Cell-mediated autoimmunity in paraneoplastic neurological syndromes with anti-Hu antibodies

No evidence for circulating HuD-specific CD8+ T cells in patients with paraneoplastic neurological syndromes and Hu antibodies

AIM

In paraneoplastic neurological syndromes (PNS) associated with small cell lung cancer (SCLC) and Hu antibodies (Hu-PNS), Hu antigens expressed by the tumour hypothetically trigger an immune response that also reacts with Hu antigens in the nervous system, resulting in tumour suppression and neuronal damage. To gain more insight into the hypothesized CD8(+ )T cell-mediated immune pathogenesis of these syndromes, we searched for circulating HuD-specific CD8(+) T cells in a large cohort of Hu-PNS patients and controls.

PATIENTS AND METHODS

Blood was tested from 43 Hu-PNS patients, 31 Hu antibody negative SCLC patients without PNS and 54 healthy controls. Peripheral blood mononuclear cells (PBMC) were stimulated with HuD protein-spanning peptide pools (15-mers) and individual HuD-derived peptides (9-mers) and analysed by cytokine flow cytometry and interferon-gamma ELISPOT-assays. Additionally, HuD-based Class I HLA multimers were used to visualize HuD-specific CD8(+) T cells.

RESULTS

No HuD-specific CD8(+ )T cells could be detected in the blood of Hu-PNS patients or controls.

CONCLUSIONS

Our results do not support a role for HuD-specific CD8(+) T cells in Hu-PNS. Further studies should focus on the detection of circulating HuD-specific CD4(+ )T cells and examine the antigen specificity of T cells in affected tissues.

An uncontrolled trial of rituximab for antibody associated paraneoplastic neurological syndromes

Anti-CD20 monoclonal antibody (rituximab) is effectively used in the treatment of B-cell lymphomas. Recent reports in the literature suggest that antibody associated autoimmune disorders may respond to rituximab. We therefore treated nine patients with anti-Hu or anti-Yo associated paraneoplastic neurological syndromes (PNS) with a maximum of four monthly IV infusions of rituximab (375mg/m(2)). In this uncontrolled, unblinded trial of rituximab, three patients improved > or =1 point on the Rankin Scale (RS). One patient with limbic encephalitis improved dramatically (RS from 5 to 1). Further studies of rituximab in autoantibody associated PNS are warranted.

Intravenous immunoglobulin therapy in paraneoplastic neurological syndromes

Combining clinical and immunological information, a neurological syndrome can now be diagnosed as a "definite" or "possible" paraneoplastic syndrome according to the newly suggested diagnostic criteria of the PNS Euronetwork. Differentiated diagnosis of a paraneoplastic syndrome is essential for differential therapy in patients. According to the response to IVIG therapy, paraneoplastic disorders may be subgrouped in group A, a clinical response is the rule (prototype Lambert-Eaton myasthenic syndrome), and in group B, IVIG may be helpful in single patients and is indicated in specific clinical settings (prototype anti-Hu associated neurological syndromes). The mode of action of IVIG may range from direct anti-idiotype effect to indirect effects on the cellular part of the pathogenesis of paraneoplastic syndromes. Due to the therapeutic relevance, it is therefore important to diagnose a PND as early as possible, and start immunotherapy including IVIG immediately.

Managing paraneoplastic neurological disorders

Paraneoplastic neurological syndromes (PNS) are remote effects of cancer that are not caused by invasion of the tumor or its metastases. Immunologic factors appear important in the pathogenesis of PNS because antineuronal autoantibodies and T-cell responses against nervous system antigens have been defined for many of these disorders. The immunologic response is elicited by the ectopic expression of neuronal antigens by the tumor. Expression of these so-called "onconeural" antigens is limited to the tumor and the nervous system and sometimes also the testis. At the time of presentation of the neurological symptoms, most patients have not yet been diagnosed with cancer. Detection of paraneoplastic antibodies is extremely helpful in diagnosing an otherwise unexplained and often rapidly progressive neurological syndrome as paraneoplastic. In addition, the paraneoplastic antibodies may also direct the search for an underlying neoplasm. On the other hand, in patients known to have cancer, the presentation of a PNS may herald recurrence of the tumor or a second tumor. The number of paraneoplastic antibodies is still growing, and at least seven of these can now be considered well characterized. Based on the clinical syndrome, the type of antibody, and the presence or absence of cancer, patients are classified as having a "definite" or "possible" PNS. Despite the presumed autoimmune etiology of PNS, the results of various forms of immunotherapy have been disappointing, with some exceptions. Rapid detection and immediate treatment of the underlying tumor appears to offer the best chance of stabilizing the patient and preventing further neurological deterioration.

T-cells in human encephalitis

Encephalitis literally means inflammation of the brain. In general, this inflammation can result from a viral or bacterial infection in the brain itself or alternatively from a secondary autoimmune reaction against an infection or a tumor in the rest of the body. Besides this, encephalitis is present in (believed autoimmune) diseases with unknown etiology, such as multiple sclerosis or Rasmussen encephalitis (RE). This article summarizes the existing data on the role of T-cells in the pathogenesis of three types of human encephalitis: RE, paraneoplastic encephalomyelitis, and virus encephalitis. In all of them, T-cells play a major role in disease pathogenesis, mainly mediated by major histocompatiblity complex class I-restricted CD8⁺ T-lymphocytes.

Functional characterisation of autoantibodies from patients with pediatric opsoclonus–myoclonus-syndrome

Paraneoplastic opsoclonus-myoclonus-syndrome (OMS) both in children and adults is suspected to be the result of an autoimmune response directed against cross-reactive proteins of tumor and neuronal cells. We here characterised the binding and functional activities of anti-neuroblastoma antibodies in IgG fractions from 11 OMS children with and without neuroblastoma. IgG fractions from neuroblastoma without OMS (NB) and healthy children served as controls. Indirect immunofluorescence and Western blot revealed IgG binding to intracellular autoantigens in all OMS patients, but in only one of the controls (p<0.001). Using flow cytometry, we could demonstrate surface binding of IgG fractions in all OMS patients, but only in one of control (p<0.001). Moreover OMS IgG exhibited a significant anti-proliferative and a cytotoxic effect on neuroblastoma cells compared to control IgG (p<0.001 and p<0.01). TUNEL assay revealed increased apoptotic cell death of the neuroblastoma cells after exposure to OMS IgG, but not to NB or control IgG (p<0.01). Preabsorption of membrane binding abandoned the anti-proliferative effect of OMS IgG. These findings indicate that surface-binding autoantibodies are present in OMS patients and these autoantibodies cause inhibition of cell proliferation and induce apoptosis.

Surface-binding autoantibodies to cerebellar neurons in opsoclonus syndrome

Childhood opsoclonus-myoclonus syndrome can occur with or without associated neuroblastoma. An autoimmune pathogenesis has been discussed for both forms. We show here that the majority of children with opsoclonus-myoclonus syndrome (10/14) have autoantibodies binding to the surface of isolated rat cerebellar granular neurons. In some patients, these antibodies are masked by IgG binding to ubiquitous surface antigens, which could be removed by preincubation with the nonneuronal control cell line HEK 293. A newly introduced competitive binding assay showed that the surface binding is directed against the same autoantigen in different patients. Therefore, we hypothesize that opsoclonus-myoclonus syndrome may be the result of an autoimmune process against a neuronal surface protein.

Sensory neuron diseases

Sensory neuron diseases (SND) are a distinct subgroup of peripheral-nervous-system diseases, first acknowledged in 1948. Acquired SND have a subacute or chronic course and are associated with systemic immune-mediated diseases, vitamin intoxication or deficiency, neurotoxic drugs, and life-threatening diseases such as cancer. SND are commonly idiopathic but can be genetic diseases; the latter tend to involve subtypes of sensory neurons and are associated with certain clinical pictures. The loss of sensory neurons in dorsal root ganglia causes the degeneration of short and long peripheral axons and central sensory projections in the posterior columns. This pathological process leads to a pattern of sensory nerve degeneration that is not length dependent and explains distinct clinical and neurophysiological abnormalities. Here we propose a comprehensive approach to the diagnosis of acquired and hereditary SND and discuss clinical, genetic, neurophysiological, neuroradiological, and neuropathological assessments.

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.

Association between the neuron-specific RNA-binding protein ELAVL4 and Parkinson disease

Inflammatory processes have been implicated in the cascade of events that lead to nerve cell death. In the nervous system, a number of genes involved in inflammation pathways are regulated post-transcriptionally via the interaction of their mRNAs with specific RNA-binding Hu proteins, the vertebrate homologues of the Drosophila ELAV (for embryonic lethal abnormal vision). The gene encoding ELAVL4, a member of the Hu family of proteins, is located 2 Mb from the chromosome 1p linkage region peak for age-at-onset (AAO) of Parkinson disease (PD) (LOD = 3.41). Nine single-nucleotide polymorphisms (SNPs) in ELAVL4 were genotyped for 266 multiplex families (1,223 samples). Additional genotyping in 377 singleton families was performed for a subset of five SNPs (SNPs 1-5) that were not in linkage disequilibrium. SNP 2 (located in the first intron of ELAVL4) showed a strong significant association with AAO of PD (P = 0.006), and SNP 5 (a coding SNP in ELAVL4) showed a moderately significant association (P = 0.035). Haplotype analysis revealed that the A-C haplotype at SNPs 2 and 3 has the strongest significant association with AAO (P = 0.0001) among all combinations of two or three loci. The A-C haplotype remained significant for AAO after the inclusion of the C allele at SNP 5 to this haplotype (A-C-C haplotype, P = 0.00018). Although SNP 5 was found to associate with PD risk in the early-onset subset of PD families (at least one affected with AAO <40 years, 60 families), we believe that it is a by-product of its association with AAO. Taken together, these results suggest a potential role for ELAVL4 as a modifier gene for AAO of PD.

Neuroimmunology of the paraneoplastic neurological degenerations

The paraneoplastic neurological degenerations (PNDs) are remarkable examples of naturally occurring tumor immunity in humans. In PND patients, common tumors such as breast, ovarian and lung tumors express proteins normally made exclusively in the brain, eliciting an immune response that successfully suppresses growth of the tumor. This successful anti-tumor response would be expected to go clinically unnoticed by the patient, but the immune cells mediating the response somehow cross into the brain, resulting in an autoimmune attack on neurons and neurological symptoms. Pieces of the mystery of this tumor immune response and neuronal autoimmunity have been assembled, but much more needs to be learned.

T cell response to Hu-D peptides in patients with anti-Hu syndrome

The anti-Hu syndrome is the most common paraneoplastic neurologic syndrome but the exact mechanism of immune mediated neuronal injury remains unknown. Anti-Hu antibodies do not appear to play a pivotal role in the pathogenesis of the disease. To assess cell-mediated immunity, we selected 51 peptides from the Hu-D sequence and tested their ability to bind to six common HLA class I molecules. Stable complexes with purified HLA molecules were obtained with 19/51 (37%) selected peptides. Subsequently, the ability of the 19 HLA-binding peptides to stimulate T cells from 10 patients and 10 control subjects was evaluated by detecting IFN-gamma secretion. An anti-peptide T-cell response was observed in 7/10 Hu-positive patients but also in 3/10 control subjects. Overall, a significant T-cell activation occurred in response to 74% (14 out of 19) of the selected peptides in the Hu-positive patients vs. 16% (3 out of 19) in the control group (p < 0.001). In addition, T cells of patients tested within 3 months of the onset of anti-Hu syndrome responded to 82% (14 out of 17) of assessed Hu-D peptides vs. 37% (7 out of 19) in patients tested 1 year or more after developing the syndrome (p < 0.01). Thus, the present study suggests a role of cellular immunity during the course of anti-Hu syndrome.

Gangliosides act as onconeural antigens in paraneoplastic neuropathies

We describe two patients with progressive neuropathy and lung cancer in whom gangliosides (GS) may represent the oncoantigens. Patient 1 had motor neuropathy, high titers of IgG1 and IgG3 to GD1a and GM1, and expansion of circulating gamma-delta T lymphocytes, a T-cell subset responding to glycolipids. Patient 2 presented with Miller-Fisher-like syndrome and IgG3 activity to disialo-GS. In both cases, decreased autoimmune responses and stabilization of neuropathy were accomplished by tumor treatment. By immunohistochemistry, patient 1's IgG bound to his own tumor and to structures of normal nervous system expressing GD1a or GM1. Infiltration of IgG in the same neural structures was found at his autopsy. Regarding cellular immunity, the proportion of gamma-delta T lymphocytes infiltrating carcinoma from patient 1 was significantly higher than in neoplastic controls. These results indicate that GS may represent onconeural antigens in paraneoplastic neuropathy (PNN); their expression on neoplastic tissue may elicit autoimmune responses, which also target neural structures.

Human enteric neuropathies: morphology and molecular pathology

The aim of this study is to review current understanding of the molecular and morphological pathology of the enteric neuropathies affecting motor function of the human gastrointestinal tract and to evaluate the described pathological entities in the literature to assess whether a new nosology may be proposed. The authors used PUBMED and MEDLINE searches to explore the literature pertinent to the molecular events and pathology of gastrointestinal motility disorders including achalasia, gastroparesis, intestinal pseudo-obstruction, colonic inertia and megacolon in order to characterize the disorders attributable to enteric gut neuropathies. This scholarly review has shown that the pathological features are not readily associated with clinical features, making it difficult for a patient to be classified into any specific category. Individual patients may manifest more than one of the morphological and molecular abnormalities that include: aganglionosis, neuronal intranuclear inclusions and apoptosis, neural degeneration, intestinal neuronal dysplasia, neuronal hyperplasia and ganglioneuromas, mitochondrial dysfunction (syndromic and non-syndromic), inflammatory neuropathies (caused by cellular or humoral immune mechanisms), neurotransmitter diseases and interstitial cell pathology. The pathology of enteric neuropathies requires further study before an effective nosology can be proposed. Carefully studied individual cases and small series provide the basic framework for standardizing the collection and histological evaluation of tissue obtained from such patients. Combined clinical and histopathological studies may facilitate the translation of basic science to the clinical management of patients with enteric neuropathies.

Les neuropathies périphériques paranéoplasiques

Paraneoplastic peripheral neuropathies constitute a heterogeneous group of conditions. A link between the tumor and the neuropathy has been demonstrated in a subgroup only. Definite paraneoplastic neuropathies correspond to neuropathies associated with antibodies reacting with antigens common to the peripheral nervous system and the cancer. Neuropathies associated with anti-Hu antibodies are the most frequent and consist mainly in subacute sensory neuronopathy. Sensory or sensory-motor neuropathies with anti-CV2 antibodies are less frequent. The link between the cancer and the neuropathy is less clear in the other forms. The frequency of cancer in this group varies from 1 to 18 p.cent.These neuropathies include inflammatory demyelinating neuropathies, neuropathy and vasculitis, lower motor neurone diseases, and autonomic neuropathies. Occasionally, the neuropathy improves with treatment of the tumor. Recent data suggest that gangliosides may be the target of the immune process in neuropathies associated with melanoma.

Peptides derived from the onconeural HuD protein can elicit cytotoxic responses in HHD mouse and human

Anti-Hu syndrome is a paraneoplastic neurologic disease seemingly associated with an efficient antitumoral immune response against HuD protein expressed by both small cell lung cancer (SCLC) and neurons. Since anti-Hu antibodies are not pathogenic, and oligoclonal CD8(+) T cells infiltrate neoplastic and nervous tissues, we examined MHC class I-restricted immunogenicity of human HuD. Among 14 HuD-derived peptides potentially immunogenic in HLA-A*0201 restriction, 10 had actual in vitro binding capacity to the HLA molecule, 8 elicited specific cytotoxic T lymphocytes (CTLs) in a humanized murine model after peptidic vaccination, 2 also elicited specific CTLs in healthy humans, and 1 was naturally processed and presented to the immune system.

Clinical features and pathophysiological basis of sensory neuronopathies (ganglionopathies)

Sensory ganglionopathies have a frequent association with neoplastic disorders (paraneoplastic subacute sensory neuronopathy, or SSN) or dysimmune disorders (Sjögren's syndrome, SS; Miller Fisher syndrome; and Bickerstaff's brainstem encephalitis, BBE), with drugs, such as cisplatin or pyridoxine, and with inherited disorders with degeneration of dorsal root ganglion cells. Unsteady gait and pseudoathetoid movements of the hand are the distinctive signs encountered in these disorders. The chronic disorders are characterized by non-length-dependent abnormalities of sensory nerve action potentials (SNAPs) and differ from other sensory neuropathies in showing a global, rather than distal, decrease in SNAP amplitudes. This review focuses on recent advances in defining the mechanisms involved in sensory ganglionopathies. Specific topics include a summary of their clinical features, pathological findings, and immunopathology. In SSN, early diagnosis by the detection of anti-Hu antibodies and early treatment of the cancer gives the best chance of stabilizing the disorder. In SS sensory ganglionitis, response to treatment has been disappointing, but immunomodulating treatments are emerging. The immunological profile common to BBE and Fisher syndrome supports a common pathogenesis. In toxic sensory neuronopathy, no treatment is available. The differential diagnosis involves separating sensory ganglionopathies from other ataxic polyneuropathies, such as infectious neuropathies, sensory neuropathies with various autoantibodies, and the neuropathies seen in celiac disease.

Anti-Hu paraneoplastic syndrome presenting with brainstem-cerebellar symptoms and Lambert-Eaton myasthenic syndrome

Paraneoplastic syndrome (PNS) with two distinct neurological features was reported in a 50-year-old man who presented initially with vertigo, ataxia, dysarthria, tremor, confusion, urinary retention and hypotension. Pulmonary X-ray findings, class IIIb sputum cytology, and positive anti-Hu antibody established the diagnosis of PNS associated with small-cell lung cancer (SCLC). Two cycles of combined chemotherapy resulted in shrinkage of the lung tumor together with complete recovery of neurological symptoms and disappearance of anti-Hu antibody. Relapse of SCLC 4 months later with re-appearance of anti-Hu antibody required additional chemotherapy and irradiation. Eight months later, when multiple liver metastasis of SCLC was noticed, muscular weakness with positive waxing phenomenon compatible with Lambert-Eaton myasthenic syndrome (LEMS) developed. Postmortem examinations revealed residual SCLC in the primary lung, and massive liver metastasis with generalized lymph node involvement, but no tumors in the CNS. In the cerebellum, there was a slight loss of Purkinje cells with torpedo formation but without apparent lymphocytic infiltration. The present PNS was unique in that the relapse of SCLC was accompanied by the appearance of anti-Hu antibody, and that initial signs of brainstem-cerebellar symptoms, encephalopathy and autonomic failure were replaced by LEMS coinciding with the tumor recurrence.

Paraneoplastic cerebellar degeneration associated with antineuronal antibodies: analysis of 50 patients

Paraneoplastic cerebellar degeneration (PCD) is a heterogeneous group of disorders characterized by subacute cerebellar ataxia, specific tumour types and (often) associated antineuronal antibodies. Nine specific antineuronal antibodies are associated with PCD. We examined the relative frequency of the antineuronal antibodies associated with PCD and compared the neurological symptoms and signs, associated tumours, disability and survival between groups of PCD with different antibodies. Also, we attempted to identify patient-, tumour- and treatment-related characteristics associated with functional outcome and survival. In a 12-year period, we examined >5000 samples for the presence of antineuronal antibodies. A total of 137 patients were identified with a paraneoplastic neurological syndrome and high titre (> or =400) antineuronal antibodies. Fifty (36%) of these patients had antibody-associated PCD, including 19 anti-Yo, 16 anti-Hu, seven anti-Tr, six anti-Ri and two anti-mGluR1. Because of the low number, the anti-mGluR1 patients were excluded from the statistical analysis. While 100% of patients with anti-Yo, anti-Tr and anti-mGluR1 antibodies suffered PCD, 86% of anti-Ri and only 18% of anti-Hu patients had PCD. All patients presented with subacute cerebellar ataxia progressive over weeks to months and stabilized within 6 months. The majority of patients in all antibody groups had both truncal and appendicular ataxia. The frequency of nystagmus and dysarthria was lower in anti-Ri patients (33 and 0%). Later in the course of the disease, involvement of non-cerebellar structures occurred most frequently in anti-Hu patients (94%). In 42 patients (84%), a tumour was detected. The most commonly associated tumours were gynaecological and breast cancer (anti-Yo and anti-Ri), lung cancer (anti-Hu) and Hodgkin's lymphoma (anti-Tr and anti-mGluR1). In one anti-Hu patient, a suspect lung lesion on CT scan disappeared while the PCD evolved. Seven patients improved by at least 1 point on the Rankin scale, while 16 remained stable and 27 deteriorated. All seven patients that improved received antitumour treatment for their underlying cancer, resulting in complete remission. The functional outcome was best in the anti-Ri patients, with three out of six improving neurologically and five were able to walk at the time of last follow-up or death. Only four out of 19 anti-Yo and four out of 16 anti-Hu patients remained ambulatory. Also, survival from time of diagnosis was significantly worse in the anti-Yo (median 13 months) and anti-Hu (median 7 months) patients compared with anti-Tr (median >113 months) and anti-Ri (median >69 months). Patients receiving antitumour treatment (with or without immunosuppressive therapy) lived significantly longer [hazard ratio (HR) 0.3; 95% confidence interval (CI) 0.1-0.6; P = 0.004]. Patients > or =60 years old lived somewhat shorter from time of diagnosis, although statistically not significant (HR 2.9; CI 1.0-8.5; P = 0.06).

Paraneoplastic neurologic syndromes

Cancer can affect the nervous system through many metastatic and nonmetastatic mechanisms, including side effects of cancer treatment, infections, coagulopathy, and metabolic or nutritional deficits. Paraneoplastic neurologic disorders (PND) are an extensive group of syndromes that cannot be explained by any of these complications and may affect any part of the nervous system. PND often develop before the presence of a cancer is known and their recognition may lead to the tumor diagnosis.

Current Therapies for Paraneoplastic Neurologic Syndromes

Paraneoplastic neurologic syndromes (PNS) comprise an extensive group of heterogeneous disorders that can affect any part of the central and peripheral nervous system. There is evidence that many of these disorders are mediated by immunologic responses triggered by the presence of a cancer. Several immunologic mechanisms and many antigenic targets have been related to these disorders. Some disorders of the neuromuscular junction or peripheral nervous system are directly mediated by antibodies, and they may have a paraneoplastic origin or develop without a tumor association. For these disorders and a few PNS of the central nervous system, immunotherapy may result in neurologic improvement. However, for most PNS of the peripheral and central nervous system the response to any type of therapy is, in general, disappointing. The main concern of the clinician should be to rule out other diagnostic entities and to uncover the presence of the associated neoplasm that often remains elusive to detection. In general, the best approach to treat PNS is to discover and treat the tumor promptly, and provide supportive care for the neurologic deficits with symptomatic treatment and physical therapy. In a few cases, depending on the syndrome and if the patient is in the early stages of the neurologic disease, treatment with immunosuppression may have some effect on the PNS.

Role of enteric glial cells in inflammatory bowel disease

Enteric glial cells (EGCs) represent an extensive but relatively poorly described cell population within the gastrointestinal tract. Accumulating data suggest that EGCs represent the morphological and functional equivalent of CNS astrocytes within the enteric nervous system (ENS). The EGC network has trophic and protective functions toward enteric neurons and is fully implicated in the integration and the modulation of neuronal activities. Moreover, EGCs seem to be active elements of the ENS during intestinal inflammatory and immune responses, sharing with astrocytes the ability to act as antigen-presenting cells and interacting with the mucosal immune system via the expression of cytokines and cytokine receptors. Transgenic mouse systems have demonstrated that specific ablation of EGC by chemical ablation or autoimmune T-cell targeting induces an intestinal pathology that shows similarities to the early intestinal immunopathology of Crohn's disease. EGCs may also share with astrocytes the ability to regulate tissue integrity, thereby postulating that similar interactions to those observed for the blood-brain barrier may also be partly responsible for regulating mucosal and vascular permeability in the gastrointestinal tract. Disruption of the EGC network in Crohn's disease patients may represent one possible cause for the enhanced mucosal permeability state and vascular dysfunction that are thought to favor mucosal inflammation.

Immunization with a cannabinoid receptor type 1 peptide results in experimental allergic meningocerebellitis in the Lewis rat: A model for cell-mediated autoimmune neuropathology

Neuronal elements are increasingly suggested as primary targets of an autoimmune attack in certain neurological and neuropsychiatric diseases. Type 1 cannabinoid receptors (CB1) were selected as autoimmune targets because they are predominantly expressed on neuronal surfaces in brain and display strikingly high protein levels in striatum, hippocampus, and cerebellum. Female Lewis rats were immunized with N-terminally acetylated peptides (50 or 400 microg per rat) of the extracellular domains of the rat CB1 and killed at various time points. Subsequent evaluation using immunohistochemistry and in situ hybridization showed dense infiltration of immune cells exclusively within the cerebellum, peaking 12-16 days after immunization with the CB1 peptide containing amino acids 9-25. The infiltrates clustered in meninges and perivascular locations in molecular and granular cell layers and were also scattered throughout the CB1-rich neuropil. They consisted primarily of CD4(+) and ED1(+) cells, suggestive of cell-mediated autoimmune pathology. There were no inflammatory infiltrates elsewhere in the brain or spinal cord. The results show that neuronal elements, such as neuronal cell-surface receptors, may be recognized as antigenic targets in a cell-mediated autoimmune attack and, therefore, support the hypothesis of cell-mediated antineuronal autoimmune pathology in certain brain disorders.

Cytotoxic T cell activity against peptides of Hu protein in anti-Hu syndrome

Half of all patients with limbic encephalitis and small cell lung carcinoma (SCLC) have anti-Hu antibodies that react with all of central and peripheral nervous system neuronal nuclei in immunohistochemical studies and 35- to 40-kDa reactive bands on western blots of extracts from isolated central nervous system neurons. The roles of anti-Hu antibodies in neuronal damage, however, have yet to be shown. Evidence of infiltration of CD8-positive T cells to tumors and affected nervous tissues and limited use of the T cell receptor repertoire in the central nervous system suggests that CD8-positive cytotoxic T cells (CTL) cause neuronal loss. We found the HLA B7 supertype in all of seven Japanese patients with anti-Hu syndrome. We identified HLA class I-restricted, CD 8-positive cytotoxic T cell activity in peripheral blood from three patients with anti-Hu syndrome for five peptides with binding motifs for the HLA B7 supertype in the amino acid sequence of the Hu protein. This study support the involvement of CD8-positive cytotoxic T cells in the development of paraneoplastic neurological syndrome with anti-Hu antibodies.

Paraneoplastic neurological syndromes: an update on diagnosis, pathogenesis, and therapy

Since the discovery of the first clinically relevant anti neuronal antibody specific for a paraneoplastic aetiology in 1985, the number of such reactivities has grown at a rate of about one per year. Clinicians can now diagnose a paraneoplastic syndrome much more easily. This ability is especially important because, typically, the neurological symptoms occur before the cancer is diagnosed. Early tumour diagnosis is essential, because effective treatment of the cancer still seems to be the most efficient treatment option for the neurological symptoms. Immuno modulatory therapy should, nevertheless, be initiated as early as possible and seems especially helpful for peripheral syndromes and limbic encephalitis. The recent fundamental advances in understanding of the autoimmune pathology of these disorders, especially the role of cytotoxic T cells, should eventually lead to more effective treatment options.

Immunotherapeutic approaches to paraneoplastic neurological disorders

The review presents an overview on the pathogenesis of paraneoplastic neurological disorders (PNDs) and the current therapeutic immunosuppressive or immunomodulatory strategies used in these patients. PNDs are disturbances in the functioning of the nervous system in cancer patients, where the disturbances are not due to a local effect of the tumour or its metastases. Most of these clinically, well-defined syndromes in adults are associated with lung cancer (especially small cell lung cancer), lymphomas and gynaecological tumours. Since autoantibodies directed against proteins expressed in neurons and tumour cells have been found, PNDs are suspected to be autoimmune. In neuromuscular PND, immunosuppressive therapies, plasmapheresis and intravenous immunoglobulins are effective treatments. In contrast, central nervous system PNDs seen in adults are by far the most problematic group to treat. With exception of the stiff-man syndrome, immunosuppression appears to have little effect on these neurological disorders. Tumour therapy stabilises PNDs but does not cause improvement. Plasmapheresis reduces the autoantibody titre in the sera of these patients but, like tumour therapy, does not lead to a clinical improvement. In children with paraneoplastic opsoclonus-myoclonus syndrome, steroids and intravenous immunoglobulins may lead to a complete or partial remission of PNDs.

Remote neurologic manifestations of cancer

Paraneoplastic disorders may affect any part of the central or peripheral nervous systems. Although relatively uncommon, these disorders are a significant cause of neurologic morbidity for cancer patients. At least some paraneoplastic syndromes are believed to be caused by an autoimmune reaction against shared tumor-neural antigens. This article summarizes the clinical features of paraneoplastic disorders, the current evidence for autoimmunity, and guidelines for diagnosis and treatment.

Oligoclonal T-cells in blood and target tissues of patients with anti-Hu syndrome

T-cell clones of unknown significance (TCUS), assessed by monoclonal or oligoclonal T-cell patterns in PCR-DGGE, were detected in blood of 7/9 patients with anti-Hu syndrome. Clonal patterns were also detected in 2/2 neoplastic lymph nodes, and in 2/2 inflamed dorsal root ganglia from three patients. Only some T-cell clones found in target tissues were also detected in blood or non-target tissues, and likely corresponded to TCUS. In one patient, an identical T-cell clone was found in both neoplastic lymph node tissue and dorsal root ganglia, but not in blood. Dorsal root-infiltrating lymphocytes were cytotoxic CD8(+) TIA-1(+) T-cells. They were often found in close contact to sensory neurons, most of which expressed MHC-1. Taken together, these data support a direct effector role of cytotoxic CD8(+) T-cells, the same clones being likely operative in sensory neuron damage and immune-mediated tumor growth control.

The clinical spectrum and pathogenesis of paraneoplastic disorders of the central nervous system

Paraneoplastic neurologic disorders (PND) refer to neurologic disorders of unknown cause that occur at higher frequency in patients with cancer than in the general population. There is increasing evidence that many of these disorders are immune mediated and associated with cytotoxic antitumor immunity. The identification of the immune responses in these patients facilitates the diagnosis of the PND and has led to the cloning and characterization of the target antigens in the nervous system and tumor.

Enterocolitis induced by autoimmune targeting of enteric glial cells: a possible mechanism in Crohn's disease?

Early pathological manifestations of Crohn's disease (CD) include vascular disruption, T cell infiltration of nerve plexi, neuronal degeneration, and induction of T helper 1 cytokine responses. This study demonstrates that disruption of the enteric glial cell network in CD patients represents another early pathological feature that may be modeled after CD8(+) T cell-mediated autoimmune targeting of enteric glia in double transgenic mice. Mice expressing a viral neoself antigen in astrocytes and enteric glia were crossed with specific T cell receptor transgenic mice, resulting in apoptotic depletion of enteric glia to levels comparable in CD patients. Intestinal and mesenteric T cell infiltration, vasculitis, T helper 1 cytokine production, and fulminant bowel inflammation were characteristic hallmarks of disease progression. Immune-mediated damage to enteric glia therefore may participate in the initiation and/or the progression of human inflammatory bowel disease.

Cancer and autoimmunity: autoimmune and rheumatic features in patients with malignancies

OBJECTIVES

To review the autoimmune and rheumatic manifestations of patients with malignancy.

METHODS

A Medline search of all published papers using keywords related to malignancies, autoimmunity, rheumatic diseases, and paraneoplastic syndromes.

RESULTS

Patients with malignant diseases may develop autoimmune phenomena and rheumatic diseases as a result of (a) generation of autoantibodies against various autoantigens, including oncoproteins (P185, 1-myc, c-myc, c-myb), tumour suppression genes (P53), proliferation associated antigens (cyclin A, B1, D1, E; CENP-F; CDK, U3-RNP), onconeural antigens (Hu, Yo, Ri, Tr), cancer/testis antigens (MAGE, GAGE, BAGE, SSX, ESO, SCP, CT7), and rheumatic disease associated antigens (RNP, Sm). The clinical significance of the various autoantibodies is not clear. Anti-oncoprotein and anti-tumour suppression gene antigens are detected before the diagnosis of the cancer or in the early stages of the malignant disease, suggesting a potential diagnostic or prognostic role. Anti-onconeural antibodies are pathogenic and are associated with specific clinical neurological syndromes (anti-Hu syndrome and others). (b) Paraneoplastic syndromes, a wide range of clinical syndromes, including classic autoimmune rheumatic diseases that develop among patients with cancer. (c) Rheumatism after chemotherapy, a clinical entity characterised by the development of musculoskeletal symptoms after combination chemotherapy for malignancy.

CONCLUSION

Autoimmune and rheumatic features are not rare among patients with malignancies. They are the result of various diverse mechanisms and occasionally they may be associated with serious clinical entities.

Restricted IgG1 subclass of anti-Yo antibodies in paraneoplastic cerebellar degeneration

Paraneoplastic cerebellar degeneration (PCD) occurs as a non-metastatic manifestation of cancer in a small proportion of patients with certain breast or gynaecological tumours, and is characterised by widespread Purkinje cell loss. Antibodies against a Purkinje cell cytoplasmic antigen, called Yo, that is expressed by the tumours, are present in the majority of these patients, but the pathogenic role of the antibodies is not clear. To characterise further the immune response in these cases, 13 anti-Yo positive sera were tested for IgG subclasses by immunohistochemistry and western blotting and, in four cases, PHA-stimulated cytokine secretion by peripheral blood lymphocytes was measured. Surprisingly, anti-Yo antibodies were entirely restricted to the IgG1 subclass, whereas antibodies against the small cell cancer-associated antigen, Hu, were found in all four IgG subclasses. There was a trend towards raised IgG1 levels in the total IgG of the anti-Yo positive patients and, in two, PHA-stimulated peripheral blood lymphocytes secreted raised levels of IFN-gamma. By contrast, in the other two cases tested, raised levels of IL-4 were secreted. Patients with PCD associated with anti-Yo antibodies appear to have strong immune responses that are polarised with respect to the IgG subclass and Th cytokine profiles.

Antibody types and IgG subclasses in paraneoplastic neurological syndromes

Three major patterns of antineuronal antibody response have been identified in patients with paraneoplastic neurological syndromes: Type I ('Anti-Yo'), associated with cerebellar degeneration in the setting of breast or gynecological cancer, Type IIa ('anti-Hu') associated with encephalomyeloneuritis in patients with small cell carcinoma of the lung, and Type IIb ('anti-Ri') associated with breast cancer. We have employed immunofluorescence methods to determine the antibody classes and the IgG subclasses which react with neurons in each of these patterns of paraneoplastic antibody response. In this study, IgG was the only antibody class identified; IgM and IgA antibodies were not found. IgG1 was the major subclass represented and was found in 9/9 patients with Type I antibody response, 26/27 patients with Type IIa antibody response, and 3/3 patients with Type IIb antibody response. Many patients also exhibited positive staining for IgG2 and IgG3. Trace amounts of IgG4 antineuronal antibodies were detected in a single patient with Type I antibody response; IgG4 antibodies were not found in other patients. Patients with paraneoplastic neurological syndromes exhibit an antibody response which is overwhelmingly IgG and is comprised predominantly of IgG subclasses capable of fixing complement. The role of these antibodies in the pathogenesis of paraneoplastic neurological disease remains uncertain.

Chronic multiple paraneoplastic syndromes

A patient presented with symptoms of limbic and brainstem encephalitis, motor and sensory neuronopathy, cerebellar dysfunction, and highly positive anti-Hu antibodies. He also harbored P/Q-type calcium channel antibodies and manifested the Lambert-Eaton myasthenic syndrome (LEMS). Small-cell lung cancer was found, and he received both antineoplastic therapy and intravenous immunoglobulin (IVIg). Remission of the malignancy was achieved. Although the anti-Hu-related manifestations improved after therapy, LEMS has persisted, leading to IVIg dependency.

Pathogenetic role of autoantibodies in neurological diseases

Autoreactive B cells and antibodies can be detected in a variety of neurological diseases. Their causative role has been established in some disorders and they are obviously involved in the pathogenesis of others. Some mechanisms engendering B-cell autoimmunity in animal models have been shown to operate in humans. Factors that determine B-cell immune-response patterns and the effector pathways have been identified. B-cell responses to CNS-restricted autoantigens are governed by distinctive immune reactions. Evidence has accumulated that the CNS is a permissive and, under inflammatory conditions, even a B-cell-supporting micro-environment. Data from human and animal experiments have enhanced our understanding of B-cell physiology in health and neurological disease, which has relevant diagnostic and therapeutic implications.

Paraneoplastic syndromes: an unsolved murder

With neuroimmunology playing an ever greater role in child neurology, paraneoplastic syndromes--uncommon but often devastating complications of cancer--are in the forefront. Abnormalities of both humoral and cellular immunity support the immunological theory of causation. Through co-complicity of host and tumor factors, targets of immunologically mediated injury remote from the tumor may be damaged or destroyed, giving rise to discrete neurological deficits. In the nervous system, the main targets are neuronal nuclei or cell bodies, structural constituents, surface receptors, synapses, and ion channels. The clinical syndromes and response to treatment differ substantially between children and adults. Current pharmacological and biological therapies, which are nonselective, include noncytotoxic and cytotoxic drugs, intravenous immunoglobulins, plasma exchange, and immunoadsorption, some chosen for induction and others for maintenance. Tumor resection and thymectomy are surgical treatments. Combination immunotherapies allow steroid sparing, targeting of more than one immunologic effector pathway, and deploy an advantageous mixture of early- and late-acting drugs. More selective and efficacious immunotherapies are needed.

Autoantibodies in paraneoplastic neurological syndrome

Paraneoplastic neurological syndrome is a rare disorder caused by the secondary effects of cancer and is thought to be immune-mediated. A high titer of autoantibodies in the patient's serum and cerebrospinal fluid, directed against both neurons and tumor, have been detected in some forms of this syndrome. These autoantibodies are considered the result of an immunological response to tumor and may cross-react with cells of the nervous system, causing neuronal damage. Specific forms of this syndrome are often associated with specific antineuronal antibodies and tumors. The onset of neurological symptoms and detection of these antibodies often precede the diagnosis of the tumor; therefore, detection of these antibodies greatly assists the diagnosis of this syndrome and prompts investigations for the underlying tumor. The pathogenicity of these antineuronal antibodies has been proven in only a few cases, such as that of anti-voltage gated calcium-channel antibodies in Lambert-Eaton myasthenic syndrome. The selective involvement of specific types of neurons has not been fully elucidated. The target spectrum of some of these antineuronal antibodies correlates well with the neurological symptoms, but that of others is wider than expected from the symptoms. Interesting evidence has suggested that these antionconeuronal antibodies can suppress tumor growth. The discovery of new antibodies and characterization of target molecules have been reported with advances in the field of molecular biology. A more detailed understanding of the relationship between the cancer and the neural involvement from the molecular biological standpoint may lead to rational tumor therapy and elucidation of the mechanism of neuronal death. Here, major clinical forms with well-known antineuronal antibodies and specific tumors are reviewed; for each antineuronal antibody, the target antigens and its putative role in the pathogenesis of this syndrome are described.

Autoimmune and antitumor consequences of antibodies against antigens shared by normal and malignant tissues

There is now a considerable body of information documenting the autoimmune consequences of antibodies induced by growing malignancies, or by passively administered and actively induced antibodies, in cancer patients against antigens shared by normal and malignant tissues. This provides a rich source of information addressing the consequences of autoantibodies against a range of antigens. Antibodies against cell-surface or intracellular antigens in the central nervous system (CNS) or on epithelial surfaces of normal tissues do not generally result in autoimmunity, but the same types and titers of antibodies against cell surface antigens in the subepidermal skin, peripheral nerves, blood, or vascular sites such as the spleen and bone marrow readily induce autoimmunity. The blood brain barrier of the CNS and apical antigen expression and the basement membrane in epithelial tissues, may protect these sites from antibody induced damage. Cancer cells, however, are protected by neither unidirectional antigen expression nor basement membranes. Vaccine induced antibodies against a variety of cancer cell surface antigens have been associated with prevention of tumor recurrence in preclinical models and in vaccinated cancer patients, in the absence of demonstrable autoimmunity. This forms the basis for a series of ongoing Phase III trials with single or polyvalent antigen cancer vaccines designed for optimal antibody induction.

Gene Therapy for Lung Cancer

Gene therapy is emerging as a promising modality for the treatment of lung cancer. Diverse strategies employing gene therapy for lung cancer have been investigated in vitro and in animal models, and a number of these approaches have met with promising results. Several phase I and II clinical trials have been undertaken, and early results suggest that it may be safe to administer gene therapy to lung cancer patients. It remains to be determined whether this modality will be efficacious as primary or adjunctive therapy in the setting of lung cancer.

Reversible paraneoplastic encephalomyelitis associated with a benign ovarian teratoma

BACKGROUND

Paraneoplastic encephalomyelitis (PEM) is a well characterized, and typically irreversible, paraneoplastic syndrome, usually associated with small cell lung cancer or other malignancy. We describe a case of a young woman with a benign ovarian teratoma who presented with a reversible PEM.

CASE REPORT

A 24-year-old woman presented with a three week history of memory impairment, unusual behavior, personality changes, auditory hallucinations, hypersomnolence and binocular biplopia. On admission she was disoriented and inattentive with impaired short term memory. Small doses of lorazepam (1 mg), given for episodic agitation, repeatedly induced multidirectional bilateral nystagmus and a skew deviation, but her neurological examination was otherwise normal. A left-sided pelvic mass was palpable. Brain MRI pre- and post-gadolinium was normal. There was a mild CSF pleocytosis and an EEG showed minimal bilateral background activity irregularities. There were no other laboratory abnormalities. Two weeks after admission, she clinically deteriorated developing central respiratory failure and a flaccid paraplegia. Repeat MRI showed an area of increased T2 weighted signal in the medulla and three similar areas in the spinal cord. Following removal of her tumor, treatment with high dose corticosteroids and intravenous immunoglobulin, she ultimately made a full recovery. Pathology revealed the tumor to be a benign ovarian cystic teratoma.

CONCLUSIONS

This is the first report of a reversible PEM seen in association with a benign tumor, in this case a mature ovarian teratoma. Presumably, an immune response directed against neural clements of the teratoma cross-reacted with normal brain, brainstem and spinal cord antigens to cause neurologic symptoms. Tumor removal was followed by neurologic recovery.

Paraneoplastic neuropathy

Paraneoplastic neuropathies occur in various settings. This article focuses on recent neuroimmunologic findings regarding paraneoplastic neuropathy. Entities such as sensorimotor and sensory neuropathy, sensory neuronopathy; motor, autonomic, demyelinating and vasculitic mononeuropathies; and cranial nerve lesions and neuropathies in association with leukaemia and paraproteinaemas are discussed. Finally, the article considers the issue of 'overlap' syndromes--the occurrence of several paraneoplastic phenomena in the same patient.