APP and Alzheimer disease: On the other hand, the three mentioned above APP-Tg mouse strains, 5xFAD, APPSwe/PS1dE9, and Tg-SwDI, do not contain human tau gene with the P301L mutation present in 3xTg-AD mice (Oddo et al., 2003), and whether or not the presence of human tau in 3xTg-AD brain plays a role in the spleen enlargement is still being discussed.