Suppression of Myasthenia Gravis by Antigen-Specific Mucosal Tolerance and Modulation of Cytokines and Costimulatory Factors

Expression of lymphocyte activation gene-3 on CD4+T cells is regulated by cytokine interleukin-18 in myasthenia gravis

Myasthenia gravis (MG) is a T cell-dependent, B cell-mediated, and complement-dependent autoimmune disease. Lymphocyte activation gene-3 (LAG-3; CD223) is an immune checkpoint protein that plays an important role in maintaining autoimmune tolerance and homeostasis. To investigate the cytokine-regulated expression pattern of LAG-3, CD4+T cells were sorted from the peripheral blood of healthy volunteers by density gradient centrifugation and stimulated with various cytokines in vitro. The expression of membrane LAG-3 (mLAG-3), membrane a disintegrin and metallopeptidase domain10 (mADAM10) and membrane ADAM17 (mADAM17) on CD4+T cells was detected by flow cytometry; the concentration of soluble LAG-3 (sLAG-3) was detected by ELISA; and the relative expression of genes at the transcriptional level was detected by fluorescence quantitative RT-PCR (qRT-PCR). sLAG-3 levels were significantly increased in the peripheral plasma of AChR Ab-positive patients with MG compared to healthy volunteers, while the percentage of mLAG-3 expression on CD4+T lymphocytes in the peripheral blood of patients with MG was significantly reduced. IL-18 inhibited mLAG-3 levels on CD4+T cells in a concentration-dependent manner. Additionally, the concentration of sLAG-3 in the supernatant increased. After PHA and IL-18 stimulation, ADAM10 and ADAM17 also increased compared to those in the PHA-active group. Moreover, there were significant differences in the expression of mADAM10 and mADAM17 in CD4+T lymphocytes between patients with MG and healthy volunteers. These results suggest that IL-18 may regulate the expression pattern of mLAG-3 in CD4+T cells and sLAG-3 via ADAM10- and ADAM17-mediated pathways, thus affecting the immune effects of CD4+T cells. This study provides a preliminary exploration of the upstream regulatory molecules of the LAG-3 and IL-18/LAG-3 signalling pathways for potential targeted therapy of autoimmune diseases in the future.

Interleukin-18 cytokine in immunity, inflammation, and autoimmunity: Biological role in induction, regulation, and treatment

Interleukin-18 (IL-18) is a potent pro-inflammatory cytokine involved in host defense against infections and regulates the innate and acquired immune response. IL-18 is produced by both hematopoietic and non-hematopoietic cells, including monocytes, macrophages, keratinocytes and mesenchymal cell. IL-18 could potentially induce inflammatory and cytotoxic immune cell activities leading to autoimmunity. Its elevated levels have been reported in the blood of patients with some immune-related diseases, including rheumatoid arthritis, systemic lupus erythematosus, type I diabetes mellitus, atopic dermatitis, psoriasis, and inflammatory bowel disease. In the present review, we aimed to summarize the biological properties of IL-18 and its pathological role in different autoimmune diseases. We also reported some monoclonal antibodies and drugs targeting IL-18. Most of these monoclonal antibodies and drugs have only produced partial effectiveness or complete ineffectiveness in vitro, in vivo and human studies. The ineffectiveness of these drugs targeting IL-18 may be largely due to the loophole caused by the involvement of other cytokines and proteins in the signaling pathway of many inflammatory diseases besides the involvement of IL-18. Combination drug therapies, that focus on IL-18 inhibition, in addition to other cytokines, are highly recommended to be considered as an important area of research that needs to be explored.

IgG4 Autoantibodies in Organ-Specific Autoimmunopathies: Reviewing Class Switching, Antibody-Producing Cells, and Specific Immunotherapies

Organ-specific autoimmunity is often characterized by autoantibodies targeting proteins expressed in the affected tissue. A subgroup of autoimmunopathies has recently emerged that is characterized by predominant autoantibodies of the IgG4 subclass (IgG4-autoimmune diseases; IgG4-AID). This group includes pemphigus vulgaris, thrombotic thrombocytopenic purpura, subtypes of autoimmune encephalitis, inflammatory neuropathies, myasthenia gravis and membranous nephropathy. Although the associated autoantibodies target specific antigens in different organs and thus cause diverse syndromes and diseases, they share surprising similarities in genetic predisposition, disease mechanisms, clinical course and response to therapies. IgG4-AID appear to be distinct from another group of rare immune diseases associated with IgG4, which are the IgG4-related diseases (IgG4-RLD), such as IgG4-related which have distinct clinical and serological properties and are not characterized by antigen-specific IgG4. Importantly, IgG4-AID differ significantly from diseases associated with IgG1 autoantibodies targeting the same organ. This may be due to the unique functional characteristics of IgG4 autoantibodies (e.g. anti-inflammatory and functionally monovalent) that affect how the antibodies cause disease, and the differential response to immunotherapies of the IgG4 producing B cells/plasmablasts. These clinical and pathophysiological clues give important insight in the immunopathogenesis of IgG4-AID. Understanding IgG4 immunobiology is a key step towards the development of novel, IgG4 specific treatments. In this review we therefore summarize current knowledge on IgG4 regulation, the relevance of class switching in the context of health and disease, describe the cellular mechanisms involved in IgG4 production and provide an overview of treatment responses in IgG4-AID.

IL-18 in inflammatory and autoimmune disease

Inflammation serves as the first line of defense in response to tissue injury, guiding the immune system to ensure preservation of the host. The inflammatory response can be divided into a quick initial phase mediated mainly by innate immune cells including neutrophils and macrophages, followed by a late phase that is dominated by lymphocytes. Early in the new millennium, a key component of the inflammatory reaction was discovered with the identification of a number of cytosolic sensor proteins (Nod-like receptors) that assembled into a common structure, the 'inflammasome'. This structure includes an enzyme, caspase-1, which upon activation cleaves pro-forms of cytokines leading to subsequent release of active IL-1 and IL-18. This review focuses on the role of IL-18 in inflammatory responses with emphasis on autoimmune diseases.

Current and emerging treatments for the management of myasthenia gravis

Myasthenia gravis is an autoimmune neuromuscular disorder. There are several treatment options, including symptomatic treatment (acetylcholinesterase inhibitors), short-term immunosuppression (corticosteroids), long-term immunosuppression (azathioprine, cyclosporine, cyclophosphamide, methotrexate, mycophenolate mofetil, rituximab, tacrolimus), rapid acting short-term immunomodulation (intravenous immunoglobulin, plasma exchange), and long-term immunomodulation (thymectomy). This review explores in detail these different treatment options. Potential future treatments are also discussed.

Interleukin-18: a pro-inflammatory cytokine that plays an important role in acute pancreatitis

A large body of clinical and experimental evidence suggests that cytokines play a key role in the pathogenesis of local and systemic complications of acute pancreatitis. IL-18 is a pro-inflammatory cytokine that plays a key role in many human diseases, including acute pancreatitis. This review focuses on the present understanding in IL-18 and its potential role in acute pancreatitis. IL-18 levels reflect the severity of acute pancreatitis and display a significant negative correlation with the concentrations of antioxidative damage factors, serum selenium and glutathione peroxidases (GPx). The relationship between IL-18 and other pro-inflammatory cytokines shows that IL-18 is one of the key mediators of inflammation in the pathogenesis of acute pancreatitis. Elevation of serum IL-18 levels may mediate acute pancreatitis associated liver injury. The use of IL-18 antagonists as direct routes to block IL-18 activity and P2X7 receptor antagonists and interleukin-1beta-converting enzyme (ICE) inhibitors as indirect routes to block IL-18 activity suggest that specific therapeutic inhibition of IL-18 is a promising therapeutic approach for acute pancreatitis.

Vaccines against myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disease mediated by antibodies to nicotinic acetylcholine receptor (AChR) interfering with the neuromuscular transmission. Experimental autoimmune MG serves as an excellent animal model to study possible therapeutic modalities for MG. This review will focus on the different ways to turn off the autoimmune response to AChR, which results in suppression of myasthenia. This paper will describe the use of fragments or peptides derived from the AChR, antigen-presenting cells and anti-T cell receptor antibodies, and will discuss the underlying mechanisms of action. Finally, the authors propose new promising therapeutic prospects, including treatment based on the modulation of regulatory T cells, which have recently been found to be functionally defective in MG patients.

Menstrual variation of autonomic balance may be a factor in exacerbations of certain diseases during the menstrual cycle

Exacerbation of certain medical conditions during specific phases of the menstrual cycle has long been recognized. Mechanisms of the cyclic variations are poorly understood, but are often attributed to fluctuations in reproductive hormones. We hypothesize that normal variations in autonomic balance during the menstrual cycle, which likely evolved as adaptations for reproduction, may contribute to catamenial variations in diseases independent of hormonal variations. Emerging evidence suggests that autonomic balance shifts towards sympathetic bias during the second half of the menstrual cycle. This shift can be seen as an evolutionary adaptation to address the immunologic and physiologic demands for successful implantation and gestation. Through direct modulation of lymphoid system and activation of the cortisol pathway, sympathetic bias promotes a shift to relative T helper (Th)-2-biased immunity which may favor maternal tolerance of the embryo by attenuating Th-1-mediated interference of implantation. Immune variance during the menstrual cycle has been implicated in menstrual fluctuations of many diseases, but until now the immune variance has been attributed to female hormonal changes. We propose that shifts in autonomic balance independently contribute to fluctuations in diseases by modulating the immune system. Still further, we propose that many other diseases fluctuate due to the direct nervous system actions of shifts in autonomic balance. Our hypothesis portends new therapeutic paradigms based on cyclical modulation of autonomic balance to address catamenial variations of medical conditions.