Autologous bone marrow transplant in the treatment of acute leukaemia

Immune ablation with stem-cell rescue: a possible cure for systemic lupus erythematosus?

The impressive prolongation of survival has been the most important progress made in clinical systemic lupus erythematosus (SLE). Quality of life has also greatly improved, including pregnancy. However, persisting disease and therapy-related morbidity outcomes justify new approaches, different from the usual long-term palliative immunosuppression. Haematopoietic stem cells (HSCs) from healthy histocompatible mice are capable of curing murine SLE after eradication of the original HSCs with total body irradiation. Syngeneic and even autologous HSCs are also capable of curing induced experimental autoimmune diseases such as adjuvant arthritis and experimental allergic encephalomyelitis. In man allogeneic bone-marrow transplantation (BMT) is becoming progressively safer, but cannot yet be offered to SLE patients. However, syngeneic transplants from twins non-concordant for the disease would be justified. Conditioning with high-dose cyclophosphamide followed by autologous HSC rescue, from the marrow and/or from the peripheral blood, may already be regarded as a powerful immunosuppressive procedure for selected cases of SLE and other severe autoimmune diseases. Autologous transplant procedures are not saddled with the immunologic problems of allo-BMT. Although eradication of SLE may not be achieved by auto-BMT, minimal residual immunologic disease can be suppressed or controlled, and long-term self-maintained remissions may be expected.

The graft versus leukemia (GVL) effect after allogeneic bone marrow transplantation for chronic myelogenous leukemia (CML)

Immune mechanisms superimposed to the myeloablative conditioning regimens exert an additional powerful effect in eradicating leukemia and in achieving immunological control of minimal residual disease. The impact of GVHD-independent GVL has been evaluated to be absent, or near absent, in ALL, about 30% in AML and about 40% in CML. While until little time ago most of the evidence in favor of an immune antileukemia mechanism exerted by allo BMT in CML was indirect, based on the lack of GVL, there is now solid evidence of a positive type, based on the antileukemia effect of donor lymphocyte infusions in patients having relapsed after transplant. There are three lines of indirect clinical evidence for GVL in CML: they include the classical linkage between GVHD and reduced relapse rate, increased relapse rate after identical twin allografts, and increased relapse risk after effective GVHD prophylaxis, with T lymphocyte depletion in the foreground. The eradicating effects of donor lymphocyte infusions in relapsed patients are the ultimate demonstration that allogeneic immune competent cells are capable of recognizing and destroying the Ph-positive clone. However the frequency of irreversible aplasia indicates that donor lymphocytes act in the same way on residual host hematopoiesis, so that a second graft, without repeat conditioning, should be programmed for such cases.