TREM2 and Alzheimer disease: TREM2 expression level is enhanced in AD. Changes in TREM2 glycosylation likely impact its ligand binding properties. The patterns of TREM2's glycosylation can influence the cell signaling functions of TREM2. TREM2 is an important immune receptor expressed on microglia and other myeloid cells in the brain. Alterations in TREM2 glycosylation likely lead to the disruption of key immune functions mediated by TREM2. This could trigger excessive brain inflammation, which is a hallmark of PD pathology.