Adding to this evidence, a majority of recently identified AD risk genes discovered on genome wide association studies such as ABCA7, BIN1, CD33, CR1, INPP5D, MS4A6A, PLCG2SHIP1, and TREM2 are highly or exclusively expressed by macrophages and microglia [71,76,77,78,79]. This evidence concerns the gene TREM2 and Alzheimer disease.