KGF inhibits the capacity of the thymic microenvironment to attract T-cell precursors. (A) Adult C57BL/6 mice were treated either with KGF (⊡) or HBSS (▪) as in Figure 1, and the numbers of ETPs (Lin⁻CD44⁺CD25⁻CD117^hi) were determined at the indicated days. (B) Time-lapse video microscopy recorded E14.5 fetal thymocytes that migrated toward (open bars) and then entered (filled bars) an alymphoid E14.5 fetal thymic lobe that had been pre-exposed for 24 hours to KGF (100 ng/mL, ⊡) or HBSS-supplemented medium (▪) before the start of the migration experiments. The graph depicts the numbers of cells that migrated in a directed fashion and that reached the thymic lobe. Statistical significance was evaluated individually for open bars (□) and filled bars. (C) Changes in chemokine expression following exposure to exogenous KGF. Chemokine mRNA levels were determined by quantitative reverse-transcription PCR qRT. The y-axis shows the relative transcript levels (the group with maximal chemokine expression was set as 100%, which is displayed as value of 1.0). Mean ± SD; *P < .05 versus HBSS controls in panel A, with 5 mice per group and time point. Mean ± SEM; *P < .01 versus HBSS controls in panel B where data are representative of 10 independent in vitro experiments.