Hemopoietic reconstitution after bone marrow transplantation.

Forty-one patients underwent bone marrow transplantation (BMT) for treatment of severe aplastic anemia or hematologic malignancies. Hemopoietic reconstitution after BMT was monitored by peripheral blood counts, counts of bone marrow cellularity, and clonal assays for hemopoietic progenitors (CFUc, CFUe, and BFUe), along with bone marrow morphology. The number of transplanted nucleated cells and the number of transplanted progenitors (CFUc, CFUe, and BFUe) correlated significantly with the time of reticulocyte recovery. The number of transplanted CFUc correlated significantly with the time of granulocyte recovery. Platelet recovery occurred late and showed large variations. No correlation between the transplanted cells and the recovery of nucleated cells or hemopoietic progenitors (CFUc, CFUe, and BFUe) in the bone marrow was found. Bone marrow cellularity and hemopoietic progenitors showed a rapid, but incomplete, recovery during the first 56 days after BMT. Hematologic studies on seven long-term survivors with an uncomplicated posttransplantation course revealed subnormal bone marrow cellularity and hemopoietic progenitor incidence up to three years after BMT, despite normal peripheral blood counts. The low progenitor incidence could be explained by a proliferative defect of the stem cells, compensated for by an amplification in the more differentiated compartment of hemopoiesis.