Suppression of stem cells.
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Biomedical subjects
Publications and source records attributed to M J Cline.
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The ability of syngeneic peripheral leucocytes to cure marrow aplasia was tested in a patient with paroxysmal nocturnal haemoglobinuria (P.N.H.). Transfusion of 7.1X10(10) white cells obtained by leucopheresis from an identical-twin donor, providing 3.4X10(4) myeloid progenitors (C.F.U.-C)/kg, failed to improve marrow function within two months. In contrast, transfusion of 1.3X10(10) nucleated bone-marrow cells, representing 6.4X10(4) C.F.U.-C/kg, from the same donor resulted in prompt bone-marrow recovery. These observations support the hypothesis that aplastic anaemia in P.N.H. is a stem-cell defect that may be corrected by the simple infusion of relatively small numbers of normal bone-marrow cells. They also seem to indicate a distinct advantage of marrow cells over peripheral-blood mononuclear cells in their ability to correct marrow aplasia.
In vitro culture of haematopoietic cells has provided some surprising insights into critical interactions of blood-forming cells. Subpopulations of lymphoid cells have been shown to produce colony-stimulating activity, to interact with macrophages, and to have important effects on the very early stages of erythropoiesis. Macrophages have multiple influences on the proliferation and differentiation of other haematopoietic cells.
Human peripheral blood contains two types of stem cells that differentiate along the granulocytic pathway. They are separable by their ability to form colonies in agar in vitro (CFU-C) and in plasma clots in diffusion chambers in vivo (CFU-DG). Kinetic studies suggest that CFU-DG represents an intermediate between the still hypothetical human pluripotent stem cell and CFU-C.
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We have investigated the mechanism of splenic irradiation-induced granulocytopenia in two patients with myelofibrosis and marked splenomegaly. Serial assays were performed for circulating granulocyte-monocyte progenitors capable of colony formation in vitro (CFU-C). For comparison, similar studies were performed on two patients receiving whole brain irradiation for glioma. Splenic irradiation caused a significant decrease in circulating CFU-C in the myelofibrosis patients. There was no decrease in circulating CFU-C in the brain-irradiated patients. No radiation-induced humoral inhibitor of granulopoiesis and no increased CFU-C radiosensitivity could be demonstrated in the myelofibrosis patients. These observations, taken together with previous data on splenic blood flow and pooling, suggest that the major mechanism of irradiation-induced granulocytopenia in myelofibrosis is destruction of proliferating precursor cells in the splenic tissue and sinusoids.
Both murine and human bone marrow cells were cultured in plasma clots which were formed inside diffusion chambers implanted into cyclophosphamide- and saline-treated mice. After an initial fall, the number of mouse bone marrow cells and numbers of mouse myeloid stem cells (CFU-C) and agar cluster-forming units rose faster in the cyclophosphamide-treated animals. These hosts also favored formation of myeloid (CFU-D-G) and erythroid (CFR-D-E) colonies and myeloid higher than those of CFU-C from the same marrow population. These observations suggest the existence of humoral factors stimulating granulocyte progenitor cell replication and differentiation. At its best the increment of CFU-D-E number was equivalent to that caused by a single 0.1 unit erythropoietin dose. Culture of normal human marrow cells resulted in colonies in the plasma clot containing only granulocytes and macrophages. Cyclophosphamide-treated host animals were essential for human CFU-D-G development. Plating efficiency for human marrow myeloid colonies was better in the conventional in vitro agar cultures than in diffusion chambers.
The development since 1966 of a technology for growing stem cells in vitro has provided new insights into the controls of blood cell production. Hematopoietic hormones have been purified and important cellular interactions in hematopoiesis have been defined.
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We have used in vitro immunotherapy before autologous bone marrow transplantation for three patients with acute lymphoblastic leukemia (ALL). Bone marrow was removed during remission, and mononuclear cells were separated by density-step centrifugation on Ficoll-Hypaque. The cells from each patient were treated with a heteroantiserum and complement to eliminate leukemic cells and were cryopreserved. Following chemotherapy and total body irradiation, the treated marrows were thawed and infused. All the patients showed positive evidence of returning marrow function before death. One patient who survived 4 months showed no evidence of leukemia at post mortem, and marrow sections demonstrated active hematopoiesis of all cell lines.
Recent studies using cytotoxic and cell separation techniques have identified differentiation-related antigens on human hematopoietic cells. These results, combined with bone marrow transplantation studies, have yielded a picture of antigenic modulation from the pluripotent hematopoietic stem cell through the differentiated end cells.
Ten patients with non-leukemic neoplasms received intensive, marrow-lethal doses of drugs and radiation followed by rescue with autologous cryopreserved bone marrow (nine) or marrow from an identical twin as part of a phase 1-2 study. Nine patients had extensive disease that was unresponsive to conventional therapy. Marrow engraftment was documented in all evaluable cases and most patients had a substantial anti-tumor response. Three patients are alive from 4 to 10 months following transplantation without evidence of disease.
Marrow cells of known HLA type were incubated with HLA antiserum plus complement and then plated in soft agar. Colony formation was consistently inhibited by appropriate HLA antisera. Mixing experiments excluded an indirect effect on CFU-C by lysis of mature leukocytes. We conclude that human CFU-C express HLA antigens.
We have used cryopreserved autologous hematopoietic cells to repopulate bone marrow of patients receiving intensive chemotherapy and radiation. We employed the technique of density step centrifugation to concentrate stem cells from whole bone marrow. The concentrate of cells was frozen in vials using dimethyl sulphoxide (DMSO) as a cryo-protective agent and was stored in the vapor phase of liquid nitrogen. Test vials were thawed and assayed for myeloid stem cells (CFU-C) to determine the potential of the larger marrow aliquot. These test values were compared to the recovery of cells and CFU-C when the marrow was used for autotransplantation. The return of hematopoietic function after autotransplantation was evaluated and correlated with the dosage of cells and CFU-C infused.
A correlation was demonstrated between bone-marrow graft rejection and pretransplant lymphocytotoxins. This finding might prove useful as a test for identification of patients at high risk of rejection who might benefit from more intensive immunosuppression.
A patient with poorly differentiated monocytic malignancy had extensive lytic lesions of bone and hypercalcemia. The patient's bone margins showed little evidence of osteoclast activity. Serum parathormone concentrations were slightly increased relative to the degree of hypercalcemia, consistent with impaired renal function. Serum concentrations of the relevant prostaglandins were normal. Supernatant medium from cultured tumor cells caused prominent bone resorption in vitro. The studies on this patient provide evidence that malignant cells of the monocyte-macrophage line are capable of direct bone resorption.