Quantitative evaluation of apoptosis in CD34-derived megakaryocytes by supravital PI incorporation. (A) SSC/FSC dot plot showing the gate region (R1) used to analyze apoptotic cells. Gated apoptotic cells were monitored after 12 (B) and 21 (C) days of liquid suspension culture in the presence of 100 ng/mL of TPO. Left areas represent viable cells, which do not incorporate PI, whereas the right area represents apoptotic cells, incorporating PI. M1 is the percentage of apoptotic cells. The × axis shows the relative fluorescence intensity. The y axis shows the relative number of cells. Results of one experiment representative of three separate experiments are shown.