Human umbilical cord blood banking and transplantation: a state of the art.

Human umbilical cord blood has proven to be a feasible alternative source of hematopoietic stem cells for pediatric and some adult patients with major hematologic disorders. This has promoted the establishment of cord blood banks for use in unrelated transplants worldwide. The banking of umbilical cord blood offers many advantages: absence of donor risk, absence of donor attrition, immediate availability, and the ability to expand available donor pools in targeted ethnic and racial minorities currently underrepresented in all bone marrow registries. Preliminary clinical experience suggests that, due to the immunological immaturity of cord blood cells, graft versus host disease might be lower than when using bone marrow from adult donors and HLA restrictions might be less stringent. Techniques to improve the efficacy of blood banks are currently under investigation. Closed cord blood collection methods have proven to be superior to open in reducing the risk of microbial contamination. Efficient banking requires volume reduction of cord blood units without significant loss of progenitor cells, in order to decrease storage space and cost, and this may be achieved by using the separation techniques. Cryopreservation and thawing techniques have been established and do not seem to affect the viability and progenitor cell recovery or the feasibility of CD34(+) selection and ex vivo expansion. Nevertheless, many scientific, ethical, and social questions have arisen in connection with cord blood banking that need to be addressed.