Microbes help mothers protect children from allergies

In a study published online on December 7, 2009 in the Journal of Experimental Medicine, researchers in Marburg, Germany found that exposure to environmental bacteria triggered a mild inflammatory response in pregnant mice that rendered their offspring resistant to allergies.

The progressive rise in allergies in the past several decades is often attributed to an increasing tendency to keep children too clean – the theory known as the hygiene hypothesis. According to this theory, exposure of young children to environmental microbes conditions the developing immune system to tolerate microbes and allergens later in life. Studies have shown, for example, that children raised on farms, which teem with microbes, developed fewer allergies than those raised in cities or non-farming rural regions. But it may not be the children's exposure that count as the children of farming mothers are also less susceptible to allergies regardless of their own exposure.

In this new study pregnant mice, exposed to inhaled barnyard microbes, gave birth to allergy-resistant pups. The exposure triggered a mild inflammatory response in the mothers – an increased production of microbe-sensing 'Toll-like' receptors (TLRs) and the production of immune molecules called cytokines. The maternal TLRs were essential for transmitting protection, but how TLR signals translate into allergy resistance in the offspring is not yet known. It also remains to be seen whether the protection applies to a broad range of allergens, including those found in food.

Conrad, M.L., et al. 2009. J. Exp. Med. doi:10.1084/jem.20090845.
Holt, P.G., and D.H. Strickland. 2009. J. Exp. Med. doi:10.1084/jem.20092469.

Courtesy of EurekAlert

First published in December 2009

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