FLOW CYTOMETRIC CHARACTERIZATION OF CD34+ HEMATOPOIETIC PROGENITOR CELLS IN MOBILIZED PERIPHERAL BLOOD AND BONE MARROW OF CANCER PATIENTS

D34, a heavily glycosylated membrane molecule, is characteristically expressed on early and committed hematopoietic progenitor cells (HPC).1,2 This antigen is present on 1-3 % of normal bone marrow (BM) cells, on 0.01-0.1 % of peripheral blood (PB) cells and on 0.1-0.4 % of cord blood (CB) cells. Marked increases of PB CD34+ cells occur during the recovery phase after myelosuppressive chemo-therapy and/or growth factor administration.3,4 These cells, which can be estimated by flow cytometry, collected on a large scale by leuka-pheresis and cryopreserved for transplantation, are able to engraft and to reconstitute hemo-poiesis after myeloablative therapy.5,6 PB HPC transplantation is increasingly used for treatin