Immune reconstitution after transplantation of autologous peripheral stem cells in children: a comparison between CD34+ selected and non-manipulated grafts

Background & Aims High-dose chemotherapy followed by autologous stem cell transplantation (ASCT) improves the prognosis in pediatric patients with several solid tumors and lymphomas [1]. Little is known about the reconstitution of the immune system after ASCT and the influence of CD34+ cell selection on the reconstitution in pediatric patients Methods Between 1990 and 2001, 94 pediatric patients with solid tumors and lymphomas received autologous CD34+ selected or unmanipulated peripheral stem cells after high-dose chemotherapy. CD34+ selection was carried out with magnetic microbeads. The absolute numbers of T cells, B cells and NK cells were measured and compared in both groups at various time points post-transplant. Results Recovery of T cells was significantly faster in the unmanipulated group at day 30, with no significant difference later on. Reconstitution of B and NK cells was similar in both groups without significant difference at any time. The CD34+-selected group was divided into patients receiving less or more than 5.385 × 106/kg CD34+ cells. Patients in the CD34+ high-dose group displayed significantly faster reconstitutions of neutrophiles and lymphocyte subsets than the CD34+ low-dose group. Conclusions Engraftment and reconstitution of leukocytes, B cells and NK cells after transplantation of CD34+ selected stem cells were comparable to that in patients receiving unmanipulated grafts. T cell recovery was faster in the unmanipulated group only within the first month. However, this delay could be compensated by transplantation of > 5.385 × 106 CD34+ cells/kg.Especially for patients receiving immunotherapy after high-dose chemotherapy large numbers of immune effector cells such as NK and T cells are necessary to mediate antibody-dependent cellular cytotoxicity. Therefore, in patients receiving autologous CD34+-selected grafts, our data emphasize the need to administer high stem cell counts.