Summary:ings is unknown at present, some centers currently prefer to transplant these patients with PBSCs that have been depleted of potentially contaminating tumor cells. One To evaluate the feasibility and efficacy of CD34 ؉ cell immunoselection from routine peripheral blood stem possible method of reducing tumor cell contamination of the PBSC preparations is the positive selection of CD34 ϩ cell (PBSC) harvests in very small children a prospective study was performed in 15 children with advanced hematopoietic progenitor cells. 3 Initial trials of autografts with CD34 ϩ PBSCs have mainly been performed in adult neuroblastoma weighing 20 kg or less. Products of two consecutive leukaphereses carried out on a COBE Specpatients 4-6 and, outside of our team, 7 and so thus far there have been no reports of studies performed in small children. tra separator after G-CSF alone mobilization were pooled for immunoselection on Ceprate column. TheThe principal reasons for the restriction in the use of this technique in children with low body mass are PBSC collecmedian number of CD34 ؉ cells and total CFU-GM collected were respectively 5.9 ؋ 10 6 /kg (range 2.3-23.4) tion-associated difficulties (venous access, flow rate, metabolic and hemodynamic problems). In particular, when and 126.9 ؋ 10 4 /kg (range 52.9-559.9). After separation the median number of CD34 ؉ cells in the adsorbed fraclarge-scale collection is planned, which may require the processing of a considerable number of blood volumes, the tion was 2.6 ؋ 10 6 /kg (range 1-9.8) with a median purity of 54% (range 21-82) and a median of 95.7-fold safety of the procedure is of special importance. [8][9][10][11][12][13] We report the results of a prospective study designed to (range 35-250) enrichment. Thirteen patients underwent autografts with CD34 ؉ PBSCs after a busuldetermine whether sufficient numbers of CD34 ϩ cells can be obtained to provide reliable post-graft hematopoietic fan 600 mg/m 2 ؉ melphalan 180 mg/m 2 preparative regimen. The median number of days to achieve an reconstitution in very small children, after positive immunoselection of routinely collected leukaphereses products. absolute granulocyte count of 0.5 ؋ 10 9 /l and a platelet count of 20 ؋ 10 9 /l were respectively, 12 (range 10-24)We have investigated the feasibility and efficacy of this technique using the avidin-immunoaffinity column device and 35 (range 25-43). The median number of platelet transfusions was nine (range 2-15). We conclude that (Ceprate Stem Cell Concentrator; CellPro, Bothell, WA, USA) in 15 children with advanced neuroblastoma. These safe and effective immunoselection and transplantation of CD34 ؉ PBSC can be accomplished in children with patients may theoretically benefit from the isolation of CD34 ϩ hematopoietic progenitors, since the target CD34 low body mass.