Key to breast-milk antibodies found

A BYU-led research team has unlocked the secret to how a mother's immunity to intestinal infection is passed to her baby through breast milk.

The key was identification of a particular molecule that enables the process, said Eric Wilson, a Brigham Young University microbiologist who led the team, which included BYU undergraduates and researchers from Harvard and Stanford medical schools. The findings are published in the Nov. 1 issue of the Journal of Immunology.

One of the challenges of immunology, Wilson says, is getting white blood cells to the right place so they can fight disease. The blood stream is the highway on which the troops travel to their destination. And this research identifies the molecule that tells the white cells which off-ramp to use when a woman is lactating so that baby will reap the benefits.

Before a woman begins producing breast milk, the cells that make the antibodies against intestinal infection travel through the bloodstream until they reach her intestine, where they ward off infections that might plague her, such as rotavirus. But once she starts lactating, some of those cells begin heading instead for the mammary glands, where they'll ride her breast milk into the baby to protect him until he can develop his own immunity.

For a long time, researchers have understood that breast milk contains antibodies that protect a baby. Breast-fed babies suffer half the diarrheal illness of formula-fed bairn.

"Now we understand how they get to that baby," Wilson said.

The molecule, called CCR10, functions much like one of the numbers in a three-digit address. While the other two are not yet known, CCR10 says "you're getting close. Stop here."

An entirely different molecule, called CCR9, directs the antibody-producing cells when their destination is mom's intestine.

Understanding how the molecules work is expected to open doors to future research, Wilson said.

"If we know how these cells migrate, we'll be able to hit the right targets to get them to go where we want them," said BYU undergraduate and co-author Elizabeth Nielsen Low in a release announcing the research.

Scientists may one day be able to direct cells to the mammary gland or other targets and perhaps increase immunity. Or a vaccine might be developed that could give better immunity to the salivary gland or intestines.

If they can understand how the "addresses" work, in fact, Wilson said, they might be able not only to direct cells but block cells from reaching an address, which could have ramifications for autoimmune diseases. Imagine developing a drug that could prevent inflammation from reaching joints, he said.

Wilson started the research eight years ago when he was at Stanford, which has continued to collaborate on it. Harvard generated the mice with the correct gene knocked out for the project.

The study was supported by a National Institutes of Health grant. Other students who are co-authors are Yuetching Law, Kathryn Distelhorst and Erica D. Hill. Harvard co-authors are Olivier Morteau, Craig Gerard, Bao Lu, Sorina Ghiran and Miriam Rits. The Stanford folks are Raymond Kwan, Nicole H. Lazarus and Eugene C. Butcher.

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