Chronic Pain in Patients with Spinal Muscular Atrophy in Switzerland: A Query to the Spinal Muscular Atrophy Registry.

Background and Objectives: Chronic pain is a common symptom in various types of neuromuscular disorders. However, for patients with spinal muscular atrophy (SMA), the literature regarding chronic pain is scarce. Thus, this study assessed the prevalence of chronic pain in children, adolescents, and adults with SMA and investigated the influence of clinical characteristics on chronic pain. Materials and Methods: This study used data from 141 patients, which were collected by the Swiss Registry for Neuromuscular Disorders. Extracted data included information on pain (present yes/no, pain location, and pain medication) and clinical characteristics, such as SMA type, motor function, wheelchair use, scoliosis, and contractures. Results: The analyses revealed that the highest prevalence of chronic pain was observed in adolescents with 62%, followed by adults with 48%, children (6-12 years) with 39%, and children < 6 years with 10%. The legs, back, and hips were most frequently reported as pain locations. Sex (females), age (adolescents), and the presence of contractures and scoliosis (with surgery) were factors that were associated with chronic pain. Conclusions: These findings contribute to a better understanding of pain in SMA, shedding light on its prevalence and characteristics in different age groups, which underscores the importance of assessing and managing pain in patients with SMA.

Accuracy of Repetitive Ocular Vestibular-Evoked Myogenic Potentials to Diagnose Myasthenia Gravis in Patients With Ptosis or Diplopia.

BACKGROUND AND OBJECTIVES: We developed repetitive ocular vestibular-evoked myogenic potentials (roVEMP) as an electrophysiologic test that allows us to elicit the characteristic decrement of extraocular muscles in patients with ocular myasthenia gravis (OMG). Case-control studies demonstrated that roVEMP reliably differentiates patients with OMG from healthy controls. We now aimed to evaluate the diagnostic accuracy of roVEMP for OMG diagnosis in patients with ptosis and/or diplopia. METHODS: In this blinded prospective diagnostic accuracy trial, we compared roVEMP in 89 consecutive patients presenting with ptosis and/or diplopia suspicious of OMG with a multimodal diagnostic approach, including clinical examination, antibodies, edrophonium testing, repetitive nerve stimulation of accessory and facial nerves, and single-fiber EMG (SFEMG). We calculated the roVEMP decrement as the ratio between the mean of the first 2 responses compared with the mean of the sixth-ninth responses in the train and used cutoff of >9% (unilateral decrement) in a 30 Hz stimulation paradigm. RESULTS: Following a complete diagnostic work-up, 39 patients (44%) were diagnosed with ocular MG, while 50 patients (56%) had various other neuro-ophthalmologic conditions, but not MG (non-MG). roVEMP yielded 88.2% sensitivity, 30.2% specificity, 50% positive predictive value (PPV), and 76.5% negative predictive value (NPV). For comparison, SFEMG resulted in 75% sensitivity, 56% specificity, 55.1% PPV, and 75.7% NPV. All other diagnostic tests (except for the ice pack test) also yielded significantly higher positive results in patients with MG compared with non-MG. DISCUSSION: The study revealed a high sensitivity of 88.2% for roVEMP in OMG, but specificity and PPV were too low to allow for the OMG diagnosis as a single test. Thus, differentiating ocular MG from other neuro-ophthalmologic conditions remains challenging, and the highest diagnostic accuracy is still obtained by a multimodal approach. In this study, roVEMP can complement the diagnostic armamentarium for the diagnosis of MG. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that in patients with diplopia and ptosis, roVEMP alone does not accurately distinguish MG from non-MG disorders. TRIAL REGISTRATION INFORMATION: ClinicalTrials.gov: NCT03049956.

Guideline for the management of myasthenic syndromes.

Myasthenia gravis (MG), Lambert-Eaton myasthenic syndrome (LEMS), and congenital myasthenic syndromes (CMS) represent an etiologically heterogeneous group of (very) rare chronic diseases. MG and LEMS have an autoimmune-mediated etiology, while CMS are genetic disorders. A (strain dependent) muscle weakness due to neuromuscular transmission disorder is a common feature. Generalized MG requires increasingly differentiated therapeutic strategies that consider the enormous therapeutic developments of recent years. To include the newest therapy recommendations, a comprehensive update of the available German-language guideline 'Diagnostics and therapy of myasthenic syndromes' has been published by the German Neurological society with the aid of an interdisciplinary expert panel. This paper is an adapted translation of the updated and partly newly developed treatment guideline. It defines the rapid achievement of complete disease control in myasthenic patients as a central treatment goal. The use of standard therapies, as well as modern immunotherapeutics, is subject to a staged regimen that takes into account autoantibody status and disease activity. With the advent of modern, fast-acting immunomodulators, disease activity assessment has become pivotal and requires evaluation of the clinical course, including severity and required therapies. Applying MG-specific scores and classifications such as Myasthenia Gravis Activities of Daily Living, Quantitative Myasthenia Gravis, and Myasthenia Gravis Foundation of America allows differentiation between mild/moderate and (highly) active (including refractory) disease. Therapy decisions must consider age, thymic pathology, antibody status, and disease activity. Glucocorticosteroids and the classical immunosuppressants (primarily azathioprine) are the basic immunotherapeutics to treat mild/moderate to (highly) active generalized MG/young MG and ocular MG. Thymectomy is indicated as a treatment for thymoma-associated MG and generalized MG with acetylcholine receptor antibody (AChR-Ab)-positive status. In (highly) active generalized MG, complement inhibitors (currently eculizumab and ravulizumab) or neonatal Fc receptor modulators (currently efgartigimod) are recommended for AChR-Ab-positive status and rituximab for muscle-specific receptor tyrosine kinase (MuSK)-Ab-positive status. Specific treatment for myasthenic crises requires plasmapheresis, immunoadsorption, or IVIG. Specific aspects of ocular, juvenile, and congenital myasthenia are highlighted. The guideline will be further developed based on new study results for other immunomodulators and biomarkers that aid the accurate measurement of disease activity.

Immune checkpoint inhibitors induced side effects of the peripheral nervous system.

PURPOSE OF REVIEW: This review highlights recent knowledge on the diagnosis and treatment of immune checkpoint inhibitor-induced neurological side effects (irNAE) focussing on the neuromuscular system. RECENT FINDINGS: irNAEs mainly resemble sporadic neuromuscular autoimmune diseases and paraneoplastic neurological syndromes. However, neurological symptoms may be unspecific (muscle weakness, fatigue) in the oncological setting and carry the risk of misdiagnosis and delayed therapeutic intervention. The role of disease-specific neuromuscular autoantibodies in the diagnosis is controversial as preexisting autoantibodies may otherwise be present before immune checkpoint inhibitor (ICI) treatment without clinical symptoms and may not develop in case of irNAE manifestation. A new necrotising form of myositis (irMyositis) has been described presenting with facial weakness and ptosis mimicking myasthenia gravis. It comes along with a high rate of severe myocarditis accounting for a triad overlap syndrome (myasthenia/myositis/myocarditis). The role of modern biologicals in the treatment of irNAEs has to be determined. SUMMARY: irNAEs are rare but carry the risk of permanent morbidity and mortality. Early suspicion and diagnosis are key to prevent neurological sequelae. Beyond interruption of ICI administration, treatment corresponds to sporadic autoimmune diseases. The myasthenia/myositis/myocarditis overlap syndrome deserves special attention as it carries the highest risk of mortality. The role of neurotoxic pretreatment regimens, preexisting subclinical neurological autoimmune diseases and the risk of ICI-re-challenge after irNAEs has to be further investigated.

[Neuromuscular Practical Knowledge: Focus On Muscle Weakness]. / Neuromuskuläres Praxiswissen: Fokus Muskelschwäche.

INTRODUCTION: Muscle weakness is a common symptom in the general practice. The diagnostic work-up starts with distinguishing true muscle weakness from fatigue. The localization, time course and severity of muscle weakness as well as associated symptoms, concomitant diseases, medication and family history can help classify the weakness into certain main categories. These are genetic, inflammatory, infectious, neoplastic, toxic and metabolic/endocrine causes. Further laboratory investigations, ENMG, MRI, muscle biopsy and genetic testing can help to further narrow the differential diagnosis. Due to recent advances, particularly in the field of genetics and targeted immunomodulatory therapies, a growing number of diseases which present with muscular weakness can be treated successfully.

Antibodies Produced by CLL Phenotype B Cells in Patients With Myasthenia Gravis Are Not Directed Against Neuromuscular Endplates.

BACKGROUND AND OBJECTIVES: Myasthenia gravis (MG) can in rare cases be an autoimmune phenomenon associated with hematologic malignancies such as chronic lymphocytic leukemia (CLL). It is unclear whether in patients with MG and CLL, the leukemic B cells are the ones directly driving the autoimmune response against neuromuscular endplates. METHODS: We identified patients with acetylcholine receptor antibody-positive (AChR+) MG and CLL or monoclonal B-cell lymphocytosis (MBL), a precursor to CLL, and described their clinical features, including treatment responses. We generated recombinant monoclonal antibodies (mAbs) corresponding to the B-cell receptors of the CLL phenotype B cells and screened them for autoantigen binding. RESULTS: A computational immune cell screen revealed a subgroup of 5/38 patients with MG and 0/21 healthy controls who displayed a CLL-like B-cell phenotype. In follow-up hematologic flow cytometry, 2 of these 5 patients were diagnosed with an MBL. An additional patient with AChR+ MG as a complication of manifest CLL presented at our neuromuscular clinic and was successfully treated with the anti-CD20 therapy obinutuzumab plus chlorambucil. We investigated the specificities of expanding CLL-like B-cell clones to assess a direct causal link between the 2 diseases. However, we observed no reactivity of the clones against the AChR, antigens at the neuromuscular junction, or other common autoantigens. DISCUSSION: Our study suggests that AChR autoantibodies are produced by nonmalignant, polyclonal B cells The new anti-CD20 treatment obinutuzumab might be considered in effectively treating AChR+ MG. CLASSIFICATION OF EVIDENCE: This is a single case study and provides Class IV evidence that obinutuzumab is safe to use in patients with MG.

Diabetes insipidus and Guillain-Barré-like syndrome following CAR-T cell therapy: a case report.

BACKGROUND: Immune effector cell-associated neurotoxicity syndrome (ICANS) is a common adverse event of CD19-directed chimeric antigen receptor (CAR) T cell therapy. Other neurological adverse events, however, have not methodically been described and studied. Furthermore, safety data on CAR-T cell therapy in patients with central nervous system (CNS) lymphoma remain limited. MAIN BODY: We here report occurrence of a Guillain-Barré-like syndrome (GBS) and central diabetes insipidus (cDI) following tisagenlecleucel therapy for relapsed high-grade lymphoma with CNS involvement. Both complications were refractory to standard treatment of ICANS. Weakness of respiratory muscles required mechanical ventilation and tracheostomy while cDI was treated with desmopressin substitution for several weeks. Muscle-nerve biopsy and nerve conduction studies confirmed an axonal pattern of nerve damage. T cell-rich infiltrates and detection of the CAR transgene in muscle-nerve sections imply a direct or indirect role of CAR-T cell-mediated inflammation. In line with current treatment guidelines for GBS, intravenous immunoglobulin was administered and gradual but incomplete recovery was observed over the course of several months. CONCLUSIONS: This case report highlights the risk of rare but severe neurological adverse events, such as acute GBS or cDI, in patients treated with CAR-T cells. It further underlines the importance of appropriate patient surveillance and systematic reporting of rare complications to eventually improve treatment.

Azathioprine therapy induces selective NK cell depletion and IFN-γ deficiency predisposing to herpesvirus reactivation.

BACKGROUND: Azathioprine is a widely prescribed drug for patients with chronic inflammatory diseases such as myasthenia gravis or organ transplant recipients. Azathioprine exerts immunosuppressive effects by inhibiting intracellular purine synthesis and reducing the numbers of circulating B and T lymphocytes. Case reports indicate increased risk for serious infections that can occur despite regular measurements of lymphocyte counts during azathioprine therapy. OBJECTIVE: We sought to comprehensively investigate therapy-associated patient risks and the underlying immune dysfunction of azathioprine use. METHODS: Peripheral blood leukocytes were analyzed using single-cell mass and spectral flow cytometry to detect specific effects of azathioprine use on the systemic immune signature. Therapy-associated clinical features were analyzed in 2 independent cohorts of myasthenia gravis patients. RESULTS: Azathioprine therapy selectively induced pronounced CD56dimCD16+ natural killer cell depletion and concomitant IFN-γ deficiency. Cytokine profiling revealed a specific contraction of classical TH1 cells during azathioprine treatment. We further observed an increased occurrence of reactivation of endogenous latent herpesviruses in the azathioprine-treated group versus in patients with myasthenia gravis who were not receiving immunomodulatory treatment; this increased occurrence was validated in an independent cohort. CONCLUSION: Our study highlights the risk of development of adverse events during azathioprine therapy and suggests that natural killer cell monitoring could be valuable in clinical practice.

Twin study reveals non-heritable immune perturbations in multiple sclerosis.

Multiple sclerosis (MS) is a chronic inflammatory disorder of the central nervous system underpinned by partially understood genetic risk factors and environmental triggers and their undefined interactions1,2. Here we investigated the peripheral immune signatures of 61 monozygotic twin pairs discordant for MS to dissect the influence of genetic predisposition and environmental factors. Using complementary multimodal high-throughput and high-dimensional single-cell technologies in conjunction with data-driven computational tools, we identified an inflammatory shift in a monocyte cluster of twins with MS, coupled with the emergence of a population of IL-2 hyper-responsive transitional naive helper T cells as MS-related immune alterations. By integrating data on the immune profiles of healthy monozygotic and dizygotic twin pairs, we estimated the variance in CD25 expression by helper T cells displaying a naive phenotype to be largely driven by genetic and shared early environmental influences. Nonetheless, the expanding helper T cells of twins with MS, which were also elevated in non-twin patients with MS, emerged independent of the individual genetic makeup. These cells expressed central nervous system-homing receptors, exhibited a dysregulated CD25-IL-2 axis, and their proliferative capacity positively correlated with MS severity. Together, our matched-pair analysis of the extended twin approach allowed us to discern genetically and environmentally determined features of an MS-associated immune signature.

Single-cell profiling of myasthenia gravis identifies a pathogenic T cell signature.

Myasthenia gravis (MG) is an autoimmune disease characterized by impaired neuromuscular signaling due to autoantibodies targeting the acetylcholine receptor. Although its auto-antigens and effector mechanisms are well defined, the cellular and molecular drivers underpinning MG remain elusive. Here, we employed high-dimensional single-cell mass and spectral cytometry of blood and thymus samples from MG patients in combination with supervised and unsupervised machine-learning tools to gain insight into the immune dysregulation underlying MG. By creating a comprehensive immune map, we identified two dysregulated subsets of inflammatory circulating memory T helper (Th) cells. These signature ThCD103 and ThGM cells populated the diseased thymus, were reduced in the blood of MG patients, and were inversely correlated with disease severity. Both signature Th subsets rebounded in the blood of MG patients after surgical thymus removal, indicative of their role as cellular markers of disease activity. Together, this in-depth analysis of the immune landscape of MG provides valuable insight into disease pathogenesis, suggests novel biomarkers and identifies new potential therapeutic targets for treatment.

Pericytes regulate vascular immune homeostasis in the CNS.

Pericytes regulate the development of organ-specific characteristics of the brain vasculature such as the blood-brain barrier (BBB) and astrocytic end-feet. Whether pericytes are involved in the control of leukocyte trafficking in the adult central nervous system (CNS), a process tightly regulated by CNS vasculature, remains elusive. Using adult pericyte-deficient mice (Pdgfbret/ret ), we show that pericytes limit leukocyte infiltration into the CNS during homeostasis and autoimmune neuroinflammation. The permissiveness of the vasculature toward leukocyte trafficking in Pdgfbret/ret mice inversely correlates with vessel pericyte coverage. Upon induction of experimental autoimmune encephalomyelitis (EAE), pericyte-deficient mice die of severe atypical EAE, which can be reversed with fingolimod, indicating that the mortality is due to the massive influx of immune cells into the brain. Additionally, administration of anti-VCAM-1 and anti-ICAM-1 antibodies reduces leukocyte infiltration and diminishes the severity of atypical EAE symptoms of Pdgfbret/ret mice, indicating that the proinflammatory endothelium due to absence of pericytes facilitates exaggerated neuroinflammation. Furthermore, we show that the presence of myelin peptide-specific peripheral T cells in Pdgfbret/ret ;2D2tg mice leads to the development of spontaneous neurological symptoms paralleled by the massive influx of leukocytes into the brain. These findings indicate that intrinsic changes within brain vasculature can promote the development of a neuroinflammatory disorder.

GM-CSF and CXCR4 define a T helper cell signature in multiple sclerosis.

Cytokine dysregulation is a central driver of chronic inflammatory diseases such as multiple sclerosis (MS). Here, we sought to determine the characteristic cellular and cytokine polarization profile in patients with relapsing-remitting multiple sclerosis (RRMS) by high-dimensional single-cell mass cytometry (CyTOF). Using a combination of neural network-based representation learning algorithms, we identified an expanded T helper cell subset in patients with MS, characterized by the expression of granulocyte-macrophage colony-stimulating factor and the C-X-C chemokine receptor type 4. This cellular signature, which includes expression of very late antigen 4 in peripheral blood, was also enriched in the central nervous system of patients with relapsing-remitting multiple sclerosis. In independent validation cohorts, we confirmed that this cell population is increased in patients with MS compared with other inflammatory and non-inflammatory conditions. Lastly, we also found the population to be reduced under effective disease-modifying therapy, suggesting that the identified T cell profile represents a specific therapeutic target in MS.

Fate-Mapping of GM-CSF Expression Identifies a Discrete Subset of Inflammation-Driving T Helper Cells Regulated by Cytokines IL-23 and IL-1ß.

Pathogenic lymphocytes initiate the development of chronic inflammatory diseases. The cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) (encoded by Csf2) is a key communicator between pathogenic lymphocytes and tissue-invading inflammatory phagocytes. However, the molecular properties of GM-CSF-producing cells and the mode of Csf2 regulation in vivo remain unclear. To systematically study and manipulate GM-CSF+ cells and their progeny in vivo, we generated a fate-map and reporter of GM-CSF expression mouse strain (FROG). We mapped the phenotypic and functional profile of auto-aggressive T helper (Th) cells during neuroinflammation and identified the signature and pathogenic memory of a discrete encephalitogenic Th subset. These cells required interleukin-23 receptor (IL-23R) and IL-1R but not IL-6R signaling for their maintenance and pathogenicity. Specific ablation of this subset interrupted the inflammatory cascade, despite the unperturbed tissue accumulation of other Th subsets (e.g., Th1 and Th17), highlighting that GM-CSF expression not only marks pathogenic Th cells, but that this subset mediates immunopathology and tissue destruction.

Regulatory T Cells Restrain Pathogenic T Helper Cells during Skin Inflammation.

Psoriasis is a chronic relapsing, remitting interleukin (IL)-23/IL-17-driven skin disease mediated by the interplay of T cells and polymorphonuclear granulocytes. Although preclinical studies have provided insights into the mechanisms of disease initiation, the underpinnings of natural disease remission remain largely unknown. Here, we addressed the contribution of regulatory Foxp3+ T cells (Treg cells) in psoriasiform skin inflammation and remission using the Aldara-skin inflammation model in combination with the inducible depletion of Foxp3+ Treg cells. Loss of Treg cells exacerbated skin inflammation, but this did not involve increased γδ T cell expansion or the local production of the psoriasis-associated cytokines IL-17A, IL-17F, and IL-22, which are the main driving forces of disease development. Instead, Treg cells suppressed the infiltration of granulocyte-macrophage colony-stimulating factor (GM-CSF)-producing CD4+ T cells into the lesioned skin, and neutralizing GM-CSF in Treg cell-deficient mice reversed hyper-inflammation, resulting in disease regression. Therefore, we identified a non-redundant role of Treg cells restraining skin inflammation and mediating skin homeostasis.

Graft-versus-host disease, but not graft-versus-leukemia immunity, is mediated by GM-CSF-licensed myeloid cells.

Allogeneic hematopoietic cell transplantation (allo-HCT) not only is an effective treatment for several hematologic malignancies but can also result in potentially life-threatening graft-versus-host disease (GvHD). GvHD is caused by T cells within the allograft attacking nonmalignant host tissues; however, these same T cells mediate the therapeutic graft-versus-leukemia (GvL) response. Thus, there is an urgent need to understand how to mechanistically uncouple GvL from GvHD. Using preclinical models of full and partial MHC-mismatched HCT, we here show that the granulocyte-macrophage colony-stimulating factor (GM-CSF) produced by allogeneic T cells distinguishes between the two processes. GM-CSF drives GvHD pathology by licensing donor-derived phagocytes to produce inflammatory mediators such as interleukin-1ß and reactive oxygen species. In contrast, GM-CSF did not affect allogeneic T cells or their capacity to eliminate leukemic cells, retaining undiminished GvL responses. Last, tissue biopsies and peripheral blood mononuclear cells from patients with grade IV GvHD showed an elevation of GM-CSF-producing T cells, suggesting that GM-CSF neutralization has translational potential in allo-HCT.

High-Dimensional Single-Cell Mapping of Central Nervous System Immune Cells Reveals Distinct Myeloid Subsets in Health, Aging, and Disease.

Individual reports suggest that the central nervous system (CNS) contains multiple immune cell types with diverse roles in tissue homeostasis, immune defense, and neurological diseases. It has been challenging to map leukocytes across the entire brain, and in particular in pathology, where phenotypic changes and influx of blood-derived cells prevent a clear distinction between reactive leukocyte populations. Here, we applied high-dimensional single-cell mass and fluorescence cytometry, in parallel with genetic fate mapping systems, to identify, locate, and characterize multiple distinct immune populations within the mammalian CNS. Using this approach, we revealed that microglia, several subsets of border-associated macrophages and dendritic cells coexist in the CNS at steady state and exhibit disease-specific transformations in the immune microenvironment during aging and in models of Alzheimer's disease and multiple sclerosis. Together, these data and the described framework provide a resource for the study of disease mechanisms, potential biomarkers, and therapeutic targets in CNS disease.

Dysregulation of the Cytokine GM-CSF Induces Spontaneous Phagocyte Invasion and Immunopathology in the Central Nervous System.

Chronic inflammatory diseases are influenced by dysregulation of cytokines. Among them, granulocyte macrophage colony stimulating factor (GM-CSF) is crucial for the pathogenic function of T cells in preclinical models of autoimmunity. To study the impact of dysregulated GM-CSF expression in vivo, we generated a transgenic mouse line allowing the induction of GM-CSF expression in mature, peripheral helper T (Th) cells. Antigen-independent GM-CSF release led to the invasion of inflammatory myeloid cells into the central nervous system (CNS), which was accompanied by the spontaneous development of severe neurological deficits. CNS-invading phagocytes produced reactive oxygen species and exhibited a distinct genetic signature compared to myeloid cells invading other organs. We propose that the CNS is particularly vulnerable to the attack of monocyte-derived phagocytes and that the effector functions of GM-CSF-expanded myeloid cells are in turn guided by the tissue microenvironment.

The Cytokine GM-CSF Drives the Inflammatory Signature of CCR2+ Monocytes and Licenses Autoimmunity.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) has emerged as a crucial cytokine produced by auto-reactive T helper (Th) cells that initiate tissue inflammation. Multiple cell types can sense GM-CSF, but the identity of the pathogenic GM-CSF-responsive cells is unclear. By using conditional gene targeting, we systematically deleted the GM-CSF receptor (Csf2rb) in specific subpopulations throughout the myeloid lineages. Experimental autoimmune encephalomyelitis (EAE) progressed normally when either classical dendritic cells (cDCs) or neutrophils lacked GM-CSF responsiveness. The development of tissue-invading monocyte-derived dendritic cells (moDCs) was also unperturbed upon Csf2rb deletion. Instead, deletion of Csf2rb in CCR2(+)Ly6C(hi) monocytes phenocopied the EAE resistance seen in complete Csf2rb-deficient mice. High-dimensional analysis of tissue-infiltrating moDCs revealed that GM-CSF initiates a combination of inflammatory mechanisms. These results indicate that GM-CSF signaling controls a pathogenic expression signature in CCR2(+)Ly6C(hi) monocytes and their progeny, which was essential for tissue damage.

Deletion of Jun proteins in adult oligodendrocytes does not perturb cell survival, or myelin maintenance in vivo.

Oligodendrocytes, the myelin-forming glial cells of the central nervous system (CNS), are fundamental players in rapid impulse conduction and normal axonal functions. JunB and c-Jun are DNA-binding components of the AP-1 transcription factor, which is known to regulate different processes such as proliferation, differentiation, stress responses and death in several cell types, including cultured oligodendrocyte/lineage cells. By selectively inactivating Jun B and c-Jun in myelinating oligodendrocytes in vivo, we generated mutant mice that developed normally, and within more than 12 months showed normal ageing and survival rates. In the adult CNS, absence of JunB and c-Jun from mature oligodendrocytes caused low-grade glial activation without overt signs of demyelination or secondary leukocyte infiltration into the brain. Even after exposure to toxic or autoimmune oligodendrocyte insults, signs of altered oligodendrocyte viability were mild and detectable only upon cuprizone treatment. We conclude that JunB and c-Jun expression in post-mitotic oligodendrocytes is mostly dispensable for the maintainance of white matter tracts throughout adult life, even under demyelinating conditions.

PD-1 ligands expressed on myeloid-derived APC in the CNS regulate T-cell responses in EAE.

Disease progression in experimental autoimmune encephalomyelitis (EAE) is regulated by programmed death receptor 1 (PD-1) and its ligands, B7-H1 (programmed death ligand 1 (PD-L1)) and B7-DC (PD-L2). B7-H1 and B7-DC have negative regulatory effects upon binding PD-1 on activated T cells and B7-H1 deficiency increases severity of both diabetes and EAE. However, the role of PD-L expression on different APC in the CNS in regulating local T-cell function during relapsing EAE has not been examined. Our data show that the majority of CNS CD4+ T cells isolated during acute EAE are PD-1+, and T cells specific for relapse-associated epitopes express PD-1 upon antigen stimulation in the CNS. B7-H1 and B7-DC are differentially expressed on discrete APC populations in the inflamed CNS. B7-H1 and PD-1 have mainly inhibitory functions on CNS T cells. B7-H1 negatively regulates the stimulation of activated PD-1+ T(H) cells, in co-cultures with microglia and different CNS-infiltrating APC presenting endogenously processed peptides. The preponderance of IFN-gamma+ versus IL-17+ T cells in the CNS of B7-H1(-/-) mice suggests that B7-H1 more selectively suppresses T(H)-1 than T(H)-17 responses in vivo. In contrast, blockade of B7-DC has less pronounced regulatory effects. Overall, the results demonstrate that B7-H1 expressed by CNS myeloid APC negatively regulates T-cell activation during acute relapsing EAE.