Expression of immunoreactive major histocompatibility complex products in human skeletal muscles

Allografts of muscle precursor cells persist in the non-tolerized host

Implantation of normal muscle precursor cells into myopathic fibres to alleviate recessively inherited diseases of skeletal muscle has received much attention since the discovery of a defective or deficient gene coding for the protein dystrophin in the Duchenne and Becker forms of muscular dystrophy. Therapeutic allografting of cells would require some means of preventing their immune rejection. Here we have allografted muscle into the non-tolerant and non-immunosuppressed murine host. Precursor cells introduced in the form of a single cell suspension survive for prolonged periods post-implantation. Allografts of minced muscle often failed to survive, even though host and donor were compatible at the major histocompatibility locus. Differences at minor loci may well have contributed to such rejection. Where allografted tissue was rejected, there was a decrease in the amount of surviving host muscle at the graft site, an important observation in terms of the therapeutic implantation of cells.

Acute toxoplasma myositis: an immunohistochemical and ultrastructural study

The occurrence is reported of acute myositis in a man with meningoencephalitis due to toxoplasmosis. The ultrastructure and immunohistochemistry of a muscle biopsy of the patient were investigated. Toxoplasma organisms were not found in the muscle biopsy. The perivascular inflammatory cells in the muscle were mainly CD4+ T cells and the inflammatory cells in and around the muscle fibres were chiefly macrophages. Expression of major histocompatibility complex class I and II antigens was observed in the infiltrating cells and endothelial cells of the blood vessels. A small proportion of the infiltrating cells expressed interferon-gamma. A possible role of the immune mechanism in the evolution of myositis is discussed.

Nature of the mononuclear infiltrate and the mechanism of muscle damage in juvenile dermatomyositis and Duchenne muscular dystrophy

Normal skeletal muscle does not express class I MHC antigens. In contrast, these antigens are strongly expressed at the periphery of muscle fibres in patients with juvenile dermatomyositis (JDM) and Duchenne muscular dystrophy (DMD). Interferons can induce the expression of class I antigens, but in this study interferon-gamma could not be detected in JDM muscle biopsy specimens using four different immunocytochemical techniques. However, an infiltrate of mononuclear cells capable of synthesising interferons was present in biopsies from JDM and DMD patients. The predominant cell types detected in both diseases were macrophages and T lymphocytes, these two cell types comprising more than 80% of the infiltrating mononuclear cells. A striking predominance of CD4+ helper/inducer T cells was observed. The majority of these cells expressed class II MHC antigens and were, therefore, considered to be activated. Additional evidence for the functional activity of CD4+ T cells was derived from the finding that it was this population of cells from JDM biopsies which proliferated in response to interleukin-2 in vitro. T cell subsets in peripheral blood were also investigated in JDM and DMD patients. Only in the case of JDM were any significant differences from normal observed, where a significant reduction in the number of peripheral blood CD8+ T cells resulted in an elevation of CD4+/CD/8+ ratios. The role of CD4+ T cells and aberrant class I MHC antigen expression in mediating muscle damage in JDM and DMD is discussed.

Major histocompatibility complex antigen expression in the affected tissues in amyotrophic lateral sclerosis

Monoclonal antibody immunocytochemistry was used to examine spinal cord and muscle in amyotrophic lateral sclerosis for changes that would indicate ongoing or potential immune activity. Increased expression of class I and II major histocompatibility complex (MHC) antigens was seen in the affected areas of spinal cord. New MHC expression was concentrated in phagocytes, particularly in degenerating white matter in which they were dispersed in the tissue and also packed around blood vessels. MHC antigen was not revealed in motor neurons or skeletal muscle fibers. An anti-pan-T-cell monoclonal revealed small numbers of T cells in degenerating white matter. Similar changes have been seen in other neurodegenerative disorders. They suggest a potential for (secondary) cell-mediated activity in the affected areas rather than an ongoing MHC-restricted T-cell response. Vessel-associated phagocytes may be a source of antigen to peripheral lymphoid tissue, stimulating production of the autoantibodies that have been described.

Elevated MHC class I and II antigens in cultured human embryonic myoblasts following stimulation with gamma-interferon

The expression of major histocompatibility complex (MHC) antigens on the surface of cultured human embryonic myoblasts was studied by fluorescence microscopy. Class I or II MHC antigens were detected by monoclonal antibodies (MoAb) recognizing monomorphic determinants on HLA-A, B and C (class I), or HLA-DP, DQ and DR (class II) and a secondary fluorescein-labelled sheep anti-mouse immunoglobulin (Ig) antibody. Myoblasts were simultaneously identified using a MoAb directed against myosin light chains 1 and 2 (MLC1 and MLC2) and a combination of biotin-labelled sheep anti-mouse Ig antibody and Texas Red labelled streptavidin. We found that myoblasts demonstrated only very weak expression of either class of MHC but that, in the presence of more than 100 units of gamma-interferon (gamma-IFN) for 56-72 h, both class I and II MHC antigen expression increased significantly. During this time, class I antigen increased more than class II and at lower gamma-IFN concentrations. The implications of these findings for myoblast transfer therapy in Duchenne muscular dystrophy patients is discussed.

Lysis of myotubes by alloreactive cytotoxic T cells and natural killer cells. Relevance to myoblast transplantation

The aim of this study was to investigate the susceptibility of human myotubes to lysis by the two major types of cytotoxic effector cells, CD3+CD8+ cytotoxic T cells (CTL) and CD16+CD56+ natural killer (NK) cells. The myoblasts preparations used as target cells were greater than 90% pure as assessed by immunostaining with the Leu19 monoclonal antibody (MAb) that cross-reacts with the neural cell adhesion molecule N-CAM. Allospecific CTL lines were generated from mixed lymphocyte cultures, and freshly isolated allogeneic and autologous peripheral blood cells were used as a source of NK cells. The cytotoxicity was observed under phase optics and by immunoelectron microscopy, and was quantitated with a chromium release assay. Myotubes were efficiently killed by allospecific CTL and by autologous and allogeneic NK cells. The killing by CTL was inhibited with an anti-class I HLA MAb, and the killing by NK cells was inhibited by depleting peripheral blood cells of CD16+ cells with anti-CD16 MAb and complement. The results have important implications for myoblast transplantation, an experimental therapy of muscular dystrophy.

Mitochondrial myopathy caused by long-term zidovudine therapy

Both infection with the human immunodeficiency virus type 1 (HIV) and zidovudine (formerly called azidothymidine [AZT]) cause myopathy. To identify criteria for distinguishing zidovudine-induced myopathy from that caused by primary HIV infection, we reviewed the histochemical, immunocytochemical, and electron-microscopical features of muscle-biopsy specimens from 20 HIV-positive patients with myopathy (15 of whom had been treated with zidovudine) and compared the findings with the patients' clinical course and response to various therapies. Among the zidovudine-treated patients, the myopathy responded to prednisone in four, to the discontinuation of zidovudine in eight, and to nonsteroidal anti-inflammatory drugs in two. Numerous "ragged-red" fibers, indicative of abnormal mitochondria with paracrystalline inclusions, were found in the biopsy specimens from the zidovudine-treated patients but not in those from the other patients. The number of these fibers appeared to correlate with the severity of the myopathy. All the patients, regardless of whether they had been treated with zidovudine, had inflammatory myopathy characterized by degenerating fibers, cytoplasmic bodies, and endomysial infiltrates consisting of CD8+ cells (mean +/- SD, 60.7 +/- 6.4 percent) and macrophages (39.2 +/- 6.4 percent) associated with Class I major histocompatibility complex (MHC-I) antigens (HLA-A, -B, and -C antigens) in the muscle fibers. The numbers and percentages of CD8+ cells and macrophages were similar in both the zidovudine-treated and the untreated HIV-positive patients. Specimens obtained on repeat muscle biopsy from two patients in whom the myopathy responded to the discontinuation of zidovudine showed remarkable histologic improvement. We conclude that long-term therapy with zidovudine can cause a toxic mitochondrial myopathy, which coexists with a T-cell-mediated inflammatory myopathy that is restricted to MHC-I antigen, and is indistinguishable from the myopathy associated with primary HIV infection or polymyositis in HIV-seronegative patients.

Inflammatory and non-inflammatory inclusion body myositis. Characterization of the mononuclear cells and expression of the immunoreactive class I major histocompatibility complex product

In ten patients with inclusion body myositis (IBM) five muscular biopsies showed profuse inflammatory exudates and three showed a few scattered inflammatory cells with partial invasion in some muscle fibers. No inflammatory cells were seen in two cases. In all patients, histopathological, histomorphometric and immunocytochemical studies were performed. Immunocytochemistry for the class I and class II major histocompatibility complex gene product (MHC) was performed in all cases and in ten control muscles including: normal muscles [3], dermatomyositis [3], polymyositis [3], scleroderma [1]. In the five cases of IBM with inflammatory exudates, subsets of lymphocytes were analyzed with a panel of monoclonal antibodies against B cells, T4 cells, T8 cells, K and natural killer cells and macrophages. Some muscle fibers expressed class I MHC antigens in the inflammatory cases of IBM. These fibers were near the inflammatory exudates and occasionally showed a partial invasion. No expression of class I MHC was found in normal muscles and in non-inflammatory cases of IBM. The antigen which triggers the mononuclear cells in the inflammatory forms of IBM is probably not the filamentous inclusions in rimmed vacuoles. In other inflammatory myopathies, expression of class I MHC was present on all fibers in polymyositis, only in the perifascicular area in dermatomyositis and in scleroderma. It could be suggested that the term "inclusion body muscle disease" be applied to cases with rimmed vacuoles and "IBM-like" filaments without inflammatory cells.

Expression of major histocompatibility complex class I antigens in rat muscle cultures: the possible developmental role in myogenesis

The expression of major histocompatibility complex class I antigens was demonstrated on aneurally cultured rat muscle cells. Myoblasts showed constitutive expression of class I antigens on their cell surfaces. The presence of the antigens was transitory, disappearing as myoblasts fused and differentiated into multinucleate myotubes. Furthermore, antibody against rat class I antigens showed an inhibitory effect on the generation of myotubes during muscle development. Although mature myotubes did not show any detectable levels of class I antigens on their cell surface, soluble factors from concanavalin A-activated spleen cells or interferon gamma could induce the expression of class I antigens on muscle fibers. These results suggest that the expression of class I antigens on muscle cells is not only immunologically modulated but also developmentally regulated and that the antigens may play a role in cell recognition and interactions during the fusion process of myogenesis.

Major histocompatibility complex class I antigen expression, immunolocalization of interferon subtypes, and T cell-mediated cytotoxicity in myopathies

Major histocompatibility complex class I (MHC-I) expression on target cells is a prerequisite for antigen-specific T cell-mediated cytotoxicity (TCMC). Enhanced MHC-I expression has been attributed to interferons (IFNs) released from inflammatory cells. In previous studies, we found evidence of TCMC (invasion of non-necrotic muscle fibers by cytotoxic T cells) in polymyositis (PM) and in inclusion body myositis (IBM). We occasionally found evidence of TCMC in Duchenne dystrophy (DD) but not in dermatomyositis (DM). This study examines the relationships between TCMC, MHC-I expression, and IFN immunoreactivity in these diseases and normal controls. In controls, reactivity for MHC-I was confined to blood vessels. In all diseases, regenerating fibers expressed MHC-I. In IBM, PM and DD, all nonnecrotic muscle fibers invaded by CD8+ cells and some adjacent fibers expressed MHC-I. In DM, myriad muscle fibers expressed MHC-I but none were invaded by CD8+ cells. In all diseases, only a few mononuclear cells and no muscle fiber surfaces were immunoreactive for IFNs. We conclude that MHC-I expression on muscle fibers is necessary but not sufficient for TCMC in myopathy; that the biological significance of increased MHC-I expression in DM remains undefined; and that currently available and appropriately controlled immunocytochemical methods show no relationship between increased MHC-I expression on muscle fibers and local IFN synthesis by mononuclear cells.

Expression of class I and class II MHC antigens in neuromuscular diseases

The distribution of HLA class I and class II antigens has been investigated in cryostat sections of a series of 200 skeletal muscle biopsy specimens from patients with various neuromuscular disorders. Normal muscle fibres expressed no detectable class I antigens, whereas muscle fibres of patients with inflammatory myopathies and Duchenne (DMD) and Becker (BMD) muscular dystrophy showed consistently strong expression. In other neuromuscular diseases expression of class I antigens was more variable. No expression of class I antigens was observed on muscle fibres in samples from fetuses "at risk" for DMD and BMD or from female carriers of these disorders. The immunocytochemical assessment of HLA class I antigen expression was confirmed by a quantitative radioimmunoassay which demonstrated a 3-fold increase in the level of expression in muscle samples from patients with DMD and juvenile dermatomyositis. Class II antigen expression was never observed on muscle fibres in biopsies from normal individuals or any of the neuromuscular disorders. However, these antigens were expressed by endothelial cells present in these samples. Muscle specimens from fetuses and early in postnatal life showed very limited expression of class II antigens. They were expressed at a reduced level by about 3 months of age, but strong expression of class II antigens was not observed until about 1 year of age. The mechanism of induction of class I antigen expression in diseased muscle is not known. The appearance of class I antigens on diseased muscle may make the affected tissue a target for cytotoxic T cells and may thus have a role in muscle fibre damage in inflammatory myopathies and the X-linked muscular dystrophies.