Transplantation of peripheral blood stem cells mobilized by haematopoietic growth factors in childhood

: Peripheral blood stem cells (PBSC), mobilised by means of haematopoietic growth factors (HGF) with or without chemotherapy, are being used routinely for autologous rescue after high-dose chemo-radiotherapy in paediatric patients with lymphoma and selected solid tumours because of the ease of collection and the accelerated kinetics of neutrophil and platelet engraftment as compared with bone marrow cells. Recent reports indicated that HGF-mobilised PBSC can also be employed in childhood as an alternative to bone marrow allograft when the donor is an adult or with the aim of reversing graft failure in patients who were previously given a marrow allograft. Notwithstanding this wide use of PBSC, several biological and clinical questions of crucial relevance are still unsolved. In this article, we will analyse: (1) the optimal timing for PBSC collection after cytokine-based mobilising regimens; (2) the variables affecting the yield of peripheral blood progenitors; (3) the minimum threshold and the optimal number of PBSC that should be infused for autologous and allogeneic transplant, respectively; (4) the biological mechanisms underlying mobilisation of haematopoietic stem cells into circulation; (5) the incidence of graft-versus-host disease and the biological characteristics of donor lymphocytes in patients given allogeneic transplant of PBSC; and (6) the most relevant peculiarities in the kinetics of immune recovery of patients given allogeneic transplant of PBSC, as compared to bone marrow transplant recipients.