Figure 4: TLR3 mediates radiation-induced crypt cell death through the TRIF–RIP1 pathway.

(a) TUNEL-staining of the small intestinal crypts of Trif^−/−, Irf3^−/− and Ifnar^−/− mice 6 h after TBI and isologous BMT. TUNEL-stained epithelium shows green fluorescence. Nuclei were stained with DAPI (blue). Scale bar, 100 μm. The right-hand panel shows numbers of TUNEL-positive cells. n=3–4; results are means±s.e.m. **P<0.01 (unpaired two-tailed Student’s t-test). (b) H&E staining of the small intestinal crypts of Trif^−/−, Irf3^−/− and Ifnar^−/− mice at day 3. Scale bar, 100 μm. Asterisks denote microcolonies. The right-hand panel shows the numbers of microcolonies. n=3–5; results are means±s.e.m. **P<0.01 (unpaired two-tailed Student’s t-test). (c) TUNEL-staining of the small intestinal crypts of non-treated and Nec-1-treated mice 6 h after TBI and isologous BMT. TUNEL-stained epithelium shows green fluorescence. Nuclei were stained with DAPI (blue). Scale bar, 100 μm. The right-hand panel shows numbers of TUNEL-positive cells. n=5; results are means±s.e.m. **P<0.01 (unpaired two-tailed Student’s t-test). (d) H&E staining of the small intestinal crypts of non-treated and Nec-1-treated mice at day 3. Scale bar, 100 μm. Asterisks denote microcolonies. Right panel shows the numbers of microcolonies. n=5; results are means±s.e.m. **P<0.01 (unpaired two-tailed Student’s t-test). Results are representative of three independent experiments.