TLR9 is important for protection against mild, but not severe intestinal injury. TLR9-deficient mice were treated with 3% (A, C, E) or 1% (B, D, F) DSS in their drinking water for seven days, then supplied with regular drinking water for seven days. Wild type mice from the same experiment are depicted in Figure 1 for comparison. Mice were scored for the presence of occult blood (A, B) and stool consistency (C, D) on a daily basis during the fourteen day experiment as described in the materials and methods. (E, F) Mice were weighed on a daily basis to calculate the percent change in weight for the treatment (days 0–7) and recovery (days 7–14) periods. One of two experiments (5–6 mice per condition) with similar results shown. *** p < 0.001; Student’s t-test; n.s., not significant.