Premature thymic involution in kl/kl mice is related to disruption of thymic microenvironmental organization, which is restored by KGF. (A) The intrathymic levels of EVA, an epithelial cell–specific marker, and IL-7 transcripts in wt littermates or kl/kl mice (2 weeks old, n = 5 per group) were analyzed by quantitative RT-PCR on day 8 after initiation of PBS or KGF treatment. Each transcript level was normalized to β-actin expression. *P < .05; NS indicates not significant. (B)Thymic architecture of wt and kl/kl mice was compared 1 month after PBS or KGF treatment by H&E staining and immunofluorescence staining of K8, K5, and DAPI for nuclear staining. Arrows indicate cysts observed in the kl/kl thymus. The magnification was 100 × for H&E staining and 200 × for immunofluorescence staining.