Coexpression analysis of CXCR-4 and differentiation-related antigens on purified, circulating CD34⁺ hematopoietic progenitor cells. Results from a representative three-color flow cytometry analysis are shown. After immunomagnetic separation and staining with CD34-PerCP and the respective FITC/PE-labeled antibodies, CD34⁺ cells were gated in a FSC/SSC and SSC/FL-3 dot plot. Only low SSC/CD34⁺ cells were further analyzed. Most of the cells of the more primitive subsets (CD34⁺/CD38⁻, CD34⁺/Thy-1⁺, CD34⁺/HLA-DR⁻, CD34⁺/CD45RA⁻, CD34⁺/CD11a⁻) coexpressed CXCR-4, as indicated by the shaded areas.