PHF1 and Alzheimer disease: Retinal IHC analysis, using the PHF-1 antibody recognizing pS396- and pS404-tau in paired helical filaments, was performed on a subset of patient donors with MCI (n = 5, mean age 89.8 ± 5.8 years, 3 females/2 males), AD (n = 10, mean age 88.1 ± 7.4 years, 5 females/5 males), and NC controls (n = 9, mean age 82.2 ± 7.9 years, 3 females/6 males) (Fig. 6).