Figure 1.
Distribution of TLR4 transcripts in the mouse brain. A full-length 35S-labeled mouse TLR4 antisense riboprobe was hybridized to tissue sections singly (a-j) or in combination with antibodies (k-o) or a nonradioactive riboprobe (p-q). Dark-field image shows TLR4 mRNA expression in a spleen section from C3H/HeOuJ mice (a) and not in C57BL/10ScCr spleen (b). Insets are bright-field images. Dark-field image (d) corresponds to the brain area outlined in a Nissl-stained section (c). Circumventricular organs, SFO (e), ME (f), and AP (g) show TLR4 expression when viewed in dark field (e′-g′). Similarly, cells in choroid plexus (h, i), ventricular ependyma (j), and meninges (k) express TLR4 mRNA. Hybridization with radioactive TLR4 cRNA was followed by immunohistochemistry with NeuN (l, m) or a vascular marker isolectin B4 (k, n, o). Inset (k) shows a low-power dark-field view of TLR4 mRNA in the meninges over cortex (arrowhead). Radioactive TLR4 mRNA (silver grains in the dark-field image, p) overlapped with a nonradioactive CX3CR1 label (purple cells in p′). Magnified bright-field view (q) and inset showing one double-labeled cell. TLR4 mRNA also colocalized with Iba1-positive microglial cells (r, magnified in r′), but not with GFAP-labeled astrocytes (s). LV, Lateral ventricle; ChPlx, choroid plexus; PVN, paraventricular nucleus; 3V, third ventricle. Scale bars: a, b, d, 1 mm; e-h, 0.5 mm; i-o, 0.05 mm; p, q, r, 0.05 mm.