Apoptotic cells in sections of colonic tissues were detected by TUNEL assay. (A) Representative images of sections prepared from WT C57Bl/6 mice and from the inflamed colon of an IL-10-/- mouse; apoptotic nuclei are indicated by black arrows, 20X (B). Representative images demonstrating the presence of apoptotic nuclei in sections from TLR4-/- and TLR4-/- x IL-10-/- (DKO, black arrows) mice maintained under SPF conditions and their reduction in mice that have been rederived Hpp free. (C) Graphic representation of TdT+ cells/1mm2 high power field (HPF) enumerated from sections of colonic tissue of each line. 30 fields were counted for each section prepared from C57Bl6/WT (n=4), Hpp free TLR4-/- (n=3), SPF TLR4-/- (n=3), Hpp free TLR4-/- x IL-10-/- (n=4), SPF TLR4-/- x IL-10-/- (n=5) and SPF IL-10-/- (n=6). ** p < 0.01.