Figure 4.
Effect of amyloid β peptide (Aβ) antigen retrieval (AR) by the proteinase K digestion (P), EDTA autoclaving (A), and formic acid (FA) treatment (F) (in that order; referred to as “PAF”) method over that by the FA method. (A, B) In immunohistochemistry (IHC) with the 4702 antibody, Aβ loads (%) measured in the fusiform cortex of each case from the aged human brains (A) or in the hippocampus of each from the amyloid precursor protein–Swedish/London (APP-SL) mice (B) following the PAF method were plotted against those following the FA method. Significant correlations between the two AR methods were verified both in the aged human brains (Spearman rank correlation coefficient, r s=0.92; p=9 × 10−69) and in the mouse brains (r s=0.80; p=0.003). (C, D) The effect of Aβ AR by the PAF method was significantly higher than that by the FA method both in the aged human and in the mouse brains. In IHC with the 4702 antibody, Aβ-loaded areas measured following the PAF method compared with those following the FA method (set at 1.00; the dotted lines) were 1.59-fold at the 25th percentile, 1.86-fold at the 50th percentile, and 2.31-fold at the 75th percentile in the aged human brains (C) and 3.78-fold at the 25th percentile, 4.64-fold at the 50th percentile, and 12.32-fold at the 75th percentile in the mouse brains (D). (C) Ten (≥3.39) and (D) one (92.79) outliers are not shown. **p=2 × 10−28, *p=0.01; analyzed by Wilcoxon signed-rank test. n=162 from 54 individuals where three regions per case examined (A, C), and n=11 (B, D).