TREM2 and Alzheimer disease: 1. TREM2 activation was lower in AD microglia than in healthy subjects. 2. TREM2 activation is negatively correlated with AD.3. TREM2 controls microglial functions to mediate regulation of AD.4. In AD, activation of TREM2 may be associated with Th2-related pathways and microglial resistance.5. Regardless of R47H (rare variant TREM2 loss-of-function) TREM2 signal is low in microglia in AD.