Clinical and basic science studies of human umbilical cord blood: Implications for the GVL effect following cord blood transplantation

Human umbilical cord blood (CB) is a readily available source of stem cells and naive or ontogenically immature leukocytes [1-7]. Increasingly, CB is being utilized as an alternative to bone marrow (BM) for stem-cell transplants. The first CB transplant was performed in 1988 as a treatment for Fanconi's anemia [8]. Numerous CB transplants have since been performed to treat a variety of malignant and nonmalignant hematopoietic diseases as well as metabolic disorders [9,10]. 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 BM donor registries [11-13]. Clinical results worldwide of CB transplantation performed in settings-ranging from matched sibling to mismatched unrelated-are encouraging. In general, the time to neutrophil engraftment is similar to that for bone marrow transplant (BMT) [10]. Importantly, there is less likelihood of severe acute graftversus-host disease (aGVHD) following CB transplants even when unrelated mismatched grafts are used [9,12,14-17]. Potential downsides to CB transplantation are delayed time to platelet independence and questions regarding the ability to engraft adults [13]. However, there are reports in the literature of adult-size patients being successfully engrafted by CB [17-19].