PHF1 and Alzheimer disease: The PHF-1 antibody (tau phosphorylated at S396/S404) showed barely any immunoreactivity in control brain and a significant increase in AD brains compared to controls (Fig. 4e; p < 0.05), although weak PHF-1 immunoreactivity can be observed in control brain tissue in high intensity blots (Additional file 1: Figure S1b).