Influence of the different CD34+ and CD34- cell subsets infused on clinical outcome after non-myeloablative allogeneic peripheral blood transplantation from human leucocyte antigen-identical sibling donors

Currently, no information is available regarding the influence of the different CD34(+) cell subsets infused on the haematopoietic recovery, following non-myeloablative allogeneic peripheral blood stem cell transplantation (allo-PBSCT). We have explored, in a group of 13 patients receiving non-myeloablative allo-PBSCT from human leucocyte antigen-identical sibling donors, the influence of the total dose of CD34(+) haematopoietic progenitor cells (HPC) infused, compared with that of the different CD34(+) HPC and CD34(-) leucocyte subsets in the leukapheresis samples, on both engraftment and clinical outcome. The overall numbers of total CD34(+) HPC (P = 0.002) and myelomonocytic-committed CD34(+) HPC infused (P = 0.0002) were strongly associated with neutrophil recovery (> 1 x 10(9) neutrophils/ l), the latter being the only independent parameter influencing neutrophil recovery. Regarding long-term engraftment, only the number of immature CD34(+) HPC infused/kg correlated with the duration of hospitalization in the first 2 years after discharge (r = -0.75, P = 0.005). Both the overall amount of CD34(+) HPC and the number of myelomonocytic CD34(+) HPC infused showed a significant influence on the risk of graft-versus-host disease (GVHD). Thus, the overall probability of GVHD was 100% vs 25% for patients receiving greater than or equal to5 x 10(6) CD34(+) HPC or greater than or equal to3.5 x 10(6) of myelomonocytic-committed CD34(+) HPC vs lower doses (P = 0.013). None of the other CD34(+) and CD34(-) cell subsets analysed correlated with development of GVHD. In summary, our results suggest that in non-myeloablative allo-PBSCT, high numbers of CD34(+) HPC, especially the myelomonocytic-committed CD34(+) progenitors, lead to rapid neutrophil engraftment. However, they also strongly impair clinical outcome by increasing the incidence of GVHD.