Figure 1.

TLR2 gene expression in response to exogenous and endogenous Aβ. A solution containing either sterile saline (a) or synthetic Aβ_1–42 peptide (b) was injected into the hippocampus of CD1 mice. TLR2 mRNA expression was determined by in situ hybridization (agglomeration of silver grains) 6 h after the intracerebral infusion. c, TLR2 mRNA expression levels (as determined by optical density quantification) were significantly increased in areas distal to the injection site of Aβ_1–42-treated animals. *p < 0.05 (Student's t test; saline, n = 3; Aβ_1–42, n = 5). d, Tissue sections were stained with an antibody directed against iba1 to reveal microglia (brown cells) and hybridized with TLR2 mRNA probe. TLR2 mRNA signal always colocalized with iba1-immunoreactive cells surrounding the injection site (indicated with arrows). e, f, Activated microglia had also a positive signal for TLR2 transcript in the brain APP mice (iba1⁺/TLR2⁺). Scale bars: a, b, 500 μm; d–f, 20 μm. Error bars indicate SEM.