Naturally Immune For Life

The development of a healthy immune system begins shortly after birth and during this important time, the gut microbiome helps teach the immune system how to respond appropriately to environments. Beneficial bacteria, especially Bifidobacterium infantis (B. infantis), play an important role in this process as these bacteria are specially equipped to use human milk oligosaccharides (HMOs), natural sugars found in breast milk. HMOs help beneficial bacteria grow and produce substances that communicate with the immune system and when these early microbial communities are disrupted, the immune system does not develop in the same balanced way, increasing the risk of inflammation, allergies, and respiratory problems later in life. 

A 2026 study published in Cell Reports Medicine explored whether restoring these helpful bacteria and their food supply could improve early immune development. This large study conducted at several sites across Europe found that giving babies a combination of beneficial bacteria and substances that help them grow, called synbiotics, reduced the strong Th2 response and the imbalance in Th17 immune cells by four months of age. Researchers studied formula-fed infants who received a special combination of B. infantis, another beneficial bacterium called B. lactis, and six different HMOs. The researchers compared their immune responses with infants receiving regular formula and a separate group of exclusively breastfed infants. By four months of age, infants receiving the special combination had fewer Th2 immune cells than infants receiving regular formula. Their immune pattern moved closer to the pattern seen in breastfed infants. Th2 cells are important for fighting certain infections, but an overly strong Th2 response can also contribute to allergic inflammation. The research was conducted by scientists at Nestlé Research, who investigated how combining beneficial gut bacteria with human milk oligosaccharides (HMOs) could help support healthy immune development during infancy.

The benefits were even more remarkable in animal studies. The researchers used standard, wild-type mice. Researchers gave young mice the same combination of B. infantis and six HMOs. The mice were then exposed to a virus that causes a respiratory illness similar to RSV in humans. Mice with an unhealthy gut environment developed more severe lung damage and inflammation but those receiving the complete synbiotic combination had less lung damage, better control of the virus, and a more balanced immune response. Notably giving the HMOs alone or the bacteria alone did not provide the same level of protection demonstrating that the combination of the right bacteria and the food they need is critically important for healthy immune development. The researchers did not compare the mouse results directly with the human infants. Instead, the mouse experiments investigated whether the same general synbiotic combination that changed immune patterns in human infants could also produce measurable protection against disease in an experimental animal model but the mouse study provided additional evidence of potential biological benefits, including protection against respiratory infection and later allergic airway inflammation.

The researchers also discovered an important connection involving a substance called 12-HHT. This natural substance increased in the protected mice and was linked to better infection outcomes and when researchers gave 12-HHT directly to other young mice, it helped reduce lung damage and viral levels. It also increased two important immune regulators: plasmacytoid dendritic cells (dendron; tree) and regulatory T cells (Tregs). These cells directly coordinate immune activity and prevent excessive inflammation. Perhaps most importantly, mice that received the early-life synbiotic treatment showed lasting immune benefits into adulthood, including reduced susceptibility to experimental allergic airway disease.

This research highlights how important early gut development is for lifelong health. The findings demonstrate that B. infantis and HMOs work together to help establish a balanced immune system during a critical window of development and the results provide exciting evidence that providing early nutrition closer to human breast milk helps prepare the immune system to encounter future challenges.