CD34+ CELL SELECTION FROM FROZEN CORD BLOOD PRODUCTS USING THE ISOLEX300I AND CLINIMACS CD34 SELECTION DEVICES

Ex vivo expansion of cord blood (CB) cells requires CD34+ cell selecti on before expansion to obtain optimal numbers of progenitor cells. As a preliminary step to preclinical development of CB expansion, we have evaluated two clinical scale selection devices, the Isolex 300i (Baxt er Healthcare, Immunotherapy Division) and the CliniMACS (Miltenyi Bio tech Inc.), for CD34+ cell selection from frozen CB products. As expan sion of CB results in differentiation of cells, there may be a depleti on of stem cells. Therefore, only a fraction of the CB should be expan ded while a portion of the CB is maintained unmanipulated for infusion . After thawing of 40% fractions of each CB product, we observed >95% viable cells, with a median total WBC count of 1.8 x 10(8) cells. Use of the Isolex 300i resulted in a median purity of 51% CD34+ cells (n = 8) and a median recovery of 34% CD34+ cells. Use of the CliniMACS res ulted in a median purity of 54% CD34+ cells (n = 10) and a median reco very of 80% CD34+ cells. The absolute number of CD34+ cells recovered after selection varied with samples from 6.7 x 10(4) to 3.2 x 10(6) CD 34+ cells. Expansion of CD34+ cells from both systems resulted in >20- fold expansion of CFU-GM, with a median of 44-fold expansion. These da ta demonstrate the feasibility of selecting small fractions of frozen CB products using clinical scale CD34+ cell selection devices.