Suppression of P2-T cell line-mediated experimental autoimmune neuritis by interleukin-2 receptor targeted monoclonal antibody ART 18

Expanding our understanding of Guillain-Barré syndrome: Recent advances and clinical implications

Guillain-Barré syndrome (GBS) is a rare yet potentially life-threatening disorder of the peripheral nervous system (PNS), characterized by substantial clinical heterogeneity. Although classified as an autoimmune disease, the immune mechanisms underpinning distinct GBS subtypes remain largely elusive. Traditionally considered primarily antibody-mediated, the pathophysiology of GBS lacks clarity, posing challenges in the development of targeted and effective treatments. Nevertheless, recent investigations have substantially expanded our understanding of the disease, revealing an involvement of autoreactive T cell immunity in a major subtype of GBS patients and opening new biomedical perspectives. This review highlights these discoveries and offers a comprehensive overview of current knowledge about GBS, including ongoing challenges in disease management.

Effects of isoflurane anesthesia on F-waves in the sciatic nerve of the adult rat

INTRODUCTION

Nerve conduction studies provide insights into the functional consequences of axonal and myelin pathology in peripheral neuropathies. We investigated whether isoflurane inhalation anesthesia alters F-wave latencies and F-persistence in the sciatic nerve of adult rats.

METHODS

Ten rats were investigated at 3 different isoflurane concentrations followed by ketamine-xylazine injection anesthesia. To assess F-wave latencies, a stimulation paradigm was chosen to minimize H-reflex masking of F-waves.

RESULTS

F-wave persistence rates were reduced with 3.5% isoflurane concentration at 4 and 10 Hz supramaximal stimulation and marginally reduced with 2.5% isoflurane when compared with ketamine-xylazine. F-wave amplitudes decreased progressively with rising stimulus frequency in all types of anesthesia and most at 3.5% isoflurane concentration.

CONCLUSIONS

The type of anesthesia and the stimulus repetition rate have an impact on some F-wave parameters. Higher isoflurane concentrations and repetition rates are not recommended in experimental studies using rat neuropathy models where F-waves are of interest.

Pathogenesis of Guillain–Barré syndrome

Guillain-Barre syndrome is a postinfectious disorder caused by an aberrant immune response to an infectious pathogen, resulting in an autoimmune disease. As with other autoimmune diseases of infectious nature, the intricate balance of the numerous factors involved in the immune response may determine the outcome of the interaction between the microbe and host. Recent studies focusing on the role of cytokines and its network of related mediators and receptors suggest that any imbalance may make a significant contribution to the outcome of the infectious disease process. Better understanding of the pathogenesis of Guillain-Barre syndrome may lead to the discovery of newer therapeutics and may also serve as a model for studying other autoimmune diseases.

Immune mechanisms in acquired demyelinating neuropathies: lessons from animal models

The peripheral nervous system (PNS) is the target for a heterogenous immune attack mediated by T-cells, B-cells, and macrophages. The interaction of the humoral and cellular immune system with the structural components in the peripheral nervous system may determine the extent of inflammation and possibly repair mechanisms. The animal model experimental autoimmune neuritis (EAN) allows detailed study of the various effector pathways and tests novel therapeutic strategies in vivo. Unexpectedly, involvement of the immune system is also found in animal models for inherited neuropathies and in its human counterpart Charcot-Marie-Tooth (CMT) disease, suggesting an autoimmune reaction triggered by the genetically determined demyelinating disorder. A better understanding of immune regulation and its failure in the peripheral nervous system may help to develop more specific and more effective immunotherapies.

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.

Cytokine production and the pathogenesis of experimental autoimmune neuritis and Guillain-Barré syndrome

Acute inflammatory demyelinating polyradiculoneuropathy (Guillain-Barré syndrome, GBS) and its animal model experimental autoimmune neuritis (EAN) are prototypes of T cell-mediated autoimmune diseases affecting the peripheral nervous system (PNS). Perivascular accumulation of macrophages and T lymphocytes in the PNS, and high levels systemically of PNS myelin antigen-reactive T cells are characteristic features of both diseases, thereby suggesting a pathogenic role for immunoregulatory cytokines. Here we summarise recent studies that have clearly documented that Th1/Th2/Th3 cytokines are differently upregulated during various clinical phases of EAN and GBS. The observations indicate that the role of cytokines in immune regulation and autoimmune disease is more complex than a simple Th1-Th2 dichotomy would suggest. New treatments may be searched for that counteract this complex cytokine imbalance. Treatments with antibodies that selectively target certain pro-inflammatory cytokines, as well as with immunomodulatory preparations that promote cytokines that beneficially influence the disease course should be in focus of future therapeutic trials.

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.

Interactions between CD4+ T-cells and rat Schwann cells in vitro. 1. Antigen presentation by Lewis rat Schwann cells to P2-specific CD4+ T-cell lines

Interactions between CD4+ P2-specific T-cell lines and Schwann cells were examined in vitro by scanning electron microscopy (SEM) and T-cell proliferation studies. CD4+ T-cell lines clustered around and attached to Schwann cells which expressed Major histocompatibility complex (MHC) class II molecules. Only those P2-specific T-cell lines capable of inducing experimental allergic neuritis (EAN) when injected into adult Lewis rats clustered around the Schwann cells. T-cell lines responsive to P2 but not able to induce EAN did not cluster around Schwann cells. The addition of exogenous P2 protein inhibited in a dose-dependent way clustering and proliferation of the P2-specific T-cell lines. Cytoplasmic P2 was detected in Schwann cells by immunofluorescent labelling and the results of proliferation assays in this study suggest that endogenous P2 protein was processed by the Schwann cells and presented to T-cell lines in association with MHC class II molecules. The clustering and proliferation of class II-restricted CD4+ P2-specific T-cell lines in the presence of Schwann cells provides evidence for a role for Schwann cells as facultative antigen presenting cells, processing and presenting 'self' endogenous antigen to CD4+ T-cell lines capable of inducing EAN.

Cerebrospinal fluid pheresis in Guillain Barré syndrome

While plasmapheresis is established in the treatment of acute polyneuroradiculitis, disabling pareses may last long, persisting neurological deficits remain frequent, and costs and side-effects are considerable. Repeated filtration of cerebrospinal fluid may remove pathogenetically relevant cells and polypeptides. Observations in 12 severe Guillain-Barré patients treated with CSF pheresis indicate that it is a safe and effective procedure. We hypothesize mechanisms of action of and potential indications for CSF pheresis as a more general concept. In inflammatory demyelinating polyneuropathy, CSF filtration could be combined with 'dynamic' cerebrospinal fluid pheresis, intravenous immunoglobulin therapy, cryoprecipitation, and/or immuno-adsorption to increase its effectiveness.

The role of complement in myelin phagocytosis during PNS wallerian degeneration

Myelin removal in nerves undergoing wallerian degeneration mainly depends on invading, non-resident macrophages. The present study clarifies the role of serum complement components in this process in vitro and in vivo. Macrophages cocultured with degenerating nerves in vitro were unable to invade these nerves in the presence of C3-deficient serum. Application of C3-deficient serum subsequent to cellular invasion abolished the myelin phagocytic capacity of the invaded macrophages. This indicates that opsonization of myelin by complement components is necessary in myelin ingestion via macrophage receptors. In vivo, a monoclonal antibody to the macrophage complement receptor type 3 (CR3) significantly reduced myelin phagocytosis. Immunohistochemistry with anti-C3 antibodies showed a marked reaction in degenerating nerves. Immunoelectron microscopy localized C3 particles at the degenerating myelin sheaths. Haematogenous cells, invading the degenerating nerves, also showed a strong reaction for C3 in their cytoplasm. These results indicate that complement components play a critical role both in macrophage invasion of degenerating nerves and in the ingestion of myelin by these cells.

T-cell and macrophage activation in experimental autoimmune neuritis and Guillain-Barré syndrome

Evidence implicating cellular immune responses in the pathogenesis of experimental autoimmune neuritis (EAN) and Guillain-Barré syndrome (GBS) is reviewed. In EAN the decisive role of T-lymphocytes in the initiation of immune-mediated nerve damage has been firmly established by adoptive transfer experiments. Macrophages but not Schwann cells express major histocompatibility complex class II gene products in situ and hence may function as antigen presenters. Macrophages are crucial in the amplification and effector phase and damage the myelin sheath by phagocytic attack and release of inflammatory mediators such as toxic oxygen radicals, arachidonic acid metabolites, complement, or hydrolases. Macrophage activation in EAN is achieved by interferon-gamma. Attempts to detect specific sensitization of T-lymphocytes to nerve antigens in patients with GBS have so far been unsuccessful. However, circulating activated T cells can be found in patients with GBS, as evidenced by augmented expression of HLA-DR antigen, the transferrin receptor, and the interleukin-2 receptor on the surface of peripheral blood T cells, and by increased serum concentrations of interleukin-2 and the soluble interleukin-2 receptor. In addition, we present data indicating macrophage activation in GBS.