed that substances in the house dust from Amish, but not Hutterite, homes were able to engage and shape the innate immune system (the body’s front-line response to most microbes) in young Amish children in ways that may suppress pathologic responses leading to allergic asthma. The study is available online.

While the Amish and Hutterite communities have a similar genetic ancestry and share similar lifestyles, customs, and diets, their farming practices differ. The Amish have retained traditional methods. They live on single-family dairy farms and rely on horses for fieldwork and transportation. In contrast, the Hutterites live on large communal farms and use modern, industrialized farm machinery. This distances young Hutterite children from the constant daily exposure to farm animals.

Another striking difference between the two communities is the large disparity in asthma cases. About 5 percent of Amish schoolchildren aged 6 to 14 have asthma. This is about half of the U.S. average (10.3%) for children aged 5 to 14, and one-fourth of the prevalence (21.3%) among Hutterite children.

To understand this disparity, the researchers studied 30 Amish children 7 to 14 years old, and 30 age-matched Hutterite children. They scrutinized the children’s genetic profiles, which confirmed the remarkable similarities between Amish and Hutterite children. They compared the types of immune cells in the children’s blood, collected airborne dust from Amish and Hutterite homes and measured the microbial load in homes in both communities.

Thorne’s group, which also included Dr. Nervana Metwali from the UI’s Department of Occupational and Environmental Health, deployed novel air samplers for the study that do not require electricity. These Electrostatic Dust Samplers were placed into Amish and Hutterite homes to measure airborne particles and toxins in order to assess differences in exposures between these populations.

Results of the study showed that dust collected from Amish homes was “much richer in microbial products,” the authors note, than dust from Hutterite homes.

Thorne explained, “When we administered extracts of the two types of dust to mice, we were able to reproduce the differences in respiratory allergy that we observed in the Amish and Hutterite children.”

“The study augments prior work showing the significant role our environmental exposures play in asthma,” Thorne said. “The big advance is how our study beautifully demonstrated the key role of innate immunity in asthma in two rural populations with similar genetics.

“This is a great example of a major discovery arising from a multidisciplinary team of scientists drawn from multiple universities,” Thorne added. “Each member of the team brought unique scientific knowledge to the research.”

The National Institutes of Health, National Institute of Environmental Health Sciences, the St. Vincent Foundation, and the American Academy of Allergy, Asthma & Immunology Foundation supported the study.

The study included researchers from the University of Chicago, the University of Arizona, Dr. von Hauner Children Hospital in Munich, Germany, and Allergy and Asthma Consultants, Indianapolis.

Media Coverage

Barnyard Dust Offers a Clue to Stopping Asthma in Children (The New York Times)

Amish kids help scientists understand why farm life reduces the risk of asthma (Los Angeles Times)

How a Cow in Your Living Room Could Make the Difference for Asthma and Allergies (Iowa Public Radio)