Clinical features of anti-synthetase syndrome associated interstitial lung disease: a retrospective cohort in China.

BACKGROUND: Anti-synthetase syndrome (ASSD) is a chronic autoimmune condition characterized by antibodies directed against an aminoacycl transfer RNA synthetase (ARS) along with a group of clinical features including the classical clinical triad: inflammatory myopathy, arthritis, and interstitial lung disease (ILD). ASSD is highly heterogenous due to different organ involvement, and ILD is the main cause of mortality and function loss, which presents as different patterns when diagnosed. We designed this retrospective cohort to describe the clinical features and disease behaviour of ASSD associated ILD. METHODS: Data of 108 cases of ASSD associated ILD were retrospectively collected in Beijing Chaoyang Hospital from December 2017 to March 2019. Data were obtained from the Electronic Medical Record system. Patients were divided into 5 groups according to distinct aminoacyl tRNA synthetase (ARS) antibodies. RESULTS: Overall, 108 consecutive patients were recruited. 33 were JO-1 positive, 30 were PL-7 positive, 23 were EJ positive, 13 were PL-12 positive and 9 were OJ positive. The JO-1 (+) group had a significant higher rate of mechanic's hand (57.6%) than other 4 groups. Polymyositis/dermatomyositis (PM/DM) was diagnosed in 25 (23.1%) patients and no difference was observed among the 5 groups. The PL-7 (+) group had a higher frequency of UIP pattern (13.3%) than the other 4 groups but the difference was not significant, and the EJ (+) group had the most frequent OP pattern (78.2%), which was significantly higher than the PL-7 (+) (P < 0.001) and PL-12 (+) groups (P = 0.025). The median follow-up time was 10.7 months, during which no patients died. All received prednisone treatment, with or without immunosuppressants. At the 6-month follow-up, 96.3% of all patients (104/108) had a positive response to therapy, the JO-1 (+) and EJ (+) groups had a significantly higher improvement of forced vital capacity than the other 3 groups (P < 0.05), and the PL-7 group had the lowest FVC improvement (P < 0.05). The JO-1 (+) group and EJ (+) group had significantly higher anti-Ro-52 positive occurrence than the other 3 groups (P < 0.05). CONCLUSION: Anti PL-7 antibody had the same frequency as anti-JO-1 in ASSD-ILD, in which the ILD pattern was different with distinct anti-ARS antibodies. Most ASSD-ILD had a positive response to steroid therapies, with or without immunosuppressants. The PL-7 (+) group had the highest occurrence of UIP pattern, and a significantly lower response to therapy.

Clinical features and outcomes of the patients with anti-glycyl tRNA synthetase syndrome.

OBJECTIVE: To analyze the clinical features and outcomes of the patients with anti-glycyl tRNA synthetase (anti-EJ) syndrome in a large Chinese cohort. METHODS: The medical records, imaging, and serologic data of patients with anti-EJ antibodies from the China-Japan Friendship Hospital database were retrospectively investigated. Anti-EJ antibodies were identified using immunoblot assay. Long-term follow-up was conducted. RESULTS: Anti-EJ antibodies were present in 46 (19.7%) of the 234 patients with antisynthetase syndrome (ASS), preceded by anti-Jo-1 and anti-PL-7 antibodies. The mean age of disease onset was 51.2 ± 15.9 years, and 69.6% of these patients were female. The most prevalent clinical feature was interstitial lung disease (ILD) (96.7%), which was also the most common initial manifestation, followed by fever (60.9%), mechanic's hands (56.5%), muscle involvement (50%), and Raynaud phenomenon (8.7%). Ten (21.7%) patients developed rapidly progressive ILD (RP-ILD). Organizing pneumonia (OP) on high-resolution computed tomography (HRCT) scans (OR = 37.5, p = 0.006) and a higher C-reactive protein-to-albumin ratio (CAR) (OR = 28.3, p = 0.01) were independent risk factors for RP-ILD. Muscular pathological features were heterogeneous. Concomitant infection was noted in 63.0% of the patients during the disease course. Hypoalbuminemia (OR = 0.759, p = 0.002) was an independent risk factor for concomitant infection. Patients responded well to glucocorticoid therapy. The 5- and 10-year survival rates of the patients with anti-EJ were 97.8% and 88%, respectively. CONCLUSION: Anti-EJ syndrome was found to be a relatively common ASS subtype, with a favorable outcome. A notable proportion of the patients experienced RP-ILD, which was prone to OP on HRCT and a higher CAR, and needed aggressive management. Key Points • ILD was the most common initial manifestation of anti-glycyl tRNA synthetase syndrome. • RP-ILD was notable in anti-EJ positive patients. • Anti-EJ positive patients possessed a favorable long-term prognosis, but easily relapsed.

Extracellular vesicles derived from macrophages display glycyl-tRNA synthetase 1 and exhibit anti-cancer activity.

Glycyl-tRNA synthetase 1 (GARS1), a cytosolic enzyme secreted from macrophages, promotes apoptosis in cancer cells. However, the mechanism underlying GARS1 secretion has not been elucidated. Here, we report that GARS1 is secreted through unique extracellular vesicles (EVs) with a hydrodynamic diameter of 20-58 nm (mean diameter: 36.9 nm) and a buoyant density of 1.13-1.17 g/ml. GARS1 was anchored to the surface of these EVs through palmitoylated C390 residue. Proteomic analysis identified 164 proteins that were uniquely enriched in the GARS1-containing EVs (GARS1-EVs). Among the identified factors, insulin-like growth factor II receptor, and vimentin also contributed to the anti-cancer activity of GARS1-EVs. This study identified the unique secretory vesicles containing GARS1 and various intracellular factors that are involved in the immunological defence response against tumorigenesis.

[A case of antisynthetase syndrome with anti-EJ antibody complicated by pericarditis].

A 69-year-old man was admitted with neck muscle weakness, symmetric proximal muscle weakness, skin rash and elevated serum creatine kinase levels. Muscle biopsy showed perifascicular necrosis and perimysial alkaline phosphatase activity. Chest CT revealed interstitial lung disease and colorectal cancer was diagnosed on colonoscopy. He was serologically positive for anti-EJ antibody, leading to the diagnosis of antisynthetase syndrome (ASS). After laparoscopic low anterior resection of the rectum, he received intravenous methylprednisolone (1,000 mg/d for 3 days) followed by oral prednisolone (50 mg/d). Although his muscle weakness improved after corticosteroid therapy, he developed pericardial effusion with resultant asymptomatic hypotension and arrhythmia possibly due to pericarditis. Corticosteroid monotherapy was insufficient to control the disease, and, we decided to use oral cyclosporin concurrently. After this combined therapy started, pericardial effusion and arrhythmia were improved. We should keep in mind that pericarditis can occur in patients with anti-EJ antibody-positive ASS, and early combined therapy with corticosteroid and immunosuppressive drugs for ASS may improve the patient's prognosis.

Immune Myopathy With Perimysial Pathology Associated With Interstitial Lung Disease and Anti-EJ Antibodies.

OBJECTIVES: We report a case of immune myopathy with perimysial pathology associated with anti-glycyl-transfer RNA synthetase (anti-EJ) antibody and an excellent treatment response. METHODS: Chart review. RESULTS: A 36-year-old woman presented with 3 months of fatigue, weight loss, progressive weakness in a scapuloperoneal distribution, and dysphagia. Nerve conduction studies, electromyography, and ultrasound suggested an irritable myopathy. She had marked elevations of creatine kinase and positive anti-glycyl-transfer RNA synthetase (anti-EJ) antibodies. A left biceps muscle biopsy revealed inflammation of the perimysium and surrounding perimysial blood vessels with focal fragmentation of the perimysium. Further evaluation revealed interstitial lung disease. Treatment with prednisone and mycophenolate mofetil led to marked clinical improvement of her symptoms. CONCLUSIONS: Our case adds to the growing spectrum of inflammatory myopathies and highlights the importance of performing a comprehensive, multisystem workup.

A Rare Case of Necrotizing Myopathy and Fibrinous and Organizing Pneumonia with Anti-EJ Antisynthetase Syndrome and SSA Antibodies.

BACKGROUND Idiopathic inflammatory myopathies are autoimmune disorders that can involve the skin, joints, muscles, and lungs. The most common of these disorders are dermatomyositis, polymyositis, overlap syndrome, and inclusion body myositis. Necrotizing autoimmune myopathy is an idiopathic inflammatory myopathy that is rarely associated with Sjögren's syndrome. The most common lung findings associated with anti-EJ antisynthetase syndrome are nonspecific interstitial pneumonia and usual interstitial pneumonia; this condition is rarely associated with fibrinous and organizing pneumonia. CASE REPORT Here, we present a rare case of necrotizing myopathy and fibrinous and organizing pneumonia in a 34-year-old African American man with Sjögren's syndrome and anti-EJ antibodies. The patient's presenting symptoms were cough and proximal muscle weakness of the extremities. He had elevated serum creatine kinase level, aldolase level, and erythrocyte sedimentation rate. Myositis panel was positive for anti-EJ antibodies. Chest radiography was consistent with bilateral interstitial infiltrates. CT chest showed patchy bilateral infiltrates. Quadriceps muscle biopsy revealed widespread necrotic fibers and lung biopsy showed fibrinous and organizing pneumonia. The patient responded well to immunoglobulin therapy, mycophenolate, and prednisone, which resulted in complete resolution of bilateral infiltrates and improved muscle pain and weakness. CONCLUSIONS Myopathies are characterized by myalgia and muscle weakness due to muscle fiber dysfunction and are associated with autoimmune diseases. Histopathological features may differ in idiopathic inflammatory myopathies. It is important to recognize the rare association of anti-EJ autoantibodies with necrotizing myopathy and interstitial lung disease, which responds well to methylprednisolone and intravenous immunoglobulin.

Long-term clinical course of anti-glycyl tRNA synthetase (anti-EJ) antibody-related interstitial lung disease pathologically proven by surgical lung biopsy.

BACKGROUND: Anti-glycyl-tRNA synthetase (anti-EJ) antibody is occasionally positive in patients with interstitial lung disease (ILD). We aimed to define the clinical, radiological and pathological features of patients with anti-EJ antibody-positive ILD (EJ-ILD). METHODS: We retrospectively analyzed the medical records of 12 consecutive patients with EJ-ILD who underwent surgical lung biopsy. RESULTS: The median follow-up time was 74 months (range, 17-115 months). The median age was 62 years (range, 47-75 years). Seven of 12 patients were female. Eight patients presented with acute onset. Six patients eventually developed polymyositis/dermatomyositis. On high-resolution computed tomography, consolidation and volume loss were predominantly observed in the middle or lower lung zone. Nine patients presented pathologically nonspecific interstitial pneumonia with organizing pneumonia, alveolar epithelial injury and prominent interstitial cellular infiltrations whereas the other three patients were diagnosed with unclassifiable interstitial pneumonia. Although all patients but one improved with the initial immunosuppressive therapy, five patients relapsed. When ILD relapsed, four of the five patients were treated with corticosteroid monotherapy. Four of the six patients without relapse have been continuously treated with combination therapy of corticosteroid and immunosuppressant. CONCLUSIONS: Patients with EJ-ILD often had acute onset of ILD with lower lung-predominant shadows and pathologically nonspecific interstitial pneumonia or unclassifiable interstitial pneumonia with acute inflammatory findings. Although the disease responded well to the initial treatment, relapse was frequent. Because of the diversity of the clinical courses, combination therapy of corticosteroid and immunosuppressant should be on the list of options to prevent relapse of EJ-ILD.

Pulmonary pathologic manifestations of anti-glycyl-tRNA synthetase (anti-EJ)-related inflammatory myopathy.

AIMS: Antisynthetase syndromes are a subset of the idiopathic inflammatory myopathies characterised by the presence of autoantibodies to aminoacyl transfer-RNA synthetases (ARS) and monotypic clinical features including Raynaud phenomenon, fever, non-erosive inflammatory arthritis and hyperkeratotic skin changes ('mechanic's hands'). Interstitial lung disease (ILD) is particularly common in ARS syndromes, affecting up to 90% of patients. METHODS: Four patients with ARS syndrome who possessed anti-glycyl-tRNA synthetase (anti-EJ) autoantibodies were retrieved from the University of Pittsburgh database. We report their clinical, radiographic and histopathologic findings. RESULTS: Patients presented with dyspnoea accompanied by Raynaud phenomenon and 'mechanic's hands'. Lung disease was the first manifestation in all four patients (100%) who were all amyopathic. High-resolution CT of the chest showed patchy opacities and consolidations in two patients (50%) whose surgical lung biopsies revealed organising diffuse alveolar damage (DAD), and lower lung zone predominant reticular infiltrates and traction bronchiectasis without honeycomb change in two patients (50%) whose surgical lung biopsies revealed usual interstitial pneumonia (UIP). Mild lymphoplasmacytic inflammation and few scattered lymphoid aggregates were present, but we found no pathognomonic histopathologic features of anti-EJ ARS syndrome. Serologic testing revealed no other autoantibodies. All patients responded to immunosuppressive therapy. CONCLUSIONS: Identifying ARS-associated autoantibodies in ILD patients with or without myopathy is desirable because patients may respond well to immunosuppressive therapy, and their prognosis is better than that of patients with idiopathic forms of DAD or UIP.

Establishment of an ELISA to detect anti-glycyl-tRNA synthetase antibody (anti-EJ), a serological marker of dermatomyositis/polymyositis and interstitial lung disease.

BACKGROUND: The aminoacyl transfer RNA synthetases (ARSs) are a group of enzymes that charge amino acids to the cognate transfer RNA during the translation process. Previous reports demonstrated autoantibodies to 8 different ARS. Although anti-glycyl-tRNA synthetase antibodies (anti-EJ) are mainly found in patients with inflammatory myopathy, information on their clinical significances is limited, partly due to a lack of commercially available tests. METHODS: We developed an ELISA and immunoprecipitation method by using recombinant EJ protein to detect the anti-EJ of 453 patients with various autoimmune connective tissue diseases (ACTDs). We also studied the influence of 3 cytokines-IL-1ß, IFN-γ and IFN-α-on the level of EJ mRNA and protein expressed by human fetal lung fibroblasts. RESULTS: Five patients were positive for anti-EJ. Although 3 of these patients had dermatomyositis/polymyositis, the other 2 patients did not have myositis. The three patients with high levels of anti-EJ antibodies in ELISA were complicated with interstitial lung disease. There was no significant change in the level of EJ protein expressed by human fetal lung fibroblasts stimulated by the cytokines. CONCLUSION: We developed an ELISA to detect anti-EJ by using recombinant protein. This easy-to-use ELISA could help clarify the clinical significance of anti-EJ in ACTDs.

[Anti-synthetase syndrome: anti-PL-7, anti-PL-12 and anti-EJ]. / Síndrome antissintetase: anti-PL-7, anti-PL-12 e anti-EJ.

OBJECTIVES: Due to the scarcity of studies in the literature, we conducted an analysis of a series of patients with the anti-PL-7, PL-12 and EJ types of antisynthetase syndrome (ASS). METHODS: We conducted a retrospective cohort study of 20 patients with ASS (8 with anti-PL-7, 6 with PL-12, 6 with EJ) monitored in our department between 1982 and 2012. RESULTS: The mean patient age at disease onset was 38.5 ± 12.9 years, and the disease duration was 4.5 ± 6.4 years. Of all the patients, 70% were white and 85% were female. Constitutional symptoms occurred in 90% of cases. All patients presented objective muscle weakness in the limbs; in addition, 30% were bedridden and 65% demonstrated high dysphagia at diagnosis. Joint and pulmonary involvement and Raynaud's phenomenon occurred in 50%, 40% and 65% of cases, respectively, with more than half of the patients presenting incipient pneumopathy, ground-glass opacity and/or pulmonary fibrosis. There were no cases of neurological and/or cardiac involvement. All patients received prednisone or other immunosuppressants depending on tolerance, side effects and/or disease refractoriness. Importantly, patients with the anti-EJ type of ASS demonstrated higher rates of recurrence. Two patients died during follow-up, and 1 patient had breast cancer at the time of diagnosis. CONCLUSIONS: ASS (anti-PL-7, PL-12 and EJ) was found to predominantly affect white women. Although the autoantibodies described in the present study are more related to pulmonary than joint involvement, our patients showed a significant percentage of both types of involvement and a high percentage of myopathy. We also observed a low mortality rate.

Síndrome antissintetase: anti-PL-7, anti-PL-12 e anti-EJ / Anti-synthetase syndrome: anti-PL-7, anti-PL-12 and anti-EJ

OBJETIVOS: Devido à escassez de trabalhos na literatura, realizamos análise de uma série de pacientes com síndrome antissintetase (SAS) do tipo anti-PL-7, PL-12 e EJ. MÉTODOS: Estudo de coorte, retrospectivo, envolvendo 20 pacientes com SAS (8 com anti-PL-7, 6 com PL-12, 6 com EJ), em acompanhamento em nosso serviço, entre 1982 e 2012. RESULTADOS: A média de idade dos pacientes ao início da doença foi de 38,5 ± 12,9 anos, e a duração da doença de 4,5 ± 6,4 anos. Setenta por cento dos pacientes eram brancos e 85% eram mulheres. Sintomas constitucionais ocorreram em 90% dos casos. Todos apresentavam fraqueza muscular objetiva dos membros; ao diagnóstico, 30% encontravam-se acamados e 65% com disfagia alta. Envolvimento articular, pulmonar e fenômeno de Raynaud ocorreram, respectivamente, em 50%, 40% e 65% dos casos; mais da metade dos pacientes apresentava pneumopatia incipiente, opacidade em vidro-fosco e/ou fibrose pulmonar. Não houve casos de envolvimento neurológico e/ou cardíaco. Todos receberam prednisona e, como poupadores dessa medicação, diferentes imunossupressores, dependendo da tolerância, efeitos colaterais e/ou refratariedade da doença. De relevância, os pacientes com anti-EJ apresentaram maiores taxas de recidiva. Dois pacientes evoluíram para óbito ao longo do seguimento, e um paciente teve neoplasia mamária na ocasião do diagnóstico da doença. CONCLUSÕES: A SAS (anti-PL-7, PL-12 e EJ) afetou predominantemente mulheres brancas. Embora os autoanticorpos descritos no presente estudo estejam mais relacionados com o acometimento pulmonar comparativamente ao articular, nossos pacientes apresentaram uma porcentagem significativa de ambos e com percentagem alta de miopatia. Além disso, houve menor taxa de mortalidade.

OBJECTIVES: Due to the scarcity of studies in the literature, we conducted an analysis of a series of patients with the anti-PL-7, PL-12 and EJ types of antisynthetase syndrome (ASS). METHODS: We conducted a retrospective cohort study of 20 patients with ASS (8 with anti-PL-7, 6 with PL-12, 6 with EJ) monitored in our department between 1982 and 2012. RESULTS: The mean patient age at disease onset was 38.5 ± 12.9 years, and the disease duration was 4.5 ± 6.4 years. Of all the patients, 70% were white and 85% were female. Constitutional symptoms occurred in 90% of cases. All patients presented objective muscle weakness in the limbs; in addition, 30% were bedridden and 65% demonstrated high dysphagia at diagnosis. Joint and pulmonary involvement and Raynaud's phenomenon occurred in 50%, 40% and 65% of cases, respectively, with more than half of the patients presenting incipient pneumopathy, ground-glass opacity and/or pulmonary fibrosis. There were no cases of neurological and/or cardiac involvement. All patients received prednisone or other immunosuppressants depending on tolerance, side effects and/or disease refractoriness. Importantly, patients with the anti-EJ type of ASS demonstrated higher rates of recurrence. Two patients died during follow-up, and 1 patient had breast cancer at the time of diagnosis. CONCLUSIONS: ASS (anti-PL-7, PL-12 and EJ) was found to predominantly affect white women. Although the autoantibodies described in the present study are more related to pulmonary than joint involvement, our patients showed a significant percentage of both types of involvement and a high percentage of myopathy. We also observed a low mortality rate.

Direct characterization of target podocyte antigens and auto-antibodies in human membranous glomerulonephritis: Alfa-enolase and borderline antigens.

The identification of glomerular auto-antigens in idiopathic human membranous glomerulonephritis (MGN) is a crucial step towards the definition of the mechanisms of the disease. Recent 'in vivo' studies demonstrated a heterogeneous composition of glomerular immune-deposits in MGN biopsies only a part of which have been characterized. We studied with a proteomical approach IgGs eluted from laser capture microdissected glomeruli of 8 MGN patients and showed the existence of other three immune proteins in MGN glomeruli (α-enolase, elongation factor 2 and Glycyl Aminoacyl-tRNA Synthetase). One of these, i.e. α-enolase, fulfilled all criteria for being considered an auto-antigen. Specific IgG1 and IgG4 reacting with podocyte α-enolase were, in fact, eluted from microdissected glomeruli and Confocal- and Immuno Electron-Microscopy showed co-localization of α-enolase with IgG4 and C5b-9 in immune-deposits. Serum levels of anti a-enolase IgG4 were determined in 131 MGN patients and were found elevated in 25% of cases. Overall, our data demonstrate that glomerular α-enolase is a target antigen of autoimmunity in human MGN. Circulating anti α-enolase auto-antibodies can be detected in sera of a significant quota of MGN patients. Like other auto-antigens, α-enolase may be implicated in the pathogenesis of human MGN.

Unusually high frequency of autoantibodies to PL-7 associated with milder muscle disease in Japanese patients with polymyositis/dermatomyositis.

OBJECTIVE: Autoantibodies to aminoacyl transfer RNA synthetases, such as histidyl (Jo-1), threonyl (PL-7), alanyl (PL-12), glycyl (EJ), and isoleucyl (OJ), are closely associated with a subset of patients with polymyositis/dermatomyositis (PM/DM) complicated by interstitial lung disease (ILD). Anti-Jo-1 is by far the most common, found in 15-25% of patients with PM/DM, whereas the other types are found in only approximately 3% of these patients. In this study, the clinical associations of these autoantibodies in Japanese patients with PM/DM were investigated. METHODS: The diagnoses of PM/DM and amyopathic DM (ADM) were based on the Bohan and Peter criteria and Sontheimer's definition, respectively. Sera from 36 Japanese patients with PM/DM (13 with PM, 20 with DM, 3 with ADM) were screened by immunoprecipitation and by enzyme-linked immunosorbent assay (for Jo-1). Clinical and laboratory data were collected. RESULTS: The frequencies of autoantibodies to Jo-1 (22%) and to EJ, OJ, and PL-12 (3-6%) were similar to those found in previous studies, including studies of Japanese subjects. However, anti-PL-7 was found in 17% of patients, in contrast to a frequency of 1-4% in previous studies (P < 0.02-0.0002). The 6 anti-PL-7-positive patients were not related, and no skewing in year or month of disease development, place of residence or work, or occupation was found. All patients had ILD, consistent with the clinical features of antisynthetase-positive patients. The patients with anti-PL-7 had lower serum muscle enzyme levels and milder muscle weakness (P < 0.05) compared with anti-Jo-1-positive patients. CONCLUSION: Anti-PL-7 was found at an unusually high frequency in this group of Japanese patients with myositis. Although anti-PL-7, similar to anti-Jo-1, is associated with PM/DM with ILD, muscle involvement in the patients with anti-PL-7 appeared to be milder than that in the anti-Jo-1 subset.

Diagnosis of idiopathic myositis: value of 99mtechnetium pyrophosphate muscle scintigraphy and magnetic resonance imaging in targeted muscle biopsy.

Our objective was to study the value of 99mtechnetium-pyrophosphate (99mTc-PYP) muscle scintigraphy and magnetic resonance imaging (MRI) in detecting areas of likely muscle inflammation and in increasing the rate of positive muscle biopsies in patients with suspected myositis. The results showed that in 13 out of 13 patients with clinical and/or signs of inflammatory muscle disease, increased 99mTc-PYP uptake was demonstrated at different muscle sites 3 h after isotope injection. Subsequent MRI of symmetric muscle areas with enhanced 99mTc-PYP uptake revealed signal patterns suggesting inflammation in all cases. Biopsy of these targeted muscles demonstrated characteristic histopathologic signs of muscle inflammation in 9 out of 13 patients. Four of these 9 patients had clinically atypical disease or did not show elevated creatine phosphokinase levels. Seven of these 9 patients had not been pretreated with corticosteroids. In 4 patients only muscle fiber atrophy and/or necrosis without cellular infiltrations was seen. These 4 patients had received either high doses of corticosteroids or low doses over longer periods of time before muscle biopsy. In conclusion, the combination of 99mTc-PYP muscle scintigraphy and MRI demonstrated muscle areas with maximum inflammatory signal patterns. Targeting of muscles by MRI only will probably yield reliable results of muscle biopsy in cases of clinically and serologically characteristic myositis. 99mTc-PYP muscle scintigraphy may provide useful initial information about localization of inflamed muscle tissue, especially in atypical disease. Treatment with corticosteroids prior to histologic diagnosis may abolish inflammatory infiltrations in affected muscle tissue.

Autoantibodies to glycyl-transfer RNA synthetase in myositis. Association with dermatomyositis and immunologic heterogeneity.

OBJECTIVE: To elucidate the clinical significance and immunologic heterogeneity of anti-glycyl-transfer RNA (tRNA) synthetase antibodies in polymyositis/dermatomyositis (PM/DM). METHODS: Sera from 345 patients with rheumatic diseases, including 91 with myositis, were examined using immunoprecipitation assays. Autoantibodies to aminoacyl-tRNA synthetases were further analyzed with 2-dimensional RNA fractionation and via inhibition of in vitro aminoacylation. RESULTS: Serum from 1 patient with DM and interstitial lung disease immunoprecipitated glycyl-tRNA synthase along with only 1 of 4 associated tRNAs, in comparison with control anti-glycyl-tRNA synthetase antibodies, which bound the enzyme along with all 4 associated tRNAs. Immunoblotting findings and a lack of in vitro inhibition aminoacylation of tRNA(gly) by serum from this patient also suggested differences between the epitope specificity of this serum and that of other sera with anti-glycyl-tRNA synthetase antibodies. CONCLUSION: This identification of antibodies to glycyl-tRNA synthetase from a patient with DM underscores the association of this specificity with the disease. The finding that these antibodies bound an epitope outside the active site of the synthetase enzyme, in contrast to most anti-aminoacyl-tRNA synthetases, emphasizes the immunologic heterogeneity of these autoantibodies.

The glycyl-tRNA synthetase of Chlamydia trachomatis.

Aminoacyl-tRNA synthetases specifically charge tRNAs with their cognate amino acids. A prototype for the most complex aminoacyl-tRNA synthetases is the four-subunit glycyl-tRNA synthetase from Escherichia coli, encoded by two open reading frames. We examined the glycyl-tRNA synthetase gene from Chlamydia trachomatis, a genetically isolated bacterium, and identified only a single open reading frame for the chlamydial homolog (glyQS). This is the first report of a prokaryotic glycyl-tRNA synthetase encoded by a single gene.