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 family of colony stimulating factors and interleukins influence all aspects of hematopoietic cell proliferation and differentiation. In most instances these hematopoietic growth factors have overlapping, pleiotropic effects and frequently regulate early progenitor cell proliferation and mature cell function. Currently, seven of these factors are in clinical trial: erythropoietin for treatment of anephric anemia, IL-2 in conjunction with LAC therapy, and IL-1, IL-3, G-CSF, GM-CSF, and M-CSF for stimulation of myelopoiesis and granulocyte-macrophage function after chemotherapy, irradiation, or bone marrow transplantation in patients with cancer. G-CSF and GM-CSF have also proved effective in treatment of congenital and idiopathic neutropenias and have had some efficacy in treatment of myeloid leukemias, myelodysplastic disorders, aplastic anemia, and acquired immunodeficiency syndrome (AIDS).
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PMID:Hematopoietic growth factors in cancer. 240 5

The effects of benzene and its metabolites, hydroquinone and p-benzoquinone (PBQ) on RNA synthesis in mouse spleen lymphocytes in vitro were studied. Benzene and the quinones were shown to inhibit RNA synthesis in a dose-dependent manner at concentrations which had no significant effect on lymphocyte viability. Furthermore, 5 microM PBQ, the putative toxic metabolite of benzene, was shown to inhibit the formation of the T-cell growth factor IL-2. These results suggest that inhibition of RNA synthesis in lymphocytes by benzene may prevent the production of factors required for hemopoiesis and thus contribute to the aplastic anemia caused by benzene.
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PMID:Inhibition of RNA synthesis and interleukin-2 production in lymphocytes in vitro by benzene and its metabolites, hydroquinone and p-benzoquinone. 241 39

Apart from autoimmune reactions, antibodies to IL-2 receptors were identified in blood sera of linear mice during leukemogenesis. It is indicated that in the course of leukemia establishment, there can be demonstrated antibodies capable of blocking IL-2 receptors on the membrane of activated T lymphocytes and inhibiting IL-2-dependent proliferation of T cells. The blood sera of patients suffering from chronic lymphoid leukemia, acute lymphoblastic leukemia, lymphocytomas, pure red-cell aplasia, and aplastic anemia showed antibodies against IL-2 receptors. Out of the total number of 52 patients, 23 demonstrated those antibodies. The data obtained should be taken into account in the patients' management using IL-2.
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PMID:[Autoimmune reactions against interleukin-2 receptors in patients with blood system diseases and in experimental Rauscher retrovirus leukemia]. 258 42

In order to maintain adequate circulating numbers of blood cells, the bone marrow must produce billions of cells each day and must be able to rapidly increase production by 10-20-fold in response to infection and hemorrhage. The existence of circulating factors that regulate this process has been suspected for over 100 years. Recently, the genes encoding these growth factors were cloned and their functions are now identified. Interleukin-3 (IL-3) acts on the most primitive hematopoietic stem cell, driving this self-renewing cell to produce progeny of all hematopoietic lineages. Granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulates the granulocyte-macrophage progenitor cell, as well as cells committed to the erythroid lineage, to differentiate. G-CSF and M-CSF stimulate the most differentiated myeloid progenitors to produce granulocytes and monocytes/macrophages, respectively. Erythropoietin stimulates the differentiation of late erythroid progenitors. In the lymphoid progenitor lineage, IL-2 stimulates T cell differentiation; IL-4 and IL-6 stimulate differentiation of B cells. The colony-stimulating factors also enhance function and cause activation of the mature cells whose production they induce. In clinical trials, these hormones have successfully ameliorated anemia in renal failure, chronic disease, and in prematurity. They have improved pancytopenias in aplastic anemia, myelodysplastic syndromes, and congenital cytopenias, and they have hastened recovery from chemotherapy and bone marrow transplantation.
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PMID:Hematopoietic hormones: from cloning to clinic. 267 59

Allogeneic bone marrow transplantation (BMT) was applied in 1968 to treat severe combined immunodeficiency disease (SCID). Almost simultaneously, marrow from an MHC-matched donor corrected the immunological deficiency of a patient with Wiscott-Aldrich Syndrome (WAS). In the first successful treatment of X-linked SCID the match was imperfect and, although SCID was cured, a graft vs. host reaction caused pancytopenia. A second BMT from the same donor successfully treated a complicating aplastic anemia. Subsequently, it has been possible to cure most patients with SCID who are in reasonably good condition at the time of BMT without other manipulation if a matched sibling donor is available. Successes are reported from Holland, France, Italy, England, Scandinavia, Japan, Germany, and from many centers in the United States. Similarly, BMT is used to correct SCID due to adenosine deaminase (ADA) deficiency or nucleoside phosphorylase (NP) deficiency, which underlie two forms of SCID. Bone marrow transplantation using HLA-matched sibling donors can now treat, successfully, at least eight genetically separable forms of SCID. Highly lethal defects of phagocytic function (including LFA-1, MO-1, CR-3 deficiencies, IL-2 and IL-1 receptor deficiencies), defects of killing after phagocytosis (as in chronic granulomatous disease, WAS, and Kostmann's Syndrome), and certain inborn errors of metabolism can be cured by BMT.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Bone marrow transplantation for immunodeficiency diseases. 330 7

Cytokine is a generic term of biologically active molecules which are mainly produced by the immune-competent cells and regulate the immune response, inflammation and hematopoiesis. This includes interleukins (IL), colony-stimulating factors (CSF), interferons (IFN), tumor necrosis factors (TNF) and so on. These cytokines are glycoproteins with a molecular weight of 20,000-40,000 kD and work at very low concentrations of pM order. ILs and CSFs transduce their signal via specific cell-membrane receptors which usually consist of at least two subunits and belong to a newly identified superfamily of cytokine receptors. Characterization of cytokine/receptor system has had a considerable impact on many clinical fields including pathophysiology of diseases and therapy. For example, IL-4 and IL-5 has been revealed to play essential roles in IgE production in allergic diseases and eosinophilia in a hypereosinophilic syndrome, respectively. Receptor abnormality has also been proven to cause diseases; patients for X-linked severe combined immunodeficiency (X-SCID) have a specific defect in the gamma chain of the IL-2 receptor which is critical for thymic maturation of T cells. EPO, G-CSF, M-CSF, IFN, and IL-2 are already commercially available for therapeutic use. IL-1, IL-3, IL-6, and TNF may also be useful for mycosis fungoides, aplastic anemia, thrombocytopenia, and malignant melanoma, respectively. On the other hand, it is possible to modulate the immune response by using the monoclonal antibody directed to the cytokine receptor.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Cytokine and disease]. 752 45

Severe aplastic anemia (SAA) has been related in most cases to underlying autoimmune conditions. Various immunosuppressive regimens have been recommended in the absence of an HLA-identical bone marrow donor. Prednisolone, antithymocyte globulin, and cyclosporin A have been shown to be effective. This report describes the successful treatment of a 23-year-old woman suffering from severe aplastic anemia who had become multiresistant against previously administered immunosuppressive agents, using a monoclonal IL-2-receptor blocking antibody. The patient responded within 4 weeks. The time to the next relapse was 8 months; however, another remission with a second course of horse-antithymocyte globulin was achieved and has been maintained for 27 months to date with low doses of cyclosporin A. Although this is an anecdotical report, IL-2-receptor blockade using a monoclonal antibody might be considered as a further alternative in multi-resistant SAA, perhaps increasing the susceptibility to further immunosuppressive trials.
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PMID:Treatment of aplastic anemia with a monoclonal antibody directed against the interleukin-2 receptor. 848 6

Polyclonal horse antilymphocyte and rabbit antithymocyte globulins (ATGs) are currently used in severe aplastic anemia and for the treatment of organ allograft acute rejection and graft-versus-host disease. ATG treatment induces a major depletion of peripheral blood lymphocytes, which contributes to its overall immunosuppressive effects. Several mechanisms that may account for lymphocyte lysis were investigated in vitro. At high concentrations (.1 to 1 mg/mL) ATGs activate the human classic complement pathway and induce lysis of both resting and phytohemagglutinin (PHA)-activated peripheral blood mononuclear cells. At low, submitogenic, concentration ATGs induce antibody-dependent cell cytotoxicity of PHA-activated cells, but not resting cells. They also trigger surface Fas (Apo-1, CD95) expression in naive T cells and Fas-ligand gene and protein expression in both naive and primed T cells, resulting in Fas/Fas-L interaction-mediated cell death. ATG-induced apoptosis and Fas-L expression were not observed with an ATG preparation lacking CD2 and CD3 antibodies. Susceptibility to ATG-induced apoptosis was restricted to activated cells, dependent on IL-2, and prevented by Cyclosporin A, FK506, and rapamycin. The data suggest that low doses of ATGs could be clinically evaluated in treatments aiming at the selective deletion of in vivo activated T cells in order to avoid massive lymphocyte depletion and subsequent immunodeficiency.
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PMID:Induction of Fas (Apo-1, CD95)-mediated apoptosis of activated lymphocytes by polyclonal antithymocyte globulins. 951 35

ERYTHROPOIETIN (EPO): Erythropoietin (EPO) is a hormone that promotes the proliferation and differentiation of erythroid progenitor cells and regulates the number of erythrocytes in peripheral blood. EPO is produced mainly by the kidneys, and transcription of the EPO gene is promoted by a reduction in the oxygen concentration in the blood. The existence of EPO was suggested near the end of the 19th century by the discovery that hypoxia increases the production of red blood cells. EPO was identified as a serum factor in the 1950s, and in 1970 Miyake and coworkers succeeded in purifying it by using the urine of patients with aplastic anemia as a starting material. The human EPO gene was cloned in 1985 using a partial amino acid sequence from this purified EPO, and it is well known that recombinant EPO is currently used as a drug to treat anemia associated with chronic renal failure and other illnesses. ACTION OF EPO: When human bone marrow cells are cultured in a semisolid medium containing EPO, they form small erythroblast colonies in five to seven days, and by day 10 large erythroblast colonies appear that resemble fireworks ("burst" colonies). The original cells in the former colonies are called colony forming units-erythroid (CFU-E) or late-stage erythroblast progenitor cells and in the latter colonies they are called burst forming units-erythroid (BFU-E) or early-stage erythroblast progenitor cells. As shown in Figure 1, red blood cells are produced through differentiation from stem cells to BFU-E, CFU-E, and erythroblasts. Although EPO acts on both BFU-E and CFU-E cells, CFU-E cells show greater sensitivity to EPO, and other factors such as stem cell factor (SCF), interleukin (IL)-3, IL-4, and granulocyte macrophage colony-stimulating factor (GM-CSF) must be present together with EPO for BFU-E cell proliferation. In erythroblasts beyond the CFU-E stage, sensitivity to EPO decreases as the cells mature. THE EPO RECEPTOR AND THE CYTOKINE RECEPTOR FAMILY: The EPO receptor gene was cloned by D'Andrea and coworkers in 1989 from murine erythroleukemia cells [1]. It became clear that the EPO receptor belongs to the cytokine receptor family that comprises receptors for the various interleukins, GM-CSF, granulocyte colony-stimulating factor (G-CSF), growth hormone and prolactin. The special characteristic of this family of receptors is that they are switched on (i.e., the receptor is activated) and transduce signals to the interior of the cell by the formation of homo- or hetero-oligomers (dimers or trimers). Moreover, hetero-oligomers of these receptors share a common receptor subunit. As shown in Figure 2, the IL-3, IL-5 and GM-CSF receptors have a common &bgr; subunit, and their ligand specificity is determined by the &agr; subunit. In the same manner, the IL-6, LIF and oncostatin M (OSM) receptors all share gp130, which is the &bgr; subunit of the IL-6 receptor. The IL-2, IL-4 and IL-7 receptors all share the &ggr; subunit of the IL-2 receptor. All the above receptors are activated by the formation of hetero-oligomers, but the G-CSF receptor, EPO receptor, and growth hormone receptor are activated by the formation of homodimers of the same types of molecules [2]. We can see that groups of cytokines such as the interleukins that affect a relatively wide range of cells and have redundant biological activity create this redundancy through the common use of a single receptor subunit. On the other hand, EPO and G-CSF act with high specificity on a relatively limited range of cells, so it was probably unnecessary for their receptors to share one of the subunits. EPO RECEPTOR AND JAK2 KINASE: The signal for cellular proliferation and differentiation into erythroblasts is thought to originate at the EPO receptor. The cytoplasmic domain of the EPO receptor can be divided into two major regions. Roughly half of the cytoplasmic domain, the part lying nearest the plasma membrane, is required for generating the signals for proliferation and differentiation such as the induction of globin synthesis [3, 4]. The remaining half is not required for this signaling, and, conversely, it acts to dampen the signals. It is known that a tyrosine kinase called JAK2 associates with the region near the plasma membrane, undergoes autophosphorylation, and phosphorylates the EPO receptor, and a transcription factor called a STAT [5]. It is thought that JAK2 plays an important role in promoting cellular proliferation. The STAT is activated by the phosphorylation, and it then translocates to the nucleus, recognizes a specific base sequence in the promoter region of its target gene, and initiates transcription. At present, we know that the STAT whose activation is mediated by the EPO receptor is STAT5, and the target genes are CIS [6], which has an SH2 domain (a molecular structure that recognizes a phosphorylated tyrosine) and OSM [7], which is a pleiotropic cytokine. However, activation of STAT5 and activation of the target genes are not unique to the EPO receptor, and they also occur with the IL-2 and IL-3 receptors. Moreover, the JAK2 substrate that is directly linked to cellular proliferation is still unknown. At present, studies are under way to determine the transcription factors specific to EPO and their target genes, as well as the substrates of JAK2. RECEPTOR PHOSPHORYLATION AND CESSATION OF THE SIGNAL: On the other hand, tyrosine phosphorylation of the receptor is necessary at the cytoplasmic tail region far from the plasma membrane, and the signal transduction pathway that originates with this phosphorylated tyrosine and is mediated by proteins with SH2 domains becomes activated. First, a GTP/GDP exchange factor called SOS, which is mediated by Shc and Grb2, migrates to the plasma membrane and converts a ras protein to its GTP form. The activated ras protein then activates the Raf-MAP kinase kinase-MAP kinase cascade, and ultimately initiates the transcription of oncogenes such as c-fos and c-jun. An enzyme called PI3 kinase binds to the tyrosine phosphorylation site of the receptor and a second messenger is born. It is known that this pathway is a requirement for DNA synthesis in certain types of fibroblasts. However, these signal transduction pathways are not unique to the EPO receptor, and they are also activated by most growth factor receptors, so they are not necessarily required for EPO-induced proliferation. Conversely, the tyrosine phosphatase SH-PTP1 (also called HCP) that has an SH2 domain and is specific to blood cells associates with the tyrosine phosphorylation site of the receptor and promotes the dephosphorylation of JAK2. In other words, the role of SH-PTP1 is to stop generation of the signal [8]. Therefore, in mutations lacking this cytoplasmic tail region of the receptor far from the plasma membrane, the receptors do not undergo tyrosine phosphorylation, JAK2 activation continues for a longer period of time, and thus the signal is generated more efficiently. In fact, in one patient with a mild case of familial erythrocytosis a mutation was discovered in which the C-terminus of the EPO receptor was missing 70 amino acids [9]. This was a dominant genetic trait, and the patient's erythroblasts showed an increased sensitivity to EPO. In this family the impairment was not severe enough to be called an illness, and in fact it is said that this patient was proficient enough athletically to compete for a gold medal at the Olympics. More specifically, the reason that athletes undergo training at high altitudes is to boost EPO production because of the lower oxygen partial pressure, and this brings about the desired effect of sustained athletic capability due to a resultant increase in red blood cells. However, the same effect has occurred naturally in this athlete thanks to accelerated receptor capability.
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PMID:Physician Education: The Erythropoietin Receptor and Signal Transduction. 1038 12

In a prospective long-term study on the incidence of paroxysmal nocturnal hemoglobinuria (PNH), 115 consecutive patients with severe aplastic anemia (SAA), 97 treated with antilymphocyte globulin (ALG) and 18 with bone marrow transplantation (BMT), were observed over a period of 4-18 years and tested for the presence of complement-sensitive hematopoietic precursor cells with the bone marrow (BM) sucrose test. Sixteen (14%) of the ALG-treated patients developed clinical signs of PNH between 0.5 and 8 years after treatment. Complement-sensitive BM precursors were found in 89% of the SAA patients at some time during their disease, but in none of 18 normal donors. At diagnosis, their proportion was significantly higher in patients who later developed PNH than in patients who later achieved disease-free complete remission (CR). After ALG, the abnormal population was found in both groups, but it was gradually replaced by normal precursors in remission patients. After BMT, the complement-sensitive population decreased to very low numbers in patients with a stable graft, but increased again in 3 patients upon graft rejection. Mimicking the PNH defect by enzymatic removal of glycosyl-phosphatidylinositol (GPI)-linked proteins from CD34+ cells resulted in their complement sensitivity, suggesting that the BM sucrose test identifies precursor cells carrying the PNH defect. In 66 patients, white blood cells (WBC) in peripheral blood (PB) were examined for GPI-deficient populations by flow cytometry (FACS). Ten patients with signs of clinical or laboratory PNH had over 25% complement-sensitive precursor cells in the BM and a GPI-deficient WBC population in the PB. Of 56 SAA patients without PNH, 8 had an abnormal population detectable with both tests, 26 only with the BM sucrose test, 4 only with PB FACS analysis, and in 18, no abnormal cells were detected with either test. In search for parameters which might explain why in some patients the abnormal population expands, while it regresses or disappears in others, we tested the release of IL-2 as a parameter of immune competence. At diagnosis, IL-2 release was approximately 50% of normal in patients who later developed PNH, while it was double the normal value in patients who later achieved CR. We conclude that the majority of SAA patients transiently harbor complement-sensitive precursor cells in the BM. Patients with more than 25% abnormal BM precursors and low endogenous IL-2 release are at risk of progression to clinical PNH.
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PMID:High incidence of transiently appearing complement-sensitive bone marrow precursor cells in patients with severe aplastic anemia--A possible role of high endogenous IL-2 in their suppression. 1043 96


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