Plaque-associated microglial phosphotyrosine immunoreactivity increased with age in APP/PS1 mice. (A) Serial coronal sections from 2- , 4- , 6- and 12-month-old controls (C57BL/6) and age-matched transgenic animals (APP/PS1) (n = 5 to 6) were immunostained with anti-phosphotyrosine antibody (4G10). Representative select high magnification fields from the temporal cortex of hemisections are presented. (B) To validate microglial co-localization of phospho-tyrosine immunoreactivity, 12-month APP/PS1 sections were double-labeled using anti-phosphotyrosine antibodies and VIP as the chromogen (black arrows) and anti-CD68 or Iba1 and Vector Blue as the chromogen (green arrows). Double-labeled cells are indicated with yellow arrows. (C) To quantify immunoreactivity and omit the inclusion of non-microglial phosphotyrosine immunoreactivity, 4G10 positive plaques from APP/PS1 mice were counted from the temporal cortex and averaged and graphed (+/−SEM) for *P <0.001 from two-month APP/PS1 mice, #
P <0.001 from two-month and four-month APP/PS1 animals, $
P <0.001 from four- and six-month APP/PS1 animals.