Circulating CCR7+ICOS+ Memory T Follicular Helper Cells in Patients with Multiple Sclerosis

Transcriptome profile analysis in spinal cord injury rats with transplantation of menstrual blood-derived stem cells

Introduction

Menstrual blood-derived stem cells (MenSCs) are vital in treating many degenerative and traumatic disorders. However, the underlying molecular mechanisms remain obscure in MenSCs-treating spinal cord injury (SCI) rats.

Methods

MenSCs were adopted into the injured sites of rat spinal cords at day 7 post surgery and the tissues were harvested for total RNA sequencing analysis at day 21 after surgery to investigate the expression patterns of RNAs. The differentially expressed genes (DEGs) were analyzed with volcano and heatmap plot. DEGs were sequentially analyzed by weighted gene co-expression network, functional enrichment, and competitive endogenous RNAs (ceRNA) network analysis. Next, expression of selected miRNAs, lncRNAs, circRNAs and mRNAs were validated by quantitative real-time polymerase chain reaction (qRT-PCR). Bioinformatics packages and extra databases were enrolled to scoop the genes functions and their interaction relationships.

Results

A total of 89 lncRNAs, 65 circRNAs, 120 miRNAs and 422 mRNAs were significantly upregulated and 65 lncRNAs, 72 circRNAs, 74 miRNAs, and 190 mRNAs were significantly downregulated in the MenSCs treated rats compared to SCI ones. Current investigation revealed that MenSCs treatment improve the recovery of the injured rats and the most significantly involved pathways in SCI regeneration were cell adhesion molecules, nature killer cell mediated cytotoxicity, primary immunodeficiency, chemokine signaling pathway, T cell receptor signaling pathway and B cell receptor signaling pathway. Moreover, the lncRNA-miRNA-mRNA and circRNA-miRNA-mRNA ceRNA network of SCI was constructed. Finally, the protein-protein interaction (PPI) network was constructed using the top 100 DE mRNAs. The constructed PPI network included 47 nodes and 70 edges.

Discussion

In summary, the above results revealed the expression profile and potential functions of differentially expressed (DE) RNAs in the injured spinal cords of rats in the MenSCs-treated and SCI groups, and this study may provide new clues to understand the mechanisms of MenSCs in treating SCI.

Imbalance of Circulating Follicular Regulatory and Follicular Helper T Cell Subpopulations Is Associated with Disease Progression and Serum CYFRA 21-1 Levels in Patients with Non-small Cell Lung Cancer

OBJECTIVE

This study aimed to investigate the changes of follicular helper T (TFH) and follicular regulatory T (TFR) cell subpopulations in patients with non-small cell lung cancer (NSCLC) and their significance.

METHODS

Peripheral blood was collected from 58 NSCLC patients at different stages and 38 healthy controls. Flow cytometry was used to detect TFH cell subpopulation based on programmed death 1 (PD-1) and inducible co-stimulator (ICOS), and TFR cell subpopulation based on cluster determinant 45RA (CD45RA) and forkhead box protein P3 (FoxP3). The levels of interleukin-10 (IL-10), interleukin-17a (IL-17a), interleukin-21 (IL-21), and transforming growth factor-β (TGF-β) in the plasma were measured, and changes in circulating B cell subsets and plasma IgG levels were also analyzed. The correlation between serum cytokeratin fragment antigen 21-1 (CYFRA 21-1) levels and TFH, TFR, or B cell subpopulations was further explored.

RESULTS

The TFR/TFH ratio increased significantly in NSCLC patients. The CD45RA+FoxP3int TFR subsets were increased, with their proportions increasing in stages II to III and decreasing in stage IV. PD-1+ICOS+TFH cells showed a downward trend with increasing stages. Plasma IL-21 and TGF-β concentrations were increased in NSCLC patients compared with healthy controls. Plasmablasts, plasma IgG levels, and CD45RA+FoxP3int TFR cells showed similar trends. TFH numbers and plasmablasts were positively correlated with CYFRA 21-1 in stages I-III and negatively correlated with CYFRA 21-1 in stage IV.

CONCLUSION

Circulating TFH and TFR cell subpopulations and plasmablasts dynamically change in different stages of NSCLC, which is associated with serum CYFRA 21-1 levels and reflects disease progression.

B cell depletion attenuates CD27 signaling of T helper cells in multiple sclerosis

Multiple sclerosis is a chronic inflammatory disease of the central nervous system. Whereas T cells are likely the main drivers of disease development, the striking efficacy of B cell-depleting therapies (BCDTs) underscore B cells' involvement in disease progression. How B cells contribute to multiple sclerosis (MS) pathogenesis-and consequently the precise mechanism of action of BCDTs-remains elusive. Here, we analyze the impact of BCDTs on the immune landscape in patients with MS using high-dimensional single-cell immunophenotyping. Algorithm-guided analysis reveals a decrease in circulating T follicular helper-like (Tfh-like) cells alongside increases in CD27 expression in memory T helper cells and Tfh-like cells. Elevated CD27 indicates disrupted CD27/CD70 signaling, as sustained CD27 activation in T cells leads to its cleavage. Immunohistological analysis shows CD70-expressing B cells at MS lesion sites. These results suggest that the efficacy of BCDTs may partly hinge upon the disruption of Th cell and B cell interactions.

T cells in health and disease

T cells are crucial for immune functions to maintain health and prevent disease. T cell development occurs in a stepwise process in the thymus and mainly generates CD4⁺ and CD8⁺ T cell subsets. Upon antigen stimulation, naïve T cells differentiate into CD4⁺ helper and CD8⁺ cytotoxic effector and memory cells, mediating direct killing, diverse immune regulatory function, and long-term protection. In response to acute and chronic infections and tumors, T cells adopt distinct differentiation trajectories and develop into a range of heterogeneous populations with various phenotype, differentiation potential, and functionality under precise and elaborate regulations of transcriptional and epigenetic programs. Abnormal T-cell immunity can initiate and promote the pathogenesis of autoimmune diseases. In this review, we summarize the current understanding of T cell development, CD4⁺ and CD8⁺ T cell classification, and differentiation in physiological settings. We further elaborate the heterogeneity, differentiation, functionality, and regulation network of CD4⁺ and CD8⁺ T cells in infectious disease, chronic infection and tumor, and autoimmune disease, highlighting the exhausted CD8⁺ T cell differentiation trajectory, CD4⁺ T cell helper function, T cell contributions to immunotherapy and autoimmune pathogenesis. We also discuss the development and function of γδ T cells in tissue surveillance, infection, and tumor immunity. Finally, we summarized current T-cell-based immunotherapies in both cancer and autoimmune diseases, with an emphasis on their clinical applications. A better understanding of T cell immunity provides insight into developing novel prophylactic and therapeutic strategies in human diseases.

Recent Progress in Multiple Sclerosis Treatment Using Immune Cells as Targets

Multiple sclerosis (MS) is an autoimmune-mediated demyelinating disease of the central nervous system. The main pathological features are inflammatory reaction, demyelination, axonal disintegration, reactive gliosis, etc. The etiology and pathogenesis of the disease have not been clarified. The initial studies believed that T cell-mediated cellular immunity is the key to the pathogenesis of MS. In recent years, more and more evidence has shown that B cells and their mediated humoral immune and innate immune cells (such as microglia, dendritic cells, macrophages, etc.) also play an important role in the pathogenesis of MS. This article mainly reviews the research progress of MS by targeting different immune cells and analyzes the action pathways of drugs. The types and mechanisms of immune cells related to the pathogenesis are introduced in detail, and the mechanisms of drugs targeting different immune cells are discussed in depth. This article aims to clarify the pathogenesis and immunotherapy pathway of MS, hoping to find new targets and strategies for the development of therapeutic drugs for MS.

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.

CCR7-mediated T follicular helper cell differentiation is associated with the pathogenesis and immune microenvironment of spinal cord injury-induced immune deficiency syndrome

Spinal cord injury-induced immune deficiency syndrome (SCI-IDS) is a disorder characterized by systemic immunosuppression secondary to SCI that dramatically increases the likelihood of infection and is difficult to treat. T follicular helper (Tfh) cells regulated by chemokine receptor CCR7 are associated with SCI-IDS after acute SCI. The present study explored the roles of CCR7 in SCI-IDS occurrence and immune microenvironment composition. Gene expression profile data of peripheral blood leukocytes from SCI and non-SCI subjects were collected from the Gene Expression Omnibus database. According to differential gene expression analysis, a protein-protein interaction (PPI) network, and risk model construction, the CCR7 expression level was prominently related to acute SCI and CCR7 expression was significantly downregulated after acute SCI. Next, we constructed a clinical prediction model and used it to identify patients with acute SCI. Using Gene Ontology (GO) analysis and gene set enrichment analysis (GSEA), we discovered that immune-related biological processes, such as T cell receptor signaling pathway, were suppressed, whereas chemokine-related signaling pathways were activated after acute SCI. Immune infiltration analysis performed using single sample GSEA and CIBERSORT suggested that Tfh cell function was significantly correlated with the CCR7 expression levels and was considerably reduced after acute SCI. Acute SCI was divided into two subtypes, and we integrated multiple classifiers to analyze and elucidate the immunomodulatory relationships in both subtypes jointly. The results suggested that CCR7 suppresses the immunodeficiency phenotype by activating the chemokine signaling pathway in Tfh cells. In conclusion, CCR7 exhibits potential as a diagnostic marker for acute SCI.

Gut Microbiome and Bile Acid Metabolism Induced the Activation of CXCR5+ CD4+ T Follicular Helper Cells to Participate in Neuromyelitis Optica Spectrum Disorder Recurrence

From the perspective of the role of T follicular helper (Tfh) cells in the destruction of tolerance in disease progression, more attention has been paid to their role in autoimmunity. To address the role of Tfh cells in neuromyelitis optica spectrum disorder (NMOSD) recurrence, serum C-X-C motif ligand 13 (CXCL13) levels reflect the effects of the Tfh cells on B-cell-mediated humoral immunity. We evaluated the immunobiology of the CXCR5+CD4+ Tfh cells in 46 patients with NMOSD, including 37 patients with NMOSD with an annual recurrence rate (ARR) of<1 and 9 patients with NMOSD with an ARR of ≥1. Herein, we reported several key observations. First, there was a lower frequency of circulating Tfh cells in patients with an ARR of<1 than in those with an ARR of ≥1 (P< 0.05). Second, the serum CXCL13 levels were downregulated in individuals with an ARR<1 (P< 0.05), processing the ability to promote Tfh maturation and chemotaxis. Third, the level of the primary bile acid, glycoursodeoxycholic acid (GUDCA), was higher in patients with NMOSD with an ARR of<1 than in those with NMOSD with an ARR of ≥1, which was positively correlated with CXCL13. Lastly, the frequency of the Tfh precursor cells decreased in the spleen of keyhole limpet haemocyanin-stimulated animals following GUDCA intervention. These findings significantly broaden our understanding of Tfh cells and CXCL13 in NMOSD. Our data also reveal the potential mechanism of intestinal microbiota and metabolites involved in NMOSD recurrence.

Comprehensive Flow Cytometry Profiling of the Immune System in COVID-19 Convalescent Individuals

SARS-CoV-2 has infected more than 200 million people worldwide, with more than 4 million associated deaths. Although more than 80% of infected people develop asymptomatic or mild COVID-19, SARS-CoV-2 can induce a profound dysregulation of the immune system. Therefore, it is important to investigate whether clinically recovered individuals present immune sequelae. The potential presence of a long-term dysregulation of the immune system could constitute a risk factor for re-infection and the development of other pathologies. Here, we performed a deep analysis of the immune system in 35 COVID-19 recovered individuals previously infected with SARS-CoV-2 compared to 16 healthy donors, by flow cytometry. Samples from COVID-19 individuals were analysed from 12 days to 305 days post-infection. We observed that, 10 months post-infection, recovered COVID-19 patients presented alterations in the values of some T-cell, B-cell, and innate cell subsets compared to healthy controls. Moreover, we found in recovered COVID-19 individuals increased levels of circulating follicular helper type 1 (cTfh1), plasmablast/plasma cells, and follicular dendritic cells (foDC), which could indicate that the Tfh-B-foDC axis might be functional to produce specific immunoglobulins 10 months post-infection. The presence of this axis and the immune system alterations could constitute prognosis markers and could play an important role in potential re-infection or the presence of long-term symptoms in some individuals.

Follicular Helper CD4+ T Cells, Follicular Regulatory CD4+ T Cells, and Inducible Costimulator and Their Roles in Multiple Sclerosis and Experimental Autoimmune Encephalomyelitis

Follicular helper CD4⁺ T (TFH) cells are a specialized subset of effector T cells that play a central role in orchestrating adaptive immunity. TFH cells mainly promote germinal center (GC) formation, provide help to B cells for immunoglobulin affinity maturation and class-switch recombination of B cells, and facilitate production of long-lived plasma cells and memory B cells. TFH cells express the nuclear transcriptional repressor B cell lymphoma 6 (Bcl-6), the chemokine (C-X-C motif) receptor 5 (CXCR5), the CD28 family members programmed cell death protein-1 (PD-1) and inducible costimulator (ICOS) and are also responsible for the secretion of interleukin-21 (IL-21) and IL-4. Follicular regulatory CD4+ T (TFR) cells, as a regulatory counterpart of TFH cells, participate in the regulation of GC reactions. TFR cells not only express markers of TFH cells but also express markers of regulatory T (Treg) cells containing FOXP3, glucocorticoid-induced tumor necrosis factor receptor (GITR), cytotoxic T lymphocyte antigen 4 (CTLA-4), and IL-10, hence owing to the dual characteristic of TFH cells and Treg cells. ICOS, expressed on activated CD4⁺ effector T cells, participates in T cell activation, differentiation, and effector process. The expression of ICOS is highest on TFH and TFR cells, indicating it as a key regulator of humoral immunity. Multiple sclerosis (MS) is a severe autoimmune disease that affects the central nervous system and results in disability, mediated by autoreactive T cells with evolving evidence of a remarkable contribution from humoral responses. This review summarizes recent advances regarding TFH cells, TFR cells, and ICOS, as well as their functional characteristics in relation to MS.

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.

Role of Monoclonal Antibody "Alemtuzumab" in the Treatment of Multiple Sclerosis

This article will review current treatment options for multiple sclerosis (MS) while keeping our primary focus on alemtuzumab, as it is now approved in more than 65 countries. From a pathophysiological point of view, MS is a disabling disease impacting a patient's life both physically and mentally, leading to devastating social and economic impact. This review will elaborate on alemtuzumab's role in treating relapsing-remitting MS (RRMS) by comparing its efficacy, side effects, and monitoring with other disease-modifying therapies (DMTs) available in the market. It is a point of great concern not only for physicians but also for neurologists, nephrologists, endocrinologists, dermatologists, and oncologists when encountering long-term effects of alemtuzumab in the life of treated MS patients. We hope that our review will not only benefit treating faculties but also those who are suffering from this devastating disease.

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.

IL-21 in Homeostasis of Resident Memory and Exhausted CD8 T Cells during Persistent Infection

CD4 T cells guide the development of CD8 T cells into memory by elaborating mitogenic and differentiation factors and by licensing professional antigen-presenting cells. CD4 T cells also act to stave off CD8 T cell dysfunction during repetitive antigen stimulation in persistent infection and cancer by mitigating generation of exhausted T cells (T_EX). CD4 T cell help is also required for establishing and maintaining tissue-resident memory T cells (T_RM), the nonrecirculating memory T cell subset parked in nonlymphoid tissues to provide frontline defense against reinvading pathogens. Interleukin (IL)-21 is the signature cytokine secreted by follicular helper CD4 T cells (T_FH) to drive B cell expansion and differentiation in germinal centers to mount high-affinity, isotype class-switched antibodies. In several infection models, IL-21 has been identified as the CD4 T help needed for formation and survival of T_RM and T_EX. In this review, we will explore the different memory subsets of CD8 T cells in persistent infections, the metabolic profiles associated with each, and evidence documenting the importance of CD4 T cell-derived IL-21 in regulating CD8 T_RM and T_EX development, homeostasis, and function.

Activated inducible co-stimulator-positive programmed cell death 1-positive follicular helper T cells indicate disease activity and severity in ulcerative colitis patients

Inducible co-stimulator-positive (ICOS) and programmed cell death 1-positive (PD-1) are important markers for follicular helper T cells (Tfh); however, their roles and clinical values in ulcerative colitis (UC) remain unknown. In this study, we recruited 68 UC patients and 34 healthy controls. Circulating ICOS⁺ , PD-1⁺ and ICOS⁺ PD-1⁺ Tfh subsets were analyzed by flow cytometry. Twelve active UC patients achieving remission after treatment with 5-aminosalicylic acid were followed-up and Tfh subset changes were analyzed. Serum immunoglobulin (Ig)G, C-reactive protein (CRP), interleukin (IL)-4 and IL-21 levels and B cell subsets were analyzed and Mayo scores were calculated. Correlation analyses were performed between Tfh subsets and the clinical indicators. Receiver operating characteristic (ROC) curves were generated to evaluate the efficiency of Tfh subsets for disease monitoring. We found that levels of ICOS⁺ , PD-1⁺ and ICOS⁺ PD-1⁺ Tfh cells were significantly increased in active UC and significantly decreased when achieving clinical remission. Activated ICOS⁺ PD-1⁺ Tfh cells were positively correlated with serum CRP and Mayo scores. Furthermore, ICOS⁺ PD-1⁺ Tfh cells were significantly correlated with circulating new memory B cells and plasmablasts, as well as serum IgG, IL-4 and IL-21. ROC analyses showed that when ICOS⁺ PD-1⁺ Tfh cells were used in combination with PD-1⁺ Tfh cells, the diagnostic efficacy in distinguishing active UC from stable remission patients was higher than that of any one used alone, with area under curve (AUC) value 0·931. Our findings suggest that increased ICOS⁺ PD-1⁺ Tfh cells are associated with the activation of B cells in the pathogenesis of UC, and may be a potential biomarker for UC disease monitoring.

Regulation of the germinal center and humoral immunity by interleukin-21

Here we review the critical and non-redundant functions of IL-21 in regulating humoral immune responses. We particularly focus on studies in natura—from individuals from inborn errors of immunity that impact on IL-21 production and/or function.

Cytokines play critical roles in regulating the development, survival, differentiation, and function of immune cells. Cytokines exert their function by binding specific receptor complexes on the surface of immune cells and activating intracellular signaling pathways, thereby resulting in induction of specific transcription factors and regulated expression of target genes. While the function of cytokines is often fundamental for the generation of robust and effective immunity following infection or vaccination, aberrant production or function of cytokines can underpin immunopathology. IL-21 is a pleiotropic cytokine produced predominantly by CD4⁺ T cells. Gene-targeting studies in mice, in vitro analyses of human and murine lymphocytes, and the recent discoveries and analyses of humans with germline loss-of-function mutations in IL21 or IL21R have revealed diverse roles of IL-21 in immune regulation and effector function. This review will focus on recent advances in IL-21 biology that have highlighted its critical role in T cell–dependent B cell activation, germinal center reactions, and humoral immunity and how impaired responses to, or production of, IL-21 can lead to immune dysregulation.

T follicular helper cell subsets: a potential key player in autoimmunity

Follicular helper T (Tfh) cells are one of CD4+ helper T subsets which promote B cell maturation, activation and antigen-specific antibody production. Autoantibodies are hallmarks of autoimmune diseases, and crucial contributions of Tfh cells in development of these diseases are now evident. Deregulation of Tfh activities can contribute to a pathogenic autoantibody production and can play an important role in the promotion of autoimmune diseases. These days multiple researchers reported three subpopulations which has distinct effector functions in Tfh cells: Tfh1, Tfh2 and Tfh17 cells. In this review, we summarize the observed alterations in whole Tfh cells and subset distribution during autoimmune diseases.

Immune and Inflammatory Determinants Underlying Alzheimer's Disease Pathology

This study examines the link between peripheral immune changes in perpetuation of the Alzheimer's disease (AD) neuropathology and cognitive deficits. Our research design using human AD patients and rodent model is supported by past evidence from genomic studies. We observed an active immune response against Aβ as indicated by the increased Aβ specific IgG antibody in the serum of AD and patients with mild cognitive impairments as compared to healthy controls. A similar increase in IgG and decrease in IgM antibody against Aβ was also confirmed in the 5xFAD mouse model of AD. More importantly, we observed a negative correlation between reduced IgM levels and cognitive dysfunction that manifested as impaired memory consolidation. Strong peripheral immune activation was supported by increased activation of microglia in the brain and macrophages in the spleen of AD mice compared to wild type control littermates. Furthermore, inflammatory cytokine IL-21 that is involved in antibody class switching was elevated in the plasma of AD patients and correlated positively with the IgG antibody levels. Concurrently, an increase in IL-21 and IL-17 was observed in spleen cells from AD mice. Further investigation revealed that proportions of T follicular helper (Tfh) cells that secrete IL-21 are increased in the spleen of AD mice. In contrast to Tfh, the frequency of B1 cells that produce IgM antibodies was reduced in AD mice. Altogether, these data indicate that in AD the immune tolerance to Aβ is compromised leading to chronic immune/inflammatory responses against Aβ that are detrimental and cause neuropathology. Graphical Abstract Healthy subjects are tolerant to Aβ and usually react weakly to it resulting the in the production of IgM class of antibodies that are efficient at clearing up self-antigens such as Aβ without causing inflammation. In contrast, Alzheimer's disease patients mount a strong immune response against Aβ probably in an effort to clear up excessive Aβ. There is enhanced production of inflammatory cytokines such as IL-21 as well as an increase in Tfh cells that cause antibody class switching form IgM to IgG. The strong immune response is inefficient at clearing up Aβ and instead exacerbates inflammation that causes AD neuropathology and cognitive dysfunction.

Restoration of regulatory B cell deficiency following alemtuzumab therapy in patients with relapsing multiple sclerosis

Background

Regulatory B cells (Bregs), which protect from autoimmunity, are deficient in multiple sclerosis (MS). Novel regulatory B cell subsets CD19⁺CD24^hiCD38^hi cells and CD19⁺PD-L1^hi cells, with disparate regulatory mechanisms have been defined. Alemtuzumab provides a long-lasting suppression of disease activity in MS. In contrast to its documented efficacy, alemtuzumab’s mechanism of action is not fully understood and information about the composition of repopulating B cell pool is scarce.

Aim

To characterize repopulated B cell subsets and elucidate alemtuzumab’s mechanism of action in B cell perspective.

Methods

The frequency and the absolute number of Bregs were studied in peripheral blood mononuclear cells (PBMC) of 37 MS patients and 11 healthy controls (HC). Longitudinal analysis of the frequency and the absolute number of Bregs in PBMC of 11 MS patients was evaluated, before and at 6, 9, and 12 months post alemtuzumab.

Results

We found deficiency of CD19⁺CD24^hiCD38^hi cells during relapse compared to remission and HC (relapse vs remission: p = 0.0006, relapse vs HC: p = 0.0004). CD19⁺PD-L1^hi cells were deficient during relapse than remission and HC (relapse vs remission: p = 0.0113, relapse vs HC: p = 0.0007). Following alemtuzumab, the distribution of B cells shifts towards naïve phenotype and Breg deficiency is restored. The frequency of CD19⁺CD24^hiCD38^hi cells was significantly increased at 6 M and 9 M compared to 0 M (6 M vs 0 M: p = 0.0004, 9 M vs 0 M: p = 0.0079). At 9 M, the frequency of CD19⁺CD24^hiCD38^hi cells started to decrease and by 12 M the frequency was reduced compared to 6 M, although it was significantly higher than baseline level (12 M vs 0 M: p = 0.0257). The absolute number was significantly increased at 6 M and 9 M post-alemtuzumab (6 M vs 0 M: p = 0.0063, 9 M vs 0 M: p = 0.02). The frequency of CD19⁺PD-L1^hi cells significantly increased until 12 M (6 M vs 0 M: p = 0.0004, 12 M vs 0 M: p = 0.0036). The frequency of CD19⁺PD-L1^hi cells at 12 M was significantly higher than 9 M (p = 0.0311). We further pinpoint that CD19⁺CD24^hiCD38^hi cells were deficient at severe relapses following alemtuzumab infusion and restored during recovery.

Conclusions

Our results highlight the preferential reconstitution of Bregs as a possible mechanism of action of alemtuzumab and CD19⁺CD24^hiCD38^hi cells as a potential biomarker for disease activity.

T Follicular Helper Cells in Autoimmune Disorders

T follicular helper (Tfh) cells are a distinct subset of CD4⁺ T lymphocytes, specialized in B cell help and in regulation of antibody responses. They are required for the generation of germinal center reactions, where selection of high affinity antibody producing B cells and development of memory B cells occur. Owing to the fundamental role of Tfh cells in adaptive immunity, the stringent control of their production and function is critically important, both for the induction of an optimal humoral response against thymus-dependent antigens but also for the prevention of self-reactivity. Indeed, deregulation of Tfh activities can contribute to a pathogenic autoantibody production and can play an important role in the promotion of autoimmune diseases. In the present review, we briefly introduce the molecular factors involved in Tfh cell formation in the context of a normal immune response, as well as markers associated with their identification (transcription factor, surface marker expression, and cytokine production). We then consider in detail the role of Tfh cells in the pathogenesis of a broad range of autoimmune diseases, with a special focus on systemic lupus erythematosus and rheumatoid arthritis, as well as on the other autoimmune/inflammatory disorders. We summarize the observed alterations in Tfh numbers, activation state, and circulating subset distribution during autoimmune and some other inflammatory disorders. In addition, central role of interleukin-21, major cytokine produced by Tfh cells, is discussed, as well as the involvement of follicular regulatory T cells, which share characteristics with both Tfh and regulatory T cells.

Peripheral imbalanced TFH/TFR ratio correlates with intrathecal IgG synthesis in multiple sclerosis at clinical onset

BACKGROUND

Alteration of T-follicular helper (TFH) and regulatory (TFR) subpopulations may contribute to the development of auto-reactive B-cell.

OBJECTIVE

To investigate whether changes in TFH and TFR subsets are associated with abnormal IgG synthesis in blood and cerebrospinal fluid (CSF) of multiple sclerosis (MS) patients.

METHODS

Paired blood and CSF samples were obtained from 31 untreated relapsing-remitting multiple sclerosis (RRMS) patients at diagnosis. Peripheral blood TFH (CD3+CD4+CXCR5+CD25-CD127+), TFR (CD3+CD4+CXCR5+CD25+CD127^dim), conventional T-Helper (TH, CD3+CD4+CXCR5-CD25-CD127+), and regulatory T-cells (T-Reg, CD3+CD4+CXCR5-CD25+CD127^dim) were analyzed in all RRMS patients and in 13 healthy controls (HCs). Qualitative and quantitative intrathecal IgG synthesis was evaluated in RRMS patients, who were then further subclassified according to the presence of IgG oligoclonal bands in blood and/or CSF.

RESULTS

Compared to HC, RRMS had lower TFR percentage ( p < 0.01) and higher TFH/TFR ratio ( p < 0.001). In RRMS, TFH/TFR ratio correlated with both qualitative ( r = 0.56, p < 0.005) and quantitative intrathecal IgG synthesis (IgG Index: r = 0.78; IgGLoc: r = 0.79; IgGIF: r = 0.76, all p < 0.001). Patients with the highest TFH/TFR ratios had higher percentages of circulating B-cells (36.1 ± 35.2%, p < 0.05).

CONCLUSION

In RRMS, increased TFH/TFR ratio associates with abnormal IgG production in blood and CSF, suggesting that antibody-producing cells, derived from deregulated peripheral germinal center reaction, colonize the CNS.

Relapsing-Remitting Multiple Sclerosis Is Characterized by a T Follicular Cell Pro-Inflammatory Shift, Reverted by Dimethyl Fumarate Treatment

Multiple sclerosis (MS) is considered a T cell-mediated autoimmune disease, although several evidences also demonstrate a B cell involvement in its etiology. Follicular T helper (Tfh) cells, a CXCR5-expressing CD4+ T cell subpopulation, are essential in the regulation of B cell differentiation and maintenance of humoral immunity. Alterations in circulating (c)Tfh distribution and/or function have been associated with autoimmune diseases including MS. Dimethyl fumarate (DMF) is a recently approved first-line treatment for relapsing-remitting MS (RRMS) patients whose mechanism of action is not completely understood. The aim of our study was to compare cTfh subpopulations between RRMS patients and healthy subjects and evaluate the impact of DMF treatment on these subpopulations, relating them to changes in B cells and humoral response. We analyzed, by flow cytometry, the distribution of cTfh1 (CXCR3+CCR6-), cTfh2 (CXCR3-CCR6-), cTfh17 (CXCR3-CCR6+), and the recently described cTfh17.1 (CXCR3+CCR6+) subpopulations of CD4+ Tfh (CD45RA-CXCR5+) cells in a cohort of 29 untreated RRMS compared to healthy subjects. CD4+ non-follicular T helper (Th) cells (CD45RA-CXCR5-) were also studied. We also evaluated the effect of DMF treatment on these subpopulations after 6 and 12 months treatment. Untreated RRMS patients presented higher percentages of cTfh17.1 cells and lower percentages of cTfh2 cells consistent with a pro-inflammatory bias compared to healthy subjects. DMF treatment induced a progressive increase in cTfh2 cells, accompanied by a decrease in cTfh1 and the pathogenic cTfh17.1 cells. A similar decrease of non-follicular Th1 and Th17.1 cells in addition to an increase in the anti-inflammatory Th2 subpopulation were also detected upon DMF treatment, accompanied by an increase in naïve B cells and a decrease in switched memory B cells and serum levels of IgA, IgG2, and IgG3. Interestingly, this effect was not observed in three patients in whom DMF had to be discontinued due to an absence of clinical response. Our results demonstrate a possibly pathogenic cTfh pro-inflammatory profile in RRMS patients, defined by high cTfh17.1 and low cTfh2 subpopulations that is reverted by DMF treatment. Monitoring cTfh subsets during treatment may become a biological marker of DMF effectiveness.

T Follicular Helper-Like Cells Are Involved in the Pathogenesis of Experimental Autoimmune Encephalomyelitis

Multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE) have been proved to be T cell-mediated autoimmune diseases. Recent researches indicate that humoral immunity is also involved in the pathogenesis of these disorders. T follicular helper (Tfh) cells are critical for B cell differentiation and antibody production. However, the role of Tfh cells in MS and EAE remains unclear. Here, we found elevated frequencies of CD4⁺CXCR5⁺PD-1⁺ Tfh-like cells in both MS patients and EAE. In EAE mice, Tfh-like cells, together with B cells, were found in the ectopic lymphoid structures in spinal cords. Moreover, Tfh-like cells promoted the antibody production via IL-21/IL-21R and CD40 ligand/CD40 interaction and the synergy effect of STAT3 and non-canonical NF-κB signaling pathway inside B cells. Moreover, adoptive transfer of Tfh-like cells could increase the severity and delay the remission of EAE. In conclusion, our data indicate that Tfh-like cells contribute to the pathogenesis of EAE.

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.

High frequency of circulating follicular helper T cells is correlated with B cell subtypes in patients with ankylosing spondylitis

T follicular helper (Tfh) cells are known to support effector B cells and enhance autoimmunity; however, the association between the Tfh cells and B cells in ankylosing spondylitis (AS) is unclear. The aim of the present study was to measure the frequency of circulating cluster of differentiation (CD)4⁺ C-X-C chemokine receptor type 5 (CXCR5)⁺ Tfh cells and B cell subtypes in peripheral blood from patients with AS, and evaluate the correlation of these factors. Percentages of peripheral blood circulating CD4⁺CXCR5⁺ Tfh cells and B cell subtypes were measured via flow cytometry and the disease activity of individual patients was measured using the Bath AS Disease Activity Index (BASDAI). The potential association among these measures was analyzed via Spearman's or Pearson's correlations. In comparison with those in healthy controls (HC), significantly increased percentages of CD4⁺CXCR5⁺ cTfh, CD4⁺CXCR5⁺ programmed death 1⁺, CD4⁺CXCR5⁺ inducible T cell costimulator (ICOS)⁺, CD3⁺CD8^-CXCR5⁺ interleukin (IL)-21⁺ T cells, CD19⁺CD27^high plasmablast and CD19⁺CD38⁺ antibody-secreting B cells were detected in patients with AS, whereas there was no significant difference in CD19⁺CD27^- naïve B cells and CD19⁺CD27⁺ memory B cells. When Patients with AS were divided into high and low activity groups, significantly higher percentages of CD4⁺CXCR5⁺, CD3⁺CD8^-CXCR5⁺IL-21⁺ T cells, CD19⁺CD27^- naïve B cells and CD19⁺CD38⁺ antibody-secreting B cells, and lower CD19⁺CD27⁺ memory B cells were detected in high activity AS group compared with the low activity AS group. In addition, percentages of CD4⁺CXCR5⁺ circulating (c)Tfh, CD3⁺CD8^-CXCR5⁺IL-21⁺ T and CD19⁺CD38⁺ antibody-secreting B cells were positively correlated with BASDAI values. Furthermore, the percentage of CD4⁺CXCR5⁺ cTfh cells was positively correlated with CD19⁺CD38⁺ antibody-secreting B cells and the percentage of CD3⁺CD8^-CXCR5⁺IL-21⁺ T cells was positively correlated with CD19⁺CD27^- naïve B cells in patients with AS. These findings suggest that CD4⁺CXCR5⁺ cTfh, CD3⁺CD8^-CXCR5⁺IL-21⁺ T and CD19⁺CD38⁺ antibody-secreting B cells may participate in the pathogenesis of AS because of their distinct functions. As such, levels of cTfh and B cell subtypes may be a useful biomarker for the evaluation of disease activity in patients with AS.

Role of Immunological Memory Cells as a Therapeutic Target in Multiple Sclerosis

Pharmacological targeting of memory cells is an attractive treatment strategy in various autoimmune diseases, such as psoriasis and rheumatoid arthritis. Multiple sclerosis is the most common inflammatory disorder of the central nervous system, characterized by focal immune cell infiltration, activation of microglia and astrocytes, along with progressive damage to myelin sheaths, axons, and neurons. The current review begins with the identification of memory cell types in the previous literature and a recent description of the modulation of these cell types in T, B, and resident memory cells in the presence of different clinically approved multiple sclerosis drugs. Overall, this review paper tries to determine the potential of memory cells to act as a target for the current or newly-developed drugs.

An investigation of the relationship between recurrent spontaneous abortion and memory T follicular helper cells

PROBLEM

Immune tolerance with respect to a semi-allogeneic fetus plays a key role in the establishment of a pregnancy. Memory T follicular helper (Tfh) cells have a central role in the regulation of the adaptive immune response. Much of our knowledge of memory Tfh cells' function comes from immune-related diseases. However, the true physiological characteristics of memory Tfh cells and their mode of action in pregnancy remain unclear.

METHODS OF STUDY

Deciduas and blood were obtained from 25 recurrent spontaneous abortion (RSA) patients undergoing surgical abortion and 19 normal women in early pregnancy undergoing elective termination. RSA patients were grouped into antibody-positive patients and antibody-negative patients, respectively. The memory Tfh cells with the CD4⁺ CXCR5⁺ PD1⁺ CCR7^- and CD4⁺ CXCR5⁺ PD-1⁺ ICOS⁺ phenotypes were assessed by flow cytometry. The B cells were evaluated by flow cytometry. A correlation analysis of the subsets of memory Tfh cells and B cells in antibody-positive RSA patients was made by the Pearson test.

RESULTS

Memory Tfh cells with the CD4⁺ CXCR5⁺ PD1⁺ CCR7^- and CD4⁺ CXCR5⁺ PD-1⁺ ICOS⁺ phenotypes showed a significant increase in RSA patients compared to women with a normal pregnancy who had chosen termination. When RSA patients were grouped according positive or negative antibodies, it was surprising to find that decidual CD4⁺ CXCR5⁺ PD-1⁺ ICOS⁺ memory Tfh cells significantly increased in RSA patients with positive antibody compared to RSA patients with negative antibody. However, the percentages of CD4⁺ CXCR5⁺ PD1⁺ CCR7^- memory Tfh cells did not change in the deciduas of the two groups. Circulating and decidual B cells significantly increased in antibody-positive RSA patients compared with antibody-negative RSA patients. Correlation analysis indicated a strong association between the decidual CD4⁺ CXCR5⁺ PD-1⁺ ICOS⁺ memory Tfh cells and B cells in antibody-positive RSA patients.

CONCLUSION

These new findings provide unique insights into memory Tfh cells in mediating feto-maternal immune tolerance.

High frequencies of circulating Tfh-Th17 cells in myasthenia gravis patients

Recent studies show that the frequencies of circulating follicullar helper T (cTfh) cells are significantly higher in myasthenia gravis (MG) patients compared with healthy controls (HC). And, they are positively correlated with levels of serum anti-acetylcholine receptor antibody (anti-AchR Ab). It is unclear whether cTfh cell subset frequencies are altered and what role they play in MG patients. In order to clarify this, we examined the frequencies of cTfh cell counterparts, their subsets, and circulating plasmablasts in MG patients by flow cytometry. We determined the concentrations of serum anti-AChR Ab by enzyme-linked immunosorbent assay (ELISA). We assayed the function of cTfh cell subsets by flow cytometry and real-time polymerase chain reaction (RT-PCR). We found higher frequencies of cTfh cell counterparts, cTfh-Th17 cells, and plasmablasts in MG patients compared with HC. The frequencies of cTfh cell counterparts and cTfh-Th17 cells were positively correlated with the frequencies of plasmablasts and the concentrations of anti-AChR Ab in MG patients. Functional assays showed that activated cTfh-Th17 cells highly expressed key molecular features of Tfh cells including ICOS, PD-1, and IL-21. Results indicate that, just like cTfh cell counterparts, cTfh-Th17 cells may play a role in the immunopathogenesis and the production of anti-AChR Ab of MG.

Dimethyl fumarate induces changes in B- and T-lymphocyte function independent of the effects on absolute lymphocyte count

BACKGROUND

Dimethyl fumarate (DMF) is used to treat relapsing multiple sclerosis and causes lymphopenia in a subpopulation of treated individuals. Much remains to be learned about how the drug affects B- and T-lymphocytes.

OBJECTIVES

To characterize changes in B- and T-cell phenotype and function induced by DMF and to investigate whether low absolute lymphocyte count (ALC) is associated with unique functional changes.

METHODS

Peripheral blood mononuclear cells (PBMCs) were collected from DMF-treated patients, untreated patients, and healthy controls. A subset of DMF-treated patients was lymphopenic (ALC < 800). Multiparametric flow cytometry was used to evaluate cellular phenotypes. Functional response to non-specific and viral peptide stimulation was assessed.

RESULTS

DMF reduced circulating memory B-cells regardless of ALC. Follicular T-helper cells (CD4⁺ CXCR5⁺) and mucosal invariant T-cells (CD8⁺ CD161⁺) were also reduced. DMF reduced T-cell production of pro-inflammatory cytokines in response to polyclonal (PMA/ionomycin) and viral peptide stimulation, regardless of ALC. No differences in activation-induced cell death or circulating progenitors were observed between lymphopenic and non-lymphopenic DMF-treated patients.

CONCLUSION

These data implicate DMF-induced changes in lymphocytes as an important component of the drug's efficacy and expand our understanding of the functional significance of DMF-induced lymphopenia.

Circulating immune cells in multiple sclerosis

Circulating T and B lymphocytes contribute to the pathogenesis of the neuroinflammatory autoimmune disease, multiple sclerosis (MS). Further progress in the development of MS treatments is dependent upon a greater understanding of the immunological disturbances that underlie the disease. Analyses of circulating immune cells by flow cytometry have revealed MS-associated alterations in the composition and function of T and B cell subsets, including temporal changes associated with disease activity. Disturbances in circulating immune populations reflect those observed in the central nervous system and include skewing towards proinflammatory CD4⁺ and CD8⁺ T cells and B cells, greater proportions of follicular T helper cells and functional defects in the corresponding T and B regulatory subsets. Utilizing the analytical power of modern flow cytometers, researchers are now well positioned to monitor immunological changes associated with disease activity or intervention, describe immunological signatures with predictive value and identify targets for therapeutic drug development. This review discusses the contribution of various T and B lymphocyte subsets to MS pathogenesis, provides current and relevant phenotypical descriptions to assist in experimental design and highlights areas of future research.

Functional RNAs control T follicular helper cells

T follicular helper cells (Tfh cells), which are a prototypic subset of effector CD4⁺ T cells, regulate the production of high-affinity antibodies by controlling B cells at initial and recall phases. Since the discovery of Tfh cells in human tonsils, many notable studies focusing on Tfh cells have clarified mechanisms underlying Tfh-cell-related physiological and pathological settings. Results of these studies revealed a chief regulatory function of BCL6 in Tfh cells and the involvement of Tfh cells in the pathogenesis of various disorders including autoimmune diseases, allergies and cancers. Further, accumulating evidence has revealed microRNAs (miRNAs) of functional noncoding RNAs (ncRNAs) to be cardinal regulators of Tfh cells during the processes of development, differentiation and plasticity. In this review article, we summarize and discuss the results of recent studies about miRNAs operating Tfh-cell function and their relationships in diseases. Through the window of such functional ncRNAs, the functional significance of Tfh cells in CD4⁺ T-cell biology is becoming apparent. Studies to determine the complex background of the genetic program of Tfh cells operated by functional RNAs should lead to an understanding of the manifestations of Tfh cells with unidentified pathophysiological relevance.

Follicular Helper T Cells in Autoimmunity

The development of multiple disease-relevant autoantibodies is a hallmark of autoimmune diseases. In autoimmune type 1 diabetes (T1D), a variable time frame of autoimmunity precedes the clinically overt disease. The relevance of T follicular helper (TFH) cells for the immune system is increasingly recognized. Their pivotal contribution to antibody production by providing help to germinal center (GC) B cells facilitates the development of a long-lived humoral immunity. Their complex differentiation process, involving various stages and factors like B cell lymphoma 6 (Bcl6), is strictly controlled, as anomalous regulation of TFH cells is connected with immunopathologies. While the adverse effects of a TFH cell-related insufficient humoral immunity are obvious, the role of increased TFH frequencies in autoimmune diseases like T1D is currently highlighted. High levels of autoantigen trigger an excessive induction of TFH cells, consequently resulting in the production of autoantibodies. Therefore, TFH cells might provide promising approaches for novel therapeutic strategies.

The autoimmunity-associated gene RGS1 affects the frequency of T follicular helper cells

RGS1 (regulator of G-protein signaling 1) has been associated with multiple autoimmune disorders including type I diabetes. RGS1 desensitizes the chemokine receptors CCR7 and CXCR4 that are critical to the localization of T and B cells in lymphoid organs. To explore how RGS1 variation contributes to autoimmunity, we generated Rgs1 knockdown (KD) mice in the nonobese diabetic (NOD) model for type I diabetes. We found that Rgs1 KD increased the size of germinal centers, but decreased the frequency of T follicular helper (TFH) cells. We show that loss of Rgs1 in T cells had both a T cell-intrinsic effect on migration and TFH cell frequency, and an indirect effect on B-cell migration and germinal center formation. Notably, several recent publications described an increase in circulating TFH cells in patients with type I diabetes, suggesting this cell population is involved in pathogenesis. Though Rgs1 KD was insufficient to alter diabetes frequency in the NOD model, our findings raise the possibility that RGS1 plays a role in autoimmunity owing to its function in TFH cells. This mechanistic link, although speculative at this time, would lend support to the notion that TFH cells are key participants in autoimmunity and could explain the association of RGS1 with several immune-mediated diseases.