Characterization of complement-fixing antibodies to peripheral nerve myelin in Guillain-Barré syndrome

Application of optogenetic glial cells to neuron-glial communication

Optogenetic techniques combine optics and genetics to enable cell-specific targeting and precise spatiotemporal control of excitable cells, and they are increasingly being employed. One of the most significant advantages of the optogenetic approach is that it allows for the modulation of nearby cells or circuits with millisecond precision, enabling researchers to gain a better understanding of the complex nervous system. Furthermore, optogenetic neuron activation permits the regulation of information processing in the brain, including synaptic activity and transmission, and also promotes nerve structure development. However, the optimal conditions remain unclear, and further research is required to identify the types of cells that can most effectively and precisely control nerve function. Recent studies have described optogenetic glial manipulation for coordinating the reciprocal communication between neurons and glia. Optogenetically stimulated glial cells can modulate information processing in the central nervous system and provide structural support for nerve fibers in the peripheral nervous system. These advances promote the effective use of optogenetics, although further experiments are needed. This review describes the critical role of glial cells in the nervous system and reviews the optogenetic applications of several types of glial cells, as well as their significance in neuron-glia interactions. Together, it briefly discusses the therapeutic potential and feasibility of optogenetics.

Comparison of the Efficacy of Optogenetic Stimulation of Glia versus Neurons in Myelination

Increasing evidence demonstrates that optogenetics contributes to the regulation of brain behavior, cognition, and physiology, particularly during myelination, potentially allowing for the bidirectional modulation of specific cell lines with spatiotemporal accuracy. However, the type of cell to be targeted, namely, glia vs neurons, and the degree to which optogenetically induced cell activity can regulate myelination during the development of the peripheral nervous system (PNS) are still underexplored. Herein, we report the comparison of optogenetic stimulation (OS) of Schwann cells (SCs) and motor neurons (MNs) for activation of myelination in the PNS. Capitalizing on these optogenetic tools, we confirmed that the formation of the myelin sheath was initially promoted more by OS of calcium translocating channelrhodopsin (CatCh)-transfected SCs than by OS of transfected MNs at 7 days in vitro (DIV). Additionally, the level of myelination was substantially enhanced even until 14 DIV. Surprisingly, after OS of SCs, > 91.1% ± 5.9% of cells expressed myelin basic protein, while that of MNs was 67.8% ± 6.1%. The potent effect of OS of SCs was revealed by the increased thickness of the myelin sheath at 14 DIV. Thus, the OS of SCs could highly accelerate myelination, while the OS of MNs only somewhat promoted myelination, indicating a clear direction for the optogenetic application of unique cell types for initiating and promoting myelination. Together, our findings support the importance of precise cell type selection for use in optogenetics, which in turn can be broadly applied to overcome the limitations of optogenetics after injury.

A review of the use of biological agents for chronic inflammatory demyelinating polyradiculoneuropathy

Chronic inflammatory demyelinating polyneuropathy (CIDP) is a group of idiopathic, acquired, immune-mediated inflammatory demyelinating diseases of the peripheral nervous system. A majority of patients with CIDP respond to "first-line" treatment with IVIG, plasmapheresis and/or corticosteroids. There exists insufficient evidence to ascertain the benefit of treatment with "conventional" immunosuppressive drugs. The inconsistent efficacy, long-term financial burden and health risks of non-specific immune altering therapy have drawn recurrent attention to the possible usefulness of a variety of biological agents that target key aspects in the CIDP immunopathogenic pathways. This review aims to give an updated account of the scientific rationale and potential use of biological therapeutics in patients with CIDP. No specific treatment recommendations are given. The discovery, development and application of biological markers by modern molecular diagnostic techniques may help identify drug-naïve or treatment-resistant CIDP patients most likely to respond to targeted immunotherapy.

Innate immunity in the nervous system

The complement (C) system plays a central role in innate immunity and bridges innate and adaptive immune responses. A fine balance of C activation and regulation mediates the elimination of invading pathogens and the protection of the host from excessive C deposition on healthy tissues. If this delicate balance is disrupted, the C system may cause injury and contribute to the pathogenesis of various diseases, including neurodegenerative disorders and neuropathies. Here we review evidence indicating that C factors and regulators are locally synthesized in the nervous system and we discuss the evidence supporting the protective or detrimental role of C activation in health, injury, and disease of the nerve.

The role of macrophages in Wallerian degeneration

The present review focuses on macrophage properties in Wallerian degeneration. The identification of hematogenous phagocytes, the involvement of cell surface receptors and soluble factors, the state of activation during myelin removal and the signals and factors leading to macrophage recruitment into degenerating peripheral nerves after nerve transection are reviewed. The main effector cells in Wallerian degeneration are hematogenous phagocytes. Resident macrophages and Schwann cells play a minor role in myelin removal. The macrophage complement receptor type 3 is the main surface receptor involved in myelin recognition and uptake. The signals leading to macrophage recruitment are heterogenous and not yet defined in detail. Degenerating myelin and axons are suggested to participate. The relevance of these findings for immune-mediated demyelination are discussed since the definition of the role of macrophages might lead to a better understanding of the pathogenesis of demyelination.

Mechanisms of immune regulation in the peripheral nervous system

The peripheral nervous system (PNS) is a target for heterogenous immune attacks mediated by different components of the systemic immune compartment. T cells, B cells, and macrophages can interact with endogenous, partially immune-competent glial cells and contribute to local inflammation. Cellular and humoral immune functions of Schwann cells have been well characterized in vitro. In addition, the interaction of the humoral and cellular immune system with the cellular and extracellular components in the PNS may determine the extent of tissue inflammation and repair processes such as remyelination and neuronal outgrowth. The animal model experimental autoimmune neuritis (EAN) allows direct monitoring of these immune responses in vivo. In EAN contributions to regulate autoimmunity in the PNS are made by adhesion molecules and by cytokines that orchestrate cellular interactions. The PNS has a significant potential to eliminate T cell inflammation via apoptosis, which is almost lacking in other tissues such as muscle and skin. In vitro experiments suggest different scenarios how specific cellular and humoral elements in the PNS may sensitize autoreactive T cells for apoptosis in vivo. Interestingly several conventional and novel immunotherapeutic approaches like glucocorticosteroids and high-dose antigen therapy induce T cell apoptosis in situ in EAN. A better understanding of immune regulation and its failure in the PNS may help to develop improved, more specific immunotherapies.

Current Therapeutic Options in Severe Guillain-Barre?? Syndrome

The classical form of Guillain-Barré syndrome (GBS) refers to an acute monophasic demyelinating motor and sensory polyneuropathy characterized by symmetric ascending flaccid weakness, along with sensory impairment and, less commonly, autonomic perturbations. Pure motor axonal forms, axonal motor, and sensory forms, as well as pure autonomic forms, have also been identified. A complex immune-mediated process leads to segmental demyelination accompanied with axonal involvement in protracted cases. Establishing strategies of immunomodulation may therefore halt and even reverse the harmful autoimmune insult to peripheral nerves. The present article reviews the current immunomodulatory options in severe GBS. A recent Cochrane meta-analysis of 6 randomized studies showed no significant improvement using corticosteroids, including either oral or intravenous methylprednisolone. Combined methylprednisolone and immunoglobulins shortened the time lapse to regain independent walking. Plasmapheresis (PE) was the first effectively proven method of immunomodulation, followed by intravenous immunoglobulins (IVIG). Both methods are comparable in their beneficial effect and were used either separately or in combination, but PE was more frequently associated with severe adverse effects requiring cessation of therapy, including a bleeding diathesis. In addition, PE is feasible only in major referral centers requiring the appropriate equipment and trained personnel. In addition, younger children may be at risk for bleeding after insertion of wide catheters. Therefore, in cases of severe GBS, IVIG is recommended as the first-line drug using a total empiric dose of 2 g/kg administered over 2 consecutive days, especially in children proven highly effective with negligible adverse effects. In protracted cases, the addition of intravenous corticosteroids to IVIG should be considered, which may shorten the duration to regain independent walking. If such therapy fails, PE should be applied using centrifugal blood separators with 5% albumin as the substitute solution.

Outcome of severe Guillain-Barré syndrome in children: comparison between untreated cases versus gamma-globulin therapy

The objective of this study was to assess retrospectively the outcome of children with severe Guillain-Barré syndrome (GBS) treated either with intravenous immunoglobulins (IVIG) versus practically untreated cases by a known beneficial agent. Twenty-three children with severe GBS who became bedridden (i.e., Motor Disability Grading Scale [MDGS] grade of at least 4) were analyzed. Fifteen children were treated with IVIG and eight children comprised the nontreatment group: five on supportive therapy and three treated previously with oral steroids found ineffective in GBS. IVIG was administered at a dosage of 1 g/kg daily for 2 days under constant monitoring, with no adverse effects requiring cessation of therapy. Improvement by 1 grade on the MDGS after IVIG therapy was achieved in the IVIG group after a mean of 10.17 days (median, 8 days), and patients started walking independently after a mean of 30.35 days (median, 20.5 days). Improvement by 1 grade on the MDGS was achieved in the nontreatment group after a mean of 22.3 days (median, 20.3 days), and they started to walk independently after a mean of 113.3 days (median, 100 days). A significant difference could not be delineated between both groups, given the rather small number of children in each group. These results indicate a possible beneficial effect of IVIG in severe childhood-onset GBS compared with the nontreated group of children. The authors therefore recommend using IVIG as the first-line drug in such cases, which warrant further approval after double-blind controlled studies of using different IVIG regimens or combined with plasmapheresis and steroids.

Glial cells as targets for cytotoxic immune mediators

Oligodendrocytes and Schwann cells are the glia principally responsible for the synthesis and maintenance of myelin. Damage may occur to these cells in a number of conditions, but perhaps the most studied are the idiopathic inflammatory demyelinating diseases, multiple sclerosis in the CNS, and Guillain-Barré syndrome and its variants in the peripheral nervous system (PNS). This article explores the effects on these cells of cytotoxic immunological and inflammatory mediators: similarities are revealed, of which perhaps the most important is the sensitivity of both Schwann cells and oligodendrocytes to many such agents. This area of research is, however, characterised and complicated by numerous and often very substantial inter-observer discrepancies. Marked variability in cell culture techniques, and in assays of cell damage and death, provide artifactual explanations for some of this variability; true inter-species differences also contribute. Not the least important conclusion centres on the limited capacity of in vitro studies to reveal disease mechanisms: cell culture findings merely illustrate possibilities which must then be tested ex vivo using human tissue samples affected by the relevant disease.

Anti-GM(2) IgM antibody-induced complement-mediated cytotoxicity in patients with dysimmune neuropathies

Anti-GM2 IgM antibodies have been reported in some patients with dysimmune neuropathy or lower motor neuron syndrome. To determine whether these antibodies can induce complement-dependent cytolysis we performed a cytotoxicity assay on neuroblastoma cells with sera from seven patients with demyelinating dysimmune neuropathies and high titers of anti-GM2 IgM. As controls we used sera from seven patients with other anti-neural reactivities, six with the same neuropathies but no anti-GM2 or other anti-neural reactivity and from eight normal subjects. Of the seven positive sera tested, six induced complement-mediated cytotoxicity, while none of the controls had any relevant effect on neuroblastoma cells. Preincubation of positive sera with purified GM2 removed cytotoxic activity. Affinity purified anti-GM2 IgM had the same cytotoxic anti-GM2 effect of whole serum while serum or complement alone did not have any effect. In four anti-GM2-positive patients the percentage of cell lysis correlated with anti-GM2 titers and with IgM staining of neuroblastoma cells while in two the cytotoxic effect was higher than expected from antibody titers. Complement-mediated cell lysis induced by anti-GM2 IgM antibodies may be a possible mechanism of neural damage in patients with dysimmune neuropathy and high titers of anti-GM2 IgM antibodies.

Cutting edge: C3, a key component of complement activation, is not required for the development of myelin oligodendrocyte glycoprotein peptide-induced experimental autoimmune encephalomyelitis in mice

Experimental autoimmune encephalomyelitis (EAE), an inflammatory demyelinating disease of the CNS, is regarded as an experimental model for multiple sclerosis. The complement has been implicated in the pathogenesis of multiple sclerosis. To clarify the role of C in mouse EAE, we immunized mice deficient in C3 (C3(-/-)) and their wild-type (C3(+/+)) littermates with myelin oligodendrocyte glycoprotein peptide 35-55. C3(-/-) mice were susceptible to EAE as much as the C3(+/+) mice were. No differences were found for the production of IL-2, IL-4, IL-12, TNF-alpha, and IFN-gamma between C3(+/+) and C3(-/-) mice. This finding shows that C3, a key component in C activation, is not essential in myelin oligodendrocyte glycoprotein peptide-induced EAE in mice.

Immunohistochemical localization of cytokines, C5b-9 and ICAM-1 in peripheral nerve of Guillain-Barré syndrome

The spectrum of the Guillain-Barré Syndrome (GBS) has recently been widened by the newly identified forms of acute motor axonal neuropathy (AMAN) and acute motor sensory axonal neuropathy (AMSAN). An important question has been raised regarding the possibility for the axon to be a target in immune-mediated damage. Although myelin breakdown is the characteristic feature of classic acute inflammatory demyelinating polyradiculoneuropathy (AIDP), axonal degeneration may occasionally be observed in this form, especially in cases with explosive onset and severe clinical course. Immunohistochemical findings of five frozen sural nerves biopsies of patients with GBS (AIDP variant) tested with a panel of monoclonal antibodies raised against different molecules implicated in immune-mediated processes have principally disclosed an immunoreactivity of tumor necrosis factor-alpha (TNF-alpha) on both Schwann cell membranes and in myelinated and unmyelinated axons. On the other hand, interleukin 1-beta (IL1-beta) labeled Schwann cells, endothelial cells and macrophages; interferon-gamma (IFN-gamma) was observed both in endothelial cells and lymphocytes. Membrane attack complex (C5b-9) deposits were observed on Schwann cell membranes and finally intercellular adhesion molecule-1 (ICAM-1) was localized both on endothelial cells and macrophages. Our findings strongly suggest that TNF-alpha is an important factor in the cascade of events leading to immune-mediated demyelination and axonal damage in GBS.

Pathogenesis of Guillain-Barré syndrome

Recent neurophysiological and pathological studies have led to a reclassification of the diseases that underlie Guillain-Barré syndrome (GBS) into acute inflammatory demyelinating polyradiculoneuropathy (AIDP), acute motor and sensory axonal neuropathy (AMSAN) and acute motor axonal neuropathy (AMAN). The Fisher syndrome of ophthalmoplegia, ataxia and areflexia is the most striking of several related conditions. Significant antecedent events include Campylobacter jejuni (4-66%), cytomegalovirus (5-15%), Epstein-Barr virus (2-10%), and Mycoplasma pneumoniae (1-5%) infections. These infections are not uniquely associated with any clinical subtype but severe axonal degeneration is more common following C. jejuni and severe sensory impairment following cytomegalovirus. Strong evidence supports an important role for antibodies to gangliosides in pathogenesis. In particular antibodies to ganglioside GM1 are present in 14-50% of patients with GBS, and are more common in cases with severe axonal degeneration associated with any subtype. Antibodies to ganglioside GQ1b are very closely associated with Fisher syndrome, its formes frustes and related syndromes. Ganglioside-like epitopes exist in the bacterial wall of C. jejuni. Infection by this and other organisms triggers an antibody response in patients with GBS but not in those with uncomplicated enteritis. The development of GBS is likely to be a consequence of special properties of the infecting organism, since some strains such as Penner 0:19 and 0:41 are particularly associated with GBS but not with enteritis. It is also likely to be a consequence of the immunogenetic background of the patient since few patients develop GBS after infection even with one of these strains. Attempts to match the subtypes of GBS to the fine specificity of anti-ganglioside antibodies and to functional effects in experimental models continue but have not yet fully explained the pathogenesis. T cells are also involved in the pathogenesis of most or perhaps all forms of GBS. T cell responses to any of three myelin proteins, P2, PO and PMP22, are sufficient to induce experimental autoimmune neuritis. Activated T cells are present in the circulation in the acute stage, up-regulate matrix metalloproteinases, cross the blood-nerve barrier and encounter their cognate antigens. Identification of the specificity of these T cell responses is still at a preliminary stage. The invasion of intact myelin sheaths by activated macrophages is difficult to explain according to a purely T cell mediated mechanism. The different patterns of GBS are probably due to the diverse interplay between antibodies and T cells of differing specificities.

Detection of an autoantibody from Pug dogs with necrotizing encephalitis (Pug dog encephalitis)

An autoantibody against canine brain tissue was detected in the cerebrospinal fluid (CSF) and serum of two Pug dogs (Nos. 1 and 2) by indirect immunofluorescence assay (IFA). Dog No. 1, a 2-year-old male, exhibited severe depression, ataxia, and generalized seizures and died 2 months after the onset of symptoms. Dog No. 2, a 9-month-old male, exhibited severe generalized seizures and died 17 months after the onset of symptoms. Histopathologic examination revealed a moderate to severe multifocal accumulation of lymphocytes, plasma cells, and a few neutrophils in both the gray and white matter of the cerebrum in dog No. 1. In dog No. 2, the cellular infiltrates were mild, but there was a severe, diffuse, and multifocal necrosis in the cerebral cortex with prominent astrocytosis. With the aid of IFA using fluorescein isothiocyanate-labeled antidog IgG goat serum and a confocal imaging system, specific reactions for glial cells were detected in the CSF of these Pug dogs but not in six canine control CSF samples. Double-labeling IFA using CSF from these Pug dogs and a rabbit antiserum against glial fibrillary acidic protein (GFAP) revealed that the autoantibody recognized GFAP-positive astrocytes and their cytoplasmic projections. By immunoblot analysis, the autoantibody from CSF of these Pug dogs recognized two common positive bands at 58 and 54 kd, which corresponded to the molecular mass of human GFAP. The role of this autoantibody for astrocytes is not yet clear. However, if the presence of the autoantibody is a specific feature of Pug dog encephalitis, it will be a useful clinical diagnostic marker and a key to the pathogenesis of this unique canine neurologic disease.

Myelinated dorsal root ganglion cultures activate both the alternative and classical pathways of complement

We used rat myelinated dorsal root ganglion (MDRG) cultures to study antibody and complement-mediated mechanisms of peripheral demyelinating diseases. Heat inactivated serum from a patient (LT) with peripheral neuropathy and a monoclonal IgM reactive with myelin-associated glycoprotein (anti-MAG) and sulfated glucuronosyl glycolipids (anti-SGGL) was used as an antibody source. Incubation of whole human serum (WHS) or WHS and anti-SGGL with MDRGs resulted in reduction of classical and alternative pathway hemolytic activities and the development of abnormal myelin sheaths. Incubation of MDRG cultures with C2-deficient serum showed activation of the alternative complement pathway. Classical pathway hemolytic activity was reduced when Factor B-depleted serum was incubated with MDRG cultures. The rat MDRG culture system provides a good model system of a peripheral nerve and has therefore been used by several investigators to study antibody and complement-mediated demyelination associated with peripheral neuropathies. However, our studies indicate a high degree of complement activation and membrane disruption of cultures incubated with WHS.

Clomipramine and imipramine suppress clinical signs and T and B cell response to myelin proteins in experimental autoimmune neuritis in Lewis rats

5-Hydroxytryptamine (5-HT) reuptake inhibitors of the zimeldine-type have induced polyneuropathies similar to Guillain-Barré syndrome (GBS) in patients with endogenous depression. Some monoamine neurotransmitters have been shown to affect immune reactions in vivo and in vitro in a concentration-dependent manner. We therefore studied the effect of the monoamine reuptake inhibitory anti-depressants, clomipramine and imipramine on specific immune response and the clinical course of experimental autoimmune neuritis (EAN), the animal model of GBS in humans. Clomipramine and imipramine both suppressed clinical signs of EAN induced by immunization with bovine peripheral nerve myelin (BPM), when given at a dose of 20 mg/kg/day intraperitoneally, via osmotic pumps. Clomipramine and imipramine reduced the numbers of Th1 cells secreting IFN-gamma in response to the neuritogenic myelin proteins BPM, P0 and P2 among lymph node mononuclear cells (MNC) from rats with EAN. The levels of cells secreting IgG antibodies to BPM, P2 and GM1 in lymph nodes were reduced at the height of EAN in clomipramine and imipramine treated animals. The action of clomipramine and imipramine on induced IFN-gamma and anti-myelin antibodies suggests that the mechanism for the suppressive effect of those substances on EAN symptoms may be due to an action on myelin T and B cell autoreactivity. Considering that the main common pharmacological principle of clomipramine and imipramine is to increase the functional activity of the nor-adrenaline (NA) and serotonin (5-HT) of the monoamines, it seems justified to postulate that the actions of clomipramine and imipramine demonstrated in this study to some extent involve NA and/or 5-HT. The immunomodulatory effects of clomipramine and imipramine call for further research on the potential role of drugs acting on the monoamine system in the treatment of autoimmune diseases, and for further studies of immunological mechanisms in the pathogenesis of depressive disorders.

Cyclosporin A in resistant chronic inflammatory demyelinating polyradiculoneuropathy

The role of cyclosporin A (CsA) in the treatment of resistant chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) was retrospectively reviewed in 19 patients who had failed to respond adequately to corticosteroids, plasmapheresis, intravenous immunoglobulin, and in some cases other immunosuppressive agents. Patients were subdivided into progressive or relapsing types according to the course of disease and response to therapy graded at follow-up by clinical and electrophysiological criteria. In the progressive group, the mean disability status declined from 3.8+/-0.7 to 1.8+/-1.1 grades on a 5-grade scale following CsA therapy (P<0.001). In the relapsing group, the mean annual incidence of relapse declined from 1.0+/-0.5 to 0.2+/-0.4 after commencement of CsA (P<0.05). Dose-dependent, reversible nephrotoxicity was the most serious complication of therapy, and necessitated cessation of CsA in 2 patients. In conclusion, CsA is an efficacious and, with appropriate monitoring, safe therapy for patients with CIDP.

Pathogenesis of neuroimmunologic diseases. Experimental models

Animal models of autoimmune diseases have greatly improved our current understanding of the pathogenesis of human autoimmunity and have provided the potential for therapies based on manipulation of the immune system. In our laboratory, we have investigated the immunopathogenesis of autoimmune diseases of the nervous system and muscle. We have developed immune-based approaches for the suppression of experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis (MS), and experimental autoimmune neuritis (EAN), a model for the Guillain-Barré syndrome (GBS). These approaches included induction of peripheral tolerance, immunotoxin targeting of activated T cells, and cytokine manipulations. In addition, we identified the antigen and characterized immunopathologically an autoimmune inflammatory disease of skeletal muscle, experimental autoimmune myositis (EAM), a model for the human inflammatory muscle disease polymyositis.

The role of complement in disorders of the nervous system

The complement (C) system plays important roles in host defense but activation at inappropriate sites or to an excessive degree can cause host tissue damage. C has been implicated as a factor in the causation or propagation of tissue injury in numerous diseases. The brain is an immunologically isolated site, sheltered from circulating cells and proteins of the immune system; nevertheless, there is a growing body of evidence implicating C in numerous brain diseases. In this brief article we review the evidence suggesting a role for C in diseases of the central and peripheral nervous system and discuss the possible sources of C at these sites. Some brain cells synthesize C and also express specific receptors; some are exquisitely sensitive to the lytic effects of C. The evidence suggests that C synthesis and activation in the brain are important in immune defense at this site, but may also play a role in brain disease.

Immune globulins are effective in severe pediatric Guillain-Barré syndrome

The effect of high-dose intravenous immune globulins was evaluated in an open prospective multicenter study of 26 children with severe Guillain-Barré syndrome. They presented with mild to moderate flaccid weakness of extremities, with cranial nerve involvement (20) and sensory impairment (22). All children rapidly deteriorated in 2-16 days (mean 6) to become bedridden, and 2 children also developed respiratory failure requiring artificial ventilation (Disability Grading Scale 4-5). Immune globulins were then administered at a total dose of 2 gm/kg, on 2 consecutive days, without adverse effects requiring discontinuation of therapy. Marked and rapid improvement was noted in 25 children, who improved by 1 to 2 Disability Grade Scales < or = 2 weeks after the infusion. Twenty were able to walk independently by 1 week, and 1 could be weaned off a ventilator. Eighteen children recovered by 2 weeks. The rest recuperated in a period of four months, including a child who was artificially ventilated for 4 weeks. The uniform rapid improvement and recovery associated with immune globulins contrasts with the slow recovery course in severe natural cases. We conclude that immune globulins are effective and safe in severe childhood-onset Guillain-Barré syndrome and therefore may serve as the initial treatment of choice.

The membrane attack complex of complement mediates peripheral nervous system demyelination in vitro

The present study used cocultures of rat dorsal root ganglia (DRG) and peritoneal macrophages to define the role of activated complement components during demyelination. The complement cascade was activated in vitro by treatment of the cultures with natural rat serum and lipopolysaccharides. Complement activation was examined by detection of the membrane attack complex of complement (MAC) with an antibody directed against rat C5-9. Detection of MAC in vitro by immunoelectron microscopy was associated with morphological changes of the myelin sheath. The sheath's regular structure was disrupted. Myelin lamellae were split and showed signs of decompaction. These changes were followed by a selective macrophage attack on myelin sheaths resulting in demyelination. Schwann cell viability was not affected by complement activation. Axons and sensory ganglion cells also survived this attack. The specificity of the complement effect was tested in experiments using treatment regimens with natural rat serum or lipopolysaccharides alone. In these experiments, no morphological changes of the myelin sheath were observed as well as no macrophage attack on myelin.

Immunopathogenesis and treatment of the Guillain-Barré syndrome--Part I

The etiology of the Guillain-Barré syndrome (GBS) still remains elusive. Recent years have witnessed important advances in the delineation of the mechanisms that may operate to produce nerve damage. Evidence gathered from cell biology, immunology, and immunopathology studies in patients with GBS and animals with experimental autoimmune neuritis (EAN) indicate that GBS results from aberrant immune responses against components of peripheral nerve. Autoreactive T lymphocytes specific for the myelin antigens P0 and P2 and circulating antibodies to these antigens and various glycoproteins and glycolipids have been identified but their pathogenic role remains unclear. The multiplicity of these factors and the involvement of several antigen nonspecific proinflammatory mechanisms suggest that a complex interaction of immune pathways results in nerve damage. Data on disturbed humoral immunity with particular emphasis on glycolipid antibodies and on activation of autoreactive T lymphocytes and macrophages will be reviewed. Possible mechanisms underlying initiation of peripheral nerve-directed immune responses will be discussed with particular emphasis on the recently highlighted association with Campylobacter jejuni infection.

Physiology and pathophysiology of complement: progress and trends

The complement system comprises a family of at least 20 plasma and membrane proteins that interact in a tightly regulated cascade system to destroy invading bacteria and prevent the deposition of immune complexes in the tissues. This brief review addresses the basic mechanisms of complement activation and control and describes the active fragments produced during complement activation. The biological importance of the complement system is amply illustrated in patients with complement deficiencies, who are susceptible to bacterial infections and immune complex diseases. The involvement of complement in other immunological diseases is an expanding area of clinical research, supported by the development of new assays for the identification of complement activation. This area is discussed here with particular reference to neurological diseases. A promising new prospect involves the use of complement inhibitory molecules in therapy of complement-mediated disease and this exciting area is also discussed. Novel physiological roles of complement also are being revealed and new evidence that complement and complement receptors play an important role in reproduction is summarized. It is hoped that this brief overview will convey some of the enthusiasm currently pervading research in this underappreciated area of immunology.

Myelin- and microbe-specific antibodies in Guillain-Barré syndrome

We surveyed the frequency of reported infections and target autoantigens in 56 Guillain Barré syndrome (GBS) patients by detecting antibodies to myelin and microbes. Sulfatide (43%), cardiolipin (48%), GD1a (15%), SGPG (11%), and GM3 (11%) antibodies were the most frequently detected heterogenous autoantibodies. A wide spectrum of antimicrobial IgG and IgM antibodies were also detected; mumps-specific IgG (66%), adenovirus-specific IgG (52%), varicella-zoster virus-specific IgG (46%), and S. pneumoniae serotype 7-specific IgG (45%) were the most prevalent. Our results indicate that polyclonal expansion of physiologic and pathologic antibodies and/or molecular mimicry likely occurs following infection and is related to other autoimmune factors in the etiology of GBS. Although no single definitive myelin-specific autoantibody was identified, our results suggest a unique pattern of reactivity against autoantigens.

Central autonomic dysorganization in the early stages of experimental meningitis in rabbits induced by complement-C5A-fragment: a pathophysiological validation of the largest lyapunov exponent of heart rate dynamics

In a study of central autonomic organization in early stages of experimental meningitis in rabbits, the temporal oscillations of the momentary heart rate (heart rate dynamics) were measured. In 10 anesthetized rabbits an experimental meningitis was induced by intracisternal injection of complement-C5a-fragment in a carrier solution of sodium chloride and bovine serum albumin. 10 rabbits were injected with the above carrier solution only and served as controls. The temporal structure of the heart rate dynamics was operationalized phase-space analytically through the estimation of the largest Lyapunov exponent. Without exception, positive Lyapunov exponents of the heart rate dynamics were found, which revealed chaotic oscillations. In contrast to the controls, the intracisternal injection of C5a caused a significant decrease of the analytical index and reduced its reproducibility significantly. This result suggests a subtle central-autonomic dysfunction and a loss of the autonomic steady-state induced by the acute inflammatory process.

Widenings of the myelin lamellae in a typical Guillain-Barré syndrome

The so-called "widening of the myelin lamellae" are thought to be specific ultrastructural features of peripheral nerve myelin in patients with peripheral neuropathy associated with a monoclonal dysglobulinemia of IgM type and antiglycolipid activity. We report here a case of Guillain-Barré syndrome with no evidence of serum monoclonal dysglobulinemia, presenting the typical widenings of the myelin lamellae in small-diameter myelinated fibers from a sural nerve biopsy. In view of the positive reaction with anti-C3d complement on direct immunofluorescence, an immunological mechanism may be involved in the widenings of the myelin lamellae.

Antibody of patients with Guillain-Barré syndrome mediates complement-dependent cytolysis of rat Schwann cells: susceptibility to cytolysis reflects Schwann cell phenotype

We previously observed that demyelination of dissociated dorsal root ganglion cultures by acute phase serum of some Guillain Barré syndrome (GBS) patients was associated with cytolysis of rat Schwann cells (SC) not committed to myelination. In this study, to determine if SC cytolysis was antibody (Ab) and complement-dependent and if SC at various stages of differentiation were uniformly susceptible, sciatic nerve SC from 1-2-day-old (SC/2d) or 6-day-old (SC/6d) Sprague Dawley rats were sensitized with IgM from GBS patients or normal controls and incubated at 37 degrees C for 60 min with 25% guinea pig serum complement. Cytolysis was detected by vital dye exclusion. IgM Ab of 11 GBS patients induced complement-mediated cytolysis of 10.7-64.1% SC/2d (38.3 +/- 18.8; mean +/- SD) which was significantly higher than cytolysis of SC/6d (8.5-32%) or that by normal controls (15.0 +/- 15.2 SC/2d; 8.3 +/- 3.3 SC/6d mean +/- SD, n = 11). Culture of SC/6d increased their cytolysis by IgM plus complement to the levels similar to that of SC/2d. FACS analysis suggested that the greater sensitivity of SC/2d to cytolysis did not reflect greater antibody binding since 2.6-fold less GBS IgM was required to initiate SC/2d lysis compared to SC/6d. This suggested that the less differentiated SC were more susceptible to complement-mediated cytolysis.

Guillain-Barré syndrome following immunisation with Haemophilus influenzae type b conjugate vaccine

The Guillain-Barré syndrome (GBS) is an immune-mediated disease often associated with viral or bacterial infections and with immunisation. IgM antibodies have been implicated as the main trigger event in GBS. So far, only four cases of GBS have been observed following immunisation with a conjugate vaccine against Haemophilus influenzae type b. We report another patient with GBS after this vaccination. We measured immunoglobulins against the H. influenzae type b polysaccharide (PRP) component of the vaccine. Surprisingly the anti-PRP IgM antibody level was markedly elevated (100 micrograms/ml) in the plasma of this patient. We speculate that an excessive anti-PRP IgM antibody response to the vaccine might be the cause of GBS.

IgG monoclonal paraproteinaemia and peripheral neuropathy

Five patients with peripheral neuropathy and benign IgG monoclonal paraproteinemia are reported, all of whom had a sensorimotor neuropathy with a remitting and relapsing course. The serum paraprotein level did not correlate with the patient's clinical status. Electrophsyiological studies showed marked slowing of conduction velocity and conduction block in four of the patients and mild slowing in the other. Sural nerve biopsies demonstrated a demyelinating neuropathy with inflammatory cell infiltrates in each of the five patients. Three of the patients had evidence of myelin/Schwann cell reactivity on immunofluorescence studies and in all nerves dense expression of major histocompatability complex class I and II molecules was evident within the endoneurium, on invading mononuclear cells, endothelial cells and Schwann cells. All the patients responded to treatment, plasmapheresis being particularly effective. Four patients have achieved prolonged remissions after all treatment had ceased. These five cases of peripheral neuropathy and IgG paraproteinaemia were identical in their clinical, electrophysiological and pathological features to patients with chronic inflammatory demyelinating polyneuropathy.

Seric immune complexes in multiple sclerosis do not contain MBP epitopes

Immune complexes from sera of MS patients, other neurological diseases, and healthy donors were precipitated using polyethyleneglycol and analyzed by sodium dodecylsulfate-polyacrylamide gel electrophoresis. Silver staining evidenced additional protein bands whose molecular weights were 14-16, 38, and 43 kDa. These IC proteins were present in most MS patients studied. To identify their nature, immunoblotting was performed with antihuman immunoglobulins A, M, G antibodies. No immunoreactivity was found below a molecular weight of 66 kDa on a nitrocellulose sheet having the transferred protein pattern of MS IC. Using purified human myelin, MS IC transferred to an immobilon sheet and antihuman myelin basic protein antibodies, an immunoreactivity was seen only on purified human MBP. The small proteins of 14-16 kDa and the others of 38, 43 kDa were not immunoreactive. Identification of the nature of these additional proteins in MS IC is in progress.

High-dose intravenous immunoglobulin in the treatment of Guillain-Barré syndrome: a preliminary open study

We report the effects of intravenous gamma-globulin (IVGG) in severe Guillain-Barré syndrome (GBS) in a small open study. Seven patients were given IVGG (0.4 g/kg/day) for 5 consecutive days. At the start of treatment all had progressing limb weakness and none could stand unaided. Within 24 h all but one patient started to improve, without the expected plateau phase, and progress was maintained with a mean time to independent walking of 14 days. One patient started treatment 9 h prior to ventilation for 15 days but was walking independently 31 days after admission. This study provides further evidence that IVGG is a promising therapeutic alternative to plasmapheresis in GBS. The rapidity of the response to IVGG raises the possibility that a single dose regimen might be equally or more effective.

Inflammatory mediators in demyelinating disorders of the CNS and PNS

Work in both experimental models and human disorders of the central and peripheral nervous system has delineated multiple effector mechanisms that operate to produce inflammatory demyelination. The role of various soluble inflammatory mediators generated and released by both blood-borne and resident cells in this process will be reviewed. Cytokines such as interleukin (IL)-1, interferon (IFN)-gamma, and tumor necrosis factor (TNF)-alpha are pivotal in orchestrating immune and inflammatory cell-cell interactions and represent potentially noxious molecules to the myelin sheath, Schwann cells, and/or oligodendrocytes. Arachidonic acid metabolites, synthesized by and liberated from astrocytes, microglial cells and macrophages, are intimately involved in the inflammatory process by enhancing vascular permeability, providing chemotactic signals and modulating inflammatory cell activities. Reactive oxygen species can damage myelin by lipid peroxidation and may be cytotoxic to myelin-producing cells. They are released from macrophages and microglial cells in response to inflammatory cytokines. Activation of complement yields a number of inflammatory mediators and results in the assembly of the membrane attack complex that inserts into the myelin sheath-creating pores. Activated complement may contribute both to functional disturbance of neural impulse propagation, and to full-blown demyelination. Proteases, abundantly present at inflammatory foci, can degrade myelin. Vasoactive amines may play an important role in breaching of the blood-brain/blood-nerve barrier. The importance of nitric oxide metabolites in inflammatory demyelination merits investigation. A better understanding of the multiple effector mechanisms operating in inflammatory demyelination may help to devise more efficacious antigen non-specific therapy.

Antibody-mediated neurological disease

The number of neurological disorders in which autoantibodies are thought to play a pathogenic role continues to increase although the strength of the evidence varies. Many of the disorders are tumour associated.

Presence of the terminal complement complex (C5b-9) precedes myelin degradation in immune-mediated demyelination of the rat peripheral nervous system

In this study, the terminal complement complex C5b-9 (TCC) was localized by immunocytochemistry at different clinical stages of experimental autoimmune neuritis. Deposits of TCC were found on the surface of Schwann cells and their myelin sheaths, and to some extent in the extracellular space at predilective sites of impending demyelination before onset of clinical signs and for a short period thereafter. Additionally, TCC was deposited on the surface of W3/13 positive leukocytes. No TCC immunoreactivity was seen in the distal stump of transected sciatic nerves 1 to 15 days after axotomy. The early and transient deposition of TCC on Schwann cells and myelin sheaths in experimental autoimmune neuritis before overt demyelination suggests that complement activation plays a pathogenic role in the initiation of immune-mediated myelin damage. The lack of TCC immunoreactivity after nerve transection excludes a nonspecific activation process. The signals involved in local TCC formation in demyelinating peripheral nervous system disorders have yet to be explored.

Clinical and serological studies in a series of 45 patients with Guillain-Barré syndrome

We retrospectively reviewed the clinical files of 45 Guillain-Barré syndrome (GBS) patients admitted to our Department between 1979 and 1989. The age distribution was bimodal with a first peak in young adults (20-40 years), and a second one between 60 to 70 years. Seasonal distribution showed a late fall and a hivernal predominance. Three patients experienced a second attack of GBS 2-9 years after the first one. Thirty-one (69%) presented antecedent events, most often a respiratory tract infection (n = 20) or enteritis (n = 6). Serological studies were systematically performed, including antibody titers against herpes simplex virus, Epstein-Barr virus, cytomegalovirus (CMV), respiratory syncytial virus, human immunodeficiency virus, Mycoplasma pneumoniae, Campylobacter jejuni/coli and cardiolipin. These studies showed the presence of antibodies indicative of a CMV primary infection in 22% cases and of a Campylobacter jejuni/coli infection in 13%. Co-infection was observed in 3 cases. Serology remained negative in 12 patients with a preceding respiratory infection. There was no correlation between serology and the severity of the disease. Absence of antecedent events and of positive anti-infectious serology was observed in only 10 patients.