THE IMPORTANCE OF ENUMERATION OF CD 34 PO SITIVE CELLS BEFORE STEM-CELL COLLECTIONS

The recent significant improvement in disease-free survival in patient s with certain haematological malignancies is due to high-dose chemoth erapy and subsequent autologous bone marrow and/or stem cell transplan tation. The proliferation and egression of stem cells into the periphe ral blood must first be stimulated by defined chemotherapy and/or by a dministration of cytokines. However, the increase of circulating stem cells in peripheral blood is limited to only a few days. By immunologi cally analysing white blood cells for the expression of the surface an tigen CD 34 it is possible to calculate the numbers of haematopoietic progenitor cells. Thus, besides monitoring haematopoietic recovery, th e estimation of CD34+ cells in the peripheral blood can be used to ind icate the optimal time point for stem cell collection. Two to four ste m cell phereses (one per day) may then yield sufficient stem cells to enable the safe and rapid reconstitution of haematopoiesis following s upralethal chemotherapy.