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The hematopoietic system is derived from ventral mesoderm. A number of genes that are important in mesoderm development have been identified including members of the transforming growth factor-beta (TGF-beta) superfamily, the fibroblast growth factor (FGF) family, and the Wnt gene family. Because TGF-beta plays a pleiotropic role in hematopoiesis, we wished(More)
The possible pathogenetic mechanisms responsible for the production of acquired amegakaryocytic thrombocytopenic purpura (AATP) were investigated in a group of patients with this disorder. Absence of megakaryocytes and small platelet glycoprotein-bearing mononuclear cells, as determined by immunochemical staining of patient marrows with an antisera to(More)
An evaluation of the effects of a recombinant, soluble form of the c-kit ligand alone and in combination with either granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3) on the regulation of human megakaryocytopoiesis was performed using a serum-depleted clonal assay system and a long-term bone marrow culture system. The effects(More)
Hematopoietic stem cell (HSC) self-renewal in vitro has been reported to result in a diminished proliferative capacity or acquisition of a homing defect that might compromise marrow repopulation. Our group has demonstrated that human HSC expanded ex vivo in the presence of porcine microvascular endothelial cells (PMVEC) retain the capacity to competitively(More)
We have used a combination of hematopoietic growth factors to induce in vitro granulocytic maturation. A fraction of marrow cells enriched for hematopoietic progenitor cells (CD34+, HLA-DR+) was isolated from normal human bone marrow by monoclonal antibody staining and fluorescence-activated cell sorting. Cells were cultured in a suspension system for 3(More)
Parvovirus B19 infection leads to transient aplastic crises in individuals with chronic hemolytic anemias or immunodeficiency states. An additional unexplained sequela of B19 infection is thrombocytopenia. Because B19 is known to have a remarkable tropism for human erythropoietic elements, and is not known to replicate in nonerythroid cells, the etiology of(More)
The effects of human recombinant interleukin 6 (rIL-6) on in vitro human megakaryocytopoiesis were studied utilizing a serum-depleted culture system. Recombinant IL-6 increased both the number of megakaryocyte (MK) colonies formed and the number of cells comprising individual MK colonies cloned from normal low-density bone marrow (LDBM) cells. This(More)
The c-kit ligand or stem cell factor (SCF) and the c-kit ligand receptor (KR) are thought to play pivotal roles in the regulation of human hematopoiesis. When added to interleukin 3 (IL-3) and/or granulocyte-macrophage colony stimulating factor (GM-CSF), SCF has an especially profound effect on the in vitro proliferation of several classes of primitive(More)
We have investigated the expression of CD41a (gpIIbIIIa) on a subpopulation of human fetal bone marrow (FBM) CD34+ progenitor cells. Human FBM CD34+Lin- cells were subfractionated into CD41a+ and CD41a- subpopulations by flow cytometry. All the megakaryocyte colony-forming cells (CFU-MK) and almost all the burst-forming units-megakaryocyte (BFU-MK) were(More)