Several other studies have reported a reduction in microglial density and/or other indices of their reactivity in animals lacking TREM2 (Zhu et al., 2015; Cantoni et al., 2015; Poliani et al., 2015) with less activated microglia observed upon cuprizone-induced demyelination (Cantoni et al., 2015) and in amyloidopathy and tauopathy models (Leyns et al., 2017; Vautheny et al., 2021; Meilandt et al., 2020), although the consequences of this may vary according to disease phase and context. This evidence concerns the gene TREM2 and tauopathy.