Ultrastructural effects of Guillain-Barré serum in cultures containing only rat Schwann cells and dorsal root ganglion neurons

Role of cytokines and Toll-like receptors in the immunopathogenesis of Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is an autoimmune disease of the peripheral nervous system, mostly triggered by an aberrant immune response to an infectious pathogen. Although several infections have been implicated in the pathogenesis of GBS, not all such infected individuals develop this disease. Moreover, infection with a single agent might also lead to different subtypes of GBS emphasizing the role of host factors in the development of GBS. The host factors regulate a broad range of inflammatory processes that are involved in the pathogenesis of autoimmune diseases including GBS. Evidences suggest that systemically and locally released cytokines and their involvement in immune-mediated demyelination and axonal damage of peripheral nerves are important in the pathogenesis of GBS. Toll-like receptors (TLRs) link innate and adaptive immunity through transcription of several proinflammatory cytokines. TLR genes may increase susceptibility to microbial infections; an attenuated immune response towards antigen and downregulation of cytokines occurs due to mutation in the gene. Herein, we discuss the crucial role of host factors such as cytokines and TLRs that activate the immune response and are involved in the pathogenesis of the disease.

Plasma immunoadsorption therapy for Guillain-Barré syndrome: critical day for initiation

Immunoadsorption plasmapheresis (IAPP) is a method of removing circulating immune factors that is used to treat Guillain-Barré syndrome (GBS). We retrospectively analyzed the data on our GBS patients. In 21 patients treated with IAPP, linear regression analysis showed that the time from the onset of symptoms to the initiation of IAPP was correlated with the time required for improvement by one Hughes functional grade. We investigated the critical day for initiating treatment, which we defined as the day when initiation of IAPP was significantly more likely to improve function by at least one Hughes grade when compared with the outcome in patients receiving supportive therapy (non-IAPP group). The critical day was found to be day 6 after the onset of GBS.

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.

Neuromuscular blockade by IgG antibodies from patients with Guillain-Barré syndrome: a macro-patch-clamp study

Guillain-Barré syndrome (GBS) is often associated with serum antibodies to glycoconjugates such as GM1 and GQ1b. The pathogenic role of these antibodies and other serum factors has not yet been clarified. We have investigated the effect of serum, plasma filtrate, and highly purified IgG and IgM from 10 patients with typical GBS on motor nerve terminals in the mouse hemidiaphragm. Quantal endplate currents were recorded by means of a perfused macro-patch-clamp electrode. The plasma filtrate of all GBS patients led to a 5- to 20-fold reduction of evoked quantal release within 7 to 15 minutes of continuous superfusion. In 4 patients, the amplitudes of single quanta were clearly reduced (by 10-66% of control values), indicating an additional postsynaptic action. Blocking effects could be reversed to a variable degree within 15 to 18 minutes after washout. Purified IgG was as effective as native serum, whereas a purified GBS IgM fraction did not block transmission. Sera from convalescent patients and IgG from healthy subjects were without blocking effect. The effects were complement independent and there was no link to the presence (in 6 patients) or absence (in 4 patients) of detectable antibodies to GM1 or GQ1b. In GBS, antibodies to an undetermined antigen depress the presynaptic transmitter release and, in some cases, the activation of postsynaptic channels. We suggest that weakness in the acute stage of GBS may be caused in part by circulating antibodies.

Campylobacter species and Guillain-Barré syndrome

Since the eradication of polio in most parts of the world, Guillain-Barré syndrome (GBS) has become the most common cause of acute flaccid paralysis. GBS is an autoimmune disorder of the peripheral nervous system characterized by weakness, usually symmetrical, evolving over a period of several days or more. Since laboratories began to isolate Campylobacter species from stool specimens some 20 years ago, there have been many reports of GBS following Campylobacter infection. Only during the past few years has strong evidence supporting this association developed. Campylobacter infection is now known as the single most identifiable antecedent infection associated with the development of GBS. Campylobacter is thought to cause this autoimmune disease through a mechanism called molecular mimicry, whereby Campylobacter contains ganglioside-like epitopes in the lipopolysaccharide moiety that elicit autoantibodies reacting with peripheral nerve targets. Campylobacter is associated with several pathologic forms of GBS, including the demyelinating (acute inflammatory demyelinating polyneuropathy) and axonal (acute motor axonal neuropathy) forms. Different strains of Campylobacter as well as host factors likely play an important role in determining who develops GBS as well as the nerve targets for the host immune attack of peripheral nerves. The purpose of this review is to summarize our current knowledge about the clinical, epidemiological, pathogenetic, and laboratory aspects of campylobacter-associated GBS.

Human autoimmune neuropathies

Peripheral nerve diseases are among the most prevalent disorders of the nervous system. Because of the accessibility of the peripheral nervous system (PNS) to direct physiological and pathological study, neuropathies have traditionally played a unique role in developing our understanding of basic mechanism of nervous system injury and repair. At present they are providing new insight into the mechanisms of immune injury to the nervous system. A rapidly growing catalogue of PNS disorders are now suspected to be immune-mediated, and in the best understood of these disorders, the molecular and cellular targets of immune attack are known, and the pathophysiology follows directly from the specific immune injury. This review summarizes the immunologically relevant features of the PNS, then considers selected immune-mediated neuropathies, focusing on pathogenetic mechanisms. Finally, the PNS is providing a testing ground for new immunotherapies and approaches to protection and regeneration, including the use of trophic factors. The current status of treatment and implications for future approaches is reviewed.

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.

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.

Effects of Guillain-Barré sera containing antibodies against glycolipids in cultures of rat Schwann cells and sensory neurons

Serum samples from 52 patients with the acute Guillain-Barré syndrome (GBS), 19 patients with other neurological disorders, and 18 healthy volunteers were tested for cytotoxicity in cultures of rat Schwann cells and dorsal root ganglion neurons. The samples were also examined by enzyme-linked immunosorbent assay for IgG and IgM antibodies against various acidic and neutral glycolipids. Samples from 16 of the 52 (31%) acute GBS patients and from 1 of the 6 patients with chronic inflammatory demyelinating polyneuropathy produced myelin breakdown in culture. Although 10 of the 16 cytotoxic acute GBS serum samples contained anti-glycolipid immunoglobulins, there was no correlation in individual samples between cytotoxic activity and the presence of antibodies against specific glycolipids. While our results do not exclude a role for anti-glycolipid antibodies in the pathogenesis of the acute GBS, the cytotoxic effects of acute GBS serum in cultures of Schwann cells and sensory neurons are probably not due to these antibodies alone.

Antibodies to acidic glycolipids in Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy

Using an enzyme-linked immunosorbent assay and a thin-layer chromatography-immunostaining procedure, we detected serum antibodies against acidic glycolipids in 36 of 53 patients with Guillain-Barré syndrome (GBS) and 8 of 16 patients with chronic inflammatory demyelinating polyneuropathy (CIDP). Although we also found anti-acidic glycolipid antibodies in 4 of 13 patients with other neurological diseases; 2 of 10 patients with multiple sclerosis; 8 of 33 patients with inflammatory, infectious, allergic or autoimmune disorders and 3 of 32 healthy subjects, the levels of antibodies in these controls were much lower than in GBS patients. There were several patterns of reactivity of GBS sera including antibodies to LM1 and HexLM1, GM1 or GD1b or both, various other gangliosides, sulfated glycolipids, and as yet unidentified glycolipids. Sera from 30% of GBS patients had antibodies against two or more antigenically distinct acidic glycolipid antigens. Levels of anti-acidic glycolipid antibodies correlated with clinical symptoms in 9 of 11 GBS patients. While the increased incidence of antibodies to acidic glycolipids in patients with GBS (P less than 0.001) and CIDP (P less than 0.025) compared to controls could be an epiphenomenon, anti-acidic glycolipid antibodies may play a role in nerve injury in some GBS and CIDP patients.

Anti-GM1 IgA antibodies in Guillain-Barré syndrome

Serum anti-GM1 IgA antibodies were detected in 15 of 53 (28%) patients with the acute Guillain-Barré syndrome (GBS) and in one of 26 (4%) patients with other neurological diseases. Although nine GBS patients had anti-GM1 IgA titers of 1:200 or less, six patients had titers of 1:800 or more. Some GBS patients with anti-GM1 IgA antibodies also had antibodies against GD1b or GM2 or both. The presence of markedly elevated anti-GM1 IgA was associated with a poor clinical outcome at 6 and 12 months following onset of the GBS. The possible pathogenetic role of anti-GM1 IgA antibodies remains to be established.

Antibodies to sulfated glycolipids in Guillain-Barré syndrome

Sera from 53 patients with acute Guillain-Barré syndrome (GBS), 15 patients with chronic inflammatory demyelinating polyneuropathy (CIDP), 13 patients with other neurological diseases (OND) and 31 healthy controls were tested for IgM and IgG antibodies to sulfoglucuronyl paragloboside (SGPG) and sulfatide by both an ELISA and a thin-layer chromatogram-overlay technique. Although the mean levels of anti-SGPG or anti-sulfatide antibodies in GBS patients were not elevated compared to controls, the occurrence of anti-SGPG antibodies was more frequent in GBS patients than in controls (P less than 0.02). Acute GBS patients with antibodies to SGPG or sulfatide were clinically indistinguishable from other GBS patients. Our data suggest that elevated levels of antibodies to SGPG could be important in the pathogenesis of neuropathy in some GBS patients.

In vitro demyelination by serum antibody from patients with Guillain-Barré syndrome requires terminal complement complexes

Serum from 7 patients who had acute-phase Guillain-Barré syndrome with high anti-peripheral nerve myelin antibody activity (54 to 210 units/ml) was compared with serum from 3 patients in the recovery phase (0 to 17 units/ml) and serum from 7 disease control subjects (0 to 24 units/ml) and 7 normal control subjects (0 to 7 units/ml) for its ability to demyelinate rodent dorsal root ganglion cultures. The demyelinating capacity of each serum was quantitated by counting the percent of damaged internodal segments in each of four cultures. All sera from patients in the acute phase GBS caused 50 to 78% demyelination, in contrast with 6 to 19% by the sera from all 3 patients in the recovery phase and all other control subjects. The degree of demyelination correlated with anti-peripheral nerve myelin antibody activity of the sera and demyelination was complement-dependent. Further, cultures were treated with an immunoglobulin M (IgM) fraction of an acute-phase Guillain-Barré syndrome plasma plus normal human serum depleted of complement component C7. Only those cultures treated with IgM and C7-depleted human serum reconstituted with purified C7 resulted in 50.8% demyelination, which was significantly greater than the 14.2 to 16.2% demyelination observed in the presence of heat-inactivated, C7-depleted human serum plus purified C7 or in the absence of C7 or antibody. In summary, our work suggests that anti-peripheral nerve myelin antibody in Guillain-Barré syndrome mediated complement dependent-demyelination of rodent dorsal root ganglion cultures. Further, this in vitro demyelination required generation of activation complexes of the terminal complement cascade.

Search for antibodies to neutral glycolipids in sera of patients with Guillain-Barré syndrome

Sera from 54 patients with Guillain-Barré syndrome (GBS), 34 patients with other neurological diseases (OND) and 32 healthy controls were tested for antibodies to total lipid fractions and higher neutral glycolipid fractions isolated from human and dog nerves, purified Forssman glycolipid and a panel of purified neutral glycolipids by both an enzyme-linked immunosorbent assay (ELISA) and a thin-layer chromatogram (TLC)-overlay technique. IgM and IgG antibodies to total lipid fractions, as well as to galactocerebroside, ceramide dihexoside, ceramide trihexoside, and globoside were not significantly elevated in the sera of GBS patients as compared to controls. High levels of anti-asialo-GM1 IgG antibodies, however, were detected in 6 of 54 (11%) GBS patients and 1 of 30 (3%) OND patients. Intense reactivity with purified Forssman glycolipid and a number of glycolipid antigens in higher neutral glycolipid enriched fractions of human cauda equina and dog sciatic nerves was noted by TLC-immunostaining in many GBS and control sera. Although the levels of anti-Forssman IgM were significantly decreased in GBS sera compared with normal sera (P less than 0.05) and OND sera (P less than 0.02), the levels of anti-Forssman IgG antibodies were not significantly different. With the possible exception of IgG antibodies to asialo-GM1, our results suggest that serum antibodies against Forssman glycolipid and neutral glycolipids are not significantly elevated in GBS patients and, thus, are unlikely to play an important role in the pathogenesis of this disease.

Treatment of Guillain-Barré syndrome with anti-T cell monoclonal antibodies

Three patients with acute Guillain-Barré syndrome were treated early in the course of the disease with OKT3, an anti-T-cell monoclonal antibody. Each patient developed acute lymphopenia with specific depletion of T3-positive lymphocytes. Two patients had continued progression of clinical deficits for eight and 14 days. This suggests that T lymphocytes may not be essential for progression of Guillain-Barré syndrome at this stage of the disease.

Human alpha tumor necrosis factor does not damage cultures containing rat Schwann cells and sensory neurons

The effects of recombinant human alpha tumor necrosis factor (alpha-TNF) were compared with those of cytotoxic serum from patients with the acute Guillain-Barré syndrome (GBS) in myelinated cultures containing only rat Schwann cells and dorsal root ganglion neurons. Alpha-TNF did not damage rat peripheral nervous system tissue in culture. These observations suggest that alpha-TNF is not responsible for the cytotoxic activity of acute GBS serum in culture.

Effects of A23187 in cultures containing only rat Schwann cells and sensory neurons

Serum from approximately 40% of patients with the acute Guillain-Barré syndrome (GBS) selectively destroys myelin and myelin-related Schwann cells in cultures containing only rat dorsal root ganglion neurons and Schwann cells. To determine if the effects of GBS serum on myelin and myelin-related Schwann cells could be mediated through elevations in the intracellular concentration of calcium ions, we compared the effects of cytotoxic serum to A23187, a divalent cation ionophore. Both myelin- and nonmyelin-related Schwann cells were killed along with neurons in the presence of A23187 and extracellular calcium ions. Myelin sheaths also underwent vesicular disruption. The ultrastructural appearance of myelin and myelin-related Schwann cell lysis caused by A23187 were essentially identical to damage produced by GBS serum. These observations suggest that GBS serum factors might damage myelin and myelin-related Schwann cells in culture by an increase in myelin-related Schwann cell permeability to extracellular calcium ions. In contrast, A23187 causes necrosis of Schwann cells and neurons as well as myelin lysis by a nonselective increase in membrane permeability to extracellular calcium ions.

Effects of ethanol on rat Schwann cell proliferation and myelination in culture

It is possible to treat dissociated embryonic rat dorsal root ganglia in culture to inhibit proliferation of all nonneuronal cells except Schwann cells. Neurons have been shown to produce a mitogenic stimulus for Schwann cells under these conditions. Additionally, myelin-competent neurons induce Schwann cells to elaborate myelin sheaths. Groups of sibling cultures were exposed to various nonlethal concentrations of ethanol (0, 43, 86, or 172 mM) for 4 wk. Cultures were assessed weekly by light microscopy in a blind fashion for evidence of Schwann cell proliferation and myelin formation. Ethanol adversely affected both Schwann cell proliferation and myelin formation in culture. No obvious differences in neuronal morphology were observed among the various groups of cultures by light or electron microscopy. These observations suggest that ethanol might interfere with Schwann cell proliferation and myelin formation in culture by one or both of the following means: a) inhibit neuronal production of signals for Schwann cell proliferation and myelination or b) impede Schwann cell responses to neuronal signals. Investigation of these possibilities in culture may provide insight into neuropathologic mechanisms operative in the fetal alcohol syndrome or alcohol-associated peripheral neuropathy in humans.

The acute response of Schwann cells to taxol after nerve crush

The effect of taxol, an antimitotic drug which stabilizes microtubules and promotes their assembly, was studied with regard to Schwann cells over a 4-week period following a crush injury to rat sciatic nerve. A single intraneural injection of taxol in dimethyl sulfoxide (DMSO) was given immediately after the crush into the site of injury in one sciatic nerve and was compared with the other side which was crushed but injected with DMSO only. Sampled sites were taken proximal and distal to the lesion, as well as from the lesion itself, and studied by light and electron microscopy. The Schwann cell response was most marked during the degenerative phase immediately following the crush. At this time, there was a decrease of all cytoplasmic structures except microtubules and smooth endoplasmic reticulum. At the site of the crush lesion in taxol-treated nerves, Schwann cells possessed accumulations of myelin debris and lipid droplets. Mitotic Schwann cells were also engorged with myelin breakdown products. Multinucleated Schwann cells, believed to be the result of abnormal mitotic activity, were also apparent and were filled with large numbers of cytoplasmic microtubules. The latter were sometimes regularly arranged around phagocytosed or intracytoplasmic debris. Some recovery from the crush injury was noted with time, although the number of Schwann cells was much lower than would have been anticipated in the absence of taxol, in that long stretches of naked axon bundles were common and microtubule-related abnormalities persisted up to 4 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)