CD8+ T cells are increased in the subventricular zone with physiological and pathological aging.

Age-related cognitive decline and neurodegenerative diseases are associated with less functional neurogenic niches. It has been recently shown that aged subventricular zone (SVZ) suffers an infiltration of T cells, which affects neural stem cell activity in mice. Whether this occurs in human neurogenic niches or to which extent T-cell infiltration is also taking place in neurodegenerative diseases remains unknown. In this work, we studied the presence of T cells in both human neurogenic niches in young and old individuals. There was a significant increase in the number of CD3+ and CD8+ T cells in the SVZ of elderly individuals, which was not detected in the dentate gyrus. Moreover, we also found CD3+ and CD8+ T cells in the SVZ of individuals with neurodegenerative diseases. However, T-cell count was similar when compared non-neuropathological elderly with disease diagnosed patients. Our study reveals the infiltration of T cells in old human brains, particularly in the SVZ under non-pathological conditions and also in neurodegenerative contexts.