KGF treatment increases thymic cellularity and intrathymic IL-7 expression in kl/kl mice. wt littermates (2 weeks old, n = 5) or kl/kl mice (2 weeks old, n = 12) were treated with PBS or KGF for 3 days, and the thymic cellularity was analyzed on day 31. (A) The total thymic cellularity and (B) the absolute numbers of TN, DP, CD4 SP, and CD8 SP thymic subpopulations are shown; results are ± SD. The fold increase of the number of thymocyte subsets is shown in parenthesis. *P < .05, PBS versus KGF.