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)

Paroxysmal nocturnal hemoglobinuria (PNH) is a hematopoietic stem cell disorder in which clonal cells defective in glycosylphosphatidylinositol (GPI) biosynthesis are expanded, leading to complement-mediated hemolysis. PNH is often associated with bone marrow suppressive conditions, such as aplastic anemia. One hypothetical mechanism for the clonal expansion of GPI(-) cells in PNH is that the mutant cells escape attack by autoreactive cytotoxic cells that are thought to be responsible for aplastic anemia. Here we studied 2 model systems. First, we made pairs of GPI(+) and GPI(-) EL4 cells that expressed major histocompatibility complex (MHC) class II molecules and various types of ovalbumin. When the GPI-anchored form of ovalbumin was expressed on GPI(+) and GPI(-) cells, only the GPI(+) cells presented ovalbumin to ovalbumin-specific CD4(+) T cells, indicating that if a putative autoantigen recognized by cytotoxic cells is a GPI-anchored protein, GPI(-) cells are less sensitive to cytotoxic cells. Second, antigen-specific as well as alloreactive CD4(+) T cells responded less efficiently to GPI(-) than GPI(+) cells in proliferation assays. In vivo, when GPI(-) and GPI(+) fetal liver cells, and CD4(+) T cells alloreactive to them, were cotransplanted into irradiated hosts, the contribution of GPI(-) cells in peripheral blood cells was significantly higher than that of GPI(+) cells. The results obtained with the second model suggest that certain GPI-anchored protein on target cells is important for recognition by T cells. These results provide the first experimental evidence for the hypothesis that GPI(-) cells escape from immunologic attack.
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PMID:Inefficient response of T lymphocytes to glycosylphosphatidylinositol anchor-negative cells: implications for paroxysmal nocturnal hemoglobinuria. 1239 37

Aplastic anemia (AA) remains an elusive disease. Its pathophysiology is not only fascinating by the seemingly simple findings of cytopenia and marrow hypoplasia, but may also contain key information to the understanding of other fundamental processes such as stem cell regeneration, evolution, and immune control of clonal diseases. Although measurements of blood counts provide an objective tool to assess the disease activity and response to the therapy, immune pathophysiology of AA, as inferred from the successes of immunosuppression, provides only few other clinical clues. Similarly, the current laboratory evidence remains mostly indirect. In spite of the recognition of immune pathways of hematopoietic inhibition and apoptosis in AA, the fundamental question about the nature of the antigen(s) inciting or maintaining the pathologic immune response that ultimately leads to bone marrow failure, remains open. However, recognition of the immune targets may aid in understanding not only the pathogenesis but also many of clinical associations and the late squelae of AA. For example, abnormal cells in AA and myelodysplastic syndrome (MDS) MDS may harbor inciting antigens but the immune response lacks selectivity. Clonal selection pressure may be a result of this process or alternatively, emergence of tolerance could lead to the establishment of abnormal hematopoiesis. Clonal proliferation of large granular lymphocytosis could represent an example of an exaggerated response to an immunodominant hematopoietic antigen. In addition to the traditional functional or phenotypic analysis, pathologic immune response in AA can be studied on molecular level by identifying and quantitating T cell clones based on the presence of unique variable B-chain CDR3 sequences. Detection of clonal expansion is based on the observation that in infections and autoimmune conditions, the presence of antigenic drive will lead to the expansion and overrepresentation of T cell clones recognizing this antigen. However, simple analysis of clonal representation is not sufficient to resolve the complex nature of the immune repertoire in the context of genetic and clinical heterogeneity. Therefore, we analyzed VB and CDR3 repertoire in CD4 and CD8 cells, activated or effector cell subsets. To distinguish truly expanded and likely immunodominant clones, we first studied VB distribution and cloned CDR3 sequences from expanded VB families. Identified clonotypic sequences can be used to design molecular tests to quantitate the strength of pathologic immune response. Clonotype sharing has been confirmed in patients with similar clinical features indicating presence of common antigens. In addition, quantitative analysis showed correlation with the therapy response. Persistence and patterns of clonotypes may be helpful in the classification of immune-mediated marrow failure based on the immune characteristics and will allow inferences into the inciting pathways.
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PMID:Immune pathophysiology of aplastic anemia. 1243 Aug 55

T cell-mediated suppression of haematopoiesis is believed to play an important role in the pathophysiology of aplastic anaemia (AA) and in the pancytopenia of some myelodysplastic syndromes (MDS). Natural-killer T (NKT) cells belong to a unique lymphocyte subset that expresses an invariant T-cell receptor (TCR), consisting of Valpha24JalphaQ, and common NK cell surface markers. NKT cells have been hypothesized to play a role in immune regulation, and many human autoimmune conditions are associated with NKT cell deficiency. Here we investigate the role of NKT cells in AA and MDS patients. Flow cytometry demonstrated that NKT cells, unlike other T-lymphocyte subpopulations, were disproportionally decreased in AA and MDS marrow. When we compared variability within the CDR3 region of Valpha24 in CD4-CD8- T cells derived from AA and healthy individuals, the CDR3 size of Valpha24 cells showed a polyclonal distribution in AA patients, while in control subjects a typical oligoclonal or monoclonal pattern was found. Southern blot and sequence analysis of Valpha24 polymerase chain reaction products revealed that the NKT cell-specific JalphaQ region was predominant in control subjects, whereas it was not, or only very weakly, detected in AA and MDS patients. These results show that NKT cells are profoundly decreased in AA and MDS, and their deficiency may, as in other human autoimmune diseases, play a role in the local immune dysregulation in AA and MDS.
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PMID:Selective reduction of natural killer T cells in the bone marrow of aplastic anaemia. 1243 63

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

A 39-year-old woman with severe aplastic anemia (SAA) was transferred to our institution. She also had autoimmune thyroiditis with several positive autoantibodies. Clonal or oligoclonal T-cell proliferation was demonstrated by determining the size distribution of the complementarity-determining region 3 (CDR3) of T-cell receptor beta-chain (TCR-Vbeta) subfamilies in the patient's bone marrow and peripheral blood cells. The results suggested that hematopoiesis was suppressed by immune-mediated mechanisms. Immunosuppressive therapy for SAA using cyclosporin A (CsA) alone or concurrent CsA and antithymocyte globulin (ATG) failed to induce a hematological response. The intensity of the autoantibodies, however, partially decreased during this period. In addition, the CD4/CD8 ratio was inverted after immunosuppressive therapy. These observations indicate that, in a subset of SAA, immune-mediated hematopoietic suppression cannot be successfully treated by conventional immunosuppressive therapy, even though a substantial improvement in the underlying immunological changes can be achieved. Other therapies such as hematopoietic stem cell transplantation or more intensified repeated ATG therapy may be necessary for such patients.
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PMID:Severe aplastic anemia with autoimmune thyroiditis showing no hematological response to intensive immunosuppressive therapy. 1262 93

Post-transplantation lymphoproliferative disorder (PTLD) is usually an aberrant proliferation of EBV-infected B cells. We report the case of a 31-year-old man with severe aplastic anemia who suffered PTLD 42 days post-BMT from an unrelated donor. At the onset of PTLD, peripheral blood lymphocytes were comprised of 40% CD20(+) cells, 3% CD4(+) cells, and 56% CD8(+) cells. A highly sensitive in situ hybridization (ISH) method was used to detect EBV-encoded small non-polyadenylated RNA 1 (EBER-1) in 33.9% of sorted CD20(+) cells, 4.4% of CD4(+) cells, and 1.4% of CD8(+) cells. Each T-cell fraction contained less than 0.034% of contaminated EBV-infected B cells. Clonal proliferation of both B and T cells was demonstrated by Southern blotting. The patient did not respond to donor leukocyte infusion and died due to deterioration of PTLD. At autopsy, examination of multiple organs revealed B-cell (rather than T-cell) infiltration. This case clearly indicates that EBV can simultaneously infect B and T cells and can induce clonal proliferation of both lymphocyte subsets in severely immunocompromised patients.
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PMID:Epstein-Barr virus (EBV)-associated post-transplantation lymphoproliferative disorder simultaneously affecting both B and T cells after allogeneic bone marrow transplantation. 1266 36

The method of immune-enzyme assay was used to examine 113 patients with secondary immunodeficiency, including 16 HIV-infected drug-addicts (group 1), 36 patients with cytomegalovirus infection (CMVI) and with immunoregating index CD4/CD8 below 1.0 (group 2), 30 patients with CMVI and with CD4/CD8 below 1.2 (group 3) and 31 patients with aplastic anemia and with anemia of unclear genesis (group 4), for parvovirus infection caused by parvovirus B19. As for groups 1 and 4, the antibodies were detected in 50 and 48.4% of cases; it is noteworthy that an active parvovirus infection was registered in the above groups more often than in groups 2 and 3. There were patients with the antibodies in group 2 by 1.8 times more than in group 3. It is suggested that the simultaneous impact of HIV, CMV and parvoviruses significantly aggravates the immunodeficiency and contributes to a more severe clinical course.
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PMID:[Diagnosis of parvovirus B19 infection in patients with secondary immunodeficiency diseases]. 1282 4

Aplastic anemia (AA) is regarded as an immunological disorder because of the clinical effect of immunosuppressive therapy. Recent studies have reported that cytokines play an important role in the development of AA. In the present study, we measured levels of T-cell derived intracellular cytokine production in peripheral blood and bone marrow (BM) of patients with AA. We demonstrated that BM lymphocytes, particularly CD4(+) and CD8(+) T cells, in patients with AA produced significantly higher amounts of tumor necrosis factor-alpha (TNF-alpha), compared with lymphocytes in normal controls. We have previously reported that expression of TNF receptor (R)1 and TNFR2 in the CD34(+) CD38(-) and CD34(+) CD38(+) fractions of patients with AA is significantly higher than those in normal control. These results indicate that BM stem cells in patients with AA may possess high sensitivity to TNF-alpha. This in turn suggests that TNF-alpha affects hematopoiesis at an earlier stage in AA patients than in normal controls. We strongly support the hypothesis that a simultaneous increase in TNF-alpha production by BM lymphocytes and sensitivity of stem cells to TNF-alpha leads to BM failure in AA.
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PMID:Excessive production of tumor necrosis factor-alpha by bone marrow T lymphocytes is essential in causing bone marrow failure in patients with aplastic anemia. 1518 32

To identify candidate antigens in aplastic anemia (AA), we screened proteins derived from a leukemia cell line with serum of an AA patient and identified diazepam-binding inhibitor-related protein 1 (DRS-1). Enzyme-linked immunosorbent assay (ELISA) revealed high titers of anti-DRS-1 antibodies (DRS-1 Abs) in 27 (38.0%) of 71 AA patients displaying increased paroxysmal nocturnal hemoglobinuria (PNH)-type cells (PNH(+)), 2 (6.3%) of 32 PNH(-) AA patients, 5 (38.5%) of 13 PNH(+) myelodysplastic syndrome (MDS) patients, and none of 42 PNH(-) MDS patients. DRS-1 gene was abundantly expressed in myeloid leukemia cell lines and in CD34(+) cells derived from healthy individuals. Stimulation of T cells from an AA patient displaying high DRS-1 Abs with a putative CD4(+) T-cell epitope (amino acid residues [aa's] 191-204) presented by HLA-DR15, which overlapped with a hot spot (aa's 173-198) of DRS-1 Ab epitopes, gave rise to T cells cytotoxic for L cells (murine fibroblasts) that were transfected with DRB1*1501 and DRS-1. Enzyme-linked immunospot assay demonstrated increased frequency of T-cell precursors specific to the DRS-1 peptide in other HLA-DR15(+) AA patients displaying high DRS-1 Ab titers. These findings indicate that DRS-1 may serve as an autoantigen eliciting immune attack against hematopoietic stem cells in a subset of AA patients characterized by increased PNH-type cells.
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PMID:Diazepam-binding inhibitor-related protein 1: a candidate autoantigen in acquired aplastic anemia patients harboring a minor population of paroxysmal nocturnal hemoglobinuria-type cells. 1521 32

Regulatory T cells are believed to control the development and progression of autoimmunity by suppressing autoreactive T cells. Decreased numbers of CD4(+)CD25(+) FOXP3(+) T cells (Tregs) are associated with impaired immune homeostasis and development of autoimmune diseases. The transcription factors FOXP3 and NFAT1 have key roles in regulatory T-cell development and function. We show that Tregs are decreased at presentation in almost all patients with aplastic anemia; FOXP3 protein and mRNA levels also are significantly lower in patients with aplastic anemia and NFAT1 protein levels are decreased or absent. Transfection of FOXP3-deficient CD4(+)CD25(+) T cells from patients with a plasmid encoding wild-type NFAT1 resulted in increased FOXP3 expression in these cells. By NFAT1 knockdown in CD4(+)CD25(+) T cells, FOXP3 expression was decreased when NFAT1 expression was decreased. Our findings indicate that decreased NFAT1 could explain low FOXP3 expression and diminished Treg frequency in aplastic anemia. Treg defects are now implicated in autoimmune marrow failure.
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PMID:Deficient CD4+ CD25+ FOXP3+ T regulatory cells in acquired aplastic anemia. 1746 69


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