TREM2 and Alzheimer disease: The recent discovery of a genetic link between AD and variants of the triggering receptor expressed on myeloid cells 2 (TREM2; TREML2) gene (Guerreiro et al., 2013; Jonsson et al., 2013), which is selectively expressed on microglia in the CNS (Lue et al., 2015; Takahashi et al., 2005), has reignited the interest in identifying biomarkers of glial activation (see poster).