For decades, the brain has been described as immunologically privileged: walled off behind the blood-brain barrier, patrolled by its own resident immune cells, and largely closed to the rest of the body. Stanford researchers now report that the aging human brain does not work that way.
Working with post-mortem brain tissue and matched blood samples, the team found that aging brings a large influx of immune cells from the blood into the brain, beginning as early as middle age, and that those peripheral cells then transform into specialized microglia. The findings were published in Nature on July 30 under the title "Somatic mutations reveal the ontogeny of microglia in human aging."
