ISOLATION OF CD34(-CELL COMPONENTS USING THE BAXTER ISOLEX SYSTEM() CELLS FROM BLOOD STEM)

The CD34 antigen is expressed by human hematopoietic progenitor and st em cells. These cells are capable of reconstituting marrow function af ter marrow-ablative chemo-radiotherapy. Several different technologies have been developed for the separation of CD34(+) cells from bone mar row or peripheral blood stem cell (PBSC) components. We used an immuno magnetic separation technique to enrich CD34(+) cells from PBSC compon ents in anticipation of autologous transplantation for patients with B lymphoid malignancies. Twenty-nine patients enrolled on this study an d received mobilization chemotherapy followed by GCSF. Of these, 21 ac hieved a peripheral blood CD34(+) cell level of at least 2.0 X 10(4)/l required by protocol for separation of the stem cell components. A me dian of three components per patient was collected for processing. The average CD34(+) cell concentration in the components after apheresis was 1.0 +/- 1.2%, After the CD34(+) cell selection, the enriched compo nents contained 0.6 +/- 0.6% of the starting nucleated cells. The reco very of CD34(+) cells, however, averaged 58.4 +/- 19.2% of the startin g cell number, with a purity of 90.8 +/- 6.5%. Overall depletion of CD 34(-) cells was 99.96 +/- 0.06%. Nineteen patients were treated with m arrow-ablative conditioning regimens and received an average of 6.2 +/ - 2.0 X 10(6) CD34(+) cells/kg body weight. These patients recovered t o an ANC >0.5 X 10(9)/l at a median of 11 days (range 8-14), and plate let transfusion independence at a median of 9 days (range 5-13). Four patients died of transplant-related complications or relapse before 10 0 days after transplantation. No patient required infusion of unsepara ted cells because of failure of sustained bone marrow function. These data demonstrate that peripheral blood-derived CD34(+) cells enriched by use of an immunomagnetic separation technique are capable of rapid engraftment after autologous transplantation.