Comparing the pathogenesis of experimental autoimmune encephalomyelitis in CD4-/- and CD8-/- DBA/1 mice defines qualitative roles of different T cell subsets

CC Chemokine Receptor 4 (CCR4) as a Possible New Target for Therapy

Chemokines and their receptors participate in many biological processes, including the modulation of neuroimmune interactions. Approximately fifty chemokines are distinguished in humans, which are classified into four subfamilies based on the N-terminal conserved cysteine motifs: CXC, CC, C, and CX3C. Chemokines activate specific receptors localized on the surface of various immune and nervous cells. Approximately twenty chemokine receptors have been identified, and each of these receptors is a seven-transmembrane G-protein coupled receptor. Recent studies provide new evidence that CC chemokine receptor 4 (CCR4) is important in the pathogenesis of many diseases, such as diabetes, multiple sclerosis, asthma, dermatitis, and cancer. This review briefly characterizes CCR4 and its ligands (CCL17, CCL22, and CCL2), and their contributions to immunological and neoplastic diseases. The review notes a significant role of CCR4 in nociceptive transmission, especially in painful neuropathy, which accompanies many diseases. The pharmacological blockade of CCR4 seems beneficial because of its pain-relieving effects and its influence on opioid efficacy. The possibilities of using the CCL2/CCL17/CCL22/CCR4 axis as a target in new therapies for many diseases are also discussed.

Regulation of B cell functions by S-nitrosoglutathione in the EAE model

B cells play both protective and pathogenic roles in T cell-mediated autoimmune diseases by releasing regulatory vs. pathogenic cytokines. B cell-depleting therapy has been attempted in various autoimmune diseases but its efficacy varies and can even worsen symptoms due to depletion of B cells releasing regulatory cytokines along with B cells releasing pathogenic cytokines. Here, we report that S-nitrosoglutathione (GSNO) and GSNO-reductase (GSNOR) inhibitor N6022 drive upregulation of regulatory cytokine (IL-10) and downregulation of pathogenic effector cytokine (IL-6) in B cells and protected against the neuroinflammatory disease of experimental autoimmune encephalomyelitis (EAE). In human and mouse B cells, the GSNO/N6022-mediated regulation of IL-10 vs. IL-6 was not limited to regulatory B cells but also to a broad range of B cell subsets and antibody-secreting cells. Adoptive transfer of B cells from N6022 treated EAE mice or EAE mice deficient in the GSNOR gene also regulated T cell balance (Treg > Th17) and reduced clinical disease in the recipient EAE mice. The data presented here provide evidence of the role of GSNO in shifting B cell immune balance (IL-10 > IL-6) and the preclinical relevance of N6022, a first-in-class drug targeting GSNOR with proven human safety, as therapeutics for autoimmune disorders including multiple sclerosis.

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GSNO and GSNOR inhibitor (N6022) upregulates IL-10 and downregulates IL-6 in B cells.

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GSNO/N6022-mediated cytokine regulation occurs in a broad range of B cell subsets.

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GSNO/N6022 treatment ameliorates autoimmune disease of EAE.

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B cell transfer from N6022-treated or GSNOR null EAE mice to EAE mice shifts T cell balance (Treg > Th17) and alleviates EAE.

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The data provide the first insight into the therapeutic potential of GSNO/N6022 targeting B cells in multiple sclerosis.

CD8+ T Lymphocytes: Crucial Players in Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease associated with damage to multiple organs and glands. The most common clinical manifestations are dry eyes, dry mouth, and enlarged salivary glands. Currently, CD4+ T lymphocytes are considered to be key factors in the immunopathogenesis of pSS, but various studies have shown that CD8+ T lymphocytes contribute to acinar injury in the exocrine glands. Therefore, in this review, we discussed the classification and features of CD8+ T lymphocytes, specifically describing the role of CD8+ T lymphocytes in disease pathophysiology. Furthermore, we presented treatment strategies targeting CD8+ T cells to capitalize on the pathogenic and regulatory potential of CD8+ T lymphocytes in SS to provide promising new strategies for this inflammatory disease.

A new lipophilic amino alcohol, chemically similar to compound FTY720, attenuates the pathogenesis of experimental autoimmune encephalomyelitis by PI3K/Akt pathway inhibition

Experimental autoimmune encephalomyelitis (EAE) is one of the main animal models used for the study of Multiple Sclerosis (MS). Long-chain lipophilic amino alcohols with immunoregulatory activities have already been studied in some models of inflammatory diseases, but the action of these compounds in EAE and MS is still unknown. In this study, we investigated whether the lipophilic amino alcohol 4b would act to improve the clinical signs of EAE and reduce the demyelination process and the neuroinflammatory parameters in the spinal cord, as well as the inflammatory process in the inguinal lymph nodes, of C57Bl/6 mice induced with EAE after stimulation with MOG_35-55 and pertussis toxin. The 4b treatment (1.0 mg/kg/day) was orally administered, starting on the day of onset of clinical signs of the disease (10th) and ending on the 20th day after immunization. This treatment was able to reduce the cell count on the inguinal lymph nodes, the migration of inflammatory cells into the central nervous system (CNS), as well as the processes of microgliosis, astrogliosis, and the production of chemokines and pro-inflammatory cytokines, thus increasing the IL-10 anti-inflammatory cytokine levels in EAE mice. The inhibition of Akt phosphorylation in the CNS of EAE mice after treatment with 4b indicates that the immunoregulatory action of 4b is related to the PI3K/Akt signaling pathway. Our results indicate the immunoregulatory efficacy of the new compound 4b in the control of some inflammatory parameters and in the glial proliferation. In addition, 4b was able to reduce the demyelination of neurons and the worsening of clinical signs of EAE as effectively as the compound FTY720, the first oral drug approved by the FDA for the treatment of MS.

Neurons promote encephalitogenic CD4+ lymphocyte infiltration in experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system characterized by neuroinflammation, leading to demyelination and axonal degeneration. Neuronal excitotoxity mediated by Ca²⁺/calmodulin-dependent protein kinase IIα (CaMKIIα) results in neuronal damage in experimental autoimmune encephalitis (EAE), an animal model of MS. Here, we define a critical role of excitatory neurons in the pathogenesis of CD4⁺ lymphocyte accumulation in EAE. We silenced the activity of excitatory neurons in a mouse model of targeted EAE using inhibitory designer receptors exclusively activated by designer drugs (DREADD) under a CaMKIIα promoter. Neuronal silencing mitigated clinical disease scores in EAE, reduced the expression of c-fos, Tnfα, Ccl2, and Ccr2 mRNAs in targeted EAE lesions, and prevented the migration of CD4⁺ lymphocytes towards neurons. Ccl2 shRNA treatment of targeted EAE suppressed the migration of CD4⁺ lymphocytes and alleviated the motor deficits of EAE. Our findings indicate that neuronal activation in EAE promotes the migration of CCR2⁺ CD4⁺ lymphocytes and that neuronal silencing with an inhibitory DREADD alleviates clinical and molecular markers of disease. Neuronal CCL2 is thought to be involved in promoting lymphocytes migration.

Tuftsin Combines With Remyelinating Therapy and Improves Outcomes in Models of CNS Demyelinating Disease

Though promoting remyelination in multiple sclerosis (MS) has emerged as a promising therapeutic strategy, it does not address inflammatory signals that continue to induce neuronal damage and inhibit effectiveness of repair mechanisms. Our lab has previously characterized the immunomodulatory tetrapeptide, tuftsin, which induces an anti-inflammatory shift in microglia and macrophages. This targeted anti-inflammatory agent improves physical deficits in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Here, we sought to determine whether tuftsin is also effective in combination with benztropine, an FDA-approved drug that stimulates remyelination, in both EAE and in the cuprizone model of demyelination. We show that combining these two agents to promote anti-inflammatory and remyelinating mechanisms alleviates symptoms in EAE and lessens pathological hallmarks in both MS models. Importantly, tuftsin is required to transform the inflammatory CNS environment normally present in EAE/MS into one of an anti-inflammatory nature, and benztropine is required in the cuprizone model to improve remyelination. Our data further support tuftsin's beneficial immunomodulatory activity in the context of EAE, and show that when studying remyelination in the absence of an autoimmune insult, tuftsin still activated microglia toward an anti-inflammatory fate, but benztropine was necessary for significant repair of the damaged myelin. Overall, tuftsin effectively combined with benztropine to significantly improve MS-like pathologies in both models.

Combined Treatment with Methylprednisolone and Human Bone Marrow-Derived Mesenchymal Stem Cells Ameliorate Experimental Autoimmune Encephalomyelitis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. Although advances have been made in the treatment of MS, such as the use of IFN-β, glucocorticoids and stem cells, the therapeutic effects of these treatments are not sufficient. In the present study, we evaluated whether the combination of methylprednisolone (MP) and human bone marrow-derived mesenchymal stem cells (BM-MSCs) could enhance the therapeutic effectiveness in experimental autoimmune encephalomyelitis (EAE), a model for MS. EAE was induced by immunizing C57BL/6 mice with myelin oligodendrocyte glycoprotein 35-55 (MOG 35-55). The immunized mice received an intraperitoneal injection of MP (20 mg/kg), an intravenous injection of BM-MSCs (1 × 10⁶ cells) or both on day 14 after immunization. Combination treatment significantly ameliorated the clinical symptoms, along with attenuating inflammatory infiltration and demyelination, compared to either treatment alone. Secretion of pro-inflammatory cytokines (IFN-γ, TNF-α, IL-17) was significantly reduced, and anti-inflammatory cytokines (IL-4, IL-10) was significantly increased by the combination treatment as compared to either treatment alone. Flow cytometry analysis of MOG-reactivated T cells in spleen showed that combination treatment reduced the number of CD4⁺CD45⁺ and CD8⁺ T cells, and increased the number of CD4⁺CD25⁺Foxp3⁺ regulatory T cells. Furthermore, combination treatment enhanced apoptosis in MOG-reactivated CD4⁺ T cells, a key cellular subset in MS pathogenesis. Combination treatment with MP and BM-MSCs provides a novel treatment protocol for enhancing therapeutic effects in MS.

Interferon-β regulates dendritic cell activation and migration in experimental autoimmune encephalomyelitis

CD11c⁺ dendritic cells (DCs) exert a critical role as antigen-presenting cells in regulating pathogenic T cells in multiple sclerosis (MS). To determine whether the therapeutic benefit of interferon-β (IFN-β) treatment for MS is in part influenced by IFN regulation of DC function, we examined the immunophenotype of DCs derived from IFN-β^+/+ and IFN-β^-/- mice using a myelin oligodendrocyte glycoprotein (MOG) peptide-induced mouse model of MS, experimental autoimmune encephalomyelitis (EAE). Our earlier work identified that IFN-β^-/- mice exhibit earlier onset and more rapid progression of neurological impairment compared with IFN-β^+/+ mice. In this study we show that lipopolysaccharide-/MOG peptide-stimulated IFN-β^-/- DCs secrete cytokines associated with pathological T helper type 17 rather than regulatory T-cell polarization and exhibit increased CD80 and MHCII expression when compared with stimulated IFN-β^+/+ DCs. IFN-β^-/- DCs from mice immunized to develop EAE induce greater proliferation of MOG-transgenic CD4⁺ T cells and promote interleukin-17 production by these T cells. Adoptive transfer of MOG peptide-primed IFN-β^-/- DCs into IFN-β^+/+ and IFN-β^-/- mice immunized to develop EAE resulted in their rapid migration into the central nervous system of recipient mice, before onset of disease, which we attribute to failed signal transducer and activator of transcription 1-mediated inhibition of CCR7. Taken together, our data support immunoregulatory roles for IFN-β in the activation and migration of DCs during EAE.

CD8 T cells contribute to lacrimal gland pathology in the nonobese diabetic mouse model of Sjögren syndrome

Sjögren syndrome is an autoimmune disease characterized by targeted destruction of the lacrimal and salivary glands resulting in symptoms of severe ocular and oral dryness. Despite its prevalence, the mechanisms driving autoimmune manifestations are unclear. In patients and in the nonobese diabetic (NOD) mouse model of Sjögren syndrome, lymphocytic infiltrates consist of CD4 and CD8 T cells, although the role of CD8 T cells in disease pathogenesis has been largely unexplored. Here, we evaluated the contribution of CD8 T cells to lacrimal and salivary gland autoimmunity. Within the lacrimal and salivary glands of NOD mice, CD8 T cells were proliferating, expressed an activated phenotype, and produced inflammatory cytokines. Transfer of purified CD8 T cells isolated from the cervical lymph nodes (LNs) of NOD mice into NOD-severe combined immunodeficiency recipients resulted in inflammation of the lacrimal glands, but was not sufficient to cause inflammation of the salivary glands. Lacrimal gland-infiltrating CD8 T cells displayed a cytotoxic phenotype, and epithelial cell damage in the lacrimal glands was observed in recipients of CD8 T cells regardless of the presence of CD4 T cells. Collectively, our results demonstrate that CD8 T cells have a pathogenic role in lacrimal gland autoimmunity. The gland-specific pathogenicity of CD8 T cells makes them a valuable resource to further understand the mechanisms that discriminate lacrimal versus salivary gland autoimmunity and for the development of new therapeutics that target the early stages of disease.

BAFF-secreting neutrophils drive plasma cell responses during emergency granulopoiesis

Harris and collaborators show that neutropenia results in increased formation of plasma cells and elevated antibody production.

Prolonged infections or adjuvant usage can trigger emergency granulopoiesis (EG), leading to dysregulation in neutrophil blood counts. However, the impact of EG on T and B cell function remains largely unknown. In this study, to address this question, we used a mouse model of neutropenia and studied immune activation after adjuvant administration. The initial neutropenic state fostered an environment of increased dendritic cell activation and T cell–derived IL-17 production. Interestingly, neutropenic lysozyme 2–diphtheria toxin A mice exhibited striking EG and amplified neutrophil recruitment to the lymph nodes (LNs) that was dependent on IL-17–induced prostaglandin activity. The recruited neutrophils secreted a B cell–activating factor that highly accelerated plasma cell generation and antigen-specific antibody production. Reduction of neutrophil functions via granulocyte colony-stimulating factor neutralization significantly diminished plasma cell formation, directly linking EG with the humoral immune response. We conclude that neutrophils are capable of directly regulating T cell–dependent B cell responses in the LN.

A Distinct Region in Erythropoietin that Induces Immuno/Inflammatory Modulation and Tissue Protection

Beneficial effects of short-term whole-molecule erythropoietin (EPO) therapy have been demonstrated on several animal models of diverse central nervous system pathology. However, the increased hematocrit induced by EPO-driven marrow stimulation greatly limits its potential for side effect-free therapy. We created a library of EPO-derived fragments based on the hypothesis that 2 distinct functions, erythropoiesis and tissue protection, reside in different regions of the molecule. Several small EPO-derived peptides within the Aβ loop of whole EPO molecule were screened for tissue protection in EAE mice. The 19-mer JM-4 peptide that contains 2 cysteine molecules consistently demonstrated the most potent clinical beneficial effects without producing hematocrit alterations in animal models of EAE. The JM-4-induced tissue protection was associated with modulation of the immunoregulatory process that drives inflammation and provokes subsequent autoimmune damage. Like the whole EPO molecule, JM-4 effectively modulated immune/inflammatory reaction within both the peripheral lymphatic tissue and central nervous system. The major effects induced by JM-4 include blocked expansion of monocyte/dendritic antigen presenting cell and T helper 17 cell populations, decreased proinflammatory cytokine production, and sharply enhanced expansion of the regulatory T-cell population. JM-4 shows promise for treatment of a broad spectrum of neural and non-neural conditions associated with inflammation.

Adoptive transfer of cytokine-induced immunomodulatory adult microglia attenuates experimental autoimmune encephalomyelitis in DBA/1 mice

Microglia are resident antigen-presenting cells in the central nervous system (CNS) that either suppress or promote disease depending on their activation phenotype and the microenvironment. Multiple sclerosis (MS) is a chronic inflammatory disease causing demyelination and nerve loss in the CNS, and experimental autoimmune encephalomyelitis (EAE) is an animal model of MS that is widely used to investigate pathogenic mechanisms and therapeutic effects. We isolated and cultured microglia from adult mouse brains and exposed them to specific combinations of stimulatory molecules and cytokines, the combination of IL-4, IL-10, and TGF-β yielding the optimal regime for induction of an immunosuppressive phenotype (M2). M2 microglia were characterized by decreased expression or production of CD86, PD-L1, nitric oxide, and IL-6, increased expression of PD-L2, and having a potent capacity to retain their phenotype on secondary proinflammatory stimulation. M2 microglia induced regulatory T cells, suppressed T-cell proliferation, and downmodulated M1-associated receptor expression in M1 macrophages. Myelin oligodendrocyte glycoprotein (MOG)-induced EAE was induced in DBA/1 mice and at different time points (0, 5, 12, or 15 days postimmunization) 3 × 10⁵ M2 microglia were transferred intranasally. A single transfer of M2 microglia attenuated the severity of established EAE, which was particularly obvious when the cells were injected at 15 days postimmunization. M2 microglia-treated mice had reduced inflammatory responses and less demyelination in the CNS. Our findings demonstrate that adult M2 microglia therapy represents a novel intervention that alleviated established EAE and that this therapeutic principle may have relevance for treatment of MS patients.

Autoimmune disease in the brain--how to spot the culprits and how to keep them in check

Current concepts attribute an early and central role for auto-aggressive, myelin-specific T-lymphocytes in the pathogenesis of multiple sclerosis. This view emerged from immunological and pathological findings in experimental autoimmune encephalitis, an animal model characterised by pathological lesions closely resembling the ones found in multiple sclerosis. Furthermore, therapeutic strategies targeting the functions of these encephalitogenic T cells which attenuate their pathogenicity such as glatiramer acetate or anti-VLA4 antibody treatments represent proven approaches in multiple sclerosis. Nonetheless, all therapies evaluated to date either insufficiently dampen down inflammation or completely block immune processes. For this reason, there is a need to identify new therapeutic targets. We have employed live intravital two-photon microscopy to learn more about the behaviour of T cells during the preclinical phase of EAE, when T cells acquire the properties required to invade their target organ. Furthermore, we were able to identify an unexpected locomotive behaviour of T cells at the blood-brain barrier, which occurs immediately before diapedesis and the induction of paralytic disease. Such studies might open new avenues for the treatment of CNS autoimmune diseases. Multiple sclerosis is considered to be an autoimmune disease in which self-reactive T cells enter the central nervous system (CNS) and create an inflammatory milieu that destroys myelin and neurons. Immunomodulatory strategies for the treatment of multiple sclerosis target this process by attempting to inactivate these auto-aggressive T cells. However, so far, these strategies have failed to extinguish disease activity completely. For this reason, there is a need to understand in more detail the mechanisms by which T cells become encephalitogenic, how they enter the nervous system, and what the signals are that guide them along this path. If these processes could be better understood, it may be possible to design more effective and specific therapies for multiple sclerosis. This article will give a brief overview about our recent findings obtained using intravital imaging of autoaggressive effector T cells in an experimental model of multiple sclerosis. This new technological approach might help to fill some gaps in the understanding of autoimmune pathogenesis of multiple sclerosis.

The effects of teriflunomide on lymphocyte subpopulations in human peripheral blood mononuclear cells in vitro

Teriflunomide is an inhibitor of dihydro-orotate dehydrogenase (DHODH), and is hypothesized to ameliorate multiple sclerosis by reducing proliferation of stimulated lymphocytes. We investigated teriflunomide's effects on proliferation, activation, survival, and function of stimulated human peripheral blood mononuclear cell subsets in vitro. Teriflunomide had little/no impact on lymphocyte activation but exerted significant dose-dependent inhibition of T- and B-cell proliferation, which was uridine-reversible (DHODH-dependent). Viability analyses showed no teriflunomide-associated cytotoxicity. Teriflunomide significantly decreased release of several pro-inflammatory cytokines from activated monocytes in a DHODH-independent fashion. In conclusion, teriflunomide acts on multiple immune cell types and processes via DHODH-dependent and independent mechanisms.

Modeling the heterogeneity of multiple sclerosis in animals

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system (CNS) manifested with varying clinical course, pathology, and inflammatory patterns. There are multiple animal models that reflect different aspects of this heterogeneity. Collectively, these models reveal a balance between pathogenic and regulatory CD4(+) T cells, CD8(+) T cells, and B cells that influences the incidence, timing, and severity of CNS autoimmunity. In this review we discuss experimental autoimmune encephalomyelitis (EAE) models that have been used to study the pathogenic and regulatory roles of these immune cells; models that recapitulate different aspects of the disease seen in patients with MS, and questions remaining for future studies.

Two discreet subsets of CD8 T cells modulate PLP(91-110) induced experimental autoimmune encephalomyelitis in HLA-DR3 transgenic mice

Previously we showed that transgenic mice expressing human HLA-DR3 gene are susceptible to PLP(91-110) induced experimental autoimmune encephalomyelitis (EAE) and can serve as an animal model of multiple sclerosis (MS). HLA-DR3 mice with EAE showed increased number of CD8 T cells indicating their important role in disease pathogenesis. The role of CD8 T cells in MS, an inflammatory demyelinating disease of CNS, has been enigmatic as it has been assigned both regulatory and pathogenic roles. Therefore, to evaluate the role of CD8 T cells, we generated CD8 deficient HLA-DR3 transgenic mice (DR3.CD8(-/-)). Immunization with PLP(91-110) led to more severe EAE in DR3.CD8(-/-) mice compared to HLA-DR3 mice indicating a regulatory role for CD8 T cells. Interestingly, DR3.CD8(-/-) mice with EAE showed decreased CNS pathology compared to DR3 mice thus suggesting a pathogenic role for CD8 T cells. We show that these two subsets of CD8 T cells can be differentiated based on the surface expression of CD122 (IL-2 Rβ chain). CD8 T cells expressing CD122 (CD8+CD122+) play a regulatory role while CD8+CD122- T cells act as a pathogenic subset. CD122 expressing CD8 T cells are the regulatory subset of CD8 T cells and regulate the encephalitogenic CD4 T cells through direct modulation of antigen presenting cells and/or through the release of immunoregulatory cytokines such as IL-10, IFNγ and TGFβ. We also showed that adoptive transfer of CD8CD122- T cells caused increased spinal cord demyelination indicating that these are pathogenic subset of CD8 T cells. Our study suggests that CD8+ T cells play both regulatory as well as pathogenic role in disease pathogenesis of EAE. A better understanding of these subsets could aid in designing novel therapy for MS patients.

A distinct role of CD4+ Th17- and Th17-stimulated CD8+ CTL in the pathogenesis of type 1 diabetes and experimental autoimmune encephalomyelitis

Both CD4(+) Th17-cells and CD8(+) cytotoxic T lymphocytes (CTLs) are involved in type 1 diabetes and experimental autoimmune encephalomyelitis (EAE). However, their relationship in pathogenesis of these autoimmune diseases is still elusive. We generated ovalbumin (OVA)- or myelin oligodendrocyte glycoprotein (MOG)-specific Th17 cells expressing RORγt and IL-17 by in vitro co-culturing OVA-pulsed and MOG(35-55) peptide-pulsed dendritic cells (DC(OVA) and DC(MOG)) with CD4(+) T cells derived from transgenic OTII and MOG-T cell receptor mice, respectively. We found that these Th17 cells when transferred into C57BL/6 mice stimulated OVA- and MOG-specific CTL responses, respectively. To assess the above question, we adoptively transferred OVA-specific Th17 cells into transgenic rat insulin promoter (RIP)-mOVA mice or RIP-mOVA mice treated with anti-CD8 antibody to deplete Th17-stimulated CD8(+) T cells. We demonstrated that OVA-specific Th17-stimulated CTLs, but not Th17 cells themselves, induced diabetes in RIP-mOVA. We also transferred MOG-specific Th17 cells into C57BL/6 mice and H-2K(b-/-) mice lacking of the ability to generate Th17-stimulated CTLs. We further found that MOG-specific Th17 cells, but not Th17-activated CTLs induced EAE in C57BL/6 mice. Taken together, our data indicate a distinct role of Th17 cells and Th17-stimulated CTLs in the pathogenesis of TID and EAE, which may have great impact on the overall understanding of Th17 cells in the pathogenesis of autoimmune diseases.

CCR4 contributes to the pathogenesis of experimental autoimmune encephalomyelitis by regulating inflammatory macrophage function

Chemokines and their receptors play a critical role in orchestrating the immune response during experimental autoimmune encephalomyelitis (EAE). Expression of CCR4 and its ligand CCL22 has been observed in ongoing disease. Here we describe a role for CCR4 in EAE, illustrating delayed and decreased disease incidence in CCR4(-/-) mice corresponding with diminished CNS infiltrate. Peripheral T cell responses were unaltered in CCR4(-/-) mice; rather, disease reduction was related to reduced CD11b(+)Ly6C(hi) inflammatory macrophage (iMϕ) numbers and function. These results provide evidence that CCR4 regulates EAE development and further supports the involvement of CCR4 in iMϕ effector function.

Interferon-beta is a key regulator of proinflammatory events in experimental autoimmune encephalomyelitis

BACKGROUND

Interferon (IFN)-β is an effective therapy for relapsing-remitting multiple sclerosis, yet its mechanism of action remains ill-defined.

OBJECTIVES

Our objective was to characterize the role of IFN-β in immune regulation in experimental autoimmune encephalomyelitis (EAE).

METHODS

IFN-β(+/+) and IFN-β(-/-) mice were immunized with myelin oligodendrocyte glycoprotein peptide in the presence or absence of IFN-β, to induce EAE. Disease pathogenesis was monitored in the context of incidence, time of onset, clinical score, and immune cell activation in the brains, spleens and lymph nodes of affected mice.

RESULTS

Compared with IFN-β(+/+) mice, IFN-β(-/-) mice exhibited an earlier onset and a more rapid progression of EAE, increased numbers of CD11b(+) leukocytes infiltrating affected brains and an increased percentage of Th17 cells in the central nervous system and draining lymph nodes. IFN-β treatment delayed disease onset and reduced disease severity. Ex vivo experiments revealed that the lack of IFN-β results in enhanced generation of autoreactive T cells, a likely consequence of the absence of IFN-β-regulated events in both the CD4(+) T cells and antigen-presenting dendritic cells. Gene expression analysis of IFN-β-treated bone marrow macrophages (CD11b(+)) identified modulation of genes affecting T cell proliferation and Th17 differentiation.

CONCLUSIONS

We conclude that IFN-β acts to suppress the generation of autoimmune-inducing Th17 cells during the development of disease as well as modulating pro-inflammatory mediators.

Pathogenic MOG-reactive CD8+ T cells require MOG-reactive CD4+ T cells for sustained CNS inflammation during chronic EAE

XIncreasing evidence supports a role for CD8+ T cells in multiple sclerosis. In an attempt to isolate the contribution of CD8+ T cells in a murine model of MS, we immunized mice with a dominant CD8 epitope MOG37-46, a truncated version of MOG35-55. The data presented here show mild disease induced with MOG37-46, characterized by lower clinical scores, a decrease in CNS infiltration and a decrease in microglial activation. CD8+ T cells reactive to MOG37-46 are pro-inflammatory and traffic to the CNS; however, the presence of CD4+ T cells elicits more severe disease and sustained inflammation of the CNS.

The antidepressant venlafaxine ameliorates murine experimental autoimmune encephalomyelitis by suppression of pro-inflammatory cytokines

Antidepressants are known to impact on the immune system. In this study, we examined the immunomodulatory properties of venlafaxine, a selective serotonin/norepinephrine reuptake inhibitor (SNRI), in murine experimental autoimmune encephalomyelitis (EAE), a T-cell-mediated CNS demyelinating disease model of multiple sclerosis. EAE was induced in SJL/J mice by adoptive transfer of myelin-specific T cells. Mice received different doses of venlafaxine before induction and after onset of disease. Sustained daily oral treatment with 6, 20 and 60 mg/kg significantly ameliorated the clinical symptoms of the disease compared to vehicle during both preventive and therapeutic intervention. Venlafaxine suppressed the generation of pro-inflammatory cytokines IL-12 p40, TNF-alpha and IFN-gamma in encephalitogenic T-cell clones, splenocytes and peritoneal macrophages in vitro. It also diminished mRNA expression of a number of inflammatory genes in the inflamed CNS tissue, among them CD3, CD8, Granzyme B, IL-12 p40, IFN-gamma, TNF-alpha and the chemokines Ccl2 and RANTES, whereas the expression of brain-derived neurotrophic factor was increased. These findings demonstrate the strong immunomodulatory property of the selective SNRI venlafaxine. Further studies are warranted to clarify whether venlafaxine may exert similar effects in humans.

The role of CD8 suppressors versus destructors in autoimmune central nervous system inflammation

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) of putative autoimmune origin. Recent evidence indicates that MS autoimmunity is linked to defects in regulatory T-cell function, which normally regulates immune responses to self-antigens and prevents autoimmune diseases. MS and its animal model, experimental autoimmune encephalomyelitis (EAE), have long been regarded as a CD4(+) T-cell-mediated autoimmune disease. Studies addressing the role of CD8(+) T cells, however, have only recently begun to emerge. Pathogenic function was attributed to CD8(+) T cells because of their abundant presence or oligoclonal repertoire within MS lesions. However, CD8(+) T cells appeared to have important regulatory functions, as demonstrated in EAE or human MS studies. We here review the contribution of CD8(+) T cells to inflammation and immune regulation in CNS autoimmunity. The knowledge of distinct CD8(+) T-cell populations exerting destructive versus beneficial functions is summarized. The long-term goal is to delineate the exact phenotypic and functional characteristics of regulatory CD8(+) T-cell populations (natural as well as inducible) in humans. This knowledge may help to further develop concepts of reconstituting or enhancing endogenous mechanisms of immune tolerance in future therapeutic concepts for MS.

Myelin oligodendrocyte glycoprotein peptide-induced experimental allergic encephalomyelitis and T cell responses are unaffected by immunoproteasome deficiency

The inoculation of MOG peptides into C57BL/6 mice induces CD4(+) and CD8(+) T cells, and recent work has shown that adoptive transfer of the latter population, after extensive in vitro stimulation, can cause EAE in naïve recipient mice. Herein, we have evaluated the incidence and severity of EAE, and the induction of CD4(+) and CD8(+) T cells, following MOG peptide inoculation of wt mice and of LMP-2KO mice that lack an intact immunoproteasome, a cytoplasmic organelle that is induced by chronic inflammation and that may be important for the presentation of MHC class I epitopes to CD8(+) T cells. We report that EAE, evaluated by both clinical and histological criteria, is similar in LMP-2KO mice and wildtype C57B/6 mice (wt) in response to immunization with MOG peptides MOG(35-55) and MOG(40-54), suggesting that the immunoproteasome does not play a key role in the development of demyelinating disease. Furthermore, and consistent with previous reports, peptide-specific CD8(+) T cells were barely detectable in the CNS of peptide-immunized mice, although peptide-specific CD4(+) T cells were abundant. Therefore, we used a new technique to look for autoreactive CD8(+) T cells in MOG peptide-immunized mice, and we report the identification of CD4(+) and CD8(+) T cells that, as late as 19 days after peptide injection, are actively producing IFNgamma in vivo, in response to in vivo antigen contact.

Autoaggressive effector T cells in the course of experimental autoimmune encephalomyelitis visualized in the light of two-photon microscopy

Two photon microscopy (TPM) recently emerged as optical tool for the visualization of immune processes hundreds of micrometers deep in living tissue and organs. Here we summarize recent work on exploiting this technology to study brain antigen specific T cells. These cells are the cause of Experimental Autoimmune Encephalomyelitis (EAE) an autoimmune disease model of Multiple Sclerosis. TPM studies elucidated the dynamics of the autoaggressive effector T cells in peripheral immune milieus during preclinical EAE, where the cells become reprogrammed to enter their target organ. These studies revealed an unexpectedly lively locomotion behavior of the cells interrupted only by short-lasting contacts with the local immune stroma. Live T cell behavior was furthermore studied within the acutely inflamed CNS. Two distinct migratory patterns of the T cells were found: the majority of cells (60-70%) moved fast and seemingly unhindered through the compact CNS parenchyma. The motility of the other cell fraction was highly confined. The cells swung around a fixed cell pole forming long-lasting contacts to putative local antigen presenting cells.

Suppression of autoimmune encephalomyelitis by a neurokinin-1 receptor antagonist — A putative role for substance P in CNS inflammation

Substance P (SP) is an excitatory neurotransmitter in the central and peripheral nervous system. Most of its physiological functions are mediated through binding to the neurokinin-1 receptor (NK-1R). Recently, proinflammatory properties of SP have been described. In this study we utilized T cell transfer experimental autoimmune encephalomyelitis (EAE) to investigate the role of SP in CNS autoimmune disease. Treatment with the NK-1R antagonist CP-96,345 dramatically reduced clinical and histological signs of EAE if administered before disease onset. The protective effect of CP96,345 treatment was related to a reduced expression of the adhesion molecules ICAM-1 and VCAM-1 on CNS endothelia. The cellular composition or activation status of splenocytes was not affected by CP-96,345 administration, while the secretion of proinflammatory Th1 cytokines was reduced in treated animals. Th2 cytokines remained largely unaffected by NK-1 receptor antagonist treatment. In summary, our findings suggest that the protective effect of CP96,345 treatment is mediated by stabilization of the blood-brain barrier and suppression of Th1 immunity.

A Pathogenic Role for CD8+ T Cells in a Spontaneous Model of Demyelinating Disease

Transgenic (Tg) mice that overexpress the costimulatory ligand B7.2/CD86 on microglia spontaneously develop a T cell-mediated demyelinating disease. Characterization of the inflammatory infiltrates in the nervous tissue revealed a predominance of CD8+ T cells, suggesting a prominent role of this T cell subset in the pathology. In this study, we show that the same neurological disease occurred in Tg mice deficient in the generation of CD4+ T cells, with an earlier time of onset. Analysis of the CD8+ T cell repertoire at early stage of disease revealed the presence of selected clonal expansions in the CNS but not in peripheral lymphoid organs. We further show that Tg animals deficient in IFN-gamma receptor expression were completely resistant to disease development. Microglia activation that is an early event in disease development is IFN-gamma dependent and thus appears as a key element in disease pathogenesis. Collectively, our data indicate that the spontaneous demyelinating disease in this animal model occurs as a consequence of an inflammatory response initiated through the activation of CNS-specific CD8+ T cells by Tg expression of B7.2 within the target organ. Thus, autoreactive CD8+ T cells can contribute directly to the pathogenesis of neuroinflammatory diseases such as multiple sclerosis.

Autoreactive CD8+ T cells in multiple sclerosis: a new target for therapy?

Multiple sclerosis afflicts more than 1 million individuals worldwide and is widely considered to be an autoimmune disease. Traditionally, CD4(+) T helper cells have almost exclusively been held responsible for its immunopathogenesis, partly because certain MHC class II alleles clearly predispose for developing multiple sclerosis and also, because of their importance in inducing experimental autoimmune encephalomyelitis (EAE), the animal model for multiple sclerosis. However, several strategies that target CD4(+) T cells beneficially in EAE have failed to ameliorate disease activity in multiple sclerosis, and some have even triggered exacerbations. Recently, the potential importance of CD8(+) T cells has begun to emerge. Physiologically, CD8(+) T cells are essential for detecting and eliminating abnormal cells, whether infected or neoplastic. In multiple sclerosis, genetic associations with MHC class I alleles have now been established, and CD8(+) as well as CD4(+) T cells have been found to invade and clonally expand in inflammatory central nervous system plaques. Recent animal models induced by CD8(+) T cells show interesting similarities to multiple sclerosis, in particular, in lesion distribution (more inflammation in the brain relative to the spinal cord), although not all of the features of the human disease are recapitulated. Here we outline the arguments for a possible role for CD8(+) T cells, a lymphocyte subset that has long been underrated in multiple sclerosis and should now be considered in new therapeutic approaches.

A structural basis for CD8+ T cell-dependent recognition of non-homologous peptide ligands: implications for molecular mimicry in autoreactivity

Molecular mimicry of self-epitopes by viral antigens is one possible pathogenic mechanism underlying induction of autoimmunity. A self-epitope, mDBM, derived from mouse dopamine beta-mono-oxygenase (KALYDYAPI) sharing 44% sequence identity with the lymphocytic choriomeningitis virus-derived immunodominant epitope gp33 (KAVYNFATC/M), has previously been identified as a cross-reactive self-ligand, presentation of which results in autoimmunity. A rat peptide homologue, rDBM (KALYNYAPI, 56% identity to gp33), which displayed similar properties to mDBM, has also been identified. We herein report the crystal structure of H-2Db.rDBM and a comparison with the crystal structures of the cross-reactive H-2Db.gp33 and non-cross-reactive H-2Db.gp33 (V3L) escape variant (KALYNFATM, 88% identity to gp33). Despite the large sequence disparity, rDBM and gp33 peptides are presented in nearly identical manners by H-2Db, with a striking juxtaposition of the central sections of both peptides from residues p3 to p7. The structural similarity provides H-2Db in complex with either a virus-derived or a dopamine beta-mono-oxygenase-derived peptide with a shared antigenic identity that conserves the positioning of the heavy chain and peptide residues that interact with the T cell receptor (TCR). This stands in contrast to the structure of H-2Db.gp33 (V3L), in which a single conserved mutation, also present in rDBM, induces large movements of both the peptide backbone and the side chains that interact with the TCR. The TCR-interacting surfaces of the H-2Db.rDBM and H-2Db.gp33 major histocompatibility complexes are very similar with regard to shape, topology, and charge distribution, providing a structural basis for CD8 T cell activation by molecular mimicry and potential subsequent development of autoreactivity.

Schistosomiasis protects against multiple sclerosis

The incidences of schistosomiasis and multiple sclerosis (MS) are mutually exclusive worldwide suggesting that schistosomiasis may offer protection against the induction of the immune-mediated disease, MS. Recent studies using the mouse model of MS, experimental autoimmune encephalomyelitis, support a direct suppression of the onset of MS by chronic Schistosoma mansoni infection. Self-reactive Th1 but not Th2 responses develop in infected mice immunized with myelin oligodendrocyte glycoprotein albeit at reduced levels indicating that the induction of auto-reactive T cells is not abolished nor phenotypically altered. CNS infiltration by inflammatory cells, particularly macrophages, is significantly reduced in S. mansoni-infected, immunized mice compared to uninfected, immunized mice. Because activated macrophages are crucial to the induction of clinical disease, these findings support the hypothesis that differences in macrophage activation may contribute to the reduced incidence and delayed progression of experimental autoimmune encephalomyelitis during schistosomiasis.

Multiple sclerosis: brain-infiltrating CD8+ T cells persist as clonal expansions in the cerebrospinal fluid and blood

We surveyed the T cell receptor repertoire in three separate compartments (brain, cerebrospinal fluid, and blood) of two multiple sclerosis patients who initially had diagnostic brain biopsies to clarify their unusual clinical presentation but were subsequently confirmed to have typical multiple sclerosis. One of the brain biopsy specimens had been previously investigated by microdissection and single-cell PCR to determine the clonal composition of brain-infiltrating T cells at the single-cell level. Using complementarity-determining region 3 spectratyping, we identified several identical, expanded CD8+ (but not CD4+) T cell clones in all three compartments. Some of the expanded CD8+ T cells also occurred in sorted CD38+ blood cells, suggesting that they were activated. Strikingly, some of the brain-infiltrating CD8+ T cell clones persisted for >5 years in the cerebrospinal fluid and/or blood and may thus contribute to the progression of the disease.