Nav: Home

Breastfeeding is good for yet another reason, researchers discover

May 05, 2016

A mother's breast milk supports immune responses in her newborn that help the infant's gut become a healthy home to a mix of bacterial species, thanks in part to newly identified antibodies from the mother, according to a study by UC Berkeley researchers.

Scientists believe the gut is sterile and bacteria-free at birth, when suddenly the infant is exposed to bacteria from the wider world. The body learns to tolerate many bacterial species, and the relationship is regarded as mutually beneficial -- in exchange for free meals, gut bacteria aid digestion, help prevent infection and enhance immune function.

The new study sheds light on how immune antibodies from breast milk interact with the just-forming immune system of the newborn to help shape lifelong immune responses that are key for establishing boundaries and balance between gut microbes and the mammalian host. If this balance fails to become established or later falters, chronic inflammatory conditions, such as Crohn's disease or ulcerative colitis, may result.

A healthy relationship between host and bacteria is deemed to be "commensal," essentially meaning that neither is harmed.

In their studies of mice, Gregory Barton, the Class of '36 Chair in the Department of Molecular and Cell Biology, and post-doctoral fellow Meghan Koch, found that three specific types of antibodies, called Immunoglobulin A (IgA), Immunoglobulin G2b (IgG2b), and immunoglobulin G3 (IgG3), are present in breast milk and promote peace between the immune system and common gut-dwelling bacteria by putting the damper on inflammatory responses.

"This study provides real evidence that breast milk is important for a newborn's health," said Koch, who designed and conducted most of the experiments. "Breastfeeding helps to instruct the newborn's immune system on how to appropriately respond to non-pathogenic bacteria, many of which may reside in the gut for a lifetime."

Barton, Koch and their colleagues published their findings in the May 5, 2016 issue of the journal Cell.

IgA antibodies in milk had been identified earlier, but thought mainly to function to fight pathogens and to prevent bacteria from penetrating the gut wall and entering the circulation. IgG antibodies had been known to enter the infant in utero, and to help fight infection.

There are other components in breast milk known to shape the composition of the gut microbiota. As evidence for a long and evolving relationship between mammals and gut microbes, scientists previously identified sugars in breast milk that commensal bacteria can derive energy from, but which are indigestible to the infant.

In addition, there are other molecules in breast milk, made by the mother's immune system, that promote tolerance for commensal microbes while keeping them in the gut and away from the rest of the body.

The UC Berkeley scientists detected IgG2b- and IgG3-triggered immune responses directed toward commensal bacteria in two-week-old mice. These responses waned after three weeks, and grew stronger again in older mice. "The presence of these antibodies in young mice suggested that, like IgA, they are maternally derived," Koch said.

When she genetically eliminated maternal-derived IgG2b, IgG3 and IgA antibodies, the mice were more susceptible to inflammatory responses caused by commensal microbes.

Barton said the distinctive immune responses by the newborn's immature immune system were "surprising." The researchers found that the antibody responses against the gut microbiota did not depend on arousing the T helper cells that are the foot soldiers of the evolutionarily advanced "adaptive" immune system, but instead relied on signaling by the earlier-evolved, innate immune system.

The immune responses may serve to set up the immune system to eliminate commensal bacteria that might escape the gut and enter the circulation, without triggering an overwhelming inflammatory response, Barton said.

"What we have learned is that it is important for the immune system to recognize and to make an immune response to microbiota in the gut, but this response is qualitatively different than the immune response to pathogens," Barton said.

"We identified breast milk as a primary source of IgG antibodies that are directed against commensal bacteria early in life and demonstrated that this maternally acquired, anti-commensal IgG helps dampen T-helper-cell-driven immune responses against newly encountered microbes."

"While our study demonstrates the importance of commensal-specific IgG antibodies when acquired maternally, it is certainly possible that they serve important functions in adults, as well," he added.
-end-
The work was supported by the National Institutes of Health (Grants AI063302, AI095587, AI104914). UC Berkeley co-authors of the paper include Gabrielle Reiner, Kyler Lugo, Lieselotte Kreuk, Alison Stanbery, Eduard Ansaldo, Thaddeus Seher and William Ludington.

University of California - Berkeley

Related Immune System Articles:

Too much salt weakens the immune system
A high-salt diet is not only bad for one's blood pressure, but also for the immune system.
Parkinson's and the immune system
Mutations in the Parkin gene are a common cause of hereditary forms of Parkinson's disease.
How an immune system regulator shifts the balance of immune cells
Researchers have provided new insight on the role of cyclic AMP (cAMP) in regulating the immune response.
Immune system upgrade
Theoretically, our immune system could detect and kill cancer cells.
Using the immune system as a defence against cancer
Research published today in the British Journal of Cancer has found that a naturally occurring molecule and a component of the immune system that can successfully target and kill cancer cells, can also encourage immunity against cancer resurgence.
First impressions go a long way in the immune system
An algorithm that predicts the immune response to a pathogen could lead to early diagnosis for such diseases as tuberculosis
Filming how our immune system kill bacteria
To kill bacteria in the blood, our immune system relies on nanomachines that can open deadly holes in their targets.
Putting the break on our immune system's response
Researchers have discovered how a tiny molecule known as miR-132 acts as a 'handbrake' on our immune system -- helping us fight infection.
Decoding the human immune system
For the first time ever, researchers are comprehensively sequencing the human immune system, which is billions of times larger than the human genome.
Masterswitch discovered in body's immune system
Scientists have discovered a critical part of the body's immune system with potentially major implications for the treatment of some of the most devastating diseases affecting humans.
More Immune System News and Immune System Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.