Use of DNA polymorphisms to monitor engraftment after allogeneic bone marrow transplantation

Bone marrow transplantation (BMT) has been established as a life-saving procedure in hematologic malignancies and bone marrow failure syndromes, and it may be valuable in other types of neoplastic disease. DNA polymorphisms are used to monitor engraftment after transplantation from a related or unrelated donor. DNA polymorphisms are not useful after autologous BMT or if the donor is an identical twin. The most valuable polymorphism for this purpose is caused by variation in certain repeated sequences that are known as variable number of tandem repeats (VNTR). The VNTRs are valuable because they each have several alleles increasing the probability of finding one that is useful in a given case. This method can be used to sensitively detect small amounts of residual recipient hematopoiesis. To accomplish this the laboratory must first find a polymorphic allele that is unique in the recipient. Detection of the unique allele in peripheral blood or bone marrow after BMT is tantamount to finding recipient hematopoiesis. The presence of both donor and recipient hematopoiesis can result in a state of stable mixed chimerism and not necessarily presage a relapse after BMT for leukemia; however, the presence of residual recipient cells in some cases may indicate an increased probability of relapse, particularly in chronic myelogenous leukemia.