Localization of presenilins in human control brain. Sections of the prefrontal cortex (A, C, and E) and hippocampus (F) from neurologically normal controls immunostained with affinity-purified anti-PS2 anti serum (NT14; A) or with anti-PS1 monoclonal antibody NT1 (C) or polyclonal antibody P1 (E, F) showed very uniform and consistent patterns of immunolabeling within the cell body and proximal dendrites of most neuronal pyramids. Levels of presenilin 2 (PS2) immunoreactivity in most Purkinje cells of the cerebellum were very high (B; affinity-purified NT14). In contrast to cortical neurons, levels of presenilin 1 (PS1) immunolabeling were low in Purkinje cells (D; NT1 labeling shown). Insets show higher magnification of the same brain regions using the same antibodies. Immunolabeling of sporadic Alzheimer’s disease (AD) brain was similar. The tissue shown was stored in formalin approximately three months. PS1 immunolabeling using either antibody was preserved upon much longer storage periods (>3 years), although NT14 immunoreactivity declined.