Breast milk antibodies shape infants’ gut bacteria, immunity, study finds

A groundbreaking new study reveals a specific set of antibodies induced naturally by gut-beneficial bacteria can be transferred by mothers to infants through breast milk. These antibodies can help babies defend against deadly infection-generated diarrheal illness.

Researchers from the Gale and Ira Drukier Institute for Children’s Research at Weill Cornell Medicine set their sights on a class of antibodies call IgG. These antibodies help rid the body of infectious viruses and bacteria.

Not much was previously known how these IgG antibodies naturally induced by gut bacteria influenced infant gut immunity. To find out more, scientists used mice to determine how these antibodies are transferred from a mother’s blood to her breast milk and how they protect young mice from a pathogenic equivalent to E. coli.

“We found these IgG antibodies were protective against gut infection in the babies and that we could enhance this protection,” says Dr. Melody Zeng, senior author and assistant professor of immunology in pediatrics with the Department of Pediatrics at Weill Cornell Medicine, in a statement.

Researchers developed a vaccine using a component found in gut bacteria and then immunized female mice with it before they became pregnant.

“The same concept, in which vaccination enhances mothers’ IgG antibody levels and transfers this immunity to her babies, could protect human babies,” says Dr. Zeng. “This strategy could especially benefit premature babies, since they tend to be at much higher risk for diarrheal diseases.

Diarrheal diseases are the second leading cause of death among children under 5.

Researchers found that when IgG antibodies were passed to infant mice through breast milk, they prevented disease-causing bacteria from attaching themselves to the lining of infants’ intestines.

Weill Cornell Medicine scientists also studied how these specific antibodies interacted with a separate set of microbes — beneficial bacteria that live in the gut — to facilitate the healthy development of gut bacteria in infants. They found that “helpful bacteria train the immune system to recognize their pathogenic relatives.”

“Our findings really underscore the benefits of breastfeeding, both immediately and for the long-term development of the immune system in the offspring, says Dr. Zeng.

The study even uncovered long-term effects of these protective antibodies. The immune systems changed for mice that never received IgG antibodies from their mothers. These mice ended up developing abnormal microbial communities within their guts. Adult mice who were IgG deprived were more susceptible to abnormal inflammation associated with inflammatory bowel disorder.

The study is published in the journal Science Immunology.

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