We all know that breastfeeding helps build stronger, more resilient babies – and finally science came up with a clear answer how exactly breastfeeding supports baby’s immune system.

 A Harvard-Stanford research team has identified a molecule that is key to mothers’ ability to pass along immunity to intestinal infections to their babies through breast milk.

Apparently, there’s amazing change that takes place in a mother’s body when she begins producing breast milk. For years before her pregnancy, cells that produce antibodies against intestinal infections travel around her circulatory system as if it were a highway and regularly take an “off-ramp” to her intestine. There they stand ready to defend against infections such as cholera or rotavirus. But once she begins lactating, some of these same antibody-producing cells suddenly begin taking a different “off-ramp,” so to speak, that leads to the mammary glands.

That way, when her baby nurses, the antibodies go straight to his intestine and offer protection while he builds up his own immunity.

This is why previous studies have shown that formula-fed infants have twice the incidence of diarrheal illness as breast-fed infants.

Until now, scientists did not know how the mother’s body signaled the antibody-producing cells to take the different off-ramp. The new study identifies the molecule that gives them the green light.

“Everybody hears that breastfeeding is good for the baby,” said Eric Wilson, the Brigham Young University microbiologist who is the lead author on the study. “But why is it good? One of the reasons is that mothers’ milk carries protective antibodies which shield the newborn from infection, and this study demonstrates the molecular mechanisms used by the mother’s body to get these antibody-producing cells where they need to be.”

Understanding the role of the molecule, called CCR10, also has implications for potential future efforts to help mothers better protect their infants.

“This tells us that this molecule is extremely important, so if we want to design a vaccine for the mother so she could effectively pass protective antibodies to the child, it would be absolutely essential to induce high levels of CCR10,” said Wilson.

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