Clinical, serologic, and immunogenetic features of familial idiopathic inflammatory myopathy.

OBJECTIVE: To describe the clinical, serologic, and immunogenetic features of familial idiopathic inflammatory myopathy (IIM) and to compare these with the features of sporadic IIM. METHODS: Clinical signs and symptoms, autoantibodies, HLA-DRB1 and DQA1 alleles, and GM/KM phenotypes were compared among 36 affected and 28 unaffected members of 16 unrelated families in which 2 or more blood relatives developed an IIM. In addition, findings in patients with familial IIM were compared with those in 181 patients with sporadic IIM. The families included 3 pairs of monozygotic twins with juvenile dermatomyositis, 11 families with other siblings or relatives with polymyositis or dermatomyositis, and 2 families with inclusion body myositis. RESULTS: The clinical features of familial IIM were similar to those of sporadic IIM, although the frequency of myositis-specific autoantibodies was lower in familial than in sporadic IIM. DRB1*0301 was a common genetic risk factor for familial and sporadic IIM, but contributed less to the genetic risk of familial IIM (etiologic fraction 0.35 versus 0.51 in sporadic IIM). Homozygosity at the HLA-DQA1 locus was found to be a genetic risk factor unique to familial IIM (57% versus 24% of controls; odds ratio 4.2, corrected P = 0.002). CONCLUSION: These findings emphasize that 1) familial muscle weakness is not always due to inherited metabolic defects or dystrophies, but may be the result of the development of IIM in several members of the same family, and 2) multiple genetic factors are likely important in the etiology and disease expression of familial IIM, as is also the case for sporadic myositis, but DQA1 homozygosity is a distinct risk factor for familial IIM.

Synergistic cytotoxic effect of interferon-gamma and tumor necrosis factor-alpha on cultured human muscle cells.

OBJECTIVE: To investigate the effects of human interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha), either alone or in combination, on the viability of human muscle cells in culture. METHODS: Cultures of human muscle cells were treated with various concentrations of recombinant IFN-gamma and TNF-alpha alone and in combination, and the cytotoxic effects of the cytokines on muscle cells were assessed by measuring lactic dehydrogenase (LDH) release in supernatants and by observation of the cells for morphologic changes under phase microscopy. RESULTS: Exposure of muscle cells to 100 U/ml of either IFN-gamma or TNF-alpha for 9 days caused no cytotoxic effects, as assessed by LDH release in supernatants of muscle cell cultures and by microscopic observation of the cell cultures. However, when IFN-gamma and TNF-alpha were added together in the muscle cell cultures, they caused significant cytotoxic effects. Thus, in combination, IFN-gamma and TNF-alpha at 100 U/ml each caused significant release of LDH (3rd day 9%, 4th day 28.5%, 7th day 55.5%, 9th day 74%) in the supernatants of treated cultures compared to controls. Moreover, inspection by phase microscopy showed clear damage of muscle cells; from Days 3 to 4 progressive vacuolation, detachment of cells, and finally disintegration of the muscle cells by the 8th to 10th day was observed. The synergistic cytotoxic effect of IFN-gamma and TNF-alpha occurred at concentrations as low as 1 U/ml and 10 U/ml, respectively. CONCLUSION: Our study demonstrates for the first time a direct synergistic cytotoxic effect of IFN-gamma and TNF-alpha on human muscle cells in culture. Given that T cells and macrophages are prominent in the chronic inflammatory cell infiltrates of the affected muscles in patients with myositis, our findings suggest that IFN-gamma and TNF-alpha may play an important role in the pathogenesis of muscle destruction of this disorder.

Assessment of liver iron overload by T2-quantitative magnetic resonance imaging: correlation of T2-QMRI measurements with serum ferritin concentration and histologic grading of siderosis.

PURPOSE: To correlate hepatic 1/T2 values obtained by means of a T2-Quantitative MRI (T2-QMRI) technique with three widely applied methods for the evaluation of hemosiderosis, i.e., (a) liver iron concentrations (LFeC) (b) serum ferritin (SF), and (c) histologic grading of siderosis. The impact of coexisting hepatitis was also considered. T2-QMRI measurements were compared with signal intensity (SI) ratio measurements on conventional SE images. MATERIALS AND METHODS: Liver T2 relaxation times were calculated in 40 thalassemic patients, on a 0.5 T magnetic resonance imaging system using a multiple spin-echo sequence with parameters: TR = 2500 ms, TE = 12 ms in 20 symmetrically repeatable echoes. RESULTS: (a) 1/T2 values were well correlated (r = 0.97) with liver iron concentrations, which ranged from 2.32 to 18.0 mg/g dry weight (normal < 1.6 mg/g). (b) 1/T2 values were also correlated with serum ferritin levels (r = 0.84). At various 1/T2 values, serum ferritin levels were higher for the anti-HCV(+) patients than the anti-HCV(-) ones. (c) T2 values corresponding to successive grades of siderosis presented statistically significant differences. (d) SI ratio measurement assigned less statistically significant results, as compared to T2 values. CONCLUSION: T2-QMRI measurement of T2 relaxation time is more accurate than SI ratios in evaluating liver iron overload. It is particularly useful for hemosiderotic patients with coexisting hepatitis since, in this case, serum ferritin is not considered a reliable index of hemosiderosis.

Mechanisms of inflammation and histopathology in inflammatory myopathy.

The term inflammatory myopathy describes a group of disorders characterized by mononuclear cell infiltration of muscle tissue. Abnormalities of cell-mediated immunity have been implicated repeatedly in the pathogenesis of these disorders. In recent years, considerable evidence supporting this view has been obtained, strongly suggesting a central role to T cells in the pathogenetic process. This article reviews the immunopathology and the cellular mechanisms involved in the pathogenesis of inflammatory myopathy.

The role of cytokines in polymyositis. III. Recombinant human interferon-gamma enhances T cell adhesion to cultured human muscle cells.

OBJECTIVE: To investigate the effect of interferon-gamma (IFN gamma) on the adhesive interactions between human peripheral blood T cells and human skeletal muscle cells at various stages of muscle cell differentiation and maturation in vitro. METHODS: Human muscle cell cultures were established from normal muscle biopsy material, using the explant technique. T cells were studied for their capacity to adhere to IFN gamma-treated and untreated myoblasts and myotubes. The role of intercellular adhesion molecule type 1 (ICAM-1) in cell adhesion to muscle cells was examined in blocking studies, by enzyme-linked immunosorbent assay (ELISA), and by immunohistochemical staining using monoclonal antibodies (MAb). RESULTS: Treatment of muscle cells (myoblasts and myotubes) with IFN gamma resulted in a significant dose-dependent increase in the number of adherent T cells. Adhesion of T cells to muscle cells was significantly inhibited by MAb to ICAM-1 and to lymphocyte function-associated antigen type 1, but not by MAb to HLA-DR. There was no difference in the level of T cell adhesion to IFN gamma-treated allogeneic versus autologous muscle cells. By ELISA and immunohistochemical analysis, ICAM-1 expression on the surface of cultured human muscle cells was either absent or barely detectable, but was strongly induced by treatment of muscle cells with IFN gamma. CONCLUSION: Induction of cell adhesion molecules on muscle cells by IFN gamma may be an important mechanism for the localization of T cells in the affected muscles of patients with autoimmune myositis.

CT and MR of pineal region tumors.

Magnetic Resonance (MR) imaging features of pineal region tumors were analyzed in 14 oncologic cases. The tumors were classified as germ-cell tumors, glial tumors, pineal parenchymal tumors, meningiomas, and cysts. They demonstrated different MR signal characteristics on precontrast scans and nodular or ring type enhancement with occasional central lucencies, except for benign cysts, which have not shown enhancement. MR images were useful in defining the relationship of the tumor to the posterior third ventricle, sylvian aqueduct, vein of Galen, and tentorium. Although CT can demonstrate in more evident fashion displacement of the original pineal calcification as well as tumor calcifications, MR imaging demonstrates different signal characteristics in germinomas and pineoblastomas which can be a useful adjunct in the evaluation and differential diagnosis of these tumors.

Interferon-gamma inhibits proliferation, differentiation, and creatine kinase activity of cultured human muscle cells. II. A possible role in myositis.

OBJECTIVE: To investigate the effects of human interferon-gamma (IFN-gamma) on cultured human skeletal muscle cells. METHODS: Muscle cell cultures were treated with various concentrations of recombinant human IFN-gamma, and muscle cell proliferation, creatine kinase synthesis and muscle cell cytotoxicity were analyzed. RESULTS: Treatment of muscle cell cultures with IFN-gamma resulted in significant inhibition of myoblasts proliferation, growth, and fusion into multinucleated myotubes. IFN-gamma inhibited creatine kinase synthesis if applied before, but not after, the myoblasts begin to differentiate into myotubes. The effect of IFN-gamma was dose dependent and observed at a concentration of IFN-gamma as low as 10 U/ml. Despite these cytostatic effects, IFN-gamma was not cytotoxic to cultured muscle cells even with very high (10,000 U/ml) IFN-gamma doses. CONCLUSION: IFN-gamma inhibits muscle cell proliferation and differentiation in vitro. These findings suggest that IFN-gamma, a T cell lymphokine, may inhibit muscle regeneration and the repair of injured muscle fibers in myositis.

Spinal neurilemmomas and neurofibromas: central dot sign in postgadolinium MRI.

The MR studies of three histologically proven spinal neurilemmomas and neurofibromas were reviewed retrospectively. There were two benign neurilemmomas (schwannomas) and one neurofibroma. The common characteristic of these cases was a central low intensity focus ("dot") seen on postcontrast T1-weighted imaging. The low intensity foci corresponded histologically to a congeries of changes including edema, microcysts, foam cells, hyalinization of blood vessels, old hemorrhage, and dystrophic calcification.

Immune aspects of myositis.

Myositis describes a heterogeneous group of disorders whose main pathologic feature is chronic inflammation of the affected muscles. The association of myositis with other autoimmune diseases, the response to corticosteroid and immunosuppressive therapy, the frequent occurrence of autoantibodies, and the presence of chronic inflammatory cells in the affected muscles of patients with myositis indicate that the myositis syndromes are autoimmune diseases. This review summarizes recent observations on the role of humoral and cellular mechanisms in myositis. During the past year, the most notable contributions included studies on the relationship among autoantibodies and various clinical and epidemiologic features of patients with myositis; further evidence for T-cell involvement in the pathogenesis of myositis; demonstration of amyloid proteins in muscle fibers of patients with inclusion body myositis; and a controlled trial of plasma exchange and leukapheresis in myositis.

The role of cytokines in polymyositis: interferon-gamma induces class II and enhances class I major histocompatibility complex antigen expression on cultured human muscle cells.

Aberrant expression of class II major histocompatibility complex molecules has been found on target cells of various autoimmune diseases, including muscle fibers in patients with polymyositis-dermatomyositis. In this study the effects of a number of recombinant human cytokines, individually and in combination, on class I and class II molecule expression by cultured human muscle cells were examined with monoclonal antibodies and an immunoperoxidase technique. The following cytokines were tested: interferon-gamma, tumor necrosis factor-alpha, tumor necrosis factor-beta, interleukin-2, interleukin-1 alpha and interleukin-1 beta. Only IFN-gamma induced expression of class II molecules in muscle cells. It also enhanced the preexisting class I molecule expression by muscle cells. These findings suggest that IFN-gamma is involved in the aberrant expression of major histocompatibility complex molecules in the affected muscles of patients with polymyositis-dermatomyositis.

The role of cell-mediated immunity in polymyositis.

Although the etiologic stimulus has not been identified, there is considerable evidence that cell-mediated immune mechanisms play an important role in the pathogenesis of polymyositis-dermatomyositis: 1) a discrete chronic mononuclear cell infiltrate is almost always present in the affected muscles of patients with polymyositis-dermatomyositis; 2) the predominant cell of this chronic mononuclear cell infiltrate is the T lymphocyte; 3) the infiltrating T cells appear to be activated because they express activation antigens, such as major histocompatibility complex class II molecules; 4) peripheral blood lymphocytes express activation markers, they are sensitized to muscle, and they seem to be cytotoxic to muscle in vitro; and 5) pathologic similarities reminiscent of polymyositis are found in animal models of experimental myositis. Recent observations on cell-mediated immunity in polymyositis-dermatomyositis, discussed in this review, provide new insights into the pathogenesis of the inflammatory myopathies.

Polymyositis/dermatomyositis associated with dermatitis herpetiformis.

We describe 2 patients with dermatitis herpetiformis who developed polymyositis/dermatomyositis. On HLA typing, both patients were found to be HLA-B8, DR3 positive. The concurrence of these two relatively rare diseases, both associated with immunologic abnormalities, further supports the role of autoimmunity in their pathogenesis and indicates a possible common genetic basis. It also suggests that myositis may be more common in patients with dermatitis herpetiformis than in the general population.

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.

Relationships between clinical features and distribution of mononuclear cells in muscle of patients with polymyositis.

We examined the relationships between the clinical features and outcome of 43 patients with polymyositis-dermatomyositis (PM-DM) and muscle biopsy findings, with specific reference to the pattern of distribution of inflammatory cells. Perifascicular inflammation was associated with the presence of the rash of DM. No relationships were found between the other patterns of distribution of inflammatory cells in muscle and various clinical findings in patients with PM-DM, or the clinical course of the disease. Vasculitis of large vessels (greater than or equal to 20 micron) was seen in only 5 cases (11%) and was not present in childhood PM-DM.

Effect of mononuclear cell factors on calcium transport in sarcoplasmic reticulum vesicles.

The effect of supernatants from cultures of mitogen-stimulated human mononuclear cells on calcium transport by sarcoplasmic reticulum was examined. Calcium transport was assayed by measuring the time course of calcium accumulation by sarcoplasmic reticulum incubated with supernatants from stimulated mononuclear cells was 20% less than that by vesicles exposed to control supernatants (P less than 0.001). In contrast, no difference in calcium-dependent ATPase activity was noted between vesicles incubated with either active or control supernatants. The results suggest that mononuclear cell factors disturb calcium transport in sarcoplasmic reticulum membrane.

Mononuclear cells from patients with polymyositis inhibit calcium binding by sarcoplasmic reticulum.

We have examined whether peripheral blood mononuclear cells from patients with polymyositis-dermatomyositis (PM-DM) incubated with autologous muscle release mediators that can affect the Ca2+ binding by sarcoplasmic reticulum (SR), the key regulator of muscle contraction. Peripheral blood mononuclear cells from 11 patients with early, active, and untreated PM-DM and from 20 controls were incubated with various dilutions (ranging from 1:60 to 1:4800 wt/vol) of autologous muscle homogenates. Mononuclear cells from eight of 11 patients with PM-DM underwent proliferation as assessed by 3H-thymidine incorporation into mononuclear cells (stimulation indices ranging from 3 to 14). Supernatants from muscle-stimulated mononuclear cells suppressed the adenosine triphosphate-dependent Ca2+ binding by SR membranes derived from rat skeletal muscles. Neither proliferative responses of mononuclear cells nor release of mediators suppressing calcium binding by SR was observed in mononuclear cell cultures of controls. The factor(s) producing suppression of calcium binding by SR was nondialyzable, and its effect on SR was concentration dependent. These results suggest that mononuclear cells in PM-DM are sensitized to autologous muscle and release a soluble factor(s) that inhibits the function of SR muscle membrane. These findings may have important implications in the pathogenesis of muscle weakness in PM-DM.

Human mononuclear cell factors suppress contractility of isolated mouse soleus muscle.

Weakness in polymyositis-dermatomyositis is often greater than would be suggested by histologic evidence of fiber degeneration or necrosis. Mononuclear cell infiltration is the key pathologic feature of polymyositis-dermatomyositis, and previous studies suggest a role for cellular immunity. In this study, the effect of supernatants from mitogen-stimulated human blood mononuclear cells on contractility of isolated mouse normal soleus muscle was examined. Mononuclear cell factor-rich supernatants were generated in 5-day cultures by phytohemagglutinin P stimulation of mononuclear cells from normal volunteers. Mouse soleus muscle was mounted isometrically in a muscle bath filled with oxygenated Ringer's solution or RPMI-1640 and was stimulated electrically. In 10 individual experiments, all muscles exposed to mononuclear cell factor-rich supernatants showed a rapid and progressive decline in active force of isometric contraction; a 40% decrease in active force was observed 5 to 13 minutes (average, 8 minutes) after the addition of supernatant. The inhibitory effect was reversible on removal of mononuclear cell factor-rich supernatants. Control culture medium and supernatants from unstimulated cell cultures showed no appreciable effect on active force. The factor(s) producing suppression of muscle contractility was dialyzable and stable through several cycles of freezing and thawing. Gel chromatography (Sephadex G-25 fine) showed one active fraction corresponding to an apparent molecular weight of approximately 2000. These data indicate that factor(s) released by human mononuclear cells can directly suppress the contraction of normal skeletal muscle.

Dysfunction of the sarcoplasmic reticulum in polymyositis.

The transport of calcium in vesicles of sarcoplasmic reticulum isolated from muscle specimens from 6 patients with early, active polymyositis and from 11 controls was examined. The time courses of calcium uptake and calcium-dependent ATPase activity were measured simultaneously. Calcium uptake by sarcoplasmic reticulum vesicles from patients with polymyositis was 50% less than that by vesicles from controls (P less than 0.001). In contrast, no difference in calcium-dependent ATPase activity was noted between vesicles from patients with polymyositis and controls. The demonstrated defect may be important in the pathogenesis of muscle weakness in polymyositis.