Patients whose tumour was identified and removed within the first 4 months of the onset of the neurological disease had better outcome than the rest of the patients (figure 2)

Patients whose tumour was identified and removed within the first 4 months of the onset of the neurological disease had better outcome than the rest of the patients (figure 2). tumour treatment (usually with immunotherapy) had better outcome (p=0.004) and fewer neurological relapses (p=0.009) than the rest of the patients. 75 patients recovered or had mild deficits and 25 had severe deficits or died. Improvement was associated with a decrease of serum antibody titres. The main epitope targeted by the antibodies is in the extracellular N-terminal domain of the NR1 subunit. Patients antibodies decreased the numbers of cell-surface NMDA receptors and NMDA-receptor clusters in postsynaptic dendrites, an effect that could be reversed by antibody removal. Interpretation A well-defined set of clinical characteristics are associated with anti-NMDA-receptor encephalitis. The pathogenesis of the disorder seems to be mediated by antibodies. Introduction NMDA receptors are ligand-gated cation channels with crucial roles in synaptic transmission and plasticity. The receptors are heteromers of NR1 subunits that bind glycine and NR2 (A, B, C, or D) subunits that bind glutamate.1 NR1 and NR2 combine to form receptor subtypes with distinct pharmacological properties, localisation, and ability to interact with intracellular messengers. Overactivity of NMDA receptors causing excitotoxicity is a proposed underlying mechanism for epilepsy, dementia, and stroke, whereas low activity produces symptoms of schizophrenia.2C4 We recently identified a disorder, designated anti-NMDA-receptor encephalitis, that associates with antibodies against NR1CNR2 heteromers and results in a characteristic neuropsychiatric syndrome. 5 The first patients identified were young women with ovarian teratoma who presented with psychosis or memory problems, rapidly progressing to multiple neurological deficits requiring prolonged intensive care support. Despite the severity of the disorder, patients often recovered after tumour removal and immunotherapy, suggesting an immune-mediated pathogenesis. Preliminary studies suggested the target epitopes were located in extracellular regions of NR1CNR2B NMDA receptors.5 However, selective disruption of receptors containing NR2B, which are predominantly expressed in the forebrain and hippocampus, would not explain the extensive deficits of patients. We postulated that the crucial epitopes were present in the more widely expressed NR1 subunit. If the antibodies were pathogenic we reasoned that their effects on NMDA receptors would be reversible because most patients recover. We report the clinical features of 100 patients, analysing the frequency CCT245737 and type of tumour association, antibody titres, and response to treatment. We also investigate the epitopic region of the NMDA receptor and how antibodies affect NMDA receptors in primary cultures of hippocampal neurons. Methods Patients and procedures Clinical information was obtained by the authors or provided by referring physicians, and has been partly reported for 21 patients. 5C9 The webappendix contains additional information and details of control individuals. Control samples were obtained from 20 healthy individuals and 230 patients with suspected autoimmune or paraneoplastic encephalitis, or patients with tumours without encephalitis examined during the period of this study. Samples were from patients seen at University of Pennsylvania or patients referred to the university for a study of autoimmune disorders. All patients had brain MRI, radiological screening for a systemic neoplasm, and serological or CSF studies that ruled out other disorders (webappendix). Serum and CSF were tested for antibodies against the NMDA receptor,5 and considered positive if three immunohistochemical criteria were fulfilled (figure 1). Antibody titres were measured with ELISA on HEK293 cell lysates ectopically expressing NR1 or CCT245737 NR1CNR2B heteromers (webappendix). Studies were approved RPS6KA1 by the University of Pennsylvania Institutional Review Board. Open in a separate window Figure 1 Immunohistochemical criteria for the presence of NR1CNR2B antibodiesSera and CSF from all patients with anti-NMDA-receptor encephalitis showed identical antibody reactivity in three different assays. Coronal section of rat brain incubated with a representative CSF (A) shows intense reactivity predominantly involving the hippocampus. Cultures of non-permeabilised live rat hippocampal neurons (B) incubated with the same CSF show extensive cell-surface immunolabelling. HEK293 cells transfected with NR1 and NR2B (forming NR1CNR2B heteromers of the NMDA receptor) show intense reactivity with patients CSF (C); this reactivity co-localises (D) with the reactivity of a monoclonal rabbit CCT245737 antibody against NR1 (E). Immunofluorescence method, nuclei of cells shown with 4,6-diamidino-2-phenylindole (DAPI). A 25; B 800 oil lens; CCE 400. Neurological outcome was assessed with the modified Rankin scale (MRS)10 and mini-mental.