Fig. 1

Characterization of mouse 1C9 anti-tau_2–18 monoclonal antibody. a Competition ELISA using peptides with Alanine substitution showed that 1C9 recognized epitope PRQEF comprising 4–8 amino acids of tau_2–18 peptide. The half maximal inhibitory concentration (IC₅₀) for each peptide is shown in Table. b 1C9 recognized full-length tau but not tau that lacks 2–18 domain in Western Blot. Lane 1- tauΔ2-18, lane 2-full-length tau. c 1C9 bound monomeric (spot 1), oligomeric (spot 2: cross-linked; spot 3: non-cross-linked) and fibrillar (spot 4) forms of recombinant tau protein in dot blot. d Anti-tau_2–18 mAb 1C9 bound to neuropil threads and neurofibrillary tangles in AD brains (Braak stage VI-C). No binding was observed with non-AD brain (Braak stage 0). Original magnification 40X, scale bar = 20 μm. e 1C9 bound different species of tau protein in brain homogenates from both AD cases and control subjects in denaturing conditions (lane 1: control 1; lane 2-control 2; lane 3-AD1; lane 4-AD2; lane 5-AD3) in Western Blot. f In non-denaturing conditions in Dot Blots 1C9 as well as commercial TNT-1 Ab specific to N-terminus of Tau selectively bound to soluble tau in AD brains but not in controls. Of note, HT7 and rabbit anti-tau-polyclonal Ab recognizing total tau, had bound tau in both control and AD brains