TREM2 and Alzheimer disease: Similarly, Trem2 homozygous (Trem2-/-) or heterozygous (Trem2+/-) deficient wildtype (WT) or AD mice also display multiple microglia pathologies, including reduced numbers of microglia, increased apoptotic cell death, nonreactive microglia cell morphology, the inability to coalesce around and compact beta amyloid plaques [32], abnormal AD gene expression signature [33], age-dependent inability to reduce total Aβ plaque load [34], and an inability to support Aβ antibody-mediated beta amyloid plaque clearance [35].