PRIMORDIAL ROLE OF CD34(-) CELLS IN EARLY AND LATE TRILINEAGE HEMATOPOIETIC ENGRAFTMENT AFTER AUTOLOGOUS BLOOD-CELL TRANSPLANTATION()38()

In order to better define which cell subset contained in graft product s might be the most predictive of haemopoietic recovery following auto logous blood cell transplantation (ABCT), the relationships between th e amounts of reinfused mononuclear cells (MNC), CFU-GM, total CD34(+) cells and their CD33 and CD38 subsets, and the successive stages of tr ilineage engraftment kinetics, were studied in 45 cancer patients, usi ng the Spearman correlation test, a linear regression model and a log- inverse model. No relationship was found between the infused numbers o f MNC, CD33(+) and CD33(-) subsets observed and the numbers of days to reach predetermined absolute neutrophil (ANC), platelet and reticuloc yte counts. The infused numbers of CFU-GM, CD34(+) and CD34(+)38(+) ce lls correlated inconstantly with haemopoietic recovery parameters. The strongest and the most constant correlations were significantly obser ved between the infused numbers of CD34(+)38(-) cells and each triline age engraftment parameter. The log-inverse model determined a threshol d dose of 0.05 x 10(6) (= 5 x 10(4)) CD34(+)38(-) cells/kg, below whic h the trilineage engraftment kinetics were significantly slower and un predictable. Post-transplant TBI-conditioning regimens increased the l ow cell dose-related delay of engraftment kinetics whereas post-transp lant administration of haemopoietic growth factors (HGF) seemed to abr ogate this delay. This would justify clinical use of HGF only in patie nts transplanted with CD34(+)38(-) cell amounts lower than the propose d threshold value. This study suggests that the CD34(+)38(-) subpopula tion, although essentially participating in late complete haemopoietic recovery, is also composed of committed progenitor cells involved in early trilineage engraftment.