OPTIMAL-GROWTH OF HUMAN BLOOD HEMATOPOIETIC PROGENITOR CELLS COLLECTED BY APHERESIS FOR AUTOGRAFTS

For safe autografts with peripheral blood hematopoietic cells (PBSCT), better methods for determining the kinetics of stem cell populations and predicting engraftment speed after PBSCT need to be established. C urrent methods include culture in semi-solid medium and measurement of CD34 cell surface antigen. In this study with only partially purified blood cells obtained from children with cancer in remission, we compa red the effects of phytohemagglutinin-stimulated lymphocyte-conditione d medium (PHA-LCM) and recombinant human cytokines on the growth of pr ogenitor cells in a methylcellulose culture system. Interleukin-3 (IL- 3) alone supported more progenitor growth than standard PHA-LCM by a f actor of 1.54 for colony-forming unit granulocyte/macrophages (CFU-GM) and by a factor of 1.84 for burst-forming unit/erythroids (BFU-E). No significant change, in terms of the number of growing colonies, was o bserved by adding granulocyte/macrophage colony-stimulating factor (GM -CSF), granulocyte-CSF (G-CSF), or IL-1 to IL-3. However, the addition of G-CSF resulted in increased colony size. A further increase in CFU -GM growth was observed by the addition of IFN-gamma to the combinatio n of cytokines. No significant effect was observed when stem cell fact or (SCF) was added to the combination of cytokines containing IL-3, G- CSF, and IFN-gamma. This analysis suggests that the combination of IL- 3, G-CSF, and IFN-gamma may provide sufficient stimulation for the gro wth of human blood cells. The effects of different oxygen tensions on progenitor growth in the presence of IL-3, G-CSF, and IFN-gamma were a lso evaluated. Both CFU-GM and BFU-E formation were increased when the culture was grown at 5% O-2, as compared with an ambient 20% O-2 tens ion. A small number of infused cells were grown in culture incorporati ng either IL-3, G-CSF, and IFN-gamma at 5% O-2 or PHA-LCM at 20% O-2, and the number of infused cells was correlated to the speed of hematop oietic recovery after PBSCT. Although a significant negative correlati on was observed between the number of infused CFU-GM per kilogram of t he patient's body weight and the recovery of hematopoiesis under both culture conditions, a better correlation was found when the former met hod was applied (P < .001 vs. P < .05). These findings suggest that a culture containing IL-3, G-CSF, and IFN-gamma at low O-2 tension provi des satisfactory conditions for the proliferation of blood progenitors , and that this mixture of recombinant cytokines may enable a standard ized hematopoietic progenitor assay for PBSCT. (C) 1995 Wiley-Liss, In c.