(a) Time course of effect of anti-CD3 mAb on jejunal wt/l ratio. Mice were injected with 0.2 mg anti-CD3 mAb at time 0. Loop wt/l ratios were measured after varying times. Values are means ± SE for six determinations. (b) Effect of anti-TNF and anti–IFN-γ antibodies on jejunal wt/l ratios at 3 hours. Mice were injected simultaneously with 0.2 mg control or anti-CD3 mAb along with neutralizing mAb to TNF or IFN-γ. (c) Control or anti-CD3 mAb was injected in C57BL/6 or in TNFR-1 or IFN-γ knockout mice. Weight-to-length ratios were determined after 3 hours. Values are means ± SE for six determinations in each group. In all cases, *P < 0.05, **P < 0.01 by comparison using ANOVA. In (a), all comparisons were with 0-time control. In (b) and (c), control mAb-treated, anti–CD3-stimulated mice were initially compared with control mAb-treated, unstimulated controls. In (b), results in anti-TNF mAb and anti–IFN-γ–treated, anti–CD3-stimulated mice were compared with control mAb-treated, anti–CD3-stimulated mice. In (c), results in anti–CD3-stimulated TNFR-1^–/– and IFN-γ^–/– mice were compared with anti–CD3-stimulated B6 mice. The data indicate that TNF but not IFN-γ inhibition prevented anti–CD3-induced diarrhea.