Apoptosis of normal and ET MK cells after 7 and 14 days of culture with 100 ng/mL TPO. Apoptosis in normal donors (ND) and ET MKs was quantified by PI and annexin-V–FITC stainings after 7 and 14 days of culture. (A) The results of 1 representative experiment, the x-axis representing the relative fluorescence intensity and the y-axis, the relative number of cells. (B) Histograms showing mean ± SD percentages of positive ET (; 5 cases) and normal (▪; 6 cases) MKs for PI (sub-G1 peak DNA evaluation) and annexin-V–FITC.