Clonogenic capacity of CD34⁺Flt3^high versus CD34⁺Flt3^low marrow cell subpopulations. Cells were FACS sorted as shown in Fig 4 and plated at a density of 500 cells per culture dish in methylcellulose. Colonies were scored after 14 days of culture. (A) Colony formation from CD34⁺Flt3^high versus Flt3^lowcells. Data represent mean ± SD of triplicate cultures from three individual experiments. (B) Colony formation of CD34⁺lin⁻Flt3^high versus CD34⁺lin⁻Flt3^low cells. Data represent mean ± SD of triplicate cultures from one experiment. *P < .001; ** P < .004.