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How farm life can prevent allergies: in mice, dust molecule turns on anti-inflammatory enzyme.

Preventing many allergies could be as simple as taking a breath--of farm dust.

Dust from dairy farms switches on an anti-inflammatory enzyme in the lung cells of mice, researchers report in the Sept. 4 Science. The enzyme keeps the immune system from overreacting to common allergens, such as house dust mites, the team found.

It's the first time researchers have pinned down a specific molecule that explains how farm dust can prevent allergies, says Donata Vercelli, an immunologist at the University of Arizona in Tucson. "This won't be the end of the story, but it's certainly a good beginning."

Scientists have known that farm life seems to protect kids from developing asthma and hay fever. Contact with animals, drinking raw milk and breathing farm air all could play a role. But no one knows exactly how.

Pulmonary physician Bart Lambrecht of Ghent University in Belgium and colleagues collected dust from stables and dairy farms in Germany and then let some mice inhale a tiny bit of dust every other day for two weeks. These mice then sniffed house dust mites, an allergen that usually triggers asthma in mice.

Mice that had been breathing farm dust didn't get asthma. A genetic analysis of the cells lining the mice's lungs revealed that Tnfaip3, the gene for making the enzyme A20, had been switched on. A20 tells lung cells to chill out, so they don't fire up the immune system unnecessarily. The enzyme removes ubiquitin, a molecule that sticks to proteins and can signal cells to dial up inflammation.

But A20 isn't called to duty unless farm dust is around, the researchers found. The dust ingredient that protects against allergies maybe bits of bacteria called endotoxin. A separate experiment exposing mice to just endotoxin also protected the mice from asthma. In real life, the endotoxin could come from dried-out cow manure that has crumbled to dust, Lambrecht says. Wind can pick up the tiny particles and loft them into the air. "We're used to breathing this in," he says.

The mouse findings could translate to humans. Surveying a database with medical and residential information on 1,707 children from four European countries uncovered the same link between farm dust and allergies that the researchers found in mice.

Lambrecht thinks that some kids may live in houses that are just too clean. Nowadays, people use hospital-grade antiseptic soaps to scrub floors and sinks, he says. "There's no reason why our kitchen sinks should be sterile."

Stewart Levine of the National Heart, Lung and Blood Institute in Bethesda, Md., says the work offers a new mechanism for explaining how cells in the lungs can prevent allergic airway inflammation. But, he says, "I don't know if I would take my kid and put them in a barn based on this paper."

Caption: Inhaling farm dust may prevent allergies. Dried cow manure could harbor molecules that calm down lung cells even in the face of allergens.


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Title Annotation:BODY & BRAIN
Author:Rosen, Meghan
Publication:Science News
Geographic Code:1USA
Date:Oct 3, 2015
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