Inflammation in the small intestine of T reg cell–depleted SPF mice was more severe than in GF mice. (A) Representative histopathology of the small intestine of SPF and GF Foxp3^DTR mice 8 d after the start of the treatment with PBS or DT. Bars, 100 µm. (B) The cell numbers in the lamina propria of the small intestine in the indicated mice were determined by morphometry. (C) Analysis of the body weight of SPF and GF Foxp3^DTR mice treated with DT or PBS (control). The left panel shows changes in body weights between days 0 and 14 (n = 13 for each group). The right panel shows changes in body weights between days 0 and 28 (n = 4 for each group). Error bars represent SD. (D) Leukocytes isolated from the small intestinal lamina propria of the indicated mice were stimulated in vitro with anti-CD3 and anti-CD28 in the presence of monensin, and intracellular staining for the indicated cytokines was performed. The frequencies of cytokine-producing cells among CD4⁺Foxp3⁻ cells were determined by flow cytometric analysis. Absolute numbers of the cells are shown in Fig. S2. Data are representative of two independent experiments. (B and D) The horizontal lines indicate the mean ± SEM.