G-CSF-MOBILIZED PERIPHERAL-BLOOD PROGENITOR CELLS FOR ALLOGENEIC TRANSPLANTATION - SAFETY, KINETICS OF MOBILIZATION, AND COMPOSITION OF THEGRAFT

Allogeneic transplantation of peripheral blood progenitor cells (PBPC) makes the general anaesthesia of the donor unnecessary and may result in more rapid engraftment and faster recovery of the immune system. W e have studied G-CSF-mediated PBPC mobilization in healthy donors and analysed the cellular composition of the resulting PBPC grafts. PBPC g rafts were obtained from nine healthy donors (18-67 years old) for all ogeneic or syngeneic transplantation. Six donors received 10 mu g/kg G -CSF per day, the others 5-6 mu g/kg. Mobilization and harvesting were well tolerated except for moderate bone pain which occurred in all do nors primed with 10 mu g/kg. With 10 mu g/kg, a 31-fold (9-62) enrichm ent of circulating CD34(+) cells was observed with peak values constan tly occurring on day 5 after the start of G-CSF administration. Starti ng harvest on day 5, one to three collections on consecutive days yiel ded 5.5 x 10(6)/kg (0.9-10.7) CD34(+) cells, 219 x 10(6)/kg (106-314) T cells, and 34 x 10(6)/kg (23-67) NK cells per 10 litres leukapheresi s volume. Altogether, PBPC grafts contained 3 times more CD34(+) cells , 7 times more T cells, and 20 times more NK cells than five allogenei c marrow grafts that were analysed for comparison. The yield of CD34() cells per 10 litres apheresis volume as well as the height of the CD 34(+) peak in peripheral blood were inversely correlated to the age of the donor. In the donors primed with 5-6 mu g/kg G-CSF the increase o f circulating CD34(+) cells (4-7-fold enrichment) and the CD34(+) cell yield per 10 litres leukapheresis volume (1 x 10(6)/kg [0.8-2.2]) was much smaller compared with the 10 mu g/kg group. In conclusion, suffi cient amounts of PBPC capable of restoring haemopoiesis in allogeneic recipients can be mobilized safely by administration of G-CSF (10 mu g /kg s.c. for 5 d) in healthy donors, and harvested with one or two leu kapheresis procedures. Whether the large numbers of T-cells and NK cel ls that are contained in the collection products may influence graft-v ersus-host and graft-versus-leukaemia reactivities of PBPC grafts rema ins to be determined.