Erythropoiesis following bone marrow transplantation from donors heterozygous for beta-thalassaemia.

This study shows a marked and protracted activation of HbF synthesis in homozygous beta.-thalassaemia patients transplanted from HLA identical siblings heterozygous for beta-thalassaemia, as compared to patients transplanted from normal donors. HbF synthesis in recipients was much higher in relation to the corresponding bone marrow donor values either normal or heterozygous for beta thalassaemia. gamma-chain synthesis and G gamma/A gamma ratio were also studied in peripheral blood BFU-E from recipients and their donors. BFU-E from donors heterozygous for beta-thalassaemia showed higher gamma chain synthesis as compared to normal donors. Peripheral blood BFU-E gamma/beta + gamma ratios and G gamma percentage were higher in recipients than in their corresponding donors both normal or heterozygotes. The marked and protracted reactivation of HbF synthesis in recipients of heterozygous beta-thalassaemia bone marrow most likely results from an increased erythropoietic stress on erythroid progenitors. In order to obtain adequate Hb levels heterozygous beta-thalassaemia bone marrow should produce more red blood cells to compensate for the low MCH. The magnitude of activation of HbF synthesis was very variable. This variability may result from inherited differences in the capacity of reactivation of HbF synthesis of red cell progenitors from heterozygous beta-thalassaemia under stressed erythropoiesis.