Reduced level of platelet production in CB-derived MK culture.

(A) Platelets released from CB- (▪) and PB-derived (■) cultures. Platelets were enumerated using anti-CD61 FITC-conjugated MoAb; see also panel B. Histograms were the mean ± SD of 5 independent experiments. Statistical significance was established by using the Student t test, P < .002. Corresponding CB (●) and PB (▵) megakaryocytic growth is indicated (right axis); see also Figure 4. (B) Platelets obtained from CB-MKs (upper panels) and PB-MKs (bottom panels) were analyzed at days 12 and 14 by flow cytometry. In vitro–produced platelets were evidenced by using anti-CD61 FITC-conjugated MoAb (solid line). Expression of P-selectin on the surface of platelets before (dotted line) and after (dashed line) stimulation with 2 U/mL thrombin at 37°C for 15 minutes was analyzed by using anti-CD62 PE-conjugated MoAb. Isotype control is also presented (thin line). Representative experiment of 5 independent ones is presented.