Cell-cycle analysis of CD34⁺ progenitors incubated with soluble TGF-β1 or anti–TGF-β antibody.

After 48 hours of incubation, CD34⁺ cells isolated from UCB were collected, fixed, permeabilized, and stained with Ki67-FITC. Cells were then stained with 7-AAD overnight before acquisition analysis by FACS Calibur flow cytometry. Controls for the G₀ population were peripheral blood T cells starved overnight in serum-free medium. Controls for the cycling cell population were peripheral blood T cells stimulated with PHA and IL-2 overnight. White bars indicate cells incubated with the cytokines IL-3, IL-6, and SCF alone. Black bars indicate cells incubated in the same cytokine mixture with addition of soluble TGF-β1. Gray bars indicate cells incubated in the same cytokine mixture with addition of anti–TGF-β–neutralizing antibody. *P < .05.