ISOLATION AND TRANSPLANTATION OF AUTOLOGOUS PERIPHERAL CD34(-ACTIVATED CELL SORTING() PROGENITOR CELLS HIGHLY PURIFIED BY MAGNETIC)

Peripheral stem cells were mobilized and collected in 26 pediatric pat ients with malignant diseases. A total of 47 leukaphereses were perfor med in the 26 patients. The mean number of nucleated cells collected w as 4.5 +/- 2.6 x 10(8)/kg and the number of CD34(+) progenitors collec ted was 6.7 +/- 6.8 x 10(6)/kg. CD34-positive selection was performed using a two-step method of magnetic-activated cell sorting (MACS) in 2 4 patients or a combination of an immunoaffinity column and MACS in tw o 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 x 10(6)/kg. Thus, the mean recovery of CD34(+) cells was 93 +/- 1 0%. In 22 of the 26 patients, high-dose chemotherapy was performed wit h subsequent reinfusion of the highly purified CD34(+) cells. In all 2 2 patients, a normal hematopoietic reconstitution was seen with a mean time of 12.4 +/- 2.7 days to reach >0.5 x 10(9)/I neutrophils (range 8-19 days). The time to reach independence from platelet transfusion w as 31.6 +/- 17.0 days (range 16-78 days). There were no transplant-rel ated deaths. In summary, we have shown that mobilized peripheral CD34( +) progenitors can be highly purified with a good recovery and that re infusion of these cells after high-dose chemotherapy results in a rapi d, complete and sustained engraftment. We conclude that this method ca n be used for purging in any CD34-negative malignancies and for autolo gous T and B cell depletion in the treatment of autoimmune diseases wi th high-dose immunoablative therapy.