Relevance of colony forming assays to bone marrow transplanation with particular reference to grafting for aplastic anaemia

Hematologic aspects of myeloablative therapy and bone marrow transplantation

The transplantation of bone marrow cells or isolated hematopoietic stem cells from the bone marrow or peripheral blood is a widely utilized form of therapy for patients with incurable diseases of the hematopoietic and immune systems. Successful engraftment of the transplanted stem cells in an adequately prepared recipient normally leads to bone marrow reconstitution over a period of several weeks, accompanied by more gradual reconstitution of the immune system. Since the recipient is profoundly ill during the initial treatment period, laboratory data is critical for monitoring engraftment, detecting residual/recurrent disease, and identifying problems that may delay bone marrow reconstitution or lead to other medical complications. Accurate blood cell counts are imperative, and most bone marrow transplantation patients undergo periodic monitoring with bone marrow aspirates and biopsies with cytogenetic, molecular, and multiparametric flow cytometric studies. The potential complications of bone marrow transplantation include engraftment failure and delayed engraftment, infection, residual bone marrow disease, acute and chronic graft versus host disease, myelofibrosis, therapy-related acute leukemia, post-transplant lympho-proliferative disorders, and toxic myelopathy.

Increased expression of Fas (APO-1, CD95) on CD34+ haematopoietic progenitor cells after allogeneic bone marrow transplantation

Up-regulation of Fas/APO-1 (CD95) on haematopoietic progenitors and Fas-mediated apoptosis have been suggested to occur in a possible pathological mechanism in some bone marrow failure syndromes. We examined the expression of Fas antigen and susceptibility to Fas-mediated suppression of donor-derived haematopoietic cells of allogeneic bone marrow transplantation (BMT) recipients. Cytofluorometric analysis revealed low expression of Fas on CD34+ bone marrow cells from marrow donors or healthy controls. However, significantly higher expression of Fas antigen was observed on CD34+ bone marrow cells of BMT recipients, in whom engraftment of donor bone marrow (BM) cells was confirmed. The addition of an agonistic anti-Fas antibody (Ab) (CH-11) to haematopoietic stem cell culture of BM cells more strongly suppressed colony formation from granulocyte-macrophage colony-forming units (GM-CFU) and erythroid burst-forming units (BFU-E) after BMT. Pretreatment by blocking anti-Fas Ab (ZB4) abrogated the Fas-mediated GM-CFU and BFU-E suppression. Purified marrow CD34+ cells from BMT recipients were also susceptible to the Fas-mediated colony suppression. Thus, donor-derived CD34+ haematopoietic cells increased their expression of Fas antigen and were susceptible to Fas-mediated haematopoietic suppression. These findings provide new insight for understanding the haematological condition after BMT.

A comparison between regimens containing chemotherapy alone (busulfan and cyclophosphamide) and chemotherapy (V. RAPID) plus total body irradiation on marrow engraftment following allogeneic bone marrow transplantation

The effect of two conditioning regimens given prior to allogeneic bone marrow transplantation (BMT) on the kinetics of engraftment were compared. 5 patients received busulfan and cyclophosphamide: 7 patients received daunorubicin, vincristine, cytosine arabinoside, methylprednisone and VM-26 plus total body irradiation (TBI). Bone marrow progenitors (BFU-E, CFU-E, CFU-GM, CFU-F) were assayed up to 3 months post-BMT. All progenitors were severely depressed in spite of peripheral blood recovery. There was no stromal recovery in any adult patient post-BMT. There was no significant difference in time to engraftment, or colony forming units, or between patients conditioned with chemotherapy alone or chemotherapy plus TBI. We were unable to detect effects of graft-versus-host disease or cytomegalic viral infection on bone marrow progenitors or peripheral blood recovery in this study.

Hematopoietic factors in graft-versus-host reaction

Graft-versus-host (GVH) reaction has a curious unsolved area in the immunopathogenesis and pathophysiology of the immunohematopoietic system, and GVH disease remains one of the major obstacles in clinical allogeneic bone marrow transplantation. T lymphocytes and T lymphocyte subpopulations are now recognized to be initiators of this GVH reaction and disease. Also, T lymphocytes are known to be accessory cells in the regulation of hematopoiesis, and produce a variety of lymphokines relevant to hematopoiesis. Admittedly, remarkable hematopoietic changes can be found in GVH reaction, but the cellular mechanisms underlying these changes are so complex they have yet to be fully elucidated. In fact, elevated serum levels of myeloid and erythroid colony-stimulating activities were found in mice suffering from GVH disease in which marked granulopoiesis and suppression of erythropoietic differentiation were seen. In addition, each granulocyte/macrophage colony-stimulating factor (GM-CSF) or burst-promoting activity (BPA) could be detected in sera from patients with GVH disease following allogeneic bone marrow transplantation. There seems to be at least two mechanisms involved in the control of hematopoiesis with either humoral or local environmental factor, probably via the T lymphocytes or T lymphocyte subpopulations activated by alloantigens or autologous non-T cells.

Complement-dependent hematopoietic inhibitors in the sera of patients with aplastic anemia and paroxysmal nocturnal hemoglobinuria

The sera of 14 out of 48 patients with aplastic anemia and four out of nine patients with paroxysmal nocturnal hemoglobinuria (PNH) contained complement-dependent hematopoietic inhibitory activity against allogeneic marrow progenitor cells. Some sera with hematopoietic inhibitory activity, however, demonstrated no effect on autologous marrow progenitor cells. Hematopoietic inhibitory activity was absorbed by pooled, packed platelets. Serum hematopoietic inhibitory activity was present in both IgM and IgG fractions. These data suggested that serum hematopoietic inhibitors are alloantibodies and might be associated with graft rejection in the transplanted marrow of patients with aplastic anemia and PNH.

Haemopoietic reconstitution after allogeneic bone marrow transplantation in man: recovery of haemopoietic progenitors (CFU-Mix, BFU-E and CFU-GM)

Haemopoietic reconstitution was evaluated in 44 patients given HLA compatible sibling bone marrow transplants. The mean peripheral blood haemoglobin, neutrophil and platelet counts were markedly reduced early post-graft but returned to normal by 26 weeks post transplant. Bone marrow multipotent (CFU-Mix), erythroid (BFU-E) and myeloid (CFU-GM) progenitor cell reconstitution were also assessed at regular intervals up to 2 years post-graft. The mean value of CFU-GM increased gradually and attained a normal value by 52 weeks. The BFU-E value did not reach a normal value until after 52 weeks post-graft. However, CFU-Mix growth appeared to be impaired even up to 2 years post-transplant. The occurrence of graft versus host disease at 3 months post-transplant was associated with significantly lower mean numbers of platelets, marrow CFU-GM, BFU-E and CFU-Mix. Post-transplant patients who were on methotrexate therapy were also shown to have lower marrow CFU-GM and neutrophil values compared to those patients who received cyclosporin post-transplant. This study demonstrated that although peripheral blood counts were normal after 26 weeks post-graft, marrow stem cell reserve in these patients was reduced. This might in part explain the documented increase in risk of severe infections or thrombocytopenia in some of these patients, particularly during viral infection, graft-versus-host disease or immunosuppressive treatment.

Hemopoietic progenitor cell function after HLA-identical sibling bone marrow transplantation: influence of chronic graft-versus-host disease

We examined hemopoietic reconstitution during the first 12 months post-transplant in 31 patients given high-dose cyclophosphamide, total body irradiation and an HLA-identical sibling marrow transplant for hematological malignancy. Unexpectedly, we found marrow CFU-gm and marrow CFU-e cells to be denser than normal throughout the first year post-transplant. While functionally adequate neutrophil and platelet counts were achieved in the first six weeks post-transplant, there were defects in hemopoietic progenitor cell function during the first year post-transplant. Although we could detect no influence from acute graft-versus-host disease (GVHD), chronic GVHD adversely affected the growth of both myeloid and erythroid blood progenitor cells.

Drug-induced aplastic anaemia and agranulocytosis. Incidence and mechanisms

Aplastic anaemia and agranulocytosis are uncommon but serious adverse effects of drug therapy. They result from an adverse interaction between the drug and the haemopoietic pathway in certain susceptible individuals. The nature of this idiosyncratic interaction differs for different drugs and possibly for different individuals. In some instances an immune mechanism might be implicated, in others the patient's cells might carry a genetic susceptibility to the drug, while yet other patients might metabolise the drug abnormally. The idiosyncratic nature of these effects has made their investigation difficult, but experimental studies have allowed some progress in our understanding. In a practical sense, however, responsibility for preventing these problems will remain with clinicians, who should be alert to the risks and revise their prescribing habits accordingly.

A proliferative defect of human bone marrow after transplantation

A technique which permits proliferation of CFU-C or their precursors is described. Bone marrow cells from 10 normal donors showed an increase over a 2 week culture period of total nucleated cell counts, and of granulocyte colony and cluster forming cells. During culture an adherent layer of fibroblasts and monocyte-macrophage cells formed. Bone marrow from eight patients taken between 2 weeks and 2 years after marrow transplantation did not show CFU-C proliferation or increase in total cell counts in culture. This difference did not appear to be due to changes in the adherent cell layer formation, and suggests that grafted human bone marrow shows a proliferative defect similar to that described in mouse transplantation models.