TGF-β1^−/− E14 FL cells show a defect in hematopoietic stem/progenitor cell compartment. (A) E14 FL cells (5 × 10⁴) from TGF-β1^+/+ and TGF-β1^−/− mice were plated in methylcellulose. Colonies were scored between 7 and 10 days in culture. The average ± SD of 5 experiments is shown (6 mice per experiment); *P < .05. (B) Analysis of LSK population in E14 FL from TGF-β1^+/+ and TGF-β1^−/− mice. The histograms are the average ± SD of 6 independent experiments; *P < .05. (C-F) Lethally irradiated hosts were injected with 4 dilutions of E14 TGF-β1^+/+ and TGF-β1^−/− FL cells: (C) 10 × 10⁶, (D) 5 × 10⁶, (E) 1 × 10⁶, and (F) 5 × 10⁵ male E14 FL cells (n = 5 mice per cell dose and per genotype). Recipients were monitored daily. Survival data were analyzed with the use of a log-rank nonparametric test, and the results are expressed as Kaplan-Meier survival curves.