Interestingly, among female APOE-ε4 carriers with AD, the rs1921622 A allele was associated with increased expression of these microglial activation genes—specifically, increased transcript levels of CD74, APOE and TREM2 in microglia as well as an increased proportion of TMEM163+ microglia (Fig. 6g). This evidence concerns the gene TREM2 and Alzheimer disease.