Temporal evolution of nerve conduction study abnormalities in anti-myelin-associated glycoprotein neuropathy.

BACKGROUND: A distal-predominant demyelinating symmetric pattern is most frequent in patients with neuropathy associated with anti-myelin-associated glycoprotein (MAG) antibodies. The literature however lacks longitudinal data to describe whether this is consistent over time. METHODS: From the Ottawa Neuromuscular Center database, we identified 23 patients with both immunoglobulin M gammopathy and anti-MAG antibodies. For median, ulnar and fibular motor conduction studies, we analyzed distal latency and amplitude, negative peak duration, terminal latency index (TLI), and conduction velocity. For median, ulnar, sural, and superficial fibular sensory conduction studies, we analyzed distal latency and amplitude. Results were compared for the earliest and the latest data sets. RESULTS: The mean time interval between the two assessment points was 6.5 years. Median and ulnar motor nerve conduction studies did not show a significant change for any of the parameters tested. There was disproportionate prolongation of median distal motor latency and reduction in TLI, compared to the ulnar nerve. Deep fibular motor conduction studies showed a marked reduction in amplitudes over time. Sensory potentials were recordable in the upper limb in less than 50% at the first study and less than 25% on the most recent study. There was an even larger attrition of recordable sural and superficial fibular sensory potentials. CONCLUSIONS: Our results highlight the stability of median and ulnar motor conduction study results over a mean observation period of 6.5 years. In contrast, lower limb motor and all sensory potentials show a marked trend toward becoming unrecordable.

Selective in vivo removal of pathogenic anti-MAG autoantibodies, an antigen-specific treatment option for anti-MAG neuropathy.

Anti-MAG (myelin-associated glycoprotein) neuropathy is a disabling autoimmune peripheral neuropathy caused by monoclonal IgM autoantibodies that recognize the carbohydrate epitope HNK-1 (human natural killer-1). This glycoepitope is highly expressed on adhesion molecules, such as MAG, present in myelinated nerve fibers. Because the pathogenicity and demyelinating properties of anti-MAG autoantibodies are well established, current treatments are aimed at reducing autoantibody levels. However, current therapies are primarily immunosuppressive and lack selectivity and efficacy. We therefore hypothesized that a significant improvement in the disease condition could be achieved by selectively neutralizing the pathogenic anti-MAG antibodies with carbohydrate-based ligands mimicking the natural HNK-1 glycoepitope 1. In an inhibition assay, a mimetic (2, mimHNK-1) of the natural HNK-1 epitope blocked the interaction of MAG with pathogenic IgM antibodies from patient sera but with only micromolar affinity. Therefore, considering the multivalent nature of the MAG-IgM interaction, polylysine polymers of different sizes were substituted with mimetic 2. With the most promising polylysine glycopolymer PL84(mimHNK-1)45 the inhibitory effect on patient sera could be improved by a factor of up to 230,000 per epitope, consequently leading to a low-nanomolar inhibitory potency. Because clinical studies indicate a correlation between the reduction of anti-MAG IgM levels and clinical improvement, an immunological surrogate mouse model for anti-MAG neuropathy producing high levels of anti-MAG IgM was developed. The observed efficient removal of these antibodies with the glycopolymer PL84(mimHNK-1)45 represents an important step toward an antigen-specific therapy for anti-MAG neuropathy.

Immunotherapy-responsive allodynia due to distal acquired demyelinating symmetric (DADS) neuropathy.

INTRODUCTION: Distal acquired demyelinating symmetric (DADS) neuropathy is a distal variant of chronic inflammatory demyelinating polyradiculoneuropathy. It is characterized by chronic distal symmetric sensory or sensorimotor deficits. Sensory ataxia is a common clinical presentation. Nerve conduction studies typically show markedly prolonged distal motor latencies. METHODS: We report 2 patients with chronic progressive generalized pain and fatigue, with normal neurological examinations except for allodynia. RESULTS: Nerve conduction studies were typical of DADS neuropathy. Monoclonal protein studies were negative. Cerebrospinal fluid protein levels were elevated. Sural nerve biopsies revealed segmental demyelination and remyelination. One biopsy had marked endoneurial and epineurial lymphocytic infiltration. Immunomodulatory therapy alleviated the pain and fatigue and markedly improved distal motor latencies in both patients. CONCLUSIONS: DADS neuropathy can present with pain and a normal neurological examination apart from allodynia. Nerve conduction studies are necessary for diagnosis. These patients respond to immunotherapy better than typical DADS neuropathy patients with sensory ataxia. Muscle Nerve 54: 973-977, 2016.

Destruction of paranodal architecture in inflammatory neuropathy with anti-contactin-1 autoantibodies.

OBJECTIVE: Autoantibodies against paranodal proteins have been described in patients with inflammatory neuropathies, but their association with pathology of nodes of Ranvier is unclear. We describe the clinical phenotype and histopathological changes of paranodal architecture of patients with autoantibodies against contactin-1, identified from a cohort with chronic inflammatory demyelinating polyradiculoneuropathy (n=53) and Guillain-Barré syndrome (n=21). METHODS: We used ELISA to detect autoantibodies against contactin-1. Specificity of the autoantibodies was confirmed by immunoblot assay, binding to contactin-1-transfected human embryonic kidney cells, binding to paranodes of murine teased fibres and preabsorption experiments. Paranodal pathology was investigated by immunofluorescence labelling of dermal myelinated fibres. RESULTS: High reactivity to contactin-1 by ELISA was found in four patients with chronic inflammatory demyelinating polyradiculoneuropathy and in none of the patients with Guillain-Barré syndrome, which was confirmed by cell binding assays in all four patients. The four patients presented with a typical clinical picture, namely acute onset of disease and severe motor symptoms, with three patients manifesting action tremor. Immunofluorescence-labelling of paranodal proteins of dermal myelinated fibres revealed disruption of paranodal architecture. Semithin sections showed axonal damage but no classical signs of demyelination. INTERPRETATION: We conclude that anti-contactin-1-related neuropathy constitutes a presumably autoantibody-mediated form of inflammatory neuropathy with distinct clinical symptoms and disruption of paranodal architecture as a pathological correlate. Anti-contactin-1-associated neuropathy does not meet morphological criteria of demyelinating neuropathy and therefore, might rather be termed a 'paranodopathy' rather than a subtype of demyelinating inflammatory neuropathy.

Nerve ultrasound findings in neuropathy associated with anti-myelin-associated glycoprotein antibodies.

BACKGROUND AND PURPOSE: No systematic nerve ultrasound (US) studies on patients with neuropathy and anti-myelin-associated glycoprotein (anti-MAG) antibodies are available. PATIENTS AND METHODS: Twenty-eight patients (18 men, 10 women, mean age 69.2 ± 10.9 years; mean disease duration 6.9 years) with anti-MAG neuropathy underwent nerve US. Echotexture, nerve cross-sectional area (CSA) and intra-nerve and inter-nerve CSA variability were assessed. The frequency (number of nerves with enlarged CSA, 'enlarged nerves sum score') and distribution (proximal versus distal, arms versus legs, symmetry) of US abnormalities were considered. Controls included two groups: four patients with immunoglobulin M (IgM) paraproteinaemic neuropathy without anti-MAG antibodies and five with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) associated with IgM paraprotein. RESULTS: In all, 26/28 patients had increased CSA (23 with at least one nerve outside entrapment sites). Intra-nerve CSA variability was abnormal in 21/28 patients (in 14 for increased nerve CSA outside entrapment sites). Inter-nerve CSA variability was abnormal in 16 patients (of whom half for CSA increase out of entrapment sites). The enlarged nerves sum score in anti-MAG neuropathy patients was greater than in MAG-negative paraproteinaemic neuropathies and lower than in CIDP. Intra-nerve variability appeared instead similar in anti-MAG and controls. No correlation was found between US findings and Inflammatory Neuropathy Cause and Treatment Group (INCAT) disability score or disease duration. DISCUSSION: Amongst the different measures to assess the US pattern (symmetry/asymmetry, proximal/distal distribution and sum score), the enlarged nerves sum score was the most useful for differentiating the three groups of patients with demyelinating neuropathies and may contribute to diagnosis in a typical cases.

Distinct lymphocytes subsets in IgM-related neuropathy: clinical-immunological correlations.

IgM-related neuropathy generally presents as a late-onset demyelinating polyneuropathy with predominant sensory loss and ataxia. However, we recently reported the clinical, neurophysiological and pathological findings from our cohort and identified in about a third of patients an atypical phenotype. We analyzed by flow cytometry the different lymphocytes subsets in the peripheral blood of patients affected by IgM-related neuropathy, chronic inflammatory demyelinating polyneuropathy (CIDP), monoclonal gammopathy of undetermined significance and healthy subjects, to investigate whether different immunological patterns may differentiate the classical phenotype from atypical forms. IFN-gamma producing CD4+ and CD8+ T lymphocytes, as well as CD4+ and CD8+ T cells expressing T-bet (T-helper type 1, Th1) were increased in CIDP patients. The percentage of circulating CD4+ and CD8+ T cells producing IL-10 as well as the percentage of CD19+ cells expressing Blimp-1 were higher in patients with IgM-neuropathy. We did not find any significant differences in the different lymphocytes subsets in the IgM-related neuropathy between patients with classical and atypical phenotype. Th1 cells are increased in CIDP patients while a T helper type 2-phenotype seems to prevail in patients with IgM-neuropathy. Further studies involving a larger patient population are needed to evaluate if different lymphocytes subset may be involved in different clinical phenotypes of IgM-related neuropathy.

Immune-mediated neuropathies following stem cell transplantation.

OBJECTIVE: To study the clinical, electrophysiological and pathological characteristics and outcome of immune-mediated neuropathy (IMN) following stem cell transplantation (SCT). METHODS: Retrospective chart review of the Mayo Clinic Rochester SCT database between January 1997 and August 2012. RESULTS: Of the 3305 patients who underwent SCT, 12 patients (0.36%) had IMN. The median time from SCT to IMN was 7 months. IMN typically presented as an asymmetric radiculoplexus neuropathy (7/12 patients) or acute polyradiculoneuropathy (Guillain-Barré syndrome) (4/12). Neurophysiology showed demyelinating neuropathy in four patients and axonal neuropathy in eight. Cerebrospinal fluid protein was increased in five of six patients (median 67 mg/dL). The Neuropathy Impairment Score (NIS) improved in all patients (mean NIS 43-10, p=0.016). Six patients died. One patient died from complications of IMN and one died from complications of the haematological disease. Five patients had recurrence of their malignancy within 4 months of the IMN and of these, four died. CONCLUSIONS: IMN occurs rarely in patients after SCT. Two possible mechanisms include (1) an immune reconstitution syndrome, supported by stereotypical neuropathy types (radiculoplexus and polyradiculoneuropathies), monophasic course and temporal association with SCT and (2) a paraneoplastic phenomenon, supported by frequent early malignancy recurrence following IMN.

Peripheral nervous system neuroimmunology seen by a neuro-pathologist.

In most dysimmune neuropathies, historically the microscopical lesions were described prior to immunological studies. The latter along with neuropathological studies have found some immune, albeit incomplete, explanations of the mechanisms of these lesions which we will describe in two main syndromes: the primitive auto-immune inflammatory peripheral polyneuropathies (GBS and CIDP) and polyneuropathies induced by a monoclonal dysglobulinemia. In some patients who have to be discussed case by case pathology (nerve biopsy) will confirm the diagnosis, may help to delineate the molecular anomalies and identify lesional mechanisms. We will review the high variability of nerve lesions which is characteristic of dysimmune neuropathies. Pathological studies confirm that both humoral and cellular immune reactions against Schwann cell and/or axonal antigens are implicated in primitive dysimmune neuropathies due to a dysfunction or failure of immune tolerance mechanisms. In case of a polyneuropathy associated to a monoclonal dysglobulinemia, pathological and immunological studies have shown that in many patients, the dysglobulinemia did harm the peripheral nerve; knowledge of the pathological lesions and their mechanisms is of major interest for orienting specific treatments.

Beneficial effects of Rituximab in patients with anti-MAG (myelin-associated glycoprotein) neuropathy: case reports.

Anti-myelin-associated glycoprotein (MAG) neuropathy is a primary demyelinating sensorimotor polyneuropathy that can be very debilitating and is known to be resistant to treatment. There are only a few conflicting reports on the effect of Rituximab in anti-MAG neuropathy. We present three patients who improved remarkably with Rituximab infusions. Until the safety and efficacy of this drug are determined in larger controlled studies, use of Rituximab should be limited to patients with significant neurologic deficits.

Clinical trials in CIDP and chronic autoimmune demyelinating polyneuropathies.

The main chronic autoimmune neuropathies include chronic inflammatory demyelinating polyneuropathy (CIDP), multifocal motor neuropathy (MMN), and anti-myelin-associated glycoprotein (MAG) demyelinating neuropathy. On the basis of randomized controlled studies, corticosteroids, intravenous immunoglobulin (IVIg), and plasmapheresis provide short-term benefits in CIDP. MMN responds only to IVIg. Because in MMN and CIDP, IVIg infusions are required every 3-6 weeks to sustain benefits or long-term remissions, there is a need for "IVIg-sparing" agents. In CIDP, immunosuppressive drugs, such as azathioprine, cyclosporine, methotrexate, mycophenolate, and cyclophosphamide, are used, but controlled trials have not shown that they are effective. Controlled trials have also not shown benefit to any agents in anti-MAG neuropathy. However, clinicians use many immunosuppressive drugs in both settings, but all have potentially serious side effects and are only effective in some patients. Thus, there is a need for new therapies in the inflammatory and paraproteinemic neuropathies. New agents targeting T cells, B cells, and transmigration and transduction molecules are discussed as potential treatment options for new trials. The need for biomarkers that predict therapeutic responses or identify patients with active disease is emphasized, and the search for better scoring tools that capture meaningful changes after response to therapies is highlighted.

Long-term response to rituximab and fludarabine combination in IgM anti-myelin-associated glycoprotein neuropathy.

We report the clinical response and biological effects of treatment with rituximab and fludarabine (RF) in five patients with IgM anti-myelin-associated glycoprotein (MAG) demyelinating neuropathy. Between November 2006 and October 2009, four men and one woman aged 52-85 years received intravenous rituximab at 375 mg/m(2) on day 1 and oral fludarabine at 40 mg/m(2) /day from days 1 to 5, in a treatment cycle that was repeated every month for up to 6 months. Two patients had IgM monoclonal gammopathy of undetermined significance and three low tumor mass Waldenstrom's macroglobulinemia. Four patients showed a major hematological response with a decrease in anti-MAG titer in three and clearing in one. One patient did not respond. For the responding patients, symptoms and electrophysiological parameters improved significantly. No patient relapsed at post-RF treatment follow-up (12-45 months), and no toxicity was reported. The combination of RF induced significant responses in IgM anti-MAG demyelinating neuropathies, without toxicity. Clinical improvements were correlated to hematological and immunological results.

Auto-immune polyradiculoneuropathy and a novel IgG biomarker in workers exposed to aerosolized porcine brain.

Twenty-four patients, all of whom were exposed to aerosolized porcine brain tissue through work-place environment (abattoir), developed a syndrome of immune-mediated polyradiculoneuropathy; three also had central nervous system manifestations (transverse myelitis, meningoencephalitis, and aseptic meningitis). Patients had characteristic electrophysiological findings of very distal and proximal conduction slowing (prolonged distal and F-wave latencies, regions where the blood-nerve barrier is the most permeable) and all patients' serum contained a novel IgG immunofluorescence pattern. Nerve pathology, when available, showed mild changes of segmental demyelination, axonal degeneration, and inflammatory changes. Patients had meaningful improvement of symptoms and electrophysiologic findings with immune therapy and with removal of exposure to aerosolized brain tissue. We postulate that this outbreak is an auto-immune polyradiculoneuropathy triggered by occupational exposure to multiple aerosolized porcine neural tissue antigens that result in neural damage where the blood-nerve barrier is the least robust.

[Diagnosis of immune-mediated neuropathies]. / Az immunmediált neuropathiák diagnosztikája.

Separate discussion of immune-mediated neuropathies from other neuropathies is justified by the serious consequences of the natural course of these diseases, like disability and sometimes even life threatening conditions. On the other hand nowadays effective treatments already exist, and with timely and correct diagnosis an appropriately chosen treatment may result in significant improvement of quality of life, occasionally even complete recovery. These are rare diseases, and the increasing number of different variants makes it more difficult to recognize them. Their diagnosis is based on the precise knowledge of clinical signs and symptoms, and it is verified by the help of neurophysiologic and laboratory, first of all CSF examinations. Description of clinical features of the classic acute immune-mediated neuropathy, characterized by ascending paresis and demyelination is followed by a summary of characteristics of newly recognized axonal, regional and functional variants. Chronic immune-mediated demyelinating polyneuropathies are not diagnosed in due number even today. This paper does not only present the classic form but it also introduces the ever increasing special variants, like distal acquired demyelinating sensory neuropathy, Lewis-Sumner syndrome, multifocal motor neuropathy and paraproteinemic neuropathies. Vasculitic neuropathies can be divided into two groups: systemic and non-systemic ones. The first sign of a vasculitic neuropathy is a progressive, painful mononeuropathy; the classic clinical presentation is the mononeuritis multiplex. It is characterized by general signs like fever, loss of weight, fatigue. In systemic vasculitis organ specific symptoms are also present. From the paraneoplastic diseases the subacute sensory neuropathy and the sensory neuronopathy are members of the immune-mediated neuropathies, being most frequently associated with small cell lung cancer.

Spinal fluid IgG antibodies from patients with demyelinating diseases bind multiple sclerosis-associated bacteria.

A panel of 10 IgG enzyme-linked immunosorbent assays (ELISAs) were developed for the detection of anti-microbial immune responses in the cerebrospinal fluid (CSF) of patients with demyelinating diseases (DD). The anti-microbial ELISA assays follow on prior human brain tissue RNA sequencing studies that established multiple sclerosis (MS) microbial candidates. Lysates included in the ELISA panel were derived from Akkermansia muciniphila, Atopobium vaginae, Bacteroides fragilis, Lactobacillus paracasei, Odoribacter splanchnicus, Pseudomonas aeruginosa, Cutibacterium (Propionibacterium) acnes, Fusobacterium necrophorum, Porphyromonas gingivalis, and Streptococcus mutans. CSF responses from patients with demyelinating diseases (DD, N = 14) were compared to those with other neurological diseases (OND, N = 8) and controls (N = 13). Commercial positive and negative control CSF specimens were run with each assay. ELISA index values were derived for each specimen against each of the 10 bacterial lysates. CSF reactivity was significantly higher in the DD group compared to the controls against Akkermansia, Atopobium, Bacteroides, Lactobacillus, Odoribacter, and Fusobacterium. Four of the 11 tested DD group subjects had elevated antibody indexes against at least one of the 10 bacterial species, suggesting intrathecal antibody production. This CSF serological study supports the hypothesis that several of the previously identified MS candidate microbes contribute to demyelination in some patients. KEY MESSAGES: A panel of 10 IgG enzyme-linked immunosorbent assays (ELISAs) were developed for the detection of anti-microbial immune responses in the cerebrospinal fluid (CSF) of patients with demyelinating diseases, including multiple sclerosis and acute disseminated encephalomyelitis. CSF reactivity was significantly higher in the demyelination group compared to the controls against the bacteria Akkermansia, Atopobium, Bacteroides, Lactobacillus, Odoribacter, and Fusobacterium. Several of the demyelination subjects had elevated antibody indexes against at least one of the 10 antigens, suggesting at least limited intrathecal production of anti-bacterial antibodies. This CSF serological study supports the hypothesis that several of the previously identified MS candidate microbes contribute to demyelination in some patients.

Anti-MAG neuropathy: From biology to clinical management.

The acquired chronic demyelinating neuropathies include a growing number of disease entities that have characteristic, often overlapping, clinical presentations, mediated by distinct immune mechanisms, and responding to different therapies. After the discovery in the early 1980s, that the myelin associated glycoprotein (MAG) is a target antigen in an autoimmune demyelinating neuropathy, assays to measure the presence of anti-MAG antibodies were used as the basis to diagnose the anti-MAG neuropathy. The route was open for describing the clinical characteristics of this new entity as a chronic distal large fiber sensorimotor neuropathy, for studying its pathogenesis and devising specific treatment strategies. The initial use of chemotherapeutic agents was replaced by the introduction in the late 1990s of rituximab, a monoclonal antibody against CD20+ B-cells. Since then, other anti-B cells agents have been introduced. Recently a novel antigen-specific immunotherapy neutralizing the anti-MAG antibodies with a carbohydrate-based ligand mimicking the natural HNK-1 glycoepitope has been described.

A bacterium lipopolysaccharide that elicits Guillain-Barré syndrome has a GM1 ganglioside-like structure.

There is a strong association between Guillain-Barré syndrome (GBS) and Penner's serotype 19 (PEN 19) of Campylobacter jejuni. Sera from patients with GBS after C. jejuni infection have autoantibodies to GM1 ganglioside in the acute phase of the illness. Our previous work has suggested that GBS results from an immune response to cross-reactive antigen between lipopolysaccharide (LPS) of the Gram-negative bacterium and membrane components of peripheral nerves. To clarify the pathogenesis of GBS, we have investigated whether GM1-oligosaccharide structure is present in the LPS of C. jejuni (PEN 19) that was isolated from a GBS patient. After extraction of the LPS, the LPS showing the binding activity of cholera toxin, that specifically recognizes the GM1-oligosaccharide was purified by a silica bead column chromatography. Gas-liquid chromatography-mass spectrometric analysis has shown that the purified LPS contained Gal, GalNAc, and NeuAc, which are sugar components of GM1 ganglioside. 1H NMR methods [Carr-Purcell-Meiboom-Gill (CPMG), total correlation spectroscopy (TOCSY), and nuclear Overhauser effect spectroscopy (NOESY)] have revealed that the oligosaccharide structure [Gal beta 1-3 GalNAc beta 1-4(NeuAc alpha 2-3)Gal beta] protrude from the LPS core. This terminal structure [Gal beta 1-3GalNAc beta 1-4(NeuAc alpha 2-3)Gal beta] is identical to the terminal tetrasaccharide of the GM1 ganglioside. This is the first study to demonstrate the existence of molecular mimicry between nerve tissue and the infectious agent that elicits GBS.

Steroid-responsive myeloneuropathy associated with antithyroid antibodies.

BACKGROUND/OBJECTIVE: To present information about 2 steroid-responsive, antithyroid antibody-positive patients with myeloneuropathy and myelopathy. METHODS: Case reports. RESULTS: A 48-year-old woman and a 42-year-old man presented with acute onset tetraparesis and magnetic resonance imaging studies showing cervical spinal lesions. Nerve conduction and biopsy studies of the woman were suggestive of a demyelinating polyradiculoneuropathy. Detailed diagnostic workup turned out to be negative for both patients, except for highly elevated antithyroid antibodies with normal thyroid functions and imaging. Both patients responded remarkably well to high-dose steroid treatment, and their symptoms disappeared in a few months. Both patients' antithyroid antibody levels were reduced shortly after steroid treatment and in parallel with the amelioration of symptoms. CONCLUSIONS: Antithyroid antibodies might be associated with acute demyelinating myeloneuropathy or myelopathy pathogenesis and might indicate a good response to steroid treatment in these syndromes.

Childhood-onset multifocal motor neuropathy with IgM antibodies to GM2 and GalNac-GD1a.

BACKGROUND: Multifocal motor neuropathy (MMN) is an acquired immune-mediated form of neuropathy characterized by upper and asymmetric limb weakness without sensory loss. The mean age of onset is 40 years (range, 20-70 years), and childhood-onset MMN is extremely rare. In the present report, we discuss a case of childhood-onset MMN in a patient who tested positive for anti-GM2 and anti-GalNac-GD1a immunoglobulin M (IgM) antibodies. CASE REPORT: A 12-year-old girl presented with progressive weakness of the upper extremities without sensory loss. Electrophysiological assessments revealed definite conduction blocks in the left median and bilateral radial nerves. She was diagnosed with MMN in accordance with the European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) criteria. Serological studies revealed that she tested positive for IgM antibodies to GM2 and GalNac-GD1a. Partial improvements in both muscle weakness and electrophysiological assessments were achieved after 8 months of high-dose intravenous immunoglobulin (IVIg) treatment. CONCLUSION: Although childhood-onset MMN is rare, most patients respond to IVIg treatment. This is the first case of childhood-onset MMN in a patient who tested positive for anti-GM2 and anti-GalNac-GD1a IgM antibodies. Although half of the adult patients with MMN test positive for anti-GM1 IgM antibodies, they were not detected in our patient. Comprehensive testing for serum anti-glycolipid antibodies in addition to GM1 may aid in the diagnosis of childhood-onset MMN.

Cav2.1 voltage-dependent Ca2+ channel current is inhibited by serum from select patients with Guillain-Barré syndrome.

To investigate the pathophysiological mechanisms of immune-mediated peripheral neuropathies, we studied the effects of sera from patients with Guillain-Barré syndrome (GBS) on the Cav2.1 voltage-dependent calcium channel (VDCC) current in Purkinje cells. Using the whole-cell recording technique, Cav2.1 VDCC current was measured in cerebellar Purkinje cells in the presence of serum from GBS patients with acute motor axonal neuropathy (AMAN) or acute inflammatory demyelinating polyneuropathy (AIDP). The AMAN patient sera significantly inhibited the Cav2.1 VDCC current compared with healthy volunteer sera, and this inhibition was fully reversible by washing out the AMAN serum. Similarly, IgG purified from AMAN sera also inhibited the Cav2.1 VDCC current. However, the activation and inactivation kinetics of the Cav2.1 VDCC currents were not affected by serum from an AMAN patient. Moreover, the VDCC current of Purkinje cells was also inhibited by IgG anti-GM1 monoclonal antibody (anti-GM1 mAb). In an immunocytochemical study using double fluorescence staining, Purkinje cells were stained by monoclonal IgG anti-GM1 mAb. In contrast, AIDP patient and healthy volunteer sera did not affect the Cav2.1 VDCC current. These results suggest that in some case of GBS, particularly of AMAN patients with IgG anti-GM1 mAb, muscle weakness may be induced by dysfunction of Cav2.1 VDCC functioning at the motor nerve terminals.

Neuropathy of gastrointestinal Chagas' disease: immune response to myelin antigens.

Most reports of autoimmune response during infection with the parasite Trypanosoma cruzi have dealt with the cardiomyopathic form of Chagas' disease, but little is known about the mechanisms of tissue damage involved in the gastrointestinal form, which was studied here. Chronically infected patients with a severe gastrointestinal form of Chagas' disease present increased antibody production and proliferative responses to peripheral myelin components, such as myelin basic protein (MBP), which is homologous to the P1 protein fraction of peripheral myelin. T lymphocytes preferentially recognize a region on the MBP molecule (1-30), which suggests that the MBP is a potential target on the peripheral nerve for autoimmune reactions in patients with gastrointestinal lesions resulting from Chagas' disease.