TREM2 and Alzheimer disease: The importance of inflammatory pathways affecting the function of microglia for the pathogenesis of AD is highlighted by the results of genome-wide association studies (GWAS), where many of the implicated genes have a major role in immunological processes, as well as the recent linkage to AD of a rare variant of TREM2, a gene that regulates phagocytosis and the activation state of microglia/macrophages [5,6].