IL-27 enhances the differentiation of CD34⁻KSL HSCs. Mouse CD34⁻KSL cells (40 cells/well) were cultured in serum-free medium supplemented with 0.5% BSA and SCF (10 ng/mL) in the presence or absence of IL-27 (10 ng/mL) in triplicate. On days 7, 14, and 21, cell growth was monitored using a light microscopy (A left panels), and number of cells per well was counted and images were acquired under an inverted microscope (Leica DB IRBE) or standard trypan blue exclusion method (A-E right panels). Expanded cells also were stained with various combinations of antibodies and analyzed by flow cytometry (B-E left panels). Numbers represent the percentage of cells in each box or area. Data are shown as the mean (± SD). Mouse CD34⁻KSL cells (40 cells/well) were cultured under myeloid conditions in medium supplemented with 10% FCS, SCF (10 ng/mL), TPO (10 ng/mL), IL-3 (10 ng/mL), and EPO (1 U/mL) in the presence or absence of IL-27 (10 ng/mL) in triplicate. On days 7 and 10, number of cells per well was counted under an inverted microscope (F). Cells also were stained with various combinations of antibodies and analyzed by flow cytometry (G). Data are shown as the mean (± SD). * indicates P less than .05, compared with controls.