(Ivanhoe Newswire) -- A pregnant woman's exposure to microbes may protect
her unborn child from developing allergies later in life.
Researchers in Marburg, Germany found 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 kids too clean -- a theory known as
the hygiene hypothesis. According to this theory, exposing 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.
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.
SOURCE: Journal of Experimental Medicine, December 7, 2009
