To investigate whether there is any influence of plasma protein in the periphery on protein expression in the brain parenchyma, the cellular location of TREM2, tau, ApoE, and Aβ42 was examined by immunofluorescence staining on postmortem brains sections from the superior frontal cortex (SFC), hippocampus (HP), and mid temporal cortex (MTC) of AD, DS, and age-matched controls (n = 10 in each group: aged between 46 to 76 years, Supplementary Table 1). This evidence concerns the gene APOE and Alzheimer disease.