Figure 6.

KPβ stimulates the proliferation of CD34⁺ hematopoietic progenitor cells. CD34⁺ human hematopoietic cells were isolated from cord blood and transduced with lentiviral particles encoding the indicated KPβ construct or GFP. Cells were grown for 14 days in the absence of cytokines (A) or in the presence of a cytokine cocktail containing thrombopoietin, stem cell factor, FLT3-ligand and interleukin-6 (B). Viable cells were counted in the presence of trypan blue. One representative experiment is shown. At the end of the experiment, cells that had been cultured without cytokines were permeabilized and stained with anti-PDGFRβ (C) or anti-phospho-STAT5 (D) antibodies and analyzed by flow cytometry.