THE MECHANISMS INVOLVED IN THE IMPAIRMENT OF HEMATOPOIESIS AFTER AUTOLOGOUS BONE-MARROW TRANSPLANTATION

Hematopoiesis after autologous bone marrow transplantation (BMT) is ch aracterized by a prolonged and severe deficiency of marrow progenitors for several years, especially of erythroid and megakaryocyte progenit ors, while the peripheral blood cells and marrow cellularity have reac hed relatively normal values within a few weeks. These anomalies are c omparable to those reported for allogeneic BMT, despite the absence of any allo-immune reaction or post-graft immunosuppressive therapy. Pos t-graft hematopoietic impairment is the consequence of quantitative an d qualitative changes involving both stem cell and stromal compartment s which are expressed by an impaired capacity of stem cell self-renewa l and commitment towards erythroid and megakaryocytic lineages. Beside s the toxicity of conditioning regimens, hematopoietic reconstitution using autologous grafts is particularly dependent on a combination of factors related to the patient, such as underlying disease and pre-gra ft chemotherapy regimens, and to the graft processing itself, such as in vitro purging with chemotherapeutic agents.