Short-term IL-7 administration does not alter thymic phenotype or function. Mice treated with rmIL-7 (5 μg per day for 14 days) or diluent were analyzed for thymocyte number (A), total intrathymic TRECs (B), and distribution of thymocyte subsets (C). (D) Lin^- thymocytes (CD3, CD4, CD8, B220, IgM, Mac-1, pan-NK, and Gr-1 negative) were analyzed for CD44 and CD25 expression that defines the DN1 through DN4 subpopulations. Data shown in graphs A through D are data from a single experiment, representative of 2 experiments carried out, showing the mean plus or minus SD of 3 mice per group. (E) Patterns of thymocyte maturation markers within each thymocyte subset were analyzed in IL-7-treated (dashed line) and diluent-treated (solid line) mice. Shown are representative data from 3 separate experiments. (F) The kinetics of thymocyte development was determined in IL-7- and diluent-treated mice by continuous oral administration of BrdU (“Materials and methods”). At the indicated time points, the percentage of thymocyte subset populations incorporating BrdU was determined. Shown are data from a single experiment, representative of 2 experiments carried out, with the mean plus or minus SD of 3 mice per group.