CaV α2δ Autoimmune Encephalitis: A Novel Antibody and its Characteristics.

OBJECTIVE: Discovery of a novel antibody would enable diagnosis and early treatment of autoimmune encephalitis. The aim was to discover a novel antibody targeting a synaptic receptor and characterize the pathogenic mechanism. METHOD: We screened for unknown antibodies in serum and cerebrospinal fluid samples from autoimmune encephalitis patients. Samples with reactivity to rat brain sections and no reactivity to conventional antibody tests underwent further processing for antibody discovery, using immunoprecipitation to primary neuronal cells, mass-spectrometry analysis, an antigen-binding assay on an antigen-overexpressing cell line, and an electrophysiological assay with cultured hippocampal neurons. RESULTS: Two patients had a novel antibody against CaV α2δ (voltage-gated calcium channel alpha-2/delta subunit). The patient samples stained neuropils of the hippocampus, basal ganglia, and cortex in rat brain sections and bound to a CaV α2δ-overexpressing cell line. Knockdown of CaV α2δ expression in cultured neurons turned off the immunoreactivity of the antibody from the patients to the neurons. The patients were associated with preceding meningitis or neuroendocrine carcinoma and responded to immunotherapy. In cultured neurons, the antibody reduced neurotransmitter release from presynaptic nerve terminals by interfering with tight coupling of calcium channels and exocytosis. INTERPRETATION: Here, we discovered a novel autoimmune encephalitis associated with anti-CaV α2δ antibody. Further analysis of the antibody in autoimmune encephalitis might promote early diagnosis and treatment. ANN NEUROL 2021;89:740-752.

Routine diagnostics for neural antibodies, clinical correlates, treatment and functional outcome.

OBJECTIVE: To determine frequencies, interlaboratory reproducibility, clinical ratings, and prognostic implications of neural antibodies in a routine laboratory setting in patients with suspected neuropsychiatric autoimmune conditions. METHODS: Earliest available samples from 10,919 patients were tested for a broad panel of neural antibodies. Sera that reacted with leucine-rich glioma-inactivated protein 1 (LGI1), contactin-associated protein-2 (CASPR2), or the voltage-gated potassium channel (VGKC) complex were retested for LGI1 and CASPR2 antibodies by another laboratory. Physicians in charge of patients with positive antibody results retrospectively reported on clinical, treatment, and outcome parameters. RESULTS: Positive results were obtained for 576 patients (5.3%). Median disease duration was 6 months (interquartile range 0.6-46 months). In most patients, antibodies were detected both in CSF and serum. However, in 16 (28%) patients with N-methyl-D-aspartate receptor (NMDAR) antibodies, this diagnosis could be made only in cerebrospinal fluid (CSF). The two laboratories agreed largely on LGI1 and CASPR2 antibody diagnoses (κ = 0.95). The clinicians (413 responses, 71.7%) rated two-thirds of the antibody-positive patients as autoimmune. Antibodies against the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), NMDAR (CSF or high serum titer), γ-aminobutyric acid-B receptor (GABABR), and LGI1 had ≥ 90% positive ratings, whereas antibodies against the glycine receptor, VGKC complex, or otherwise unspecified neuropil had ≤ 40% positive ratings. Of the patients with surface antibodies, 64% improved after ≥ 3 months, mostly with ≥ 1 immunotherapy intervention. CONCLUSIONS: This novel approach starting from routine diagnostics in a dedicated laboratory provides reliable and useful results with therapeutic implications. Counseling should consider clinical presentation, demographic features, and antibody titers of the individual patient.

Effects of in vivo and in vitro administration of neuro-Behcet's disease IgG.

Antibodies directed against membrane antigens of neuronal axonal processes (neuropil) have been recently identified in neuro-Behcet's disease (NBD) patients. To delineate the potential pathogenic action of these antibodies, pooled sera from seven NBD patients with neuropil antibodies and seven healthy controls were divided into purified IgG and IgG-depleted serum (IgG-DS) fractions and each fraction was administered into lateral ventricles of rats. NBD IgG-injected rats showed reduced locomotor activity in the open field test as compared to NBD IgG-DS, healthy control IgG, healthy control IgG-DS and PBS injected rats (n = 10 for each group). There were no significant differences among treatment groups by means of anxiety-like behaviors (assessed by elevated plus maze test) and learning/memory functions (assessed by passive avoidance test). Administration of NBD IgG on cultured SH-SY5Y neuroblastoma cells induced significantly increased cell death and apoptosis (as measured by nucleosome levels in the supernatants) as compared to other treatment groups. Our results suggest that IgGs isolated from sera of neuropil antibody-positive NBD patients have a neurotoxic action, which is presumably mediated by apoptotic mechanisms. Motor deficits frequently observed in NBD patients might at least partially be caused by the pathogenic action of anti-neuronal IgG.

Identificación y utilidad clínica de los anticuerpos antineuronales / Identification and clinical usefulness of anti-neuronal antibodies

Revisamos los anticuerpos neuronales descritos en las enfermedades del SNC con el fin de clarificar su valor diagnóstico. En este estudio los anticuerpos neuronales asociados con los síndromes resultantes de la disfunción neuronal del SNC se clasifican en 2 grupos en función de la localización del antígeno dentro de la neurona o en la membrana celular. El grupo I incluye los anticuerpos cuya diana son antígenos intracelulares y probablemente no son patogénicos. Estos incluyen anticuerpos onconeurales (Hu [ANNA1], Yo [PCA1], Ri [ANNA2], CV2 [CRMP5], amphiphysin, Ma2, Tr, SOX1) que son útiles para el diagnóstico de los síndromes neurológicos paraneoplásicos (SNP). Otros anticuerpos de este grupo, principalmente anticuerpos anti-descarboxilasa del ácido glutámico (GAD), identifican otros síndromes no paraneoplásicos como el síndrome de la persona rígida (SPS), la ataxia cerebelar y la encefalitis límbica (LE). Los anticuerpos del grupo II reconocen antígenos de la superficie neuronal. Los anticuerpos de este grupo se asocian con síndromes característicos del SNC, pero su detección no indica que el trastorno sea paraneoplásico. Los más frecuentes son los anticuerpos anti-receptor NMDA, seguidos de los anticuerpos contra la proteína LGl1 asociada al canal de potasio. Otros anticuerpos menos comunes incluyen aquellos contra los receptores de AMPA, GABAb, mGluR 1 y 5 y contra CASPR2. Se sugiere un papel patogénico de los anticuerpos debido a la respuesta de los síntomas a la terapia inmunológica y la correlación entre la titulación del anticuerpo y los resultados neurológicos (AU)

We review the neuronal antibodies described in CNS disorders in order to clarify their diagnostic value. In this work, the neuronal antibodies associated with syndromes resulting from CNS neuronal dysfunction were classified into two groups according to the location of the antigen inside the neuron or in the cell membrane. Group I includes antibodies that target intracellular antigens and are probably not pathogenic. They include onconeural antibodies (Hu [ANNA1], Yo [PCA1], Ri [ANNA2], CV2 [CRMP5], amphiphysin, Ma2, Tr, SOX1), which are useful for the diagnosis of paraneoplastic neurological syndromes (PNS). Other antibodies of this group, mainly anti-glutamic acid decarboxylase (GAD) antibodies, identify non-paraneoplastic syndromes (PNS), such as stiff-person syndrome (SPS), cerebellar ataxia, and limbic encephalitis (LE). Group II antibodies recognize neuronal surface antigens. Antibodies in this group are associated with characteristic CNS syndromes, but their detection does not indicate that the disorder is paraneoplastic. The most frequent are the anti-receptor NMDA antibodies, followed by the antibodies against the protein LGI1 associated with the potassium channel. Other less common antibodies include those against the receptors of AMPA, GABAb, mGluR 1 and 5, and against CASPR2. A pathogenic role of the antibodies is suggested by the response of symptoms to immunotherapy, and the correlation between antibody titers and neurological outcome (AU)

Encephalitis with refractory seizures, status epilepticus, and antibodies to the GABAA receptor: a case series, characterisation of the antigen, and analysis of the effects of antibodies.

BACKGROUND: Increasing evidence suggests that seizures and status epilepticus can be immune-mediated. We aimed to describe the clinical features of a new epileptic disorder, and to establish the target antigen and the effects of patients' antibodies on neuronal cultures. METHODS: In this observational study, we selected serum and CSF samples for antigen characterisation from 140 patients with encephalitis, seizures or status epilepticus, and antibodies to unknown neuropil antigens. The samples were obtained from worldwide referrals of patients with disorders suspected to be autoimmune between April 28, 2006, and April 25, 2013. We used samples from 75 healthy individuals and 416 patients with a range of neurological diseases as controls. We assessed the samples using immunoprecipitation, mass spectrometry, cell-based assay, and analysis of antibody effects in cultured rat hippocampal neurons with confocal microscopy. FINDINGS: Neuronal cell-membrane immunoprecipitation with serum of two index patients revealed GABAA receptor sequences. Cell-based assay with HEK293 expressing α1/ß3 subunits of the GABAA receptor showed high titre serum antibodies (>1:160) and CSF antibodies in six patients. All six patients (age 3-63 years, median 22 years; five male patients) developed refractory status epilepticus or epilepsia partialis continua along with extensive cortical-subcortical MRI abnormalities; four patients needed pharmacologically induced coma. 12 of 416 control patients with other diseases, but none of the healthy controls, had low-titre GABAA receptor antibodies detectable in only serum samples, five of them also had GAD-65 antibodies. These 12 patients (age 2-74 years, median 26.5 years; seven male patients) developed a broader spectrum of symptoms probably indicative of coexisting autoimmune disorders: six had encephalitis with seizures (one with status epilepticus needing pharmacologically induced coma; one with epilepsia partialis continua), four had stiff-person syndrome (one with seizures and limbic involvement), and two had opsoclonus-myoclonus. Overall, 12 of 15 patients for whom treatment and outcome were assessable had full (three patients) or partial (nine patients) response to immunotherapy or symptomatic treatment, and three died. Patients' antibodies caused a selective reduction of GABAA receptor clusters at synapses, but not along dendrites, without altering NMDA receptors and gephyrin (a protein that anchors the GABAA receptor). INTERPRETATION: High titres of serum and CSF GABAA receptor antibodies are associated with a severe form of encephalitis with seizures, refractory status epilepticus, or both. The antibodies cause a selective reduction of synaptic GABAA receptors. The disorder often occurs with GABAergic and other coexisting autoimmune disorders and is potentially treatable. FUNDING: The National Institutes of Health, the McKnight Neuroscience of Brain Disorders, the Fondo de Investigaciones Sanitarias, Fundació la Marató de TV3, the Netherlands Organisation for Scientific Research (Veni-incentive), the Dutch Epilepsy Foundation.

Brain development in the yellow fever mosquito Aedes aegypti: a comparative immunocytochemical analysis using cross-reacting antibodies from Drosophila melanogaster.

Considerable effort has been directed towards understanding the organization and function of peripheral and central nervous system of disease vector mosquitoes such as Aedes aegypti. To date, all of these investigations have been carried out on adults but none of the studies addressed the development of the nervous system during the larval and pupal stages in mosquitoes. Here, we first screen a set of 30 antibodies, which have been used to study brain development in Drosophila, and identify 13 of them cross-reacting and labeling epitopes in the developing brain of Aedes. We then use the identified antibodies in immunolabeling studies to characterize general neuroanatomical features of the developing brain and compare them with the well-studied model system, Drosophila melanogaster, in larval, pupal, and adult stages. Furthermore, we use immunolabeling to document the development of specific components of the Aedes brain, namely the optic lobes, the subesophageal neuropil, and serotonergic system of the subesophageal neuropil in more detail. Our study reveals prominent differences in the developing brain in the larval stage as compared to the pupal (and adult) stage of Aedes. The results also uncover interesting similarities and marked differences in brain development of Aedes as compared to Drosophila. Taken together, this investigation forms the basis for future cellular and molecular investigations of brain development in this important disease vector.

Steroid-responsive recurrent limbic encephalitis associated with small cell lung cancer and neuropil antibodies.

Paraneoplastic limbic encephalitis (PLE) associated with small cell lung cancer (SCLC) often presents with antibodies to intracellular antigens and a poor outcome even after tumor resection and immunotherapy. We report a PLE patient presenting with generalized seizures, shortterm memory impairment and medial temporal lobe hyperintensity in MRI. Initial screening revealed significantly elevated thyroid antibody levels suggesting Hashimoto's encephalopathy. Following methylprednisolone treatment, her seizures ceased, MRI findings disappeared and memory impairment showed a partial resolution in 5 months. Two months later, she developed further generalized seizures. Chest X-ray showed a mass lesion, which was demonstrated by needle biopsy to be a small cell lung carcinoma (SCLC). The panel of onconeural antibodies including cell-membrane antigens was negative. However, the patient's serum and cerebrospinal fluid IgG, obtained during both exacerbations, immunolabeled cytoplasm and dendrites of Purkinje cells, cerebellar and hippocampal molecular layers, basal ganglia, thalamus, and the surface of cultured hippocampal neurons, in a manner distinct from previously identified neuropil antibodies associated with SCLC. These neuropil antibodies appear to be associated with a favorable response to treatment. Further studies are required for determination of the target antigen.

New onset refractory convulsive status epilepticus associated with serum neuropil auto-antibodies in a school aged child.

We report a case of a child that suffered from a severe new onset status epilepticus a few days after a common viral infection. Despite extensive screening, no bacterial, viral or fungal infection could be found. Using immunohistochemical analysis, we found neuronal auto-antibodies directed against the neuropil, in blood and CSF, associated with CSF oligoclonal banding. Status epilepticus was highly refractory to antiepileptic drugs, but improved few days after Intra-Venous Immunoglobulin Injection (IVIG). The patient developed ongoing temporal lobe epilepsy that was still associated with neuropil auto-antibodies. Therefore, screening for antineuronal antibodies should be helpful to characterize and maybe to handle new onset status epilepticus without any obvious aetiology. Further studies should establish the link between epilepsy and such auto-antibodies.

Encefalitis por anticuerpos contra el receptor NMDA. Descripción de una paciente sin tumor asociado y revisión de la bibliografía / Encephalitis due to antibodies against the NMDA receptor. A case report of a female patient with no associated tumour and a literature review

Introducción. Recientemente se ha descrito una forma grave de encefalitis aguda asociada a anticuerpos contra el receptor N-metil-D-aspartato (NMDA). Este cuadro ocurre en jóvenes, no siempre con un tumor subyacente y, pese a la gravedad inicial, su identificación y tratamiento precoz pueden llevar a recuperaciones sin secuelas. Presentamos un nuevo caso y revisamos los conocimientos disponibles acerca de esta nueva entidad. Caso clínico. Mujer de 22 años de edad que acudió a nuestro centro como consecuencia de un trastorno progresivo del comportamiento. Durante los días siguientes, un deterioro del nivel de conciencia hizo necesario el soporte respiratorio. Una resonancia magnética craneal mostró lesiones hiperintensas principalmente en regiones temporales profundas. El estudio de líquido cefalorraquídeo reveló pleocitosis con predominio linfocitario y anticuerpos contra el receptor NMDA. En el estudio complementario no se apreció tumor subyacente. El tratamiento con corticoesteroides e inmunoglobulinas dio lugar a una lenta pero continua mejoría. Al cabo de un año de seguimiento no ha presentado recidivas, no ha aparecido tumor alguno y la paciente se ha reintegrado a sus actividades habituales. Incluso una atrofia temporal llamativa desarrollada al inicio del cuadro se ha ido resolviendo en estudios de neuroimagen de control. Conclusión. La encefalitis por anticuerpos anti-NMDA es una enfermedad recientemente caracterizada, pero, de acuerdo con los datos disponibles hasta la fecha, relativamente frecuente. Clínicamente bien definida, la sospecha de esta entidad hará posible un diagnóstico definitivo y la instauración de un tratamiento precoz (AU)

Introduction. A severe form of acute encephalitis associated to antibodies against the N-methyl D-aspartate (NMDA) receptor has recently been reported. This clinical picture occurs in young people, not always with an underlying tumour and, despite the initial severity, if identified and treated at an early stage, complete recovery without any kind of sequelae can be achieved. We report on a new case and review the body of knowledge currently available on this recently identified condition. Case report. A 22-year-old female who visited our centre due to a progressive conduct disorder. Over the days that followed, deterioration in the level of consciousness made it necessary to put her on assisted respiration. Magnetic resonance imaging of the head showed hyperintense lesions mainly in deep temporal regions. A study of the cerebrospinal fluid revealed pleocytosis with a predominance of lymphocytes and antibodies against the NMDA receptor. In the complementary study no underlying tumour was observed. Treatment with corticosteroids and immunoglobulins brought about a slow but steady improvement. After a one-year follow-up there have been no recurrences, no tumours have appeared and the patient has gone back to her usual day-to-day activities. Even a significant temporal atrophy that developed at the beginning of the clinical picture has gradually been seen to resolve itself in neuroimaging studies performed as a control measure. Conclusion. Encephalitis due to anti-NMDA antibodies is a disease that has only recently been characterised, but which, according to currently available data, is relatively frequent. Clinically well defined, suspicion of this condition will make it possible to reach a definitive diagnosis and to establish early treatment (AU)

Diagnostic value of N-methyl-D-aspartate receptor antibodies in women with new-onset epilepsy.

BACKGROUND: In women younger than 45 years, a new form of encephalitis associated with ovarian teratoma and presenting with seizures and psychiatric symptoms has been described. Most patients have antibodies to NR1/NR2 heteromers of the N-methyl-D-aspartate receptor (NMDAR). OBJECTIVE: To assess the frequency and significance of antibodies to NMDAR in otherwise unexplained new-onset epilepsies in young women. DESIGN: Prospective cohort study. SETTING: University department of epileptology. PATIENTS: From January 1, 2005, to June 30, 2007, we identified 19 female patients aged 15 to 45 years with unexplained new-onset epilepsy. In addition, we studied 61 cerebrospinal fluid-serum sample pairs from patients with other cryptogenic epilepsies and 11 cerebrospinal fluid-serum sample pairs from surgically treated patients with epilepsy with no evident encephalitic abnormalities. MAIN OUTCOME MEASURES: Antibodies to NMDAR and characteristics of affected patients. RESULTS: Five of the 19 patients had antibodies against NMDAR. These patients had diffuse cerebral dysfunction and seizure origins. Psychiatric symptoms and pleocytosis were significantly associated with this group of patients. The disease course was episodic, in part relapsing-remitting, with full recoveries either spontaneously or after corticosteroid or intravenous immunoglobulin treatments. Only 1 patient had a neoplasm (multiple neuroendocrine tumors that included the ovaries) identified to date. In the control series, one 22-year-old man with a cryptogenic, severely encephalopathic seizure disorder was NMDAR antibody positive, and he also recovered fully. CONCLUSIONS: Anti-NMDAR encephalitis accounts for a relevant proportion of otherwise unexplained new-onset epilepsies. Patients harboring NMDAR antibodies usually have prominent psychiatric symptoms and pleocytosis, and they may develop hypoventilation. Anti-NMDAR encephalitis is not always paraneoplastic.

[Limbic encephalitis: the new cell membrane antigens and a proposal of clinical-immunological classification with therapeutic implications]. / Encefalitis límbica: los nuevos antígenos y propuesta de una clasificación clinicoinmunológica con implicaciones terapéuticas.

INTRODUCTION: Most studies of patients with limbic encephalitis, paraneoplastic or not, use rigid clinical-radiological entry criteria or select patients previously known to have cancer or to harbor well characterized paraneoplastic antibodies. In practice this selection excludes a significant number of patients with autoimmune encephalitides, some of which may represent new disorders. METHODS: Review of the literature and our clinical experience with patients with limbic encephalitis. Description of the studies that led to the identification of new antibodies and antigens related to several types of autoimmune encephalitis. RESULTS: 82 % of prospectively identified patients with non-viral limbic encephalitis at our institution had 526 antibodies against proteins of the CNS. These antibodies were directed against two category of antigens: a) intracellular or classical paraneoplastic antigens (Hu, Ma2, among other), and b) cell membrane antigens including the voltage-gated potassium channels and the newly identified antigens of the neuropil of hippocampus. Each category of antigens included several subgroups with distinctive clinical-immunological associations. While the encephalitides related to intracellular antigens are predominantly mediated by cytotoxic T-cell mechanisms and are poorly responsive to treatment, those related to cell membrane antigens appear to be mediated by antibodies and often respond to treatment. Among the newly identified antigens, the NR1/NR2B heteromers of the NMDA receptor are of great interest due to their critical role in synaptic plasticity and memory. Patients with antibodies against these receptors are young women with benign-appearing cystic tumors of the ovary (mature or immature teratomas), who develop a severe and characteristic encephalitis that we report in detail. Despite the severity of the disorder, patients often recover after treatment of the tumor and immunotherapy. CONCLUSIONS: Approximately 40 % of patients with classical or atypical limbic encephalitis develop relevant immune responses that are not identified by currently available commercial tests. Different from the previously known paraneoplastic antigens, which location is intracellular and associate with syndromes that are poorly responsive to treatment, the newly identified antigens of the neuropil of hippocampus are in the neuronal cell membrane and the related syndromes, although severe and potentially lethal, often respond to treatment.

Immunoreactivity of calcium binding protein secretagogin in the human hippocampus is restricted to pyramidal neurons.

Disturbed calcium homeostasis plays a crucial role in the aetiology of Alzheimer's disease (AD) and the aging process. We evaluated immunoreactivity of secretagogin, a recently cloned calcium binding protein, in hippocampus and adjacent entorhinal cortex of 30 neuropathologically examined post mortem brains (m:f=12:18; mean age, 79.8+/-15.1 years). The study group consisted of 15 cases fulfilling the criteria for high probability of AD according to the NIA-Reagan Institute Criteria and 15 cases with no to medium probability. Sections were incubated with secretagogin-specific antibodies and the number of immunoreactive neurons as well as staining intensities in both neurons and neuropil were assessed. Both cellular and neuropil immunoreactivity were restricted to subiculum and Ammons horn. Cellular immunoreactivity was further restricted to pyramidal neurons and showed a hierarchical distribution: the mean percentage of immunoreactive neurons was highest in sector CA3 (64.41%), followed by CA2 (44.09%), CA4 (34.38%), CA1 (10.9%), and the subiculum (2.92%; P<0.001, except CA2-CA4, P>0.05), while it did not differ significantly between groups with different degrees of AD pathology. The pattern of secretagogin immunoreactivity resembles that of calcium sensor proteins as it is restricted to a subset of neurons and therefore secretagogin could serve highly specialized tasks in neuronal calcium signalling.

Regionally specific distribution of the binding of anti-glutamine synthetase and anti-S100 antibodies and of Datura stramonium lectin in glial domains of the optic lobe of the giant prawn.

We previously characterized some crustacean glial cells by markers such as 2',3'-cyclic nucleotide 3'-phosphodiesterase and glial fibrillary acidic protein. Here we use antibodies against glutamine synthetase full-length molecule (anti-GS/FL), a GS C-terminal peptide (anti-GS/20aa-C), and brain S100 (anti-S100), as well as the binding of the insect glia and rat astrocytic marker Datura stramonium lectin (DSL), in the optic lobe of the prawn Macrobrachium rosenbergii. All markers label the lamina ganglionaris cartridge region (lighter: anti-GS/FL; heavier: DSL). In addition, anti-GS/FL labels superficial somata of external and internal medullas and internal chiasm cells. Both anti-GS/20aa-C and anti-S100 label heavily the glial sheaths of the lamina ganglionaris. In addition, anti-S100 binds to the perineurial glia of medullary parenchymal vessels. Western blot analyses show that both anti-GS/FL and anti-GS/20aa-C bind mostly to a band of 50-55 kDa, compatible with a long isoform of vertebrate GS, and accessorily to a possible dimer and, in the case of anti-GS/20aa-C, to an ill-defined band of intermediate mass. Binding of anti-S100 is selective for a single band of about 68 kDa but shows no protein in the weight range of the canonical S100 protein superfamily. DSL reveals two bands of about 75 and about 120 kDa, thus within the range of maximal recognition for rat astrocytes. Our results suggest that phenotype protein markers of the optic lobe glia share antigenic determinants with S100 and (a long form of) GS and that, similarly to vertebrate and insect glia, crustacean glia protein and N-glycan residue markers display regional heterogeneity.

Transient ischemia-induced changes of neurofilament 200 kDa immunoreactivity and protein content in the main olfactory bulb in gerbils.

This study was carried out to investigate alterations of neurofilament 200 kDa (NF-200) and its polyphosphorylation form (RT97) immunoreactivity and protein content in the main olfactory bulb (MOB) after 5 min of transient forebrain ischemia in gerbils. In the sham-operated group, weak NF-200 immunoreactivity was detectable in a few somata of mitral cells, which projected weak NF-200-immunoreactive processes to the external plexiform layer (EPL). At 1-5 days after ischemia, strong NF-200 and RT97 immunoreactivity was shown by the mitral cell processes; however, somata of mitral cells did not show NF-200 immunoreactivity. At this time point, strong NF-200-immunoreactive mitral cell processes ran to the EPL and glomerular layer (GL). Thereafter, NF-200 and RT97 immunoreactivity was decreased up to 30 days after ischemia. In the 15 days post-ischemic group, the distribution pattern of NF-200 and RT97 immunoreactivity was slightly lower than that in the 1-5 days post-ischemic groups. In the 30 days post-ischemic group, moderate NF-200 and RT97 immunoreactivity was found in the mitral cells processes, but the immunoreactivity in the EPL and GL nearly disappeared. A Western blot study showed a pattern of NF-200 and RT97 expression at all post-ischemic time points similar to that of immunohistochemistry after ischemia. This result indicates that NF-200 and RT97 accumulates in injured mitral cell processes a few days after transient ischemia, which suggests that the axonal transport in the MOB may be disturbed during this period after transient ischemia.

Treatment-responsive limbic encephalitis identified by neuropil antibodies: MRI and PET correlates.

We report seven patients, six from a single institution, who developed subacute limbic encephalitis initially considered of uncertain aetiology. Four patients presented with symptoms of hippocampal dysfunction (i.e. severe short-term memory loss) and three with extensive limbic dysfunction (i.e. confusion, seizures and suspected psychosis). Brain MRI and [(18)F]fluorodeoxyglucose (FDG)-PET complemented each other but did not overlap in 50% of the patients. Combining both tests, all patients had temporal lobe abnormalities, five with additional areas involved. In one patient, FDG hyperactivity in the brainstem that was normal on MRI correlated with central hypoventilation; in another case, hyperactivity in the cerebellum anticipated ataxia. All patients had abnormal CSF: six pleocytosis, six had increased protein concentration, and three of five examined had oligoclonal bands. A tumour was identified and removed in four patients (mediastinal teratoma, thymoma, thymic carcinoma and thyroid cancer) and not treated in one (ovarian teratoma). An immunohistochemical technique that facilitates the detection of antibodies to cell surface or synaptic proteins demonstrated that six patients had antibodies to the neuropil of hippocampus or cerebellum, and one to intraneuronal antigens. Only one of the neuropil antibodies corresponded to voltage-gated potassium channel (VGKC) antibodies; the other five (two with identical specificity) reacted with antigens concentrated in areas of high dendritic density or synaptic-enriched regions of the hippocampus or cerebellum. Preliminary characterization of these antigens indicates that they are diverse and expressed on the neuronal cell membrane and dendrites; they do not co-localize with VGKCs, but partially co-localize with spinophilin. A target autoantigen in one of the patients co-localizes with a cell surface protein involved in hippocampal dendritic development. All patients except the one with antibodies to intracellular antigens had dramatic clinical and neuroimaging responses to immunotherapy or tumour resection; two patients had neurological relapse and improved with immunotherapy. Overall, the phenotype associated with the novel neuropil antibodies includes dominant behavioural and psychiatric symptoms and seizures that often interfere with the evaluation of cognition and memory, and brain MRI or FDG-PET abnormalities less frequently restricted to the medial temporal lobes than in patients with classical paraneoplastic or VGKC antibodies. When compared with patients with VGKC antibodies, patients with these novel antibodies are more likely to have CSF inflammatory abnormalities and systemic tumours (teratoma and thymoma), and they do not develop SIADH-like hyponatraemia. Although most autoantigens await characterization, all share intense expression by the neuropil of hippocampus, with patterns of immunolabelling characteristic enough to suggest the diagnosis of these disorders and predict response to treatment.

Tripartite mushroom body architecture revealed by antigenic markers.

We have explored the organization of the axonal lobes in Drosophila mushroom bodies by using a panel of immunohistochemical markers. These markers consist of antibodies to eight proteins expressed preferentially in the mushroom bodies: DAMB, DCO, DRK, FASII, LEO, OAMB, PKA RII, and RUT. Previous to this work, four axonal lobes, two projecting dorsally (alpha and alpha') and two medially (beta and gamma), had been described in Drosophila mushroom bodies. However, our analysis of immunohistochemically stained frontal and sagittal sections of the brain revealed three medially projecting lobes. The newly distinguished lobe, which we term beta', lies along the dorsal surface of beta, just posterior to gamma. In addition to resolving a fifth lobe, our studies revealed that there are specific lobe sets defined by equivalent marker expression levels. These sets are (1) the alpha and beta lobes, (2) the alpha' and beta' lobes, and (3) the gamma lobe and heel (a lateral projection formed by a hairpin turn of some of the peduncle fibers). All of the markers we have examined are consistent with these three sets. Previous Golgi studies demonstrate that each mushroom body cell projects one axon that branches into a dorsal lobe and a medial lobe, or one unbranched axon that projects medially. Taken together with the lobe sets listed above, we propose that there are three major projection configurations of mushroom body cell axons: (1) one branch in the alpha and one in the beta lobe, (2) one branch in the alpha' and one in the beta' lobe, and (3) one unbranched axon projecting to the heel and the gamma lobe. The fact that these neuron types exhibit differential expression levels of a number of mushroom body genes suggests that they may have corresponding functional differences. These functions may be conserved in the larvae, as several of these genes were expressed in larval and embryonic mushroom bodies as well. The basic mushroom body structure, including the denritic calyx, peduncle, and lobes, was already visible by the late stages of embryogenesis. With new insights into mushroom body organization, and the characterization of markers for developing mushroom bodies, we are beginning to understand how these structures form and function.