Blood cells replace the immune cells of the ageing human brain

02 September 2026

At birth, the brain contains its own immune cells, called microglia, that are thought to persist throughout life without being replaced by cells from outside the brain. Studies that trace cell lineage now show that these cells are replaced by circulating immune cells during ageing, revealing a previously unappreciated interaction between the brain and the rest of the body.

This is a summary of: Belk, J. A. et al. Somatic mutations reveal the ontogeny of microglia in human ageing. Nature https://doi.org/10.1038/s41586-026-10939-0 (2026).

doi: https://doi.org/10.1038/d41586-026-02694-z‘Expert opinion’ is published under a CC BY 4.0 licence.

ReferencesGinhoux, F. et al. Science 330, 841–845 (2010).Article