CCE-25–c-Kit^negSca-1^pos and Sca-1^neg cell growth in “contact” M2-10B4 cocultures. Purified CCE-25–c-Kit^negSca-1^pos and Sca-1^neg cells were added to M2-10B4 monolayers and were cocultured for 25 days with biweekly feeding in the presence of 100 ng/mL SCF and 30 ng/mL IL-3. Cells were harvested and stained as described in “Materials and methods.” The bars represent the percentages of granulocytes (Gr-1), monocytic cells (Mac-1), and/or macrophages (F4/80), as well as c-Kit^pos cells as indicated, minus the background contributed by the isotype-matched controls. Left panel: CCE-25–c-Kit^pos cells were used as a positive control for growth. Middle panel: CCE-25–c-Kit^negSca-1^pos cells. Left panel: CCE-25–c-Kit^negSca-1^neg cells. For these analyses, background staining, indicated by staining with isotype-matched controls, was subtracted to yield the percentages shown. Values were calculated by averaging the data from 2 separate experiments. Error bars indicate the standard error between experiments. These data are representative of 3 wells per group per experiment in 3 experiments.