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Microbes Help Mothers Protect Kids from Allergies

ScienceDaily (Dec. 28, 2009) � A pregnant woman's exposure to microbes
may protect her child from developing allergies later in life.
Researchers in Marburg, Germany find that exposure to environmental
bacteria triggers a mild inflammatory response in pregnant mice that
renders their offspring resistant to allergies.

The study will be published online on December 7, 2009 in the Journal of
Experimental Medicine. In an accompanying Commentary, Patrick Holt and
Deborah Strickland discuss the biological mechanisms behind these
findings and how they might one day prevent allergies in people.

The progressive rise in allergies in the past several decades is often
attributed to an increasing tendency to keep kids too clean -- a 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 kids' exposure that
counts; children of farming mothers are also less susceptible to
allergies regardless of their own exposure. But the biological
mechanisms behind this phenomenon were a mystery.

According to the new study by Harald Renz and colleagues at the
Phillips-University of Marburg, pregnant mice exposed to inhaled
barnyard microbes gave birth to allergy-resistant pups. The exposure
triggered a mild inflammatory response in the moms, characterized by the
increased expression 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.


Story Source:

Adapted from materials provided by Rockefeller University Press, via
EurekAlert!, a service of AAAS.


Journal References:

1. Conrad, M.L., et al. Maternal TLR signaling is required for prenatal
asthma protection by the nonpathogenic microbe Acinetobacter lwoffii
F78. J. Exp. Med., 2009; DOI: 10.1084/jem.20090845
2. Holt, P.G., and D.H. Strickland. Soothing signals: transplacental
transmission of resistance to asthma and allergy. J. Exp. Med., 2009;
DOI: 10.1084/jem.20092469
Pages: 1
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