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Mother’s gut microbiota strengthens newborn's immunity

No. 15c | 18/03/2016 | by Koh

Already during pregnancy, microbes in the mother’s gut shape the baby's immune system. This effect is brought about by microbial molecules that are transmitted to the baby across the placenta or via antibodies in the mother's milk. Scientists from Bern University Hospital, the University of Bern, the German Cancer Research Center (DKFZ) and ETH Zurich have now reported this finding in an article published in Science.

© Rocky Mountain Laboratories, NIAID, NIH [Public domain], via Wikimedia Commons

Babies are born with immature immune systems. Up until now, scientists have assumed that newborns start after birth to adapt to the host of microorganisms that compose their own intestinal microbiome. In experiments with mice, scientists from Bern University Hospital, the University of Bern, the German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ) and ETH Zurich have now discovered that the mother's gut microbiota prepares the baby already in the womb for the process of microbial colonization that takes place after birth. The gut research group at the University Hospital of Bern (Inselspital) has been pursuing basic and clinical research in this field for many years and ranges among the world's most renowned research teams. Mathias Heikenwälder from the DKFZ and his group supported their Swiss colleagues by conducting an analysis of the immune system, particularly of the secondary lymphatic organs, during this phase in immune development.

Microbial invasion after birth

When a baby is born, it leaves the sterile, sheltered environment of the uterus and enters a world that teems with microbes. After birth, microorganisms quickly colonize all surfaces of the body. Within a few days, the intestine is inhabited by ten times more microbes than there are cells in the baby's whole body.

Newborns normally survive this sudden invasion of bacteria without problems. However, more than six million infants under the age of five still die worldwide each year, most of them as a result of intestinal infections or malnutrition. The critical challenge after birth is that trillions of microbes must colonize the intestine without infecting the newborn, provoking a strong immune response or impeding the gut's capacity to absorb nutrients.

Harmless molecules from the gut

In their current article, the researchers report that molecules of microbes living in the maternal intestine can enter the mother's body and then get transmitted to the baby via the placenta or, after birth, during breast feeding via antibodies that are contained in the mother's milk. These microbial fragments are harmless and do not cause any infection. Instead, they stimulate cells in the baby's body to prepare its immune system and gut for the time after birth when the newborn has to cope with the microorganisms living in its own intestine.

“For this work, we studied bacteria that do not cause disease,” says Heikenwälder. “But our results most likely also hold true for dangerous pathogens, against which the newborn can produce a better defense thanks to this preparation of the immune system.” Andrew Macpherson, Research Director at Bern University Hospital, added: “We have always known that we may be grateful to our mothers for their love and protection, now we know that we should also be grateful to them for their gut microbiota.”

Mercedes Gomez de Agüero, Stephanie C. Ganal-Vonarburg, Tobias Fuhrer, Sandra Rupp, Yasuhiro Uchimura, Hai Li, Anna Steinert, Mathias Heikenwälder, Siegfried Hapfelmeier, Uwe Sauer, Kathy D. McCoy, Andrew J. Macpherson: The maternal microbiota drives early postnatal innate immune development: Science 2016, DOI: 10.1126/science.aad2571

The German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ) with its more than 3,000 employees is the largest biomedical research institute in Germany. At DKFZ, more than 1,000 scientists investigate how cancer develops, identify cancer risk factors and endeavor to find new strategies to prevent people from getting cancer. They develop novel approaches to make tumor diagnosis more precise and treatment of cancer patients more successful. The staff of the Cancer Information Service (KID) offers information about the widespread disease of cancer for patients, their families, and the general public. Jointly with Heidelberg University Hospital, DKFZ has established the National Center for Tumor Diseases (NCT) Heidelberg, where promising approaches from cancer research are translated into the clinic. In the German Consortium for Translational Cancer Research (DKTK), one of six German Centers for Health Research, DKFZ maintains translational centers at seven university partnering sites. Combining excellent university hospitals with high-profile research at a Helmholtz Center is an important contribution to improving the chances of cancer patients. DKFZ is a member of the Helmholtz Association of National Research Centers, with ninety percent of its funding coming from the German Federal Ministry of Education and Research and the remaining ten percent from the State of Baden-Württemberg.

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