G‐CSF‐mobilized peripheral blood progenitor cells for allogeneic transplantation: safety, kinetics of mobilization, and composition of the graft

Abstract

Allogeneic transplantation of peripheral blood progenitor cells (PBPC) markes the general anaesthesia of the donor unnecessary and may result in more rapid engraftment and faster recovery of the immune system. We have studied G-CSF-mediated PBPC mobilization in healthy donors and analysed the cellular composition of the resulting PBPC grafts. PBPC grafts were obtained from nine healthy donors (18-67 years old) for allogeneic or syngeneic transplantation. Six donors received 10 μg/kg G-CSF per day, the others 5-6 μg/kg. Mobilization and harvesting were well tolerated except for moderate bone pain which occurred in all donors primed with 10 μg/kg. With 10 μg/kg, a 31-fold (9-62) enrichment of circulating CD34⁺ cells was observed with peak values constantly occurring on day 5 after the start of G-CSF administration. Starting harvest on day 5, one to three collections on consecutive days yielded 5.5 x 10⁶/kg (0.9-10.7) CD34⁺ cells, 219 x 10⁶/kg (106–314) T cells, and 34 x 10⁶/kg (23–67) NK cells per 10 litres leukapheresis volume. Altogether, PBPC grafts contained 3 times more CD34⁺ cells, 7 times more T cells, and 20 times more NK cells than five allogeneic marrow grafts that were analysed for comparison. The yield of CD34⁺ cells per 10 litres apheresis volume as well as the height of the CD34⁺ peak in peripheral blood were inversely correlated to the age of the donor. In the donors primed with 5–6μg/kg G-CSF the increase of circulating CD34⁺ cells (4–7-fold enrichment) and the CD34⁺ cell yield per 10 litres leukapheresis volume (1 x 10⁶/kg [0.8-2-2]) was much smaller compared with the 10μg/kg group. In conclusion, sufficient amounts of PBPC capable of restoring haemopoiesis in allogeneic recipients can be mobilized safely by administration of G-CSF (10 μg/kg s.c. for 5 d) in healthy donors, and harvested with one or two leukapheresis procedures. Whether the large numbers of T-cells and NK cells that are contained in the collection products may influence graft-versus-host and graft-versus-leukaemia reactivities of PBPC grafts remains to be determined.