Do neuronal autoantibodies cause psychosis? A neuroimmunological perspective

Integrating Clinical Neuropsychology and Psychotic Spectrum Disorders: A Systematic Analysis of Cognitive Dynamics, Interventions, and Underlying Mechanisms

Background and Objectives: The study aims to provide a comprehensive neuropsychological analysis of psychotic spectrum disorders, including schizophrenia, bipolar disorder, and depression. It focuses on the critical aspects of cognitive impairments, diagnostic tools, intervention efficacy, and the roles of genetic and environmental factors in these disorders. The paper emphasizes the diagnostic significance of neuropsychological tests in identifying cognitive deficiencies and their predictive value in the early management of psychosis. Materials and Methods: The study involved a systematic literature review following the PRISMA guidelines. The search was conducted in significant databases like Scopus, PsycINFO, PubMed, and Web of Science using keywords relevant to clinical neuropsychology and psychotic spectrum disorders. The inclusion criteria required articles to be in English, published between 2018 and 2023, and pertinent to clinical neuropsychology's application in these disorders. A total of 153 articles were identified, with 44 ultimately included for detailed analysis based on relevance and publication status after screening. Results: The review highlights several key findings, including the diagnostic and prognostic significance of mismatch negativity, neuroprogressive trajectories, cortical thinning in familial high-risk individuals, and distinct illness trajectories within psychosis subgroups. The studies evaluated underline the role of neuropsychological tests in diagnosing psychiatric disorders and emphasize early detection and the effectiveness of intervention strategies based on cognitive and neurobiological markers. Conclusions: The systematic review underscores the importance of investigating the neuropsychological components of psychotic spectrum disorders. It identifies significant cognitive impairments in attention, memory, and executive function, correlating with structural and functional brain abnormalities. The paper stresses the need for precise diagnoses and personalized treatment modalities, highlighting the complex interplay between genetic, environmental, and psychosocial factors. It calls for a deeper understanding of these neuropsychological processes to enhance diagnostic accuracy and therapeutic outcomes.

Cerebrospinal Fluid Homer-3 Autoantibodies in a Patient with Amnestic Mild Cognitive Impairment

(1) Background: Homer-3 antibodies are associated with cerebellar disease ranging from subacute degeneration to cerebellitis. However, cognitive impairment associated with Homer-3 autoantibodies has not been reported until now. (2) Methods: in retrospect, we systematically studied clinical, cranial magnetic resonance imaging (cMRI), electroencephalography (EEG) and lumbar puncture data, including neural autoantibodies of a clinical case. (3) Results: we describe the case of a 56-year-old woman presenting with amnestic mild cognitive impairment in association with serum and CSF detection of Homer-3 autoantibodies and a depressive syndrome. cMRI revealed cerebellar atrophy. CSF analysis showed elevated ptau181 protein. Applying the criteria for an autoimmune psychiatric syndrome revealed a plausible autoimmune basis for the mild cognitive impairment. (4) Discussions: our case report demonstrates an amnestic mild cognitive impairment and depressive symptoms associated with Homer-3 autoantibodies as a novel feature of Homer-3 antibody-related disease. We also propose that cognitive dysfunction might result from impaired AMPAR signaling in the hippocampus induced by Homer-3 antibodies, which will have to be verified in further research.

Niacin skin flush and membrane polyunsaturated fatty acids in schizophrenia from the acute state to partial remission: a dynamic relationship

Despite the consistent finding of an attenuated niacin-induced flush response in schizophrenia, its long-term stability and relationship to the membrane polyunsaturated fatty acid (PUFA) levels remain unknown. We conducted niacin skin tests and measured the membrane PUFAs using gas chromatography among 46 schizophrenia inpatients and 37 healthy controls at the baseline and the 2-month follow-up. Attenuated flush responses were persistently observed in schizophrenia patients in both acute and partial remission states, whereas an increased flush response was found in the controls. A persistent decrease in both dihomo-gamma-linolenic acid and docosahexaenoic acid and an increased turnover of arachidonic acid (ARA) via endogenous biosynthesis were found in schizophrenia patients. A composite niacin flush score by combining those with a control-to-case ratio of >1.4 (i.e., scores at 5 min of 0.1 M, 0.01 M, and 0.001 M + 10 min of 0.01 M and 0.001 M + 15 min of 0.001 M) at the baseline was correlated positively with ARA levels among controls but not among schizophrenia patients, whereas the flush score at the 2-month follow-up was correlated positively with ARA levels among patients. The 2-month persistence of attenuated niacin-induced flush response in schizophrenia patients implies that the niacin skin test might tap a long-term vulnerability to schizophrenia beyond acute exacerbation.

The Challenge of Assessing Mild Neuroinflammation in Severe Mental Disorders

Recent psychoneuroimmunology research has provided new insight into the etiology and pathogenesis of severe mental disorders (SMDs). The mild encephalitis (ME) hypothesis was developed with the example of human Borna disease virus infection years ago and proposed, that a subgroup SMD patients, mainly from the broad schizophrenic and affective spectrum, could suffer from mild neuroinflammation, which remained undetected because hard to diagnose with available diagnostic methods. Recently, in neurology an emerging new subgroup of autoimmune encephalitis (AE) cases suffering from various neurological syndromes was described in context with the discovery of an emerging list of Central Nervous System (CNS) autoantibodies. Similarly in psychiatry, consensus criteria of autoimmune psychosis (AP) were developed for patients presenting with CNS autoantibodies together with isolated psychiatric symptoms and paraclinical findings of (mild) neuroinflammation, which in fact match also the previously proposed ME criteria. Nevertheless, identifying mild neuroinflammation in vivo in the individual SMD case remains still a major clinical challenge and the possibility that further cases of ME remain still under diagnosed appears an plausible possibility. In this paper a critical review of recent developments and remaining challenges in the research and clinical diagnosis of mild neuroinflammation in SMDs and in general and in transdisciplinary perspective to psycho-neuro-immunology and neuropsychiatry is given. Present nosological classifications of neuroinflammatory disorders are reconsidered with regard to findings from experimental and clinical research. A refined grading list of clinical states including "classical" encephalitis, AE, AP/ME,and newly proposed terms like parainflammation, stress-induced parainflammation and neuroprogression, and their respective relation to neurodegeneration is presented, which may be useful for further research on the possible causative role of mild neuroinflammation in SMDs. Beyond, an etiology-focused subclassification of ME subtypes, like autoimmune ME or infectious ME, appears to be required for differential diagnosis and individualized treatment. The present status of the clinical diagnosis of mild neuroinflammatory mechanisms involved in SMDs is outlined with the example of actual diagnosis and therapy in AP. Ideas for future research to unravel the contribution of mild neuroinflammation in the causality of SMDs and the difficulties expected to come to novel immune modulatory, anti-infectious or anti-inflammatory therapeutic principles in the sense of precision medicine are discussed.

Schizophrenia and Influenza at the Centenary of the 1918-1919 Spanish Influenza Pandemic: Mechanisms of Psychosis Risk

Associations between influenza infection and psychosis have been reported since the eighteenth century, with acute "psychoses of influenza" documented during multiple pandemics. In the late 20th century, reports of a season-of-birth effect in schizophrenia were supported by large-scale ecological and sero-epidemiological studies suggesting that maternal influenza infection increases the risk of psychosis in offspring. We examine the evidence for the association between influenza infection and schizophrenia risk, before reviewing possible mechanisms via which this risk may be conferred. Maternal immune activation models implicate placental dysfunction, disruption of cytokine networks, and subsequent microglial activation as potentially important pathogenic processes. More recent neuroimmunological advances focusing on neuronal autoimmunity following infection provide the basis for a model of infection-induced psychosis, potentially implicating autoimmunity to schizophrenia-relevant protein targets including the N-methyl-D-aspartate receptor. Finally, we outline areas for future research and relevant experimental approaches and consider whether the current evidence provides a basis for the rational development of strategies to prevent schizophrenia.

Autoimmune encephalitis as a differential diagnosis of schizophreniform psychosis: clinical symptomatology, pathophysiology, diagnostic approach, and therapeutic considerations

Primary schizophreniform psychoses are thought to be caused by complex gene-environment interactions. Secondary forms are based on a clearly identifiable organic cause, in terms of either an etiological or a relevant pathogenetic factor. The secondary or "symptomatic" forms of psychosis have reentered the focus stimulated by the discovery of autoantibody (Ab)-associated autoimmune encephalitides (AEs), such as anti-NMDA-R encephalitis, which can at least initially mimic variants of primary psychosis. These newly described secondary, immune-mediated schizophreniform psychoses typically present with the acute onset of polymorphic psychotic symptoms. Over the course of the disease, other neurological phenomena, such as epileptic seizures, movement disorders, or reduced levels of consciousness, usually arise. Typical clinical signs for AEs are the acute onset of paranoid hallucinatory symptoms, atypical polymorphic presentation, psychotic episodes in the context of previous AE, and additional neurological and medical symptoms such as catatonia, seizure, dyskinesia, and autonomic instability. Predominant psychotic courses of AEs have also been described casuistically. The term autoimmune psychosis (AP) was recently suggested for these patients. Paraclinical alterations that can be observed in patients with AE/AP are inflammatory cerebrospinal fluid (CSF) pathologies, focal or generalized electroencephalographic slowing or epileptic activity, and/or suspicious "encephalitic" imaging findings. The antibody analyses in these patients include the testing of the most frequently found Abs against cell surface antigens (NMDA-R, CASPR2, LGI1, AMPA-R, GABA_B-R), intracellular antigens (Hu, Ri, Yo, CV2/CRMP5, Ma2 [Ta], amphiphysin, GAD65), thyroid antigens (TG, TPO), and antinuclear Abs (ANA). Less frequent antineuronal Abs (e.g., against DPPX, GABA_A-R, glycine-R, IgLON5) can be investigated in the second step when first step screening is negative and/or some specific clinical factors prevail. Beyond, tissue-based assays on brain slices of rodents may detect previously unknown antineuronal Abs in some cases. The detection of clinical and/or paraclinical pathologies (e.g., pleocytosis in CSF) in combination with antineuronal Abs and the exclusion of alternative causes may lead to the diagnosis of AE/AP and enable more causal therapeutic immunomodulatory opportunities.

The immunobiology of autoimmune encephalitides

Autoimmune encephalitides, with an estimated incidence of 1.5 per million population per year, although described only 15 years ago, have already had a remarkable impact in neurology and paved the field to autoimmune neuropsychiatry. Many patients traditionally presented with aberrant behavior, especially of acute or subacute onset, and treated with anti-psychotic therapies, turn out to have a CNS autoimmune disease with pathogenic autoantibodies against synaptic antigens responding to immunotherapies. The review describes the clinical spectrum of these disorders, and the pathogenetic role of key autoantibodies directed against: a) cell surface synaptic antigens and receptors, including NMDAR, GABAa, GABAb, AMPA and glycine receptors; b) channels such as AQP4 water-permeable channel or voltage-gated potassium channels; c) proteins that stabilize voltage-gated potassium channel complex into the membrane, like the LGI1 and CASPR2; and d) enzymes that catalyze the formation of neurotransmitters such as Glutamic Acid Decarboxylase (GAD). These antibodies, effectively target excitatory or inhibitory synapses in the limbic system, basal ganglia or brainstem altering synaptic function and resulting in uncontrolled neurological excitability disorder clinically manifested with psychosis, agitation, behavioral alterations, depression, sleep disturbances, seizure-like phenomena, movement disorders such as ataxia, chorea and dystonia, memory changes or coma. Some of the identified triggering factors include: viruses, especially herpes simplex, accounting for the majority of relapses occurring after viral encephalitis, which respond to immunotherapy rather than antiviral agents; tumors especially teratoma, SCLC and thymomas; and biological cancer therapies (immune-check-point inhibitors). As anti-synaptic antibodies persist after viral infections or tumor removal, augmentation of autoreactive B cells which release autoantigens to draining lymph nodes, molecular mimicry and infection-induced bystander immune activation products play a role in autoimmunization process or perpetuating autoimmune neuroinflammation. The review stresses the importance of early detection, clinical recognition, proper antibody testing and early therapy initiation as these disorders, regardless of a known or not trigger, are potentially treatable responding to systemic immunotherapy with intravenous steroids, IVIg, rituximab or even bortezomid.

B-cells and schizophrenia: A promising link or a finding lost in translation?

Recent genetic studies have suggested a potential role for B-cells in the pathogenesis of schizophrenia. Greater insight in the functioning of B-cells in patients with schizophrenia is therefore of importance. In this narrative review we aim to give an overview of the current literature on B-cells and schizophrenia. We found no evidence for altered numbers of these cells in blood. We did find support for increased levels of B-cell related cytokines and certain autoantibodies. Studies on B-cell development and function, or their numbers in cerebrospinal fluid or brain tissue are very limited. Based on the available data we appraise whether various B-cell mediated pathological mechanisms are likely to play a role in schizophrenia and provide directions for future research.

Autoantibodies against N-methyl-d-aspartate receptor 1 in health and disease

Purpose of review

Humoral autoimmunity has gained highest interest in neurology and psychiatry. Despite numerous recent articles on this hot topic, however, the biological significance of natural autoantibodies (AB) and the normal autoimmune repertoire of mammals remained quite obscure. AB may contribute to disorder-relevant phenotypes and are even believed to induce diseases themselves, but the circumstances under which AB become pathogenic are not fully understood. This review will focus on the highly frequent AB against the N-methyl-d-aspartate receptor 1 (NMDAR1-AB) as an illustrating example and provide a critical overview of current work (please note that the new nomenclature, GluN1, is disregarded here for consistency with the AB literature). In particular, it will demonstrate how little is known at this point and how many conclusions are drawn based on small numbers of individuals, fragmentary experimental approaches or missing controls.

Recent findings

NMDAR1-AB were investigated by clinicians world-wide with numerous small studies and case reports appearing yearly. Many publications were on ‘anti-NMDAR encephalitis’ cases or tried to separate those from other NMDAR1-AB associated conditions. Original exclusivity claims (e.g. electroencephalogram, EEG or functional magnetic resonance imaging, fMRI findings) turned out not to be exclusive for ‘anti-NMDAR encephalitis’. Systematic analyses of representative NMDAR1-AB positive sera of all immunoglobulin (Ig) classes showed comparable distribution of different epitopes, often polyspecific/polyclonal, across health and disease. Sophisticated imaging tools provided findings on synapse trafficking changes induced by NMDAR1-AB from psychotic subjects but still lack epitope data to support any claimed disorder link. Persistently high titers of NMDAR1-AB (IgG) in immunized mice with open blood–brain barrier (BBB)-induced psychosis-like symptoms but failed to induce inflammation in the brain. Knowledge on peripheral NMDAR, for example in the immune system, and on potential inducers of NMDAR1-AB is only slowly increasing.

Summary

The present knowledge on the (patho) physiological role of NMDAR1-AB is very limited and still characterized by adamant rumors. Much more experimental work and more solid and informative clinical reports, including large numbers of subjects and adequate control groups, follow-up investigations and interdisciplinary approaches will be necessary to obtain a better understanding of the significance of humoral autoimmunity in general (in focus here: NMDAR1-AB) and its disease-relevance in particular.

Human Autoantibodies Against N-Methyl-D-Aspartate Receptor Modestly Alter Dopamine D1 Receptor Surface Dynamics

Circulating autoantibodies directed against extracellular domains of the glutamatergic N-methyl-D-aspartate receptors (NMDAR-Ab) elicit psychotic symptoms in humans and behavioral deficits in animal models. Recent advances suggest that NMDAR-Ab exert their pathogenic action by altering the trafficking of NMDAR, which results in a synaptic NMDAR hypofunction consistent with the consensual glutamatergic hypothesis of psychotic disorders. Yet, dysfunction in the dopaminergic signaling is also proposed to be at the core of psychotic disorders. Since NMDAR and dopamine D1 receptors (D1R) form membrane signaling complexes, we investigated whether NMDAR-Ab purified from patients with NMDAR-encephalitis or schizophrenia impaired D1R surface dynamics. As previous data demonstrated that NMDAR-Ab, at least from NMDAR-encephalitis patients, mainly bind to hippocampal NMDAR, we used single nanoparticle imaging to track D1R specifically at the surface of hippocampal neurons that were exposed to either purified G type immunoglobulins (IgGs) from NMDAR-Ab seropositive patients suffering from NMDAR-encephalitis or schizophrenia, or control IgGs from healthy NMDAR-Ab seropositive or seronegative subjects. We report that overnight incubation with NMDAR-Ab from patients, but not from healthy carriers, decreased the surface dynamics of D1R compared with NMDAR-Ab seronegative IgGs. This decrease was abolished, and even reversed, in D1R mutant that cannot physically interact with NMDAR. Overall, our data indicate that NMDAR-Ab from patients with psychotic symptoms alter the trafficking of D1R, likely through the surface crosstalk between NMDAR and D1R.

Uncoupling the widespread occurrence of anti-NMDAR1 autoantibodies from neuropsychiatric disease in a novel autoimmune model

Autoantibodies of the IgG class against N-methyl-D-aspartate-receptor subunit-NR1 (NMDAR1-AB) were considered pathognomonic for anti-NMDAR encephalitis. This view has been challenged by the age-dependent seroprevalence (up to >20%) of functional NMDAR1-AB of all immunoglobulin classes found in >5000 individuals, healthy or affected by different diseases. These findings question a merely encephalitogenic role of NMDAR1-AB. Here, we show that NMDAR1-AB belong to the normal autoimmune repertoire of dogs, cats, rats, mice, baboons, and rhesus macaques, and are functional in the NMDAR1 internalization assay based on human IPSC-derived cortical neurons. The age dependence of seroprevalence is lost in nonhuman primates in captivity and in human migrants, raising the intriguing possibility that chronic life stress may be related to NMDAR1-AB formation, predominantly of the IgA class. Active immunization of ApoE^-/- and ApoE^+/+ mice against four peptides of the extracellular NMDAR1 domain or ovalbumin (control) leads to high circulating levels of specific AB. After 4 weeks, the endogenously formed NMDAR1-AB (IgG) induce psychosis-like symptoms upon MK-801 challenge in ApoE^-/- mice, characterized by an open blood-brain barrier, but not in their ApoE^+/+ littermates, which are indistinguishable from ovalbumin controls. Importantly, NMDAR1-AB do not induce any sign of inflammation in the brain. Immunohistochemical staining for microglial activation markers and T lymphocytes in the hippocampus yields comparable results in ApoE^-/- and ApoE^+/+ mice, irrespective of immunization against NMDAR1 or ovalbumin. These data suggest that NMDAR1-AB of the IgG class shape behavioral phenotypes upon access to the brain but do not cause brain inflammation on their own.

Brain-relevant antibodies in first-episode psychosis: a matched case-control study

BACKGROUND

There has been much recent excitement about the possibility that some cases of psychosis may be wholly due to brain-reactive antibodies, with antibodies to N-methyl-D-aspartate receptor (NMDAR) and the voltage-gated potassium channel (VGKC)-complex reported in a few patients with first-episode psychosis (FEP).

METHODS

Participants were recruited from psychiatric services in South London, UK, from 2009 to 2011 as part of the Genetics and Psychosis study. We conducted a case-control study to examine NMDAR and VGKC-complex antibody levels and rates of antibody positivity in 96 patients presenting with FEP and 98 controls matched for age and sex. Leucine-rich glioma inactiviated-1 (LGI1) and contactin-associated protein (CASPR) antibodies were also measured. Notably, patients with suspicion of organic disease were excluded.

RESULTS

VGKC-complex antibodies were found in both cases (n = 3) and controls (n = 2). NMDAR antibody positivity was seen in one case and one control. Either LGI1-Abs or CASPR2-Abs were found in three cases and three controls. Neuronal antibody staining, consistent with the above results or indicating potential novel antigens, was overall positive in four patients but also in six controls. Overall, antibody positivity was at low levels only and not higher in cases than in controls.

CONCLUSIONS

This case-control study of the prevalence of antibodies in FEP does not provide evidence to support the hypothesis that FEP is associated with an immune-mediated process in a subgroup of patients. Nevertheless, as other bio-clinical factors may influence the effect of such antibodies in a given individual, and patients with organic neurological disease may be misdiagnosed as FEP, the field requires more research to put these findings in context.

Pathogenicity of Antibodies against NMDA Receptor: Molecular Insights into Autoimmune Psychosis

Recent years have seen a flourishing literature on detection of circulating autoantibodies against neurotransmitter receptors in patients with neuropsychiatric disorders. These studies have generated hope for a better understanding of the underlying molecular dysfunctions and for appropriate therapeutic strategies. However, the detection of these autoantibodies in healthy subjects, and the lack of mechanistic insights have fostered debate about the pathogenic role of such autoantibodies. Here, we specifically discuss the biological evidence linking autoantibodies directed against the glutamatergic N-methyl-d-aspartate (NMDA) receptor (NMDAR-Abs) and psychosis, emphasising recent single-molecule imaging investigations that unveiled the impaired surface trafficking of NMDAR in the presence of NMDAR-Abs from psychotic patients. Although still in its infancy, the hypothesis that NMDAR-Abs from patients with psychosis play a pathogenic role is thus gaining support, opening avenues of fundamental and translational investigations.

Encephalitis, Mild Encephalitis, Neuroprogression, or Encephalopathy-Not Merely a Question of Terminology

Background: Psychoneuroimmunology research has presented emerging evidence of the involvement of inflammatory and immune mechanisms in the pathogenesis of severe mental disorders. In this context, new terms with increasing clinical relevance have been proposed, challenging the existing terms, and requiring consensus definitions of the new ones. Method: From a perspective of longstanding personal involvement in clinical settings and research in psychoneuroimmunology, the new and the existing terms are critically reconsidered. Results: Meningoencephalitis and encephalitis are comparably well defined clinical terms in neuropsychiatry, although in the individual case approach diagnosis can be difficult, for example in some cases of encephalitis that are described with normal cerebrospinal fluid findings, or often in chronic encephalitis. Encephalopathy is also a widely accepted term, however, with a surprisingly broad meaning with regard to the assigned underlying pathophysiology, ranging from one-hit traumatic encephalopathy to inflammatory encephalopathy, the latter term addressing a type of brain dysfunction secondary to acute systemic inflammation without proven brain autochthonus inflammation (neuroinflammation). However, this latter assumption and term may be wrong as neuroinflammation is difficult to prove in vivo. With emerging insights into prevailing inflammatory and neuroinflammatory mechanisms that are involved in the pathogenesis of severe mental disorders, the interdependent aspects of sensitive assessment and potential clinical relevance of mild neuroinflammation are becoming more apparent and of increasing clinical interest. The new terms "mild encephalitis," "parainflammation," and "neuroprogression" show considerable overlap in addition to gaps and hardly defined borders. However, details are hard to discuss as available studies use many biomarkers, but most of these are done without an established categorical attribution to exclusive terms. Most important, the three new concepts (neruoprogression, parainflammation, and mild encephalitis) are not mutually exclusive, even at the individual case level, and therefore will require state-related individual assessment approaches beyond large confirmatory studies. Conclusion: The newly proposed terms of mild encephalitis, parainflammation, and neuroprogression have an emerging clinical relevance, but respective borders, gaps and overlap in between them remain unclear, and these concepts may even be seen as complementary. Categorical delineation of the new and reconsideration of the existing terms with respect to individualized psychiatric treatment is required for better clinical use, eventually requiring a consensus approach. Here, a critique based on available data and a focus on clinical perspective was outlined, which may help to enhance fruitful discussion. The idea followed here is in line with pillar number six as proposed for the Research Diagnostic Domains, i.e., to provide and follow new concepts in psychiatric research.

The blood-brain barrier in psychosis

Blood-brain barrier pathology is recognised as a central factor in the development of many neurological disorders, but much less is known about the role of the blood-brain barrier in psychiatric disorders. We review post-mortem, serum-biomarker, CSF-biomarker, and neuroimaging studies that have examined blood-brain barrier structure and function in schizophrenia and related psychoses. We consider how blood-brain barrier dysfunction could relate to glutamatergic and inflammatory abnormalities, which are increasingly understood to play a part in the pathogenesis of psychosis. Mechanisms by which the blood-brain barrier and its associated solute transporters moderate CNS availability of antipsychotic drugs are summarised. We conclude that the complex nature of blood-brain barrier dysfunction in psychosis might be relevant to many aspects of disrupted neuronal and synaptic function, increased permeability to inflammatory molecules, disrupted glutamate homoeostasis, impaired action of antipsychotics, and development of antipsychotic resistance. Future research should address the longitudinal course of blood-brain barrier alterations in psychosis, to determine whether blood-brain barrier dysfunction is a cause or consequence of the pathology associated with the disorder.

All naturally occurring autoantibodies against the NMDA receptor subunit NR1 have pathogenic potential irrespective of epitope and immunoglobulin class

Autoantibodies of the IgG class against N-methyl-d-aspartate-receptor subunit NR1 (NMDAR1) were first described in anti-NMDAR encephalitis and seen as disease indicators. Recent work on together over 5000 individuals challenged this exclusive view by showing age-dependently up to >20% NMDAR1-autoantibody seroprevalence with comparable immunoglobulin class and titer distribution across health and disease. The key question therefore is to understand the properties of these autoantibodies, also in healthy carriers, in order to assess secondary complications and possible contributions to neuropsychiatric disease. Here, we believe we provide for human NMDAR1-autoantibodies the first comprehensive analysis of their target epitopes and functionality. We selected sera of representative carriers, healthy or diagnosed with very diverse conditions, that is, schizophrenia, age-related disorders like hypertension and diabetes, or anti-NMDAR encephalitis. We show that all positive sera investigated, regardless of source (ill or healthy donor) and immunoglobulin class, provoked NMDAR1 internalization in human-induced pluripotent stem cell-derived neurons and reduction of glutamate-evoked currents in NR1-1b/NR2A-expressing Xenopus oocytes. They displayed frequently polyclonal/polyspecific epitope recognition in the extracellular or intracellular NMDAR1 domains and some additionally in NR2A. We conclude that all circulating NMDAR1-autoantibodies have pathogenic potential regarding the whole spectrum of neuronal NMDAR-mediated effects upon access to the brain in situations of increased blood-brain-barrier permeability.

Dynamic disorganization of synaptic NMDA receptors triggered by autoantibodies from psychotic patients

The identification of circulating autoantibodies against neuronal receptors in neuropsychiatric disorders has fostered new conceptual and clinical frameworks. However, detection reliability, putative presence in different diseases and in health have raised questions about potential pathogenic mechanism mediated by autoantibodies. Using a combination of single molecule-based imaging approaches, we here ascertain the presence of circulating autoantibodies against glutamate NMDA receptor (NMDAR-Ab) in about 20% of psychotic patients diagnosed with schizophrenia and very few healthy subjects. NMDAR-Ab from patients and healthy subjects do not compete for binding on native receptor. Strikingly, NMDAR-Ab from patients, but not from healthy subjects, specifically alter the surface dynamics and nanoscale organization of synaptic NMDAR and its anchoring partner the EphrinB2 receptor in heterologous cells, cultured neurons and in mouse brain. Functionally, only patients’ NMDAR-Ab prevent long-term potentiation at glutamatergic synapses, while leaving NMDAR-mediated calcium influx intact. We unveil that NMDAR-Ab from psychotic patients alter NMDAR synaptic transmission, supporting a pathogenically relevant role.

Autoantibodies are found in neuropsychiatric conditions but without clear cellular mechanism and disease relevance. This study shows higher prevalence of autoantibodies against NMDAR receptors in schizophrenia patients, and patient-associated antibody can alter synaptic receptor trafficking and plasticity.

Voltage-gated Potassium Channel Antibody Autoimmune Encephalopathy Presenting With Isolated Psychosis in an Adolescent

Antibody-mediated encephalopathies associated with serum or cerebrospinal fluid antibodies directed against neuronal structures may present with a multitude of neuropsychiatric syndromes. Although some of the antibody-driven conditions are now well recognized in adults (eg, N-methyl-D-aspartate receptor antibody encephalitis), the spectrum of neuropsychiatric manifestations in the pediatric population is less clear. Psychosis, confusion, catatonia, and additional behavioral changes, along with seizures, encephalopathy, and movement disorders, may be initial manifestations or concurrent features in all age groups. Psychosis, when present, is often part of a broader spectrum of neurological and neuropsychiatric symptoms for which the diagnosis of autoimmune encephalitis is considered. The authors present the case of an adolescent with an acute and isolated psychotic presentation of voltage-gated potassium channel antibody encephalitis, further expanding the phenotypic spectrum of this specific antibody-mediated disease and raising the possibility that specific immune-mediated processes may define a biological subgroup of psychoses.

Psychosis: an autoimmune disease?

Psychotic disorders are common and disabling. Overlaps in clinical course in addition to epidemiological and genetic associations raise the possibility that autoimmune mechanisms may underlie some psychoses, potentially offering novel therapeutic approaches. Several immune loci including the major histocompatibility complex and B-cell markers CD19 and CD20 achieve genome-wide significance in schizophrenia. Emerging evidence suggests a potential role via neurodevelopment in addition to classical immune pathways. Additionally, lymphocyte biology is increasingly investigated. Some reports note raised peripheral CD19+ and reduced CD3+ lymphocyte counts, with altered CD4 : CD8 ratios in acute psychosis. Also, post-mortem studies have found CD3+ and CD20+ lymphocyte infiltration in brain regions that are of functional relevance to psychosis. More specifically, the recent paradigm of neuronal surface antibody-mediated (NSAb) central nervous system disease provides an antigen-specific model linking adaptive autoimmunity to psychopathology. NSAbs bind extracellular epitopes of signalling molecules that are classically implicated in psychosis such as NMDA and GABA receptors. This interaction may cause circuit dysfunction leading to psychosis among other neurological features in patients with autoimmune encephalitis. The detection of these cases is crucial as autoimmune encephalitis is ameliorated by commonly available immunotherapies. Meanwhile, the prevalence and relevance of these antibodies in people with isolated psychotic disorders is an area of emerging scientific and clinical interest. Collaborative efforts to achieve larger sample sizes, comparison of assay platforms, and placebo-controlled randomized clinical trials are now needed to establish an autoimmune contribution to psychosis.

Voltage-gated Potassium Channel Antibody Autoimmune Encephalopathy Presenting With Isolated Psychosis in an Adolescent

Antibody-mediated encephalopathies associated with serum or cerebrospinal fluid antibodies directed against neuronal structures may present with a multitude of neuropsychiatric syndromes. Although some of the antibody-driven conditions are now well recognized in adults (eg, N-methyl-D-aspartate receptor antibody encephalitis), the spectrum of neuropsychiatric manifestations in the pediatric population is less clear. Psychosis, confusion, catatonia, and additional behavioral changes, along with seizures, encephalopathy, and movement disorders, may be initial manifestations or concurrent features in all age groups. Psychosis, when present, is often part of a broader spectrum of neurological and neuropsychiatric symptoms for which the diagnosis of autoimmune encephalitis is considered. The authors present the case of an adolescent with an acute and isolated psychotic presentation of voltage-gated potassium channel antibody encephalitis, further expanding the phenotypic spectrum of this specific antibody-mediated disease and raising the possibility that specific immune-mediated processes may define a biological subgroup of psychoses.

Autoantibodies against voltage-gated potassium channel and glutamic acid decarboxylase in psychosis: A systematic review, meta-analysis, and case series

Antibodies to the voltage-gated potassium channel (VGKC) complex and glutamic acid decarboxylase (GAD) have been reported in some cases of psychosis. We conducted the first systematic review and meta-analysis to investigate their prevalence in people with psychosis and report a case series of VGKC-complex antibodies in refractory psychosis. Only five studies presenting prevalence rates of VGKC seropositivity in psychosis were identified, in addition to our case series, with an overall prevalence of 1.5% (25/1720) compared to 0.7% in healthy controls (12/1753). Meta-analysis established that the pooled prevalence of GAD65 autoantibodies was 5.8% (95% confidence interval [CI]: 2.0-15.6%; I²  = 91%; nine studies) in psychotic disorders, with a prevalence of 4.6% (95%CI: 1.2-15.9%; nine studies; I²  = 89%) and 6.2% (95%CI: 1.2-27.0%; two studies; I²  = 69%) in schizophrenia and bipolar disorder, respectively. People with psychosis were more likely to have GAD65 antibodies than controls (odds ratio [OR], 2.24; 95%CI: 1.28-3.92%; P = 0.005; eight studies; I²  = 0%). Among 21 participants with treatment-resistant psychosis, none had VGKC antibodies. The prevalence of VGKC antibodies is low in psychosis. Our preliminary meta-analysis suggests that GAD autoantibodies are more common in people with psychosis than in controls, although few studies accounted for the possibility of co-existing type 1 diabetes mellitus and the clinical significance of reported GAD titers remains unclear. The paucity of studies reporting thresholds for defining GAD abnormality and rates of comorbid type 1 diabetes mellitus precludes interpretations regarding the influence of GAD antibodies on the development of psychotic disorders and may have led to an overestimate of the prevalence of GAD. Our case series fails to support the hypothesis that VGKC antibodies are linked to treatment resistance in psychosis, but the literature to date is remarkably sparse.

Consensus paper of the WFSBP Task Force on Biological Markers: Criteria for biomarkers and endophenotypes of schizophrenia, part III: Molecular mechanisms

OBJECTIVES

Despite progress in identifying molecular pathophysiological processes in schizophrenia, valid biomarkers are lacking for both the disease and treatment response.

METHODS

This comprehensive review summarises recent efforts to identify molecular mechanisms on the level of protein and gene expression and epigenetics, including DNA methylation, histone modifications and micro RNA expression. Furthermore, it summarises recent findings of alterations in lipid mediators and highlights inflammatory processes. The potential that this research will identify biomarkers of schizophrenia is discussed.

RESULTS

Recent studies have not identified clear biomarkers for schizophrenia. Although several molecular pathways have emerged as potential candidates for future research, a complete understanding of these metabolic pathways is required to reveal better treatment modalities for this disabling condition.

CONCLUSIONS

Large longitudinal cohort studies are essential that pair a thorough phenotypic and clinical evaluation for example with gene expression and proteome analysis in blood at multiple time points. This approach might identify biomarkers that allow patients to be stratified according to treatment response and ideally also allow treatment response to be predicted. Improved knowledge of molecular pathways and epigenetic mechanisms, including their potential association with environmental influences, will facilitate the discovery of biomarkers that could ultimately be effective tools in clinical practice.

Autoimmunity, Autoantibodies, and Autism Spectrum Disorder

Auism spectrum disorder (ASD) now affects one in 68 births in the United States and is the fastest growing neurodevelopmental disability worldwide. Alarmingly, for the majority of cases, the causes of ASD are largely unknown, but it is becoming increasingly accepted that ASD is no longer defined simply as a behavioral disorder, but rather as a highly complex and heterogeneous biological disorder. Although research has focused on the identification of genetic abnormalities, emerging studies increasingly suggest that immune dysfunction is a viable risk factor contributing to the neurodevelopmental deficits observed in ASD. This review summarizes the investigations implicating autoimmunity and autoantibodies in ASD.

Autoantibodies against the N-Methyl-d-Aspartate Receptor Subunit NR1: Untangling Apparent Inconsistencies for Clinical Practice

This viewpoint review provides an integrative picture of seemingly contradictory work published on N-methyl-d-aspartate receptor 1 (NMDAR1) autoantibodies (AB). Based on the present state of knowledge, it gives recommendations for the clinical decision process regarding immunosuppressive treatment. Brain antigen-directed AB in general and NMDAR1-AB in particular belong to a preexisting autoimmune repertoire of mammals including humans. Specific autoimmune reactive B cells may get repeatedly (perhaps transiently) boosted by various potential stimulants (e.g., microbiome, infections, or neoplasms) plus less efficiently suppressed over lifespan (gradual loss of tolerance), likely explaining the increasing seroprevalence upon aging (>20% NMDAR1-AB in 80-year-old humans). Pathophysiological significance emerges (I) when AB-specific plasma cells settle in the brain and produce large amounts of brain antigen-directed AB intrathecally and/or (II) in conditions of compromised blood–brain barrier (BBB), for instance, upon injury, infection, inflammation, or genetic predisposition (APOE4 haplotype), which then allows substantial access of circulating AB to the brain. Regarding NMDAR1-AB, functional effects on neurons in vitro and elicitation of brain symptoms in vivo have been demonstrated for immunoglobulin (Ig) classes, IgM, IgA, and IgG. Under conditions of brain inflammation, intrathecal production and class switch to IgG may provoke high NMDAR1-AB (and other brain antigen-directed AB) levels in cerebrospinal fluid (CSF) and serum, causing the severe syndrome named “anti-NMDAR encephalitis,” which then requires immunosuppressive therapy on top of the causal encephalitis treatment (if available). However, negative CSF NMDAR1-AB results cannot exclude chronic effects of serum NMDAR1-AB on the central nervous system, since the brain acts as “immunoprecipitator,” particularly in situations of compromised BBB. In any case of suspected symptomatic consequences of circulating AB directed against brain antigens, leakiness of the BBB should be evaluated by CSF analysis (albumin quotient as proxy) and magnetic resonance imaging before considering immunosuppression.

IL1R2, CCR2, and CXCR4 May Form Heteroreceptor Complexes with NMDAR and D2R: Relevance for Schizophrenia

The mild neuroinflammation hypothesis of schizophrenia was introduced by Bechter in 2001. It has been hypothesized that a hypofunction of glutamatergic signaling via N-methyl-D-aspartate receptors (NMDARs) and hyperactivation of dopamine D2 receptors play a role in schizophrenia. The triplet puzzle theory states that sets of triplet amino acid homologies guide two different receptors toward each other and contributes to the formation of a receptor heteromer. It is, therefore, proposed that putative NMDAR-C-C chemokine receptor type 2 (CCR2), NMDAR-C-X-C chemokine receptor type 4 (CXCR4), and NMDAR- interleukin 1 receptor type II (IL1R2) heteromers can be formed in the neuronal networks in mild neuroinflammation due to demonstration of Gly-Leu-Leu (GLL), Val-Ser-Thr (VST), and/or Ser-Val-Ser (SVS) amino acid homologies between these receptor protomers. This molecular process may underlie the ability to produce symptoms of schizophrenia in mild neuroinflammation. In this state, volume transmission (VT) is increased involving increased extracellular vesicle-mediated VT from microglia and astroglia. These vesicles may contain CCR2, CXCR4, and/or IL1R2 as well as their ligands and upon internalization by endocytic pathways into neurons can form heteroreceptor complexes with NMDAR in the plasma membrane with pathological allosteric receptor-receptor interactions involving increased internalization and reduced NMDAR signaling. The triplet puzzle theory also suggests the formation of putative D2R-CCR2, D2R-CXCR4, and D2R-IL1R2 heteromers in mild neuroinflammation in view of their demonstrated sets of Leu-Tyr-Ser (LYS), Leu-Pro-Phe (LPF), and/or Ser-Leu-Ala (SLA) triplet homologies. These D2R heteroreceptor complexes may also contribute to schizophrenia-like symptoms in mild neuroinflammation by enhancing D2R protomer function.

Immuno-psychiatry: an agenda for clinical practice and innovative research

BACKGROUND

The diagnostic scheme for psychiatric disorders is currently based purely on descriptive nomenclature given that biomarkers subtypes and clearly defined causal mechanisms are lacking for the vast majority of disorders. The emerging field of "immuno-psychiatry" has the potential to widen the exploration of a mechanism-based nosology, possibly leading to the discovery of more effective personalised treatment strategies.

DISCUSSION

Disturbances in immuno-inflammatory and related systems have been implicated in the aetiology, pathophysiology, phenomenology and comorbidity of several psychiatric disorders, including major mood disorders and schizophrenia. A fundamental challenge in their clinical management is to identify bio-signatures that might indicate risk, state, trait, prognosis or theragnosis. Here, we provide the rationale for a clinical and research agenda to refine future clinical practice and conceptual views, and to delineate pathways toward innovative treatment discovery.

CONCLUSION

The development of bio-signatures will allow clinicians to tailor interventions to the abovementioned biomarker subtypes - a major translational goal for research in this field.

Mapping autoantigen epitopes: molecular insights into autoantibody-associated disorders of the nervous system

BACKGROUND

Our knowledge of autoantibody-associated diseases of the central (CNS) and peripheral (PNS) nervous systems has expanded greatly over the recent years. A number of extracellular and intracellular autoantigens have been identified, and there is no doubt that this field will continue to expand as more autoantigens are discovered as a result of improved clinical awareness and methodological practice. In recent years, interest has shifted to uncover the target epitopes of these autoantibodies.

MAIN BODY

The purpose of this review is to discuss the mapping of the epitope targets of autoantibodies in CNS and PNS antibody-mediated disorders, such as N-methyl-D-aspartate receptor (NMDAR), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), leucine-rich glioma-inactivated protein 1 (Lgi1), contactin-associated protein-like 2 (Caspr2), myelin oligodendrocyte glycoprotein (MOG), aquaporin-4 (AQP4), 65 kDa glutamic acid decarboxylase (GAD65), acetylcholine receptor (AChR), muscle-specific kinase (MuSK), voltage-gated calcium channel (VGCC), neurofascin (NF), and contactin. We also address the methods used to analyze these epitopes, the relevance of their determination, and how this knowledge can inform studies on autoantibody pathogenicity. Furthermore, we discuss triggers of autoimmunity, such as molecular mimicry, ectopic antigen expression, epitope spreading, and potential mechanisms for the rising number of double autoantibody-positive patients.

CONCLUSIONS

Molecular insights into specificity and role of autoantibodies will likely improve diagnosis and treatment of CNS and PNS neuroimmune diseases.

Focus on psychosis

The concept of psychosis has been shaped by traditions in the concepts of mental disorders during the last 170 years. The term "psychosis" still lacks a unified definition, but denotes a clinical construct composed of several symptoms. Delusions, hallucinations, and thought disorders are the core clinical features. The search for a common denominator of psychotic symptoms points toward combinations of neuropsychological mechanisms resulting in reality distortion. To advance the elucidation of the causes and the pathophysiology of the symptoms of psychosis, a deconstruction of the term into its component symptoms is therefore warranted. Current research is dealing with the delineation from "normality", the genetic underpinnings, and the causes and pathophysiology of the symptoms of psychosis.

Autoimmunity in neuropsychiatric disorders

The immune system's role in the pathophysiology of several neuropsychiatric disorders has been the subject of research for many decades. Despite suggestive evidence from genetic, epidemiologic, and immunologic studies, those findings did not translate into clinical practice. Recent recognition of antibody-mediated central nervous system (CNS) disorders has fueled the search for a subgroup of patients with an antibody-mediated psychiatric illness. This chapter focuses on the current understanding of autoimmune CNS disorders and how they may be relevant to psychiatric disorders, particularly schizophrenia and autism. We review the results provided by antibody screening in psychiatric patient groups and discuss future directions to establish whether those findings will be meaningful in clinical practice.

Circulating anti-brain autoantibodies in schizophrenia and mood disorders

In recent years, an inflammatory autoimmune process, autoantibodies mediated, has been porposed as having a role in the development of different psychiatric disorders. The aim of this study was to assay organ-specific and non organ-specific circulating autoantibodies in schizophrenia, mood disorders and healthy controls; among organ-specific autoantibodies we focused on different fluorescence patterns of anti-brain autoantibodies against rat and monkey's sections of hippocampus, hypothalamus and cerebellum. Serum samples from 50 acutelly ill patients (30 schizophrenia and 20 mood disorders) and from 20 healthy controls were collected. Autoantibodies were assayed by indirect immunofluorescence, enzyme linked immunosorbent assay and chemiluminescence immunoassay. We found a significant difference for circulating autoantibodies to hypothalamus, hippocampus and cerebellum and for anti-nuclear autoantibodies in both schizophrenia and mood disorders when compared to the control group. Referring to the two groups of patients only, circulating antibodies anti-hypothalamus were found significant higher in mood disorders rather than in schizophrenia, with specific regard to nuclear and cytoplasmic staining of the neurons. These data suggest an aspecific diffuse brain involvement of anti-brain autoantibodies in acute phases of schizophrenia and mood disorders. The greater involvement of the hypothalamus in mood disorders highlights the close relationship between autoimmunity, hypothalamic-pituitary-adrenal axis and affective disorders.

No evidence for the presence of neuronal surface autoantibodies in plasma of patients with schizophrenia

The immune system has been implicated in the etiology of schizophrenia. Autoimmunity by antibodies against neuronal cell surface antigens has been proposed as one of the pathological mechanisms. We examined plasma samples of 104 patients diagnosed with schizophrenia for the presence of autoantibodies against neuronal cell surface antigens using cultured hippocampal neurons and transfected HeLa cells. None of the samples tested positive for the presence of these autoantibodies. Based on our results it seems unlikely that autoantibodies against neuronal cell surface antigens play a role in the pathogenesis of schizophrenia, although further studies using cerebrospinal fluid are needed.

A case of autoimmune epilepsy associated with anti-leucine-rich glioma inactivated subunit 1 antibodies manifesting electrical shock-like sensations and transparent sadness

Autoimmune epilepsy is an isolated phenotype of autoimmune encephalitis, which may be suspected in patients with unexplained adult-onset seizure disorders or resistance to antiepileptic drugs (AEDs). Antibodies against leucine-rich glioma inactivated subunit 1 of the voltage-gated potassium channel (VGKC) complex, recently termed anti-LGI-1 antibodies, are one of the causes of autoimmune epilepsies. Bizarre symptoms with extremely short duration and high frequency are clues to the possible presence of autoimmune epilepsy with anti-LGI-1 antibodies. Precise diagnosis is important because autoimmune epilepsy is treatable and the prognosis can be predicted.

Ketamine and phencyclidine: the good, the bad and the unexpected

The history of ketamine and phencyclidine from their development as potential clinical anaesthetics through drugs of abuse and animal models of schizophrenia to potential rapidly acting antidepressants is reviewed. The discovery in 1983 of the NMDA receptor antagonist property of ketamine and phencyclidine was a key step to understanding their pharmacology, including their psychotomimetic effects in man. This review describes the historical context and the course of that discovery and its expansion into other hallucinatory drugs. The relevance of these findings to modern hypotheses of schizophrenia and the implications for drug discovery are reviewed. The findings of the rapidly acting antidepressant effects of ketamine in man are discussed in relation to other glutamatergic mechanisms.

Antibodies to surface dopamine-2 receptor and N-methyl-D-aspartate receptor in the first episode of acute psychosis in children

BACKGROUND

The dopamine and glutamate hypotheses are well known in psychosis. Recently, the detection of autoantibodies against proteins expressed on the surface of cells in the central nervous system has raised the possibility that specific immune-mediated mechanisms may define a biological subgroup within psychosis, although no cohort of a first episode of psychosis in children has been investigated.

METHODS

Serum taken during the acute presentation of 43 children with first episode of psychosis and serum from 43 pediatric control subjects was assessed for the presence of immunoglobulin (Ig)G, IgM, or IgA antibodies to dopamine-2 receptor (D2R) and NR1 subunit of the N-methyl-D-aspartate receptor using a flow cytometry live cell-based assay and immunolabeling of murine primary neurons.

RESULTS

Using a cutoff of three SD above the control mean, serum antibodies to D2R or NR1 were detected in 8 of 43 psychotic patients but not detected in any of 43 control subjects (p < .001). Positive immunoglobulin binding to D2R was found in 3 of 43 psychosis patients (3 IgG, 1 IgM, 0 IgA) and to N-methyl-D-aspartate receptor in 6 of 43 patients (5 IgG, 1 IgM, 1 IgA). Specificity of antibody was confirmed by immunoaffinity purification and immunoabsorption. Significant differences in antibody binding to live, fixed, and fixed and permeabilized neurons were observed, confirming that only live cells can define surface epitope immunolabeling.

CONCLUSIONS

This is the first report of serum antibodies to surface D2R and NR1 in pediatric patients with isolated psychosis, which supports the hypothesis that a subgroup of patients may be immune-mediated.

Preexisting Serum Autoantibodies Against the NMDAR Subunit NR1 Modulate Evolution of Lesion Size in Acute Ischemic Stroke

BACKGROUND AND PURPOSE

Recently, we reported high seroprevalence (age-dependent up to >19%) of N-methyl-d-aspartate-receptor subunit NR1 (NMDAR1) autoantibodies in both healthy and neuropsychiatrically ill subjects (N=4236). Neuropsychiatric syndrome relevance was restricted to individuals with compromised blood-brain barrier, for example, apolipoprotein E4 (APOE4) carrier status, both clinically and experimentally. We now hypothesized that these autoantibodies may upon stroke be protective in individuals with hitherto intact blood-brain barrier, but harmful for subjects with chronically compromised blood-brain barrier.

METHODS

Of 464 patients admitted with acute ischemic stroke in the middle cerebral artery territory, blood for NMDAR1 autoantibody measurements and APOE4 carrier status as indicator of a preexisting leaky blood-brain barrier was collected within 3 to 5 hours after stroke. Evolution of lesion size (delta day 7-1) in diffusion-weighted magnetic resonance imaging was primary outcome parameter. In subgroups, NMDAR1 autoantibody measurements were repeated on days 2 and 7.

RESULTS

Of all 464 patients, 21.6% were NMDAR1 autoantibody-positive (immunoglobulin M, A, or G) and 21% were APOE4 carriers. Patients with magnetic resonance imaging data available on days 1 and 7 (N=384) were divided into 4 groups according to NMDAR1 autoantibody and APOE4 status. Groups were comparable in all stroke-relevant presenting characteristics. The autoantibody+/APOE4- group had a smaller mean delta lesion size compared with the autoantibody-/APOE4- group, suggesting a protective effect of circulating NMDAR1 autoantibodies. In contrast, the autoantibody+/APOE4+ group had the largest mean delta lesion area. NMDAR1 autoantibody serum titers dropped on day 2 and remounted by day 7.

CONCLUSIONS

Dependent on blood-brain barrier integrity before an acute ischemic brain injury, preexisting NMDAR1 autoantibodies seem to be beneficial or detrimental.

Antineuronal antibodies against neurotransmitter receptors and synaptic proteins in schizophrenia: current knowledge and clinical implications

When Eugen Bleuler coined the term 'schizophrenia' he believed that various causes of illness may underlie this disease. Currently, neurodevelopmental abnormalities and consecutive impairments in dopaminergic and glutamatergic neurotransmission are considered as major causes of schizophrenia. However, there are various indications for involvement of immune processes, at least in subgroups of patients. Circulating antineuronal antibodies provide a promising link between the well-described disturbances in neurotransmission and the immune hypothesis of schizophrenia. This review summarizes important studies that have examined the role of glutamate, dopamine, acetylcholine and serotonin receptor autoantibodies, and other antineuronal antibodies against synaptic proteins in the serum of patients diagnosed with schizophrenia. Currently, it is not known whether the presence of antineuronal antibodies in blood should be considered as a causal or disease-modulating factor in schizophrenia. Due to emerging evidence regarding the important role of the blood-brain barrier, combined testing of serum and cerebrospinal fluid is likely to be more appropriate to answer this question than pure serum analyses. We suggest implementation of such testing in first-onset and treatment-resistant patients as part of the diagnostic process. In addition, future clinical trials should evaluate if immunotherapy (e.g. cortisone pulse therapy, intravenous immunoglobulins, plasmapheresis, rituximab, or cyclophosphamide) is helpful in cases with a neuroinflammatory component.

Myasthenia gravis and risks for comorbidity

Myasthenia gravis (MG) is an autoimmune disorder leading to skeletal muscle weakness and fatigability. MG subgroups are defined according to pathogenetic autoantibody (against acetylcholine receptor, muscle-specific tyrosine kinase or lipoprotein receptor-related protein 4), thymus pathology and clinical manifestations. MG patients have an increased risk for concordant autoimmune disease, in particular with early onset MG. Most common comorbidities are thyroid disease, systemic lupus erythematosus and rheumatoid arthritis. Cardiomyositis and subclinical heart dysfunction have been described in patients with thymoma MG and late onset MG but represent no major threat. A thymic lymphoepithelioma implies an increased risk for another cancer. Autoimmune MG represents no distinct cancer risk factor, although lymphomas and a few other cancer types have been reported with slightly increased frequency. Severe MG-related muscle weakness means a risk for respiratory failure and respiratory tract infection. Drug MG treatment can lead to side-effects. Thymectomy is regarded as a safe procedure both short and long term. Non-MG-related comorbidity represents a diagnostic and therapeutic challenge, especially in elderly patients. Diagnostic accuracy and optimal follow-up is necessary to identify and treat all types of coexisting disease in MG.

Epilepsy-related psychosis: a role for autoimmunity?

Postictal psychosis (PIP) is a serious psychiatric complication of epilepsy that occurs in approximately 6% of patients following multiple complex partial or generalized seizures. The psychosis is classically described as having a pleomorphic phenomenology, including paranoid, grandiose, and religious delusions as well as multimodal hallucinations with prominent affective changes and agitation. Little is understood about the pathophysiology of the condition. There has been a recent increase in interest in the relevance of autoimmunity to the pathogenesis of both epilepsy and psychosis. Studies have demonstrated the presence of antibodies directed against synaptic autoantigens (such as the N-methyl-d-aspartate receptor or the voltage-gated potassium channel complex) in approximately 10% of cases of sporadic epilepsy. These same autoantibodies are known to cause encephalopathy syndromes which feature psychiatric symptoms, usually psychosis, as a prominent part of the phenotype as well as other neurological features such as seizures, movement disorders, and autonomic dysfunction. It is beginning to be asked if these antibodies can be associated with a purely psychiatric phenotype. Here, we hypothesize that PIP may be an autoimmune phenomenon mediated by autoantibodies against synaptic antigens. More specifically, we outline a potential mechanism whereby long or repeated seizures cause short-lived blood-brain barrier (BBB) dysfunction during which the brain becomes exposed to pathogenic autoantibodies. In essence, we propose that PIP is a time-limited, seizure-dependent, autoantibody-mediated encephalopathy syndrome. We highlight a number of features of PIP that may be explained by this mechanism, such as the lucid interval between seizures and onset of psychosis and the progression in some cases to a chronic, interictal psychosis.