Midlife brings a major immune shiftThe clearest transition appeared in microglia, the immune cells that help maintain and protect the brain. In their place, researchers detected cells whose molecular profiles resembled immune cells circulating in the blood. Across several types of brain cells, researchers found that the genome’s three-dimensional structure became progressively less organized. The widespread erosion of that architecture suggests that declining genome organization may be a basic feature of brain aging. The results indicate that brain aging involves more than a slow accumulation of damage.