CD34- FOCUS ON IMMUNOMAGNETIC BEADS AND CHYMOPAPAIN( CELL SELECTION )

The aim of the present study was to develop immunoadsorption technique s for purifying CD34+ cells from the peripheral blood (PB) and the bon e marrow (BM). First, we compared two methods for isolating CD34+ cell s from patients with acute non-lymphocytic leukemia. Twenty-two sample s (17 PB, 5 BM) were obtained from 19 patients, were density cut and, after incubation with My10 antibody, were separated by panning or by i mmunomagnetic beads. Beads allowed a significantly better separation, either in terms of purification of CD34+ cells (85.5+/-11.1% vs 55.7+/ -23.8%, p=0.003) or in terms of depletion of CD34+ cells from the nega tive fractions (3.9+/-7.6 vs 30.9+/-25.1%, p=0.008). In a second study , 2 BMs from healthy subjects and 1 BM and 2 PBs from chronic myeloid leukemia patients were separated using immunomagnetic beads. The resul ts confirmed the previous study the overall frequency of CD34+ cells i n the isolated positive fractions was 85.0+/-10.6% (with a recovery of 64.0+/-5.7%), while it was only 2.7+/-6.6% in the negative fractions. In particular the purity in the two normal BMs was respectively 86 an d 97%. According to these results, the great majority of clonogenic ce lls was separated in the CD34+ fractions. Chymopapain, that was used t o detach the beads from the cells, was shown to be non-toxic to the cl onogenic cells. Positive selection of CD34+ cells with immunomagnetic beads and chymopapain is a useful method for isolating almost pure pro genitors from the PB and the BM for experimental use and is under inve stigation for clinical applications.