The magnetic cell sorting (MACS) system was used to isolate CD34+ human umbilical cord blood (HUCB) stem cells (SC). Variables that might affect the detection of CD34+ cells, purity, enrichment, and yield of CD34+ cells, and the co-expression by CD34+ cells of CD38 and HLA-DR and their clonogenic capabilities were investigated. These variables were (a) separation technique [Ficoll, Percoll mononuclear cell (MNC) preparation] and (b) storage of HUCB [fresh, stored overnight (O/N) at 4°C or frozen]. There was no difference between MNC prepared for MACS CD34+ SC isolation by Ficoll or Percoll separation. The use of fresh, O/N, or frozen HUCB did not affect the isolation of CD34+ SC.
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