Isolation and ex vivo expansion of CD34+ cells from cord blood using dextran sedimentation and avidin column selection.

Human umbilical cord bloods were fractionated by unit gravity sedimentation in 1% (v/v) dextran, followed by immunoaffinity selection for CD34+ stem and progenitor cells. Dextran sedimentation alone enabled recovery of more than 80% of the nucleated cells present and 90% of the CD34+ cells, as determined by flow cytometry. The addition of an immunoaffinity selection step for CD34+ cells resulted in a 134-fold enrichment for CD34+ cells, with a mean yield of 64 +/- 15%. The resultant CD34+ population contained almost half the CFU-GM activity initially present in the cord bloods and could be expanded ex vivo in liquid culture.