Disease-associated increased HIF-1, αvβ3 integrin,and Flt-1 do not suffice to compensate the damage-inducing loss of blood vessels in inflammatory myopathies

Objective To analyze the microvascular network in skeletal muscle biopsies from patients with dermatomyositis (DM) and systemic sclerosis (SSc) compared to polymyositis (PM) and systemic lupus erythematosus (SLE), and non-inflammatory myopathies, and to clarify whether reparative angiogenesis-related factors are expressed in parallel to blood vessel damage.Methods Immunohistochemical staining of muscle biopsies (10 DM, 10 SSc, 10 PM, 10 SLE, and 10 non-inflammatory myopathies) with antibodies against von Willebrand factor (vWF), hypoxia-inducible factor-1 (HIF-1), 3 integrin subunit, and vascular endothelial growth factor receptor-1 (VEGFR-1). The TechMate staining robot and biotin-streptavidin protocol were used.Results DM and SSc muscles were characterized by endothelial damage and reduction of blood vessel network. Expression of angiogenesis-related factors (HIF-1, 3, VEGFR-1) was also found in the same biopsies. In contrast, in PM and SLE muscles, vascular networks were apparently not affected and angiogenic stimuli were less expressed if at all.Conclusions This work demonstrates that in inflamed muscles hypoxia/ischemia induces increased expression of angiogenic factors, yet their impact is insufficient to repair disease-associated reduction of the capillary network. This leads to questions considering the usefulness of angiogenic factors in the treatment of ischemic inflammatory myopathies in DM and SSc.     

Tumor necrosis factor-alpha in inflammatory myopathies: pathophysiology and therapeutic implications

OBJECTIVES: To present, in an organized fashion, data from the medical literature on the possible role of tumor necrosis factor (TNF)-alpha in the pathogenesis of dermatomyositis (DM) and polymyositis (PM), as well as recent clinical studies where TNF-inhibition was used as a treatment for myositis. METHODS: PUBMED was searched from 1966 to the present using the terms: TNF-alpha, TNF-inhibitors, dermatomyositis, polymyositis, myositis, and inflammatory myopathy. In addition, relevant abstracts from major recent rheumatology meetings were retrieved. RESULTS: Several studies that employed immunostaining and polymerase chain reaction analysis in muscle biopsy specimens from patients with inflammatory myopathies showed increased presence of TNF-alpha and its soluble receptors in inflamed muscle. One genetic study proposed an association between DM and the -308A TNF polymorphism. Abnormally high levels of TNF-alpha in the muscle may be directly toxic to myofibers, while preventing muscle regeneration. Furthermore, TNF-alpha may induce, or augment, the production of other pro-inflammatory cytokines such as interleukin (IL)-1, monocyte chemotactic protein-1, IL-6, and IL-8. These findings have prompted some investigators to use off-label, TNF-inhibitors in DM/PM patients, especially if they had failed corticosteroids, immune gamma-globulin, and traditional immunosuppressive agents. The results from these early, uncontrolled, studies have been promising. CONCLUSION: TNF-alpha may have a role in the pathogenesis of the myositis and has emerged as a possible therapeutic target. Larger, carefully controlled studies are needed to confirm the results from early studies and clearly define the efficacy and safety of anti-TNF agents in the treatment of inflammatory myopathies.     

Pathogenesis of the idiopathic inflammatory myopathies

The inflammatory myopathies, commonly described as idiopathic, are a group of acquired diseases characterized by an inflammatory infiltrate of the skeletal muscle. On the basis of clinical and immuno-pathological features, three major diseases can be identified: dermatomiositis (DM), polymyositis (PM) and inclusion body myositis (IBM). Immunopathogenesis mechanisms are crucial for discriminating between the three different subsets of inflammatory myopathies. DM is a complement-mediated microangiopathy affecting skin and muscle. PM and IBM are T cell-mediated disorders, where CD8-positive cytotoxic T cells invade muscle fibres expressing MHC class I antigens. This article summarizes the main immunopathological markers. The impact of this new knowledge must be defined in relation to potential therapeutic targets for idiopathic inflammatory myopathies.     

Limited effects of high-dose intravenous immunoglobulin (IVIG) treatment on molecular expression in muscle tissue of patients with inflammatory myopathies

OBJECTIVES: The study was conducted with the aim of achieving an improved understanding of the molecular mechanisms of high-dose intravenous immunoglobulin (IVIG) in inflammatory myopathies by investigating the effects on muscle function and immunological molecules in skeletal muscle of polymyositis (PM), dermatomyositis (DM) and inclusion body myositis (IBM) patients. METHODS: Thirteen treatment-resistant patients, 6 PM, 4 DM, 2 IBM and 1 juvenile DM, were treated with 2 g/kg of IVIG, three times at monthly intervals. Functional Index in Myositis and serum creatinine kinase (CK) levels were determined, and muscle biopsies were performed before treatment and after the third IVIG infusion. Immunological molecules were also studied in biopsies taken 24-48 h after the first infusion. RESULTS: Improved muscle function was observed in three patients (1 PM, 1 DM and 1 IBM) and CK levels decreased in five. T cells, macrophages, major histocompatibility complex (MHC) class I antigen on muscle fibres, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression and membranolytic attack complex (MAC) deposits on capillaries were present to an equal degree in biopsies before and after IVIG treatment. No correlation between the clinical response and molecular changes was found. CONCLUSIONS: The clinical effects of high-dose IVIG on muscle function in patients with refractory inflammatory active myositis did not correspond to effects on any of the investigated molecules in our study. T cells, macrophages, phenotypical changes in muscle fibres and endothelial cell activation were still present after treatment. These observations question a role for IVIG as an immune-modulating therapy in patients with inflammatory myopathies.     

Polymyositis, dermatomyositis, and autoimmune necrotizing myopathy: clinical features

Idiopathic inflammatory myopathies are a heterogeneous group of autoimmune disorders predominantly affecting skeletal muscles, resulting in muscle inflammation and weakness. The 3 most common inflammatory myopathies are polymyositis (PM), dermatomyositis (DM), and inclusion body myositis. This review details the clinical findings noted in PM, DM, and the emerging entity of autoimmune necrotizing myopathy.     

Increased expression of interleukin 1alpha and MHC class I in muscle tissue of patients with chronic, inactive polymyositis and dermatomyositis

OBJECTIVE: To investigate if there is a molecular correlate in muscle tissue to the persisting decreased muscle function in patients with chronic, inactive polymyositis (PM) and dermatomyositis (DM). METHODS: Muscle function was assessed using a muscle function index of myositis. To assess disease activity both histopathological investigation of muscle biopsies and magnetic resonance imaging (MRI) scans of the thigh muscles were performed. Inactive chronic disease was defined as persisting muscle weakness and absence of inflammatory infiltrates in muscle biopsy and absence of signs of inflammation on MRI. Expression of interleukin 1alpha (IL-1alpha), IL-1beta,, adhesion molecules, and MHC class I molecules in muscle tissue was investigated with immunohistochemistry. RESULTS: Muscle weakness was confirmed by a reduction of muscle function score. No signs of inflammation typical for myositis were observed. The most striking finding in our study was the strong expression of IL-1alpha and MHC class I molecules in muscle tissue from patients with inactive chronic PM and DM. Increased IL-1alpha expression was evident in capillaries and increased MHC class I expression was detected in muscle fiber membranes. CONCLUSION: IL-1alpha and MHC class I molecules may have an importance in the pathogenesis of the chronic muscle weakness and fatigue in patients with PM and DM.     

Nation-wide survey for the treatment with cyclosporin A of interstitial pneumonia associated with collagen diseases]

OBJECTIVES: This study was performed to investigate the efficacy and safety of cyclosporin A (CsA) for the treatment of interstitial pneumonia (IP) associated with collagen diseases in Japan. METHODS: Questionnaires were sent to 36 hospitals specializing in collagen diseases. RESULTS: Fifty-eight patients (7 polymyositis (PM), 19 dermatomyositis (DM), 7 systemic sclerosis (SSc), 7 rheumatoid arthritis (RA), 2 mixed connective tissue disease (MCTD), 1 systemic lupus erythematosus (SLE) and 1 Sj?gren's syndrome (SS), 1 RA + SSc, 2 PM + SSc, 1 DM + SLE, and 10 idiopathic interstitial pneumonia (IIP) with IP were treated with CsA at 14 hospitals. IP was classified into the acute or chronic type. In the PM/DM group (7 PM, 19 DM, 2 PM + SSC, 1 DM + SLE), 65.5% were the acute type. In the other collagen disease group (7 SSc, 7 RA, 2 MCTD, 1 SLE, 1 SS, and 1 RA + SSc) and IIP group, 36.8% and 50% were the acute type, respectively. Mean dosages of CsA were 3.7 +/- 1.3 mg/kg/day for the PM/DM group, 3.0 +/- 1.0 for the other collagen disease group, and 3.8 +/- 4.8 for the IIP group. Oral corticosteroids were administered in combination with CsA in 100, 73.7, and 70% of the patients with PM/DM, other collagen disease, and IIP groups, respectively. CsA was effective for 72.2, 33.3, and 25% of the acute IP cases in the PM/DM, other collagen disease, and IIP groups, respectively. CsA was effective for 50.0, 50.0, and 60.0% of chronic IP cases in the PM/DM, other collagen disease, and IIP groups, respectively. Twenty-three adverse effects were observed, but most of them ameliorated upon withdrawal or reduction of the CsA dose. CONCLUSION: CsA is effective for the treatment of acute type IP associated with collagen diseases, especially PM/DM. To perform a prospective multi-center trial, standards for the recruitment of patients, efficacy assessments, and trial course and treatment should be determined carefully.     

Cytokine production in muscle tissue of patients with idiopathic inflammatory myopathies

Objective. To study cytokine expression in muscle tissues of patients with inflammatory myopathies and to compare the profiles of patients with polymyositis (PM), inclusion body myositis (IBM), and dermatomyositis (DM). Methods. We performed indirect immunohistochemistry studies of muscle tissue sections with a panel of 16 different cytokine-specific monoclonal antibodies, directed against interleukin-1α, (IL-1α), IL-1β, IL-1 receptor antagonist (IL-1ra), IL-2, IL-3, IL-4, IL-6, IL-8, IL-10, IL-13, interferon-γ (IFNγ), tumor necrosis factor α (TNFα), granulocyte-macrophage colonystimulating factor (GM-CSF), transforming growth factor β1 (TGFß1), TGFß2, and TGFß3 in 5 untreated patients each with PM, DM, and IBM and in 4 normal controls. Fresh frozen muscle tissue sections were fixed in formaldehyde before the procedure. The use of saponin as a detergent to permeabilize the cell membranes enabled identification of intracellular cytokine production. Results. The most prominent finding was the expression of IL-1α observed in all patients but in none of the normal controls. In all patients with PM, DM, and IBM, IL-1α was expressed in endothelial cells of capillaries, arterioles, and venules in areas surrounded by inflammatory cells, and also in areas with no or scarce inflammatory cells in both endomysium and perimysium. Furthermore, IL-1α was also expressed in mononuclear inflammatory cells in all 15 cases. IL-1β was observed in inflammatory cells in 10 of the 15 patients but, in contrast to IL-1α, it was not expressed in blood vessel walls. TGFß1, TGFß2, and TGFß3 were strongly positive in all 15 patients, but only scattered cells were positive in the normal controls. The remaining cytokines were observed only in relatively few cells and only in occasional patients (although the patients were selected for the presence of large infiltrates), and in none of the controls. The patterns were similar in PM, DM, and IBM. Conclusion. Cytokine expression in muscle tissue of patients with inflammatory myopathy is dominated by IL-1α, IL-1β, and TGFß1–3. The predominant IL-1α expression in the blood vessels indicates an importance of the endothelial cells in the inflammatory process in PM, IBM, and DM. A sustained, local release of T cell-derived cytokines may not be a requirement for tissue injury in the inflammatory myopathies. There does not appear to be a qualitative difference in cytokine expression patterns in PM, IBM, and DM.     

Decreased expression of interleukin-1alpha, interleukin-1beta, and cell adhesion molecules in muscle tissue following corticosteroid treatment in patients with polymyositis and dermatomyositis

OBJECTIVE: To study the effects of immunosuppressive therapy, in particular, corticosteroids, on morphologic signs of inflammation and expression of cytokines, adhesion molecules, and class I major histocompatibility complex (MHC) antigen in muscle tissue from patients with polymyositis (PM) and dermatomyositis (DM) and to correlate the molecular changes with changes in muscle function. METHODS: Seven patients with PM and 4 patients with DM underwent muscle biopsy before and after 3-6 months of therapy. Ten of the 11 patients were initially treated with prednisolone 30-60 mg/day. The phenotypes of infiltrating inflammatory cells and the expression of interleukin-1alpha (IL-1alpha) and IL-1beta, adhesion molecules, and class I MHC antigen were studied by immunochemistry. Computerized image analysis was used for quantitation of staining. Muscle function was assessed with a muscle function index score. RESULTS: Pronounced improvement of muscle function during the treatment period was noted in 8 of the 11 patients. The changes in muscle function coincided with an almost complete disappearance of inflammatory cells, including CD3+ T cells, in the patients with clinical improvement. These patients also exhibited decreased expression of IL-1alpha, IL-1beta, intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), leukocyte function-associated antigen 1alpha, and very late activation antigen 4alpha. Of note, there was persistent expression of IL-1alpha, ICAM-1, and VCAM-1 in capillaries and of class I MHC antigens on muscle fibers in several of the patients who, after corticosteroid treatment, still had muscle weakness despite the disappearance of inflammatory infiltrates. CONCLUSION: Changes in the muscle expression of key molecules in the inflammatory process, such as IL-1alpha and IL-1beta, ICAM-1 and class I MHC antigens, showed a consistent but not complete concordance with changes in and status of muscle function in patients with myositis who received the current standard treatment for the disease. These data indicate that it is possible to further evaluate various therapies for myositis using molecular analysis of muscle biopsy specimens obtained on repeated occasions. In addition, the data demonstrate a dissociation between muscle function and degree of inflammatory infiltration in the affected muscles and suggest that the functional defects are more related to the expression of molecules such as IL-1alpha in muscle capillaries than to the mere presence of inflammatory cells in the affected muscles.     

Large macrophage colony-forming cells identical to high proliferative potential colony-forming cells in peripheral blood of patients with collagen vascular diseases: high occurrence among patients with systemic sclerosis and dermatomyositis

OBJECTIVE: To examine peripheral blood (PB) of patients with various collagen vascular diseases (CVD) for the presence of colony-forming cells (CFC) that form large macrophage colonies (> 2.5 mm in diameter, > 10,000 cells). METHODS: Peripheral blood mononuclear cells were obtained from 92 patients with various active CVD and 20 healthy controls, and assayed for in vitro colony formation. There were 14 patients with systemic lupus erythematosus (SLE), 30 with rheumatoid arthritis (RA), 17 with systemic sclerosis (SSc), 20 with polymyositis (PM)/dermatomyositis (DM) (11 PM, 9 DM) and 11 with systemic vasculitis. RESULTS: Large macrophage CFC were detected in PB of 7% of patients with SLE (1/14), 17% with RA (5/30), 47% with SSc (8/17), 30% with PM/DM (6/20) [9% PM (1/11) and 56% DM (5/9)], 0% of those with systemic vasculitis (0/11) and 0% of the healthy subjects (0/20). There was a significant difference between the occurrence of CFC in patients with PM versus patients with DM (p < 0.05). The occurrence of CFC in patients with SSc or DM was significantly higher than that in patients with other CVD including SLE, RA, PM, and systemic vasculitis (p < 0.05). CONCLUSION: Based on the size of the colonies they formed, the CFC corresponded to high proliferative potential colony-forming cells, a subset of primitive hematopoietic cells. Our findings among patients with CVD indicate that these primitive hematopoietic progenitor cells, which are believed to constitute a noncirculating population in healthy individuals, are found most frequently in PB of patients with SSc and DM. It is likely that primitive hematopoietic cells are frequently mobilized into the peripheral circulation during the pathogenesis of SSc and DM.     

Clinical and laboratory features of overlap syndromes of idiopathic inflammatory myopathies associated with systemic lupus erythematosus,systemic sclerosis,or rheumatoid arthritis

Because overlap syndromes (OSs) are rarely described, we analyzed retrospectively their frequencies and correlations in Brazilian series of 31 patients with dermatomyositis (DM)/polymyositis (PM) associated with systemic lupus erythematosus (SLE), systemic sclerosis (SSc), or rheumatoid arthritis (RA) attended at a referral single center. Myositis-specific autoantibodies (MSAs: anti-Jo-1, anti-PL-7, anti-PL-12, anti-EJ, anti-OJ, anti-SRP, anti-Mi-2) and myositis-associated autoantibodies (MAAs: anti-PM-Scl75, anti-PM-Scl100, anti-Ku) as well as specific autoantibodies related to SLE, SSc, and RA were investigated. The mean age of the OS patients (9 DM and 22 PM) was 44.6?±?15.4 years, with a predominance of women (83.9 %) and white ethnicity (58.1 %). PM was the most frequent inflammatory myopathy, and the clinical presentation of DM/PM was significantly different among the OS groups. Overlap was found with SSc (48.4 %), SLE (29.0 %), and RA (22.6 %). The clinical manifestations of DM/PM were identified simultaneously with SSc and RA in the majority of cases, in contrast to identification in the SLE group (p?<?0.05). All patients were positive for antinuclear antibodies, and the prevalence of MSA and MAA was 38.8 % in all OS groups, mutually exclusive, and more frequent in the SSc group. Comparing the clinical and laboratory features, there was a higher frequency of vascular (skin ulcers, Raynaud’s phenomenon) and pulmonary (interstitial lung disease) involvement in the SSc group (p?<?0.05). Moreover, there were no differences among the groups in relation to disease relapse and deaths. Concluding, this is the first study to show the different characteristics of a series of patients with connective tissue disease (CTD)-OS in the heterogeneous Brazilian population.     

Autoantibodies in Polymyositis and Dermatomyositis

Inflammatory myopathies are a group of acquired diseases, characterized by immunoflogistic processes primarily involving the skeletal muscle. According to recent classification criteria, four major diseases have been identified: polymyositis (PM), dermatomyositis (DM), sporadic inclusion body myositis (IBM), and necrotizing autoimmune myositis (NAM). Autoantibodies can be found in the sera of most patients with myositis. Myositis-specific autoantibodies (MSAs) are markers of very specific disease entities within the spectrum of myositis, and target proteins involved in key processes of protein synthesis. Myositis autoantigens comprise the well-defined aminoacyl-tRNA synthetases, the Mi-2 helicase/histone deacetylase protein complex, and the signal recognition particle (SRP) ribonucleoprotein, together with novel targets such as TIF1-γ, MDA5, NXP2, SAE, and HMGCR. Recent studies suggest that autoantigens drive a B cell antigen-specific immune response in muscles. Interestingly, an increased expression of Jo-1 and Mi-2 in regenerating fibers in muscle biopsies from PM and DM patients compared to normal was demonstrated. Myositis autoantigen up-regulation was observed in neoplastic tissues, thus representing a potential link between cancer and autoimmunity in myositis. Non-immunological mechanisms seem to participate to the pathogenesis of inflammatory myopathies; induction of endoplasmic reticulum stress response in response to abnormal muscle regeneration and inflammation has recently been reported in patients with myositis. This review article provides an update of new emerging insights about the clinical and pathophysiologic role of principal autoantibodies in myositis.     

Serum concentrations of the CXC chemokines interleukin 8 and growth-regulated oncogene-alpha are elevated in patients with systemic sclerosis

OBJECTIVE: To determine whether serum concentrations of 2 CXC chemokines, interleukin 8 (IL-8) and growth-regulated oncogene-alpha (GRO-alpha), which are potent chemoattractants and activators for neutrophils, are elevated and whether they correlate with clinical features in patients with systemic sclerosis (SSc). METHODS: Serum samples from patients with diffuse cutaneous SSc (dSSc; n = 36), limited cutaneous SSc (lSSc; n = 42), systemic lupus erythematosus (SLE; n = 15), dermatomyositis (DM; n = 15), and healthy controls (n = 35) were examined by ELISA. RESULTS: Serum IL-8 was detected significantly more frequently in patients with dSSc (61%) and lSSc (55%) relative to healthy controls (6%), patients with SLE (7%), and those with DM (13%). Similarly, serum GRO-alpha concentrations in SSc patients were significantly increased compared with controls, patients with SLE, or those with DM. Elevated IL-8 concentrations significantly correlated with decreased % DLCO and rheumatoid factor positivity, while increased GRO-alpha levels were significantly associated with decreased % DLCO and % vital capacity, involvement of kidney and muscle, the presence of anti-topoisomerase I antibody, and increased serum IgG levels. CONCLUSION: Our results suggest that the elevation of serum levels of the CXC chemokines IL-8 and GRO-alpha is specific to SSc and that the elevation of CXC chemokines, particularly GRO-alpha, correlates with the involvement of internal organs, especially pulmonary damage.     

MyoD expression restores defective myogenic differentiation of human mesoangioblasts from inclusion-body myositis muscle

Inflammatory myopathies (IM) are acquired diseases of skeletal muscle comprising dermatomyositis (DM), polymyositis (PM), and inclusion-body myositis (IBM). Immunosuppressive therapies, usually beneficial for DM and PM, are poorly effective in IBM. We report the isolation and characterization of mesoangioblasts, vessel-associated stem cells, from diagnostic muscle biopsies of IM. The number of cells isolated, proliferation rate and lifespan, markers expression, and ability to differentiate into smooth muscle do not differ among normal and IM mesoangioblasts. At variance with normal, DM and PM mesoangioblasts, cells isolated from IBM, fail to differentiate into skeletal myotubes. These data correlate with lack in connective tissue of IBM muscle of alkaline phosphatase (ALP)-positive cells, conversely dramatically increased in PM and DM. A myogenic inhibitory basic helix-loop-helix factor B3 is highly expressed in IBM mesoangioblasts. Indeed, silencing this gene or overexpressing MyoD rescues the myogenic defect of IBM mesoangioblasts, opening novel cell-based therapeutic strategies for this crippling disorder.     

Decreased CD161+CD8+ T cells in the peripheral blood of patients suffering from rheumatic diseases

OBJECTIVES: Although it has been reported that the numbers of both CD4(-)CD8(-) and CD4(+) natural killer T (NKT) cells are selectively decreased in the peripheral blood of patients with rheumatic diseases, there have been no reports concerning a novel subpopulation of CD8(+) NKT cells. To examine whether CD161(+)CD8(+) T cells, which are closely related to CD8(+) NKT cells, are also decreased in patients with rheumatic diseases, we have investigated the expression of CD161, together with that of CD28, CD25 and CD62L, on T cells in the peripheral blood of these patients. METHODS: The rheumatic diseases evaluated in this study were systemic lupus erythematosus (SLE) (n= 54), mixed connective-tissue disease (MCTD) (n= 15), systemic sclerosis (SSc) (n= 14), polymyositis/dermatomyositis (PM/DM) (n= 13) and rheumatoid arthritis (RA) (n= 24). Healthy donors were examined as controls (n= 18). The expression of CD161, CD28, CD25 and CD62L on T cells was analysed by flow cytometry. RESULTS: Both the frequency of CD161 expression on CD8(+) cells and the absolute number of CD161(+)CD8(+) cells were significantly decreased in patients with SLE, MCTD, SSc and PM/DM. Only the absolute number of CD161(+)CD8(+) T cells was significantly decreased in RA. CD161 expression on CD28(-)CD8(+) T cells was significantly decreased in SLE, MCTD and SSc. The absolute number of CD161(+)CD8(+)CD62L(-) T cells was significantly decreased in SLE, MCTD and SSc. CONCLUSIONS: Both the frequency and the absolute number of CD161(+)CD8(+) T cells were decreased in the peripheral blood of patients suffering from SLE, MCTD, SSc and PM/DM. This result suggests that there is also an abnormality of NKT cells in the CD8(+) population.     

Muscle biopsy findings in inflammatory myopathies

The inflammatory myopathies encompass a heterogeneous group of acquired muscle diseases characterized clinically, by muscle weakness, and histologically, by inflammatory infiltrates within the skeletal muscles. The group of these myopathies comprise three major and discrete subsets: polymyositis (PM), dermatomyositis (DM), and inclusion body myositis (IBM). Each subset retains its characteristic clinical, immunopathologic, and morphologic features regardless of whether it occurs separately or in connection with other systemic diseases. Although the diagnosis of these disorders is based on the combination of clinical examination, electromyographic data, serum muscle enzyme levels, various autoantibodies, and the muscle biopsy findings, the muscle biopsy offers the most definitive diagnostic information in the majority of the cases. This article summarizes the main histologic features that characterize PM, DM, or IBM and emphasizes the main pitfalls associated with interpretation of the biopsies.     

Proliferative response of peripheral blood mononuclear cells to autologous and allogeneic muscle in patients with polymyositis/dermatomyositis

We examined the proliferative responses of peripheral blood mononuclear cells (PBMC) to autologous and homologous muscle homogenates in 21 patients with early, active, untreated polymyositis/dermatomyositis (PM/DM), 8 patients with chronic PM/DM, 10 patients with myopathies other than PM/DM, 7 patients with connective tissue diseases without myositis, and 12 healthy individuals. PBMC from patients with PM/DM and from control subjects were incubated with various dilutions of autologous and homologous muscle homogenates. PBMC from patients with active PM/DM underwent significant proliferation on exposure to both the autologous muscle and the homologous muscle homogenates. In contrast, PBMC from patients with chronic PM/DM, other myopathies, connective tissue diseases without myositis, and from healthy individuals did not respond to either autologous or homologous muscle. Our findings demonstrate that the PBMC of patients with PM/DM are sensitized to muscle.