Transplantation haemopoiesis. Morphological bone marrow studies after allogeneic marrow transplantation in man for severe aplastic anaemia and acute leukaemia.

Bone marrow (BM) morphology was studied in patients who underwent bone marrow transplantation (BMT) for severe aplastic anaemia (SAA) and acute myeloid leukaemia (AML). Four patients with SAA had marrow transplanted from HLA-identical siblings after conditioning with cyclophosphamide (CY); three cases of AML were treated with allogeneic BMT. The medullary material was generally obtained by aspiration, but treated so as to preserve its architecture; fresh, postvital preparations were particularly useful for this purpose. In SAA, the bone marrow before transplantation showed dense infiltrates composed of macrophages and other inflammatory cells; after BMT, repopulation started at the periphery of the infiltrates, when they were not totally destroyed by CY. Granulocytic repopulation generally preceded erythropoiesis, which always occurred by way of typical erythroblastic reticulocytopoietic islands. Marked but transient dyserythropoiesis was found in two cases; in one of them, it was considered as drug-dependent. Both in SAA and in AML, but more so in the latter, a marked and sometimes imposing macrophagic hyperplasia was found after transplantation. Many macrophages were actively engulfing erythrocytes and nucleated cells. This last type appeared prominent in rejection episodes.