TREM2 is a damage-response receptor expressed exclusively by myeloid cells including brain microglia.22 It has a preference for binding anionic lipids, notably Phosphatidyl-serine (PS)21,23–25 a membrane signal on apoptotic cells, notably neuronal synapses in AD.26 Other lipids reported to activate TREM2 include Phosphatidyl-ethanol (PE), Phosphatidyl-choline (PC), Phospholipids and Sphingolipids such as Ceramides (Cer) and Sphingomyelins (SM). Here, TREM2 is linked to Alzheimer disease.