Figure 3.
Chronic treatment with the endotoxin LPS increases the innate immune response and neurodegeneration in SOD1G37R mice. The bright-field (B.F.) and dark-field photomicrographs depict representative examples of the hybridization signal for TNF-α (B), IL-12 (C), and TLR2 (D) mRNA in the reticular formation just above the olivary complex. It is of interest to note that the hybridization signal for IL-12 and TLR2 overlaps with the fluorochrome FJB (C, D;vs E), used here as a marker of neuronal death. Degenerating axons were labeled by FJB staining in the reticular formation; DAPI-positive nuclei were essentially devoid of FJB signal in this structure (F). The bottom panels in G depict examples of microglial cells containing positive hybridization signal for TLR2 mRNA in the reticular formation. Cells of myeloid origin were labeled by immunoperoxidase using antisera directed against iba1 (brown immunoreactive cells). TLR2 mRNA was thereafter hybridized on the same sections by means of a radioactive in situ hybridization technique (silver grains). Note the presence of the mRNA encoding TLR2 within parenchymal microglia (agglomeration of silver grains within the cell cytoplasm) (black arrowheads). Scale bars: A-E, 500 μm; F, G, 50 μm. See the legend to Figure 2 for definitions of abbreviations.