Children's risk for developing allergies and asthma is reduced when they are exposed in early infancy to a dog in the household, and now researchers have discovered a reason why. Exposure of mice to dust from houses where canine pets are permitted both indoors and outdoors can reshape the community of microbes that live in the mouse gut — collectively known as the gastrointestinal microbiome — and also diminish immune system reactivity to common allergens, according to a new study by researchers led by Susan Lynch, Ph.D., associate professor with the Division of Gastroenterology at the University of California at San Francisco (UCSF), and Nicholas Lukacs, Ph.D., professor in the Department of Pathology at the University of Michigan. The scientists also identified a specific bacterial species within the gut that is critical to protecting the airways against both allergens and viral respiratory infection. The study, funded by the National Institute of Allergy and Infectious Diseases (NIAID), was published online on December 16, 2013 in PNAS and involves a multi-disciplinary group of researchers from UCSF, the University of Michigan, the Henry Ford Health System ,and Georgia Regents University. The results were obtained in studies of mice challenged with allergens after earlier exposure to dust from homes with dogs, but the results also are likely to explain the reduced allergy risk among children raised with dogs from birth, according to the study leaders. In their study, the scientists exposed mice to cockroach or protein allergens. They discovered that asthma-associated inflammatory responses in the lungs were greatly reduced in mice previously exposed to dog-associated dust, in comparison to mice that were exposed to dust from homes without pets or mice not exposed to any dust.
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