Blocking blood-borne T cells reverses age-related memory decline in mice

A mouse study finds aging CD8+ T cells circulating in the blood promote cognitive ageing by secreting an enzyme that inflames the brain and impairs regeneration; blocking their blood-borne effects improved memory and learning in old mice, suggesting a practical blood-targeted approach to mitigate age-related cognitive decline. Parabiosis and cell-transfer experiments indicate these non-infiltrating T cells drive ageing, and aged cells can dampen memory-related gene expression in young brains.