Umbilical cord blood as a new and promising source of unrelated-donor hematopoietic stem cells for transplantation.

A rapidly accelerating number of transplantations of hematopoietic stem cells from human umbilical cord blood have been performed for malignancies and for congenital disorders. Umbilical cord blood presents multiple advantages over bone marrow as a source of stem cells. Harvesting presents no donor risk or discomfort, the product carries less likelihood of infectious disease transmission, and collection can be targeted to include minority groups underrepresented in bone marrow donor registries. Furthermore, the interval from initiation of a search to the transplantation procedure has been much shorter than for bone marrow, and the lack of mature T lymphocytes in cord blood reduces the incidence and severity of graft-versus-host disease in transplant recipients. Potential problems under current investigations include whether cord blood provides a sufficient quantity of stem cells for adult recipients or an effective level of "graft-versus-leukemia" effect.