TREM2 and Alzheimer disease: A decade of GWAS projects for Alzheimer’s disease has provided key and initially surprising insights into the progression of late-onset Alzheimer’s disease, particularly the dependence on the innate immune system, with the identification of genes such as TREM2 and SPI1/PU.1 (Guerreiro et al., 2013; Jonsson et al., 2013; Huang et al., 2017; Sims et al., 2017).