The association between tau aggregation and microglia in frontotemporal lobar dementia

Background Frontotemporal lobar degeneration (FTLD) describes a neurodegenerative disorder caused by protein accumulation in the brain, with the most common form due to aggregated Tau (FTLD‐tau). A potential role for neuroinflammation in FTLD has been highlighted by the discovery of genetic risk variants related to innate/adaptive immunity. Furthermore, studies have shown increased microglial and astrocyte activation together with T cell infiltration in the brain of a mouse tauopathy model (THY‐Tau22). Methods To test the possible neuro‐immune interactions in human FTLD‐tau, we obtained FFPE brain tissue from 12 FTLD‐MAPT, 33 Pick’s Disease (PiD) and 45 Progressive Supranuclear Palsy (PSP) patients, as well as 55 controls. Using immunohistochemistry we assessed the tau pathology across diseases using antibodies against several sites of tau phosphorylation in association with phenotypic markers of microglia and T cells. Results Our results show that PiD, PSP and FTLD‐MAPT patients had significantly higher phosphorylated tau protein loads (AT8: p