LACK OF DNA-SYNTHESIS AMONG CD34(-BLOOD AND IN CYTOKINE-MOBILIZED BLOOD() CELLS IN CORD)

Flow cytometric DNA analysis was performed in combination with three-c olour immunological staining of cell surface antigens on density-separ ated mononuclear cells (MNC) obtained from peripheral blood (PB) befor e, during and after cytokine stimulation of healthy adults. The aim of the study was to determine the cell-cycling status of haemopoietic pr ogenitor cells mobilized into the blood of healthy volunteers during a 5d treatment period with 5 mu g per kg body weight of either granuloc yte colony-stimulating factor (G-CSF) or granulocyte-macrophage colony -stimulating factor (GM-CSF). Despite considerably increasing numbers of CD34(+) PB MNC, the latter were not found to be in S/G(2)M phase, w hereas, among the CD34(-) MNC, the proportion of cells in S/G(2)M phas e increased from < 0.1% to 0.75 +/- 0.4% (GM-CSF) and to 1.34 +/- 0.75 % (G-CSF) and dropped again after discontinuation of the cytokine stim ulation. These cells expressed CD33 but were negative for CD45RA, CD3, CD19 and CD14 and were thus considered granulopoietic cells. Analogou s results were obtained from analyses of cord blood (CB). In contrast, CD34(+) cells from bone marrow (BM) were partially (between 9% and 15 %) found to be in S/G(2)M phase. The non-cycling status of PB and CB p rogenitor cells was confirmed by the analysis of CD34(+) cells enriche d from the two cell sources. However, in vitro stimulation of these pr ogenitor cells using IL3, GM-CSF, erythropoietin and steel factor (SF) revealed that, after 48 h in suspension culture, up to 30% of the CD3 4(+) cells were in S/G(2)M phase. The fact that cycling CD34(+) cells are only detectable in BM but not in PB or CB may suggest different ad hesive properties of migrating/mobilized 'stem cells' which may requir e the BM micro-environment for adequate proliferation in vivo.