T Cells Are Required for Intestinal Inflammation in R23FR Mice. (A) Representative H&E stained sections from R23FR, R23FR/Rag−/−, R23FR/Mu−/− and R23FR/Tcrd−/− mice at d56. Scale bars, 100 μm. (B) Histological scores of the colon and cecum of R23FR, R23FR/Rag−/−, R23FR/Mu−/− and R23FR/Tcrd−/− mice at d56. Notice that disease was completely absent in R23FR/Rag−/− mice but not in R23FR/Mu−/− and R23FR/Tcrd−/− mice. (C) Schematic representation depicts experimental design for cell depletion experiments. (D) Representative H&E-stained colon and cecum sections (left) and histological scores (right) of R23FR mice after treatment with anti-CD4 and anti-CD8 antibodies. Depletion of CD4+, but not CD8+ T cells significantly reduced disease severity. Scale bars, 100 μm. **p<0.01, *** p<0.001, ns, not significant; by nonparametric Mann-Whitney test.