CD34 enrichment of umbilical cord blood.

OBJECTIVE We describe the relation between the clamping time and blood volume collected, plus two enrichment systems for CD34+ stem cells from umbilical cord blood, to achieve an excellent recovery of cells with a high proliferative ability and bone marrow reconstitution. METHOD After cord blood collection by an obstetrician, stem cell purification has been performed either with a combination of monoclonal antibodies, using the negative selection Stem Sep method, or with a positive cell selection based on their surface CD34 antigens, using the Mini Macs system. RESULTS An excellent recovery of hematopoietic progenitors: Burst Forming Unit Erythroid; Colony Forming Unit Granulocyte and Macrophage; and Colony Forming Unit Granulocyte, Erythroid, Monocyte and Macrophage, inversely related to the rising of clamping time, has been achieved with the Mini Macs system (54 % of colonies, with 90 % purity). With the Stem Sep method, recovery of hematopoietic progenitors was 35 % (with 80 % purity). CONCLUSIONS By an early clamping of umbilical cord blood, we obtained a higher number of CD34+ cells whose clonogenic activity increased with enrichment. This is particularly useful considering that the number of CD34+ stem cells contained in a unit of placental blood is enough for transplantation to a child, but not for an adult engraftment. Thus, using these methods, we can obtain a larger number of CD34+ stem cells, which increases the possibility of reducing graft-versus-host disease in adult patients, producing survival rates similar to those of transplantation of bone marrow from unrelated donors (Ref. 5).