In vitro megakaryocyte production in normal plasma. CD34⁺-rich cells were cultured in media containing rHuMGDF and control plasma. Cultures were harvested on day 5 (A), day 7 (B), or day 10 (C-D). The abscissa shows data from FL-1H (FITC–anti-CD41), and the ordinate shows either FL-2H (phycoerythrin (PE)–anti-CD14) (A-C) or cell size, FSC (D). Cells within gate R2 are considered CD41⁺ based on the results of FITC–MOPC-21 control experiments.