Guideline for the management of myasthenic syndromes.

Myasthenia gravis (MG), Lambert-Eaton myasthenic syndrome (LEMS), and congenital myasthenic syndromes (CMS) represent an etiologically heterogeneous group of (very) rare chronic diseases. MG and LEMS have an autoimmune-mediated etiology, while CMS are genetic disorders. A (strain dependent) muscle weakness due to neuromuscular transmission disorder is a common feature. Generalized MG requires increasingly differentiated therapeutic strategies that consider the enormous therapeutic developments of recent years. To include the newest therapy recommendations, a comprehensive update of the available German-language guideline 'Diagnostics and therapy of myasthenic syndromes' has been published by the German Neurological society with the aid of an interdisciplinary expert panel. This paper is an adapted translation of the updated and partly newly developed treatment guideline. It defines the rapid achievement of complete disease control in myasthenic patients as a central treatment goal. The use of standard therapies, as well as modern immunotherapeutics, is subject to a staged regimen that takes into account autoantibody status and disease activity. With the advent of modern, fast-acting immunomodulators, disease activity assessment has become pivotal and requires evaluation of the clinical course, including severity and required therapies. Applying MG-specific scores and classifications such as Myasthenia Gravis Activities of Daily Living, Quantitative Myasthenia Gravis, and Myasthenia Gravis Foundation of America allows differentiation between mild/moderate and (highly) active (including refractory) disease. Therapy decisions must consider age, thymic pathology, antibody status, and disease activity. Glucocorticosteroids and the classical immunosuppressants (primarily azathioprine) are the basic immunotherapeutics to treat mild/moderate to (highly) active generalized MG/young MG and ocular MG. Thymectomy is indicated as a treatment for thymoma-associated MG and generalized MG with acetylcholine receptor antibody (AChR-Ab)-positive status. In (highly) active generalized MG, complement inhibitors (currently eculizumab and ravulizumab) or neonatal Fc receptor modulators (currently efgartigimod) are recommended for AChR-Ab-positive status and rituximab for muscle-specific receptor tyrosine kinase (MuSK)-Ab-positive status. Specific treatment for myasthenic crises requires plasmapheresis, immunoadsorption, or IVIG. Specific aspects of ocular, juvenile, and congenital myasthenia are highlighted. The guideline will be further developed based on new study results for other immunomodulators and biomarkers that aid the accurate measurement of disease activity.

International Consensus Guidance for Management of Myasthenia Gravis: 2020 Update.

OBJECTIVE: To update the 2016 formal consensus-based guidance for the management of myasthenia gravis (MG) based on the latest evidence in the literature. METHODS: In October 2013, the Myasthenia Gravis Foundation of America appointed a Task Force to develop treatment guidance for MG, and a panel of 15 international experts was convened. The RAND/UCLA appropriateness method was used to develop consensus recommendations pertaining to 7 treatment topics. In February 2019, the international panel was reconvened with the addition of one member to represent South America. All previous recommendations were reviewed for currency, and new consensus recommendations were developed on topics that required inclusion or updates based on the recent literature. Up to 3 rounds of anonymous e-mail votes were used to reach consensus, with modifications to recommendations between rounds based on the panel input. A simple majority vote (80% of panel members voting "yes") was used to approve minor changes in grammar and syntax to improve clarity. RESULTS: The previous recommendations for thymectomy were updated. New recommendations were developed for the use of rituximab, eculizumab, and methotrexate as well as for the following topics: early immunosuppression in ocular MG and MG associated with immune checkpoint inhibitor treatment. CONCLUSION: This updated formal consensus guidance of international MG experts, based on new evidence, provides recommendations to clinicians caring for patients with MG worldwide.

Fingolimod effects in neuroinflammation: Regulation of astroglial glutamate transporters?

Fingolimod is an oral sphingosine-1-phosphate-receptor modulator which reduces the recirculation of immune cells and may also directly target glial cells. Here we investigate effects of fingolimod on expression of astroglial glutamate transporters under pro-inflammatory conditions. In astrocyte cell culture, the addition of pro-inflammatory cytokines led to a significant downregulation of glutamate transporters glutamate transporter-1 (slc1a2/SLC1A2) and glutamate aspartate transporter (slc1a3/SLC1A3) expression on the mRNA or protein level. In this setting, the direct application of fingolimod-1 phosphate (F1P) on astrocytes did not change expression levels of slc1a2 and slc1a3 mRNA. The analysis of both transporters on the protein level by Western Blot and immunocytochemistry did also not reveal any effect of F1P. On a functional level, the addition of conditioned supernatants from F1P treated astrocytes to neuronal cell culture did not result in increased neurite growth. In experimental autoimmune encephalomyelitis as a model of multiple sclerosis, fingolimod treatment reduced T cell and macrophages/microglia mediated inflammation and also diminished astrocyte activation. At the same time, fingolimod restored the reduced expression of slc1a2 and slc1a3 in the inflamed spinal cord on the mRNA level and of SLC1A2 and SLC1A3 on the protein level, presumably via indirect, anti-inflammatory mechanisms. These findings provide further evidence for a predominantly peripheral effect of the compound in neuroinflammation.

International consensus guidance for management of myasthenia gravis: Executive summary.

OBJECTIVE: To develop formal consensus-based guidance for the management of myasthenia gravis (MG). METHODS: In October 2013, the Myasthenia Gravis Foundation of America appointed a Task Force to develop treatment guidance for MG, and a panel of 15 international experts was convened. The RAND/UCLA appropriateness methodology was used to develop consensus guidance statements. Definitions were developed for goals of treatment, minimal manifestations, remission, ocular MG, impending crisis, crisis, and refractory MG. An in-person panel meeting then determined 7 treatment topics to be addressed. Initial guidance statements were developed from literature summaries. Three rounds of anonymous e-mail votes were used to attain consensus on guidance statements modified on the basis of panel input. RESULTS: Guidance statements were developed for symptomatic and immunosuppressive treatments, IV immunoglobulin and plasma exchange, management of impending and manifest myasthenic crisis, thymectomy, juvenile MG, MG associated with antibodies to muscle-specific tyrosine kinase, and MG in pregnancy. CONCLUSION: This is an international formal consensus of MG experts intended to be a guide for clinicians caring for patients with MG worldwide.

Guidelines on dermatomyositis--excerpt from the interdisciplinary S2k guidelines on myositis syndromes by the German Society of Neurology.

The present guidelines on dermatomyositis (DM) represent an excerpt from the interdisciplinary S2k guidelines on myositis syndromes of the German Society of Neurology (available at www.awmf.org). The cardinal symptom of myositis in DM is symmetrical proximal muscle weakness. Elevated creatine kinase, CRP or ESR as well as electromyography and muscle biopsy also provide important diagnostic clues. Pharyngeal, respiratory, cardiac, and neck muscles may also be affected. Given that approximately 30% of patients also develop interstitial lung disease, pulmonary function tests should be part of the diagnostic workup. Although the cutaneous manifestations in DM are variable, taken together, they represent a characteristic and crucial diagnostic criterion for DM. Approximately 5-20% of individuals exhibit typical skin lesions without any clinically manifest muscle involvement (amyopathic DM). About 30% of adult DM cases are associated with a malignancy. This fact, however, should not delay the treatment of severe myositis. Corticosteroids are the therapy of choice in myositis (1-2 mg/kg). Additional immunosuppressive therapy is frequently required (azathioprine, for children methotrexate). In case of insufficient therapeutic response, the use of intravenous immunoglobulins is justified. The benefit of rituximab has not been conclusively ascertained yet. Acute therapeutic management is usually followed by low-dose maintenance therapy for one to three years. Skin lesions do not always respond sufficiently to myositis therapy. Effective treatment for such cases consists of topical corticosteroids and sometimes also calcineurin inhibitors. Systemic therapies shown to be effective include antimalarial agents (also in combination), methotrexate, and corticosteroids. Intravenous immunoglobulins or rituximab may also be helpful. UV protection is an important prophylactic measure.

Clinical features, pathogenesis, and treatment of myasthenia gravis: a supplement to the Guidelines of the German Neurological Society.

Myasthenia gravis (MG) is an autoimmune antibody-mediated disorder of neuromuscular synaptic transmission. The clinical hallmark of MG consists of fluctuating fatigability and weakness affecting ocular, bulbar and (proximal) limb skeletal muscle groups. MG may either occur as an autoimmune disease with distinct immunogenetic characteristics or as a paraneoplastic syndrome associated with tumors of the thymus. Impairment of central thymic and peripheral self-tolerance mechanisms in both cases is thought to favor an autoimmune CD4(+) T cell-mediated B cell activation and synthesis of pathogenic high-affinity autoantibodies of either the IgG1 and 3 or IgG4 subclass. These autoantibodies bind to the nicotinic acetylcholine receptor (AchR) itself, or muscle-specific tyrosine-kinase (MuSK), lipoprotein receptor-related protein 4 (LRP4) and agrin involved in clustering of AchRs within the postsynaptic membrane and structural maintenance of the neuromuscular synapse. This results in disturbance of neuromuscular transmission and thus clinical manifestation of the disease. Emphasizing evidence from clinical trials, we provide an updated overview on immunopathogenesis, and derived current and future treatment strategies for MG divided into: (a) symptomatic treatments facilitating neuromuscular transmission, (b) antibody-depleting treatments, and

Pivotal Role for CD16+ Monocytes in Immune Surveillance of the Central Nervous System.

Monocytes represent a heterogeneous population of primary immune effector cells. At least three different subsets can be distinguished based on expression of the low-affinity FcγRIII: CD14(++)CD16 -: classical monocytes, CD14(++)CD16(+) intermediate monocytes, and CD14(+)CD16 ++: non-classical monocytes. Whereas CD16 -: classical monocytes are considered key players in multiple sclerosis (MS), little is known on CD16(+) monocytes and how they contribute to the disease. In this study, we examined the frequency and phenotype of monocyte subpopulations in peripheral blood, cerebrospinal fluid (CSF), and brain biopsy material derived from MS patients and controls. Furthermore, we addressed a possible monocyte dysfunction in MS and analyzed migratory properties of monocyte subsets using human brain microvascular endothelial cells. Our ex vivo studies demonstrated that CD16(+) monocyte subpopulations are functional but numerically reduced in the peripheral blood of MS patients. CD16(+) monocytes with an intermediate-like phenotype were found to be enriched in CSF and dominated the CSF monocyte population under noninflammatory conditions. In contrast, an inversed CD16(+) to CD16 -: CSF monocyte ratio was observed in MS patients with relapsing-remitting disease. Newly infiltrating, hematogenous CD16(+) monocytes were detected in a perivascular location within active MS lesions, and CD16(+) monocytes facilitated CD4(+) T cell trafficking in a blood -: brain barrier model. Our findings support an important role of CD16(+) monocytes in the steady-state immune surveillance of the CNS and suggest that CD16(+) monocytes shift to sites of inflammation and contribute to the breakdown of the blood-brain barrier in CNS autoimmune diseases.

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

OBJECTIVE: To identify novel genetic loci that predispose to early-onset myasthenia gravis (EOMG) applying a two-stage association study, exploration, and replication strategy. METHODS: Thirty-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. RESULTS: ALLELE 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. INTERPRETATION: The 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.

Anti-agrin autoantibodies in myasthenia gravis.

OBJECTIVE: Because the extracellular matrix protein agrin is essential for neuromuscular junction formation and maintenance, we tested the hypothesis that autoantibodies against agrin are present in sera from patients with myasthenia gravis (MG). METHODS: We determined the presence of anti-agrin antibodies in 54 sera from patients with generalized MG using a solid-phase ELISA with purified mini-agrin protein. Thirty of the 54 sera were seronegative for antibodies against the acetylcholine receptor (AChR) or muscle-specific tyrosine kinase (MuSK), 15 had elevated levels of anti-MuSK, and 9 had elevated levels of anti-AChR autoantibodies. Sixteen sera from healthy volunteers served as control. RESULTS: Five sera with elevated levels of anti-agrin antibodies were identified. The concentration of the antibodies ranged between 0.04 and 0.12 nM. Four of the 5 agrin-positive sera were also positive for anti-MuSK, one was positive for anti-AChR, and 2 had elevated levels of anti-low-density lipoprotein receptor-related protein 4 (LRP4) autoantibodies. Some of the sera stained adult mouse neuromuscular junctions and reacted with native mini-agrin expressed in 293HEK cells. CONCLUSIONS: The results provide evidence for agrin as a novel target protein for autoantibodies in patients with MG. Anti-agrin antibodies were always detected in combination with autoantibodies against MuSK, LRP4, or AChRs, indicating a high incidence of autoantibodies against several neuromuscular proteins in the agrin-positive MG cases.

New poteintial serum biomarkers in multiple sclerosis identified by proteomic strategies.

Proteome analysis of body fluids is a powerful tool to identify biomarkers of neurological disorders. Multiple sclerosis (MScl) is a chronic disabling disorder of central nervous system (CNS) and is regarded as an autoimmune disease to myelin components. Clinical subtypes of MScl differ in course, prognosis and response to available therapy. There is evidence of a different pattern of CNS lesions in subtypes, suggesting different immunological mechanisms are relevant in inflammatory demyelination. In order to elucidate proteome signatures, we used two-dimensional differential gel electrophoresis (2D-DIGE) to compare the protein expression profile in serum of different clinical subtypes of MScl patients and of healthy volunteers, resp. controls. Significant expression differences were detected by 2D-DIGE for 241 serum proteins, and transthyretin, zinc-alpha-2-glycoprotein, alpha-1-antitrypsin, immunoglobulin and complement factors (C4, C6 and C8) were identified as potential disease signatures for MScl patients. Three highly-expressed proteins were selected for further evaluation in individual patients by independent immunoassays, and the up-regulation of transthyretin, zinc alpha-2-glycoprotein and immunoglobulin kappa light chain was validated in sera of relapsing-remitting (CIS and RRMScl) patients, when compared to healthy donors. To present significant expression differences in PPMScl, analysis with a larger patient population is required.

Isolation of myeloid dendritic cells and epithelial cells from human thymus.

In this protocol we provide a method to isolate dendritic cells (DC) and epithelial cells (TEC) from the human thymus. DC and TEC are the major antigen presenting cell (APC) types found in a normal thymus and it is well established that they play distinct roles during thymic selection. These cells are localized in distinct microenvironments in the thymus and each APC type makes up only a minor population of cells. To further understand the biology of these cell types, characterization of these cell populations is highly desirable but due to their low frequency, isolation of any of these cell types requires an efficient and reproducible procedure. This protocol details a method to obtain cells suitable for characterization of diverse cellular properties. Thymic tissue is mechanically disrupted and after different steps of enzymatic digestion, the resulting cell suspension is enriched using a Percoll density centrifugation step. For isolation of myeloid DC (CD11c(+)), cells from the low-density fraction (LDF) are immunoselected by magnetic cell sorting. Enrichment of TEC populations (mTEC, cTEC) is achieved by depletion of hematopoietic (CD45(hi)) cells from the low-density Percoll cell fraction allowing their subsequent isolation via fluorescence activated cell sorting (FACS) using specific cell markers. The isolated cells can be used for different downstream applications.

Suppression of experimental autoimmune encephalomyelitis by interleukin-10 transduced neural stem/progenitor cells.

Neural stem/progenitor cells (NSPCs) have the ability to migrate into the central nervous system (CNS) to replace damaged cells. In inflammatory CNS disease, cytokine transduced neural stem cells may be used as vehicles to specifically reduce inflammation and promote cell replacement. In this study, we used NSPCs overexpressing IL-10, an immunomodulatory cytokine, in an animal model for CNS inflammation and multiple sclerosis (MS). Intravenous injection of IL-10 transduced neural stem/progenitor cells (NSPC(IL-10)) suppressed myelin oligodendrocyte glycoprotein aa 35-55 (MOG35-55)- induced experimental autoimmune encephalomyelitis (EAE) and, following intravenous injection, NSPC(IL-10) migrated to peripheral lymphoid organs and into the CNS. NSPC(IL-10 )suppressed antigen-specific proliferation and proinflammatory cytokine production of lymph node cells obtained from MOG35-55 peptide immunized mice. In this model, IL-10 producing NSPCs act via a peripheral immunosuppressive effect to attenuate EAE.

Exploring the MHC-peptide matrix of central tolerance in the human thymus.

Ever since it was discovered that central tolerance to self is imposed on developing T cells in the thymus through their interaction with self-peptide major histocompatibility complexes on thymic antigen-presenting cells, immunologists have speculated about the nature of these peptides, particularly in humans. Here, to shed light on the so-far unknown human thymic peptide repertoire, we analyse peptides eluted from isolated thymic dendritic cells, dendritic cell-depleted antigen-presenting cells and whole thymus. Bioinformatic analysis of the 842 identified natural major histocompatibility complex I and II ligands reveals significant cross-talk between major histocompatibility complex-class I and II pathways and differences in source protein representation between individuals as well as different antigen-presenting cells. Furthermore, several autoimmune- and tumour-related peptides, from enolase and vimentin for example, are presented in the healthy thymus. 302 peptides are directly derived from negatively selecting dendritic cells, thus providing the first global view of the peptide matrix in the human thymus that imposes self-tolerance in vivo.

The different roles of the thymus in the pathogenesis of the various myasthenia gravis subtypes.

The thymus plays distinct roles in the pathogenesis of the different Myasthenia gravis (MG) subtypes. Inflammatory, neoplastic and age-related alterations of the thymus are of pivotal relevance for the initiation of anti-acetylcholine receptor (AChR) autoimmunity in early onset MG, thymoma-associated MG and, likely, late onset MG, respectively. By contrast, the thymus is presumably not related to MG that is due to autoantibodies to the muscle specific kinase, MuSK. Finally, the role of the thymus is still obscure in MG defined by antibodies against the agrin receptor LRP4 and in MG without all of the above autoantibdies (triple sero-negative MG) since these MG subtypes have been described only recently and thymectomy has not been their standard treatment. This review aims to give an update on intrathymic mechanisms of tolerance breakdown in MG, including abnormal T cell selection and activation, the role of thymic myoid cells, the autoimmune regulator (AIRE) and regulatory T cells.

Natural HLA class I ligands from glioblastoma: extending the options for immunotherapy.

Glioblastoma multiforme is the most frequent and most malignant primary brain tumor with poor prognosis despite surgical removal and radio-chemotherapy. In this setting, immunotherapeutical strategies have great potential, but the reported repertoire of tumor associated antigens is only for HLA-A 02 positive tumors. We describe the first analysis of HLA-peptide presentation patterns in HLA-A 02 negative glioma tissue combined with gene expression profiling of the tumor samples by oligonucleotide microarrays. We identified numerous candidate peptides for immunotherapy. These are peptides derived from proteins with a well-described role in glioma tumor biology and suitable gene expression profiles such as PTPRZ1, EGFR, SEC61G and TNC. Information obtained from complementary analyses of HLA-A 02 negative tumors not only contributes to the discovery of novel shared glioma antigens, but most importantly provides the opportunity to tailor a patient-individual cocktail of tumor-associated peptides for a personalized, targeted immunotherapeutic approach in HLA-A 02 negative patients.

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

OBJECTIVE: The objective of this study is to comprehensively define the genetic basis of early onset myasthenia gravis (EOMG). METHODS: 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. RESULTS: 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) ). INTERPRETATION: 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.

Contrasting disease patterns in seropositive and seronegative neuromyelitis optica: A multicentre study of 175 patients.

BACKGROUND: The diagnostic and pathophysiological relevance of antibodies to aquaporin-4 (AQP4-Ab) in patients with neuromyelitis optica spectrum disorders (NMOSD) has been intensively studied. However, little is known so far about the clinical impact of AQP4-Ab seropositivity. OBJECTIVE: To analyse systematically the clinical and paraclinical features associated with NMO spectrum disorders in Caucasians in a stratified fashion according to the patients' AQP4-Ab serostatus. METHODS: Retrospective study of 175 Caucasian patients (AQP4-Ab positive in 78.3%). RESULTS: Seropositive patients were found to be predominantly female (p < 0.0003), to more often have signs of co-existing autoimmunity (p < 0.00001), and to experience more severe clinical attacks. A visual acuity of ≤ 0.1 during acute optic neuritis (ON) attacks was more frequent among seropositives (p < 0.002). Similarly, motor symptoms were more common in seropositive patients, the median Medical Research Council scale (MRC) grade worse, and MRC grades ≤ 2 more frequent, in particular if patients met the 2006 revised criteria (p < 0.005, p < 0.006 and p < 0.01, respectively), the total spinal cord lesion load was higher (p < 0.006), and lesions ≥ 6 vertebral segments as well as entire spinal cord involvement more frequent (p < 0.003 and p < 0.043). By contrast, bilateral ON at onset was more common in seronegatives (p < 0.007), as was simultaneous ON and myelitis (p < 0.001); accordingly, the time to diagnosis of NMO was shorter in the seronegative group (p < 0.029). The course of disease was more often monophasic in seronegatives (p < 0.008). Seropositives and seronegatives did not differ significantly with regard to age at onset, time to relapse, annualized relapse rates, outcome from relapse (complete, partial, no recovery), annualized EDSS increase, mortality rate, supratentorial brain lesions, brainstem lesions, history of carcinoma, frequency of preceding infections, oligoclonal bands, or CSF pleocytosis. Both the time to relapse and the time to diagnosis was longer if the disease started with ON (p < 0.002 and p < 0.013). Motor symptoms or tetraparesis at first myelitis and > 1 myelitis attacks in the first year were identified as possible predictors of a worse outcome. CONCLUSION: This study provides an overview of the clinical and paraclinical features of NMOSD in Caucasians and demonstrates a number of distinct disease characteristics in seropositive and seronegative patients.

Anti-LRP4 autoantibodies in AChR- and MuSK-antibody-negative myasthenia gravis.

Myasthenia gravis (MG) is an autoimmune disorder characterized by a defect in synaptic transmission at the neuromuscular junction causing fluctuating muscle weakness with a decremental response to repetitive nerve stimulation or altered jitter in single-fiber electromyography (EMG). Approximately 80% of all myasthenia gravis patients have autoantibodies against the nicotinic acetylcholine receptor in their serum. Autoantibodies against the tyrosine kinase muscle-specific kinase (MuSK) are responsible for 5-10% of all myasthenia gravis cases. The autoimmune target in the remaining cases is unknown. Recently, low-density lipoprotein receptor-related protein (LRP4) has been identified as the agrin receptor. LRP4 interacts with agrin, and the binding of agrin activates MuSK, which leads to the formation of most if not all postsynaptic specializations, including aggregates containing acetylcholine receptors (AChRs) in the junctional plasma membrane. In the present study we tested if autoantibodies against LRP4 are detectable in patients with myasthenia gravis. To this end we analyzed 13 sera from patients with generalized myasthenia gravis but without antibodies against AChR or MuSK. The results showed that 12 out of 13 antisera from double-seronegative MG patients bound to proteins concentrated at the neuromuscular junction of adult mouse skeletal muscle and that approximately 50% of the tested sera specifically bound to HEK293 cells transfected with human LRP4. Moreover, 4 out of these 13 sera inhibited agrin-induced aggregation of AChRs in cultured myotubes by more than 50%, suggesting a pathogenic role regarding the dysfunction of the neuromuscular endplate. These results indicate that LRP4 is a novel target for autoantibodies and is a diagnostic marker in seronegative MG patients.

Serum and cerebrospinal fluid uric acid levels in lewy body disorders: associations with disease occurrence and amyloid-ß pathway.

Recent studies have provided evidence that uric acid (UA), a natural antioxidant, may play a role in the development and progression of Parkinson's disease (PD) and of dementia. In this clinical study we were therefore interested in the role of UA in Lewy body disorders (LBD), which includes Parkinson's disease (PD) and a common form of neurodegenerative dementias, dementia with Lewy bodies (DLB). Ninety-five LBD patients (55 non-demented PD patients, PDND; 20 PD patients with dementia, PDD; and 20 DLB patients) and 76 controls underwent clinical and biochemical analyses including, from a subcohort, cerebrospinal fluid (CSF) analyses, and analysis of three single nucleotide polymorphisms (SNPs) known to be associated with altered serum UA levels. We confirmed previous findings of lowered serum UA levels in LBD patients compared to controls. In CSF, UA levels were significantly higher in PDND patients (median 0.7 mg/dl) compared only to demented LBD patients (0.4 mg/dl; p = 0.03), but not to controls (0.5 mg/dl; p = 0.12). CSF UA levels correlated positively with CSF Aß42 levels. This correlation was highest in controls (ρ = 0.67), intermediate in PDND (ρ = 0.49), but not observable in demented LBD patients (ρ = 0.10). These findings suggest an involvement of serum UA in LBD occurrence, and an involvement of CSF UA in cognitive decline in LBD, possibly through the Aß pathway. SNP rs1165205 (SLC17A3) was weakly associated with altered CSF UA levels. Taken together, our results provide first evidence for disease-relevant but potentially distinct roles of UA in the blood and CSF compartment, respectively, in LBD.