[Cord blood banks--unrelated transplants]

Hematopoietic progenitor cells are present in umbilical cord blood; placental blood (PB) previously considered as waste product now constitutes an alternative source of hematopoietic stem cells for bone marrow reconstitution. This has promoted the establishment of cord blood banks for use in unrelated transplants. The banking of PB offers many advantages: the donors do not require anesthesia, stored PB can be a valuable source of stem cells for patients from ethnic minorities underrepresented in volunteer registers, and stored PB can be made available much faster than bone marrow from unrelated donors. Preliminary clinical experience suggests that, due to the immunological immaturity of PB cells, graft versus host disease might be lower than when using bone marrow from adult donors and HLA restrictions might be less stringent. If the number of nucleated cells in PB often appears low for patients weighing more than 40 kg, clinical data suggest that the number of stem cells may be sufficient for adult transplantation. The number of cord blood banks throughout the world is increasing rapidly. In the USA and Europe, more than 10,500 PB units are stored and available for transplantation. In the next 5 years, a total of 50,000 PB will be reached which may be sufficient to provide for the majority of candidates for unrelated BM transplantation. The practices of umbilical cord blood collection, mother selection, infectious disease screening, cell manipulation and storage must be standardized. Some accreditation process should be mandatory for assessing operating procedures and the quality assurance programs of the banks, and for allowing the international exchange of placental blood between transplant centers.