Antigenic expression and DNA content of cytokine-expanded human megakaryocytic cells. Developing megakaryocytes analyzed by two-color flow cytometry, evaluating glycoprotein IIb/IIIa (CD41) antigen expression (FITC; abcissa) and DNA content (propidium iodide; ordinate). The vertical quadrant marker in the flow diagrams represents upper limit of nonspecific fluorescence, using an isotype-specific inappropriate antibody as a control.