Early-onset Myasthenia Gravis Patients Research Articles

Studying the relationship between clinical features and mental health among late-onset myasthenia gravis patients.

BACKGROUNDMental disorders are common comorbidities among individuals with neurological diseases, and the prevalence of depressive and anxiety-related symptoms in newly referred patients at neurology outpatient clinics is high. There have been few studies on the mental health of patients with late-onset myasthenia gravis (MG).AIMTo examine the relationship between clinical features and the mental health symptoms within late-onset MG patients.METHODSA total of 105 patients diagnosed with MG were recruited consecutively from a neuromuscular outpatient clinic between December 2020 and February 2021. Patients were classified into two groups: early-onset MG (age at onset < 50 years, n = 63) and late-onset MG (age at onset ≥ 50 years, n = 42). Social demographic data and information about marital status, education level, clinical symptoms, serum antibody levels, and therapies used were collected for all participants. Participants were also evaluated using the Myasthenia Gravis Composite scale, the Myasthenia Gravis Activities of Daily Living scale, the Myasthenia Gravis Quality of Life 15 (MG-QOL-15) questionnaire, the 17-item version of the Hamilton Depression Rating Scale (HAM-D) and the Hamilton Anxiety Rating Scale (HAM-A). The relationship between clinical features and mental health in late-onset MG patients was examined using multivariate logistic regression analyses. RESULTSLate-onset MG patients were more prone to dyspnea, had higher levels of serum anti-acetylcholine receptor antibodies, and higher total scores on the MG-QOL-15, HAM-D, and HAM-A questionnaires, than early-onset MG patients had (P < 0.05). Among those with late-onset MG, female patients had higher total HAM-D and HAM-A scores than male patients had (P < 0.05). High scores on the QOL-15 questionnaire were associated with higher incidences of anxiety and depression, and the association was found to be independent after adjusting for confounding risk factors. In the late-onset subgroup, the areas under the receiver operating characteristic curves for the MG-QOL-15 score-based diagnostic accuracy for anxiety and depression state were 0.816 (P = 0.001) and 0.983 (P < 0.001), respectively.CONCLUSIONHigher MG-QOL-15 scores were a risk factor for anxiety and depression in late-onset MG, and women with late-onset MG were more likely to have anxiety and depression than men were.

Rituximab for the treatment of generalised myasthenia gravis: experience in clinical practice

Rituximab (RTX) is an anti-CD20 monoclonal antibody that has been used in cases of refractory myasthenia gravis (MG). The aim of this work is to analyse the efficacy and safety of RTX in MG in real clinical practice in a tertiary hospital. A retrospective study was conducted with patients with MG treated with RTX in our centre from March 2014 to September 2020. Demographic and serological data, together with information about previous immunomodulatory treatment, clinical response and adverse effects are collected. Twenty patients with MG - 100% generalised: 70% late-onset MG (LOMG) and 30% early-onset MG (EOMG) - were given RTX (mean age: 66.8 years; 70% male). A total of 90% are seropositive, 16 of them with positive anti-acetylcholine receptor antibodies and two with positive muscle-specific tyrosine kinase (anti-MuSK) antibodies. All had failed previous treatments: 100% with steroids, 100% with intravenous immunoglobulins and/or plasmapheresis, 55% with other immunosuppressants (25% with one previous immunosuppressant, 10% with two, 15% with three and 5% with four) and 35% with thymectomy. After RTX, 75% of patients showed a clinical response (12 patients with complete remission and the possibility of steroid withdrawal without recurrence; and three patients with partial remission and the possible reduction of steroid dosage) and 25% therapeutic failure; in all these cases RTX was withdrawn. All the anti-MuSK+ patients (100%) and 92.8% of the LOMG patients responded to RTX, while 66% of EOMG patients failed. Only three patients reported adverse effects, all of which were mild and did not require RTX withdrawal. In our experience, rituximab is a safe and effective treatment in aggressive generalised MG with anti-MuSK or late-onset MG (LOMG).

Causes and Consequences of miR-150-5p Dysregulation in Myasthenia Gravis.

Autoimmune Myasthenia gravis (MG) is a chronic neuromuscular disease mainly due to antibodies against the acetylcholine receptor (AChR) at the neuromuscular junction that induce invalidating muscle weaknesses. In early-onset MG, the thymus is the effector organ and is often characterized by B-cell infiltrations leading to ectopic germinal center (GC) development. The microRNA miR-150-5p has been previously characterized as a biomarker in MG due to its increase in the serum of patients and its decrease after thymectomy, correlated with an improvement of symptoms. Here, we investigated the causes and consequences of the miR-150 increase in the serum of early-onset MG patients. We observed that miR-150 expression was upregulated in MG thymuses in correlation with the presence of thymic B cells and showed by in situ hybridization experiments, that miR-150 was mainly expressed by cells of the mantle zone of GCs. However, we did not observe any correlation between the degree of thymic hyperplasia and the serum levels in MG patients. In parallel, we also investigated the expression of miR-150 in peripheral blood mononuclear cells (PBMCs) from MG patients. We observed that miR-150 was down-regulated, especially in CD4+ T cells compared to controls. These results suggest that the increased serum levels of miR-150 could result from a release from activated peripheral CD4+ T cells. Next, we demonstrated that the in vitro treatment of PBMCs with miR-150 or antimiR-150 oligonucleotides, respectively, decreased or increased the expression of one of its major target gene: the proto-oncogene MYB, a well-known actor of hematopoiesis. These results revealed that increased serum levels of miR-150 in MG patients could have a functional effect on PBMCs. We also showed that antimiR-150 caused increased cellular death of CD4+ and CD8+ T cells, along with the overexpression of pro-apoptotic genes targeted by miR-150 suggesting that miR-150 controlled the survival of these cells. Altogether, these results showed that miR-150 could play a role in MG both at the thymic level and in periphery by modulating the expression of target genes and peripheral cell survival.

Challenging the current model of early-onset myasthenia gravis pathogenesis in the light of the MGTX trial and histological heterogeneity of thymectomy specimens.

The MGTX trial provided evidence that, in general, thymectomy is beneficial in adult patients up to 60 years of age with anti-acetylcholine receptor-positive, nonthymomatous myasthenia gravis (MG). This finding supports the long-held view that the pathogenesis of this type of MG (early-onset MG (EOMG)) starts inside the thymus, results in the long-term intrathymic recruitment of autoantibody-producing B cells and plasma cells, and eventually spreads to the peripheral immune system. However, observed clinical responses to treatment in the MGTX trial were diverse. This might be due to heterogeneous epidemiological and genetic features of EOMG patients and variable durations of corticosteroid treatment before surgery, including a paucity of patients that were corticosteroid naive. Furthermore, the observed histological heterogeneity suggests that a single pathogenetic model may not fully reflect the spectrum of events that modify the course of EOMG. Here, we describe the morphology of the normal and MG-associated thymus, how to evaluate morphological changes, and the current pathogenetic model of EOMG and discuss how it could be refined by integrating MGTX-derived histological findings in thymectomy specimens and associated clinical observations.

Juvenile-onset myasthenia gravis: autoantibody status, clinical characteristics and genetic polymorphisms.

Myasthenia gravis (MG) is an autoimmune disorder mediated by antibodies against proteins at the neuromuscular junction. Juvenile-onset MG (JMG) has been reported to have special characteristics. It is still unclear whether there are any pathogenic and genetic differences between juvenile and adult MG. In this study, we evaluated the clinical characteristics, autoantibody status (antibodies against AChR, MuSK, LRP4, titin and RyR) and genetic susceptibility (CHRNA1, CTLA4 and AIRE) in 114 Chinese JMG patients, and compared with 207 young adult MG patients (onset age 18-40years). JMG patients were classified into two subgroups: the very early onset group (<8years) and puberty onset group (8-18years). The very early onset MG patients had a higher proportion of ocular MG and thymus hyperplasia, compared with puberty onset MG and young adult MG (P<0.05). AChR antibodies were found in majority of JMG patients and were associated with more severe disease (P<0.05), while other antibodies were rare in JMG. Moreover, the very early onset MG had a more prominent genetic predisposition than puberty and adult MG, affecting the susceptible genes CHRNA1 and CTLA4. JMG has the same pathogenic background as adult MG, but has typical clinical features and a prominent genetic predisposition in very early onset patients (<8years). Specific therapeutic considerations are needed.

Thymic Germinal Centers and Corticosteroids in Myasthenia Gravis: an Immunopathological Study in 1035 Cases and a Critical Review.

The most common form of Myasthenia gravis (MG) is due to anti-acetylcholine receptor (AChR) antibodies and is frequently associated with thymic pathology. In this review, we discuss the immunopathological characteristics and molecular mechanisms of thymic follicular hyperplasia, the effects of corticosteroids on this thymic pathology, and the role of thymic epithelial cells (TEC), a key player in the inflammatory thymic mechanisms. This review is based not only on the literature data but also on thymic transcriptome results and analyses of pathological and immunological correlations in a vast cohort of 1035 MG patients without thymoma. We show that among patients presenting a thymic hyperplasia with germinal centers (GC), 80% are females, indicating that thymic follicular hyperplasia is mainly a disease of women. The presence of anti-AChR antibodies is correlated with the degree of follicular hyperplasia, suggesting that the thymus is a source of anti-AChR antibodies. The degree of hyperplasia is not dependent upon the time from the onset, implying that either the antigen is chronically expressed and/or that the mechanisms of the resolution of the GC are not efficiently controlled. Glucocorticoids, a conventional therapy in MG, induce a significant reduction in the GC number, together with changes in the expression of chemokines and angiogenesis. These changes are likely related to the acetylation molecular process, overrepresented in corticosteroid-treated patients, and essential for gene regulation. Altogether, based on the pathological and molecular thymic abnormalities found in MG patients, this review provides some explanations for the benefit of thymectomy in early-onset MG patients.

Proteasome inhibition with bortezomib depletes plasma cells and specific autoantibody production in primary thymic cell cultures from early-onset myasthenia gravis patients.

Bortezomib is a potent inhibitor of proteasomes currently used to eliminate malignant plasma cells in multiple myeloma patients. It is also effective in depleting both alloreactive plasma cells in acute Ab-mediated transplant rejection and their autoreactive counterparts in animal models of lupus and myasthenia gravis (MG). In this study, we demonstrate that bortezomib at 10 nM or higher concentrations killed long-lived plasma cells in cultured thymus cells from nine early-onset MG patients and consistently halted their spontaneous production not only of autoantibodies against the acetylcholine receptor but also of total IgG. Surprisingly, lenalidomide and dexamethasone had little effect on plasma cells. After bortezomib treatment, they showed ultrastructural changes characteristic of endoplasmic reticulum stress after 8 h and were no longer detectable at 24 h. Bortezomib therefore appears promising for treating MG and possibly other Ab-mediated autoimmune or allergic disorders, especially when given in short courses at modest doses before the standard immunosuppressive drugs have taken effect.

VAV1 and BAFF, via NFκB pathway, are genetic risk factors for myasthenia gravis.

ObjectiveTo identify novel genetic loci that predispose to early-onset myasthenia gravis (EOMG) applying a two-stage association study, exploration, and replication strategy.MethodsThirty-four loci and one confirmation loci, human leukocyte antigen (HLA)-DRA, were selected as candidate genes by team members of groups involved in different research aspects of MG. In the exploration step, these candidate genes were genotyped in 384 EOMG and 384 matched controls and significant difference in allele frequency were found in eight genes. In the replication step, eight candidate genes and one confirmation loci were genotyped in 1177 EOMG patients and 814 controls, from nine European centres.ResultsAllele frequency differences were found in four novel loci: CD86, AKAP12, VAV1, B-cell activating factor (BAFF), and tumor necrosis factor-alpha (TNF-α), and these differences were consistent in all nine cohorts. Haplotype trend test supported the differences in allele frequencies between cases and controls. In addition, allele frequency difference in female versus male patients at HLA-DRA and TNF-α loci were observed.InterpretationThe genetic associations to EOMG outside the HLA complex are novel and of interest as VAV1 is a key signal transducer essential for T- and B-cell activation, and BAFF is a cytokine that plays important roles in the proliferation and differentiation of B-cells. Moreover, we noted striking epistasis between the predisposing VAV1 and BAFF haplotypes; they conferred a greater risk in combination than alone. These, and CD86, share the same signaling pathway, namely nuclear factor-kappaB (NFκB), thus implicating dysregulation of proinflammatory signaling in predisposition to EOMG.

Clonal heterogeneity of thymic B cells from early-onset myasthenia gravis patients with antibodies against the acetylcholine receptor

Myasthenia gravis (MG) with antibodies against the acetylcholine receptor (AChR–MG) is considered as a prototypic autoimmune disease. The thymus is important in the pathophysiology of the disease since thymus hyperplasia is a characteristic of early-onset AChR–MG and patients often improve after thymectomy. We hypothesized that thymic B cell and antibody repertoires of AChR–MG patients differ intrinsically from those of control individuals. Using immortalization with Epstein–Barr Virus and Toll-like receptor 9 activation, we isolated and characterized monoclonal B cell lines from 5 MG patients and 8 controls. Only 2 of 570 immortalized B cell clones from MG patients produced antibodies against the AChR (both clones were from the same patient), suggesting that AChR-specific B cells are not enriched in the thymus. Surprisingly, many B cell lines from both AChR–MG and control thymus samples displayed reactivity against striated muscle proteins. Striational antibodies were produced by 15% of B cell clones from AChR–MG versus 6% in control thymus. The IgVH gene sequence analysis showed remarkable similarities, concerning VH family gene distribution, mutation frequency and CDR3 composition, between B cells of AChR–MG patients and controls. MG patients showed clear evidence of clonal B cell expansion in contrast to controls. In this latter aspect, MG resembles multiple sclerosis and clinically isolated syndrome, but differs from systemic lupus erythematosus.Our results support an antigen driven immune response in the MG thymus, but the paucity of AChR-specific B cells, in combination with the observed polyclonal expansions suggest a more diverse immune response than expected.

Proteasome inhibition with bortezomib depletes plasma cells and autoantibody production in primary thymic cell cultures from early-onset myasthenia gravis patients (P5146)

Abstract In the autoimmune disease myasthenia gravis (MG), autoantibodies against the muscle AChR are mainly produced by both short- and long-lived plasma cells, which are resistant to standard immunosuppressive drugs (i.e. glucocorticoids). A novel therapy to eliminate plasma cells is the proteasome inhibitor bortezomib, which is used to treat patients with multiple myeloma (MM, a plasma cell malignancy). Previously, we demonstrated that bortezomib also reduced autoantibody titers in an animal model of MG (Gomez, A. M. J. Immunol. 2011). The thymus of MG patients is frequently enriched in germinal centers and contains plasma cells that produce autoantibodies in vitro, even after irradiation (which depletes B and T lymphocytes). We studied the in vitro effects of bortezomib in cultured thymus cells from MG patients undergoing therapeutic thymectomy. Treatment with a single dose of bortezomib blocked the production of these pathogenic autoantibodies, reduced the total IgG levels and eliminated plasma cells. Ultrastructural signs of apoptosis were detected in plasma cells as early as 8 h after addition of bortezomib; at 24 h, no plasma cells could be detected. Moreover, we demonstrated that the minimum concentration of bortezomib that eliminates plasma cells in vitro is 60-fold lower than the peak concentration found in MM patients treated with bortezomib, suggesting that low doses might be effective for eliminating plasma cells in patients with antibody-mediated autoimmune diseases.

Recent advances in genetic predisposition of myasthenia gravis.

Myasthenia gravis (MG) is an autoimmune disease mediated by the presence of autoantibodies that bind to components of the neuromuscular junction, causing the symptoms of muscular weakness and fatigability. Like most autoimmune disorders, MG is a multifactorial, noninherited disease, though with an established genetic constituent. The heterogeneity observed in MG perplexes genetic analysis even more, as it occurs in various levels, including diverse autoantigens, thymus histopathology, and age at onset. In this context of distinct subgroups, a plethora of association studies, discussed in this review, have assessed the involvement of various HLA and non-HLA related loci in MG susceptibility, over the past five years. As expected, certain HLA alleles were strongly associated with MG. Many of the non-HLA genes, such as PTPN22 and CTLA-4, have been previously studied in MG and other autoimmune diseases and their association with MG has been reevaluated in more cohesive groups of patients. Moreover, novel risk or protective loci have been revealed, as in the case of TNIP1 and FOXP3. Although the majority of these results have been derived from candidate gene studies, the focal point of all recent genetic studies is the first genome-wide association study (GWAS) conducted on early-onset MG patients.

Risk for myasthenia gravis maps to a 151Pro→Ala change in TNIP1 and to human leukocyte antigen‐B*08

The objective of this study is to comprehensively define the genetic basis of early onset myasthenia gravis (EOMG). We have carried out a 2-stage genome-wide association study on a total of 649 North European EOMG patients. Cases were matched 1:4 with controls of European ancestry. We performed imputation and conditional analyses across the major histocompatibility complex, as well as in the top regions of association outside the human leukocyte antigen (HLA) region. We observed the strongest association in the HLA class I region at rs7750641 (p = 1.2 × 10(-92) ; odds ratio [OR], 6.25). By imputation and conditional analyses, HLA-B*08 proves to be the major associated allele (p = 2.87 × 10(-113) ; OR, 6.41). In addition to the expected association with PTPN22 (rs2476601; OR, 1.71; p = 8.2 × 10(-10) ), an imputed coding variant (rs2233290) at position 151 (Pro→Ala) in the TNFAIP3-interacting protein 1, TNIP1, confers even stronger risk than PTPN22 (OR, 1.91; p = 3.2 × 10(-10) ). The association at TNIP1 in EOMG implies disease mechanisms involving ubiquitin-dependent dysregulation of NF-κB signaling. The localization of the major HLA signal to the HLA-B*08 allele suggests that CD8(+) T cells may play a key role in disease initiation or pathogenesis.

BAFF serum levels in myasthenia gravis: effects of therapy

B lymphocyte activating factor (BAFF) belonging to the tumour necrosis factor (TNF) ligand super-family is a key survival factor for B lymphocytes [1]. In transgenic mice, BAFF overproduction is associated with lymphocytic disorders and autoimmunity [2], and increased serum BAFF levels are found in human autoimmune diseases [3]. Myasthenia gravis (MG) is an antibody-mediated disease of neuromuscular transmission. Most patients have serum antibodies against the acetylcholine receptor (AChR). Anti-AChR positive MG is associated with thymus alterations, such as follicular hyperplasia and thymoma [4]. Thymus hyperplasia is characterized by expanded thymus perivascular spaces with infiltration of T and B lymphocytes and germinal centre formation; BAFF was found to be expressed in the MG hyperplastic thymus where it could foster a microenvironment permissive to B-cells [5]. Our aim was to evaluate serum BAFF levels in MG patients in different phases of their disease and the effects of therapy. We tested serum samples from 66 patients, 52 women and 14 men (M/W: 1/3.7) aged 14–74 years (mean 39) and 41 healthy controls, 32 women and 9 men (M/W: 1/3.5), aged 20–66 years (mean 41). Patient population included: 61 anti-AChR positive (42 early-onset, 11 lateonset and 8 thymoma) and 5 early-onset anti-AChR negative MG cases. No patient had anti-muscle specific kinase (MuSK) antibodies. All patients but two had generalized disease. Thymectomy was performed on all thymoma cases and 42/47 early-onset MG patients; a typical thymus hyperplasia was found in 35/42 of these cases. BAFF levels were measured in 52 patients before immunosuppressive (IS) treatment; in 13 of these cases, who had undergone thymectomy with histological findings of thymus hyperplasia, we evaluated serial samples taken before and 5–33 years after thymectomy; 14 patients were under IS therapy (mostly with prednisone) at the inclusion. BAFF levels were measured in duplicate by quantitative sandwich enzyme immunoassay using commercial Quantikine kit (R&D Systems, USA). The normal range for the BAFF assay was defined by the geometric mean BAFF level ?2 SD in controls. Statistical analysis was performed by paired and unpaired Student t test and ANOVA. All patients and controls gave informed consent to the study. Mean serum BAFF levels were significantly higher in the MG population (938.8 ± 284 pg/mL) than in controls (797 ± 192 pg/mL) (p = 0.005). Overall, 20/66 patients (30.3%) had BAFF levels above the normal range. BAFF values did not correlate with disease severity. In 33 MG samples taken before any treatment the mean BAFF value was 953 ± 268 pg/mL, and it did not differ in 19 samples from patients who had undergone thymectomy and had never received IS therapy (1,060 ± 266 pg/mL) (p = 0.14). In the 13 patients in whom serial samples (before and after thymectomy) were tested, serum BAFF levels did not significantly change after thymectomy (p = 0.22) (Fig. 1) with no clearly correlation with clinical outcome. On the other hand, in MG patients under IS therapy, BAFF This study has been approved by the local ethics committee and has been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki.

Titin and ryanodine receptor antibodies and neuromuscular involvement in myasthenia gravis

Of sera of patients with myasthenia gravis (MG), 30% contains titin and ryanodine receptor (RyR) antibodies. In early-onset MG (i.e., before 50 years of age), the presence of titin antibodies strongly suggests a thymoma. Late-onset MG comprises one MG group, characterized by a broad antimuscle immune response, including both titin and the acetylcholine receptor (AChR). Another group is preferentially associated with the HLA-A3, B7 and DRw2 antigens, representing a delayed early-onset of the disease that has a selective AChR immune response. The presence of titin and RyR antibodies is associated with more severe disease. Titin antibodies may, in some patients with rippling muscle disease, affect the contractile machinery of myofibers, thereby affecting their mechanical sensitivity. It is not known whether this occurs in MG. RyR antibodies may impair excitation–contraction coupling and contribute to muscle weakness in MG patients. Titin antibodies may serve as tumor markers in early-onset MG patients.

Antigen‐specific T‐cell activation in hyperplastic thymus in myasthenia gravis

In order to determine whether antigen-specific T-cell activation by dendritic cells (DCs) is accelerated in thymuses exhibiting lymphofollicular hyperplasia (TLFH) among patients with early-onset myasthenia gravis (EOMG), we investigated the expression levels of phosphorylated protein kinase C (PKC)theta and the local relationship between the presence of phosphorylated PKCtheta and the homing receptor CD44 or CD83, a marker for mature DCs, in samples taken from EOMG patients with early improvement following thymectomy, in remnant thymuses from late-onset MG patients, and in non-MG control thymuses. Antigen-specific T-cell activation was markedly accelerated in TLFH from EOMG patients. Activated T cells and adjacent DCs appeared to be components of a CD44(high) cell population circulating from the blood to the thymus. Although there is no convincing evidence that thymectomy is of benefit in MG, in some EOMG patients with early improvement following thymectomy, blockade of CD44-associated circulation mechanisms is probably the cause for the early benefits of thymectomy and is a potential alternative to thymectomy.

Myasthenia gravis: disease severity and prognosis

To examine myasthenia gravis (MG) severity and long-term prognosis in seronegative, seropositive, and thymoma MG. Four series of patients were studied retrospectively. Severity and treatment were assessed each year, and muscle antibodies were assayed. Seropositive MG patients had a more severe course than seronegative MG patients. MG severity was higher in non-thymectomized compared to thymectomized early-onset MG patients. MG severity did not differ between thymectomized and non-thymectomized late-onset patients. There was no significant difference in MG severity between thymoma and non-thymoma MG patients. MG is more severe in seropositive MG patients. With proper treatment, especially early thymectomy, the long-term prognosis is good in seropositive MG patients. The present studies indicate a benefit of thymectomy in early-onset MG, but no dramatic benefit in late-onset MG. Similar MG severity and outcome was seen in thymoma and non-thymoma MG.

A CTLA4high genotype is associated with myasthenia gravis in thymoma patients

Myasthenia gravis (MG) in thymoma patients depends critically on intratumorous generation and export of mature autoreactive CD4+ T cells. Why non-MG thymomas fail to produce CD4+ T cells is unknown. We studied three single-nucleotide polymorphisms of the cytotoxic T-lymphocyte-associated antigen 4(CTLA4) gene in thymoma patients, nonthymoma early-onset MG patients, and control subjects. Surprisingly, the CTLA4high genotype +49A/A, which is protective against several autoimmune diseases, exerted a prominent predisposing effect to paraneoplastic MG in thymoma patients. The unusual disease association with a CTLA4high genotype implies a unique pathogenesis of paraneoplastic MG, with high CTLA4 levels possibly supporting the nontolerogenic selection of CD4+ T cells in MG-associated thymomas.

The role of complement in myasthenia gravis: serological evidence of complement consumption in vivo

Background Antibodies to the acetylcholine receptor (AChR) titin and the ryanodine receptor (RyR) occur in myasthenia gravis (MG). These antibodies are capable of complement activation in vitro. The involvement of the complement system should cause consumption of complement components such as C3 and C4 in vivo. Materials and methods Complement components C3 and C4 were assayed in sera from 78 AChR antibody-positive MG patients and 52 healthy controls. Forty-eight of the patient sera contained titin antibodies as well, and 20 were also RyR antibody-positive. Results MG patients with AChR antibody concentrations above the median (11.2 nmol/l) had significantly lower mean C3 and C4 concentrations in serum compared to those with AChR antibody concentrations below the median. Titin antibody-positive MG patients, titin antibody-negative early-onset MG patients, titin antibody-negative late-onset MG patients, and controls had similar C3 and C4 concentrations. Nor did mean C3 and C4 concentrations differ in MG patients with RyR antibodies. Patients with severe MG (grades 4 and 5) had similar C3 and similar C4 levels compared to those with mild MG (grades 1 and 2). Conclusion An increased in vivo complement consumption was detected in MG patients with high AChR antibody concentrations, unrelated to MG severity and non-AChR muscle antibodies.

Circulating regulatory anti-T cell receptor antibodies in patients with myasthenia gravis.

Serum anti-T cell receptor (TCR) Ab's are involved in immune regulation directed against pathogenic T cells in experimental models of autoimmune diseases. Our identification of a dominant T cell population expressing the Vbeta5.1 TCR gene (TCRBV5-1), which is responsible for the production of pathogenic anti-acetylcholine receptor (AChR) autoantibodies in HLA-DR3 patients with early-onset myasthenia gravis (EOMG), prompted us to explore the occurrence, reactivity, and regulatory role of anti-TCR Ab's in EOMG patients and disease controls with clearly defined other autoantibodies. In the absence of prior vaccination against the TCR, EOMG patients had elevated anti-Vbeta5.1 Ab's of the IgG class. This increase was restricted largely to EOMG cases with HLA-DR3 and with less severe disease, and it predicted clinical improvement in follow-up studies. EOMG patient sera containing anti-TCR Ab's bound specifically the native TCR on intact Vbeta5.1-expressing cells and specifically inhibited the proliferation and IFN-gamma production of purified Vbeta5.1-expressing cells to alloantigens in mixed lymphocyte reaction and the proliferation of a Vbeta5.1-expressing T cell clone to an AChR peptide, indicating a regulatory function for these Ab's. This evidence of spontaneously active anti-Vbeta5.1 Ab's in EOMG patients suggests dynamic protective immune regulation directed against the excess of pathogenic Vbeta5.1-expressing T cells. Though not sufficient to prevent a chronic, exacerbated autoimmune process, it might be boosted using a TCR peptide as vaccine.

HLA-DPB1 polymorphisms in patients with hyperthyroid Graves' disease and early onset myasthenia gravis.

Using the technique of in vitro enzymatic DNA amplification and dot blot hybridization with sequence-specific oligonucleotide (SSO) probes, a study of genetic polymorphism of HLA-DPB1 was performed in 83 unrelated patients with Graves' disease (GD), 48 patients with early onset myasthenia gravis (EOMG) and 100 normal British caucasoid subjects who were also tissue typed for HLA-A, B and DR antigens. HLA-DPB1*0401 was the commonest allele in both patient and control groups with gene frequencies of 0.380, 0.333 and 0.445 for GD, EOMG and controls, respectively. No significant independent association was found with any HLA-DPB1 allele. As expected, HLA-DR17 is significantly associated with Graves' disease (pc < 8 x 10(-3), RR = 2.9), while both HLA-B8 and DR17 are significantly associated with EOMG (pc < 2 x 10(-7), RR = 10.3 and pc < 0.02, RR = 3.4, respectively)] HLA-DR2 is also significantly increased in EOMG patients who were negative for HLA-DR17 (pc < 0.02, RR = 6.4). In addition, the co-occurrence of HLA-B8 with DPB1*0402 was significantly commoner in patients with GD (p < 0.021, RR = 6.2) and EOMG (p < 0.0007, RR = 10.8) than in controls, although the HLA-DPB1*0402 by itself showed no significant increase.