Bone marrow transplantation in leukemia in the absence of an HLA-identical sibling donor.

Bone marrow transplantation is a potentially curative treatment for patients with leukemia, aplastic anemia, metabolic disorders, and immunodeficiency. One of the main problems ofthis procedure is the graftversus-host reaction induced in the recipient by the immune function of the transplanted marrow. In order to minimize the risks of graft rejection and graft-versus-host disease (GVHD), marrow transplantation has in general been limited to patients with HLAidentical sibling donors. The majority ofpatients, however, will not have such a family member available. To cope with such patients, several alternative approaches have been investigated. One of them is autologous bone marrow transplantation (with or without antileukemic treatment of the marrow); another is transplantation of haploidentical marrow after T-cell depletion by separation with lectins, E rosetting, or monoclonal antibodies. Most experience in this field has been gained in patients with severe combined immunodeficiency. Another alternative for these patients is bone marrow transplantation with the marrow of an unrelated but matched or partially matched donor, or even a mismatched family donor. Only few clinical data are available to assess the latest acceptable limits for HLA incompatibility in human bone marrow transplantations with