MAPT and Alzheimer disease: These combined findings have revealed a complex temporal and functional involvement of microglia in AD risk and progression: while neuroprotective roles of microglia in limiting Aβ build-up may act in presymptomatic AD (Wang et al. 2015; Zhao et al. 2018), once in motion the disease course may be accelerated by microglial-mediated spreading of tau pathology and synapse loss (Asai et al. 2015; Hong et al. 2016; Hansen et al. 2018).