Isolation and transplantation of autologous peripheral CD34⁺ progenitor cells highly purified by magnetic-activated cell sorting

Abstract

Peripheral stem cells were mobilized and collected in 26 pediatric patients with malignant diseases. A total of 47 leukaphereses were performed in the 26 patients. The mean number of nucleated cells collected was 4.5 ± 2.6 × 10⁸/kg and the number of CD34⁺ progenitors collected was 6.7 ± 6.8 × 10⁶/kg. CD34-positive selection was performed using a two-step method of magnetic-activated cell sorting (MACS) in 24 patients or a combination of an immunoaffinity column and MACS in two patients. The purity of the positively selected CD34⁺ progenitors was 98.8 ± 0.7% and the number of isolated CD34⁺ cells was 6.5 ± 5.9 × 10⁶/kg. Thus, the mean recovery of CD34⁺ cells was 93 ± 10%. In 22 of the 26 patients, high-dose chemotherapy was performed with subsequent reinfusion of the highly purified CD34⁺ cells. In all 22 patients, a normal hematopoietic reconstitution was seen with a mean time of 12.4 ± 2.7 days to reach >0.5 × 10⁹/l neutrophils (range 8–19 days). The time to reach independence from platelet transfusion was 31.6 ± 17.0 days (range 16–78 days). There were no transplant-related deaths. In summary, we have shown that mobilized peripheral CD34⁺ progenitors can be highly purified with a good recovery and that reinfusion of these cells after high-dose chemotherapy results in a rapid, complete and sustained engraftment. We conclude that this method can be used for purging in any CD34-negative malignancies and for autologous T and B cell depletion in the treatment of autoimmune diseases with high-dose immunoablative therapy.