Figure 2

Expansion of CD34^-lineage^- cells in response to IL-15 plus IL-21. CD34^-lineage^- cells were maintained in liquid cultures with Flt3-L and SCF, in the presence of either IL-15, or IL-21 or the combination of both cytokines for up to 4 weeks. In order to monitor cell expansion in response to cytokine stimulation, cells were harvested weekly and counted. CD34⁺ cells isolated from the same UCB samples were used in control experiments. Panel A: Cultures were established with CD34^-lineage^- cells. The number of viable cells was counted using trypan blue exclusion. The bars depict mean and standard deviation recorded in 11 independent experiments performed with 11 different UCB samples. Panel B: Fold expansion of the CD34^-lineage^- cells after 4 weeks of culture with either of the cytokine combinations. The bars depict mean and standard deviation recorded in 11 independent experiments performed with 11 different UCB samples. Panel C: Fold expansion of UCB CD34⁺ cells after 4 weeks of culture with either of the cytokine combinations. The bars depict mean and standard deviation recorded in 5 independent experiments performed with 5 different UCB samples. Panel D: After 4 weeks of culture with IL-21 and IL-15, CD34^-lineage^- cells were harvested, stained with May-Grünwald-Giemsa and visualized under an AX70 optical microscope (Olympus, Tokyo, Japan) equipped with 100×/1.25 NA objective lens. Image acquisition was performed with an Optronics digital camera (Olympus) and ImagePro Plus software (Media Cybernetics, Silver Spring, MD).