Fig. 4. Membrane phenotype of megakaryocytic cells. HPCs grown in serum-free medium in the presence of 100 ng/ml TPO alone (Control), or in combination with 10 µM PD98059 or 50 nM rapamycin were analyzed throughout the culture (from day 0 up to day 12) by flow cytometry using PE- or FITC-conjugated mAbs. The percentages of CD34⁺, CD41⁺, CD61⁺, CD42b⁺ and CD62⁺ cells are shown as the mean ± s.e.m. of three independent experiments.