APP and Brain atrophy: 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.