CD34(+) CD41(+) CELLS BEST PREDICT PLATELET RECOVERY AFTER AUTOLOGOUSPERIPHERAL-BLOOD STEM-CELL TRANSPLANTATION/

Reliable markers for megakaryocytic reconstitution after peripheral bl ood stem cell transplantation (PBSCT) have not been established. To de termine a convenient and reliable predictor, we measured the number of megakaryocyte progenitor cells in PBSC grafts by clonogenic and flow cytometric assays. Seventeen patients with hematological and solid mal ignancies were included in this study. For the clonogenic assay, we us ed thrombopoietin (TPO) as a growth factor to evaluate the maximum num ber of megakaryocyte progenitor cells, Using a flow cytometric assay, we examined the expression of platelet glycoproteins on CD34(+) cells to count the number of megakaryocyte progenitor cells. We used buffer containing EDTA to prevent platelet adhesion to CD34(+) cells and sele cted CD34(+) cells by immunomagnetic beads. The best correlation was o bserved between the number of CD34(+)/CD41a(+) cells and the time to p latelet recovery (P = 0.0205), rather than the total number of CD34(+) cells. In addition, a close correlation was observed between the numb er of CD34(+)/CD41a(+) cells and colony-forming unit megakaryocyte (CF U-MK) (P = 0.0018), These observations suggest that the number of CD34 (+)/CD41a(+) cells is the best predictor for platelet reconstitution a fter PBSCT.