Long-term lymphoid-restricted split chimerism after myeloablative aUogeneic BMT for bcr-abl+ ALL

摘要

Allogeneic BMT results in true biological chimeras. In most cases, the procedure leads to complete donor chimerism, which refers to complete replacement of host by donor lympho-hematopoiesis. Mixed chimerism (MC) indicates the presence of both donor and recipient hematopoietic cells, and its presence depends on several factors such as intensity of the conditioning regimen, T-cell content of the graft, GVHD prophylaxis and underlying disease.1 MC may be efficiently induced in non-malignant genetic disorders, such as marrow failure syndromes and hemoglo-binopathies, and this may be enough to reverse the clinical consequences of inborn errors. MC in leukemia patients is a strong indicator of relapse, especially when it is observed after myeloablative conditioning and when MC reveals an increasing number of recipient cells over time.2 However, long-term MC without relapse has also been described in leukemia patients treated with myeloablative conditioning.3"5 Schaap et al? identified 19 leukemia patients with persisting (>2 years) MC among 231 transplanted patients. The number of recipient cells in peripheral blood did not exceed 15% in a group of 10 patients, whereas the other 9 patients had a relatively high percentage of persisting autologous cells for a median of 12 years#