Science
Brain immune cells undergo major shift around age 50, study finds
Researchers found that resident brain immune cells begin declining at midlife and are replaced by inflammatory cells from the bloodstream.
The short version
- A study of postmortem human brain tissue revealed that protective resident immune cells in the hippocampus decline around age 50 and are replaced by inflammatory immune cells from the blood.
- The cellular shift, along with blood-brain barrier deterioration and gene activity changes, may help explain why neuroinflammation and neurodegenerative risks rise as people age.
- Because the replacement immune cells originate in the bloodstream, researchers suggest future therapies could potentially modify these cells to protect the brain against Alzheimer's without directly targeting central nervous system tissue.
- Future research aims to identify what triggers the influx of blood-derived immune cells and why the timing and extent of these changes vary among individuals.
Key facts
- Researchers from UC San Diego, New York Genome Center, and UC Irvine analyzed postmortem hippocampal tissue from 40 neurologically healthy adults aged 20 to 95.[Fox News]
- Around age 50, resident brain immune cells called microglia begin to decline and are increasingly replaced by inflammatory cells entering from the bloodstream.[Fox News]
- The study also observed deterioration in cells that maintain the blood-brain barrier, along with widespread changes in DNA and gene activity.[Fox News]
- The research was funded by the National Institutes of Health and published in the journal Science.[Fox News]
What remains uncertain
- The study cannot prove direct causation or confirm that these cellular changes cause cognitive decline, as it relied on postmortem tissue from different individuals rather than tracking individual subjects over time.[Fox News]
- It remains unknown what exact triggers cause blood-derived immune cells to enter the brain, or whether the observed findings apply across the entire brain beyond the studied hippocampus.[Fox News]