Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0014070 (encephalomyelitis)
 13,017 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Some autoreactive T cells normally escape thymic selection and persist in the periphery. This is true of myelin-reactive CD4(+) T cells, the effectors of experimental autoimmune encephalomyelitis (EAE) in laboratory animals and the presumed mediators of multiple sclerosis in humans. Nonetheless, most individuals do not succumb to autoimmune disease. There is growing evidence that while peripheral APCs stimulate immune responses against foreign Ags in the setting of tissue destruction and "danger," they actually maintain tolerance against self Ags under steady state conditions. We hypothesized that tolerance against candidate autoantigens could be reversed by activation of APCs via CD40 or Toll-like receptor 9 signaling. Adult SJL mice injected i.p. with a peptide fragment of proteolipid protein (a candidate autoantigen in multiple sclerosis) emulsified in IFA fail to mount lymphoproliferative or cytokine responses and are protected from EAE upon subsequent challenge with the Ag combined with adjuvants. Here we report that tolerized proteolipid protein-specific lymph node cells regain the ability to divide, differentiate along a Th1 lineage, and transfer EAE when reactivated in the presence of agonistic Abs against CD40 or CpG oligonucleotides. The effects of both anti-CD40 and CpG oligonucleotides are dependent upon induction of IL-12. Our findings suggest two mechanisms to explain the well-documented association between infectious illnesses and flare-ups of multiple sclerosis. Microbial pathogens could 1) release molecules that bind Toll-like receptors, and/or 2) stimulate microbe-specific T cells to express CD40 ligand, thereby licensing APCs that bear both microbial and autoantigens to break tolerance.
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PMID:Activation of APCs through CD40 or Toll-like receptor 9 overcomes tolerance and precipitates autoimmune disease. 1219 53

We describe the generation of mice that express a transgenic T cell receptor (TCR) (5B6) specific for the encephalitogenic myelin proteolipid protein (PLP) peptide 139-151, on the experimental autoimmune encephalomyelitis-resistant (EAE-resistant) B10.S background. Despite harboring a high frequency of self-reactive T cells, 5B6 transgenic mice on the B10.S background rarely develop spontaneous EAE, which is in striking contrast to 5B6 transgenic mice on the EAE-susceptible SJL background. The relative resistance to spontaneous EAE in transgenic B10.S mice is not due to deletion or anergy of T cells, but appears to be controlled by APCs. Analysis of APCs revealed a lower activation state and a lower T cell-activating capacity for APCs from B10.S mice than for those from EAE-susceptible SJL mice. When APCs in 5B6 transgenic B10.S mice were activated, for example, via TLR9 or TLR4, T cell tolerance was broken, resulting in EAE. Our findings demonstrate that activation of APCs via innate immune receptors can break self tolerance and trigger the development of autoimmunity even in a genetically resistant strain. These findings suggest that the development of autoimmune diseases such as multiple sclerosis is determined at least partly by the endogenous activation state of APCs.
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PMID:Activation of antigen-presenting cells by microbial products breaks self tolerance and induces autoimmune disease. 1505 5

The initial event in the pathogenesis of autoimmune disease is thought to be the priming of naive autoreactive T cells by an infection with a cross-reactive microorganism. Although such cross-reactive priming should be a common event, autoimmune disease does not frequently develop. This situation is reflected after the immunization of C57BL/6 mice with the neuroantigen myelin oligodendrocyte glycoprotein (MOG) with CFA, which primes a type 1 T cell response but does not lead to clinical or histological manifestation of experimental allergic encephalomyelitis unless pertussis toxin is injected in addition. We show in this study that, in MOG:CFA-primed mice, the autoimmune CNS pathology develops after intracerebral deposition of TLR9-activating CpG oligonucleotides, but not following non-CpG oligonucleotide injection or after aseptic cryoinjury of the brain. Thus, access of primed MOG-specific Th1 cells to the uninflamed CNS or to CNS undergoing sterile inflammation did not suffice to elicit autoimmune pathology; only if the APC in the target organ were activated in addition by the TLR9-stimulating microbial product did they exert local effector functions. The data suggest that such licensing of APC in the target organ by microbial stimuli represents a checkpoint for functional self-tolerance. Therefore, microorganisms unrelated to the cross-reactive agent that primes the autoreactive T cells could dictate the onset and exacerbation of autoimmune diseases.
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PMID:The third signal in T cell-mediated autoimmune disease? 1521 Jul 63

Microglia are the resident macrophage-like population in the CNS. Microglia remain quiescent until injury or infection activates the cells to perform effector inflammatory and APC functions. Our previous studies have shown that microglia infected with a neurotropic strain of Theiler's murine encephalomyelitis virus secreted innate immune cytokines and up-regulated costimulatory molecules and MHC class II, enabling the cells to present viral and myelin Ags to CD4+ T cells. Recently, TLRs have been shown to recognize pathogen-associated molecular patterns and initiate innate immune responses upon interaction with infectious agents. We examined TLR expression on brain microglia and their functional responses upon stimulation with various TLR agonists. We report that mouse microglia express mRNA for all of the recently identified TLRs, TLR1-9, used for recognition of bacterial and viral molecular patterns. Furthermore, stimulation of quiescent microglia with various TLR agonists, including LPS (TLR4), peptidoglycan (TLR2), polyinosinic-polycytidylic acid (TLR3), CpG DNA (TLR9), and infection with viable Theiler's murine encephalomyelitis virus, activated the cells to up-regulate unique patterns of innate and effector immune cytokines and chemokines at the mRNA and protein levels. In addition, TLR stimulation activated up-regulation of MHC class II and costimulatory molecules, enabling the microglia to efficiently present myelin Ags to CD4+ T cells. Thus, microglia appear to be a unique and important component of both the innate and adaptive immune response, providing the CNS with a means to rapidly and efficiently respond to a wide variety of pathogens.
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PMID:Microglia initiate central nervous system innate and adaptive immune responses through multiple TLRs. 1535 40

Innate immune mechanisms essential for priming encephalitogenic T cells in autoimmune neuroinflammation are poorly understood. Experimental autoimmune encephalomyelitis (EAE) is a IL-17-producing Th (Th17) cell-mediated autoimmune disease and an animal model of multiple sclerosis. To investigate how upstream TLR signals influence autoimmune T cell responses, we studied the role of individual TLR and MyD88, the common TLR adaptor molecule, in the initiation of innate and adaptive immune responses in EAE. Wild type (WT) C57BL/6, TLR-deficient and MyD88-deficient mice were immunized with myelin oligodendrocyte glycoprotein (MOG) in CFA. MyD88(-/-) mice were completely EAE resistant. Purified splenic myeloid DC (mDC) from MyD88(-/-) mice expressed much less IL-6 and IL-23, and serum and T cell IL-17 were absent. TLR4(-/-) and TLR9(-/-) mice surprisingly exhibited more severe EAE symptoms than WT mice. IL-6 and IL-23 expression by mDC and Th17 responses were higher in TLR4(-/-) mice, suggesting a regulatory role of TLR4 in priming Th17 cells. IL-6 expression by splenocytes was higher in TLR9(-/-) mice. Our data suggest that MyD88 mediates the induction of mDC IL-6 and IL-23 responses after MOG immunization, which in turn drives IL-17-producing encephalitogenic Th17 cell activation. Importantly, we demonstrate that TLR4 and TLR9 regulate disease severity in MOG-induced EAE.
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PMID:Unexpected regulatory roles of TLR4 and TLR9 in experimental autoimmune encephalomyelitis. 1820 39

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system, with disturbances of the immunological balance. As TLR9-null mice showed increased resistance to experimental autoimmune encephalomyelitis and recent genetic investigations showed that T-1237C promoter polymorphism of TLR9, commonly implicated in autoimmune diseases, induces a deregulation of its expression, we performed an association study in a Portuguese population of 165 MS patients and unrelated healthy controls. Our results show no significant association with MS and no protective effect of T-1237C concerning age of onset, disease severity or disease subtype in MS patients.
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PMID:T-1237C polymorphism of TLR9 gene is not associated with multiple sclerosis in the Portuguese population. 1820 76

Cathepsin K was originally identified as an osteoclast-specific lysosomal protease, the inhibitor of which has been considered might have therapeutic potential. We show that inhibition of cathepsin K could potently suppress autoimmune inflammation of the joints as well as osteoclastic bone resorption in autoimmune arthritis. Furthermore, cathepsin K-/- mice were resistant to experimental autoimmune encephalomyelitis. Pharmacological inhibition or targeted disruption of cathepsin K resulted in defective Toll-like receptor 9 signaling in dendritic cells in response to unmethylated CpG DNA, which in turn led to attenuated induction of T helper 17 cells, without affecting the antigen-presenting ability of dendritic cells. These results suggest that cathepsin K plays an important role in the immune system and may serve as a valid therapeutic target in autoimmune diseases.
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PMID:Cathepsin K-dependent toll-like receptor 9 signaling revealed in experimental arthritis. 1823 12

Experimental autoimmune encephalomyelitis (EAE) is a Th17-mediated autoimmune disease and an animal model for multiple sclerosis (MS). Complete Freund's adjuvant (CFA) contains pathogen-associated molecular patterns (PAMPs) that bind toll-like receptors (TLRs), and is necessary to induce EAE. Upstream TLR signals modify innate and adaptive immune responses in EAE. In detail, the common TLR adaptor molecule MyD88 is necessary for induction of EAE, and mediates activation of peripheral myeloid dendritic cells (mDCs) and differentiation of autoimmune Th17 cells. The stimulatory TLRs have not yet been identified for Th17 cells. TLR4 down regulates disease severity in EAE and Th17 cell responses, but promotes Th1 cell responses, which may inhibit the differentiation of Th17 cells. Moreover, treatment with a TLR4 ligand tolerizes mice and prevents EAE. TLR9 down regulates disease severity in myelin oligodendrocyte glycoprotein (MOG)-induced EAE, whereas it promotes disease in MOG(35-55)-induced EAE. Thus MyD88, TLR4 and TLR9 modify the disease process in EAE. Both endogenous and CFA-derived TLR ligands are implicated to modulate the disease process.
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PMID:Regulation of autoimmune encephalomyelitis by toll-like receptors. 1921 Oct 42

Certain pathogen molecules trigger innate immune responses and drive subsequent adaptive immune responses toward an antigen presented simultaneously. Such bacterial or viral molecules constitute pathogen-associated molecular patterns (PAMPs) that bind to pattern-recognition receptors such as toll-like receptors (TLRs). Recently, endogenous molecules were identified that ligate the same receptors. The role of these receptors' response to complete Freund's adjuvant during initiation of CD4 T cell responses in EAE, the animal model for multiple sclerosis, is here discussed. Myeloid differentiation primary response gene 88 (MyD88) is necessary for the induction of experimental autoimmune encephalomyelitis (EAE), and it is required for the activation of myeloid dendritic cells and differentiation of T helper 17 cells. The role of individual TLR, in particular TLR3, TLR4, and TLR9, signaling in modulation of EAE inflammation varies with the experimental model employed and the immune cells that drive pathology. The TLR-dependent production of proinflammatory cytokines is regulated by mechanisms that dampen the pathway and prevent excess damage. Development of TLR antagonists to treat autoimmune diseases must acknowledge the possibility of interference with regulatory mechanisms.
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PMID:Toll-like receptors in multiple sclerosis mouse experimental models. 1975 86

The potential roles of TLRs in the cause and pathogenesis of autoimmune CNS inflammation remain contentious. In this study, we examined the effects of targeted deletions of TLR1, TLR2, TLR4, TLR6, TLR9, and MyD88 on the induction of myelin oligodendrocyte glycoprotein 35-55 (MOG(35-55)) peptide/CFA/pertussis toxin-induced autoimmune encephalomyelitis. Although C57BL/6.Tlr1(-/-), C57BL/6.Tlr4(-/-) and C57BL/6.Tlr6(-/-) mice showed normal susceptibility to disease, signs were alleviated in female C57BL/6.Tlr2(-/-) and C57BL/6.Tlr9(-/-) mice and C57BL/6.Tlr2/9(-/-) mice of both sexes. C57BL/6.Myd88(-/-) mice were completely protected. Lower clinical scores were associated with reduced leukocyte infiltrates. These results were confirmed by passive adoptive transfer of disease into female C57BL/6.Tlr2(-/-) and C57BL/6.Tlr9(-/-) mice, where protection in the absence of TLR2 was associated with fewer infiltrating CD4(+) cells in the CNS, reduced prevalence of detectable circulating IL-6, and increased proportions of central (CD62L(+)) CD4(+)CD25(+)Foxp3(+) regulatory T cells. These results provide a potential molecular mechanism for the observed effects of TLR signaling on the severity of autoimmune CNS inflammation.
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PMID:Role for MyD88, TLR2 and TLR9 but not TLR1, TLR4 or TLR6 in experimental autoimmune encephalomyelitis. 2168 27


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