Breast milk antibody benefits

Antibodies present in breast milk play a key role in the early development of the intestine and its bacterial passengers and should be considered as an additive for formula feeds in some situations, a study has shown.

The benefits of breast-feeding have been known for many years and include a reduced risk of allergies, diarrhoeal diseases and subsequent inflammatory bowel diseases.

This is thought to be due to changes in the intestinal bacterial microflora, which occur in response to dietary factors.

An important component of breast milk are antibodies, which are secreted into the milk from the mother's bloodstream and are notably absent from milk formula feeds.

But what effect these antibodies might have, if any, on the spectrum of bacteria that take up residence in the intestines of both young animals and adults wasn't known.

To find out, Eric Rogier and his colleagues at the University of Kentucky took the ingenious step of engineering mice that could produce milk that lacked these antibodies. In this way they could separate any influence of the antibodies from the other components of the breast milk.

Writing in PNAS, the team counted the diversity of bacteria present in the guts of pups and adults reared either by normal mothers, or mice with milk lacking the chief IgA antibody normally present in breast milk.

Antibody IgA in the milk, they found, altered the levels of over 1000 bacterial species in young animals. This persisted after weaning into adulthood, with differences in nearly 500 bacterial species measured in weaned animals.

When the team studied the lining and lymph glands of the intestines of young mice, they found that the absence of antibodies in breast milk was leading to higher levels of bacteria invading the lymph glands and evidence of biochemical stress and altered gene expression in the epithelial cells which coat the gut surface.

The changes to  the spectrum of bacteria in the guts of mice reared on milk lacking the antibody were also similar to changes documented previously amongst human patients with inflammatory bowel diseases.

On the basis of their findings, the Kentucky team conclude that "oral administration of purified IgA could be investigated as a biological therapy for intestinal infections and inflammation, particularly in formula-fed infants..."