In light of the strong correlation between tau pathology and brain atrophy in AD, rather than Aβ,182 a comparison was made between the immune responses of amyloid-depositing APP/PS1-21 (A/PE4) and 5xFAD (5xE4) mice, versus P301S tau transgenic (TE4) mice expressing human APOE4.165 Interestingly, the number of T cells was significantly increased only in TE4 mice in regions where brain atrophy occurred, and this increase was positively correlated with the number of microglia. Here, APOE is linked to Brain atrophy.