Photomicrographs of hippocampal tissue sections from an individual with Braak NFT stage II (a – e, a1 – e1) and an individual with Braak NFT stage VI (f – j, f1 – j1) immunohistochemically processed using antibodies directed against the p-tau 262 epitope of the tau protein (a, a1, f, f1), the p-tau 356 epitope (b, b1, g, g1), the p-tau 231 epitope (clone AT180; c, c1, h, h1) and the p-tau 202/205 epitope (clone AT8; d, d1, i, i1). The pan-amyloid binding dye X-34 was used to confirm the presence of fibrillar tau (e, e1, j, j1). Immunolabeling and histofluorescence observed in the CA1 region, near the CA1/CA2 border, are illustrated at low (a – e, f – j) and higher (a1 – e1, f1 – j1) magnification. The locations of the higher-magnification images are indicated by dashed outlines in the low-magnification images. The illustrated immunohistochemical staining was replicated in three sections per individual in each of three individuals with Braak II and five individuals with Braak VI. In summary, the p-tau 262 and p-tau 356 immunostaining is localized mainly to granular structures inside hippocampal neurons, whereas the p-tau 231 and p-tau 202/205 antibodies show a more diffuse pattern of immunolabeling in hippocampal neurons, and in neuropil threads, at both Braak II and VI NFT stages.
