Mothers conferred immunity to allergen; not known if findings apply to humans
MONDAY, Jan. 28 (HealthDay News) -- Breast-feeding helped protect baby mice from developing allergic asthma, a new study found.
The mice that were breast-fed by mothers that had been exposed to an allergen "inherited" the allergen and developed tolerance to it.
But once again, a central question is whether such an animal study can be extrapolated to humans.
"You hate to translate data on mice to data on humans," said Dr. Jennifer Wu, an obstetrician/gynecologist at Lenox Hill Hospital in New York City. "I wouldn't necessarily apply this to humans, especially because it's mice and not primates."
The findings were published online Jan. 27 in the journal Nature Medicine.
The incidence of allergic diseases such as asthma, food allergies and various skin conditions has soared during the past few decades. In children 4 years of age and younger, the incidence of asthma has risen 160 percent, while the incidence of atopic dermatitis, which includes eczema, has almost tripled. The incidence of peanut allergy has doubled just during the past decade, according to the American Academy of Pediatrics.
Although genetic factors clearly play a role in the trends, researchers have intensified their efforts to find environmental contributors. And, in fact, exposure to allergens in the environment during infancy reduces the risk of developing asthma.
It's been unclear, however, if breast-feeding has an impact on the development of allergic disease.
Earlier this month, the American Academy of Pediatrics (AAP) issued a report concluding that atopic disease, which includes eczema, asthma and food allergies, may be delayed or prevented in high-risk infants if they're exclusively breast-fed for at least four months or fed infant formula without cow milk protein.
"The article from AAP actually found conflicting data on asthma and breast-feeding," Wu said. "Breast-feeding did decrease wheezing in infants but didn't seem to decrease overall asthma."
For the new study, French researchers exposed lactating mice to an airborne allergen, ovalbumin, which is the main protein found in egg whites. Ovalbumin was transferred from the mother to the baby via breast milk and conferred immunological tolerance to the allergen.
The baby mice exposed to ovalbumin showed decreased airway "hyper-reactivity" and decreased mucus in the airways, among other benefits.
"No other experimental study has investigated whether exposure of lactating mice to an airborne allergen would impact asthma development in progeny. The allergen exposure was only restricted to the lactation phase starting one day after delivery to three weeks (weaning time)," said study senior author Valerie Julia, a permanent researcher with the National Institute of Health and Medical Research, University of Nice-Sophia-Antipolis in Valbonne.
"We found that airborne antigens are efficiently transferred from the mother to the neonate through milk. We believe that the presence of the allergen in milk together with the immunosuppressive molecule called TGF-beta "instructs" the immune system of the neonate not to over-react against the allergen," Julia added.
Although more studies need to be done to confirm the potential effect in humans, as Wu pointed out, "there are other huge benefits of breast-feeding in terms of nutrition and emotional bonding."
The American Academy of Pediatrics has more on breast-feeding your infant.
SOURCES: Jennifer Wu, M.D., obstetrician/gynecologist, Lenox Hill Hospital, New York City; Valerie Julia, Ph.D., permanent researcher, National Institute of Health and Medical Research, University of Nice-Sophia-Antipolis, Valbonne, France; Jan. 27, 2008, Nature Medicine, online
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