Injection of anti–IL-7 MAb (M25) induces a partial reversal of the phenotypic abnormalities observed on early and late thymic development. After 10 injections of 1 mg anti–IL-7 MAb (M25) or its isotype control (CC57), 3 mice from each group were killed 2 to 3 days after the last injection. (A) Total thymocytes and DP counts in the groups injected with M25 and CC57, respectively. (B) Modification of CD4/CD8 profile percentages after anti–IL-7 MAb injection. (C) Appearance of DP cells with normal maturation markers. The shaded areas represent the marker of interest, and the open areas represent the negative control. The percentage of positive cells for each marker is shown. Increase of absolute numbers (D) and percentages (E) of the T-cell committed progenitors DN3 and DN4 after anti–IL-7 MAb injection compared with control group mice. Error bars indicate SEM. (F) Enhancement of DN1, DN2, and DN4 cell proliferation by Ki-67 IC staining after injection of anti–IL-7 MAb in one representative experiment. ⁺P < .05. The shaded histograms show the marker of interest; and the open histograms, the negative isotype controls. The number beneath each bracket represents the percentage of positive events.