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Query: UMLS:C0027121 (myositis)
 4,538 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Polymyositis and dermatomyositis are inflammatory myopathies characterized by proximal muscle weakness and myopathic electromyographic and histological findings. While the causes of myositis are not known, the close association of these disorders with a spectrum of autoantibodies suggests an etiologic and/or pathogenetic role for autoimmune processes. Of particular interest in this regard are antibodies directed against histidyl as well as other tRNA synthetases which are almost uniquely associated with myositis and may define a distinct subset of patients. Recently we isolated the histidyl tRNA synthetase gene which encodes the autoantigen representing the most frequent target of the myositis autoimmune response. The isolation and expression of this gene has allowed us to investigate both the autoreactive epitopes on histidyl-tRNA synthetase and the extent to which these correlate with functional epitopes on the molecule. As described here, the results of these studies as well as other recent data pertaining to the immunopathogenesis of myositis, provide a framework for delineating the mechanisms which render synthetases and other translation-related proteins autoantigenic in myositis, and allow one to examine the significance of such autoimmune responses in the etiology and pathogenesis of inflammatory myopathy.
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PMID:Anti-Jo-1 autoantibodies and the immunopathogenesis of autoimmune myositis. 172 33

We have developed an enzyme-linked immunosorbent assay (ELISA) specific for autoantibodies directed against the autoantigen Jo-1 (histidyl-tRNA synthetase) using antigen prepared biochemically from HeLa cells. No other patient sera, including those containing antibodies directed at threonyl-tRNA synthetase or alanyl-tRNA synthetase, reacted in the assay. Screening of sera from 169 patients with a variety of autoimmune and neuromuscular diseases confirmed that anti-Jo-1 antibodies are confined to a subgroup of patients with pure polymyositis, pure dermatomyositis, or myositis associated with another rheumatic disease.
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PMID:An enzyme-linked immunosorbent assay for the detection and quantitation of anti-Jo-1 antibody in human serum. 349 84

Polymyositis is regarded as an autoimmune inflammatory muscle disease. A major subgroup of patients have autoantibodies to cellular histidyl-transfer RNA synthetase (HRS). We have analyzed the role of the autoantigen HRS in the induction of murine myositis in a comparative study of inoculation of BALB/c mice with recombinant HRS protein versus naked DNA coding for HRS. Adult BALB/c mice produced antibodies to human HRS following inoculation with HRS protein and adjuvant, but myositis was not observed. Alternatively, expression plasmid DNA constructs encoding full-length and truncated human HRS were inoculated intramuscularly in gene transfer studies. DNA-inoculated mice produced relatively low anti-HRS antibody titers. However, in contrast to recombinant HRS protein-inoculated mice, HRS gene transfer induced pathology with evidence of cellular infiltration of perivascular and endomysial regions of the inoculated muscle. Multiple inoculations of a plasmid construct encoding a hybrid molecule consisting of HRS and the transferrin receptor cytoplasmic tail induced the highest levels of antibodies and persisting cellular infiltration. Unlike HRS, expression of influenza virus hemagglutinin (HA) following inoculation of an HA plasmid did not induce myositis. Transfer of naked DNA constructs expressing HRS is likely to provide valuable information on the autoimmune response to this protein and its role in the development of myositis.
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PMID:Myositis induced by naked DNA immunization with the gene for histidyl-tRNA synthetase. 928 47

Myositis-overlap syndromes are characterized by a heterogeneous group of clinical syndromes of which many are closely linked with specific autoantibodies. Clinical and laboratory-based research into this fascinating group of syndromes have given us clues in elucidating the role of immunogenetic, environmental influences on the etiopathogenesis of autoimmune disease. Patients positive for anti-snU1 RNP antibody often present with a constellation of "autoimmune-related" clinical features, often not fulfilling the diagnostic criteria for a single disease entity. Controversy remains as to whether this represents a single disease entity, namely mixed connective tissue disease, or an undifferentiated autoimmune rheumatic/overlap syndrome. Anti-PM-Scl antibodies are linked with myositis-scleroderma overlap and generally tend to follow a benign course, often responding well to minimal immunosuppression. More recently the number of anti-tRNA synthetase antibody-associated overlap syndromes has expanded; antibodies to the autoantigen histidyl-tRNA synthetase (Jo1) being the commonest and best characterized. Patients with these antibodies often have severe interstitial lung disease and the poorest prognosis, often necessitating aggressive immunosuppressive therapy.
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PMID:Myositis overlap syndromes. 1055 70

The mechanism of injury and death of muscle cells in the inflammatory myopathies (dermatomyositis, polymyositis, and inclusion body myositis) remains obscure. We and others have not detected apoptosis in the muscle biopsies from patients with myositis despite clear evidence of cell damage and loss. We provide evidence in this study that Fas ligand (FasL) as well as Fas is present on muscle cells and inflammatory cells in myositis biopsies: Fas is present on most muscle cells and lymphocytes, and FasL is present on degenerating muscle cells and many infiltrating mononuclear cells. The expression of both Fas and FasL in the inflamed tissue makes the absence of apoptosis more striking. To address the mechanisms of this resistance to classical apoptosis in muscle cells, we have investigated the expression of the antiapoptotic molecule FLICE (Fas-associated death domain-like IL-1-converting enzyme)-inhibitory protein (FLIP) in muscle biopsies of myositis patients and in cultured human skeletal muscle cells. Using laser capture microscopy, we have shown that FLIP is expressed in the muscle fibers and on infiltrating lymphocytes of myositis biopsies. Furthermore, we have shown that FLIP, but not Bcl-2, is expressed in cultured human skeletal muscle cells stimulated with proinflammatory cytokines, and inhibition of FLIP with antisense oligonucleotides promotes significant cleavage of poly(ADP-ribose) polymerase autoantigen, a sensitive indicator of apoptosis. These studies strongly suggest that the resistance of muscle to Fas-mediated apoptosis is due to the expression of FLIP in muscle cells in the inflammatory environment in myositis.
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PMID:The inhibition of apoptosis in myositis and in normal muscle cells. 1079 13

The antigenic specificity of an unusual antinuclear antibody pattern in three patient sera was identified after separating HeLa-cell nuclear extracts by two-dimensional (2D) gel electrophoresis and localizing the antigens by immunoblotting with patient serum. Protein spots were excised from the 2D gel and their contents were analyzed by matrix-assisted laser desorption-ionization (MALDI) or nanoelectrospray ionization time-of-flight (TOF) tandem mass spectrometry (MS) after in-gel digestion with trypsin. A database search identified the proteins as the C1 and C2 heterogeneous nuclear ribonucleoproteins. The clinical spectrum of patients with these autoantibodies includes arthritis, psoriasis, myositis, and scleroderma. None of 59 patients with rheumatoid arthritis, 19 with polymyositis, 33 with scleroderma, and 10 with psoriatic arthritis had similar antibodies. High-resolution protein-separation methods and mass-spectrometric peptide mapping in combination with database searches are powerful tools in the identification of novel autoantigen specificities.
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PMID:Heterogeneous nuclear ribonucleoproteins C1/C2 identified as autoantigens by biochemical and mass spectrometric methods. 1105 75

Polymyositis (PM) is an inflammatory muscle disease caused by autoimmune dysfunction, considered to be caused by cytotoxic CD8 T cells. To date, no autoantigens have been identified. We attempted to induce an experimental allergic myositis (EAM) in BALB/c mice by inoculating syngeneic dendritic cells (DC) presenting peptides that are expected to match the binding anchor motif of H-2K(d) (BALB/c). We selected peptides that are highly expressed in skeletal muscle. Only when we inoculated syngeneic bone marrow-derived DC presenting pyruvate kinase M1/M2 peptide 464-472 in BALB/c mice, 41.7% of the mice (EAM) developed pathological changes in skeletal muscle compatible to human PM. Under other conditions (when we inoculated DC presenting no synthetic peptides into BALB/c or C57BL/6 mice and DC presenting pyruvate kinase M1/M2 peptide into C57BL/6 mice), there were no necrotizing and inflammatory lesions. Induction of EAM in the same manner as above also induced CTL activity against P815 cells with the same peptide and syngeneic differentiated cultured myotubes without peptides by the chromium release assay. Consistent with the similarity of the binding anchor motif of H-2K(d) (BALB/c) and HLA A*2402, we conclude that pyruvate kinase M1/M2 peptide is a candidate autoantigen not only in BALB/c-EAM but also in human-PM with the HLA A*2402 allele.
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PMID:Dendritic cells presenting pyruvate kinase M1/M2 isozyme peptide can induce experimental allergic myositis in BALB/c mice. 1143 Oct 10

Experimental autoimmune myositis (EAM) is a rodent model for human inflammatory muscle disease (IMD). It can be induced by immunization of rodents with skeletal muscle homogenate and adjuvant. The specific myositogenic autoantigen has not been clearly identified although some evidence points to skeletal muscle myosin. In this report we strengthen this evidence, showing that Lewis rats immunized with purified skeletal muscle myosin develop EAM with the same pattern and severity as EAM induced by whole rabbit skeletal muscle homogenate (WRM). Multiple inflammatory lesions are detected histopathologically in the biceps, quadriceps, and gastrocnemius muscles. Myosin-reactive T cells from animals immunized either with myosin or with WRM have similar patterns of antigen-induced proliferation. The results show that myosin, a component of skeletal muscle, is at least one autoantigen in EAM.
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PMID:Skeletal muscle myosin is the autoantigen for experimental autoimmune myositis. 1278 10

The inflammatory myopathies, commonly described as idiopathic, are the largest group of acquired and potentially treatable myopathies. On the basis of unique clinical, histopathological, immunological, and demographic features, they can be differentiated into three major and distinct subsets: dermatomyositis, polymyositis, and inclusion-body myositis. Use of new diagnostic criteria is essential to discriminate between them and to exclude other disorders. Dermatomyositis is a microangiopathy affecting skin and muscle; activation and deposition of complement causes lysis of endomysial capillaries and muscle ischaemia. In polymyositis and inclusion-body myositis, clonally expanded CD8-positive cytotoxic T cells invade muscle fibres that express MHC class I antigens, which leads to fibre necrosis via the perforin pathway. In inclusion-body myositis, vacuolar formation with amyloid deposits coexists with the immunological features. The causative autoantigen has not yet been identified. Upregulated vascular-cell adhesion molecule, intercellular adhesion molecule, chemokines, and their receptors promote T-cell transgression, and various cytokines increase the immunopathological process. Early initiation of therapy is essential, since both polymyositis and dermatomyositis respond to immunotherapeutic agents. New immunomodulatory agents currently being tested in controlled trials may prove promising for difficult cases.
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PMID:Polymyositis and dermatomyositis. 1464 32

Unique autoantibody specificities are strongly associated with distinct clinical phenotypes, making autoantibodies useful for diagnosis and prognosis. To investigate the mechanisms underlying this striking association, we examined autoantigen expression in normal muscle and in muscle from patients with autoimmune myositis. Although myositis autoantigens are expressed at very low levels in control muscle, they are found at high levels in myositis muscle. Furthermore, increased autoantigen expression correlates with differentiation state, such that myositis autoantigen expression is increased in cells that have features of regenerating muscle cells. Consistent with this, we found that cultured myoblasts express high levels of autoantigens, which are strikingly down-regulated as cells differentiate into myotubes in vitro. These data strongly implicate regenerating muscle cells rather than mature myotubes as the source of ongoing antigen supply in autoimmune myositis. Myositis autoantigen expression is also markedly increased in several cancers known to be associated with autoimmune myositis, but not in their related normal tissues, demonstrating that tumor cells and undifferentiated myoblasts are antigenically similar. We propose that in cancer-associated myositis, an autoimmune response directed against cancer cross-reacts with regenerating muscle cells, enabling a feed-forward loop of tissue damage and antigen selection. Regulating pathways of antigen expression may provide unrecognized therapeutic opportunities in autoimmune diseases.
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PMID:Enhanced autoantigen expression in regenerating muscle cells in idiopathic inflammatory myopathy. 1572 37


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