Stanford researchers find blood-derived immune cells infiltrate aging human brains
A Stanford team discovered that immune cells from the bloodstream enter the human brain during middle age and become microglia, challenging the view that the brain is isolated from the body’s immune system.
Stanford scientists have demonstrated that, beginning in middle age, large numbers of blood-origin immune cells cross the blood-brain barrier and integrate into the human brain, where they differentiate into microglia. Researchers compared DNA mutations in immune cells from blood and from brain tissue obtained through the Stanford Rapid Autopsy Center and the University of Washington’s Alzheimer’s Disease Sequencing Project, establishing a genetic link between the two populations.
The work overturns the long-standing belief that brain microglia are a self-sustaining population established at birth. The discovery, supported in part by the Knight Initiative for Brain Resilience, opens the possibility of designing peripheral immune cells to combat amyloid and tau aggregates in Alzheimer’s disease. It also highlights a uniquely human aspect of brain aging that could reshape how scientists approach neuro-immune interactions. The results were reported in the journal Nature.
Why it matters
It reveals a human-specific immune pathway that could be targeted to prevent or treat brain diseases.
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