Activation of microglia (microgliosis) coincides with focal axonal swellings in B6. APBTgmice. Little to no microgliosis (as judged by an increase in AIF1, red) was observed in B6.APBTg mice at 4 months but significant levels of microgliosis were observed in multiple brain regions at 8 months of age (arrowhead). Images taken from a region of the hippocampus as an example. AIF1 (allograft inducible factor, formerly IBA1) is a marker of microglia. Occasionally, this coincided with localized regions of axonal swellings (arrow, visualized using neurofilament, NFL, green). DAPI was used to identify nuclei. Scale bars = 50 μm.