For example, the triggering receptor expressed on myeloid cells 2 (TREM2) and apolipoprotein E (APOE) are major genetic risk factors for sporadic AD that are expressed by plaque-associated microglia and involved in Αβ clearance (Bradshaw et al., 2013; Castellano et al., 2011; Kleinberger et al., 2014; Parhizkar et al., 2019; Reddy et al., 2009; Wang et al., 2015). Here, TREM2 is linked to Alzheimer disease.