Feeding breast milk to developing infants gives a substantial boost to their immune system. A cocktail of nutrients, immune-boosting factors, and stem cells, breast milk provides a multitude of ingredients that help a baby’s immune system mature. But pinning down the exact mechanism in which it does this has proved a difficult task for researchers.

Now, in a study published as a preproof in Gastroenterology, researchers from the RESIST Cluster of Excellence at Hannover Medical School (MHH) and the University of Bonn believe they have found the proteins that could be responsible.

The proteins, called alarmins, are found in extremely high concentrations in breast milk and breast-fed babies, and are thought to play an important role in the development of a mature intestinal immune system.

"Alarmins are the 'gold' in breast milk. These proteins prevent dangerous intestinal colonization disorders that can lead to blood poisoning and intestinal inflammation," explained Prof. Dr Dorothee Viemann of the Hannover Medical School (MHH) Clinic for Pediatric Pneumology, Allergology and Neonatology in a statement.

As a newborn matures, so too do the bacteria in their gut. Microbes colonize the intestinal wall, creating a thriving microbiome that helps the infant build an immune system against nastier pathogens that wish to do them harm. Should this microbiome develop differently to normal, complications – like inflammatory bowel disease (IBD) – can occur.

This is where alarmins come in. Healthy newborns typically have high levels of alarmins, leading the researchers to believe they could play a crucial role in normal microbiota development. After studying 517 stool samples from infants and measuring the level of alarmins present, the researchers found that alarmins regulate the development of a healthy array of microbes in the gut by interactions with immune cells. It is this microbiome that then interacts with the host immune system, preventing the onset of microbe-associated gastrointestinal disease.

Many mothers are unable to breastfeed for a variety of reasons, however, Professor Viemann believes that whilst fully mimicking breast milk into a packable formula may never be possible, these results could have huge implications for more effective formula and supplements in the future.

"Supplementation with these proteins could support the development of newborns which do not produce enough alarmins or get enough in breast milk. That could prevent a range of long-term conditions linked to intestinal colonization disorders, such as chronic intestinal inflammation and obesity," said Professor Viemann.

With around 1.6 million Americans living with IBD currently, it is hoped that further understanding of the intricate mechanisms behind the microbiome will help alleviate the disease. The authors are now planning further work – including a possible clinical study – based on this new discovery and hope that using alarmins as a supplement may afford some protection against microbial-related diseases.