Expression of the CXCR4 receptor on peripheral blood platelets. Platelets were prepared as described in Materials and Methods. Platelets were stained with a PE-conjugated anti-CXCR4 MoAb or isotype control antibody and then analyzed by flow cytometry. The staining with control antibody is shown as the solid profile and the staining with the anti-CXCR4 antibody is shown as the thin line.