TREM2 and Alzheimer disease: While the Aβ peptide-clearing mechanisms are highly complex, one particularly important molecular sensor for Aβ42 peptide clearance is the triggering receptor expressed in myeloid/microglial cells 2 (TREM2; encoded at chr6p21.1), a variably glycosylated 230 amino acid transmembrane spanning stimulatory receptor of the immunoglobulin/lectin-like gene superfamily strongly associated with innate-immune, pro-inflammatory, and neurodegenerative signaling in AD.