Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0002874 (aplastic anemia)
 5,905 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The high-proliferative-potential colony-forming cell (HPP-CFC) has been shown to be clearly heterogeneous. Hierarchical subpopulations can be identified by analyzing the kinetics of cell regeneration and the specific cellular requirement for cytokines. In this study, a new type of HPP-CFC, termed high-proliferative potential mixed colony-forming unit-megakaryocyte (HPP-mCFU-MK), was detected in murine bone marrow cell cultures. The HPP-mCFU-MK was able to form macroscopic colonies that fit the criteria of the HPP-CFC colony but contained a number of megakaryocytes. Its growth was stimulated by either aplastic anemia serum (AAS) or a combination of three or more recombinant hematopoietic growth factors but was not inhibited by transforming growth factor-beta 1 (TGF-beta 1) and platelet factor 4 (PF4) in vitro. The recloning of the 12-day-old HPP-mCFU-MK colonies picked up from AAS-stimulated primary cultures caused secondary formation of HPP-CFC colonies. These data suggest that HPP-mCFC-MK is a new subset of stem cell characterized by its ability to produce directly a number of megakaryocytes in response to multifactor stimulation, to generate a secondary set of HPP-CFC in replating culture, and to be unaffected by TGF-beta 1 and PF4 treatment.
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PMID:Identification of a murine high-proliferative-potential colony-forming cell (HPP-CFC) capable of producing a number of megakaryocytes and replating for secondary HPP-CFCs in culture. 814 10

The hematopoietic growth factors stem cell factor (SCF) and flt3 ligand (flt3L) are produced within the hematopoietic microenvironment in a membrane-bound and soluble isoform. To elucidate the relevance of the two isoforms in the network of early-acting cytokines, we examined the interaction of membrane-bound SCF with the soluble forms of SCF and flt3L in long-term cultures of human bone marrow cells. Feeder layers of the murine SCF-deficient Steel stromal cell line transfected with human cDNA stably expressing SCF as a transmembrane molecule were used to support growth of mononuclear cells and CD34+ progenitors derived from normal human bone marrow or from hypoplastic marrow of patients with aplastic anemia (AA). The output of nonadherent progenitor cells representing colony-forming units (CFU) and high-proliferative potential colony-forming cells (HPP-CFC) was scored weekly in secondary methylcellulose cultures; the number of colonies derived from long-term culture-initiating cells (LTC-IC) was determined in nonadherent and adherent cells at 5 weeks. Membrane-bound SCF expressed in the stromal layer was more effective than soluble SCF and soluble flt3L in maintaining clonogenic progenitors. Furthermore, the transmembrane form of SCF effectively synergized with both exogenously supplied factors, although the effect of flt3L was superior to the effect of soluble SCF. In cultures of normal bone marrow cells, addition of flt3L enhanced the total number of CFU and HPP-CFC-type progenitors, primarily of the granulocyte/macrophage lineage, by six- to ninefold after 3 weeks and of LTC-IC-derived colonies by 13-fold after 5 weeks of culture. In cultures of AA cells, both the number and the survival rate of clonogenic precursors were severely impaired even in the presence of flt3L, which, however, yielded a two- to sixfold enhancement of CFU and HPP-CFC numbers at 1 to 2 weeks. In comparison with the hematopoietic function of human Dexter-type stroma cultures, murine feeders expressing high levels of membrane-associated human SCF were equivalent in supporting hematopoiesis during the initial 3 to 4 culture weeks when supplemented with flt3L. These results demonstrate that soluble flt3L interacts with membrane-bound SCF in supporting the long-term growth of bone marrow progenitor cells. The hypothesis that SCF and flt3L function synergistically during the very early stages of human hematopoiesis is thereby reinforced.
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PMID:The membrane-bound isoform of stem cell factor synergizes with soluble flt3 ligand in supporting early hematopoietic cells in long-term cultures of normal and aplastic anemia bone marrow. 959 Jun 52

Engraftment failure following allogeneic bone marrow (BM) transplantation is of clinical concern particularly involving T-cell-depleted inoculum and transplantations for aplastic anemia. Immune resistance by lymphoid and natural killer (NK) populations with "barrier" function is well established. Major histocompatibility complex (MHC)-identical marrow allografts were examined to investigate effector pathways in non-NK-mediated resistance. Barrier function was examined in cytotoxic normal and deficient B6 (H-2(b)) recipients primed to donor minor histocompatibility antigen (MiHA) prior to BM transplantation. Host resistance was sensitively evaluated by colony-forming unit (CFU) assays to directly assess for donor progenitor cell (PC) and peripheral chimerism. B6 host CD8(+) T cells but not CD4(+) or NK1.1(+) cells effected rejection of primitive (CFU-HPP [high-proliferative potential]) and lineage-committed (CFU-IL3/GM [interleukin 3/granulocyte macrophage]) allogeneic donor progenitors. To address complementation by the cytotoxic pathways existing in singly deficient (perforin or FasL) recipients, cytotoxically double (perforin plus FasL) deficient (cdd) recipients were used. Resistance in B6-cdd recipients was comparable to that of wild-type B6 recipients and was also dependent on CD8(+) T cells. A "triple" cytotoxic deficient model, involving transplantation of TNFR1(-/-) (tumor necrosis factor receptor 1) progenitor grafts did not diminish the ability of B6-cdd recipients to reject allografts. Finally, injection of anti-TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) monoclonal antibody (mAb) in B6-cdd recipients also failed to inhibit rejection of TNFR1(-/-) marrow grafts. In total, these studies demonstrate that CD8(+) host T cells can effectively resist MHC-matched MiHA-mismatched donor PCs via alternative effector pathway(s) independent of perforin-, FasL-, TNFR-1-, and TRAIL-dependent cytotoxicity. Therefore, inhibition of these effector pathways in sensitized recipients is unlikely to result in stem cell engraftment following PC allografts.
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PMID:Antigen-primed CD8+ T cells can mediate resistance, preventing allogeneic marrow engraftment in the simultaneous absence of perforin-, CD95L-, TNFR1-, and TRAIL-dependent killing. 1252 99