Cord blood transplant: current and future issues.

Cord blood as the source of hematopoietic stem cells has several advantages over bone marrow cells for transplant purpose. It is readily available, and causes no physical harm or inconveniences to the donor in the processing of harvesting cells. Waiting time between initiating the search and the time to transplant from an unrelated donor is much shorter with cord blood than with unrelated donor bone marrow. The incidence of graft-versus-host diseases is much less. Because of these advantages, cord blood has been increasingly used as the source of stem cells. As of this writing, more than 200 cord blood transplants have been done in patients with hematological malignancies, solid tumors, hematological diseases, immunodeficiency syndromes, and metabolic diseases. One of the limitations inherent in the cord blood is its limited number of hematopoietic stem cells. Thus it has been primarily used for pediatric patients, though more recently, adult patients also have been transplanted with cord blood as people have become more experienced in harvesting cord blood thus yielding a larger number of stem cells in a given specimen. Efforts have been made to amplify stem cells in vitro following harvesting cord blood stem cells, so that adult recipients also would routinely benefit from this resource. Cord blood lymphocytes are functionally "naive", do not generate vigorous mixed lymphocyte culture reactivities. The low incidence of graft-versus-host disease in the recipients of cord blood is due to this particular property. It is highly desirable that the world wide cord blood registry, similar to the international bone marrow registry would be instituted, but there are logistic, ethical and financial problems that need to be resolved. Cord blood is one of the best stem cell sources, and its application is quite wide.