Toward cord blood banking: density-separation and cryopreservation of cord blood progenitors.

It has been shown that cord blood collected at birth can be used to successfully engraft a human lymphocyte antigen (HLA)-matched sibling suffering from a malignant disease. It has been further suggested that this source of cells may be used in unrelated but HLA-compatible patients. These wide indications would imply the establishment of cord blood banks comprising 10(5) or more samples. In this report we show that it is possible to fractionate and freeze cord blood samples without major loss in granulomonocytic or erythroblastic progenitors (CFU-GM and BFU-E). Density separation should be carried out using Percoll of density 1.080. Separated samples should be frozen and thawed in the presence of DNase I. This procedure should allow the storage of approximately 10 mL samples in cryotubes containing a number of CFU-GM and BFU-E sufficient to engraft a patient weighing less than 30 kg. These data provide a rationale for establishing cord blood banks.