High frequencies of activated B cells and T follicular helper cells are correlated with disease activity in patients with new-onset rheumatoid arthritis

Polarization of circulating follicular helper T cells correlates with bullous pemphigoid severity

BACKGROUND

Follicular helper T (Tfh) cells form a distinct population of T-helper cells with different polarizations (type 1, type 2 and type 17) that regulates humoral responses and may participate in the pathophysiology of B-cell-mediated autoimmune diseases such as bullous pemphigoid (BP), a dermatosis mediated by autoantibodies specific for hemi-desmosomal proteins.

OBJECTIVES

To evaluate the impact on circulating Tfh cells of super potent topical corticosteroid (TCS) treatment, which is more effective and safer than high doses of oral corticosteroids, and is the recommended first-line treatment of BP.

METHODS

Using flow cytometry, we compared the frequency, polarization and activation of Tfh cells in the blood of patients with BP with age- and sex-matched control participants without BP at baseline and longitudinally, after the initiation of TCS treatment.

RESULTS

We found that, at baseline, circulating Tfh cells were more frequent in patients with BP than in participants without BP and exhibited an activated phenotype. We further showed a decrease in type 1 and an increase in type 17 Tfh cells in the blood of patients with BP, which resulted in a higher type 2 + type 17 to type 1 Tfh cell ratio. This ratio correlated positively with disease severity, as measured by the Bullous Pemphigoid Disease Area Index. Remarkably, with TCS treatment, although the frequency of Tfh cells in patients with BP returned to a level similar to that of control participants, the activated phenotype persisted. Interestingly, serum interleukin-21 levels and the Tfh cell subset ratio, similarly to disease activity and serum anti-BP180 and anti-BP230 autoantibodies, decreased with TCS treatment.

CONCLUSIONS

Overall, our findings suggest the involvement Tfh cell polarization in the pathophysiology of BP and open the door to modulation of Tfh cell activity for treatment purposes.

Helper T cells: A potential target for sex hormones to ameliorate rheumatoid arthritis? (Review)

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease whose etiology is not fully understood. Defective peripheral immune tolerance and subsequent mis‑differentiation and aberrant infiltration of synovium by various immune cells, especially helper T (Th) cells, play an important role in the development of RA. There are significant sex differences in RA, but the results of studies on the effects of sex hormones on RA have been difficult to standardize and hormone replacement therapy has been limited by the potential for serious side effects. Existing research has amply demonstrated that cellular immune responses are largely determined by sex and that sex hormones play a key role in Th cell responses. Based on the aforementioned background and the plasticity of Th cells, it is reasonable to hypothesize that the action of sex hormones on Th cells will hopefully become a therapeutic target for RA. The present review discussed the role of various Th cell subsets in the pathogenesis of RA and also explored the role of sex hormones on the phenotype and function of these aberrantly regulated immune cells in RA as well as other pathologic effects on RA.

Control of T-cell immunity by fatty acid metabolism

Fatty acids play critical roles in maintaining the cellular functions of T cells and regulating T-cell immunity. This review synthesizes current research on the influence of fatty acids on T-cell subsets, including CD8+ T cells, TH1, TH17, Treg (regulatory T cells), and TFH (T follicular helper) cells. Fatty acids impact T cells by modulating signaling pathways, inducing metabolic changes, altering cellular structures, and regulating gene expression epigenetically. These processes affect T-cell activation, differentiation, and function, with implications for diseases such as autoimmune disease and cancer. Based on these insights, fatty acid pathways can potentially be modulated by novel therapeutics, paving the way for novel treatment approaches for immune-mediated disorders and cancer immunotherapy.

Evolving understanding of autoimmune mechanisms and new therapeutic strategies of autoimmune disorders

Autoimmune disorders are characterized by aberrant T cell and B cell reactivity to the body's own components, resulting in tissue destruction and organ dysfunction. Autoimmune diseases affect a wide range of people in many parts of the world and have become one of the major concerns in public health. In recent years, there have been substantial progress in our understanding of the epidemiology, risk factors, pathogenesis and mechanisms of autoimmune diseases. Current approved therapeutic interventions for autoimmune diseases are mainly non-specific immunomodulators and may cause broad immunosuppression that leads to serious adverse effects. To overcome the limitations of immunosuppressive drugs in treating autoimmune diseases, precise and target-specific strategies are urgently needed. To date, significant advances have been made in our understanding of the mechanisms of immune tolerance, offering a new avenue for developing antigen-specific immunotherapies for autoimmune diseases. These antigen-specific approaches have shown great potential in various preclinical animal models and recently been evaluated in clinical trials. This review describes the common epidemiology, clinical manifestation and mechanisms of autoimmune diseases, with a focus on typical autoimmune diseases including multiple sclerosis, type 1 diabetes, rheumatoid arthritis, systemic lupus erythematosus, and sjögren's syndrome. We discuss the current therapeutics developed in this field, highlight the recent advances in the use of nanomaterials and mRNA vaccine techniques to induce antigen-specific immune tolerance.

Helper T Cells are Hyperactive and Contribute to the Dysregulation of Antibody Production in Patients with Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease, mediated by a complex interaction between B cells and various subsets of T cells. Dysfunction of helper T (Th) and regulatory T (Treg) cells may contribute to the breakdown of self-tolerance and the progression of autoimmune disease. In this study, we investigated the activity of Th and Treg cells on the differentiation of autologous B cells in vitro using cell cultures from the peripheral blood of healthy controls (HCs) and RA patients. The expressions of programmed death 1 (PD-1) and IL-21 were monitored as activation markers for Th cells. Unstimulated Th cells from RA patients showed remarkably higher PD-1 expression than HC samples. Stimulation of Th cells from RA patients with Staphylococcus enterotoxin B (SEB) in the presence of B cells significantly induced their PD-1 and IL-21 expression at a considerably higher level in RA compared to HCs, and Treg cells did not affect IL-21 production. When monitoring B-cell differentiation, a significantly higher frequency of plasma cells was observed, even in unstimulated samples of RA patients compared to HCs. In the SEB-stimulated co-cultures of the RA samples, plasma cell frequency and IgG production were considerably higher than in HCs and were not significantly affected by Tregs. These findings demonstrate that Th cells are constitutively active in RA, and their hyperactivity upon interaction with diseased B cells may lead to uncontrolled antibody production.

Role of T follicular helper cells in autoimmune rheumatic Diseases: A systematic review on immunopathogenesis and response to treatment

BACKGROUND

T follicular helper (Tfh) cells are a subdivision of T helper cells involved in antigen-specific B cell immunity. Tfh cells play an essential role in the interaction of T cells/B cells in the germinal centers (GC), and dysregulation of Tfh actions can offer pathogenic autoantibody formation and lead to the development of autoimmune diseases. This study seeks to evaluate changes in Tfh frequency and its related cytokines in autoimmune disease, its association with disease phase, severity, prognosis, and the effect of immunosuppressive treatment on the Tfh population.

METHOD

The study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 Statement. Electronic databases, including PubMed, Scopus, Web of Science, and Embase, were systematically searched for potentially eligible studies up to January 1, 2024.

RESULTS

We identified 4998 articles in the initial search, from which 1686 similar titles were removed. A total of 3312 articles were initially screened, and 3051 articles were excluded by title/abstract screening. A total of 261 studies were considered for full-text assessment, and 205 articles were excluded by reason. Finally, a total of 56 studies were included in our review.

CONCLUSION

The population of Tfh cells is generally higher in autoimmune diseases versus Health control. Moreover, the number of Tfh cells is associated with the disease severity and can be considered for determining the prognosis of studies. Also, peripheral blood circulating Tfh (cTfh) cells are an available sample that can be used as an indicator for diagnosing diseases.

High dimensional proteomic mapping of bone marrow immune characteristics in immune thrombocytopenia

To investigate the role of co-stimulatory and co-inhibitory molecules on immune tolerance in immune thrombocytopenia (ITP), this study mapped the immune cell heterogeneity in the bone marrow of ITP at the single-cell level using Cytometry by Time of Flight (CyTOF). Thirty-six patients with ITP and nine healthy volunteers were enrolled in the study. As soluble immunomodulatory molecules, more sCD25 and sGalectin-9 were detected in ITP patients. On the cell surface, co-stimulatory molecules like ICOS and HVEM were observed to be upregulated in mainly central memory and effector T cells. In contrast, co-inhibitory molecules such as CTLA-4 were significantly reduced in Th1 and Th17 cell subsets. Taking a platelet count of 30×109 L-1 as the cutoff value, ITP patients with high and low platelet counts showed different T cell immune profiles. Antigen-presenting cells such as monocytes and B cells may regulate the activation of T cells through CTLA-4/CD86 and HVEM/BTLA interactions, respectively, and participate in the pathogenesis of ITP. In conclusion, the proteomic and soluble molecular profiles brought insight into the interaction and modulation of immune cells in the bone marrow of ITP. They may offer novel targets to develop personalized immunotherapies.

The changes of intestinal flora and its relevance with memory Tfh and B cells in rheumatoid arthritis patients treated with csDMARDs and csDMARDs + bDMARDs

BACKGROUND

A growing body of experimental and clinical evidence has implicated gut microbiota in the onset and course of rheumatoid arthritis (RA). The imbalance of intestinal flora in RA patients may lead to abnormal expression of immune cells and related cytokines.

PURPOSE

Conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) and conventional synthetic disease-modifying antirheumatic drugs combined with biological disease-modifying antirheumatic drugs (csDMARDs + bDMARDs) are widely used to treat RA, but the characteristics of gut microbiota before and after treatment and their relationship with memory Tfh/B cells and cytokines remain unclear.

METHODS

Stool samples were collected from 50 RA patients and 25 healthy controls (HCs) for 16SrRNA gene sequencing. We examined the proportion of lymphocyte subsets in healthy controls and RA patients. Enzyme linked immunosorbent assay (ELISA) was used to detect the levels of related cytokines in serum. The α and β diversity of intestinal flora, and the correlation between intestinal flora and clinical indicators, lymphocyte subsets, cytokines were analyzed.

RESULT

At the genus level, Ruminococcaceae_Ruminococcus was decreased in the csDMARDs and csDMARDs + bDMARDs treatment group, whereas Faecalibacterium was reduced in the csDMARDs treatment group, compared to untreated group. CD4+CD45RO+CCR7+CXCR5+central memory Tfh cells and CD4+CD45RO+CCR7-CXCR5+effector memory Tfh cells were significantly lower in the csDMARDs + bDMARDs treatment group than in untreated group. CD19+CD27+IgD+pre-switched memory B cells were higher in the csDMARDs and csDMARDs + bDMARDs treatment groups, whereas CD19+CD27+IgD-switched memory B cells were significantly lower than in untreated group. Ruminococcaceae_Ruminococcus was negatively correlated with CD19+CD27+IgD+ pre-switched memory B cells but positively correlated with CD4+CD45RO+CCR7-CXCR5+effector memory Tfh and CD19+CD27+IgD-switched memory B cells in patients with RA treated with DMARDs.

CONCLUSION

The gut microbiota, memory Tfh cells, memory B cells, and cytokines of patients with RA changed significantly under different treatment regimens and had certain correlations with the clinical indicators of RA.

Circulating Immune Landscape Profiling in Psoriasis Vulgaris and Psoriatic Arthritis by Mass Cytometry

Background

Psoriasis, a systemic disorder mediated by the immune system, can appear on the skin, joints, or both. Individuals with cutaneous psoriasis (PsC) have an elevated risk of developing psoriatic arthritis (PsA) during their lifetime. Despite this known association, the cellular and molecular mechanisms underlying this progression remain unclear.

Methods

We performed high-dimensional, in-depth immunophenotyping of peripheral blood mononuclear cells (PBMCs) in patients with PsA and psoriasis vulgaris (PsV) by mass cytometry. Blood samples were collected before and after therapy for a longitudinal study. Then three sets of comparisons were made here: active PsA vs. active PsV, untreated PsV vs. treated PsV, and untreated PsA vs. treated PsA.

Results

Marked differences were observed in multiple lymphocyte subsets of PsA related to PsV, with expansion of CD4+ T cells, CD16- NK cells, and B cells. Notably, two critical markers, CD28 and CD127, specifically differentiated PsA from PsV. The expression levels of CD28 and CD127 on both Naïve T cells (TN) and central memory CD4+ T cells (TCM) were considerably higher in PsA than PsV. Meanwhile, after treatment, patients with PsV had higher levels of CD28hi CD127hi CD4+ TCM cells, CD28hi CD127hi CD4+ TN cells, and CD16- NK cells.

Conclusion

In the circulation of PsA patients, the TN and CD4+ TCM are characterized with more abundant CD28 and CD127, which effectively distinguished PsA from PsV. This may indicate that individuals undergoing PsV could be stratified at high risk of developing PsA based on the circulating levels of CD28 and CD127 on specific cell subsets.

Comprehensive Co-Inhibitory Receptor (Co-IR) Expression on T Cells and Soluble Proteins in Rheumatoid Arthritis

Co-inhibitory receptors (Co-IRs) are essential in controlling the progression of immunopathology in rheumatoid arthritis (RA) by limiting T cell activation. The objective of this investigation was to determine the phenotypic expression of Co-IR T cells and to assess the levels of serum soluble PD-1, PDL-2, and TIM3 in Taiwanese RA patients.

METHODS

Co-IRs T cells were immunophenotyped employing multicolor flow cytometry, and ELISA was utilized for measuring soluble PD-1, PDL-2, and TIM3. Correlations have been detected across the percentage of T cells expressing Co-IRs (MFI) and different indicators in the blood, including ESR, high-sensitivity CRP (hsCRP), 28 joint disease activity scores (DAS28), and soluble PD-1/PDL-2/TIM3.

RESULTS

In RA patients, we recognized elevated levels of PD-1 (CD279), CTLA-4, and TIGIT in CD4+ T cells; TIGIT, HLA-DR, TIM3, and LAG3 in CD8+ T cells; and CD8+CD279+TIM3+, CD8+HLA-DR+CD38+ T cells. The following tests were revealed to be correlated with hsCRP: CD4/CD279 MFI, CD4/CD279%, CD4/TIM3%, CD8/TIM3%, CD8/TIM3 MFI, CD8/LAG3%, and CD8+HLA-DR+CD38+%. CD8/LAG3 and CD8/TIM3 MFIs are linked to ESR. DAS28-ESR and DAS28-CRP exhibited relationships with CD4/CD127 MFI, CD8/CD279%, and CD8/CD127 MFI, respectively. CD4+CD279+TIM3+% was correlated with DAS28-ESR (p = 0.0084, N = 46), DAS28-CRP (p = 0.007, N = 47), and hsCRP (p = 0.002, N = 56), respectively. In the serum of patients with RA, levels of soluble PD-1, PDL-2, and Tim3 were extremely elevated. CD4+ TIM3+% (p = 0.0089, N = 46) and CD8+ TIM3+% (p = 0.0305, N = 46) were correlated with sTIM3 levels; sPD1 levels were correlated with CD4+CD279+% (p < 0.0001, N = 31) and CD3+CD279+% (p = 0.0084, N = 30).

CONCLUSIONS

Co-IR expressions on CD4+ and CD8+ T cells, as well as soluble PD-1, PDL-2, and TIM3 levels, could function as indicators of disease activity and potentially play crucial roles in the pathogenesis of RA.

Single-cell insights into immune dysregulation in rheumatoid arthritis flare versus drug-free remission

Immune-mediated inflammatory diseases (IMIDs) are typically characterised by relapsing and remitting flares of inflammation. However, the unpredictability of disease flares impedes their study. Addressing this critical knowledge gap, we use the experimental medicine approach of immunomodulatory drug withdrawal in rheumatoid arthritis (RA) remission to synchronise flare processes allowing detailed characterisation. Exploratory mass cytometry analyses reveal three circulating cellular subsets heralding the onset of arthritis flare - CD45RO+PD1hi CD4+ and CD8+ T cells, and CD27+CD86+CD21- B cells - further characterised by single-cell sequencing. Distinct lymphocyte subsets including cytotoxic and exhausted CD4+ memory T cells, memory CD8+CXCR5+ T cells, and IGHA1+ plasma cells are primed for activation in flare patients. Regulatory memory CD4+ T cells (Treg cells) increase at flare onset, but with dysfunctional regulatory marker expression compared to drug-free remission. Significant clonal expansion is observed in T cells, but not B cells, after drug cessation; this is widespread throughout memory CD8+ T cell subsets but limited to the granzyme-expressing cytotoxic subset within CD4+ memory T cells. Based on our observations, we suggest a model of immune dysregulation for understanding RA flare, with potential for further translational research towards novel avenues for its treatment and prevention.

Cartilage destruction in early rheumatoid arthritis patients correlates with CD21-/low double-negative B cells

BACKGROUND

Involvement of B cells in the pathogenesis of rheumatoid arthritis (RA) is supported by the presence of disease-specific autoantibodies and the efficacy of treatment directed against B cells. B cells that express low levels of or lack the B cell receptor (BCR) co-receptor CD21, CD21-/low B cells, have been linked to autoimmune diseases, including RA. In this study, we characterized the CD21+ and CD21-/low B cell subsets in newly diagnosed, early RA (eRA) patients and investigated whether any of the B cell subsets were associated with autoantibody status, disease activity and/or joint destruction.

METHODS

Seventy-six eRA patients and 28 age- and sex-matched healthy donors were recruited. Multiple clinical parameters were assessed, including disease activity and radiographic joint destruction. B cell subsets were analysed in peripheral blood (PB) and synovial fluid (SF) using flow cytometry.

RESULTS

Compared to healthy donors, the eRA patients displayed an elevated frequency of naïve CD21+ B cells in PB. Amongst memory B cells, eRA patients had lower frequencies of the CD21+CD27+ subsets and CD21-/low CD27+IgD+ subset. The only B cell subset found to associate with clinical factors was the CD21-/low double-negative (DN, CD27-IgD-) cell population, linked with the joint space narrowing score, i.e. cartilage destruction. Moreover, in SF from patients with established RA, the CD21-/low DN B cells were expanded and these cells expressed receptor activator of the nuclear factor κB ligand (RANKL).

CONCLUSIONS

Cartilage destruction in eRA patients was associated with an expanded proportion of CD21-/low DN B cells in PB. The subset was also expanded in SF from established RA patients and expressed RANKL. Taken together, our results suggest a role for CD21-/low DN in RA pathogenesis.

Identification of potential ferroptosis key genes and immune infiltration in rheumatoid arthritis by integrated bioinformatics analysis

Objective

Ferroptosis is of vital importance in the development of Rheumatoid arthritis (RA). The purpose of this project is to clarify the potential ferroptosis-related genes, pathways, and immune infiltration in RA by bioinformatics analysis.

Methods

We acquired ferroptosis-related genes (FRGs) from Ferroptosis database (FerrDb). We obtained the Gene dataset of RA (GSE55235) from the Gene Expression Omnibus (GEO) Database, screened the differentially expressed genes (DEGs) in RA and control samples, and then took the intersection of it and FRGs. Aiming to construct the protein-protein interaction (PPI) networks of the FRGs-DEGs, STRING database and Cytoscape software 3.7.0 would be used. Furthermore, hub genes were identified by CytoNCA, a Cytoscape plug-in. The gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment of FRGs-DEGs were performed.

Results

We identified 34 FRGs-DEGs, including 7 upregulated and 27 downregulated genes by taking the intersection of the FRGs and DEGs. PPI analysis identified a total of 3 hub genes(VEGFA, PTGS2, and JUN). GO enrichment analyses and KEGG Pathway enrichment displayed that the FRGs-DEGs are involved in the response to oxidative stress and corticosteroid, heme binding, FoxO-signal pathway. Results of immune infiltration displayed that increased infiltration of T cells, while Macrophages M2 less may be related to the occurrence of RA.

Conclusion

The hub genes involved in ferroptosis in RA may be VEGFA, PTGS2, and JUN, which are mainly involved in FoxO-signal pathway. T cell, Mac, and plasma cells may be involved in the regulation of RA-joints-synovial-inflammation.

The roles of T cells in psoriasis

Psoriasis is a recurring inflammatory skin condition characterized by scaly, red patches on the skin. It affects approximately 3% of the US population and is associated with histological changes such as epidermal hyperplasia, increased blood vessel proliferation, and infiltration of leukocytes into the skin's dermis. T cells, which are classified into various subtypes, have been found to play significant roles in immune-mediated diseases, particularly psoriasis. This paper provides a review of the different T lymphocyte subtypes and their functions in psoriasis, as well as an overview of targeted therapies for treating psoriasis.

T Follicular Helper Cells in Tertiary Lymphoid Structure Contribute to Renal Fibrosis by IL-21

Tertiary lymphoid structure (TLS) represents lymphocyte clusters in non-lymphoid organs. The formation and maintenance of TLS are dependent on follicular helper T (TFH) cells. However, the role of TFH cells during renal TLS formation and the renal fibrotic process has not been comprehensively elucidated in chronic kidney disease. Here, we detected the circulating TFH cells from 57 IgAN patients and found that the frequency of TFH cells was increased in IgA nephropathy patients with renal TLS and also increased in renal tissues from the ischemic-reperfusion-injury (IRI)-induced TLS model. The inducible T-cell co-stimulator (ICOS) is one of the surface marker molecules of TFH. Remarkably, the application of an ICOS-neutralizing antibody effectively prevented the upregulation of TFH cells and expression of its canonical functional mediator IL-21, and also reduced renal TLS formation and renal fibrosis in IRI mice in vivo. In the study of this mechanism, we found that recombinant IL-21 could directly promote renal fibrosis and the expression of p65. Furthermore, BAY 11-7085, a p65 selective inhibitor, could effectively alleviate the profibrotic effect induced by IL-21 stimulation. Our results together suggested that TFH cells contribute to TLS formation and renal fibrosis by IL-21. Targeting the ICOS-signaling pathway network could reduce TFH cell infiltration and alleviate renal fibrosis.

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.

Pathologic and molecular insights in nodal T-follicular helper cell lymphomas

T-follicular helper (TFH) cells are one of the T-cell subsets with a critical role in the regulation of germinal center (GC) reactions. TFH cells contribute to the positive selection of GC B-cells and promote plasma cell differentiation and antibody production. TFH cells express a unique phenotype characterized by PD-1^hi, ICOS^hi, CD40L^hi, CD95^hi, CTLA^hi, CCR7^lo, and CXCR5^hi . Three main subtypes of nodal TFH lymphomas have been described: 1) angioimmunoblastic-type, 2) follicular-type, and 3) not otherwise specified (NOS). The diagnosis of these neoplasms can be challenging, and it is rendered based on a combination of clinical, laboratory, histopathologic, immunophenotypic, and molecular findings. The markers most frequently used to identify a TFH immunophenotype in paraffin-embedded tissue sections include PD-1, CXCL13, CXCR5, ICOS, BCL6, and CD10. These neoplasms feature a characteristic and similar, but not identical, mutational landscape with mutations in epigenetic modifiers (TET2, DNMT3A, IDH2), RHOA, and T-cell receptor signaling genes. Here, we briefly review the biology of TFH cells and present a summary of the current pathologic, molecular, and genetic features of nodal lymphomas. We want to highlight the importance of performing a consistent panel of TFH immunostains and mutational studies in TCLs to identify TFH lymphomas.

Human B-cell subset identification and changes in inflammatory diseases

Our understanding of the B-cell subsets found in human blood and their functional significance has advanced greatly in the past decade. This has been aided by the evolution of high dimensional phenotypic tools such as mass cytometry and single-cell RNA sequencing which have revealed heterogeneity in populations that were previously considered homogenous. Despite this, there is still uncertainty and variation between studies as to how B-cell subsets are identified and named. This review will focus on the most commonly encountered subsets of B cells in human blood and will describe gating strategies for their identification by flow and mass cytometry. Important changes to population frequencies and function in common inflammatory and autoimmune diseases will also be described.

Dynamics of circulating follicular helper T cell subsets and follicular regulatory T cells in rheumatoid arthritis patients according to HLA-DRB1 locus

B cells, follicular helper T (Tfh) cells and follicular regulatory T (Tfr) cells are part of a circuit that may play a role in the development or progression of rheumatoid arthritis (RA). With the aim of providing further insight into this topic, here we evaluated the frequency of different subsets of Tfh and Tfr in untreated and long-term treated RA patients from a cohort of Argentina, and their potential association with particular human leukocyte antigen (HLA) class-II variants and disease activity. We observed that the frequency of total Tfh cells as well as of particular Tfh subsets and Tfr cells were increased in seropositive untreated RA patients. Interestingly, when analyzing paired samples, the frequency of Tfh cells was reduced in synovial fluid compared to peripheral blood, while Tfr cells levels were similar in both biological fluids. After treatment, a decrease in the CCR7^loPD1^hi Tfh subset and an increase in the frequency of Tfr cells was observed in blood. In comparison to healthy donors, seropositive patients with moderate and high disease activity exhibited higher frequency of Tfh cells while seropositive patients with low disease activity presented higher Tfr cell frequency. Finally, we observed that HLA-DRB1*09 presence correlated with higher frequency of Tfh and Tfr cells, while HLA-DRB1*04 was associated with increased Tfr cell frequency. Together, our results increase our knowledge about the dynamics of Tfh and Tfr cell subsets in RA, showing that this is altered after treatment.

Aberrant B Cell Signaling in Autoimmune Diseases

Aberrant B cell signaling plays a critical in role in various systemic and organ-specific autoimmune diseases. This is supported by genetic evidence by many functional studies in B cells from patients or specific animal models and by the observed efficacy of small-molecule inhibitors. In this review, we first discuss key signal transduction pathways downstream of the B cell receptor (BCR) that ensure that autoreactive B cells are removed from the repertoire or functionally silenced. We provide an overview of aberrant BCR signaling that is associated with inappropriate B cell repertoire selection and activation or survival of peripheral B cell populations and plasma cells, finally leading to autoantibody formation. Next to BCR signaling, abnormalities in other signal transduction pathways have been implicated in autoimmune disease. These include reduced activity of several phosphates that are downstream of co-inhibitory receptors on B cells and increased levels of BAFF and APRIL, which support survival of B cells and plasma cells. Importantly, pathogenic synergy of the BCR and Toll-like receptors (TLR), which can be activated by endogenous ligands, such as self-nucleic acids, has been shown to enhance autoimmunity. Finally, we will briefly discuss therapeutic strategies for autoimmune disease based on interfering with signal transduction in B cells.

Inflammatory Cytokine-Neutralizing Antibody Treatment Prevented Increases in Follicular Helper T Cells and Follicular Regulatory T Cells in a Mouse Model of Arthritis

Background

Follicular T helper (TFH) and follicular regulatory T (TFR) cells play important roles in humoral immunity. Nevertheless, their significance in rheumatoid arthritis (RA) pathogenesis has not been fully elucidated. As an important treatment strategy, the effect of inflammatory factor-neutralizing antibodies on TFH and TFR in RA remains unclear.

Methods

We used the collagen-induced arthritis (CIA) mouse model to illustrate the quantity and functional changes in TFH and TFR cells. The changes of plasmablast, TFH and TFR cells in the spleen and peripheral blood of CIA mice were analyzed by flow cytometry. The levels of TFH and TFR and their functional subsets in the spleen after anti-inflammatory antibody treatment were analyzed and compared. The functional changes of TFH and TFR in CIA mice before and after treatment were detected by in vitro culture experiments.

Results

Plasmablast levels were increased in CIA spleen and peripheral blood and both TFH and TFR cell levels were upregulated. TFH and TFR cells were decreased significantly after the anti-inflammatory antibody treatment. TIGIT⁺ and TIGIT⁺CD226⁻ TFH cells in CIA mouse spleen were elevated and PD-1 and ICOS expression on spleen TFH and TFR cells was increased. Both the ability of TFH cells to secrete IL-21 and aid B cells and the ability of TFR cells to secrete IL-10 and inhibit TFH cells were enhanced in the CIA mice. After antibody treatment, the cell subsets and functions were recovered.

Conclusion

Germinal center TFH and TFR cells were increased and their functions were enhanced. With inflammatory factor-neutralizing antibody treatment, TFH and TFR subsets and their functions returned to normal. These findings provide important information on the dynamics of humoral immune-related cell subsets in RA and the effects of treatment on them.

Immunomodulatory role of T helper cells in rheumatoid arthritis : a comprehensive research review

Rheumatoid arthritis (RA) is an autoimmune disease that involves T and B cells and their reciprocal immune interactions with proinflammatory cytokines. T cells, an essential part of the immune system, play an important role in RA. T helper 1 (Th1) cells induce interferon-γ (IFN-γ), tumour necrosis factor-α (TNF-α), and interleukin (IL)-2, which are proinflammatory cytokines, leading to cartilage destruction and bone erosion. Th2 cells primarily secrete IL-4, IL-5, and IL-13, which exert anti-inflammatory and anti-osteoclastogenic effects in inflammatory arthritis models. IL-22 secreted by Th17 cells promotes the proliferation of synovial fibroblasts through induction of the chemokine C-C chemokine ligand 2 (CCL2). T follicular helper (Tfh) cells produce IL-21, which is key for B cell stimulation by the C-X-C chemokine receptor 5 (CXCR5) and coexpression with programmed cell death-1 (PD-1) and/or inducible T cell costimulator (ICOS). PD-1 inhibits T cell proliferation and cytokine production. In addition, there are many immunomodulatory agents that promote or inhibit the immunomodulatory role of T helper cells in RA to alleviate disease progression. These findings help to elucidate the aetiology and treatment of RA and point us toward the next steps.

Cite this article: Bone Joint Res 2022;11(7):426–438.

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.

The activity level of follicular helper T cells in the peripheral blood of osteosarcoma patients is associated with poor prognosis

Osteosarcoma (OS) is solid tumors with high malignancy and incidence starting in the bones. OS pathogenesis has been proved to be closely associated with immune imbalance, and follicular helper T cells (Tfh) significantly affect host humoral immune homeostasis. However, there are few reports on the effect of Tfh cell activation on the prognosis of OS patients. Hence, this investigation on the changes in the proportion of peripheral blood Tfh cells in OS patients, and the relationship between their activity level and OS prognosis. We collected peripheral blood from patients with OS, benign bone tumor (BT group) and healthy subjects (Healthy group), respectively. The number of CD4⁺CXCR5⁺ Tfh cell in peripheral blood was measured by flow cytometry and correlation analysis between its activity and OS clinicopathological characteristics was carried out. The data showed that in comparison with the BT and Healthy groups, higher proportion and activation level of peripheral blood CD4⁺CXCR5⁺ Tfh cells in CD4⁺ T cells were found in the OS group. In OS patients, increases of the proportion and activity level of Tfh cells were associated with poorly differentiated OS and tumor metastasis. Additionally, Kaplan-Meier and Cox regression analysis showed a longer overall survival in patients with low proportion of peripheral blood CD4⁺CXCR5⁺ Tfh cells in CD4⁺ T cells, and their activation level may be a prognostic factor in OS patients. In conclusion, peripheral blood CD4⁺CXCR5⁺ Tfh cell activation in OS patients was associated with a poor prognosis. This study provided ideas for improving the clinical treatment of OS patients.

Mature naive B cells regulate the outcome of murine acute graft-versus-host disease in an IL-10 independent manner

Graft-versus-host disease (GVHD) is the main complication of bone marrow transplantation (BMT). T CD4+ lymphocytes are the main effector cells for disease development but other cell types can determine disease outcome through cytokine production and antigen presentation. B cells are abundant in BMT products and are involved in chronic GVHD immunopathogenesis. However, their role in acute GVHD is still unclear. Here, we studied the role of donor resting B cells in a model of acute GVHD. Animals receiving transplants depleted of B cells presented a more severe disease, indicating a protective role for B cells. Mice transplanted with IL-10 KO B cells developed GVHD as severe as those receiving WT B cells. Besides that, mice transplanted with MHC II deficient B cells and as so, unable to present antigen to CD4+ T cells, developed as severe GVHD as animals transplanted without B cells. This result suggests that protection provided by mature naive B cells depends on antigen presentation and not IL-10 production by B cells. In the absence of donor B cells, transplanted mice exhibited disorganized lymphoid splenic tissue. Additionally, donor B cell depletion diminished the follicular T (Tfh)/T effector (Teff) ratio suggesting that protection was correlated with a shift to Tfh differentiation, reducing the number of effector T cells. Importantly, the Tfh/Teff shift impacts disease outcome since observed proinflammatory cytokine levels and tissue damage in target organs were consistent with disease protection. The role of transplanted B cells in the outcome of BMT and the development of acute GVHD should be carefully studied, since these cells are abundant in BMT products and are potent modulator and effector cells in allogeneic response. Extended Abstract Background: B cells are widely known for their ability to produce antibodies. In addition, B cells can act efficiently as antigen-presenting cells, implying the mutual regulation of both T and B lymphocyte subsets. T cell help for B cells has been known for more than 50 years; however, B cell help for T cells, especially regarding the modulation of follicular and regulatory phenotypes, had only lately been explored. Here, we studied the role of resting B cells in a model of systemic inflammatory disease mediated by T cells, graft-versus-host disease (GVHD), which is the main complication of allogeneic bone marrow transplantation. Objetive: The objective of this paper is to investigate the role of donor B cells in acute Graft-versus-Host Disease.

STUDY DESIGN

To investigate the role of donor B cells in aGVHD, we used a full MHC-mismatched bone marrow transplantation model. We infused C57BL/6 BM cells along with splenocytes depleted or not of B220⁺ cells into lethally irradiated BALB/c mice. We also used B cells from IL-10 KO mice to investigate the role of IL-10 produced by donor B cells and B cells from mice which cannot express MHC-II (CIITA KO) to investigate the role of cognate interaction between donor B and T cells.

RESULTS

Animals receiving transplants depleted of B cells presented a more severe disease, showing the existence of B cell-dependent protection. This protection was dependent on the T cell-B cell cognate interaction but not on IL-10 or Treg induction. In the absence of donor B cells, transplanted mice exhibited fewer GCs and a lower follicular T (Tfh)/T effector (Teff) ratio than mice transplanted in the presence of B cells. Protection was correlated with a shift to Tfh differentiation, reducing the number of effector cells. Importantly, the Tfh/Teff shift impacts disease outcome with less T cell-mediated disease due to more B cell-dependent Tfh generation with fewer effector T cells and lower proinflammatory cytokine levels detected in target organs.

CONCLUSION

We show that B-cell depleted bone marrow transplantation leads to a more severe disease, with earlier mortality related to increased organ damage. Such differences depend on cognate interactions between T cells and B cells, are IL-10 independent and are related to a shift in the differentiation of lymphocytes from the follicular helper phenotype to the effector phenotype. Therefore, Teffs, which are circulating cells, become relatively more numerous and can reach and damage the target tissues. These results point to caution in the early posttransplantation elimination of donor B cells. It is not a matter of eliminating only antibody-forming cells or cells that mediate Tfh generation but of B cells, which interact and modulate T cell activity, impacting a disease that is not antibody mediated.

Acazicolcept (ALPN-101), a dual ICOS/CD28 antagonist, demonstrates efficacy in systemic sclerosis preclinical mouse models

Background

Uncontrolled immune response with T cell activation has a key role in the pathogenesis of systemic sclerosis (SSc), a disorder that is characterized by generalized fibrosis affecting particularly the lungs and skin. Costimulatory molecules are key players during immune activation, and recent evidence supports a role of CD28 and ICOS in the development of fibrosis. We herein investigated the efficacy of acazicolcept (ALPN-101), a dual ICOS/CD28 antagonist, in two complementary SSc-related mouse models recapitulating skin fibrosis, interstitial lung disease, and pulmonary hypertension.

Methods

Expression of circulating soluble ICOS and skin-expressed ICOS was investigated in SSc patients. Thereafter, acazicolcept was evaluated in the hypochlorous acid (HOCL)-induced dermal fibrosis mouse model and in the Fra-2 transgenic (Tg) mouse model. In each model, mice received 400 μg of acazicolcept or a molar-matched dose of an Fc control protein twice a week for 6 weeks. After 6 weeks, skin and lung were evaluated.

Results

ICOS was significantly increased in the sera from SSc patients and in SSc skin biopsies as compared to samples from healthy controls. Similar body weight changes were observed between Fc control and acazicolcept groups in both HOCL and Fra-2 Tg mice suggesting a good tolerance of acazicolcept treatment. In mice challenged with HOCL, acazicolcept induced a significant decrease in dermal thickness, collagen content, myofibroblast number, and inflammatory infiltrates characterized by B cells, T cells, neutrophils, and macrophages. In the Fra-2 Tg mouse model, acazicolcept treatment reduced lung collagen content, fibrillar collagen, histological fibrosis score, and right ventricular systolic pressure (RVSP). A reduction in frequency of CD4+ and T effector memory cells and an increase in the percentage of CD4+ T naïve cells in spleen and lung of acazicolcept-treated Fra-2 Tg mice was observed as compared to Fc control-treated Fra-2 Tg mice. Moreover, acazicolcept reduced CD69 and PD-1 expression on CD4+ T cells from the spleen and the lung. Target engagement by acazicolcept was demonstrated by blockade of CD28 and ICOS detection by flow cytometry in treated mice.

Conclusions

Our results confirm the importance of costimulatory molecules in inflammatory-driven fibrosis. Our data highlight a key role of ICOS and CD28 in SSc. Using complementary models, we demonstrated that dual ICOS/CD28 blockade by acazicolcept decreased dermal and pulmonary fibrosis and alleviated pulmonary hypertension. These results pave the way for subsequent research on ICOS/CD28-targeted therapies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02709-2.

B Cells in Rheumatoid Arthritis：Pathogenic Mechanisms and Treatment Prospects

Rheumatoid arthritis (RA) is a common, chronic, systemic autoimmune disease, and its clinical features are the proliferation of joint synovial tissue, the formation of pannus and the destruction of cartilage. The global incidence of RA is about 1%, and it is more common in women. The basic feature of RA is the body’s immune system disorders, in which autoreactive CD4⁺T cells, pathogenic B cells, M1 macrophages, inflammatory cytokines, chemokines and autoantibodies abnormally increase in the body of RA patients B cell depletion therapy has well proved the important role of B cells in the pathogenesis of RA, and the treatment of RA with B cells as a target has also been paid more and more attention. Although the inflammatory indicators in RA patients receiving B-cell depletion therapy have been significantly improved, the risk of infection and cancer has also increased, which suggests that we need to deplete pathogenic B cells instead of all B cells. However, at present we cannot distinguish between pathogenic B cells and protective B cells in RA patients. In this review, we explore fresh perspectives upon the roles of B cells in the occurrence, development and treatment of RA.

Association of Circulating T Follicular Helper Cells With Idiopathic Optic Neuritis and Neuromyelitis Optica Spectrum Disorders

Background: T follicular helper cells (Tfh cells) play an important role in activating B lymphocytes and may associate with idiopathic Optic Neuritis (ON) and Neuromyelitis Optica Spectrum Disorders (NMOSD).

Objective: This study aimed to examine the potential role of Tfh cells in pathogenesis of idiopathic ON and NMOSD.

Methods: Circulating CD4⁺CXCR5⁺ and CD4⁺CXCR5⁺PD-1⁺ cells in 46 idiopathic ON and 68 NMOSD patients as well as 28 healthy controls were examined by flow cytometry before treatment. Serum AQP4 antibody, Expended Disability Status Scale (EDSS) and Visual Outcome Scale (VOS) were detected before and after treatment.

Results: The percentages of circulating CD4⁺CXCR5⁺ and CD4⁺CXCR5⁺PD-1⁺Tfh cells in CD4⁺ cells (%) were significantly increased in idiopathic ON and NMOSD compared with those of healthy controls (p < 0.01). No significant difference of Tfh cells in blood and cerebral spinal fluid (CSF) was found between ON and NMOSD patients. The percentages of CSF, CD4⁺, CXCR5⁺, and CD4⁺CXCR5⁺PD-1⁺ cells in CD4⁺ cells (%) were positively correlated with those of the blood (r = 0.5781, r = 0.6079, p = 0.0076, and p = 0.0045, respectively). EDSS scores of NMOSD group were higher than those of ON group and the time course of NMOSD patients was longer than that of ON patients (p < 0.01). After methylprednisolone treatment, both EDSS and VOS scores were significantly decreased at discharge compared with before treatment (p < 0.01). There was no significant correlation among Tfh cell percentages in CD4⁺ cells, CSF leukocytes, CSF protein, annual recurrence rate, EDSS and VOS scores between two groups (p > 0.05).

Conclusion: The Circulating T follicular helper cells were increased in both idiopathic ON and NMOSD.

The Germinal Center Milieu in Rheumatoid Arthritis: The Immunological Drummer or Dancer?

Rheumatoid Arthritis (RA) is a chronic autoimmune disease characterized by joint inflammation, affecting approximately 1% of the general population. To alleviate symptoms and ameliorate joint damage, chronic use of immunosuppressives is needed. However, these treatments are only partially effective and may lead to unwanted side effects. Therefore, a more profound understanding of the pathophysiology might lead to more effective therapies, or better still, a cure. The presence of autoantibodies in RA indicates that B cells might have a pivotal role in the disease. This concept is further supported by the fact that a diverse antibody response to various arthritis-related epitopes is associated with arthritis development. In this context, attention has focused in recent years on the role of Germinal Centers (GCs) in RA. Since GCs act as the main anatomic location of somatic hypermutations, and, thus, contributing to the diversity and specificity of (auto) antibodies, it has been speculated that defects in germinal center reactions might be crucial in the initiation and maintenance of auto-immune events. In this paper, we discuss current evidence that various processes within GCs can result in the aberrant production of B cells that possess autoreactive properties and might result in the production of RA related autoantibodies. Secondly, we discuss various (pre-)clinical studies that have targeted various GC processes as novel therapies for RA treatment.

Adenosine and Inflammation: Here, There and Everywhere

Adenosine is a ubiquitous endogenous modulator with the main function of maintaining cellular and tissue homeostasis in pathological and stress conditions. It exerts its effect through the interaction with four G protein-coupled receptor (GPCR) subtypes referred as A1, A2A, A2B, and A3 adenosine receptors (ARs), each of which has a unique pharmacological profile and tissue distribution. Adenosine is a potent modulator of inflammation, and for this reason the adenosinergic system represents an excellent pharmacological target for the myriad of diseases in which inflammation represents a cause, a pathogenetic mechanism, a consequence, a manifestation, or a protective factor. The omnipresence of ARs in every cell of the immune system as well as in almost all cells in the body represents both an opportunity and an obstacle to the clinical use of AR ligands. This review offers an overview of the cardinal role of adenosine in the modulation of inflammation, showing how the stimulation or blocking of its receptors or agents capable of regulating its extracellular concentration can represent promising therapeutic strategies for the treatment of chronic inflammatory pathologies, neurodegenerative diseases, and cancer.

Circulating CD4+ FoxP3- CXCR5- CXCR3+ PD-1hi cells are elevated in active rheumatoid arthritis and reflect the severity of the disease

OBJECTIVE

To examine the expression and clinical significance of circulating CD4⁺  FoxP3^-  CXCR5^-  CXCR3⁺  PD-1^hi cells in rheumatoid arthritis (RA).

METHODS

CD4⁺  FoxP3^-  CXCR5^-  CXCR3⁺  PD-1^hi cells in peripheral blood of 35 patients with active RA, 17 with RA in stable remission, and 24 healthy controls were analyzed by flow cytometry. Serum IgG and circulating plasmablast percentages were measured and correlations with CD4⁺  FoxP3^-  CXCR5^-  CXCR3⁺  PD-1^hi cells were systematically analyzed. Disease Activity Scale 28 (DAS28) scores were also calculated and correlation analysis with CD4⁺  FoxP3^-  CXCR5^-  CXCR3⁺  PD-1^hi cells was conducted. The levels of CD4⁺  FoxP3^-  CXCR5^-  CXCR3⁺  PD-1^hi cells were compared before and after disease-modifying anti-rheumatic drug treatment. Cytokine levels in plasma and cytokine secretion in CD4 cells were measured and their correlations with CD4⁺  FoxP3^-  CXCR5^-  CXCR3⁺  PD-1^hi cells were further analyzed.

RESULTS

The levels of CD4⁺  FoxP3^-  CXCR5^-  CXCR3⁺  PD-1^hi cells in the peripheral blood of patients with active RA were significantly increased compared with healthy controls. CD4⁺  FoxP3^-  CXCR5^-  CXCR3⁺  PD-1^hi cells in patients with active RA were positively correlated with serum IgG and DAS28 scores. CD4⁺  FoxP3^-  CXCR5^-  CXCR3⁺  PD-1^hi cells were significantly decreased in patients after treatment. Plasma interleukin-10 concentrations and interleukin-10-positive CD4 cell percentages were significantly positively correlated with CD4⁺  FoxP3^-  CXCR5^-  CXCR3⁺  PD-1^hi cell levels.

CONCLUSION

Circulating CD4⁺  FoxP3^-  CXCR5^-  CXCR3⁺  PD-1^hi cells in patients with active RA are increased and could reflect the severity of the disease, which may play a potential role in the pathogenesis of RA.

First-in-human study of the safety, tolerability, pharmacokinetics, and pharmacodynamics of ALPN-101, a dual CD28/ICOS antagonist, in healthy adult subjects

ALPN-101 (ICOSL vIgD-Fc) is an Fc fusion protein of a human inducible T cell costimulatory ligand (ICOSL) variant immunoglobulin domain (vIgD) designed to inhibit the cluster of differentiation 28 (CD28) and inducible T cell costimulator (ICOS) pathways simultaneously. A first-in-human study evaluated the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of ALPN-101 in healthy adult subjects. ALPN-101 was generally well-tolerated with no evidence of cytokine release, clinically significant immunogenicity, or severe adverse events following single subcutaneous (SC) doses up to 3 mg/kg or single intravenous (IV) doses up to 10 mg/kg or up to 4 weekly IV doses of up to 1 mg/kg. ALPN-101 exhibited a dose-dependent increase in exposure with an estimated terminal half-life of 4.3-8.6 days and SC bioavailability of 60.6% at 3 mg/kg. Minimal to modest accumulation in exposure was observed with repeated IV dosing. ALPN-101 resulted in a dose-dependent increase in maximum target saturation and duration of high-level target saturation. Consistent with its mechanism of action, ALPN-101 inhibited cytokine production in whole blood stimulated by Staphylococcus aureus enterotoxin B ex vivo, as well as antibody responses to keyhole limpet hemocyanin immunization, reflecting immunomodulatory effects upon T cell and T-dependent B cell responses, respectively. In conclusion, ALPN-101 was well-tolerated in healthy subjects with dose-dependent PK and PD consistent with the known biology of the CD28 and ICOS costimulatory pathways. Further clinical development of ALPN-101 in inflammatory and/or autoimmune diseases is therefore warranted.

Helper T Cells in Idiopathic Membranous Nephropathy

Idiopathic membranous nephropathy (IMN) is an autoimmune disease in which the immune system produces an antibody response to its own antigens due to impaired immune tolerance. Although antibodies are derived from plasma cells differentiated by B cells, the T-B cells also contribute a lot to the immune system. In particular, the subsets of helper T (Th) cells, including the dominant subsets such as Th2, Th17, and follicular helper T (Tfh) cells and the inferior subsets such as regulatory T (Treg) cells, shape the immune imbalance of IMN and promote the incidence and development of autoimmune responses. After reviewing the physiological knowledge of various subpopulations of Th cells and combining the existing studies on Th cells in IMN, the role model of Th cells in IMN was explained in this review. Finally, the existing clinical treatment regimens for IMN were reviewed, and the importance of the therapy for Th cells was highlighted.

A review of signaling and transcriptional control in T follicular helper cell differentiation

T follicular helper (Tfh) cells are a critical component of adaptive immunity and assist in optimal Ab-mediated defense. Multiple effector functions of Tfh support germinal center B cell survival, Ab class switching, and plasma cell maturation. In the past 2 decades, the phenotype and functional characteristics of GC Tfh have been clarified allowing for robust studies of the Th subset including activation signals and environmental cues controlling Tfh differentiation and migration during an immune response. A unique, 2-step differentiation process of Tfh has been proposed but the mechanisms underlying transition between unstable Tfh precursors and functional mature Tfh remain elusive. Likewise, newly identified transcriptional regulators of Tfh development have not yet been incorporated into our understanding of how these cells might function in disease. Here, we review the signals and downstream transcription factors that shape Tfh differentiation including what is known about the epigenetic processes that maintain Tfh identity. It is proposed that further evaluation of the stepwise differentiation pattern of Tfh will yield greater insights into how these cells become dysregulated in autoimmunity.

Alcohol Consumption in Rheumatoid Arthritis: A Path through the Immune System

Benefits and harms of different components of human diet have been known for hundreds of years. Alcohol is one the highest consumed, abused, and addictive substances worldwide. Consequences of alcohol abuse are increased risks for diseases of the cardiovascular system, liver, and nervous system, as well as reduced immune system function. Paradoxically, alcohol has also been a consistent protective factor against the development of autoimmune diseases such as type 1 diabetes, multiple sclerosis, systemic lupus erythematosus, and rheumatoid arthritis (RA). Here, we focused on summarizing current findings on the effects of alcohol, as well as of its metabolites, acetaldehyde and acetate, on the immune system and RA. Heavy or moderate alcohol consumption can affect intestinal barrier integrity, as well as the microbiome, possibly contributing to RA. Additionally, systemic increase in acetate negatively affects humoral immune response, diminishing TFH cell as well as professional antigen-presenting cell (APC) function. Hence, alcohol consumption has profound effects on the efficacy of vaccinations, but also elicits protection against autoimmune diseases. The mechanism of alcohol's negative effects on the immune system is multivariate. Future studies addressing alcohol and its metabolite acetate's effect on individual components of the immune system remains crucial for our understanding and development of novel therapeutic pathways.

MicroRNA Expression Differences in Blood-Derived CD19+ B Cells of Methotrexate Treated Rheumatoid Arthritis Patients

Rheumatoid arthritis (RA) is a complex disease with a wide range of underlying susceptibility factors. Recently, dysregulation of microRNAs (miRNAs) in RA have been reported in several immune cell types from blood. However, B cells have not been studied in detail yet. Given the autoimmune nature of RA with the presence of autoantibodies, CD19+ B cells are a key cell type in RA pathogenesis and alterations in CD19+ B cell subpopulations have been observed in patient blood. Therefore, we aimed to reveal the global miRNA repertoire and to analyze miRNA expression profile differences in homogenous RA patient phenotypes in blood-derived CD19+ B cells. Small RNA sequencing was performed on CD19+ B cells of newly diagnosed untreated RA patients (n=10), successfully methotrexate (MTX) treated RA patients in remission (MTX treated RA patients, n=18) and healthy controls (n=9). The majority of miRNAs was detected across all phenotypes. However, significant expression differences between MTX treated RA patients and controls were observed for 27 miRNAs, while no significant differences were seen between the newly diagnosed patients and controls. Several of the differentially expressed miRNAs were previously found to be dysregulated in RA including miR-223-3p, miR-486-3p and miR-23a-3p. MiRNA target enrichment analysis, using the differentially expressed miRNAs and miRNA-target interactions from miRTarBase as input, revealed enriched target genes known to play important roles in B cell activation, differentiation and B cell receptor signaling, such as STAT3, PRDM1 and PTEN. Interestingly, many of those genes showed a high degree of correlated expression in CD19+ B cells in contrast to other immune cell types. Our results suggest important regulatory functions of miRNAs in blood-derived CD19+ B cells of MTX treated RA patients and motivate for future studies investigating the interactive mechanisms between miRNA and gene targets, as well as the possible predictive power of miRNAs for RA treatment response.

Frontiers of Autoantibodies in Autoimmune Disorders: Crosstalk Between Tfh/Tfr and Regulatory B Cells

Balance of Tfh/Tfr cell is critically important for the maintenance of immune tolerance, as evidenced by the fact that T follicular helper (Tfh) cells are central to the autoantibodies generation through providing necessary help for germinal center (GC) B cells, whereas T follicular regulatory (Tfr) cells significantly inhibit autoimmune inflammation process through restraining Tfh cell responses. However, signals underlying the regulation of Tfh and Tfr cells are largely undefined. Regulatory B cells (Bregs) is a heterogeneous subpopulation of B cells with immunosuppressive function. Considerable advances have been made in their functions to produce anti‐inflammatory cytokines and to regulate Th17, Th1, and Treg cells in autoimmune diseases. The recent identification of their correlations with dysregulated Tfr/Tfh cells and autoantibody production makes Bregs an important checkpoint in GC response. Bregs exert profound impacts on the differentiation, function, and distribution of Tfh and Tfr cells in the immune microenvironment. Thus, unraveling mechanistic information on Tfh-Breg and Tfr-Breg interactions will inspire novel implications for the establishment of homeostasis and prevention of autoantibodies in diverse diseases. This review summarizes the dysregulation of Tfh/Tfr cells in autoimmune diseases with a focus on the emerging role of Bregs in regulating the balance between Tfh and Tfr cells. The previously unsuspected crosstalk between Bregs and Tfh/Tfr cells will be beneficial to understand the cellular mechanisms of autoantibody production and evoke a revolution in immunotherapy for autoimmune diseases.

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.

Enhanced IgG1 -mediated antibody response towards thymus-dependent immunization in CXCR1-deficient mice

Background

Chemokine receptors and their corresponding ligands are key players of immunity by regulation of immune cell differentiation and migration. CXCR1 is a high‐affinity receptor for CXCL8. Differential expression of CXCR1 is associated with a variety of human pathologies including cancer and inflammatory diseases. While various studies have highlighted the importance of CXCR1‐mediated CXCL8‐sensing for neutrophil trafficking and function, its role in B‐cell responses remains unsolved. Therefore, our aim was to investigate innate and adaptive antibody responses in CXCR1‐deficient mice.

Methods

Cell populations of the spleen and the peritoneal cavity were identified and quantified via flow cytometry. To investigate thymus‐independent (TI) and thymus‐dependent (TD) antibody responses, mice were immunized intraperitoneally with TNP‐Ficoll, Pneumovax23, and TNP‐Chicken Gamma Globulin. Mice were bled before as well as 7 and 14 days after vaccination to collect serum. Serum antibody levels overtime were analyzed according to their specificity by enzyme‐linked immunosorbent assay. B‐1 cell functionality was examined by IL‐5/IL‐5Rα‐dependent stimulation of peritoneal and splenic cells in vitro. To analyze CXCR1/2‐expression, CD19⁺ splenocytes were enriched by magnetic‐activated cell sorting before isolation of total RNA contents, followed by reverse transcription and real‐time polymerase chain reaction.

Results

The distribution of natural B‐1 cell populations was disturbed in the absence of CXCR1, while their responsiveness towards TI antigens and in vitro stimulation remained functional. Besides, CXCR1‐deficiency was accompanied by increased frequencies of follicular B‐2 cells in the spleen. Interestingly, these mice produced elevated levels of antigen‐specific IgG₁ upon TD immunization and harbored a significantly enlarged proportion of CXCR5‐expressing T helper (H) cells. CXCR1‐expression was detectable in CD19⁺ splenocytes derived from wild‐type, but not CXCR1‐deficient mice.

Conclusion

Our data demonstrate a previously unknown relevance of CXCR1 for the production of specific IgG₁ in response to vaccination. These findings identify CXCR1 as a promising candidate for future studies on the regulation of adaptive antibody responses.

Autoreactive T cells in pemphigus: perpetrator and target

Pemphigus vulgaris (PV) is an autoimmune blistering disease, in which autoantibodies against epidermal cadherins, such as desmoglein (Dsg)1 and Dsg3, lead to the development of blisters and erosions on the skin and mucous membranes. Autoreactive CD4+ T cells are essential for the induction and perpetuation of the disease by interaction with B cells producing autoantibodies. PV has a strong genetic association with certain human leucocyte antigen (HLA) alleles with HLA-DRB1*04:02 and LA-DQB1*05:03 being the most prevalent in patients. Recently, genome-wide association studies have provided a new approach to identify single nucleotide polymorphisms, alongside the known association with HLA alleles. Loss of tolerance against Dsgs and other autoantigens is a critical event in the pathogenesis of PV. Epitope spreading contributes to the progression of PV, leading to an extension of the Dsg-specific autoimmune response to other molecular epitopes of autoantigens, such as desmocollins or muscarinic receptors. Alterations in CD4+CD25+ FoxP3+ regulatory T cells are thought to contribute to the development of PV representing a suitable target for therapeutic interventions. Several CD4+ T-cell subsets and cytokines are involved in the pathogenesis of PV, while Th2 cells are the extensively studied population. Recently, other T cell subsets like T follicular helper cells and Th17 have gained attention as new potential players in PV pathogenesis. The involvement of local autoantibody production in the lesional skin of PV patients in tertiary lymphoid organs is currently discussed but not yet clarified. In this study, we reviewed the current knowledge about the development, characteristics and function of autoreactive T cells in pemphigus and present current new T cell-targeted therapeutic approaches.

Targeting co-stimulatory molecules in autoimmune disease

Therapeutic targeting of immune checkpoints has garnered significant attention in the area of cancer immunotherapy, in which efforts have focused in particular on cytotoxic T lymphocyte antigen 4 (CTLA4) and PD1, both of which are members of the CD28 family. In autoimmunity, these same pathways can be targeted to opposite effect: to curb the over-exuberant immune response. The CTLA4 checkpoint serves as an exemplar, whereby CTLA4 activity is blocked by antibodies in cancer immunotherapy and augmented by the provision of soluble CTLA4 in autoimmunity. Here, we review the targeting of co-stimulatory molecules in autoimmune diseases, focusing in particular on agents directed at members of the CD28 or tumour necrosis factor receptor families. We present the state of the art in co-stimulatory blockade approaches, including rational combinations of immune inhibitory agents, and discuss the future opportunities and challenges in this field.

Therapeutic Cytokine Inhibition Modulates Activation and Homing Receptors of Peripheral Memory B Cell Subsets in Rheumatoid Arthritis Patients

Memory B cells have known to play an important role in the pathogenesis of rheumatoid arthritis (RA). With the emergence of B cell-targeted therapies, the modulation of memory B cells appears to be a key therapeutic target. Human peripheral memory B cells can be distinguished based on the phenotypic expression of CD27 and IgD, characterizing the three major B cell subpopulations: CD27+IgD+ pre-switch, CD27+IgD- post-switch, and CD27-IgD- double-negative memory B cells. We evaluated different memory cell populations for activation markers (CD95 and Ki-67) and chemokine receptors (CXCR3 and 4) expressing B cells in active RA, as well as under IL6-R blockade by tocilizumab (TCZ) and TNF-α blockade by adalimumab (ADA). Memory B cells were phenotypically analyzed from RA patients at baseline, week 12, and week 24 under TCZ or ADA treatment, respectively. Using flow cytometry, surface expression of CD95, intracellular Ki-67, and surface expressions of CXCR3 and CXCR4 were determined. Compared with healthy donors (n = 40), the phenotypic analysis of RA patients (n = 80) demonstrated that all three types of memory B cells were activated in RA patients. Surface and intracellular staining of B cells showed a significantly higher percentage of CD95+ (p < 0.0001) and Ki-67+ (p < 0.0001) cells, with numerically altered CXCR3+ and CXCR4+ cells in RA. CD95 and Ki-67 expressions were highest in post-switch memory B cells, whereas CD19+CXCR3+ and CD19+CXCR4+ expressing cells were substantially higher in the pre-switch compartment. In all subsets of the memory B cells, in vivo IL-6R, and TNF-α blockade significantly reduced the enhanced expressions of CD95 and Ki-67. Based on our findings, we conclude that the three major peripheral memory B cell populations, pre-, post-switch, and double-negative B cells, are activated in RA, demonstrating enhanced CD95 and Ki-67 expressions, and varied expression of CXCR3 and CXCR4 chemokine receptors when compared with healthy individuals. This activation can be efficaciously modulated under cytokine inhibition in vivo.

Immunomodulatory Effects of Mesenchymal Stem Cells and Mesenchymal Stem Cell-Derived Extracellular Vesicles in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that affects the joints and other organs for which there is currently no effective treatment. Mesenchymal stem cells (MSCs) have therapeutic potential due to their immunomodulatory and differentiation effects. While extensive experimental studies and clinical trials have demonstrated the effects of MSCs in various diseases, MSCs have been found to cause abnormal differentiation and tumor formation. Therefore, extracellular vesicles derived from MSCs (MSC-EVs) are more effective, less toxic, and more stable than the parental cells. MSC-EVs transfer various nucleic acids, proteins, and lipids from parent cells to recipient cells, and thus participate in chronic inflammatory and immune processes. In this review, we summarize the properties and biological functions of MSCs and MSC-EVs in RA. Improvement in our understanding of the mechanisms underlying MSC and MSC-EVs in RA provides an insight into potential biomarkers and therapeutic strategies for RA.

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.

Challenges in Dengue Vaccines Development: Pre-existing Infections and Cross-Reactivity

Dengue is one of the most frequently transmitted mosquito-borne diseases in the world, which creates a significant public health concern globally, especially in tropical and subtropical countries. It is estimated that more than 390 million people are infected with dengue virus each year and around 96 million develop clinical pathologies. Dengue infections are not only a health problem but also a substantial economic burden. To date, there are no effective antiviral therapies and there is only one licensed dengue vaccine that only demonstrated protection in the seropositive (Immune), naturally infected with dengue, but not dengue seronegative (Naïve) vaccines. In this review, we address several immune components and their interplay with the dengue virus. Additionally, we summarize the literature pertaining to current dengue vaccine development and advances. Moreover, we review some of the factors affecting vaccine responses, such as the pre-vaccination environment, and provide an overview of the significant challenges that face the development of an efficient/protective dengue vaccine including the presence of multiple serotypes, antibody-dependent enhancement (ADE), as well as cross-reactivity with other flaviviruses. Finally, we discuss targeting T follicular helper cells (Tfh), a significant cell population that is essential for the production of high-affinity antibodies, which might be one of the elements needed to be specifically targeted to enhance vaccine precision to dengue regardless of dengue serostatus.

Update on the Pathomechanism, Diagnosis, and Treatment Options for Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease that involves multiple joints bilaterally. It is characterized by an inflammation of the tendon (tenosynovitis) resulting in both cartilage destruction and bone erosion. While until the 1990s RA frequently resulted in disability, inability to work, and increased mortality, newer treatment options have made RA a manageable disease. Here, great progress has been made in the development of disease-modifying anti-rheumatic drugs (DMARDs) which target inflammation and thereby prevent further joint damage. The available DMARDs are subdivided into (1) conventional synthetic DMARDs (methotrexate, hydrochloroquine, and sulfadiazine), (2) targeted synthetic DMARDs (pan-JAK- and JAK1/2-inhibitors), and (3) biologic DMARDs (tumor necrosis factor (TNF)-α inhibitors, TNF-receptor (R) inhibitors, IL-6 inhibitors, IL-6R inhibitors, B cell depleting antibodies, and inhibitors of co-stimulatory molecules). While DMARDs have repeatedly demonstrated the potential to greatly improve disease symptoms and prevent disease progression in RA patients, they are associated with considerable side-effects and high financial costs. This review summarizes our current understanding of the underlying pathomechanism, diagnosis of RA, as well as the mode of action, clinical benefits, and side-effects of the currently available DMARDs.

Peripheral B Cell Subsets in Autoimmune Diseases: Clinical Implications and Effects of B Cell-Targeted Therapies

Antibody-secreting cells (ASCs) play a fundamental role in humoral immunity. The aberrant function of ASCs is related to a number of disease states, including autoimmune diseases and cancer. Recent insights into activated B cell subsets, including naïve B cell to ASC stages and their resultant cellular disturbances, suggest that aberrant ASC differentiation occurs during autoimmune diseases and is closely related to disease severity. However, the mechanisms underlying highly active ASC differentiation and the B cell subsets in autoimmune patients remain undefined. Here, we first review the processes of ASC generation. From the perspective of novel therapeutic target discovery, prediction of disease progression, and current clinical challenges, we further summarize the aberrant activity of B cell subsets including specialized memory CD11c^hiT-bet⁺ B cells that participate in the maintenance of autoreactive ASC populations. An improved understanding of subgroups may also enhance the knowledge of antigen-specific B cell differentiation. We further discuss the influence of current B cell therapies on B cell subsets, specifically focusing on systemic lupus erythematosus, rheumatoid arthritis, and myasthenia gravis.

Peripheral Blood Lymphocyte Analysis in Oligo- and Polyarticular Juvenile Idiopathic Arthritis Patients Receiving Methotrexate or Adalimumab Therapy: A Cross-Sectional Study

Juvenile idiopathic arthritis (JIA) is an umbrella term for seven distinct chronic immune-mediated diseases. Disease-modifying anti-rheumatic drugs (DMARD) are used to treat the underlying joint inflammation as well as extra-articular manifestations. Immunosuppression is a considerable side effect of the drugs. The main goal of this study was to investigate the effect of different JIA therapies on leukocyte subpopulations, which play a role in immune-defense. Three study groups were established. The first group consisted of JIA patients treated with methotrexate solely, the second one received a combination of methotrexate (MTX) and adalimumab (ADA). The control group was made up of the patients' healthy siblings. A total of 63 children were recruited. Fourty-one children with JIA and 22 healthy controls were included in the study. The absolute number of CD3+ T-cells was significantly elevated in patients treated with biological therapy compared to healthy controls (p2 = 0.017). In contrast, the number of CD56+ natural killer cells was significantly lower in children receiving biological therapy in comparison with healthy donors (p2 = 0.039). A significant alteration was also demonstrated between patients treated with MTX and MTX/ADA group concerning CD 19+ B-cells (p3 = 0.042). This is the first study that demonstrates significant alterations in the number of B-cells and T-cells with a relative decrease of NK-cell ratios in JIA patients receiving different DMARD therapy. Clinical Trial Registration: NCT03833271. 21.01.2019.