IL-21 and IL-21 receptor expression in lymphocytes and neurons in multiple sclerosis brain

The role of Interleukin-21 (IL-21) in allergic disorders: Biological insights and regulatory mechanisms

In recent decades, allergic diseases subsequent from an IgE-mediated response to specific allergens have become a progressively public chronic disease worldwide. They have shaped an important medical and socio-economic burden. A significant proportion of allergic disorders are branded via a form 2 immune response relating Th2 cells, type 2 natural lymphoid cells, mast cells and eosinophils. Interleukin-21 (IL-21) is a participant of the type-I cytokine family manufactured through numerous subsets of stimulated CD4+ T cells and uses controlling properties on a diversity of immune cells. Increasingly, experimental sign suggests a character for IL-21 in the pathogenesis of numerous allergic disorders. The purpose of this review is to discuss the biological properties of IL-21 and to summaries current developments in its role in the regulation of allergic disorders.

OCA-B promotes autoimmune demyelination through control of stem-like CD4 + T cells

Stem-like T cell populations can selectively contribute to autoimmunity, but the activities that promote and sustain these populations are incompletely understood. Here, we show that T cell-intrinsic loss of the transcription cofactor OCA-B protects mice from experimental autoimmune encephalomyelitis (EAE) while preserving responses to CNS infection. In adoptive transfer EAE models driven by multiple antigen encounters, OCA-B deletion nearly eliminates CNS infiltration, proinflammatory cytokine production and clinical disease. OCA-B-expressing CD4 + T cells within the CNS of mice with EAE comprise a minority of the population but display a memory phenotype and preferentially confer disease. In a relapsing-remitting EAE model, OCA-B T cell deficiency specifically protects mice from relapse. During remission, OCA-B promotes the expression of Tcf7 , Slamf6 , and Sell in proliferating T cell populations. At relapse, OCA-B loss results in both the accumulation of an immunomodulatory CD4 + T cell population expressing Ccr9 and Bach2 , and the loss of pro-inflammatory gene expression from Th17 cells. These results identify OCA-B as a driver of pathogenic stem-like T cells.

T cell help shapes B cell tolerance

T cell help is a crucial component of the normal humoral immune response, yet whether it promotes or restrains autoreactive B cell responses remains unclear. Here, we observe that autoreactive germinal centers require T cell help for their formation and persistence. Using retrogenic chimeras transduced with candidate TCRs, we demonstrate that a follicular T cell repertoire restricted to a single autoreactive TCR, but not a foreign antigen-specific TCR, is sufficient to initiate autoreactive germinal centers. Follicular T cell specificity influences the breadth of epitope spreading by regulating wild-type B cell entry into autoreactive germinal centers. These results demonstrate that TCR-dependent T cell help can promote loss of B cell tolerance and that epitope spreading is determined by TCR specificity.

Candidate Genetic and Molecular Drivers of Dysregulated Adaptive Immune Responses After Traumatic Brain Injury

Abstract Neuroinflammation is a significant and modifiable cause of secondary injury after traumatic brain injury (TBI), driven by both central and peripheral immune responses. A substantial proportion of outcome after TBI is genetically mediated, with an estimated heritability effect of around 26%, but because of the comparatively small datasets currently available, the individual drivers of this genetic effect have not been well delineated. A hypothesis-driven approach to analyzing genome-wide association study (GWAS) datasets reduces the burden of multiplicity testing and allows variants with a high prior biological probability of effect to be identified where sample size is insufficient to withstand data-driven approaches. Adaptive immune responses show substantial genetically mediated heterogeneity and are well established as a genetic source of risk for numerous disease states; importantly, HLA class II has been specifically identified as a locus of interest in the largest TBI GWAS study to date, highlighting the importance of genetic variance in adaptive immune responses after TBI. In this review article we identify and discuss adaptive immune system genes that are known to confer strong risk effects for human disease, with the dual intentions of drawing attention to this area of immunobiology, which, despite its importance to the field, remains under-investigated in TBI and presenting high-yield testable hypotheses for application to TBI GWAS datasets.

The role of Interleukin-21 in autoimmune Diseases: Mechanisms, therapeutic Implications, and future directions

IL-21 is a multifunctional cytokine that regulates the functional activity of various immune cells. Initial studies have shown that IL-21 can influence the differentiation, proliferation and function of T and B cells, as well as promote the maturation and increase the cytotoxicity of CD8 + T cells and NK cells. During humoral immune responses, IL-21 has significant effects on B cell activation, differentiation and apoptosis. In addition, IL-21 promotes the differentiation of both naive and memory B cells, ultimately leading to the activation of plasma cells. The function of IL-21 in the immune system is complex, as it has the ability to either stimulate or inhibit immune responses. in addition, IL-21 facilitates the differentiation of naive and memory B cells into plasma cells. The functionality of IL-21 in the immune system is diverse, as it has the ability to stimulate or inhibit immune responses. This cytokine has been implicated in several diseases including cancer, allergies and autoimmune diseases. Research has suggested that this cytokine is involved in the development of autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. Several studies have suggested that inhibition of IL-21 has a therapeutic effect on autoimmune diseases. Therefore, targeting both the cytokine's receptor and IL-21 in autoimmune diseases may be an effective approach to reduce the severity of the disease or to treat it. This review will examine the biological effects of IL-21 on various immune cells and the role of the cytokine in autoimmune diseases.

Suppression of NK Cell Activation by JAK3 Inhibition: Implication in the Treatment of Autoimmune Diseases

Natural killer (NK) cell is an essential cytotoxic lymphocyte in our innate immunity. Activation of NK cells is of paramount importance in defending against pathogens, suppressing autoantibody production and regulating other immune cells. Common gamma chain (γc) cytokines, including IL-2, IL-15, and IL-21, are defined as essential regulators for NK cell homeostasis and development. However, it is inconclusive whether γc cytokine-driven NK cell activation plays a protective or pathogenic role in the development of autoimmunity. In this study, we investigate and correlate the differential effects of γc cytokines in NK cell expansion and activation. IL-2 and IL-15 are mainly responsible for NK cell activation, while IL-21 preferentially stimulates NK cell proliferation. Blockade of Janus tyrosine kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway by either JAK inhibitors or antibodies targeting γc receptor subunits reverses the γc cytokine-induced NK cell activation, leading to suppression of its autoimmunity-like phenotype in vitro. These results underline the mechanisms of how γc cytokines trigger autoimmune phenotype in NK cells as a potential target to autoimmune diseases.

Association of chronic periodontitis with multiple sclerosis: A systematic review and meta-analysis

BACKGROUND

Chronic periodontitis (CP) is a multifactorial, chronic inflammatory disease of microbial etiology that manifests as a result of the dysfunction of the immune mechanism, culminating in the destruction of the alveolar bone of the jaws. Multiple sclerosis (MS) is an autoimmune disorder that affects the central nervous system (CNS), leads to demyelination and degeneration of nerve axons and often causes severe physical and/or cognitive impairment. As CP and MS involve inflammatory mechanisms and immune dysfunction, researchers have attempted to study the association between them.

AIM

To systematically review the literature on the epidemiological association between CP and MS in adults.

METHODS

PRISMA 2020 statement was used in the study protocol. The design was done according to the Cochrane methodology. A comprehensive literature search was performed in PubMed, Scopus and Cochrane databases; a manual search and evaluation of the gray literature was also performed. The meta-analysis was performed by Review Manager (RevMan) 5.4. Odds ratio (OR) with 95% confidence interval (CI) was defined as the effect size of the outcome. Heterogeneity was assessed by Chi-square and I2. The articles evaluated were written in English, without a time limit, concern observational studies (patient-controls) and report the diagnostic criteria of the diseases. Duplicate entries were excluded. To evaluate the reliability of the results of each study, Newcastle-Ottawa Scale (NOS) and GRADE tools were used. Two independent reviewers did all evaluations with a resolution of discrepancies by a third.

RESULTS

Meta-analysis included three observation studies examined 3376 people. MS patients are significantly more likely to be diagnosed with CP than healthy controls (OR 1.93, 95% CI 1.54-2.42, p<0.0001).

CONCLUSION

A high prevalence of CP was found among MS patients compared with healthy controls. Healthcare professionals should be aware of the association between these pathological entities to provide patients with high-quality care through an effective and holistic diagnostic and therapeutic approach.

Cadmium Exposure Is Associated with Behavioral Deficits and Neuroimmune Dysfunction in BTBR T+ Itpr3tf/J Mice

Autism spectrum disorders (ASD) are neurobehavioral disabilities characterized by impaired social interactions, poor communication skills, and restrictive/repetitive behaviors. Cadmium is a common heavy metal implicated in ASD. In this study, we investigated the effects of Cd exposure on BTBR T+ Itpr3tf/J (BTBR) mice, an ASD model. We looked for changes in repetitive behaviors and sociability through experiments. We also explored the molecular mechanisms underlying the effects of Cd exposure, focusing on proinflammatory cytokines and pathways. Flow cytometry measured IL-17A-, IL-17F-, IL-21-, TNF-α-, STAT3-, and RORγt-expressing CD4+ T cells from the spleens of experimental mice. We then used RT-PCR to analyze IL-17A, IL-17F, IL-21, TNF-α, STAT3, and RORγ mRNA expression in the brain. The results of behavioral experiments showed that Cd exposure significantly increased self-grooming and marble-burying in BTBR mice while decreasing social interactions. Cd exposure also significantly increased the number of CD4+IL-17A+, CD4+IL-17F+, CD4+IL-21+, CD4+TNF-α+, CD4+STAT3+, and CD4+RORγt+ cells, while upregulating the mRNA expression of the six molecules in the brain. Overall, our results suggest that oral exposure to Cd aggravates behavioral and immune abnormalities in an ASD animal model. These findings have important implications for ASD etiology and provide further evidence of heavy metals contributing to neurodevelopmental disorders through proinflammatory effects.

T follicular helper cells and T follicular regulatory cells in autoimmune diseases

T follicular helper (Tfh) cells are heterogeneous and mainly characterized by expressing surface markers CXCR5, ICOS, and PD-1; cytokine IL-21; and transcription factor Bcl6. They are crucial for B-cell differentiation into long-lived plasma cells and high-affinity antibody production. T follicular regulatory (Tfr) cells were described to express markers of conventional T regulatory (Treg) cells and Tfh cells and were able to suppress Tfh-cell and B-cell responses. Evidence has revealed that the dysregulation of Tfh and Tfr cells is positively associated with the pathogenic processes of autoimmune diseases. Herein, we briefly introduce the phenotype, differentiation, and function of Tfh and Tfr cells, and review their potential roles in autoimmune diseases. In addition, we discuss perspectives to develop novel therapies targeting Tfh/Tfr balance.

Multiple sclerosis: Motor dysfunction

Multiple sclerosis is a chronic neurological disease characterized by inflammation and degeneration within the central nervous system. Over the course of the disease, most MS patients successively accumulate inflammatory lesions, axonal damage, and diffuse CNS pathology, along with an increasing degree of motor disability. While the pharmacological approach to MS targets inflammation to decrease relapse rates and relieve symptoms, disease-modifying therapy and immunosuppressive medications may not prevent the accumulation of pathology in most patients leading to long-term motor disability. This has been met with recent interest in promoting plasticity-guided concepts, enhanced by neurophysiological and neuroimaging approaches to address the preservation of motor function.

Neuroinflammation: Extinguishing a blaze of T cells

Inflammation is a biological process that dynamically alters the surrounding microenvironment, including participating immune cells. As a well-protected organ surrounded by specialized barriers and with immune privilege properties, the central nervous system (CNS) tightly regulates immune responses. Yet in neuroinflammatory conditions, pathogenic immunity can disrupt CNS structure and function. T cells in particular play a key role in promoting and restricting neuroinflammatory responses, while the inflamed CNS microenvironment can influence and reshape T cell function and identity. Still, the contraction of aberrant T cell responses within the CNS is not well understood. Using autoimmunity as a model, here we address the contribution of CD4 T helper (Th) cell subsets in promoting neuropathology and disease. To address the mechanisms antagonizing neuroinflammation, we focus on the control of the immune response by regulatory T cells (Tregs) and describe the counteracting processes that preserve their identity under inflammatory challenges. Finally, given the influence of the local microenvironment on immune regulation, we address how CNS-intrinsic signals reshape T cell function to mitigate abnormal immune T cell responses.

Interleukin 22 and its association with neurodegenerative disease activity

It is worth noting that neuroinflammation is well recognized as a symptom of neurodegenerative diseases (NDs). The regulation of neuroinflammation becomes an attractive focus for innovative ND treatment technologies. There is evidence that IL-22 is associated with the development and progression of a wide assortment of NDs. For example, IL-22 can activate glial cells, causing them to generate pro-inflammatory cytokines and encourage lymphocyte infiltration in the brain. IL-22 mRNA is highly expressed in Alzheimer’s disease (AD) patients, and a high expression of IL-22 has also been detected in the brains of patients with other NDs. We examine the role of IL-22 in the development and treatment of NDs in this review, and we believe that IL-22 has therapeutic potential in these diseases.

Therapeutic Effect of IL-21 Blockage by Gene Therapy in Experimental Autoimmune Encephalomyelitis

The pathogenic role of the interleukin 21 (IL-21) in different autoimmune diseases, such as multiple sclerosis (MS), has been extensively studied. However, its pleiotropic nature makes it a cytokine that may exhibit different activity depending on the immunological stage of the disease. In this study, we developed a gene therapy strategy to block the interaction between IL-21 and its receptor (IL-21R) by using adeno-associated vectors (AAV) encoding a new soluble cytokine receptor (sIL21R) protein. We tested this strategy in a murine model of experimental autoimmune encephalomyelitis (EAE), obtaining different clinical effects depending on the time at which the treatment was applied. Although the administration of the treatment during the development of the immune response was counterproductive, the preventive administration of the therapeutic vectors showed a protective effect by reducing the number of animals that developed the disease, as well as an improvement at the histopathological level and a modification of the immunological profile of the animals treated with the AAV8.sIL21R. The beneficial effect of the treatment was also observed when inducing the expression of the therapeutic molecule once the first neurological signs were established in a therapeutic approach with a doxycyline (Dox)-inducible expression system. All these clinical results highlight the pleiotropicity of this cytokine in the different clinical stages and its key role in the EAE immunopathogenesis.

CXCL13 expressed on inflamed cerebral blood vessels recruit IL-21 producing TFH cells to damage neurons following stroke

BACKGROUND

Ischemic stroke is a leading cause of mortality worldwide, largely due to the inflammatory response to brain ischemia during post-stroke reperfusion. Despite ongoing intensive research, there have not been any clinically approved drugs targeting the inflammatory component to stroke. Preclinical studies have identified T cells as pro-inflammatory mediators of ischemic brain damage, yet mechanisms that regulate the infiltration and phenotype of these cells are lacking. Further understanding of how T cells migrate to the ischemic brain and facilitate neuronal death during brain ischemia can reveal novel targets for post-stroke intervention.

METHODS

To identify the population of T cells that produce IL-21 and contribute to stroke, we performed transient middle cerebral artery occlusion (tMCAO) in mice and performed flow cytometry on brain tissue. We also utilized immunohistochemistry in both mouse and human brain sections to identify cell types and inflammatory mediators related to stroke-induced IL-21 signaling. To mechanistically demonstrate our findings, we employed pharmacological inhibitor anti-CXCL13 and performed histological analyses to evaluate its effects on brain infarct damage. Finally, to evaluate cellular mechanisms of stroke, we exposed mouse primary neurons to oxygen glucose deprivation (OGD) conditions with or without IL-21 and measured cell viability, caspase activity and JAK/STAT signaling.

RESULTS

Flow cytometry on brains from mice following tMCAO identified a novel population of cells IL-21 producing CXCR5+ CD4+ ICOS-1+ T follicular helper cells (TFH) in the ischemic brain early after injury. We observed augmented expression of CXCL13 on inflamed brain vascular cells and demonstrated that inhibition of CXCL13 protects mice from tMCAO by restricting the migration and influence of IL-21 producing TFH cells in the ischemic brain. We also illustrate that neurons express IL-21R in the peri-infarct regions of both mice and human stroke tissue in vivo. Lastly, we found that IL-21 acts on mouse primary ischemic neurons to activate the JAK/STAT pathway and induce caspase 3/7-mediated apoptosis in vitro.

CONCLUSION

These findings identify a novel mechanism for how pro-inflammatory T cells are recruited to the ischemic brain to propagate stroke damage and provide a potential new therapeutic target for stroke.

T Cell Help in the Autoreactive Germinal Center

The germinal center serves as a site of B cell selection and affinity maturation, critical processes for productive adaptive immunity. In autoimmune disease tolerance is broken in the germinal center reaction, leading to production of autoreactive B cells that may propagate disease. Follicular T cells are crucial regulators of this process, providing signals necessary for B cell survival in the germinal center. Here we review the emerging roles of follicular T cells in the autoreactive germinal center. Recent advances in immunological techniques have allowed study of the gene expression profiles and repertoire of follicular T cells at unprecedented resolution. These studies provide insight into the potential role follicular T cells play in preventing or facilitating germinal center loss of tolerance. Improved understanding of the mechanisms of T cell help in autoreactive germinal centers provides novel therapeutic targets for diseases of germinal center dysfunction.

Fatty Acid Metabolism and T Cells in Multiple Sclerosis

Cellular metabolic remodeling is intrinsically linked to the development, activation, differentiation, function, and survival of T cells. T cells transition from a catabolic, naïve state to an anabolic effector state upon T cell activation. Subsequently, specialization of T cells into T helper (Th) subsets, including regulatory T cells (Treg), requires fine-tuning of metabolic programs that better support and optimize T cell functions for that particular environment. Increasingly, studies have shown that changes in nutrient availability at both the cellular and organismal level during disease states can alter T cell function, highlighting the importance of better characterizing metabolic-immune axes in both physiological and disease settings. In support of these data, a growing body of evidence is emerging that shows specific lipid species are capable of altering the inflammatory functional phenotypes of T cells. In this review we summarize the metabolic programs shown to support naïve and effector T cells, and those driving Th subsets. We then discuss changes to lipid profiles in patients with multiple sclerosis, and focus on how the presence of specific lipid species can alter cellular metabolism and function of T cells.

Different subpopulations of regulatory T cells in human autoimmune disease, transplantation, and tumor immunity

CD4⁺CD25⁺ regulatory T cells (Tregs), a subpopulation of naturally CD4⁺ T cells that characteristically express transcription factor Forkhead box P3 (FOXP3), play a pivotal role in the maintenance of immune homeostasis and the prevention of autoimmunity. With the development of biological technology, the understanding of plasticity and stability of Tregs has been further developed. Recent studies have suggested that human Tregs are functionally and phenotypically diverse. The functions and mechanisms of different phenotypes of Tregs in different disease settings, such as tumor microenvironment, autoimmune diseases, and transplantation, have gradually become hot spots of immunology research that arouse extensive attention. Among the complex functions, CD4⁺CD25⁺FOXP3⁺ Tregs possess a potent immunosuppressive capacity and can produce various cytokines, such as IL‐2, IL‐10, and TGF‐β, to regulate immune homeostasis. They can alleviate the progression of diseases by resisting inflammatory immune responses, whereas promoting the poor prognosis of diseases by helping cells evade immune surveillance or suppressing effector T cells activity. Therefore, methods for targeting Tregs to regulate their functions in the immune microenvironment, such as depleting them to strengthen tumor immunity or expanding them to treat immunological diseases, need to be developed. Here, we discuss that different subpopulations of Tregs are essential for the development of immunotherapeutic strategies involving Tregs in human diseases.

Long-Term Effects of Alemtuzumab on CD4+ Lymphocytes in Multiple Sclerosis Patients: A 72-Month Follow-Up

Introduction

Alemtuzumab is highly effective in the treatment of patients with relapsing multiple sclerosis (PwRMS) and selectively targets the CD52 antigen, with a consequent profound lymphopenia, particularly of CD4+ T lymphocytes. However, the immunological basis of its long-term efficacy has not been clearly elucidated.

Methods

We followed up 29 alemtuzumab-treated RMS patients over a period of 72 months and studied the immunological reconstitution of their CD4+ T cell subsets by means of phenotypic and functional analysis and through mRNA-related molecule expression, comparing them to healthy subject (HS) values (rate 2:1).

Results

In patients receiving only two-course alemtuzumab, the percentage of CD4+ lymphocytes decreased and returned to basal levels only at month 48. Immune reconstitution of the CD4+ subsets was characterized by a significant increase (p < 0.001) in Treg cell percentage at month 24, when compared to baseline, and was accompanied by restoration of the Treg suppressor function that increased within a range from 2- to 6.5-fold compared to baseline and that persisted through to the end of the follow-up. Furthermore, a significant decrease in self-reactive myelin basic protein-specific Th17 (p < 0.0001) and Th1 (p < 0.05) cells reaching HS values was observed starting from month 12. There was a change in mRNA of cytokines, chemokines, and transcriptional factors related to Th17, Th1, and Treg cell subset changes, consequently suggesting a shift toward immunoregulation and a reduction of T cell recruitment to the central nervous system.

Conclusions

These data provide further insight into the mechanism that could contribute to the long-term 6-year persistence of the clinical effect of alemtuzumab on RMS disease activity.

Impact of IL-21 Gene Polymorphisms (rs2055979) and the Levels of Serum IL-21 on the Risk of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic autoimmune disorder of the central nervous system. Genetic and environmental factors have important roles in the induction, onset, and progression of MS. In this study, the IL-21 genotype (rs2055979) (G/T) in Iraqi MS patients was compared with a healthy control group to investigate the possible association of any particular genotype or allele with multiple sclerosis. This study included 70 patients with relapsing-remitting MS and 50 healthy individuals as control. Following the extraction of genomic DNA, polymerase chain reaction-restriction fragment length polymorphism, the frequencies of genotypes, and alleles were calculated and statistically analyzed. The results of the study revealed a significant reduction in the distribution of the wild homozygous genotype (GG) in MS patients, in comparison to a healthy control group (14.3% vs. 34 %; 0.0129 at P≤0.05; odds ratio [OR] 3.0909, 95% confidence interval [CI]: 1.2704-7.5203). However, MS cases and controls did not differ significantly in neither GT nor TT genotypes, 62.9% (OR 0.6402, 95% CI: 0.3064-1.3374) and 52% (OR 0.5494, 95% CI: 0.2074-1.4557), respectively. The data of allele frequencies in patients and controls showed that the G allele frequencies were 0.46 vs. 0.60 in patients and controls, respectively, while T allele frequencies were 0.54 vs. 0.40 in patients and controls, respectively. The current conclusions indicated that in the study group, the GG genotype of IL-21(rs2055979) could be related to MS.

Sustained immunotolerance in multiple sclerosis after stem cell transplant

Objective

Autologous haematopoietic stem cell transplantation (AHSCT) has the potential to induce sustained periods of disease remission in multiple sclerosis (MS), which is an inflammatory disease of the central nervous system (CNS) characterised by demyelination and axonal degeneration. However, the mechanisms associated with durable treatment responses in MS require further elucidation.

Methods

To characterise the longer term immune reconstitution effects of AHSCT at 24 and 36 months (M) post‐transplant, high‐dimensional immunophenotyping of peripheral blood mononuclear cells from 22 MS patients was performed using two custom‐designed 18‐colour flow cytometry panels.

Results

The higher baseline frequencies of specific pro‐inflammatory immune cells (T‐helper‐17 (Th17) cells, mucosal‐associated invariant T‐cells and CNS‐homing T‐conventional (T‐conv) cells observed in MS patients were decreased post‐AHSCT by 36M. This was accompanied by a post‐AHSCT increase in frequencies and absolute counts of immunoregulatory CD56^hi natural killer cells at 24M and terminally differentiated CD8⁺CD28⁻CD57⁺ cells until 36M. A sustained increase in the proportion of naïve B‐cells, with persistent depletion of memory B‐cells and plasmablasts was observed until 36M. Reconstitution of the B‐cell repertoire was accompanied by a reduction in the frequency of circulating T‐follicular helper cells (cTfh) expressing programmed cell death‐1 (PD1⁺) at 36M. Associations between frequency dynamics and clinical outcomes indicated only responder patients to exhibit a decrease in Th17, CNS‐homing T‐conv and PD1⁺ cTfh pro‐inflammatory subsets at 36M, and an increase in CD39⁺ T‐regulatory cells at 24M.

Interpretation

AHSCT induces substantial recalibration of pro‐inflammatory and immunoregulatory components of the immune system of MS patients for up to 36M post‐transplant.

T-cell surveillance of the human brain in health and multiple sclerosis

Circulating and tissue-resident T cells collaborate in the protection of tissues against harmful infections and malignant transformation but also can instigate autoimmune reactions. Similar roles for T cells in the brain have been less evident due to the compartmentized organization of the central nervous system (CNS). In recent years, beneficial as well as occasional, detrimental effects of T-cell-targeting drugs in people with early multiple sclerosis (MS) have increased interest in T cells patrolling the CNS. Next to studies focusing on T cells in the cerebrospinal fluid, phenotypic characteristics of T cells located in the perivascular space and the meninges as well as in the parenchyma in MS lesions have been reported. We here summarize the current knowledge about T cells infiltrating the healthy and MS brain and argue that understanding the dynamics of physiological CNS surveillance by T cells is likely to improve the understanding of pathological conditions, such as MS.

Follicular T cells are clonally and transcriptionally distinct in B cell-driven mouse autoimmune disease

Pathogenic autoantibodies contribute to tissue damage and clinical decline in autoimmune disease. Follicular T cells are central regulators of germinal centers, although their contribution to autoantibody-mediated disease remains unclear. Here we perform single cell RNA and T cell receptor (TCR) sequencing of follicular T cells in a mouse model of autoantibody-mediated disease, allowing for analyses of paired transcriptomes and unbiased TCRαβ repertoires at single cell resolution. A minority of clonotypes are preferentially shared amongst autoimmune follicular T cells and clonotypic expansion is associated with differential gene signatures in autoimmune disease. Antigen prediction using algorithmic and machine learning approaches indicates convergence towards shared specificities between non-autoimmune and autoimmune follicular T cells. However, differential autoimmune transcriptional signatures are preserved even amongst follicular T cells with shared predicted specificities. These results demonstrate that follicular T cells are phenotypically distinct in B cell-driven autoimmune disease, providing potential therapeutic targets to modulate autoantibody development.

Increased Tc17 cell levels and imbalance of naïve/effector immune response in Parkinson's disease patients in a two-year follow-up: a case control study

BACKGROUND

Neuroinflammation has been proved to play a role in dopaminergic neuronal death in Parkinson's disease (PD). This link highlights the relevance of the immune response in the progression of the disease. However, little is known about the impact of peripheral immune response on the disease. This study is aimed to evaluate how immune cell populations change in untreated PD patients followed-up for 2 years.

METHODS

Thirty-two patients with no previous treatment (PD-0 yr) and twenty-two healthy subjects (controls) were included in the study. PD patients were sampled 1 and 2 years after the start of the treatment. CD4 T cells (naïve/central memory, effector, and activated), CD8 T cells (activated, central memory, effector memory, NKT, Tc1, Tc2, and Tc17), and B cells (activated, plasma, and Lip-AP) were characterized by flow cytometry.

RESULTS

We observed decreased levels of naïve/central memory CD4 and CD8 T cells, Tc1, Tc2, NKT, and plasma cells, and increased levels of effector T cells, activated T cells, and Tc17.

CONCLUSIONS

PD patients treated for 2 years showed an imbalance in the naive/effector immune response. Naïve and effector cell levels were associated with clinical deterioration. These populations are also correlated to aging. On the other hand, higher Tc17 levels suggest an increased inflammatory response, which may impact the progression of the disease. Our results highlight the relevant effect of treatment on the immune response, which could improve our management of the disease.

Altered distributions in circulating follicular helper and follicular regulatory T cells accountable for imbalanced cytokine production in multiple sclerosis

Follicular T helper (Tfh) and regulatory (Tfr) cells are distinct subsets of CD4+ T lymphocytes, regulating humoral immune responses in the germinal center. It is widely accepted that dysregulated Tfh and Tfr cells are associated with autoimmunity. In this study, we evaluated the frequencies of circulating chemokine receptor (CXCR)5+ programmed cell death 1 (PD-1+ ) Tfh (cTfh) and CXCR5+ PD-1+ forkhead box protein 3 (FoxP3+ ) CD25+ Tfr (cTfr) cells, and their corresponding cytokines from the peripheral blood mononuclear cells of 28 patients with relapsing-remitting multiple sclerosis (MS) and 16 age- and sex-matched healthy controls (HC). Subsets of cTfh cells by Th1- and Th17-related surface markers (CXCR3 and CCR6) were also evaluated. We found that the frequency of cTfh cells was significantly higher in MS patients compared to that of HC. Conversely, the frequency of cTfr cells was lower in MS patients than that of HC. Interleukin (IL)-21-producing cTfh cells were significantly increased in MS patients, while IL-10-secreting cTfr cells were lower in MS patients compared to levels in HC. Among cTfh cells, cTfh17.1 cells were the major subtypes that were significantly increased in MS patients compared to HC, with the frequency of IL-21-secreting cells being the highest. These results suggest that an imbalanced distribution of cTfh and cTfr exist in MS patients, which contributes to the reciprocally altered IL-21 and IL-10 production.

Ectopic Lymphoid Follicles in Multiple Sclerosis: Centers for Disease Control?

While the contribution of autoreactive CD4⁺ T cells to the pathogenesis of Multiple Sclerosis (MS) is widely accepted, the advent of B cell-depleting monoclonal antibody (mAb) therapies has shed new light on the complex cellular mechanisms underlying MS pathogenesis. Evidence supports the involvement of B cells in both antibody-dependent and -independent capacities. T cell-dependent B cell responses originate and take shape in germinal centers (GCs), specialized microenvironments that regulate B cell activation and subsequent differentiation into antibody-secreting cells (ASCs) or memory B cells, a process for which CD4⁺ T cells, namely follicular T helper (T_FH) cells, are indispensable. ASCs carry out their effector function primarily via secreted Ig but also through the secretion of both pro- and anti-inflammatory cytokines. Memory B cells, in addition to being capable of rapidly differentiating into ASCs, can function as potent antigen-presenting cells (APCs) to cognate memory CD4⁺ T cells. Aberrant B cell responses are prevented, at least in part, by follicular regulatory T (T_FR) cells, which are key suppressors of GC-derived autoreactive B cell responses through the expression of inhibitory receptors and cytokines, such as CTLA4 and IL-10, respectively. Therefore, GCs represent a critical site of peripheral B cell tolerance, and their dysregulation has been implicated in the pathogenesis of several autoimmune diseases. In MS patients, the presence of GC-like leptomeningeal ectopic lymphoid follicles (eLFs) has prompted their investigation as potential sources of pathogenic B and T cell responses. This hypothesis is supported by elevated levels of CXCL13 and circulating T_FH cells in the cerebrospinal fluid (CSF) of MS patients, both of which are required to initiate and maintain GC reactions. Additionally, eLFs in post-mortem MS patient samples are notably devoid of T_FR cells. The ability of GCs to generate and perpetuate, but also regulate autoreactive B and T cell responses driving MS pathology makes them an attractive target for therapeutic intervention. In this review, we will summarize the evidence from both humans and animal models supporting B cells as drivers of MS, the role of GC-like eLFs in the pathogenesis of MS, and mechanisms controlling GC-derived autoreactive B cell responses in MS.

Correlation between IL-31 and sCD40L plasma levels in Fingolimod-treated patients with Relapsing-Remitting Multiple Sclerosis (RRMS)

INTRODUCTION

Multiple Sclerosis (MS) is a chronic, autoimmune, demyelinating disease of the central nervous system (CNS). Currently, several protocols are described for the different phases of MS. In this longitudinal study, we aim to quantify the concentration of plasma cytokines of MS patients treated with Fingolimod alone or after Glatiramer Acetate (GA) or Interferon-beta (IFN-β), in order to compeer both treatments and describes if it is possible to use them as biomarkers.

OBJECTIVE

Compare the two different types of drug treatment and describes possible immune biomarkers in RRMS patients treated with Fingolimod alone or after GA or IFN-β.

MATERIALS AND METHODS

This is a controlled, non-randomized clinical trial. Plasma concentrations of IL-31, sCD40L and nine others cytokines were evaluated in two groups of patients with a one-year follow-up. Group 1 (n = 12): RRMS patients treated with GA or IFN-β for at least six months before the study who changed therapy to Fingolimod after six months, and Group 2 (n = 12): naïve RRMS patients who started treatment with Fingolimod. We used ANOVA two-way to analyze the cytokines and Spearman coefficient to evaluate the correlation.

RESULTS

Although Group 2 started with a greater number of relapses per disease duration, Fingolimod treatment was effective in decreasing this parameter, as well as EDSS over 12 months. However, the treatment with GA or IFN-β on Group 1 showed a tendency to increase the number of relapses after 6 months of follow-up, which decrease when the therapy was changed to Fingolimod. After the evaluation of 11 cytokines in one year, we found that IL-31 and sCD40L were the biomarkers that demonstrated a more difference when compared to the classical ones, following the clinical pattern over the treatment period.

CONCLUSIONS

Our study describes the existence of two promising plasmatic biomarkers (IL-31 and sCD40L), which reduced plasmatic levels in RRMS patients followed the treatment time of Fingolimod, despite that more studies are needed to prove their efficiency.

Upregulation of interleukin (IL)-31, a cytokine producing CXCR1 peripheral immune cells, contributes to the immune abnormalities of autism spectrum disorder

Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders characterized by communication deficits, impaired social interactions, and restricted stereotypical behaviors. Several immune cells are associated with immune dysfunction in ASD; however, IL-31 has not been explored in ASD. This study aims to investigate the role of inflammatory cytokines and transcription factors of the CXCR1 cells in children with ASD. In the current study, we investigated the cytokines and transcription factors produced by CXCR1⁺ cells (IL-31, IL-9, IL-21R, IL-21, NF-κB p65, RORγT, STAT1, and FoxP3) in peripheral blood mononuclear cells (PBMCs), from children with ASD and typically developing (TD) control children, using flow cytometric analysis. In addition, we measured mRNA and protein expression levels of IL-31 using quantitative real-time PCR and western blot analyses in PBMCs. In our study, children with ASD had increased CXCR1⁺IL-31⁺, CXCR1⁺IL-9⁺, CXCR1⁺IL-21R⁺, CXCR1⁺IL-21⁺, CXCR1⁺NF-κB⁺ p65, CXCR1⁺RORγT⁺, and CXCR1⁺STAT1⁺, and decreased CXCR1⁺FoxP3⁺ cells as compared with cells from the TD control samples. Similarly, children with ASD showed increased IL-31 mRNA and protein expression levels as compared to those of TD control samples. Our results suggest that upregulated production of inflammatory cytokines and transcription factors in CXCR1⁺ cells cause immunological imbalance in children with ASD. Therefore, attenuation of inflammatory cytokines/mediators and transcription factors could have a therapeutic potential in the treatment of ASD.

Effects of anesthetic method on inflammatory response in patients with Parkinson's disease: a randomized controlled study

BACKGROUND

The pathogenesis of Parkinson's disease (PD) involves degeneration of dopaminergic neurons, which is influenced by innate and adaptive immunity. IL-17 is a characteristic cytokine secreted by Th17 cells, which acts as a powerful stimulator of neutrophil migration and infiltration and promotes the secretion of inflammatory cytokines. General anesthesia and surgical stress induce immune and inflammatory responses that activate the immunosuppressive mechanism in the perioperative period. The present study investigated changes in levels of inflammatory cytokines, such as IL-17, IL-1β, and TNF-α, in patients with PD undergoing general anesthesia with inhalational anesthetics or TIVA.

METHODS

Adult patients, aged 40-75 years, scheduled for cerebral stimulator implantation were enrolled. Upon arrival at the operating theater, patients were allocated to the inhalational (I) or TIVA (T) group using block randomization. In group I, anesthesia was induced by tracheal intubation 1-2 min after intravenous administration of propofol (1-2 mg/kg) and rocuronium (0.6-1 mg/kg). Thereafter, anesthesia was maintained with 1-2 vol% sevoflurane, 0.01-0.2 μg/kg/min remifentanil, and O₂/air (FiO₂ 0.4). In group T, propofol (3-6 μg/mL), remifentanil (2-6 ng/mL), and rocuronium (0.6-1 mg/kg) were administered using target controlled infusion (TCI) for induction of anesthesia. Blood samples were obtained preoperatively (T0), 2 h after induction of anesthesia (T1), and 24 h after surgery (T2). IL-17, IL-1β, and TNF-α levels were evaluated by ELISA.

RESULTS

Serum levels of IL-17 were elevated at T2 in group I compared to group T but the difference was not statistically significant. IL-1β tended to be greater in group I compared to group T, but the differences were not significant. TNF-α was slightly higher at all time points in group T and showed a tendency to increase at T2 in both groups, but this was not statistically significant.

CONCLUSIONS

TIVA may be useful for inhibiting neuroinflammation by inhibiting the increase in serum levels of IL-17 24 h after implantation surgery. Serum IL-17 level may be used as a biomarker for PD progression.

TRIAL REGISTRATION

Clinical Research Information Service of Korea National Institute of Health (CRIS) Identification number: KCT0002061 . Registered 25 October 2019 - Retrospectively registered, https://cris.nih.go.kr/cris/search/search_result_st01.jsp?seq=15125.

Interleukin-17 in Chronic Inflammatory Neurological Diseases

A critical role for IL-17, a cytokine produced by T helper 17 (Th17) cells, has been indicated in the pathogenesis of chronic inflammatory and autoimmune diseases. A positive effect of blockade of IL-17 secreted by autoreactive T cells has been shown in various inflammatory diseases. Several cytokines, whose production is affected by environmental factors, control Th17 differentiation and its maintenance in tissues during chronic inflammation. The roles of IL-17 in the pathogenesis of chronic neuroinflammatory conditions, multiple sclerosis (MS), experimental autoimmune encephalomyelitis (EAE), Alzheimer's disease, and ischemic brain injury are reviewed here. The role of environmental stimuli in Th17 differentiation is also summarized, highlighting the role of viral infection in the regulation of pathogenic T helper cells in EAE.

Imbalance in T follicular helper cells producing IL-17 promotes pro-inflammatory responses in MuSK antibody positive myasthenia gravis

A detailed understanding of the role of Tfh cells in MuSK-antibody positive myasthenia gravis (MuSK-MG) is lacking. We characterized phenotype and function of Tfh cells in MuSK-MG patients and controls. We found similar overall Tfh and follicular regulatory (Tfr) T cell frequencies in MuSK-MG and healthy controls, but MuSK-MG patients exhibited higher frequencies of Tfh17 cells and a higher ratio of Tfh:Tfr cells. These results suggest imbalanced Tfh cell regulation, further supported by increased frequencies of CD4 T cells co-producing IL-21/IL-17 and IL-17/IFN-γ, and increased Tfh-supported IgG production. These results support a role for Tfh cell dysregulation in MuSK-MG immunopathology.

B and T Cells Driving Multiple Sclerosis: Identity, Mechanisms and Potential Triggers

Historically, multiple sclerosis (MS) has been viewed as being primarily driven by T cells. However, the effective use of anti-CD20 treatment now also reveals an important role for B cells in MS patients. The results from this treatment put forward T-cell activation rather than antibody production by B cells as a driving force behind MS. The main question of how their interaction provokes both B and T cells to infiltrate the CNS and cause local pathology remains to be answered. In this review, we highlight key pathogenic events involving B and T cells that most likely contribute to the pathogenesis of MS. These include (1) peripheral escape of B cells from T cell-mediated control, (2) interaction of pathogenic B and T cells in secondary lymph nodes, and (3) reactivation of B and T cells accumulating in the CNS. We will focus on the functional programs of CNS-infiltrating lymphocyte subsets in MS patients and discuss how these are defined by mechanisms such as antigen presentation, co-stimulation and cytokine production in the periphery. Furthermore, the potential impact of genetic variants and viral triggers on candidate subsets will be debated in the context of MS.

Interleukin-9 regulates macrophage activation in the progressive multiple sclerosis brain

Background

Multiple sclerosis (MS) is an immune-mediated, chronic inflammatory, and demyelinating disease of the central nervous system (CNS). Several cytokines are thought to be involved in the regulation of MS pathogenesis. We recently identified interleukin (IL)-9 as a cytokine reducing inflammation and protecting from neurodegeneration in relapsing–remitting MS patients. However, the expression of IL-9 in CNS, and the mechanisms underlying the effect of IL-9 on CNS infiltrating immune cells have never been investigated.

Methods

To address this question, we first analyzed the expression levels of IL-9 in post-mortem cerebrospinal fluid of MS patients and the in situ expression of IL-9 in post-mortem MS brain samples by immunohistochemistry. A complementary investigation focused on identifying which immune cells express IL-9 receptor (IL-9R) by flow cytometry, western blot, and immunohistochemistry. Finally, we explored the effect of IL-9 on IL-9-responsive cells, analyzing the induced signaling pathways and functional properties.

Results

We found that macrophages, microglia, and CD4 T lymphocytes were the cells expressing the highest levels of IL-9 in the MS brain. Of the immune cells circulating in the blood, monocytes/macrophages were the most responsive to IL-9. We validated the expression of IL-9R by macrophages/microglia in post-mortem brain sections of MS patients. IL-9 induced activation of signal transducer and activator of transcription (STAT)1, STAT3, and STAT5 and reduced the expression of activation markers, such as CD45, CD14, CD68, and CD11b in inflammatory macrophages stimulated in vitro with lipopolysaccharide and interferon (IFN)-γ. Similarly, in situ the number of activated CD68⁺ macrophages was significantly reduced in areas with high levels of IL-9. Moreover, in the same conditions, IL-9 increased the secretion of the anti-inflammatory cytokine, transforming growth factor (TGF)-β.

Conclusions

These results reveal a new cytokine expressed in the CNS, with a role in the context of MS. We have demonstrated that IL-9 and its receptor are both expressed in CNS. Moreover, we found that IL-9 decreases the activation state and promotes the anti-inflammatory properties of human macrophages. This mechanism may contribute to the beneficial effects of IL-9 that are observed in MS, and may be therapeutically potentiated by modulating IL-9 expression in MS.

IgG3 + B cells are associated with the development of multiple sclerosis

OBJECTIVES

Disease-modifying therapies (DMTs) targeting B cells are amongst the most effective for preventing multiple sclerosis (MS) progression. IgG3 antibodies and their uncharacterised B-cell clones are predicted to play a pathogenic role in MS. Identifying subsets of IgG3 + B cells involved in MS progression could improve diagnosis, could inform timely disease intervention and may lead to new DMTs that target B cells more specifically.

METHODS

We designed a 31-parameter B-cell-focused mass cytometry panel to interrogate the role of peripheral blood IgG3 + B cells in MS progression of two different patient cohorts: one to investigate the B-cell subsets involved in conversion from clinically isolated syndrome (CIS) to MS; and another to compare MS patients with inactive or active stages of disease. Each independent cohort included a group of non-MS controls.

RESULTS

Nine distinct CD20+IgD-IgG3 + B-cell subsets were identified. Significant changes in the proportion of CD21+CD24+CD27-CD38- and CD27+CD38hiCD71hi memory B-cell subsets correlated with changes in serum IgG3 levels and time to conversion from CIS to MS. The same CD38- double-negative B-cell subset was significantly elevated in MS patients with active forms of the disease. A third CD21+CD24+CD27+CD38- subset was elevated in patients with active MS, whilst narrowband UVB significantly reduced the proportion of this switched-memory B-cell subset.

CONCLUSION

We have identified previously uncharacterised subsets of IgG3 + B cells and shown them to correlate with autoimmune attacks on the central nervous system (CNS). These results highlight the potential for therapies that specifically target IgG3 + B cells to impact MS progression.

Chronic Inflammatory Lameness Increases Cytokine Concentration in the Spinal Cord of Dairy Cows

Lameness in dairy cows is an extremely painful multifactorial condition that affects the welfare of animals and economically impacts the dairy industry worldwide. The aim of this study was to determine the profile of cytokines in the spinal cord dorsal horn of dairy cows with painful chronic inflammatory lameness. Concentrations of 10 cytokines were measured in the spinal cord of seven adult dairy cows with chronic lameness and seven adult dairy cows with no lameness. In all cows lameness was evaluated using a mobility scoring system and registered accordingly. Immediately after euthanasia the spinal cord was removed and 20 cm of lumbar segments (L2–L5) were obtained. After dorsal horn removal and processing, cytokine quantification of tumor necrosis factor-alpha (TNF-α), interleukin-1alpha (IL-1α), interleukin 13 (IL-13), chemokine-10 (CXCL10/IP-10), chemokine-9 (CXCL9/MIG), interferon-alpha (IFN-α), interferon-gamma (IFN-γ), interleukin-21 (IL-21), interleukin-36ra (IL-36ra), and macrophage inflammatory protein-1 beta (MIP-1β) was performed using a multiplex array. Lame cows had higher concentrations of TNF-α, IL-1-α, IL-13, CXCL10, CXCL9, IFN-α, and IFN-γ in their dorsal horn compared to non-lame cows, while IL-21 concentration was decreased. No differences in IL-36ra and MIP-1β concentrations between lame and non-lame cows were observed. Painful chronic inflammation of the hoof in dairy cows leads to a marked increase in cytokine concentration in the dorsal horn of the spinal cord, which could represent a state of neuroinflammation of the Central Nervous System (CNS).

Inhibition of tyrosine kinase signaling by tyrphostin AG126 downregulates the IL-21/IL-21R and JAK/STAT pathway in the BTBR mouse model of autism

Autism spectrum disorder (ASD) comprises a broad range of neurodevelopmental disorders that are associated with deficits in social interaction and communication. The tyrosine kinase inhibitor tyrphostin AG126 represents a promising therapeutic agent for several neuroinflammatory disorders. There are currently no treatments available that can improve ASD and we previously showed that AG126 treatment exerts beneficial effects on BTBR T⁺ Itpr3^tf/J (BTBR) mice, a model for autism that shows the core features of ASD; however, the immunological mechanisms and molecular targets associated with this effect were previously unclear. This study was undertaken to delineate the neuroprotective effect of AG126 on BTBR mice. Here, using this mouse model, we investigated the effects of AG126 administration on IL-21R, IL-21, IL-22, TNF-α, NOS2, STAT3, IL-27, and Foxp3 production by CD8⁺ T cells in the spleen by flow cytometry. We further explored the mRNA and protein expression of IL-21, IL-22, IL-1β, TNF-α, NOS2, JAK1, STAT3, IL-27, and Foxp3 in brain tissue by RT-PCR, and western blotting. We found that BTBR mice treated with AG126 exhibited significant decreases in IL-21R-, IL-21-, IL-22-, TNF-α-, NOS2-, STAT3-producing, and increases in IL-27- and Foxp3-producing, CD8⁺ T cells. Our results further demonstrated that AG126 treatment effectively decreased IL-21, IL-22, IL-1β, TNF-α, NOS2, JAK1, and STAT3, and increased IL-27 and Foxp3 mRNA and protein expression in brain tissues. Our findings suggest that AG126 elicits a neuroprotective response through downregulation of the IL-21/IL-21R and JAK/STAT pathway in BTBR mice, which could represent a promising novel therapeutic target for ASD treatment.

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.

Th17/Treg cells imbalance and their related cytokines (IL-17, IL-10 and TGF-β) in children with autism spectrum disorder

We aimed in this study to investigate a possible involvement of Th17/Treg cells imbalance in autism spectrum disorders (ASD). Using flowcytometry to determine circulating Th17 and Treg cells percentages, RT- PCR and ELISA for cytokine expression, we demonstrated that Th17/Treg balance in ASD children was significantly skewed toward a Th17 response compared to their control. Th17 cells and the ratio of Th17/Treg cells had a significantly positive correlation with disease severity whereas Treg cells had a negative correlation. The imbalance of Th17, Treg cells and their related cytokines may play a vital role in the progression of the disease.

Paradoxical role of Breg-inducing cytokines in autoimmune diseases

Regulatory B cells (Breg) are crucial immunoregulators that maintain peripheral tolerance and suppress inflammatory autoimmune responses. In recent years, our understanding on the nature and mechanism of action of Bregs has revealed the important role of cytokines in promoting the regulatory properties of this unique B cell subset, both in animal and human models. In this review, we compiled the cytokines that have been reported by multiple studies to induce the expansion of Breg. The Breg-inducing cytokines which are currently known include IL-21, IL-6, IL1β, IFNα, IL-33, IL-35, BAFF and APRIL. As cytokines are also known to play a pivotal role in the pathogenesis of autoimmune diseases, in parallel we reviewed the pattern of expression of the Breg-inducing cytokines in Systemic Lupus Erythematosus (SLE), Rheumatoid Arthritis (RA), Inflammatory Bowel Diseases (IBD) and Multiple Sclerosis (MS). We show here that Breg-inducing cytokines are commonly implicated in these inflammatory diseases where they typically have a higher expression than in healthy individuals, suggesting their paradoxical nature. Interestingly, despite the general overexpression of Breg-inducing cytokines, it is known that Breg cells are often numerically or functionally impaired in various autoimmune conditions. Considering these alterations, we explored the possible parameters that may influence the function of Breg-inducing cytokines in exhibiting either their regulatory or pro-inflammatory properties in the context of autoimmune conditions.

IL-21 Induces an Imbalance of Th17/Treg Cells in Moderate-to-Severe Plaque Psoriasis Patients

Background: Psoriasis is a chronic immune-mediated inflammatory skin disease, with over-activated interleukin (IL)-17-producing CD4⁺ T cells (Th17) and repressed regulatory T (Treg) cells. IL-21 is a Th17-related cytokine and plays an important role in the pathogenesis of psoriasis. However, the mechanism by which IL-21 affects the pathogenic progress of psoriasis remains poorly understood.

Methods: IL-21 and IL-21 receptor (IL-21R) expression in normal and psoriatic lesional skin were determined by immumohistochemical staining, immunofluorescence staining, and western blotting. The levels of IL-21, IL-17A, and IL-22 in the culture supernatants were measured by enzyme-linked immunosorbent assay (ELISA). The level of IL-10 in the culture supernatants was measured by cytometric bead array (CBA). The mRNA expression levels were assessed by quantitative polymerase chain reaction (qPCR). CD4⁺ T cells were isolated from the peripheral blood mononuclear cells (PBMCs) from the psoriasis patients and healthy individuals and then treated with or without IL-21 for 3 days. The proportions of Th17 and Treg cells were determined by flow cytometric analysis.

Results: IL-21 and IL-21R were highly expressed in the lesional skin and peripheral blood of psoriasis patients. IL-21 promoted CD4⁺ T cells proliferation and Th17 cells differentiation and inhibiting Treg cells differentiation by upregulating RORγt expression and downregulating Foxp3 expression, with increased expression and secretion of IL-17A and IL-22. The proportion of Treg cells was negatively correlated with that of Th17 cells in psoriasis patients.

Conclusion: Our results suggest that IL-21 may promote psoriatic inflammation by inducing imbalance in Th17 and Treg cell populations.

Distinct Expression of Inflammatory Features in T Helper 17 Cells from Multiple Sclerosis Patients

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). T helper (Th) 17 lymphocytes play a role in the pathogenesis of MS. Indeed, Th17 cells are abundant in the cerebrospinal fluid and peripheral blood of MS patients and promote pathogenesis in the mouse model of MS. To gain insight into the function of Th17 cells in MS, we tested whether Th17 cells polarized from naïve CD4 T cells of healthy donors and MS patients display different features. To this end, we analysed several parameters that typify the Th17 profile during the differentiation process of naïve CD4 T cells obtained from relapsing-remitting (RR)-MS patients (n = 31) and healthy donors (HD) (n = 28). Analysis of an array of cytokines produced by Th17 cells revealed that expression of interleukin (IL)-21, tumour necrosis factor (TNF)-β, IL-2 and IL-1R1 is significantly increased in Th17 cells derived from MS patients compared to healthy donor-derived cells. Interestingly, IL-1R1 expression is also increased in Th17 cells circulating in the blood of MS patients compared to healthy donors. Since IL-2, IL-21, TNF-β, and IL-1R1 play a crucial role in the activation of immune cells, our data indicate that high expression of these molecules in Th17 cells from MS patients could be related to their high inflammatory status.

Immune system and new avenues in Parkinson’s disease research and treatment

Parkinson’s disease (PD) is a progressive neurological disorder characterized by degeneration of dopaminergic neurons in the substantia nigra. However, although 200 years have now passed since the primary clinical description of PD by James Parkinson, the etiology and mechanisms of neuronal loss in this disease are still not fully understood. In addition to genetic and environmental factors, activation of immunologic responses seems to have a crucial role in PD pathology. Intraneuronal accumulation of α-synuclein (α-Syn), as the main pathological hallmark of PD, potentially mediates initiation of the autoimmune and inflammatory events through, possibly, auto-reactive T cells. While current therapeutic regimens are mainly used to symptomatically suppress PD signs, application of the disease-modifying therapies including immunomodulatory strategies may slow down the progressive neurodegeneration process of PD. The aim of this review is to summarize knowledge regarding previous studies on the relationships between autoimmune reactions and PD pathology as well as to discuss current opportunities for immunomodulatory therapy.

Dysregulation of the expression of HLA-DR, costimulatory molecule, and chemokine receptors on immune cells in children with autism

Autism spectrum disorder (ASD) is a heterogeneous disorder diagnosed based on the severity of abnormalities in social skills. Several studies have acknowledged the presence of abnormal immune functions among individuals diagnosed with ASD. HLA-DR (human leukocyte antigen-antigen D related) has been shown to play a significant role in several inflammatory and neurological disorders; however, the role of HLA-DR signaling in ASD has not yet been fully clarified. In this study, we investigated the role of HLA-DR signaling in children with ASD. Flow cytometric analysis, using peripheral blood mononuclear cells (PBMCs), revealed the numbers of CD4⁺, CD8⁺, CD28⁺, CXCR4⁺, and CCR7⁺ expressing HLA-DR cells in typically developing (TD) controls and children with ASD. We also determined the numbers of IFN-γ⁺, IL-21⁺, and Foxp3⁺ expressing HLA-DR cells in TD controls and in children with ASD using PBMCs. We observed mRNA and protein expression levels of HLA-DR by RT-PCR and western blotting analysis. Our results revealed that children with ASD had significantly increased numbers of HLA-DR⁺CD4⁺, HLA-DR⁺CD8⁺, CD28⁺HLA-DR⁺, HLA-DR⁺CXCR4⁺, HLA-DR⁺CCR7⁺ cells compared with TD controls. We found that children with ASD showed increased HLA-DR⁺IFN-γ⁺ and HLA-DR⁺IL-21⁺ and decreased HLA-DR⁺Foxp3⁺ expression levels compared with TD controls. Furthermore, children with ASD showed higher HLA-DR mRNA and protein expression levels compared with TD controls. These results indicated that HLA-DR could play an essential role in the immune abnormalities associated with ASD.

Emerging Role of Follicular T Helper Cells in Multiple Sclerosis and Experimental Autoimmune Encephalomyelitis

Multiple sclerosis (MS) is an autoimmune disorder where both T cells and B cells are implicated in pathology. However, it remains unclear how these two distinct populations cooperate to drive disease. There is ample evidence from studies in both MS patients and mouse models that Th17, B cells, and follicular T helper (TFH) cells contribute to disease. This review article describes the literature that identifies mechanisms by which Th17, TFH, and B cells cooperatively drive disease activity in MS and experimental autoimmune encephalomyelitis (EAE). The curation of this literature has identified that central nervous system (CNS) infiltrating TFH cells act with TH17 cell to contribute to an inflammatory B cell response in neuroinflammation. This demonstrates that TFH cells and their products are promising targets for therapies in MS.

T Cells That Help B Cells in Chronically Inflamed Tissues

Chronically inflamed tissues commonly accrue lymphocyte aggregates that facilitate local T cell-B cell interactions. These aggregates can range from small, loosely arranged lymphocyte clusters to large, organized ectopic lymphoid structures. In some cases, ectopic lymphoid structures develop germinal centers that house prototypical T follicular helper (Tfh) cells with high expression of Bcl6, CXCR5, PD-1, and ICOS. However, in many chronically inflamed tissues, the T cells that interact with B cells show substantial differences from Tfh cells in their surface phenotypes, migratory capacity, and transcriptional regulation. This review discusses observations from multiple diseases and models in which tissue-infiltrating T cells produce factors associated with B cell help, including IL-21 and the B cell chemoattractant CXCL13, yet vary dramatically in their resemblance to Tfh cells. Particular attention is given to the PD-1^hi CXCR5⁻ Bcl6^low T peripheral helper (Tph) cell population in rheumatoid arthritis, which infiltrates inflamed synovium through expression of chemokine receptors such as CCR2 and augments synovial B cell responses via CXCL13 and IL-21. The factors that regulate CD4⁺ T cell production of CXCL13 and IL-21 in these settings are also discussed. Understanding the range of T cell populations that can provide help to B cells within chronically inflamed tissues is essential to recognize these cells in diverse inflammatory conditions and to optimize either broad or selective therapeutic targeting of B cell-helper T cells.

Downregulation in Helios transcription factor signaling is associated with immune dysfunction in blood leukocytes of autistic children

Autism spectrum disorder (ASD) is a complex heterogeneous neurodevelopmental disorder in which immunological imbalance has been suggested to be a major etiological component. Helios, a transcription factor, has been studied extensively in the context of human T cell regulation in health and disease, yet the role of Helios signaling has not been examined in children with ASD. In the present study, we investigated the production of Helios in CD4⁺, CD8⁺, and TIM-3⁺, CXCR3⁺ cells in typically developing (TD) controls and children with ASD and in peripheral blood mononuclear cells (PBMCs). We assayed the production of IFN-γ⁺Helios⁺, IL-21⁺Helios⁺, T-bet⁺Helios⁺, and Foxp3⁺Helios⁺ cells, and determined Helios mRNA and protein expression levels in PBMCs, in TD controls and children with ASD. Our results revealed that children with ASD had lower numbers of CD4⁺Helios⁺ CD8⁺Helios⁺, TIM-3⁺Helios⁺, and CXCR3⁺Helios⁺ cells as compared to TD controls. Our results also showed that children with ASD had decreased IFN-γ⁺Helios⁺, IL-21⁺Helios⁺, T-bet⁺Helios⁺, and Helios⁺Foxp3⁺ production compared to that in TD controls. Moreover, our results indicated that children with ASD had lower Helios mRNA and protein expression levels compared to those in TD controls. These results suggest that the Helios transcription factor may be critical to immune alterations in children with ASD. Therefore, our results suggest that targeting Helios signaling might offer a strategy for developing ASD therapies.

Psychoneuroimmunology and immunopsychiatry of zebrafish

Despite the high prevalence of neural and immune disorders, their etiology and molecular mechanisms remain poorly understood. As the zebrafish (Danio rerio) is increasingly utilized as a powerful model organism in biomedical research, mounting evidence suggests these fish as a useful tool to study neural and immune mechanisms and their interplay. Here, we discuss zebrafish neuro-immune mechanisms and their pharmacological and genetic modulation, the effect of stress on cytokines, as well as relevant models of microbiota-brain interplay. As many human brain diseases are based on complex interplay between the neural and the immune system, here we discuss zebrafish models, as well as recent successes and challenges, in this rapidly expanding field. We particularly emphasize the growing utility of zebrafish models in translational immunopsychiatry research, as they improve our understanding of pathogenetic neuro-immune interactions, thereby fostering future discovery of potential therapeutic agents.

Upregulation of Interleukin 21 and Interleukin 21 Receptor in Patients with Dermatomyositis and Polymyositis

Background:

The immunopathologic mechanism underlying dermatomyositis (DM) and polymyositis (PM) remains poorly understood. Many cytokines play a pathogenic role in DM and PM. Interleukin 21 (IL-21) has a pleiotropic effect on inflammation regulation. This study aimed to detect the serum IL-21 level and investigate the expression of IL-21 and IL-21 receptor (IL-21R) in muscle tissues of patients with DM and PM.

Methods:

Biopsied muscle samples were obtained from 11 patients with DM, 12 with PM, and six controls; mRNA levels of IL-21 and IL-21R were analyzed by real-time quantitative reverse transcription-polymerase chain reaction; and immunohistochemical staining was used to evaluate the protein expression of IL-21 and IL-21R. Serum samples were obtained from 36 patients with DM, 19 with PM, and 20 healthy controls. The serum IL-21 level was detected by enzyme-linked immunosorbent assay.

Results:

The expression of IL-21 was upregulated in patients with DM and PM. The IL-21 mRNA level was significantly increased in muscle tissues of patients with DM and PM (DM vs. control, P = 0.001; PM vs. control, P = 0.001), whereas IL-21R mRNA level in patients with DM/PM was not statistically different from that of healthy controls. Immunohistochemical staining showed both IL-21 and IL-21R were significantly expressed in the inflammatory cells in muscle tissues of patients with DM and PM. The serum IL-21 level was also significantly higher in patients with DM/PM than in controls (DM vs. control, 49.12 [45.28, 60.07] pg/ml vs. 42.54 [38.69, 48.85] pg/ml, P = 0.001; PM vs. control, 50.77 [44.19, 60.62] pg/ml vs. 42.54 [38.69, 48.85] pg/ml, P = 0.005).

Conclusions:

IL-21 expression is upregulated in patients with DM and PM in both muscle tissue and serum. In addition, IL-21R protein is highly expressed in affected muscle tissues of patients with DM and PM. IL-21 may play a pathogenic role through IL-21R in patients with DM and PM.

Immunophenotypic characterization of CSF B cells in virus-associated neuroinflammatory diseases

Intrathecal antibody synthesis is a well-documented phenomenon in infectious neurological diseases as well as in demyelinating diseases, but little is known about the role of B cells in the central nervous systems. We examined B cell and T cell immunophenotypes in CSF of patients with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) compared to healthy normal donors and subjects with the other chronic virus infection and/or neuroinflammatory diseases including HIV infection, multiple sclerosis (MS) and progressive multifocal leukoencephalopathy. Antibody secreting B cells (ASCs) were elevated in HAM/TSP patients, which was significantly correlated with intrathecal HTLV-1-specific antibody responses. High frequency of ASCs was also detected in patients with relapsing-remitting multiple sclerosis (RRMS). While RRMS patients showed significant correlations between ASCs and memory follicular helper CD4+ T cells, CD4+CD25+ T cells were elevated in HAM/TSP patients, which were significantly correlated with ASCs and HTLV-1 proviral load. These results highlight the importance of the B cell compartment and the associated inflammatory milieu in HAM/TSP patients where virus-specific antibody production may be required to control viral persistence and/or may be associated with disease development.