Trends in transplantation of hematopoietic stem cells from unrelated donors.

Transplants of hematopoietic stem cells from unrelated donors have become feasible for patients with a growing variety of hematologic disorders. The probability of finding a suitable donor has increased because of the expansion of the network of registries containing more than seven million HLA-typed donors worldwide. The selection of compatible donors has become more effective, thanks to the discovery of new HLA alleles and the development of precise and efficient HLA typing methods using DNA technology. Improved methods for transplantation may provide the opportunity to further decrease treatment-related toxicity and improve survival.