Different interleukin-17-secreting Toll-like receptor+ T-cell subsets are associated with disease activity in multiple sclerosis

Hyperresponsiveness of Corticoid-Resistant Th17/Tc-17 Cells to TLR-2 and TLR-4 Ligands is a Feature of Multiple Sclerosis Patients at Higher Risk of Therapy Failure

Purpose

The presence of T cells expressing TLR-2 and TLR-4 has been associated with relapsing-remitting multiple sclerosis (RRMS) pathogenesis. Here, we evaluated whether the effectiveness of DMT in controlling clinical activity of the disease would be associated with modulation of proportion of TLRs+ T cells.

Patients and Methods

Whole peripheral blood mononuclear cells, purified CD4+ and CD8+ T cells from RRMS patients were cultured with different stimuli. The frequency of IL-17-secreting CD4+ and CD8+ T cells positive for TLR-2 and TLR-4 was determined by flow cytometry. The cytokine profile of these T cells following TLR-2 and TLR-4 stimulation was determined by Multiplex. Some of these T cell cultures were treated with hydrocortisone. The levels of LPS-binding protein (LBP) were dosed by ELISA. Clinical (occurrence of relapses) and radiological (number of active brain lesions) activity were evaluated during the 1-year follow-up.

Results

Despite DMT, high intensity of TLR-2 and TLR-4 expression on (CD4+ and CD8+) T-cells, as well as the frequency of IL-17-secreting (CD4+ and CD8+) T-cells, are predictive of future RRMS relapses. Moreover, higher cytokine production related to Th17/Tc-17 phenotypes in response to TLR-2 and TLR-4 agonists was observed in DMT-treated patients and displayed an elevated number of brain lesions. The hyperresponsiveness of MS-derived T-cells to TLR-2 and TLR-4 ligands, with high levels of IL-1β, IL-6, IL-17, IFN-γ and GM-CSF in response to both TLR agonists, positively correlated with plasma LBP levels. Interestingly, corticoid was less efficient in reducing Th17 and Tc-17 cytokine production induced by TLR-2 and TLR-4 ligands in DMT-treated patients who relapsed during follow-up.

Conclusion

Collectively, the data suggested that persistence of circulating Th17 and Tc17 cells expressing elevated levels of functional TLR-2 and TLR-4 could indicate high disease activity and lower therapeutic efficacy in RRMS patients.

Immunological dimensions of neuroinflammation and microglial activation: exploring innovative immunomodulatory approaches to mitigate neuroinflammatory progression

The increasing life expectancy has led to a higher incidence of age-related neurodegenerative conditions. Within this framework, neuroinflammation emerges as a significant contributing factor. It involves the activation of microglia and astrocytes, leading to the release of pro-inflammatory cytokines and chemokines and the infiltration of peripheral leukocytes into the central nervous system (CNS). These instances result in neuronal damage and neurodegeneration through activated nucleotide-binding domain and leucine-rich repeat containing (NLR) family pyrin domain containing protein 3 (NLRP3) and nuclear factor kappa B (NF-kB) pathways and decreased nuclear factor erythroid 2-related factor 2 (Nrf2) activity. Due to limited effectiveness regarding the inhibition of neuroinflammatory targets using conventional drugs, there is challenging growth in the search for innovative therapies for alleviating neuroinflammation in CNS diseases or even before their onset. Our results indicate that interventions focusing on Interleukin-Driven Immunomodulation, Chemokine (CXC) Receptor Signaling and Expression, Cold Exposure, and Fibrin-Targeted strategies significantly promise to mitigate neuroinflammatory processes. These approaches demonstrate potential anti-neuroinflammatory effects, addressing conditions such as Multiple Sclerosis, Experimental autoimmune encephalomyelitis, Parkinson's Disease, and Alzheimer's Disease. While the findings are promising, immunomodulatory therapies often face limitations due to Immune-Related Adverse Events. Therefore, the conduction of randomized clinical trials in this matter is mandatory, and will pave the way for a promising future in the development of new medicines with specific therapeutic targets.

Analysis of Differential TLR Activation in a Mouse Model of Multiple Sclerosis

Multiple sclerosis (MS) is a neurodegenerative and autoimmune disease affecting the central nervous system (CNS). The precise etiology of MS is still undeciphered, and signs and symptoms of the disease are varied and complex, ranging from axonal degeneration, synaptic, and neuronal loss to demyelination. Inflammation plays a critical role in determining the onset and the progression of MS, but there is still a lot of information missing before scientists come to understand what are the factors that contribute to the establishment of the neuroinflammation. Thus, various murine models, each representative of a specific hallmark of MS, are used to study the processes underlying the pathogenetic mechanisms of the disease in an attempt to find effective drugs for its treatment. Among the many causes of MS, viral infections appear to be one of the most prominent ones. In this scenario, the comprehension of the role of receptors activated upon the recognition of viral, and in general microbial, components in determining onset and progression of the neuroinflammation is of paramount importance. Toll-like receptors (TLRs) are evolutionarily conserved receptors that recognize several pathogen-associated molecular patterns (PAMPs), common structures of the pathogens, or the damage caused by the pathogens within the host. TLRs are thus directly involved in the regulation of inflammatory reactions and in the activation of the innate and, subsequently, the adaptive immune responses crucial for the elimination of infectious pathogens. The role of TLR activation in the development of MS is widely studied in various murine models of MS, as well as in MS patients. In this chapter, we will summarize the current knowledge about the contribution of TLRs to the development or progression of MS, and we will illustrate different methods commonly used for the investigation of the role of different TLRs in various murine models of the disease.

Application and prospect of targeting innate immune sensors in the treatment of autoimmune diseases

Dysregulation of auto-reactive T cells and autoantibody-producing B cells and excessive inflammation are responsible for the occurrence and development of autoimmune diseases. The suppression of autoreactive T cell activation and autoantibody production, as well as inhibition of inflammatory cytokine production have been utilized to ameliorate autoimmune disease symptoms. However, the existing treatment strategies are not sufficient to cure autoimmune diseases since patients can quickly suffer a relapse following the end of treatments. Pattern recognition receptors (PRRs), including Toll-like receptors (TLRs), Nod-like receptors (NLRs), RIG-I like receptors (RLRs), C-type lectin receptors (CLRs) and various nucleic acid sensors, are expressed in both innate and adaptive immune cells and are involved in the development of autoimmune diseases. Here, we have summarized advances of PRRs signaling pathways, association between PRRs and autoimmune diseases, application of inhibitors targeting PRRs and the corresponding signaling molecules relevant to strategies targeting autoimmune diseases. This review emphasizes the roles of different PRRs in activating both innate and adaptive immunity, which can coordinate to trigger autoimmune responses. The review may also prompt the formulation of novel ideas for developing therapeutic strategies against autoimmune diseases by targeting PRRs-related signals.

Major depression favors the expansion of Th17-like cells and decrease the proportion of CD39+Treg cell subsets in response to myelin antigen in multiple sclerosis patients

BACKGROUND

Mood disorders have been associated with risk of clinical relapses in multiple sclerosis (MS), a demyelinating disease mediated by myelin-specific T cells.

OBJECTIVES

We aimed to investigate the impact of major depressive disorder (MDD) and cytokine profile of T-cells in relapsing remitting MS patients.

METHODS

For our study, plasma and PBMC were obtained from 60 MS patients (30 with lifetime MDD) in remission phase. The PBMC cultures were stimulated with anti-CD3/anti-CD28 beads or myelin basic protein (MBP), and effector and regulatory T cell phenotypes were determined by flow cytometry. The cytokine levels, both in the plasma or in the supernatants collected from PBMC cultures, were quantified by Luminex. In some experiments, the effect of serotonin (5-HT) was investigated.

RESULTS

Here, higher Th17-related cytokine levels in response to anti-CD3/anti-CD28 and MBP were quantified in the plasma and PBMC cultures of the MS/MDD group in comparison with MS patients. Further, elevated frequency of CD4+ and CD8+ T cells capable of producing IL-17, IL-22 and GM-CSF was observed in depressed patients. Interestingly, the percentage of myelin-specific IFN-γ+IL-17+ and IFN-γ+GM-CSF+ CD4+ T cells directly correlated with neurological disabilities. In contrast, the occurrence of MDD reduced the proportion of MBP-specific CD39+Tregs subsets. Notably, the severity of both neurological disorder and depressive symptoms inversely correlated with these Tregs. Finally, the addition of 5-HT downregulated the release of Th17-related cytokines in response to anti-CD3/anti-CD28 and myelin antigen.

CONCLUSIONS

In summary, our findings suggested that recurrent major depression, by favoring imbalances of effector Th17 and Treg cell subsets, contributes to MS severity.

Toll-like receptor 10 gene polymorphism and risk of multiple sclerosis among Iraqi patients

Background

Toll-like receptors (TLRs) are a family of 10 pattern recognition receptors (TLR1–TLR10) involved in the regulation of inflammatory and immune responses besides their role in the pathogenesis of autoimmune diseases including multiple sclerosis (MS). TLR10 is the least studied TLR in MS, and data for single nucleotide polymorphisms (SNPs) of the TLR10 gene are limited. Therefore, a case–control study was performed on 85 patients with relapsing–remitting MS and 86 healthy controls (HC) to explore SNPs in the promoter region of TLR10 gene. A 927-bp region was amplified, and Sanger sequencing identified 10 SNPs with a minor allele frequency ≥ 10% (rs200395112 T/A, rs201802754 A/T, rs201228097 T/A, rs113588825 G/A, rs10004195 T/A, rs10034903 C/G, rs10012016 G/A/C, rs10012017 G/T, rs33994884 T/Deletion [Del] and rs28393318 A/G).

Results

Del allele and T/Del genotype of rs33994884, as well as AG genotype of rs28393318, showed significantly lower frequencies in MS patients compared to HC. Allele and genotype frequencies of the 10 SNPs showed no significant differences between MS patients classified according to the Expanded Disability Status Scale. Haplotype analysis revealed that haplotype A-T-A-G-A-G-G-T-A showed a significantly increased frequency in MS patients compared to HC (odds ratio [OR] = 9.70; 95% confidence interval [CI] = 1.28–73.31; corrected probability [pc] = 0.03), while frequency of A-T-A-G-T-C-A-T-G haplotype was significantly decreased (OR = 0.10; 95% CI = 0.01–0.85; pc = 0.05).

Conclusions

The study indicated that two SNPs may influence susceptibility to MS (rs33994884 and rs28393318), but haplotype analysis of TLR10 gene SNPs was more informative.

Case Report: Exacerbation of Relapses Following mRNA COVID-19 Vaccination in Multiple Sclerosis: A Case Series

Introduction

mRNA coronavirus disease 2019 (COVID-19) vaccination has been widely used to arrest the spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Rarely, autoimmune events such as relapses in patients with multiple sclerosis (MS) have been reported after vaccination. However, the possible effects of vaccination in a patient already experiencing the symptoms of a relapse represent an unusual scenario that has not been described.

Patients and Methods

This is a retrospective case series of four patients from three major tertiary referral centers that received mRNA COVID-19 vaccination after starting with symptoms of acute demyelination of the central nervous system due to non-recognized MS. A detailed description of each case, including MRI studies, serum light-neurofilament levels, and cerebrospinal fluid (CSF) cytokine profile, is provided.

Case Description

All patients presented exacerbation of ongoing symptoms after vaccination (range 14-112 days first dose). All patients presented MRI features suggestive of highly active MS and fulfilled McDonald 2017 criteria at the time of presentation. All patients presented high serum light-neurofilament levels and oligoclonal G bands restricted to the CSF. Higher levels of interleukin-6 in the CSF were present in the more severe cases.

Discussion

We describe exacerbation of relapses after mRNA COVID-19 vaccination. We hypothesize RNA sensors such as Toll-like receptor 7 may be activated and contribute to amplify the inflammatory response during a relapse.

Conclusion

Patients should seek medical attention if experiencing acute neurological symptoms, especially before vaccination. Fast diagnostic procedures and prompt treatment should be performed in these patients. Pharmacovigilance and further study are warranted to confirm causality.

Emerging role of bystander T cell activation in autoimmune diseases

Autoimmune disease is known to be caused by unregulated self-antigen-specific T cells, causing tissue damage. Although antigen specificity is an important mechanism of the adaptive immune system, antigen non-related T cells have been found in the inflamed tissues in various conditions. Bystander T cell activation refers to the activation of T cells without antigen recognition. During an immune response to a pathogen, bystander activation of self-reactive T cells via inflammatory mediators such as cytokines can trigger autoimmune diseases. Other antigen-specific T cells can also be bystander-activated to induce innate immune response resulting in autoimmune disease pathogenesis along with self-antigen-specific T cells. In this review, we summarize previous studies investigating bystander activation of various T cell types (NKT, γδ T cells, MAIT cells, conventional CD4⁺, and CD8⁺ T cells) and discuss the role of innate-like T cell response in autoimmune diseases. In addition, we also review previous findings of bystander T cell function in infection and cancer. A better understanding of bystander-activated T cells versus antigen-stimulated T cells provides a novel insight to control autoimmune disease pathogenesis.

Elevated proportion of TLR2- and TLR4-expressing Th17-like cells and activated memory B cells was associated with clinical activity of cerebral cavernous malformations

BACKGROUND

Recent evidences have suggested the involvement of toll-like receptor (TLR)-4 in the pathogenesis of cerebral cavernous malformations (CCM). Elevated frequency of TLR+T-cells has been associated with neurological inflammatory disorders. As T-cells and B-cells are found in CCM lesions, the objective of the present study was to evaluate the cytokine profile of T-cells expressing TLR2 and TLR4, as well as B-cell subsets, in asymptomatic (CCMAsympt) and symptomatic (CCMSympt) patients.

METHODS

For our study, the cytokine profile from TLR2+ and TLR4+ T-cell and B-cell subsets in CCMAsympt and CCMSympt patients was investigated using flow cytometry and ELISA. T-cells were stimulated in vitro with anti-CD3/anti-CD28 beads or TLR2 (Pam3C) and TLR4 (LPS) ligands.

RESULTS

CCMSymptc patients presented a higher frequency of TLR4+(CD4+ and CD8+) T-cells and greater density of TLR4 expression on these cells. With regard to the cytokine profile, the percentage of TLR2+ and TLR4+ Th17 cells was higher in CCMSympt patients. In addition, an elevated proportion of TLR4+ Tc-1 cells, as well as Tc-17 and Th17.1 cells expressing TLR2 and TLR4, was observed in the symptomatic patients. By contrast, the percentage of TLR4+ IL-10+CD4+ T cells was higher in the CCMAsympt group. Both Pam3C and LPS were more able to elevate the frequency of IL-6+CD4+T cells and Th17.1 cells in CCMSympt cell cultures. Furthermore, in comparison with asymptomatic patients, purified T-cells from the CCMSympt group released higher levels of Th17-related cytokines in response to Pam3C and, mainly, LPS, as well as after activation via TCR/CD28. Concerning the B-cell subsets, a higher frequency of memory and memory activated B-cells was observed in CCMSympt patients.

CONCLUSIONS

Our findings reveal an increase in circulating Th17/Tc-17 cell subsets expressing functional TLR2 and, mainly, TLR4 molecules, associated with an increase in memory B-cell subsets in CCM patients with clinical activity of the disease.

Role of Toll-Like Receptors in Neuroimmune Diseases: Therapeutic Targets and Problems

Toll-like receptors (TLRs) are a class of proteins playing a key role in innate and adaptive immune responses. TLRs are involved in the development and progression of neuroimmune diseases via initiating inflammatory responses. Thus, targeting TLRs signaling pathway may be considered as a potential therapy for neuroimmune diseases. However, the role of TLRs is elusive and complex in neuroimmune diseases. In addition to the inadequate immune response of TLRs inhibitors in the experiments, the recent studies also demonstrated that partial activation of TLRs is conducive to the production of anti-inflammatory factors and nervous system repair. Exploring the mechanism of TLRs in neuroimmune diseases and combining with developing the emerging drug may conquer neuroimmune diseases in the future. Herein, we provide an overview of the role of TLRs in several neuroimmune diseases, including multiple sclerosis, neuromyelitis optica spectrum disorder, Guillain-Barré syndrome and myasthenia gravis. Emerging difficulties and potential solutions in clinical application of TLRs inhibitors will also be discussed.

Toll-like Receptor 2 in Autoimmune Inflammation

TLR signaling is critical for broad scale immune recognition of pathogens and/or danger molecules. TLRs are particularly important for the activation and the maturation of cells comprising the innate immune response. In recent years it has become apparent that several different TLRs regulate the function of lymphocytes as well, albeit to a lesser degree compared to innate immunity. TLR2 heterodimerizes with either TLR1 or TLR6 to broadly recognize bacterial lipopeptides as well as several danger-associated molecular patterns. In general, TLR2 signaling promotes immune cell activation leading to tissue inflammation, which is advantageous for combating an infection. Conversely, inappropriate or dysfunctional TLR2 signaling leading to an overactive inflammatory response could be detrimental during sterile inflammation and autoimmune disease. This review will highlight and discuss recent research advances linking TLR2 engagement to autoimmune inflammation.

Resolvin E1 Regulates Th17 Function and T Cell Activation

Resolvin E1 (RvE1) is a specialized pro-resolving lipid mediator derived from eicosapentaenoic acid and plays a critical role in resolving inflammation and tissue homeostasis. T_h17 cells are a distinct group of T helper (T_h) cells with tissue-destructive functions in autoimmune and chronic inflammatory diseases via the secretion of IL-17. Dendritic cell (DC)-mediated antigen presentation regulates the T_h17-induced progression of inflammation and tissue destruction. In this study, we hypothesized that the RvE1 would restore homeostatic balance and inflammation by targeting the T_h17 function. We designed three experiments to investigate the impact of RvE1 on different phases of T_h17 response and the potential role of DCs: First CD4⁺ T cells were induced by IL-6/TGF_β to measure the effect of RvE1 on T_h17 differentiation in an inflammatory milieu. Second, we measured the impact of RvE1 on DC-stimulated T_h17 differentiation in a co-culture model. Third, we measured the effect of RvE1 on DC maturation. RvE1 blocked the CD25, CCR6 and IL-17 expression; IL-17, IL-21, IL-10, and IL-2 production, suggesting inhibition of T cell activation, T_h17 stimulation and chemoattraction. RvE1 also suppressed the activation of DCs by limiting their pro-inflammatory cytokine production. Our findings collectively demonstrated that the RvE1 targeted the T_h17 activation and the DC function as a potential mechanism for inflammatory resolution and acquired immune response.

Toll-like receptor 2 and 4 antagonism for the treatment of experimental autoimmune encephalomyelitis (EAE)-related pain

Neuropathic pain is a major symptom of multiple sclerosis (MS) with up to 92% of patients reporting bodily pain, and 85% reporting pain severe enough to cause functional disability. None of the available therapeutics target MS pain. Toll-like receptors 2 and 4 (TLR2/TLR4) have emerged as targets for treating a wide array of autoimmune disorders, including MS, as well as having demonstrated success at suppressing pain in diverse animal models. The current series of studies tested systemic TLR2/TLR4 antagonists in males and females in a low-dose Myelin oligodendrocyte glycoprotein (MOG) experimental autoimmune encephalomyelitis (EAE) model, with reduced motor dysfunction to allow unconfounded testing of allodynia through 50+ days post-MOG. The data demonstrated that blocking TLR2/TLR4 suppressed EAE-related pain, equally in males and females; upregulation of dorsal spinal cord proinflammatory gene expression for TLR2, TLR4, NLRP3, interleukin-1β, IkBα, TNF-α and interleukin-17; and upregulation of dorsal spinal cord expression of glial immunoreactivity markers. In support of these results, intrathecal interleukin-1 receptor antagonist reversed EAE-induced allodynia, both early and late after EAE induction. In contrast, blocking TLR2/TLR4 did not suppress EAE-induced motor disturbances induced by a higher MOG dose. These data suggest that blocking TLR2/TLR4 prevents the production of proinflammatory factors involved in low dose EAE pathology. Moreover, in this EAE model, TLR2/TLR4 antagonists were highly effective in reducing pain, whereas motor impairment, as seen in high dose MOG EAE, is not affected.

Selective serotonin reuptake inhibitor attenuates the hyperresponsiveness of TLR2+ and TLR4+ Th17/Tc17-like cells in multiple sclerosis patients with major depression

Elevated frequency of Th17-like cells expressing Toll-like receptors (TLRs) has been recently associated with relapsing-remitting multiple sclerosis (MS) pathogenesis, a chronic inflammatory demyelinating autoimmune disease of the central nervous system. We aimed to investigate the impact of current major depressive disorder (MDD) on the behaviour of these cells following in vitro stimulation with TLR2, TLR4, TLR5 and TLR9 agonists. Here, the level of both cell proliferation and cytokine production related to Th17/Tc17 phenotypes in response to TLR2 (Pam3C) and TLR4 (LPS) ligands was significantly higher in CD4+ and CD8+ T-cell cultures from MS/MDD patients when compared to non-depressed patients. These cytokine levels were positively associated with neurological disabilities in patients. No difference for responsiveness to TLR5 (flagellin) and TLR9 (ODN) agonists was observed. LPS, but not Pam3C, induced significant IL-10 release, mainly in patients without MDD. Interestingly, more intense expression of TLR2 and TLR4 on these cells was observed in MDD patients. Finally, in vitro addition of serotonin and treatment of MDD patients with selective serotonin reuptake inhibitors (SSRIs) reduced the production of Th17/Tc17-related cytokines by CD4+ and CD8+ T cells in response to Pam3C and LPS. However, only SSRI therapy diminished the frequency and intensity of TLR2 and TLR4 expression on circulating CD4+ and CD8+ T cells. In summary, although preliminary, our findings suggest that adverse events that elevate circulating levels of TLR2 and TLR4 ligands can affect MS pathogenesis, particularly among depressed patients.

The expression profile of virus-recognizing toll-like receptors in natural killer cells of Cypriot multiple sclerosis patients

Objective

The exact aetiology of multiple sclerosis (MS) remains elusive, although several environmental and genetic risk factors have been implicated to varying degrees. Among the environmental risk factors, viral infections have been suggested as strong candidates contributing to MS pathology/progression. Viral recognition and control are largely tasked to the NK cells via TLR recognition and various cytotoxic and immunoregulatory functions. Additionally, the complex roles of different TLRs in MS pathology are highlighted in multiple, often contradictory, studies. The present work aims to analyse the TLR expression profile of NK cells isolated from MS patients. Highly purified CD56⁺CD3⁻ NK cells isolated from peripheral blood of MS patients (n = 19) and healthy controls (n = 20) were analysed via flow cytometry for their expression of viral antigen-recognizing TLRs (TLR2, TLR3, TLR7, and TLR9).

Results

No difference was noted in TLR expression between MS patients and healthy controls. These results aim to supplement previous findings which study expressional or functional differences in TLRs present in various subsets of the immune system in MS, thus aiding in a better understanding of MS as a complex multifaceted disease.

Bystander CD4+ T cells: crossroads between innate and adaptive immunity

T cells are the central mediators of both humoral and cellular adaptive immune responses. Highly specific receptor-mediated clonal selection and expansion of T cells assure antigen-specific immunity. In addition, encounters with cognate antigens generate immunological memory, the capacity for long-term, antigen-specific immunity against previously encountered pathogens. However, T-cell receptor (TCR)-independent activation, termed “bystander activation”, has also been found. Bystander-activated T cells can respond rapidly and secrete effector cytokines even in the absence of antigen stimulation. Recent studies have rehighlighted the importance of antigen-independent bystander activation of CD4⁺ T cells in infection clearance and autoimmune pathogenesis, suggesting the existence of a distinct innate-like immunological function performed by conventional T cells. In this review, we discuss the inflammatory mediators that activate bystander CD4⁺ T cells and the potential physiological roles of these cells during infection, autoimmunity, and cancer.

Immune cells that become activated in the absence of antigen stimulation could be harnessed in the fight against infection, autoimmunity, and cancer. Je-Min Choi and colleagues from Hanyang University in Seoul, South Korea, review how the immune system can deploy helper T cells through an unusual process called bystander activation. Most T cells become activated only after receptors on their surface bind to specific cognate antigen. In contrast, bystander T cells are activated non-specifically in response to cytokines and other pro-inflammatory mediators. Studies have shown that this cell population has a variety of protective and pathogenic functions, for example, guarding against multiple sclerosis, aggravating the symptoms of parasitic infections and promoting antitumor immunity. A better understanding of these immune cells could lead to new therapeutic options for these diseases.

Pattern Recognition Receptors in Multiple Sclerosis and Its Animal Models

Pattern recognition receptors (PRRs) coordinate the innate immune response and have a significant role in the development of multiple sclerosis (MS). Accumulating evidence has identified both pathogenic and protective functions of PRR signaling in MS and its animal model, experimental autoimmune encephalomyelitis (EAE). Additionally, evidence for PRR signaling in non-immune cells and PRR responses to host-derived endogenous ligands has also revealed new pathways controlling the development of CNS autoimmunity. Many PRRs remain uncharacterized in MS and EAE, and understanding the distinct triggers and functions of PRR signaling in CNS autoimmunity requires further investigation. In this brief review, we discuss the diverse pathogenic and protective functions of PRRs in MS and EAE, and highlight major avenues for future research.

Immunomodulatory receptors are differentially expressed in B and T cell subsets relevant to autoimmune disease

Inhibitory cell-surface receptors on lymphocytes, often called immune checkpoints, are powerful targets for cancer therapy. Despite their direct involvement in autoimmune pathology, they are currently not exploited therapeutically for autoimmune diseases. Understanding the expression pattern of these receptors in health and disease is essential for targeted drug design. Here, we designed three 23-colour flow cytometry panels for peripheral-blood T cells, including 15 lineage-defining markers and 21 immunomodulatory cell-surface receptors, and a 22-marker panel for B cells. Blood samples from healthy individuals, multiple sclerosis (MS), and lupus (SLE) patients were included in the study. Several receptors show differential expression on regulatory T cells (Treg) compared to T helper (Th) 1 and Th17 cells, and functional relevance of this difference could be shown for BTLA and CD5. Unbiased multiparametric analysis revealed a subset of activated CD8⁺ T cells and a subset of unswitched memory B cells that are diminished in MS and SLE, respectively.

TLR-2 and TLR-4 agonists favor expansion of CD4+ T cell subsets implicated in the severity of neuromyelitis optica spectrum disorders

BACKGROUND

High frequency of circulating Th17 cell subsets expressing TLR2, TLR4 and TLR9 was observed in Neuromyelitis optica spectrum disorder (NMOSD) patients, a severe humoral autoimmune disease of the central nervous system. Our objective was to evaluate the direct effects of different TLR ligands on CD4⁺ T-cells form those patients.

METHODS

CD4⁺ T-cell cultures from NMOSD and healthy individuals were stimulated with different TLR ligands and the cell proliferation and cytokine profile was analyzed by [³H] TdR up take and ELISA/ cytometry, respectively. The plasma levels of CD14 were determined by ELISA.

RESULTS

Here, Pam3C (TLR2) and LPS (TLR4) induced significant cell proliferation and IL-6, IL-17 and IL-21 production by CD4⁺ T-cells from NMOSD. Additionally, while both TLR ligands were more potent in favoring the expansion of T_FH-like cells, Pam3C reduced the frequency of IL-10-secreting FoxP3⁺and FoxP3^- CD4⁺ T-cells. With regard to disease severity, the levels of IL-6, IL-17 and IL-21 produced by CD4⁺ T-cells, as well as the frequency of T_FH-like cells, in response to TLR2 and TLR4 agonists were positively correlated with neurological disabilities and the occurrence of new acute relapses during follow up. Finally, circulating levels of CD14, an indirect marker of microbial translocation, were positively correlated with IL-6, IL-17 and IL-21 release by Pam3C- and LPS-activated CD4⁺ T-cells.

CONCLUSIONS

In summary, our data suggest that microbial antigens may affect NMOSD outcomes by favoring an imbalance between Th17 and TFH-like cells and regulatory T cell subsets.