Fig. 3. Effect of TPO on cell survival in clones with low levels of Mpl expression on their cell surface. Cells were washed three times and left deprived of cytokines or stimulated with 10 ng/ml of TPO. At the indicated time, cells were collected and labeled with propidium iodide. Percentages of apoptotic cells in the sub-G1 peak were determined by flow cytometry. Results are representative of two independent experiments.