Our immune system loses control over our gut microbiome we age

Researchers from the Leibniz Institute for Age Research and the University of Jena have hypothesized that immune surveillance plays a key role in maintaining the balance of the microbiome. They believe that age-related changes in the microbiome are not primarily due to the behavior of the microbes themselves, but rather to the gradual deterioration of this surveillance mechanism.

The authors compare the functioning of immune surveillance to how the body fights cancer cells, identifying and suppressing those elements that become uncontrollably abundant. In the gut, this surveillance probably doesn’t target specific types of microbes, but rather ensures that none of them gain an excessive advantage. This helps maintain the diversity and stability of the microbial community.

To illustrate their idea, the scientists created a computer model. In this model, different types of bacteria compete for space. If a rule is implemented that limits the most aggressive and fast-growing bacteria, the community remains diverse and stable. However, if the control is weakened, one species becomes dominant, and the overall diversity decreases.

As we age, our immune system changes in a non-uniform way: some inflammatory responses persist or even intensify, while subtle regulatory mechanisms weaken. Researchers suggest that it is the ability to recognize and contain overactive strains that is primarily affected. This leads to a paradoxical situation: while the overall immune response to microbial populations may be excessive, the ability to target specific cells is compromised. This results in the chronic, low-grade inflammation commonly associated with aging, as well as an imbalance in the microbiome.

The hypothesis has practical implications for the development of therapies. If it is correct, simply changing the composition of intestinal bacteria may not be enough: it is important to simultaneously strengthen those parts of the immune system that are responsible for maintaining balance. This is especially relevant for people with weakened immune systems, where the connection between the state of the immune system and the microbiome is particularly noticeable.

To test the theory, scientists suggest starting with research on short-lived model organisms, such as the African killifish, which is often used in gerontology. In addition, long-term observations of people are necessary: it is important to see whether the weakening of immune surveillance really precedes changes in the microbiome, rather than following them.

If the hypothesis is confirmed, it will change the approach to the prevention of age-related disorders. The stability of the intestinal microbiome will not be so much a property of the bacteria themselves, but rather the result of a constant interaction with the immune system, the control of which is gradually lost over the years. New knowledge can form the basis of strategies aimed at healthy aging and the prevention of age-related diseases.