Expression of cell surface markers. A) Representative overlay plots showing the expression of cell surface markers, as determined by flow cytometry. Single color immunostaining of freshly isolated PBMCs at day 0 (black plots) and culture-derived EPCs at day 10 (gray plots) was performed with saturating concentrations of mouse anti-human PE-conjugated monoclonal antibodies directed against CD14, CD34 and VEGFR2. Overlay plots are presented as the number of events over the log of associated fluorescence. B) Histogram represents the mean data ± SEM of at least 4 independent experiments.