CXCR4 expression on megakaryocytes and platelets. (A, B) Representative data of flow cytometric analysis of CD41a and CXCR4 on megakaryocytes grown in culture are shown. Cord blood CD34⁺ cells were cultured for 6 days in the presence of a combination of SCF and PEG-rhuMGDF. Cells were stained using an anti-CD41a MoAb in combination with either an isotype control antibody (A) or the anti-CXCR4 MoAb (B). (C) CXCR4 expression on freshly isolated megakaryocytes after percoll enrichment. (D) Platelets, depleted in leukocytes, were labeled using a similar procedure. Labeling with control MoAb is shown by the thin line. The thick line shows the staining with the anti-CXCR4 MoAb.