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ABSTRACT: Myasthenia gravis (MG) is an antibody mediated, T cell dependent autoimmune disease characterized by muscle fatigability in which autoantibodies directed to the acetylcholine receptor (AChR) impair neuromuscular transmission. The identification of CD4(+)CD25(+)Foxp3(+) Treg cells as important regulators of tolerance opened a major area of investigation raising the possibility that a dysfunction in the Treg compartment is involved in the etiology and pathogenesis of autoimmune diseases, including MG. In this paper we summarize shortly Treg abnormalities that were reported in MG patients and report on our studies of Treg in experimental autoimmune MG (MG). Hopefully these studies would pave the way towards the development of novel Treg-based treatment modalities that will restore self-tolerance in MG and other autoimmune diseases. In our previous studies in EAMG we have shown that Treg cells transferred from healthy rat donors to myasthenic rats suppress EAMG. However, Treg cells from sick animals do not have the same in vivo suppressive activity as those from healthy donors. The objective of the present study was to further characterize quantitative and qualitative alterations in Treg cells of rats with EAMG. We found that the frequency of CD4(+)CD25(+)Foxp3(+) Treg cells within the spleen and PBL was decreased in EAMG rats as compared to naïve and CFA-immunized healthy controls. Treg cells from myasthenic rats were less effective than Treg cells from controls in suppressing the proliferation of CD4(+) T effector cells in response to ConA and of B cells in response to LPS. Moreover, CD4(+)CD25(+) cells from EAMG rats exhibited an elevated extent of apoptosis and expressed upregulated levels of FAS and of Th17-associated cytokines. Since EAMG is an induced disease, these quantitative and qualitative alterations in Treg cells do not reflect predisposing impairments and seem to be associated with the specific autoimmune response resulting from AChR immunization.
Autoimmunity reviews 03/2013; · 6.37 Impact Factor
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ABSTRACT: Aire (autoimmune regulator) has a key role in the establishment of tolerance to autoantigens. Aire(-/-) mice present decreased thymic expression of AChR, significantly lower frequencies of regulatory T (T(reg) ) cells, and higher expression of Th17 markers, compared to controls. We therefore predicted that Aire(-/-) mice would be more susceptible to induction of experimental autoimmune myasthenia gravis (EAMG). However, when EAMG was induced in young mice, Aire(-/-) mice presented a milder disease that wild-type (WT) controls. In contrast, when EAMG was induced in older mice, Aire(-/-) mice were more severely affected than WT mice. The relative resistance to EAMG in young Aire(-/-) mice correlated with increased numbers of T(reg) cells in their spleens compared to young controls. A similar age-related susceptibility was also observed when EAE was induced in Aire(-/-) mice, suggesting an age-related link among Aire, disease susceptibility, and peripheral T(reg) cells that may be a general feature of autoimmunity.
Annals of the New York Academy of Sciences 12/2012; 1275(1):107-13. · 3.15 Impact Factor
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ABSTRACT: Establishment of tolerance in myasthenia gravis (MG) involves regulatory T (T(reg) ) cells. Experimental autoimmune MG (EAMG) in rats is a suitable model for assessing the contribution of T(reg) cells to the immunopathology of the disease and for testing novel T(reg) cell-based treatment modalities. We have studied two immunotherapeutic approaches for targeting of T(reg) cells in myasthenia. By one approach we demonstrated that treatment of sick rats by ex vivo-generated exogenous T(reg) cells derived from healthy donors suppressed EAMG. By a different approach, we aimed at affecting the endogenous T(reg) /Th17 cell balance by targeting IL-6, which has a key role in controlling the equilibrium between pathogenic Th17 and suppressive T(reg) cells. We found that treatment of myasthenic rats by neutralizing anti-IL-6 antibodies shifted this equilibrium in favor of T(reg) cells and led to suppression of EAMG. Our results show that T(reg) cells could serve as potential targets in treating MG patients.
Annals of the New York Academy of Sciences 12/2012; 1274(1):120-6. · 3.15 Impact Factor
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ABSTRACT: Suppressive regulatory T cells (Treg) and pathogenic T helper 17 (Th17) cells are two lymphocyte subsets with opposing activities in autoimmune diseases. The proinflammatory cytokine IL-6 is a potent factor in switching immune responses in vivo from the induction of Treg to pathogenic Th17 cells. We studied the Treg and Th17 cell compartments in experimental autoimmune myasthenia gravis (EAMG) and healthy control rats in order to assess whether the equilibrium between Treg and Th17 cells is perturbed in the disease. We found that Th17 cell-related genes are upregulated and Treg-related genes are downregulated in EAMG. The shift in favor of Th17 cells in EAMG could be reversed by antibodies to IL-6. Administration of anti-IL-6 antibodies to myasthenic rats suppressed EAMG when treatment started at the acute or at the chronic phase of disease. Suppression of EAMG by anti-IL-6 antibodies was accompanied by a decrease in the overall rat anti-AChR antibody titer and by a reduced number of B cells as compared with control treatment. Administration of anti-IL-6 antibodies led to down-regulation of several Th17 related genes including IL-17, IL-17R, IL-23R and IL-21 but did not affect the number of Treg cells in the lymph nodes. These data identify IL-6 as an important target for modulation of autoimmune responses.
Journal of Autoimmunity 12/2010; 36(2):135-41. · 7.37 Impact Factor
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ABSTRACT: The autoimmune regulator (Aire) is involved in the prevention of autoimmunity by promoting thymic expression of tissue restricted antigens which leads to elimination of self-reactive T cells. We found that Aire knockout (KO) mice as well as mouse strains that are susceptible to experimental autoimmune myasthenia gravis (EAMG) have lower thymic expression of acetylcholine receptor (AChR- the main autoantigen in MG), compared to wild type (WT) mice and EAMG-resistant mouse strains, respectively. We demonstrated that Aire KO mice have a significant and reproducible lower frequency of CD4+Foxp3+ cells and a higher expression of Th17 markers in their thymus, compared to wild type (WT) mice. These findings led us to expect that Aire KO mice would display increased susceptibility to EAMG. Surprisingly, when EAMG was induced in young (2 month-old) mice, EAMG was milder in Aire KO than in WT mice for several weeks until the age of about 5 months. However, when EAMG was induced in relatively aged (6 month-old) mice, Aire KO mice presented higher disease severity than WT controls. This age-related change in susceptibility to EAMG correlated with an elevated proportion of Treg cells in the spleens of young but not old KO, compared to WT mice, suggesting a role for peripheral Treg cells in the course of disease. Our observations point to a possible link between Aire and Treg cells and suggest an involvement for both in the pathogenesis of myasthenia.
Journal of Autoimmunity 10/2010; 36(1):16-24. · 7.37 Impact Factor
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Keren Mizrachi,
Revital Aricha,
Tali Feferman,
Neta Kela-Madar,
Ilana Mandel,
Tamar Paperna,
Ariel Miller,
Avraham Ben-Nun,
Sonia Berrih-Aknin,
Miriam C Souroujon, Sara Fuchs
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ABSTRACT: We have previously shown that several phosphodiesterase (PDE) subtypes are up-regulated in muscles and lymph node cells (LNC) of rats with experimental autoimmune myasthenia gravis (EAMG). In the present study we investigated PDE expression during the course of EAMG and experimental allergic encephalomyelitis (EAE) and found that the up-regulated expression of selected PDE subtypes in both experimental models is correlated with disease severity. In EAMG, PDE expression is correlated also with muscle damage. A similar up-regulation of PDE was also observed in the respective human diseases, MG and multiple sclerosis (MS). Our findings suggest that change in PDE expression levels is a general phenomenon in autoimmune diseases and may also be used as a marker for disease severity.
Journal of neuroimmunology 03/2010; 220(1-2):43-51. · 2.84 Impact Factor
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ABSTRACT: We have previously demonstrated that the chemokine IFN-gamma inducible protein 10 (IP-10) and its receptor CXCR3, are overexpressed in myasthenia gravis (MG) and its animal model experimental autoimmune MG (EAMG). We now studied the potential of modulating rat EAMG by interference in CXCR3/IP-10 signaling. Two different approaches were used: 1) blocking IP-10 by IP-10-specific antibodies and 2) inhibiting the CXCR3 chemokine receptor by a CXCR3 antagonist. Treatment by either of these reagents led to suppression of EAMG suggesting that inhibition of CXCR3/IP-10 signaling can be considered as a potential treatment modality for MG.
Journal of neuroimmunology 03/2009; 209(1-2):87-95. · 2.84 Impact Factor
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ABSTRACT: Myasthenia gravis (MG) and experimental autoimmune MG (EAMG) are antibody-mediated autoimmune diseases in which the nicotinic acetylcholine receptor (AChR) is the major autoantigen. Previously we have revealed that oral treatment with the less native recombinant fragment of the extracellular domain of the human AChR (Halpha1-205) suppressed ongoing EAMG, whereas the more native recombinant Trx-Halpha1-210 exacerbated EAMG. In this study, we speculated on the role of B-cell epitopes in oral tolerogens for the induction of oral tolerance in EAMG. We developed a B-cell epitope-free AChR fragment (BF-AChR) by removing two major B-cell epitopes (67-76 and 129-145) from Trx-Halpha1-210. BF-AChR exhibited a poor response to EAMG sera and to AChR-specific B- and T-cells while its parent fragment, Trx-Halpha1-210, showed much higher reactivity. Oral administration of BF-AChR ameliorated the symptoms in ongoing myasthenic rats accompanied by a significant decrease in AChR-specific humoral and Th1 cellular responses. The underlying mechanism for BF-AChR-induced oral tolerance was mediated by a shift from Th1 to regulatory T-cell (IL-10(+), CD4(+) TGF-beta(+) or Foxp3(+)) responses. This shift was assessed by changes in the cytokine profile and a deviation in the anti-AChR IgG isotypes from IgG2a/IgG2b to IgG1. Our results suggest that the removal of pathogenic B-cell epitopes from AChR fragments increases tolerogenicity by reducing the activation and proliferation of autoreactive B- and T-cells. Collectively, careful consideration of the immunogenicity of a tolerogen is necessary to induce successful oral tolerance in autoimmune disorders.
Molecular Immunology 10/2008; 46(1):192-201. · 2.90 Impact Factor
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ABSTRACT: Myasthenia gravis (MG) is frequently treated by corticosteroids such as methylprednisolone. However, continuous treatment with steroids often results in adverse effects. In the present study we evaluated the therapeutic potential of a combination of suboptimal doses of methylprednisolone (Solumedrol) and Pentoxifylline (PTX), a general phosphodiesterase (PDE) inhibitor, in rat experimental autoimmune MG (EAMG). This combined treatment resulted in a pronounced suppressive effect on EAMG and was by far more effective than each of the drugs administered separately at these low doses. The suppressive effect on EAMG was accompanied by decreased humoral and cellular responses to AChR as well as down-regulated mRNA expression levels of Th1 cytokines and IL-10 in lymph node cells and of PDE-4 and cathepsin-l in the muscle. This study demonstrates the potential of PTX as a steroid-sparing agent in the management of myasthenia gravis.
Journal of Neuroimmunology 09/2008; 201-202:128-35. · 2.96 Impact Factor
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ABSTRACT: Intravenous immunoglobulin (IVIG) administration has been beneficially used for the treatment of a variety of autoimmune diseases including myasthenia gravis (MG). We have demonstrated that IVIG administration in experimental autoimmune MG (EAMG) results in suppression of disease that is accompanied by decreased Th1 cell and B cell proliferation. Chromatography of pooled human immunoglobulins (IVIG) on immobilized IgG, isolated from rats with EAMG or from MG patients, results in a depletion of the suppressive activity of the IVIG. Moreover, reconstitution of the activity-depleted IVIG with the eluted minute IVIG fractions that had been adsorbed onto the EAMG- or MG-specific columns recovers the depleted immunosuppressive activity. This study supports the notion that the therapeutic effect of IVIG is mediated by an antigen-specific anti-immunoglobulin (anti-idiotypic) activity that is essential for its suppressive activity.
Annals of the New York Academy of Sciences 07/2008; 1132:244-8. · 3.15 Impact Factor
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ABSTRACT: Naturally occurring CD4(+)CD25(+) regulatory T (Treg) cells are key players in immune tolerance and have therefore been suggested as potential therapeutic tools for autoimmune diseases. In myasthenia gravis (MG), reduced numbers or functionally impaired Treg cells have been reported. We have observed that PBL from myasthenic rats contain decreased numbers of CD4(+)CD25(high)Foxp3(+) cells as compared with PBL from healthy controls, and we have tested whether Treg cells from healthy donors can suppress experimental autoimmune MG in rats. Because the number of naturally occurring Treg cells is low, we used an approach for a large-scale ex vivo generation of functional Treg cells from CD4(+) splenocytes of healthy donor rats. Treg cells were generated ex vivo from CD4(+) cells by stimulation with anti-CD3 and anti-CD28 Abs in the presence of TGF-beta and IL-2. The obtained cells expressed high levels of CD25, CTLA-4, and Foxp3, and they were capable of suppressing in vitro proliferation of T cells from myasthenic rats in response to acetylcholine receptor, the major autoantigen in myasthenia. Administration of ex vivo-generated Treg cells to myasthenic rats inhibited the progression of experimental autoimmune MG and led to down-regulation of humoral acetylcholine receptor-specific responses, and to decreased IL-18 and IL-10 expression. The number of CD4(+)CD25(+) cells in the spleen of treated rats remained unchanged, but the subpopulation of CD4(+)CD25(+) cells expressing Foxp3 was significantly elevated. Our findings imply that Treg cells play a critical role in the control of myasthenia and could thus be considered as potential agents for the treatment of MG patients.
The Journal of Immunology 03/2008; 180(4):2132-9. · 5.79 Impact Factor
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ABSTRACT: Intravenous immunoglobulin (IVIG) treatment is beneficially used in autoimmune disorders including myasthenia gravis (MG) although its mode of action and active components are still not fully identified. In an attempt to isolate from IVIG a disease-specific suppressive fraction, IVIG was passed on columns of IgG from rats with experimental autoimmune MG (EAMG) or from MG patients. These chromatographies resulted in depletion of the suppressive activity of IVIG on rat EAMG whereas the minute amounts of IgG fractions eluted from the EAMG- or MG-specific columns retained the immunosuppressive activity of IVIG. These results demonstrate that a minor disease-specific immunoglobulin fraction present in IVIG is essential for its suppressive activity.
Journal of Neuroimmunology 03/2008; 194(1-2):89-96. · 2.96 Impact Factor
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ABSTRACT: [corrected] Intravenous immunoglobulin administration has been beneficially used for the treatment of a variety of autoimmune diseases including myasthenia gravis, although its mode of action and active components have not yet been fully identified.
To isolate from IVIg a disease-specific fraction involved in the therapeutic activity in myasthenia and to identify its properties and function.
IVIg administration in experimental autoimmune MG results in suppression of disease that is accompanied by decreased Th1 cell and B cell proliferation. Chromatography of IVIg on columns of IgG from rats with EAMG or from MG patients resulted in depletion of the suppressive activity that IVIg has on rat EAMG. Moreover, the minute amounts of IgG fractions eluted from the EAMG or MG-specific columns retained the immunosuppressive activity of IVIg.
Our study supports the notion that the therapeutic effect of IVIg is mediated by a minor disease-specific immunoglobulin fraction that is present in IVIg and is essential for its therapeutic activity.
The Israel Medical Association journal: IMAJ 02/2008; 10(1):58-60. · 1.02 Impact Factor
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ABSTRACT: Intravenous immunoglobulin (IVIG) administration has been beneficially used for the treatment of a variety of autoimmune diseases including myasthenia gravis (MG). We have demonstrated that IVIG administration in experimental autoimmune MG (EAMG) results in suppression of disease that is accompanied by decreased Th1 cell and B cell proliferation. Chromatography of pooled human immunoglobulins (IVIGs) on immobilized IgG, isolated from rats with EAMG, results in a complete depletion of the suppressive activity of the IVIG. Moreover, the eluate from this EAMG-specific antibody column retains the immunosuppressive activity of IVIG. This study supports the notion that the therapeutic effect of IVIGs is mediated by an antigen-specific anti-immunoglobulin (anti-idiotypic) activity that is essential for its suppressive activity.
Annals of the New York Academy of Sciences 09/2007; 1110(1):550 - 558. · 3.15 Impact Factor
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ABSTRACT: DNA microarray technology was used to identify new potential drug targets for myasthenia gravis (MG), to delineate genes involved in the pathogenesis of the disease and to possibly target their protein products for immunotherapy. In this study we compared the gene expression in lymph node cells (LNC) and muscles of rats with experimental autoimmune MG (EAMG) to those of control, healthy rats. Of the genes that were found to be deregulated in EAMG, we chose to elaborate on two gene systems: (a) The chemokine IFN-gamma-inducible protein 10 (IP-10, CXCL10), and its receptor (CXCR3) and (b) phosphodiesterases.
Annals of the New York Academy of Sciences 07/2007; 1107:111-7. · 3.15 Impact Factor
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Annals of the New York Academy of Sciences 12/2006; 505(1):256 - 271. · 3.15 Impact Factor
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Annals of the New York Academy of Sciences 12/2006; 505(1):676 - 682. · 3.15 Impact Factor
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Annals of the New York Academy of Sciences 12/2006; 681(1):126 - 139. · 3.15 Impact Factor
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Annals of the New York Academy of Sciences 12/2006; 475(1):81 - 93. · 3.15 Impact Factor
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ABSTRACT: Intravenous immunoglobulin (IVIG) administration has been beneficially used in the treatment of several autoimmune disorders including myasthenia gravis (MG), although its mechanism of action is still not clear. To study the optimal conditions of IVIG treatment and delineate its mechanism of action we established a suitable model in rat experimental autoimmune MG (EAMG). We show that IVIG has a suppressive effect on the clinical symptoms of ongoing EAMG that is associated with decreased AChR-specific cellular and humoral immune reactivity. Costimulatory factors and cytokine profile analyses suggest that IVIG immunomodulation in EAMG involves suppression of B and Th1-type T cell responses with no generation of T-regulatory cells. Our data contribute to the understanding of the immunological mechanisms underlying IVIG treatment in MG and in other autoimmune disorders.
Journal of Neuroimmunology 08/2006; 176(1-2):187-97. · 2.96 Impact Factor
