In Alzheimer's disease (AD), there is a strong genetic rationale for immune dysfunction to increase risk for dementia (e.g., CR1, MS4A, PLCG2, ABI3, and TREM2) (Efthymiou & Goate, 2017; Guerreiro, Bras, & Hardy, 2013; Jansen et al., 2019; Kunkle et al., 2019). Here, TREM2 is linked to Alzheimer disease.