Abstract 56

Background: CD34+ cells adhere to the compartment of hematopoetic stem and progenitor cells. A low frequency of CD34+ cells hampers an adequate characterization and their potential clinical use. Several strategies have been developed to enrich CD34+ cells. We analysed the performance of three different enrichment procedures for CD34+ cord blood cells.

Material and Measurements: Mononuclear cord blood cells were subjected to CD34-specific enrichment using an biotin-streptavidine-based method (CellPro, n=9) and two different immunomagnetic strategies (Dynabeads, Dynal, n=7; MACS, Miltenyi Biotec, n=18).

Results: Mononuclear cells displayed a small fraction of CD34+ cells with 6.5 ± 3.9% (±SD) used for CellPro isolation, 3.5 ± 2.0% (Dynal) and 2.2 ± 1.2% (Miltenyi Biotec). Resulting target cells after enrichment consisted of 64.0 ± 14.2%(CellPro), 82.6 ± 6.7% (Dynal) and - significantly (p<0.02) elevated - 93.4 ± 3.6% CD34+ cells (Miltenyi Biotec). Yield of target cells was low using the biotin-streptavidine-based CellPro system(17.3%, range 1.8-35.6) as well as the immunomagnetic Dynal system (18.0%, range 2.3-64.2%). Significant (p<0.03) higher yields (45.2%, range 19.1-86.1%) were attained using the MACS technique (Miltenyi Biotec). Purified CD34+ cells displayed a fraction of 12%, range 6-20%(Dynal), and 14%, range 7-23% (Miltenyi Biotec), hematopoietic progenitors and revealed a high proliferative capacity in cytokine-supplemented suspension culture.

Conclusions: Commercially available systems allowed a fast and simple enrichment of CD34+ cord blood cells. The performance of cell enrichment, as measured by purity and yield of target cells, differed dependent on the strategy used. With the aim to get a maximum of cells, almost enriched to homogeneity, the technique of Magnetic Cell Separation, MACS (Miltenyi Biotec), significantly displayed the most promising results.