TREM2 and Alzheimer disease: The evidence that sTREM2 levels are increased in the cerebrospinal fluid and CNS of AD patients suggest that the processing of TREM2 by α-secretase is linked to AD (Heslegrave et al, 2016; Lichtenthaler et al, 2022; Piccio et al, 2016; Suárez-Calvet et al, 2019).