PHF1 and Alzheimer disease: In the present study forebrain sections from male and female 3-week, 2–4, 5-6, 8-9, and 18–20-month-old 3xTg-AD and age-matched ntg mice were immunostained using well-characterized antibodies directed against 6E10, tau conformational epitopes (Alz50 and MC1), and phosphotau epitopes AT180 (phosphothreonine 231), AT8 (phosphoserine 202/205), and PHF-1 (phosphoserine 396/404).