# Stanford Study: Immune Cells Flood into the Aging Brain New discovery opens doors for understanding brain aging and treating neurological diseases. - **Source:** [Latest Science News -- ScienceDaily](https://brifing.si/source/0eef8637-6c5b-4e79-8f5b-6c9c6b36cf16) - **Published:** 2026-08-14 - **Original article:** - **On Brifing:** https://brifing.si/s/d4646ef0-a1c5-4659-93de-a58fef0bbb3f ## Redefining the Brain's Immune System Researchers at Stanford University discovered that immune cells from other parts of the body enter the brain during aging. This finding shows that the brain's immune system is far more dynamic than previously thought. The brain was considered an isolated system with its own specialized immune cells and the blood-brain barrier. However, the new research fundamentally changes this view. ## Origins and Foundations of the Research The research was led by Julia Belk, a postdoctoral researcher in pathology at Stanford Medicine. Belk adopted an interdisciplinary approach combining computer science and medicine. Previous studies observed that mutated blood stem cells reduced the risk of Alzheimer's. This observation strengthened the idea that immune cells interact with the brain. ## Genetic Analysis and Findings Researchers analyzed genetic information from thousands of individuals and identified that certain immune cell clones had a protective effect against Alzheimer's. They deepened their studies on whether these cells could enter the brain. Evidence showed that immune cells produced by blood stem cells could migrate into the brain. ## Aging and Immune Cells During aging, blood stem cells in the bone marrow continuously renew immune cells. However, it was thought that immune cells in the brain renewed themselves. The new research reveals that these cells also receive external support. This finding offers a new perspective on how brain immunity changes with age. ## Link Between Alzheimer's and Immune Cells The idea that blood-derived immune cells could play a protective role against Alzheimer's sparked debates in the scientific community. In 2022, researchers supported by the Knight Initiative for Brain Resilience began testing this hypothesis. They investigated how immune cells providing resilience against Alzheimer's reached the brain. ## Comparison of Brain Tissue and Blood Samples Researchers examined brain tissue and blood samples from Stanford Rapid Autopsy Center and the University of Washington's Alzheimer's Disease Sequencing Project. These samples were used to determine the origin of immune cells. DNA analysis compared genetic similarities between cells in the blood and brain. ## Genetic Traces and Cell Origin Researchers used DNA mutations to determine the origin of immune cells. Mutations accumulated in blood stem cells with age are passed on to immune cells. If cells in the brain and blood carry the same mutations, it is concluded that they share the same origin. This method proved that cells in the brain were blood-derived. ## Implications and Future Directions This discovery opens new approaches for understanding brain aging and treating neurological diseases. The ability of immune cells to migrate into the brain offers potential pathways for preventing or treating diseases like Alzheimer's. The research sheds light on redefining the brain's immune system and future treatment strategies. ## Sources covering this story - https://www.sciencedaily.com/releases/2026/08/260814011033.htm — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._