The goal of this study is to quantify the expression level of the three TREM2 transcripts in AD and control brains, to determine whether there is differential expression of TREM2 in the three groups, sporadic-AD cases (cases), AD-TREM2 (TREM2-carriers) carriers and controls (controls) and finally to determine whether these differences are due to the differential expression of a particular TREM2 isoform. Here, TREM2 is linked to Alzheimer disease.