Fig. 4. TPO-dependent survival and proliferation of clones expressing Mpl. (A) Cells were washed three times and stimulated with various concentrations of TPO. At the indicated times, cells were either labeled with PI and percentages of apoptotic cells determined by flow cytometry (right axix) or cell proliferation was quantitated by [³H]thymidine incorporation (left axis). The results shown for [³H]thymidine incorporation are means±s.d. of triplicate experiments. Results are representative of two independent experiments.