Cells In Inclusion Body Myositis Research Articles

Clinical Correlates of Blood KLRG1+ T cells in Inclusion Body Myositis (2802)

Clinical Correlates of Blood KLRG1+ T cells in Inclusion Body Myositis (2802)

AUTOIMMUNE MYOPATHIES: P.306 Clinical correlates of KLRG1+ T cells in inclusion body myositis

Recent published data has firmly highlighted the role of immune dysfunction as possibly the primary pathogenic mechanism in inclusion body myositis (IBM), as clonal highly differentiated ``immunosenescent'' CD8+ T cells, phenotypically resembling terminally differentiated effector memory CD45RA+ T cells (TEMRA cells), are seen in circulation in over 75% of cases. The most prominent surface marker of these cells is killer cell lectin-like receptor G1 (KLRG1). The objective of this study is to correlate disease features, such as disease phenotype and severity, in IBM with peripheral blood levels of killer cell lectin-like receptor G1 (KLRG1)-expressing T cells.

Where are we moving in the classification of idiopathic inflammatory myopathies?

Discoveries of myositis-specific antibodies, transcriptomic signatures, and clinicoseropathological correlation support classification of idiopathic inflammatory myopathies (IIM) into four major subgroups: dermatomyositis, immune-mediated necrotizing myopathy (IMNM), antisynthetase syndrome (ASS), and inclusion body myositis (IBM) whereas leaving polymyositis as a historical nonspecific diagnosis of exclusion. This review summarizes and comments on recent knowledge regarding the major subgroup of IIM. Type 1 interferon (IFN1) pathway activation is the most prominent in dermatomyositis whereas type 2 interferon (IFN2) pathway activation is high in IBM and ASS; neither pathway is distinct in IMNM. Myxovirus-resistant protein A, IFN1 surrogate marker, is now one of definite dermatomyositis muscle biopsy criteria in the new 2018 European Neuromuscular Centre classification of dermatomyositis; the classification emphasizes on different categorization with and without dermatomyositis-specific antibody result. Novel HLA loci associated with anti-TIF1-γ, anti-Mi-2, and anti-Jo-1 antibodies in Caucasian population are identified. Associations of chaperon-assisted selective autophagy (CASA) and complement-mediated autoimmunity in IMNM as well as highly differentiated T cells in IBM are discovered. Current IIM classification requires integrated clinicoseropathological approaches. Additional information, such as transcriptomics, HLA haplotyping, and potential biomarkers help tailoring categorization that may have future diagnostic and therapeutic implications.

Highly differentiated cytotoxic T cells in inclusion body myositis.

Inclusion body myositis is a late onset treatment-refractory autoimmune disease of skeletal muscle associated with a blood autoantibody (anti-cN1A), an HLA autoimmune haplotype, and muscle pathology characterized by cytotoxic CD8+ T cell destruction of myofibres. Here, we report on translational studies of inclusion body myositis patient muscle compared with a diverse set of other muscle disease samples. Using available microarray data on 411 muscle samples from patients with inclusion body myositis (n = 40), other muscle diseases (n = 265), and without neuromuscular disease (normal, n = 106), we identified a signature of T-cell cytotoxicity in inclusion body myositis muscle coupled with a signature of highly differentiated CD8 T-cell effector memory and terminally differentiated effector cells. Further, we examined killer cell lectin-like receptor G1 (KLRG1) as a marker of this population of cells, demonstrated the correlation of KLRG1 gene expression with lymphocyte cytotoxicity across 28 870 human tissue samples, and identified the presence of KLRG1 on pathogenic inclusion body myositis muscle invading T cells and an increase in KLRG1 expressing T cells in inclusion body myositis blood. We examined inclusion body myositis muscle T-cell proliferation by Ki67 immunohistochemistry demonstrating that diseased muscle-invading T cells are minimally or non-proliferative, in accordance with known properties of highly differentiated or terminally differentiated T cells. We found low expression of KLRG1 on infection-protective human lymphoid tissue central memory T cells and autoimmune-protective human blood regulatory T cells. Targeting highly differentiated cytotoxic T cells could be a favourable approach to treatment of inclusion body myositis.

Early disintegration of myonuclear fibrous lamina in inclusion body myositis: Ultrastructural and immunohistochemical studies

AbstractObjectiveMorphological analyses to assess the integrity of myonuclear surface structures in muscle biopsies from patients with inclusion body myositis (IBM) and related disorders were carried out to find clues to the causes of IBM.MethodsMuscle biopsies from 26 patients (seven with IBM, five polymyositis, three dermatomyositis, one hereditary inclusion body myopathy associated with Paget disease and front‐temporal dementia, three with other non‐inflammatory myopathies, four with no pathological abnormalities and three type 2 fiber atrophy only) were assessed by measuring lengths of clearly identifiable muscle outer (ONM) and inner nuclear membranes (INM), and fibrous laminae (FL) on electron micrographs, and grading severity of degenerative changes in the sarcoplasm into three stages. The nuclei of capillary endothelial cells were also examined and lamin A/C, a major constituent of FL, localized immunohistochemically.ResultsCompared with patients with no pathology or type 2 fiber atrophy only, polymyositis had significantly less ONM, INM and FL at an advanced stage of degeneration. In dermatomyositis, ONM was moderately decreased. In IBM, ONM, INM and FL were decreased severely from early stages of muscle fiber degeneration. In the one case with inclusion body myopathy associated with Paget disease and front‐temporal dementia, all three layers, particularly ONM, were decreased. No significant changes were observed in the nuclei of capillary endothelial cells in IBM or other conditions. In IBM, there was less lamin A/C in myonuclei than in capillary endothelial cell nuclei.ConclusionsIn IBM, shorter lengths of myonuclear surface structures, particularly of FL, were observed from an early stage of degeneration. Early disintegration of FL might reflect an essential pathomechanism of IBM.

Expanded T cell receptor Vβ–restricted T cells from patients with sporadic inclusion body myositis are proinflammatory and cytotoxic CD28null T cells

Sporadic inclusion body myositis (IBM) is characterized by T cell infiltrates in muscle tissue, but their functional role is unclear. Systemic signs of inflammation are lacking, and the absence of beneficial effects following immunosuppression has challenged the notion of a role for the immune system. This study was undertaken to investigate the phenotype and functionality of T cells, specifically a subset of proinflammatory, cytotoxic, and apoptosis-resistant T cells defined as CD28(null) T cells, in the pathogenesis of sporadic IBM. A cohort of 27 patients with sporadic IBM was analyzed for the frequency of circulating and muscle-infiltrating CD28(null) T cells. The T cell receptor (TCR) V(β) usage was determined using flow cytometry and immunohistochemistry. Anti-CD3-stimulated peripheral blood mononuclear cells were analyzed for intracellular interferon-γ and cytotoxic potential by flow cytometry. We found striking accumulations of both CD8+CD28(null) and CD4+CD28(null) T cells, which represented the TCR V(β) -expanded T cells in sporadic IBM. Such CD28(null) T cells were abundant both in the inflamed muscle tissue and in the circulation. Although the specific TCR V(β) expansions varied between patients, both CD8+CD28(null) and CD4+CD28(null) T cells consistently displayed a highly proinflammatory and cytotoxic potential. Our results suggest that CD28null T cell expansions represent the previously described expanded T cell subsets in sporadic IBM, and their proinflammatory capacity and presence in both muscle tissue and the circulation may imply a role of immune activation in sporadic IBM. In addition, CD4+CD28(null) T cells may exert cytotoxic effects directly on muscle fibers due to a cytotoxic potential similar to that in CD8+ T cells.

Shared blood and muscle CD8+ T-cell expansions in inclusion body myositis

Inclusion body myositis (IBM) is the most frequent inflammatory myopathy over the age of fifty. Pathological findings suggest that two processes may contribute to IBM pathogenesis: a primary degenerative process affecting muscle fibre and/or an autoimmune process mediated by major histocompatibility complex (MHC) class-I-restricted cytotoxic CD8+ T cells. Previous studies have demonstrated that muscle-infiltrating CD8+ T cells in IBM display restricted expression of T-cell receptor (TCR)-BV families or evidenced oligoclonal T-cell expansions. This study was performed to investigate whether blood T cells similarly exhibit clonal expansions due to the recirculation of muscle-infiltrating T cells in the periphery. For this, we studied the T-cell repertoire of 17 IBM patients by complementarity-determining-region (CDR) 3 length distribution (immunoscope) analysis of TCR-B transcripts. Mean age was 68 years (range 53-88) and mean duration of the disease was 6.5 years (2-20). Oligoclonal T-cell expansions were observed in the blood of IBM patients. The quantitative average perturbation D index was significantly increased in IBM patients [D = 13.7% +/- 1.2%, mean +/- standard error of measurement (SEM)] as compared with 17 age-matched controls suffering from connective tissue diseases not associated with T-cell repertoire perturbation, that is, dermatomyositis (DM) and systemic sclerosis (9.3 +/- 0.6%, P < 0.005). Nevertheless, there was no correlation between the level of blood perturbation and muscle inflammation. Sorting experiments showed that these perturbations were due to oligoclonal expansions of CD8+ T cells. In the three IBM patients analysed, we could relate the blood expansions to T-cell clones also found in muscle. The clonally expanded blood T cells dramatically responded to interleukin-2 (IL-2) in vitro, suggesting that they had been primed in vivo, presumably in response to yet unknown muscle auto-antigens. Together, our results indicate that clonally expanded muscle-infiltrating CD8+ T cells re-circulate in the blood and support the concept of a CD8+ T-cell-mediated autoimmune component in IBM, similarly to what is observed in polymyositis (PM).

Discovering statistically significant pathways in expression profiling studies

Accurate and rapid identification of perturbed pathways through the analysis of genome-wide expression profiles facilitates the generation of biological hypotheses. We propose a statistical framework for determining whether a specified group of genes for a pathway has a coordinated association with a phenotype of interest. Several issues on proper hypothesis-testing procedures are clarified. In particular, it is shown that the differences in the correlation structure of each set of genes can lead to a biased comparison among gene sets unless a normalization procedure is applied. We propose statistical tests for two important but different aspects of association for each group of genes. This approach has more statistical power than currently available methods and can result in the discovery of statistically significant pathways that are not detected by other methods. This method is applied to data sets involving diabetes, inflammatory myopathies, and Alzheimer's disease, using gene sets we compiled from various public databases. In the case of inflammatory myopathies, we have correctly identified the known cytotoxic T lymphocyte-mediated autoimmunity in inclusion body myositis. Furthermore, we predicted the presence of dendritic cells in inclusion body myositis and of an IFN-alpha/beta response in dermatomyositis, neither of which was previously described. These predictions have been subsequently corroborated by immunohistochemistry.

Expression of Bcl-2 in inclusion body myositis.

On the background of the possible role of the anti-apoptotic protein Bcl-2 to inhibit apoptosis induced by the Fas/Fas ligand system in inflammatory myopathies we investigated the expression of Bcl-2 in inclusion body myositis (IBM). We examined muscle tissue from seven IBM patients and controls by immunocytochemistry using antibodies against Bcl-2, Fas (a member of the tumor necrosis factor receptor family) and the regeneration marker, neural cell adhesion molecule (N-CAM). We also investigated the occurrence of DNA fragmentation by the terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL)-method. Both Bcl-2 and Fas were up-regulated in muscle fibers in IBM and disease controls. Bcl-2 was expressed by regenerating muscle fibers while Fas was expressed by non-regenerating muscle fibers associated with inflammatory cell infiltrates. Bcl-2 and Fas were also expressed by inflammatory cells. There were scattered TUNEL positive nuclei and most of these appeared to be inflammatory cells. The low occurrence of apoptotic myonuclei is not related to Bcl-2 expression, which is confined to regenerating muscle cells in IBM and other myopathies.

Oligoclonal expansion of muscle infiltrating T cells in inclusion body myositis

Inclusion body myositis (IBM) is the most common muscle disease affecting individuals over 50 years of age. An important feature of IBM is invasion of muscle fibers by T cells. The muscle infiltrating T cells show a restricted usage of variable (V) α/ β gene families. In this study we have investigated the clonality of T cells using two of the predominant V β families i.e. V β3 and V β8 in three patients with IBM. The study was performed by reverse transcription and polymerase chain reaction (RT-PCR) analysis, followed by cloning and sequencing of the T cell receptor complementarity determining region 3. We found oligoclonal expansion of V β3 bearing muscle infiltrating T cells in two patients and of V β8 in one patient, supporting the concept that antigen stimulated T cells are important in the pathogenesis of IBM. Results of HLA typing indicated a genetic predisposition for the disease by the presence of DR3, DR52 and DQB1 *0201/0202 in all three patients.

Cytotoxic mechanisms in inflammatory myopathies. Co-expression of Fas and protective Bcl-2 in muscle fibres and inflammatory cells.

Expression of the Fas 'death receptor', Fas (CD95/APO-1) renders cells susceptible to programmed cell death ('apoptosis'), whereas Bcl-2 protects cells from apoptosis. Using fluorescence immunohistochemistry, we analysed Fas and Bcl-2 expression in muscle from five patients with polymyositis (PM), four patients with inclusion body myositis (IBM), three patients with dermatomyositis (DM), three patients with Duchenne muscular dystrophy (DMD) and three nonmyopathic controls. Fas (CD95) and Bcl-2 were not detected in control muscle, but expressed in muscle fibres and inflammatory cells in PM, IBM, DM and DMD. The proportion of Fas+ muscle fibres ranged from < 1 to 50%, and was higher in PM and IBM than in DM and DMD. On average, the Fas+ muscle fibres were smaller (median diameter, 10 microns; range, 7-32 microns) than the Fas- fibres (median, 36 microns; range, 10-60 microns). Less than 10% of the Fas+ muscle fibres co-expressed the regeneration marker CD56 (neural cell adhesion molecule N-CAM). In PM and IBM, the proportion of Fas+ muscle fibres was higher among fibres invaded or contacted by T cells than among fibres not contacted by T cells (P < 0.01). The proportion of Fas+ fibres co-expressing Bcl-2 was 76 +/- 16% in PM, 100% in IBM and 63 +/- 23% in DM. Fas and Bcl-2 expression was also noted in inflammatory cells in PM, IBM, DM and DMD. Using the terminal deoxytransferase-catalysed DNA nick end labelling technique for detection of nuclear DNA fragmentation, none of myonuclei, and < 0.1% of inflammatory cell nuclei, showed signs of apoptosis. Our results suggest that, although Fas expression confers susceptibility to Fas-mediated apoptosis, Fas-expressing muscle fibres and inflammatory cells are protected by the anti-apoptotic protein Bcl-2.

Limited T‐Cell Receptor V Gene Usage in Inclusion Body Myositis

Inclusion body myositis (IBM) is a chronic, progressive inflammatory myopathy. The inflammatory infiltrates are dominated by T cells, which frequently invade muscle fibres. The present study was performed to characterize the usage of the variable (V) segment of the T-cell receptor of muscle infiltrating cells in IBM. Using the reverse transcriptase polymerase chain reaction (RT-PCR) technique the authors analysed the expression of 22 V alpha and 24 V beta families in muscle tissue from six patients with IBM displaying intense inflammatory cell infiltration. The following V alpha/V beta families appeared in at least 50% of the patients: V alpha 1, 5, 7, 15, 16, 17, 20, 21, 22 and V beta 3, 5.2, 8, 12, 14, 22. In all patients V alpha 7, 16 and V beta 8 were expressed in muscle tissue. Furthermore, in two of the patients peripheral blood lymphocytes (PBL) were investigated in parallel. There was a restricted usage of V alpha and V beta families in muscle in comparison to PBL, indicating a selective homing or local proliferation of T lymphocytes in the inflammatory lesions in IBM.