PARIS, January 27, 2008 - French scientists studying lactating mice say
they can add an important piece of evidence to a charged debate as to whether
breastfeeding helps protect a child against asthma.
   In a paper published online on Sunday by the journal Nature Medicine, a
National Institute for Health and Medical Research (Inserm) team exposed
lactating mice to airborne dust containing ovalbumin, a well-known asthma
allergen that is found in egg whites.
   The mother mice transmitted the allergen to their newborn through the milk,
helping the offspring to develop an immunological tolerance to the irritant.
   The tolerance was induced thanks to the presence of TGF beta, an important
signalling protein, in the breast milk.
   Breastfed mice whose mother had been exposed to ovalbumin were far less
likely to develop wheezing, airway mucus and other asthma symptoms than
non-breastfed counterparts.
   "Breast-feeding induced tolerance may rely on both the chronic
administration of an antigen at a low dose, a setting known to promote
tolerance induction, and the presence of milk-borne TGF beta," they suggest.
   Asthma is a worsening health problem that affects 300 million people
worldwide, although the causes for it are complex.
   One suspected source is exposure to allergens such as tobacco smoke, pollen
and mites while in childhood.
   These allergens in later life are identified as intruders by the immune
system's T helper type-2 cells. They go into overdrive, causing the airways to
inflame and constrict.
   Some research, conducted among populations rather than in the lab, has
suggested that newborns can develop a tolerance to airborne antigens through
breastfeeding.
   Other research, though, has found no difference. Some studies have even
suggested breastfeeding may accentuate the risk of asthma.
   But the Inserm researchers note that these studies do not take into account
the mother's exposure to airborne allergens at the time when they were
breastfeeding -- nor did they measure levels of antigens in breast milk.
   That avenue of exploration should now be opened up in the light of the new
findings, they say.

AFP