New study finds gut immune cells travel to brain, influencing Alzheimer’s progression.
Alzheimer’s disease continues to puzzle doctors and researchers, but new work is offering a different way of thinking about how the illness develops and how it might be treated in the future. A team at the Buck Institute for Research on Aging has found that immune cells living in the gut may have an important role in how the brain responds to Alzheimer’s. Their study, published in Cell Reports on August 29, 2025, shows that some of these gut immune cells are able to move to the brain, where they may influence inflammation and possibly even the progression of the disease. The findings also suggest that diet, especially one rich in fiber, could affect this process.
The gut is the body’s largest immune organ, containing a wide variety of cells that usually protect against harmful bacteria and keep digestion in balance. In this study, researchers looked at mice bred to develop Alzheimer’s. They discovered that a certain type of immune cell, called B cells, which normally help maintain balance in the gut, was reduced in the Alzheimer’s mice. Even more striking was the discovery that some of these cells had left the gut and traveled to the brain, settling in a border region known as the meningeal dura mater. These gut-derived immune cells were found to recognize bacteria from the intestines, raising the possibility that the gut and brain were communicating in unexpected ways.
To understand why this movement was happening, the scientists studied how the brain might be calling these cells in. They found that inflammatory cells in the brain of the Alzheimer’s mice were producing a chemical signal that acted like a beacon, encouraging the gut cells to migrate. Similar patterns were later confirmed in human data from past studies, making the discovery even more compelling. The team went further by using a drug to block this signal in the mice, which gave evidence that this “gut-brain axis” could be manipulated.
Alongside these immune system findings, the researchers tested whether diet might help restore balance. They fed some of the mice a fiber-rich substance known as inulin. The results were promising: the gut B cells returned, and the mice showed less frailty, including fewer tremors. Inulin produces short-chain fatty acids when broken down, which not only improve gut health but also travel through the body to influence other organs, including the brain. By lowering inflammation and improving gut balance, the fiber seemed to provide benefits that went beyond digestion.
The team also noted that while the fiber did not consistently reduce brain plaques—the sticky deposits often linked with Alzheimer’s—it did improve overall well-being. The mice lived healthier, with better scores on several measures of aging. This suggests that even if diet cannot erase the disease, it may still help extend quality of life. One of the researchers emphasized that the findings support long-standing advice about eating more fruits and vegetables, not just for general health but possibly for brain resilience as well.
The bigger question is whether these changes in the gut immune system are simply a reaction to brain damage caused by Alzheimer’s or whether they help drive the disease in the first place. Some researchers believe the initial signals may be protective, but over time the constant strain weakens the gut, allowing harmful bacteria to grow and increasing inflammation throughout the body. If that is true, intervening early might prevent or slow the disease process.
Future work will focus on whether specific gut bacteria can be tied to higher risks for Alzheimer’s or other brain conditions like Parkinson’s and multiple sclerosis. If certain bacteria are linked to increased inflammation, then treatments could be designed to block those signals before they cause harm. The study’s lead postdoctoral fellow expressed hope that early interventions, whether through diet, drugs, or microbiome adjustments, could eventually change the course of the disease.
For now, the discovery adds another piece to the Alzheimer’s puzzle, connecting the gut and brain in a way that few expected. It also highlights the importance of everyday choices, such as eating more fiber, which might have more far-reaching effects than once imagined.
Sources:
Alzheimer’s research uncovers a new therapeutic pathway for the memory-robbing malady
Amyloid-β-driven Alzheimer’s disease reshapes the colonic immune system in mice
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