Restricted use of T cell receptor V genes in endomysial infiltrates of patients with inflammatory myopathies

Inclusion body myositis (IBM), polymyositis (PM) and dermatomyositis (DM) are diseases characterized clinically by progressive muscle weakness and histologically by T lymphocyte infiltrates in striated muscle. The pathogenetic role of these cells is proposed to be cell-mediated cytotoxicity in PM and IBM, but the exact mechanisms of their action are poorly understood. Characterization of the variable regions of T cell receptors (TcR) on the infiltrating lymphocytes may be expected to provide insights into the mechanisms of local activation of the immune system in inflammatory myopathies. Immunohistochemical analysis using a panel of monoclonal antibodies specific for 11 Vα/β TcR was performed on cryosectioned muscle biopsy specimens from eight patients with IBM, eight with PM and three with DM. In addition, TcR expression was studied in inflammatory infiltrates in skin biopsies obtained from some of the IBM patients challenged locally with tuberculin. Flow cytometry was used to assess expression of TcR on peripheral blood lymphocytes. All the patients displayed a clear restriction of TcR usage, preferentially limited to Vα2 and Vβ3 TcR families in the endomysial, but not in perivascular infiltrates, even within the same muscle specimen. Such a restriction was not found in skin punch biopsies or PBL from the same subjects. Our results suggest that T cells extravasate non-selectively to the skeletal muscle, but once there, only certain TcR families proliferate, presumably after encounter with a locally exposed superantigen.     

Difference in adhesion molecule expression (ICAM-1 and VCAM-1) in juvenile and adult dermatomyositis, polymyositis and inclusion body myositis

To assess the differential expression of adhesion molecules ICAM-1 and VCAM-1 in vessels and muscle fibers in acquired inflammatory myopathy, a series comprising thirty-seven muscle biopsy specimens from patients with JDM, fifteen with DM, fifteen with PM and seven with IBM was studied. Histochemical and immunohistochemical tests (StreptABCcomplex/HRP) for ICAM-1 and VCAM-1 (Dakopatts) were performed in serial frozen sections. ICAM-1 expression in vessels was significantly (p<0.0001) more present in JDM than PM, DM or IBM. However, in muscle fibers, ICAM-1 expression was absent in both JDM and IBM, but present in 33.4% and 40% in PM and DM respectively (p<0.0001). VCAM-1 expression in vessels was significantly more present in PM and DM than JDM and IBM (p<0.0001) while VCAM-1 expression in muscle fibers was almost absent in the four groups (p=0.2632). These findings emphasize the importance of adhesion molecules in the pathophysiology of the inflammatory myopathies, mainly the marked ICAM-1 expression in vessels in JDM, corroborating the microvascular involvement in this disease. In contrast, VCAM-1 seems not to play a major role in JDM, as previously described in PM, DM and IBM. Adhesion molecule expression in JDM presents a differential characteristic when compared to PM, DM and IBM.     

Pathogenesis and therapies of immune-mediated myopathies

The most common autoimmune muscle disorders include dermatomyositis (DM), polymyositis (PM), necrotizing autoimmune myositis (NAM) and sporadic inclusion body myositis (sIBM). DM is a complement-mediated microangiopathy leading to destruction of capillaries, hypoperfusion and inflammatory cell stress on the perifascicular regions. NAM is an increasingly recognized subacute myopathy triggered by statins, viral infections, cancer or autoimmunity with macrophages as the final effector cells causing fiber injury. PM and IBM are T cell-mediated disorders where cytotoxic CD8(+) T cells clonally expand in situ and invade major histocompatibility complex class I expressing muscle fibers. In sIBM, in addition to autoreactive T cells, there are degenerative features characterized by vacuolization and accumulation of stressor or amyloid-related misfolded proteins; an interrelationship between inflammatory and degeneration-associated molecules is prominent and enhances the cascade of pathogenic factors. These disorders are treatable, hence the need to make the correct diagnosis from the outset. The applied therapeutic strategies are outlined and the promising new agents are reviewed.     

Immune checkpoint failures in inflammatory myopathies: An overview

Dermatomyositis (DM), polymyositis (PM), inclusion body myositis (IBM), immune mediated necrotizing myopathy (IMNM) and overlap myositis (OM) are classified as inflammatory myopathies (IM) with involvement of autoimmune features such as autoreactive lymphocytes and autoantibodies. Autoimmunity can be defined as a loss in self-tolerance and attack of autoantigens by the immune system. Self-tolerance is achieved by a group of immune mechanisms occurring in central and periphal lymphoid organs and tissues, called immune checkpoints, that work in synergy to protect the body from harmful immune reactions. Autoimmune disorders appear when immune checkpoints fail. In this review, the different immune checkpoint failures are discussed in DM, PM, IBM and IMNM. Exploring research contribution in each of these immune checkpoints might help to highlight research perspectives in the field and obtain a more complete picture of IM disease pathology.     

Altered RIG‐I/DDX58‐mediated innate immunity in dermatomyositis

We investigated the molecular mechanisms involved in the pathogenesis of three inflammatory myopathies, dermatomyositis (DM), polymyositis (PM) and inclusion body myositis (IBM). We performed microarray experiments^? using microdissected pathological muscle fibres from 15 patients with these disorders and five controls. Differentially expressed candidate genes were validated by immunohistochemistry on muscle biopsies, and the altered pathways were analysed in human myotube cultures. Up‐regulation of genes involved in viral and nucleic acid recognition were found in the three myopathies but not in controls. In DM, retinoic acid‐inducible gene 1 (RIG‐I, DDX58) and the novel antiviral factor DDX60, which promotes RIG‐I‐mediated signalling, were significantly up‐regulated, followed by IFIH1 (MDA5) and TLR3. Immunohistochemistry confirmed over‐expression of RIG‐I in pathological muscle fibres in 5/5 DM, 0/5 PM and 0/5 IBM patients, and in 0/5 controls. Stimulation of human myotubes with a ligand of RIG‐I produced a significant secretion of interferon‐β (IFNβ; p < 0.05) and up‐regulation of class I MHC, RIG‐I and TLR3 (p < 0.05) by IFNβ‐dependent and TLR3‐independent mechanisms. RIG‐I‐mediated innate immunity, triggered by a viral or damage signal, plays a significant role in the pathogenesis of DM, but not in that of PM or IBM. Copyright © 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd     

Novel aspects on the contribution of T cells and dendritic cells in the pathogenesis of myositis

This review focuses on recent advances and new hypothesis in the understanding of the T and dendritic cells contribution to the pathogenesis of idiopathic inflammatory myopathies (IIMs), especially polymyositis (PM) and dermatomyositis (DM). The new data show that non-specific amplification of muscle inflammation by T lymphocyte and dendritic cells may result from the local production of cytokines and chemokines. Synergistic interactions between these factors explain some of the clinical features. The potent role of these molecules suggests their potential for therapeutic manipulation using specific inhibitors.     

Novel aspects on the contribution of T cells and dendritic cells in the pathogenesis of myositis

This review focuses on recent advances and new hypothesis in the understanding of the T and dendritic cells contribution to the pathogenesis of idiopathic inflammatory myopathies (IIMs), especially polymyositis (PM) and dermatomyositis (DM). The new data show that non-specific amplification of muscle inflammation by T lymphocyte and dendritic cells may result from the local production of cytokines and chemokines. Synergistic interactions between these factors explain some of the clinical features. The potent role of these molecules suggests their potential for therapeutic manipulation using specific inhibitors.     

Immunolocalization of protein-bound 3-nitrotyrosine in inflammatory myopathies

3-nitrotyrosine (3NT) is regarded as a "footprint" of nitric oxide generation. The study aimed at documenting the presence and distribution of 3-nitrotyrosine (3NT) in muscle tissue samples from patients with idiopathic inflammatory myopathies (IIM) as well as from those with non-inflammatory myopathies to consider whether polymyositis (PM) and dermatomyositis (DM) could be distinguished based on 3NT immunohistochemistry in muscle biopsy. Cryosections prepared from muscle biopsies of 54 patients with either IIM, i.e., PM and DM, or various non-inflammatory myopathies were immunostained using monoclonal antibody against 3NT. The 3NT immunostaining was localized to endothelial cells and their close surroundings in muscle biopsies of DM and PM patients but only in those areas of tissue sections where inflammatory cell infiltrates were present. No 3NT positivity was found in tissue sections of IIM patients without inflammatory infiltrates in the studied sample as well as in muscle tissue sections of patients with non-inflammatory myopathies. However, the endothelial cells were also positive in cases of confirmed non-inflammatory myopathies with secondary lymphocytic infiltration (myodystrophies, myasthenia gravis). Despite the pathogenetic significance, the 3NT immunohistochemistry is of low diagnostic value for the differential diagnosis of IIM in muscle biopsy.     

Diagnosis,pathogenesis and treatment of myositis: recent advances

Dermatomyositis (DM), polymyositis (PM), necrotizing myopathy (NM) and inclusion body myositis (IBM) are four distinct subtypes of idiopathic inflammatory myopathies – in short myositis. Recent studies have shed some light on the unique pathogenesis of each entity. Some of the clinical features are distinct, but muscle biopsy is indispensable for making a reliable diagnosis. The use of magnetic resonance imaging of skeletal muscles and detection of myositis‐specific autoantibodies have become useful additions to our diagnostic repertoire. Only few controlled trials are available to substantiate current treatment approaches for myositis and hopes are high that novel modalities will become available within the next few years. In this review we provide an up‐to‐date overview of the pathogenesis and diagnostic approach of myositis. We aim to present a guide towards therapeutic and general management.     

Differential Immunohistological Features of Inflammatory Myopathies and Dysferlinopathy

This study was performed in order to characterize the types of the infiltrating cells, and the expression profiles of major histocompatibility complex (MHC) class I and membrane attack complex (MAC) in patients with inflammatory myopathies and dysferlinopathy. Immunohistochemical stains were performed using monoclonal antibodies against several inflammatory cell types, MHC class I, and MAC in muscles from inflammatory myopathies and dysferlinopathy. There was significant difference in the types of infiltrating cells between polymyositis (PM), dermatomyositis (DM), and dysferlinopathy, including significantly high CD4+/CD8+ T cell ratio and B/T cell ratio in DM. In dysferlinopathy, CD4+ T cells were the most abundant and the proportions of infiltrating cell types were similar to those of DM. MHC class I was expressed in muscle fibers of PM and DM regardless of the presence of inflammatory infiltrates. MAC was expressed in necrotic fibers and vessels of PM and DM. One patient with early stage DM had a MAC deposits on endomysial capillaries. In dysferlinopathy, MAC deposit was also observed on the sarcolemma of nonnecrotic fibers. The analysis of inflammatory cells, MHC class I expressions and MAC deposits may help to differentiate dysferlinopathy from idiopathic inflammatory myopathy.     

The type I interferon system in idiopathic inflammatory myopathies

Polymyositis (PM), dermatomyositis (DM) and inclusion body myositis (IBM) are chronic inflammatory diseases that are characterized by muscle weakness and inflammatory cells in muscle tissue. Autoantibodies are common, some of them are specific for myositis, the most frequent being the anti-Jo-1 antibody which is associated not only with myositis but also with interstitial lung disease and arthritis. A role of type I interferons in disease mechanisms of myositis was first supported by the reported onset of PM and DM during treatment with type I interferon. More recently an interferon signature has been reported in muscle tissue of DM and PM patients both as gene and protein expression, and type I IFN expression in peripheral blood cells seems to correlate with disease activity. Different mechanisms could induce type I interferon in PM and DM like viral infections or endogenous factors as suggested by the observation that sera from myositis patients with anti-Jo-1 antibodies as well as anti-SSA and anti-SSB antibodies have an interferon inducible capacity. Accumulating data indicate a role of the type I interferon in myositis, particularly in juvenile and adult DM and in anti-Jo-1 or anti-SSA positive PM.     

The pathological diagnosis of specific inflammatory myopathies.

Pathological diagnosis of dermatomyositis (DM), polymyositis (PM), and inclusion body myositis (IBM) should be possible in almost all cases when an appropriately involved muscle is biopsied. DM shows characteristic patterns of muscle fiber damage and capillary damage. Lymphocytes and macrophages are seen in PM and IBM partially invading non-necrotic fibers. IBM is also characterized by rimmed vacuoles with membranous whorls, characteristic masses of filaments in cytoplasm and sometimes in nuclei, and grouped atrophic fibers. Muscle fiber damage in PM is more variable. Inflammatory myopathy can be associated with HTLV-1 and HIV infection. In the latter a strong resemblance to PM is reported. Separate, still less well characterized forms of inflammatory myopathy occur in young children.     

Common pathways of autoimmune inflammatory myopathies and genetic neuromuscular disorders

It has been shown that many hereditary motor neuron diseases are caused by mutation of RNA processing enzymes. Survival of motor neuron 1 (SMN1) is well-known as a causative gene for spinal muscular atrophy (SMA) and mutations of glycyl- and tyrosyl-tRNA synthetases are identified as a cause of distal SMA and Charcot–Marie–Tooth disease. Why and how the dysfunction of these ubiquitously expressed genes involved in RNA processing can cause a specific neurological disorder is not well understood. Interestingly, SMN complex has been identified recently as a new target of autoantibodies in polymyositis (PM). Autoantibodies in systemic rheumatic diseases are clinically useful biomarkers associated with a particular diagnosis, subset of a disease, or certain clinical characteristics. Many autoantibodies produced in patients with polymyositis/dermatomyositis (PM/DM) target RNA–protein complexes such as aminoacyl tRNA synthetases. It is interesting to note these same RNA–protein complexes recognized by autoantibodies in PM/DM are also responsible for genetic neuromuscular disease. Certain RNA–protein complexes are also targets of autoantibodies in paraneoplastic neurological disorders. Thus, there are several interesting associations between RNA-processing enzymes and neuromuscular disorders. Although pathogenetic roles of autoantibodies to intracellular antigens are generally considered unlikely, understanding the mechanisms of antigen selection in a particular disease and specific neurological symptoms caused by disruption of ubiquitous RNA-processing enzyme may help identify a common path in genetic neuromuscular disorders and autoimmunity in inflammatory myopathies.     

Anti-Jo-1 antibody positive polymyositis—successful therapy with leflunomide

Idiopathic inflammatory myopathies (IM), including dermatomyositis (DM) and polymyositis (PM), are a group of systemic rheumatologic diseases of unknown etiology characterized by chronic myositis. Antisynthetase antibodies such as the anti-Jo-1 antibody are known to be highly specific for inflammatory myopathies. Patients with this antibody frequently show a combination of symptoms including interstitial lung disease, fever, polyarthritis, myositis, Raynaud's phenomenon and “mechanic's hands”. In the management of PM with anti-Jo-1 antibody, immunosuppressive agents are used to control the disease. Leflunomide is a new immunosuppressive drug recently introduced in the treatment of rheumatoid and psoriatic arthritis. Here, we report two cases of female patients with PM and anti-Jo-1 antibodies, who were successfully treated with leflunomide.     

Anti-Jo-1 antibody positive polymyositis--successful therapy with leflunomide

Idiopathic inflammatory myopathies (IM), including dermatomyositis (DM) and polymyositis (PM), are a group of systemic rheumatologic diseases of unknown etiology characterized by chronic myositis. Antisynthetase antibodies such as the anti-Jo-1 antibody are known to be highly specific for inflammatory myopathies. Patients with this antibody frequently show a combination of symptoms including interstitial lung disease, fever, polyarthritis, myositis, Raynaud's phenomenon and "mechanic's hands". In the management of PM with anti-Jo-1 antibody, immunosuppressive agents are used to control the disease. Leflunomide is a new immunosuppressive drug recently introduced in the treatment of rheumatoid and psoriatic arthritis. Here, we report two cases of female patients with PM and anti-Jo-1 antibodies, who were successfully treated with leflunomide.     

Can tissue transglutaminase be a marker of idiopathic inflammatory myopathies?

In the normal striated muscle, tissue transglutaminase (TG2) content is vestigial. However, this protein's presence has been reported to occur in myoblasts and myotubes during the fetal period. Its increased expression has been also found in the muscle tissue in the course of sporadic inclusion body myositis, as well as in polymyositis (PM) and dermatomyositis (DM), which are considered to be diseases of immunological origin. Based on in vitro studies, a substantial TG2 role in the infiltration of some T cell subsets into inflamed tissues has been suggested lately. In this study, the immunohistochemical reactions in the guinea pig experimental myositis specimens and in the ones from PM/DM patients were compared. The guinea pig tissue specimens were taken from muscles affected by experimental myositis induced by intramuscular injections of: 1/sera from 30 neoplasm patients with no metastases; 2/sera from 10 healthy people; 3/sera from 2 DM patients; 4/neuropeptides (SP, NPY or VIP) and from 5/the muscles affected by the reversed passive Arthus reaction (RPAR). The immunostaining for TG2 revealed substantial presence of this protein in single, damaged muscle fibers and a weak reaction in regenerating fibers appearing in PM/DM patients' specimens. From among experimental myositis specimens, a very intensive reaction appeared only in the damaged and regenerating muscle fibers present in the slides from guinea pig muscles injected with DM patients' sera. Such results suggest some presence of a specific factor(s) (the one(s) responsible for TG2 expression in the damaged muscle fibers) in DM patients' sera. The results suggest that transglutaminase can be a marker of inflammatory myopathies. A probable correlation between TG2 expression in muscles and organismal immunological factors, including the complement activation status, requires additional studies.