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Objectives: To identify dietary and lifestyle variables that may affect cognitive function in the elderly. Design: Population-based prospective cohort study. Setting: General community residing in Athens and the surrounding Attica region of Greece.

Myasthenia gravis (MG) is a chronic autoimmune disorder characterized by muscle weakness and caused by pathogenic autoantibodies that bind to membrane proteins at the neuromuscular junction. Most patients have autoantibodies against the acetylcholine receptor (AChR), but a subset of patients have autoantibodies against muscle-specific tyrosine kinase (MuSK) instead. MuSK is an essential component of the pathway responsible for synaptic differentiation, which is activated by nerve-released agrin. Through binding MuSK, serum-derived autoantibodies inhibit agrin-induced MuSK autophosphorylation, impair clustering of AChRs, and block neuromuscular transmission. We sought to establish individual MuSK autoantibody clones so that the autoimmune mechanisms could be better understood. We isolated MuSK autoantibody-expressing B cells from 6 MuSK MG patients using a fluorescently tagged MuSK antigen multimer, then generated a panel of human monoclonal autoantibodies (mAbs) from these cells. Here we focused on 3 highly specific mAbs that bound quantitatively to MuSK in solution, to MuSK-expressing HEK cells, and at mouse neuromuscular junctions, where they colocalized with AChRs. These 3 IgG isotype mAbs (2 IgG4 and 1 IgG3 subclass) recognized the Ig-like domain 2 of MuSK. The mAbs inhibited AChR clustering, but intriguingly, they enhanced rather than inhibited MuSK phosphorylation, which suggests an alternative mechanism for inhibiting AChR clustering.

Myasthenia gravis (MG) is a prototypical B cell-mediated autoimmune disease affecting 20–50 per 100,000 people. The majority of patients fall into two clinically distinguishable types based on whether they produce autoantibodies targeting the acetylcholine receptor (AChR-MG) or muscle specific kinase (MuSK-MG). The autoantibodies are pathogenic, but whether their generation is associated with broader defects in the B cell repertoire is unknown. To address this question, we performed deep sequencing of the B cell receptor repertoire of AChR-MG, MuSK-MG and healthy subjects to generate approximately 518,000 unique VH and VL sequences from sorted naïve and memory B cell populations. AChR-MG and MuSK-MG subjects displayed distinct gene segment usage biases in both VH and VL sequences within the naïve and memory compartments. The memory compartment of AChR-MG was further characterized by reduced positive selection of somatic mutations in the H-CDR regions and altered H-CDR3 physicochemical properties. The VL repertoire of MuSK-MG was specifically characterized by reduced V/J segment distance in recombined sequences, suggesting diminished VL receptor editing during B cell development. Our results identify large-scale abnormalities in both the naïve and memory B cell repertoires. Particular abnormalities were unique to either AChR-MG or MuSK-MG indicating that the repertoires reflect the distinct properties of the subtypes. These repertoire abnormalities are consistent with previously observed defects in B cell tolerance checkpoints in MG, thereby offering additional insight regarding the impact of tolerance defects on peripheral autoimmune repertoires. These collective findings point toward a deformed B cell repertoire as a fundamental component of MG.

Identification of dietary and lifestyle variables associated with the development of Parkinson's disease (PD) may offer pathogenetic clues and prevention opportunities. In a population-based prospective cohort study, 26,173 participants in the EPIC-Greece cohort had sociodemographic, anthropometric, medical, dietary and lifestyle variables ascertained at enrolment and periodically reassessed with follow-up contacts. Based on these data, subjects were screened as possible PD cases if they (1) reported either a medical diagnosis of PD or use of anti-PD drugs and (2) did not report preceding causes of secondary parkinsonism. For diagnostic validation, possible incident PD cases were assessed by a focused 3-item telephone questionnaire. Cox proportional hazards regression was used to evaluate associations between potential predictors and incident PD. The main multivariate model included gender, age, marital status, schooling years, farming occupation, smoking status, caffeinated coffee, body mass index, physical activity and energy intake. Additional models included all above variables plus one dietary item at a time. Incidence rate adjusted to the European population was 16.9 per 100,000 person-years. In multivariate models, incident PD exhibited strong positive association with consumption of milk, but not cheese or yoghurt. This finding may help narrow down the search for potential dairy product components with a facilitatory role in PD. Concerning other dietary components, inverse association was found between polyunsaturated fat intake and incident PD. Also, inverse association was found with tobacco smoking, in line with previous studies, but not with caffeine.

Mounting evidence suggests that autoantibodies contribute to the pathogenesis of demyelination in the PNS and CNS. Rapid reversal of electrophysiological blockade after plasmapheresis or intravenous immunoglobulin treatment for acute or chronic inflammatory demyelinating polyneuropathy is more likely to result from removal or neutralization of an antibody that impairs saltatory conduction than from remyelination. Although up to 30% of patients with acute or chronic inflammatory demyelinating polyneuropathy harbour autoantibodies, specific antigens have been identified in no more than 13% of cases. To date, autoantigens identified at the node of Ranvier include neurofascin 186, gliomedin and possibly moesin in the nodal domain, and contactin-1, Caspr1 and neurofascin 155 in the paranodal domain. In some patients with multiple sclerosis, paranodal CNPase and juxtaparanodal contactin-2 trigger a humoral response. This Review explores the molecular anatomy of the node of Ranvier, focusing on proteins with extracellular domains that could serve as antigens. The clinical implications of node-specific antibody responses are addressed, and the best approaches to identify antibodies that target nodal proteins are highlighted. Also discussed are the roles of these antibodies as either secondary, disease-exacerbating responses, or as a primary effector mechanism that defines demyelination or axonal degeneration at the node, identifies disease subtypes or determines response to treatments.

IMPORTANCE Myasthenia gravis (MG), an autoimmune disorder of neuromuscular transmission, is treated by an array of immunotherapeutics, many of which are nonspecific. Even with current therapies, a subset of patients has medically refractory MG. The benefits of B-cell-targeted therapy with rituximab have been observed in MG; however, the duration of these benefits after treatment is unclear. OBJECTIVE To evaluate the durability of response to rituximab in the treatment of acetylcholine receptor autoantibody-positive (AChR+) generalized MG. DESIGN, SETTING AND PARTICIPANTS This retrospective case series study included 16 patients with AChR+ MG referred to an MG clinic from January 1, 2007, to December 31, 2015. The patients were treated with rituximab and followed up for 18 to 84 months after treatment. MAIN OUTCOMES AND MEASURES Assessment of long-term clinical response, durability of response and/or relapse rate, AChR autoantibody levels, adverse effects, and inflammatory markers. RESULTS In the 16 patients (6 men and 10 women; median age, 42 [range, 18-69] years), clinical improvement was observed in parallel with complete withdrawal or reduction of other immunotherapies, with all patients achieving complete stable remission, pharmacologic remission, or minimal manifestations based on the Myasthenia Gravis Foundation of America postintervention status criteria. Nine patients (56%) had a relapse during a mean follow-up of 36 (range, 24-47) months. Seven patients (44%) remained relapse free with a mean follow-up of 47 (range, 18-81) months since the last rituximab treatment. All values were normalized to a pretreatment anti-AChR antibody level of 100% and the mean levels after each rituximab cycle were calculated. A 33% decrease was seen after cycle 1 of rituximab treatment (100% vs 67%; P = .004); 20% after cycle 2 (compared with cycle 1) (67% vs 47%; P = .008); and 17% after cycle 3 (compared with cycle 2) (47% vs 30%; P = .02). However, the serum cytokine levels measured were found to be unchanged. CONCLUSIONS AND RELEVANCE Rituximab therapy appears to be an effective option in patients with refractory AChR+ MG, who were observed to have a durable response after treatment. Identification of markers of disease relapse and sustained remission are critical next steps in the development of pathophysiology-relevant, evidence-based practice parameters for rituximab in the treatment of MG.

Myasthenia gravis (MG) is an archetypal autoimmune disease. The pathology is characterized by autoantibodies to the acetylcholine receptor (AChR) in most patients or to muscle-specific tyrosine kinase (MuSK) in others and to a growing number of other postsynaptic proteins in smaller subsets. A decrease in the number of functional AChRs or functional interruption of the AChR within the muscle end plate of the neuromuscular junction is caused by pathogenic autoantibodies. Although the molecular immunology underpinning the pathology is well understood, much remains to be learned about the cellular immunology contributing to the production of autoantibodies. This Review documents research concerning the immunopathology of MG, bringing together evidence principally from human studies with an emphasis on the role of adaptive immunity and B cells in particular. Proposed mechanisms for autoimmunity, which take into account that different types of MG may incorporate divergent immunopathology, are offered. Muscle Nerve 57: 172-184, 2018.