TREM2 and Alzheimer disease: Wang et al. (Wang et al., 2015) were the first to report that Trem2 deficiency significantly decreased the number of plaque-associated microglia in the 5XFAD AD mouse model, indicating that the proliferation of local microglia around the plaques is impaired, which other groups later confirmed (Yuan et al., 2016; Fitz et al., 2020).