T cell specific Cxcr5 deficiency prevents rheumatoid arthritis

Selective blockade of IL-21 by myricetin impedes T follicular helper cell differentiation by negatively regulating the JAK/STAT/Bcl-6 pathway in a rheumatoid arthritis animal model

Interleukin (IL)-21 is a major lineage-defining factor that promotes Tfh cell differentiation. The current study investigated the molecular basis of myricetin, a flavonoid that impedes IL-21-mediated differentiation of Tfh cells in RA. Through high-throughput virtual screening of natural compounds that inhibit IL-21, we found that myricetin binds to IL-21 and hampers its interaction with IL-21 receptor (IL-21R). Our in vivo studies demonstrated that myricetin treatment ameliorated the clinical manifestations in adjuvant-induced arthritis (AIA) mice by reducing paw thickness and cellular infiltration. In addition, myricetin inhibited splenic Tfh cell differentiation and IL-21 production in AIA mice. Myricetin negatively regulates JAK/STAT signaling and the downstream Bcl-6 transcription factor at the molecular level, which arrests Tfh cell differentiation. Our current research proposal to target IL-21 with myricetin inevitably represents a new molecular approach that expedites new alternative drugs for rheumatoid arthritis therapy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03880-w.

Polyclonal lymphoid expansion drives paraneoplastic autoimmunity in neuroblastoma

Neuroblastoma is a lethal childhood solid tumor of developing peripheral nerves. Two percent of children with neuroblastoma develop opsoclonus myoclonus ataxia syndrome (OMAS), a paraneoplastic disease characterized by cerebellar and brainstem-directed autoimmunity but typically with outstanding cancer-related outcomes. We compared tumor transcriptomes and tumor-infiltrating T and B cell repertoires from 38 OMAS subjects with neuroblastoma to 26 non-OMAS-associated neuroblastomas. We found greater B and T cell infiltration in OMAS-associated tumors compared to controls and showed that both were polyclonal expansions. Tertiary lymphoid structures (TLSs) were enriched in OMAS-associated tumors. We identified significant enrichment of the major histocompatibility complex (MHC) class II allele HLA-DOB∗01:01 in OMAS patients. OMAS severity scores were associated with the expression of several candidate autoimmune genes. We propose a model in which polyclonal auto-reactive B lymphocytes act as antigen-presenting cells and drive TLS formation, thereby supporting both sustained polyclonal T cell-mediated anti-tumor immunity and paraneoplastic OMAS neuropathology.

Immune surveillance and humoral immune responses in kidney transplantation - A look back at T follicular helper cells

T follicular helper cells comprise a specialized, heterogeneous subset of immune-competent T helper cells capable of influencing B cell responses in lymphoid tissues. In physiology, for example in response to microbial challenges or vaccination, this interaction chiefly results in the production of protecting antibodies and humoral memory. In the context of kidney transplantation, however, immune surveillance provided by T follicular helper cells can take a life of its own despite matching of human leukocyte antigens and employing the latest immunosuppressive regiments. This puts kidney transplant recipients at risk of subclinical and clinical rejection episodes with a potential risk for allograft loss. In this review, the current understanding of immune surveillance provided by T follicular helper cells is briefly described in physiological responses to contrast those pathological responses observed after kidney transplantation. Sensitization of T follicular helper cells with the subsequent emergence of detectable donor-specific human leukocyte antigen antibodies, non-human leukocyte antigen antibodies their implication for kidney transplantation and lessons learnt from other transplantation "settings" with special attention to antibody-mediated rejection will be addressed.

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.

Circulating DNA methylation level of CXCR5 correlates with inflammation in patients with rheumatoid arthritis

OBJECTIVES

To assess the differences in circulating DNA methylation levels of CXCR5 between rheumatoid arthritis (RA) and osteoarthritis (OA) and healthy controls (HC), and the correlation of methylation changes with clinical characteristics of RA patients.

METHODS

Peripheral blood samples were collected from 239 RA patients, 30 patients with OA, and 29 HC. Target region methylation sequencing to the promoter region of CXCR5 was achieved using MethylTarget. The methylation level of cg04537602 and methylation haplotype were compared among the three groups, and the correlation between methylation levels and clinical characteristics of RA patients was performed by Spearman's rank correlation analysis.

RESULTS

The methylation level of cg04537602 was significantly higher in the peripheral blood of RA patients compared with OA patients (p = 1.3 × 10^-3 ) and in the HC group (p = 5.5 × 10^{- 4} ). The sensitivity was enhanced when CXCR5 methylation level combined with rheumatoid factor and anti-cyclic citrullinated peptide with area under curve (AUC) of 0.982 (95% confidence interval 0.970-0.995). The methylation level of cg04537602 in RA was positively correlated with C-reactive protein (CRP) (r = .16, p = .01), and in RA patients aged 60 years and above, cg04537602 methylation levels were positively correlated with CRP (r = .31, p = 4.7 × 10^{- 4} ), tender joint count (r = .21, p = .02), visual analog scales score (r = .21, p = .02), Disease Activity Score in 28 joints (DAS28) using the CRP level DAS28-CRP (r = .27, p = 2.1 × 10^{- 3} ), and DAS28-ESR (r = .22, p = .01). We also observed significant differences of DNA methylation haplotypes in RA patients compared with OA patients and HC, which was consistent with single-loci-based CpG methylation measurement.

CONCLUSION

The methylation level of CXCR5 was significantly higher in RA patients than in OA and HC, and correlated with the level of inflammation in RA patients, our study establishes a link between CXCR5 DNA methylation and clinical features that may help in the diagnosis and disease management of RA patients.

Aberrant pro-inflammatory responses of CD20+ T cells in experimental arthritis

CD20+ T cells comprise a highly inflammatory subset implicated in autoimmunity, including rheumatoid arthritis (RA). We sought to characterize the CD20+ T cell subset in the murine collagen-induced arthritis (CIA) model of RA and investigate the phenotype and functional relevance of CD3+CD20+ T cells in the lymph nodes and arthritic joints using flow cytometry and immunohistochemistry. We demonstrate that CD3+CD4+CD20+ and CD3+CD8+CD20+ T cells are expanded in the draining lymph nodes of CIA mice, produce increased levels of pro-inflammatory cytokines and are less susceptible to regulation by regulatory T cells. Notably, CD3+CD4+CD20+ and CD3+CD8+CD20+ T cells are enriched with CXCR5+PD-1+ T follicular helper cells and CXCR5-PD-1+ peripheral T helper cells, subsets of T cells implicated in promoting B-cell responses and antibody production within pathologically inflamed non-lymphoid tissues in RA. Our findings suggest CD20+ T cells are associated with inflammatory responses and may exacerbate pathology by promoting inflammatory B-cell responses.

Genetic Polymorphisms in Follicular Helper T Cell-Related Molecules Predispose Patients to De Novo Donor-Specific Antibody Formation After Kidney Transplantation

BACKGROUND

Risk prediction of de novo donor-specific antibody (dnDSA) formation is crucial for understanding the long-term prognostic impact of kidney transplantation (KT). Recently, follicular helper T (Tfh) cells, a subtype of CD4⁺ T cells, have been reported to play an important role in dnDSA formation after solid organ transplantation. Given the growing recognition of the importance of Tfh cells in generating a strong humoral immune response, we examined whether polymorphisms in Tfh cell-related molecules were associated with dnDSA formation after KT.

METHODS

Eighty-three patients who underwent living-donor KT between January 2013 and February 2020 at Hiroshima University Hospital were included in the study. Six Tfh cell-related molecules (BCL6, CXCR5, CXCL13, ICOS, CD40L, and IL21) that are important for Tfh cell differentiation and maturation in secondary lymphoid tissues were investigated. CTLA4, which is important for Tfh-cell activation, was also investigated. Single nucleotide polymorphisms (SNPs) in the genes for these molecules were detected using Taq Man SNP genotyping and evaluated for their association with dnDSA formation after KT.

RESULTS

Of the 83 KT recipients, 8 developed dnDSAs during the observation period. No statistically significant differences were observed in the baseline characteristics between patients with and without dnDSA formation, except for donor age. Among the 7 Tfh cell-related molecules, the incidence of dnDSA formation was associated with CXCR5 and CTLA4 SNPs. Furthermore, combining these 2 SNPs enabled more significant stratification of dnDSA formation.

CONCLUSION

Our findings indicate that genetic polymorphisms in Tfh cell-related molecules are predisposing factors for dnDSA formation after KT.

Chemokines and chemokine receptors as promising targets in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease that commonly causes inflammation and bone destruction in multiple joints. Inflammatory cytokines, such as IL-6 and TNF-α, play important roles in RA development and pathogenesis. Biological therapies targeting these cytokines have revolutionized RA therapy. However, approximately 50% of the patients are non-responders to these therapies. Therefore, there is an ongoing need to identify new therapeutic targets and therapies for patients with RA. In this review, we focus on the pathogenic roles of chemokines and their G-protein-coupled receptors (GPCRs) in RA. Inflamed tissues in RA, such as the synovium, highly express various chemokines to promote leukocyte migration, tightly controlled by chemokine ligand-receptor interactions. Because the inhibition of these signaling pathways results in inflammatory response regulation, chemokines and their receptors could be promising targets for RA therapy. The blockade of various chemokines and/or their receptors has yielded prospective results in preclinical trials using animal models of inflammatory arthritis. However, some of these strategies have failed in clinical trials. Nonetheless, some blockades showed promising results in early-phase clinical trials, suggesting that chemokine ligand-receptor interactions remain a promising therapeutic target for RA and other autoimmune diseases.

CXCL13 and CXCR5 are upregulated in PCOS mice ovaries but downregulated following metformin administration

Polycystic ovary syndrome (PCOS) is becoming a common pathology among women, yet its pathogenesis remains enigmatic. The chemokine C-X-C motif ligand 13 (CXCL13) and its receptor type 5 (CXCR5) regulate inflammatory responses but their roles in PCOS remain unknown. Metformin is commonly administered to PCOS patients but its mechanism of action remains unclear. Thus, we aimed to determine the expression of CXCL13 and CXCR5 in the ovaries of PCOS mice and to evaluate the therapeutic effect of metformin on them. The study comprised four groups of mice: control, PCOS, PCOS plus metformin, and PCOS plus vehicle. CXCL13 and CXCR5 were found to be elevated in the ovarian tissues of the PCOS mice. Metformin reduced ovarian CXCL13 and CXCR5 expressions in the PCOS mice. Hence, CXCL13 and CXCR5 are potentially involved in PCOS pathogenesis; and metformin may help alleviate the symptoms of PCOS by inhibiting CXCL13 expression and actions.

Mitochondrial regulation of acute extrafollicular B-cell responses to COVID-19 severity

BACKGROUND

Patients with COVID-19 display a broad spectrum of manifestations from asymptomatic to life-threatening disease with dysregulated immune responses. Mechanisms underlying the detrimental immune responses and disease severity remain elusive.

METHODS

We investigated a total of 137 APs infected with SARS-CoV-2. Patients were divided into mild and severe patient groups based on their requirement of oxygen supplementation. All blood samples from APs were collected within three weeks after symptom onset. Freshly isolated PBMCs were investigated for B cell subsets, their homing potential, activation state, mitochondrial functionality and proliferative response. Plasma samples were tested for cytokine concentration, and titer of Nabs, RBD-, S1-, SSA/Ro- and dsDNA-specific IgG.

RESULTS

While critically ill patients displayed predominantly extrafollicular B cell activation with elevated inflammation, mild patients counteracted the disease through the timely induction of mitochondrial dysfunction in B cells within the first week post symptom onset. Rapidly increased mitochondrial dysfunction, which was caused by infection-induced excessive intracellular calcium accumulation, suppressed excessive extrafollicular responses, leading to increased neutralizing potency index and decreased inflammatory cytokine production. Patients who received prior COVID-19 vaccines before infection displayed significantly decreased extrafollicular B cell responses and mild disease.

CONCLUSION

Our results reveal an immune mechanism that controls SARS-CoV-2-induced detrimental B cell responses and COVID-19 severity, which may have implications for viral pathogenesis, therapeutic interventions and vaccine development.

Serum Levels of CXCL13 Are an Independent Predictor of Survival Following Resection of Biliary Tract Cancer

Simple Summary

Biliary tract cancer (BTC) is a primary liver malignancy with poor outcome. The identification of the ideal surgical candidates is often challenging and stratification algorithms comprising the parameters of individual tumor biology are missing. Here, we investigated a potential role of circulating CXCL1, CXCL10 and CXCL13 in patients with resectable BTC as novel biomarkers and could show that elevated levels of CXCL13 both before and after tumor resection identified a subgroup of patients with significantly impaired outcomes following tumor resection. Thus, the present study supports a fundamental role of the CXC chemokine family in BTC and identifies circulating levels of CXCL13 as a previously unrecognized marker for predicting outcomes following the resection of BTC.

Abstract

Background: The prognosis of biliary tract cancer (BTC) has remained very poor. Although tumor resection represents a potentially curative therapy for selected patients, tumor recurrence is common, and 5-year survival rates have remained below 50%. As stratification algorithms comprising the parameters of individual tumor biology are missing, the identification of ideal patients for extensive tumor surgery is often challenging. The CXC chemokine family exerts decisive functions in cell–cell interactions and has only recently been associated with cancer, but little is known about their function in BTC. Here, we aim to evaluate a potential role of circulating CXCL1, CXCL10 and CXCL13 in patients with resectable BTC. Methods: Serum levels of CXCL1, CXCL10 and CXCL13 were measured by multiplex immunoassay in a cohort of 119 BTC patients undergoing tumor resection and 50 control samples. Results: Circulating levels of CXCL1, CXCL10 and CXCL13 were all significantly elevated in BTC patients compared to healthy controls and increased the diagnostic power of established tumor markers such as CA19-9 when used in combination. Importantly, elevated levels of CXCL13 both before and after tumor resection identified a subgroup of patients with significantly impaired outcomes following tumor resection. As such, BTC patients with initial CXCL13 levels above the ideal prognostic cut-off value (25.01 pg/mL) had a median overall survival (OS) of 290 days compared to 969 days for patients with low initial CXCL13 levels. The prognostic value of circulating CXCL13 was further confirmed by uni- and multivariate Cox regression analyses. Finally, the individual kinetics of CXCL13 before and after tumor resection were also indicative of patient outcomes. Conclusion: Our data support a fundamental role of the CXC chemokine family in BTC and identified circulating levels of CXCL13 as a previously unrecognized marker for predicting outcomes following the resection of BTC.

Disease mechanisms in preclinical rheumatoid arthritis: A narrative review

In the last decades, the concept of preclinical rheumatoid arthritis (RA) has become established. In fact, the discovery that disease mechanisms start years before the onset of clinical RA has been one of the major recent insights in the understanding of RA pathogenesis. In accordance with the complex nature of the disease, preclinical events extend over several sequential phases. In a genetically predisposed host, environmental factors will further increase susceptibility for incident RA. In the initial steps of preclinical disease, immune disturbance mechanisms take place outside the joint compartment, namely in mucosal surfaces, such as the lung, gums or gut. Herein, the persistent immunologic response to altered antigens will lead to breach of tolerance and trigger autoimmunity. In a second phase, the immune response matures and is amplified at a systemic level, with epitope spreading and widening of the autoantibody repertoire. Finally, the synovial and bone compartment are targeted by specific autoantibodies against modified antigens, initiating a local inflammatory response that will eventually culminate in clinically evident synovitis. In this review, we discuss the elaborate disease mechanisms in place during preclinical RA, providing a broad perspective in the light of current evidence.

G-Protein-Coupled Receptors in Rheumatoid Arthritis: Recent Insights into Mechanisms and Functional Roles

Rheumatoid arthritis (RA) is a chronic inflammatory disease that leads to joint damage and even disability. Although there are various clinical therapies for RA, some patients still have poor or no response. Thus, the development of new drug targets remains a high priority. In this review, we discuss the role of G-protein-coupled receptors (GPCRs), including chemokine receptors, melanocortin receptors, lipid metabolism-related receptors, adenosine receptors, and other inflammation-related receptors, on mechanisms of RA, such as inflammation, lipid metabolism, angiogenesis, and bone destruction. Additionally, we summarize the latest clinical trials on GPCR targeting to provide a theoretical basis and guidance for the development of innovative GPCR-based clinical drugs for RA.

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.

Germinal Center-Related G Protein-Coupled Receptors in Antibody-Mediated Autoimmune Skin Diseases: from Basic Research to Clinical Trials

Germinal center (GC) reaction greatly contributes to the humoral immune response, which begins in lymph nodes or other secondary lymphoid organs after follicular B cells are activated by T-dependent antigens. The GCs then serve as a platform for follicular B cells to complete clonal expansion and somatic hypermutation and then interact with follicular dendritic cells (FDC) and follicular helper T cells (Tfh). Through the interaction between the immune cells, significant processes of the humoral immune response are accomplished, such as antibody affinity maturation, class switching, and production of memory B cells and plasma cells. Cell positioning during the GC reaction is mainly mediated by the chemokine receptors and lipid receptors, which both belong to G protein-coupled receptors (GPCRs) family. There are some orphan GPCRs whose endogenous ligands are unclear yet contribute to the regulation of GC reaction as well. This review will give an introduction on the ligands and functions of two types of GC-relating GPCRs-chemokine receptors like CXCR4 and CXCR5, as well as emerging de-orphanized GPCRs like GPR183, GPR174, and P2RY8. The roles these GPCRs play in several antibody-mediated autoimmune skin diseases will be also discussed, including systemic lupus erythematosus (SLE), pemphigus, scleroderma, and dermatomyositis. Besides, GPCRs are excellent drug targets due to the unique structure and vital functions. Therefore, this review is aimed at providing readers with a focused knowledge about the role that GPCRs play in GC reaction, as well as in provoking the development of GPCR-targeting agents for immune-mediated diseases besides autoimmune diseases.

Providing a Helping Hand: Metabolic Regulation of T Follicular Helper Cells and Their Association With Disease

T follicular helper (Tfh) cells provide support to B cells upon arrival in the germinal center, and thus are critical for the generation of a robust adaptive immune response. Tfh express specific transcription factors and cellular receptors including Bcl6, CXCR5, PD-1, and ICOS, which are critical for homing and overall function. Generally, the induction of an immune response is tightly regulated. However, deviation during this process can result in harmful autoimmunity or the inability to successfully clear pathogens. Recently, it has been shown that Tfh differentiation, activation, and proliferation may be linked with the cellular metabolic state. In this review we will highlight recent discoveries in Tfh differentiation and explore how these cells contribute to functional immunity in disease, including autoimmune-related disorders, cancer, and of particular emphasis, during infection.

Role of the CXCL13/CXCR5 Axis in Autoimmune Diseases

CXCL13 is a B-cell chemokine produced mainly by mesenchymal lymphoid tissue organizer cells, follicular dendritic cells, and human T follicular helper cells. By binding to its receptor, CXCR5, CXCL13 plays an important role in lymphoid neogenesis, lymphoid organization, and immune responses. Recent studies have found that CXCL13 and its receptor CXCR5 are implicated in the pathogenesis of several autoimmune diseases, such as rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, primary Sjögren’s syndrome, myasthenia gravis, and inflammatory bowel disease. In this review, we discuss the biological features of CXCL13 and CXCR5 and the recent findings on the pathogenic roles of the CXCL13/CXCR5 axis in autoimmune diseases. Furthermore, we discuss the potential role of CXCL13 as a disease biomarker and therapeutic target in autoimmune diseases.

Splenic Architecture and Function Requires Tight Control of Transmembrane TNF Expression

Soluble tumor necrosis factor (sTNF) is an important inflammatory mediator and essential for secondary lymphoid organ (SLO) development and function. However, the role of its transmembrane counterpart (tmTNF) in these processes is less well established. Here, the effects of tmTNF overxpression on SLO architecture and function were investigated using tmTNF-transgenic (tmTNF-tg) mice. tmTNF overexpression resulted in enlarged peripheral lymph nodes (PLNs) and spleen, accompanied by an increase in small splenic lymphoid follicles, with less well-defined primary B cell follicles and T cell zones. In tmTNF-tg mice, the spleen, but not PLNs, contained reduced germinal center (GC) B cell fractions, with low Ki67 expression and reduced dark zone characteristics. In line with this, smaller fractions of T follicular helper (Tfh) and T follicular regulatory (Tfr) cells were observed with a decreased Tfh:Tfr ratio. Moreover, plasma cell (PC) formation in the spleen of tmTNF-tg mice decreased and skewed towards IgA and IgM expression. Genetic deletion of TNFRI or –II resulted in a normalization of follicle morphology in the spleen of tmTNF-tg mice, but GC B cell and PC fractions remained abnormal. These findings demonstrate that tightly regulated tmTNF is important for proper SLO development and function, and that aberrations induced by tmTNF overexpression are site-specific and mediated via TNFRI and/or TNFRII signaling.

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.

In Vivo Imaging of Tfh Cells

Germinal centers (GCs) are microanatomical structures in secondary lymphoid organs where B cells undergo affinity maturation for antigen during the course of an immune response. This process is driven by a subset of T cells termed T follicular helper cells (Tfh) that through a multistep process gain access to the GC niche within the B cell follicle. This protocol details how to study Tfh behavior in vivo, on a single cell level, using two-photon intravital microscopy of the murine popliteal lymph node.

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.

Bioinformatics-based study to identify immune infiltration and inflammatory-related hub genes as biomarkers for the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease whose principal pathological change is aggressive chronic synovial inflammation; however, the specific etiology and pathogenesis have not been fully elucidated. We downloaded the synovial tissue gene expression profiles of four human knees from the Gene Expression Omnibus database, analyzed the differentially expressed genes in the normal and RA groups, and assessed their enrichment in functions and pathways using bioinformatics methods and the STRING online database to establish protein-protein interaction networks. Cytoscape software was used to obtain 10 hub genes; receiver operating characteristic (ROC) curves were calculated for each hub gene and differential expression analysis of the two groups of hub genes. The CIBERSORT algorithm was used to impute immune infiltration. We identified the signaling pathways that play important roles in RA and 10 hub genes: Ccr1, Ccr2, Ccr5, Ccr7, Cxcl5, Cxcl6, Cxcl13, Ccl13, Adcy2, and Pnoc. The diagnostic value of these 10 hub genes for RA was confirmed using ROC curves and expression analysis. Adcy2, Cxcl13, and Ccr5 are strongly associated with RA development. The study also revealed that the differential infiltration profile of different inflammatory immune cells in the synovial tissue of RA is an extremely critical factor in RA progression. This study may contribute to the understanding of signaling pathways and biological processes associated with RA and the role of inflammatory immune infiltration in the pathogenesis of RA. In addition, this study shows that Adcy2, Cxcl13, and Ccr5 have the potential to be biomarkers for RA treatment.

Promising Therapeutic Targets for Treatment of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a systemic poly-articular chronic autoimmune joint disease that mainly damages the hands and feet, which affects 0.5% to 1.0% of the population worldwide. With the sustained development of disease-modifying antirheumatic drugs (DMARDs), significant success has been achieved for preventing and relieving disease activity in RA patients. Unfortunately, some patients still show limited response to DMARDs, which puts forward new requirements for special targets and novel therapies. Understanding the pathogenetic roles of the various molecules in RA could facilitate discovery of potential therapeutic targets and approaches. In this review, both existing and emerging targets, including the proteins, small molecular metabolites, and epigenetic regulators related to RA, are discussed, with a focus on the mechanisms that result in inflammation and the development of new drugs for blocking the various modulators in RA.

Berberine Delays Onset of Collagen-Induced Arthritis through T Cell Suppression

There is evidence that berberine (BBR), a clinically relevant plant compound, ameliorates clinically apparent collagen-induced arthritis (CIA) in vivo. However, to date, there are no studies involving the use of BBR which explore its prophylactic potential in this model of rheumatoid arthritis (RA). The aim of this study was to determine if prophylactic BBR use during the preclinical phase of collagen-induced arthritis would delay arthritic symptom onset, and to characterize the cellular mechanism underlying such an effect. DBA/1J mice were injected with an emulsion of bovine type II collagen (CII) and complete Freund’s adjuvant (day 0) and a booster injection of CII in incomplete Freund’s adjuvant (day 18) to induce arthritis. Mice were then given i.p. injections of 1 mg/kg/day of BBR or PBS (vehicle with 0.01% DMSO) from days 0 to 28, were left untreated (CIA control), or were in a non-arthritic control group (n = 15 per group). Incidence of arthritis in BBR-treated mice was 50%, compared to 90% in both the CIA and PBS controls. Populations of B and T cells from the spleens and draining lymph nodes of mice were examined on day 14 (n = 5 per group) and day 28 (n = 10 per group). BBR-treated mice had significantly reduced populations of CD4⁺T_h and CD4⁺CXCR5⁺ T_fh cells, and an increased proportion of Foxp3⁺ T_reg at days 14 and 28, as well as reduced expression of co-stimulatory molecules CD28 and CD154 at both endpoints. The effect seen on T cell populations and co-stimulatory molecule expression in BBR-treated mice was not mirrored in CD19⁺ B cells. Additionally, BBR-treated mice experienced reduced anti-CII IgG2a and anti-CII total IgG serum concentrations. These results indicate a potential role for BBR as a prophylactic supplement for RA, and that its effect may be mediated specifically through T cell suppression. However, the cellular effector involved raises concern for BBR prophylactic use in the context of vaccine efficacy and other primary adaptive immune responses.

Prolactin Increases the Frequency of Follicular T Helper Cells with Enhanced IL21 Secretion and OX40 Expression in Lupus-Prone MRL/lpr Mice

Systemic lupus erythematosus is characterized by high levels of IgG class autoantibodies that contribute to the pathophysiology of the disease. The formation of these autoantibodies occurs in the germinal centers, where there is cooperation between follicular T helper cells (T_FH) and autoreactive B cells. Prolactin has been reported to exacerbate the clinical manifestations of lupus by increasing autoantibody concentrations. The objective of this study was to characterize the participation of prolactin in the differentiation and activation of T_FH cells, by performing in vivo and in vitro tests with lupus-prone mice, using flow cytometry and real-time PCR. We found that T_FH cells express the long isoform of the prolactin receptor and promoted STAT3 phosphorylation. Receptor expression was higher in MRL/lpr mice and correlative with the manifestations of the disease. Although prolactin does not intervene in the differentiation of T_FH cells, it does favor their activation by increasing the percentage of T_FH OX40⁺ and T_FH IL21⁺ cells, as well as leading to high serum concentrations of IL21. These results support a mechanism in which prolactin participates in the emergence of lupus by inducing overactive T_FH cells and perhaps promoting dysfunctional germinal centers.

Functional differentiation and regulation of follicular T helper cells in inflammation and autoimmunity

Follicular T helper (T_FH ) cells are specialized T cells that support B cells, which are essential for humoral immunity. T_FH cells express the transcription factor B-cell lymphoma 6 (Bcl-6), chemokine (C-X-C motif) receptor (CXCR) 5, the surface receptors programmed cell death protein 1 (PD-1) and inducible T-cell costimulator (ICOS), the cytokine IL-21 and other molecules. The activation, proliferation and differentiation of T_FH cells are closely related to dynamic changes in cellular metabolism. In this review, we summarize the progress made in understanding the development and functional differentiation of T_FH cells. Specifically, we focus on the regulatory mechanisms of T_FH cell functional differentiation, including regulatory signalling pathways and the metabolic regulatory mechanisms of T_FH cells. In addition, T_FH cells are closely related to immune-associated diseases, including infections, autoimmune diseases and cancers.

A Two-Step Process of Effector Programming Governs CD4+ T Cell Fate Determination Induced by Antigenic Activation in the Steady State

Various processes induce and maintain immune tolerance, but effector T cells still arise under minimal perturbations of homeostasis through unclear mechanisms. We report that, contrary to the model postulating primarily tolerogenic mechanisms initiated under homeostatic conditions, effector programming is an integral part of T cell fate determination induced by antigenic activation in the steady state. This effector programming depends on a two-step process starting with induction of effector precursors that express Hopx and are imprinted with multiple instructions for their subsequent terminal effector differentiation. Such molecular circuits advancing specific terminal effector differentiation upon re-stimulation include programmed expression of interferon-γ, whose production then promotes expression of T-bet in the precursors. We further show that effector programming coincides with regulatory conversion among T cells sharing the same antigen specificity. However, conventional type 2 dendritic cells (cDC2) and T cell functions of mammalian target of rapamycin complex 1 (mTORC1) increase effector precursor induction while decreasing the proportion of T cells that can become peripheral Foxp3⁺ regulatory T (pTreg) cells.

The mechanisms in the steady state that govern the formation of effector T cells with potentially autoimmune functions remain unclear. Opejin et al. reveal a two-step process starting with induction of effector precursors that express Hopx and are imprinted with multiple instructions for their subsequent terminal effector differentiation.

Continued Bcl6 Expression Prevents the Transdifferentiation of Established Tfh Cells into Th1 Cells during Acute Viral Infection

T follicular helper (Tfh) cells are crucial for the establishment of germinal centers (GCs) and potent antibody responses. Nevertheless, the T cell-intrinsic factors that are required for the maintenance of already-established Tfh cells and GCs remain largely unknown. Here, we use temporally guided gene ablation in CD4⁺ T cells to dissect the contributions of the Tfh-associated chemokine receptor CXCR5 and the transcription factor Bcl6. Induced ablation of Cxcr5 has minor effects on the function of established Tfh cells, and Cxcr5-ablated cells still exhibit most of the features of CXCR5⁺ Tfh cells. In contrast, continued Bcl6 expression is critical to maintain the GC Tfh cell phenotype and also the GC reaction. Importantly, Bcl6 ablation during acute viral infection results in the transdifferentiation of established Tfh into Th1 cells, thus highlighting the plasticity of Tfh cells. These findings have implications for strategies that boost or restrain Tfh cells and GCs in health and disease.

The N-terminal length and side-chain composition of CXCL13 affect crystallization, structure and functional activity

CXCL13 is the cognate chemokine agonist of CXCR5, a class A G-protein-coupled receptor (GPCR) that is essential for proper humoral immune responses. Using a `methionine scanning' mutagenesis method on the N-terminus of CXCL13, which is the chemokine signaling region, it was shown that minor length alterations and side-chain substitutions still result in CXCR5 activation. This observation indicates that the orthosteric pocket of CXCR5 can tolerate these changes without severely affecting the activity. The introduction of bulk on the ligand was well tolerated by the receptor, whereas a loss of contacts was less tolerated. Furthermore, two crystal structures of CXCL13 mutants were solved, both of which represent the first uncomplexed structures of the human protein. These structures were stabilized by unique interactions formed by the N-termini of the ligands, indicating that CXCL13 exhibits substantial N-terminal flexibility while the chemokine core domain remains largely unchanged. Additionally, it was observed that CXCL13 harbors a large degree of flexibility in the C-terminal extension of the ligand. Comparisons with other published structures of human and murine CXCL13 validate the relative rigidity of the core domain as well as the N- and C-terminal mobilities. Collectively, these mutants and their structures provide the field with additional insights into how CXCL13 interacts with CXCR5.

Microbiota-derived butyrate limits the autoimmune response by promoting the differentiation of follicular regulatory T cells

Background

Rheumatoid arthritis (RA) is a chronic debilitating autoimmune disorder with a high prevalence, especially in industrialized countries. Dysbiosis of the intestinal microbiota has been observed in RA patients. For instance, new-onset untreated RA (NORA) is associated with the underrepresentation of the Clostridium cluster XIVa, including Lachnospiraceae, which are major butyrate producers, although the pathological relevance has remained obscure. Follicular regulatory T (T_FR) cells play critical regulatory roles in the pathogenesis of autoimmune diseases, including RA. Reduced number of circulating T_FR cells has been associated with the elevation of autoantibodies and disease severity in RA. However, the contribution of commensal microbe-derived butyrate in controlling T_FR cell differentiation remains unknown.

Methods

We examined the contribution of microbe-derived butyrate in controlling autoimmune arthritis using collagen-induced arthritis (CIA) and SKG arthritis models. We phenotyped autoimmune responses in the gut-associated lymphoid tissues (GALT) in the colon and joint-draining lymph nodes in the CIA model. We developed an in vitro CXCR5⁺Bcl-6⁺Foxp3⁺ T_FR (iT_FR) cell culture system and examined whether butyrate promotes the differentiation of iT_FR cells.

Findings

Microbe-derived butyrate suppressed the development of autoimmune arthritis. The immunization of type II collagen (CII) caused hypertrophy of the GALT in the colon by amplifying the GC reaction prior to the onset of the CIA. Butyrate mitigated these pathological events by promoting T_FR cell differentiation. Butyrate directly induced the differentiation of functional T_FR cells in vitro by enhancing histone acetylation in T_FR cell marker genes. This effect was attributed to histone deacetylase (HDAC) inhibition by butyrate, leading to histone hyperacetylation in the promoter region of the T_FR-cell marker genes. The adoptive transfer of the butyrate-treated iT_FR cells reduced CII-specific autoantibody production and thus ameliorated the symptoms of arthritis.

Interpretation

Accordingly, microbiota-derived butyrate serves as an environmental cue to enhance T_FR cells, which suppress autoantibody production in the systemic lymphoid tissue, eventually ameliorating RA. Our findings provide mechanistic insights into the link between the gut environment and RA risk.

Funding

This work was supported by 10.13039/100009619AMED-Crest (16gm1010004h0101, 17gm1010004h0102, 18gm1010004h0103, and 19gm1010004s0104 to KH), the Japan Society for the Promotion of Science (JP17KT0055, JP16H01369, and JP18H04680 to KH; JP17K15734 to DT), Keio University Special Grant-in-Aid for Innovative Collaborative Research Projects (KH), Keio Gijuku Fukuzawa Memorial Fund for the Advancement of Education and Research (DT), the SECOM Science and Technology Foundation (KH), the Cell Science Research Foundation (KH), the Mochida Memorial Foundation for Medical and Pharmaceutical Research (DT), the Suzuken Memorial Foundation (KH and DT), the Takeda Science Foundation (KH and DT), The Science Research Promotion Fund, and The Promotion and Mutual Aid Corporation for Private Schools of Japan (KH).

Targeting the Chemokine System in Rheumatoid Arthritis and Vasculitis

Arrest of circulating leukocytes and subsequent diapedesis is a fundamental component of inflammation. In general, the leukocyte migration cascade is tightly regulated by chemoattractants, such as chemokines. Chemokines, small secreted chemotactic cytokines, as well as their G-protein-coupled seven transmembrane spanning receptors, control the migratory patterns, positioning and cellular interactions of immune cells. Increased levels of chemokines and their receptors are found in the blood and within inflamed tissue in patients with rheumatoid arthritis (RA) and vasculitis. Chemokine ligand-receptor interactions regulate the recruitment of leukocytes into tissue, thus contributing in important ways to the pathogenesis of RA and vasculitis. Despite the fact that blockade of chemokines and chemokine receptors in animal models have yielded promising results, human clinical trials in RA using inhibitors of chemokines and their receptors have generally failed to show clinical benefits. However, recent early phase clinical trials suggest that strategies blocking specific chemokines may have clinical benefits in RA, demonstrating that the chemokine system remains a promising therapeutic target for rheumatic diseases, such as RA and vasuculitis and requires further study.

An imbalance between blood CD4+CXCR5+Foxp3+ Tfr cells and CD4+CXCR5+Tfh cells may contribute to the immunopathogenesis of rheumatoid arthritis

BACKGROUND

Follicular helper T (Tfh) cells are a subgroup of activated CD4⁺ T cells which can assist the formation and maintenance of germinal centers. Follicular regulatory T (Tfr) cells are a new class of regulatory T cells which play a major role in suppressing cells in humoral immunity. In contrast to the role of Tfh cells, Tfr cells can inhibit the function of Tfh cells and B cells. Imbalance of blood Tfr/Tfh ratio resulted in the expansion of auto-reactive B cells and auto-antibody production (). However, the effect of Tfr cells and Tfh cells in the pathogenesis of RA (rheumatoid arthritis) is unclear. The purpose of this study was to investigate the function of Tfr cells and Tfh cells in the pathogenesis of RA.

METHODS

We recruited 20 patients fulfilled the the American College of Rheumatology diagnosis criteria and 20 healthy controls (HCs). The number of CD4⁺CXCR5⁺Foxp3⁺ Tfr cells and CD4⁺CXCR5⁺ Tfh cells in 20 RA patients were measured by flow cytometry analysis. Furthermore, the correlations between the Tfr/Tfh ratio and the characteristic clinical parameters were assessed. The serum levels of IL-21(interleukin-21), CXCL13 (chemokine (C-X-C motif) ligand 13) and TGF-β (Transforming growth factor-β) were measured by ELISA. The formation of ectopic germinal center (GC) of synovial membrane was examined by H&E staining. The transcriptional levels of CXCR5 (C-X-C chemokine receptor type 5), CXCL13, ICOS (inducible co-stimulater) and TGF-β mRNA were also analyzed. In addition, the expression of Bcl-6 (B-cell lymphoma 6), CXCR5, CXCL13 and ICOS in synovial membrane were examined by immunohistochemistry.

RESULTS

RA patients had more Tfh cells in peripheral blood, conversely, the frequency of blood Tfr cells (p < 0.05) and the ratio of Tfr/Tfh were significantly decreased compared to healthy controls (p < 0.05, p < 0.01). Furthermore, the ratio of Tfr/Tfh was negatively correlated with values of ESR (r=-0.57, p < 0.05), RF (r=-0.5275, p < 0.001), CRP (r=-0.4486, p < 0.001), IgG (r=-0.4631, p < 0.05), DAS28 scores (r=-0.5645, p < 0.01), as well as the levels of IL-21(r=-0.7398, p < 0.01), CXCL13 (r=-0.4832, p < 0.05). However, the ratio of Tfr/Tfh was positively with the serum level of TGF-β (r=0.5115, p < 0.05). Higher mRNA expression of CXCR5, CXCL13, ICOS and lower TGF-β mRNA expression were observed in RA patients. The serum expression level of IL-21, CXCL13 was significantly increased and expression of TGF-β was significantly decreased in RA patients. Furthermore, ectopic germinal center formation and higher expression of Bcl-6, CXCR5, ICOS, CXCL13 in the synovial membrane of the joints in RA patients were observed.

CONCLUSIONS

The decreased blood CD4⁺CXCR5⁺Foxp3⁺ Tfr cells/CD4⁺CXCR5⁺ Tfh cells may be responsible for the immunopathogenesis of RA.

Ethanol consumption inhibits TFH cell responses and the development of autoimmune arthritis

Alcohol consumption is a consistent protective factor for the development of autoimmune diseases such as rheumatoid arthritis (RA). The underlying mechanism for this tolerance-inducing effect of alcohol, however, is unknown. Here we show that alcohol and its metabolite acetate alter the functional state of T follicular helper (T_FH) cells in vitro and in vivo, thereby exerting immune regulatory and tolerance-inducing properties. Alcohol-exposed mice have reduced Bcl6 and PD-1 expression as well as IL-21 production by T_FH cells, preventing proper spatial organization of T_FH cells to form T_FH:B cell conjugates in germinal centers. This effect is associated with impaired autoantibody formation, and mitigates experimental autoimmune arthritis. By contrast, T cell independent immune responses and passive models of arthritis are not affected by alcohol exposure. These data clarify the immune regulatory and tolerance-inducing effect of alcohol consumption.

Moderate consumption of alcohol is associated with protection from some autoimmune diseases. Here the authors show that ethanol and its metabolite acetate can protect mice from collagen-induced arthritis and provide evidence that the mechanism of this effect might be via inhibition of the effector function of T follicular helper cells.

A highlight on CD4+ T-cells in the spleen in a rat model of rheumatoid arthritis and possible therapeutic effect of omega-3. Histological and Immunofluorescence study

BACKGROUND

Rheumatoid arthritis (RA), a primary chronic articular disease with wide range of extra-articular and systemic effects. The spleen is one of the most affected organs in RA. CD4⁺ T cells play an important role in initiation, maintenance and control of the disease.

AIM OF THE WORK

This work was designed to study the histological changes occurring in the spleen in a rat model of RA and to assess the effect of treatment with omega-3 alone, with special refer to the role of CD4⁺ T-cells.

MATERIALS AND METHODS

Thirty male albino rats were divided into four groups; control group, early and progressive RA groups and omega-3 treated group. RA was induced in rats of groups II, III and IV by a single subcutaneous injection of complete Freund's adjuvant (CFA). Samples were taken after two and four weeks of the CFA injection (in early and progressive RA groups respectively). Treatment with omega-3 (300 mg/kg/day in a single, daily oral dose) started two weeks after CFA injection in rats of group IV and continued for another two weeks. Spleen specimens were collected at the appropriate times and processed to obtain paraffin blocks. Sections were then stained for histological and immunofluorescence studies.

RESULTS

Both, early and progressive RA induced noticeable structural changes in the spleen. Thickened capsule and trabeculae and marked congestion of the blood sinusoids of the red pulp were evident. Expansion of the white pulp and areas of mononuclear cellular infiltration were seen, especially in progressive RA. Affection of blood vessel walls was also noticed. Immunofluorescence study showed extensive expression of Anti-CD4 Monoclonal Antibodies especially in progressive RA. Treatment with omega-3 significantly improved the structure of the spleen as detected by both histological and immunofluorescence studies.

CONCLUSION

Omega-3 treatment ameliorated the structural damage of the spleen caused by experimental induction of RA.

Sex differences in Tfh cell help to B cells contribute to sexual dimorphism in severity of rat collagen-induced arthritis

The study examined germinal centre (GC) reaction in lymph nodes draining inflamed joints and adjacent tissues (dLNs) in male and female Dark Agouti rat collagen type II (CII)-induced arthritis (CIA) model of rheumatoid arthritis. Female rats exhibiting the greater susceptibility to CIA mounted stronger serum CII-specific IgG response than their male counterparts. This correlated with the higher frequency of GC B cells in female compared with male dLNs. Consistently, the frequency of activated/proliferating Ki-67+ cells among dLN B cells was higher in females than in males. This correlated with the shift in dLN T follicular regulatory (Tfr)/T follicular helper (Tfh) cell ratio towards Tfh cells in females, and greater densities of CD40L and CD40 on their dLN T and B cells, respectively. The higher Tfh cell frequency in females was consistent with the greater dLN expression of mRNA for IL-21/27, the key cytokines involved in Tfh cell generation and their help to B cells. Additionally, in CII-stimulated female rat dLN cell cultures IFN-γ/IL-4 production ratio was shifted towards IFN-γ. Consistently, the serum IgG2a(b)/IgG1 CII-specific antibody ratio was shifted towards an IgG2a(b) response in females. Thus, targeting T-/B-cell interactions should be considered in putative further sex-based translational pharmacology research.

Tertiary Lymphoid Organs in Rheumatoid Arthritis

Rheumatoid Arthritis (RA) is a chronic systemic autoimmune disease. RA mainly affects the joints, with inflammation of the synovial membrane, characterized by hyperplasia, neo-angiogenesis, and immune cell infiltration that drives local inflammation and, if untreated, can lead to joint destruction and disability. In parallel to the well-known clinical heterogeneity, the underlying synovitis can also be significantly heterogeneous. In particular, in about 40% of patients with RA, synovitis is characterized by a dense lymphocytic infiltrate that can acquire the features of fully functional tertiary lymphoid organs (TLO). These structures amplify autoimmunity and inflammation locally associated with worse prognosis and potential implications for treatment response. Here, we will review the current knowledge on TLO in RA, with a focus on their pathogenetic and clinical relevance.

Total Glucosides of Paeony protects against collagen-induced mouse arthritis via inhibiting follicular helper T cell differentiation

BACKGROUND

The development of rheumatoid arthritis (RA) is related to germinal center (GC) response and autoreactive T cells, which mediate adaptive immunity and play an important role in stimulating the production of autoantibodies and pro-inflammatory cytokines by B cells and macrophages. Total Glucosides of Paeony (TGP) has anti-inflammatory, immunomodulatory and analgesic effects and is widely used to treat RA. However, few studies investigated whether the therapeutic effect of TGP is associated with the inhibition of autoimmune response.

PURPOSE

The aim of this study was to investigate the effects and mechanisms of TGP on RA.

STUDY DESIGN

Type II collagen-induced arthritis (CIA) mouse model was used, and TGP and paeoniflorin were intragastrically treated.

METHODS

DBA/1 mice were divided into 5 groups: control, model, positive drug (paeoniflorin) and high- and low-dose TGP group. After 21 days of intragastric administration, the pathological change, inflammation expression and molecular mechanism of each group of mice were detected by Micro-CT, histochemical analysis, ELLSA, Western blot, RT-qPCR and flow cytometry.

RESULTS

Our study found that TGP treatment effectively improved inflammation and joint destruction in CIA mice. It reduced the production of serum IgG2a and pro-inflammatory cytokines, including serum interleukin (IL)-21, tumor necrosis factor (TNF)-α and IL-6, and the phosphorylation of NF-κB p65 and STAT3 in a dose-dependent manner. More importantly, TGP could suppress the frequency of germinal center B cells and Tfh cells in the spleen.

CONCLUSION

TGP can not only improve symptoms, but also inhibit bone destruction. The therapeutic effect of TGP on CIA is mainly achieved by inhibiting spleen Tfh cell differentiation and GC formation through STAT3 signaling pathway.

Chemokines in rheumatic diseases: pathogenic role and therapeutic implications

Chemokines, a family of small secreted chemotactic cytokines, and their G protein-coupled seven transmembrane spanning receptors control the migratory patterns, positioning and cellular interactions of immune cells. The levels of chemokines and their receptors are increased in the blood and within inflamed tissue of patients with rheumatic diseases, such as rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, vasculitis or idiopathic inflammatory myopathies. Chemokine ligand-receptor interactions control the recruitment of leukocytes into tissue, which are central to the pathogenesis of these rheumatic diseases. Although the blockade of various chemokines and chemokine receptors has yielded promising results in preclinical animal models of rheumatic diseases, human clinical trials have, in general, been disappointing. However, there have been glimmers of hope from several early-phase clinical trials that suggest that sufficiently blocking the relevant chemokine pathway might in fact have clinical benefits in rheumatic diseases. Hence, the chemokine system remains a promising therapeutic target for rheumatic diseases and requires further study.

The roles of chemokine (C-X-C motif) ligand 13 in spinal cord ischemia-reperfusion injury in rats

Spinal cord ischemia-reperfusion injury (SCII) remains an unresolved complication and its underlying mechanism has not been fully elucidated. In this study, we studied the role of chemokine (C-X-C motif) ligand 13 (CXCL13) in a rat model of SCII. We examined the time course and cellular distribution of CXCL13 protein in rats after SCII. The effects of siRNA targeting CXCL13 or C-X-C chemokine receptor type 5 (CXCR5) in SCII were also investigated. Neurological function, histological assessment, and disruption of the blood-spinal cord barrier (BSCB) were evaluated. The expression levels of CXCL13, CXCR5, phosphorylated extracellular signal-regulated kinase (p-ERK), caspase-3, interleukin 6 (IL-6), TNF-α, and IL-1β were determined. We found that SCII resulted in impaired hind limb function and increased the expression of CXCL13. In addition, CXCL13 expression demonstrated the most pronounced effect at 24 h after SCII. We reveal that CXCL13 protein was co-expressed with the mature neuron marker NeuN and the microglial marker IBA-1 in spinal cord tissues of model rats. SCII also increased the expression of CXCR5, p-ERK, caspase-3, IL-6, TNF-α, and IL-1β at 24 h after SCII. Pre-treatment with CXCL13 siRNA protected the rats against SCII and decreased the expression of signalling pathway proteins and proinflammatory cytokines mentioned above. CXCR5 siRNA also showed similar protective effects. These findings indicate that CXCL13 is involved in SCII. The CXCL13/CXCR5 axis promotes the development of SCII, possibly via ERK-mediated pathways. Targeting the mechanism of CXCL13 involved in the development of SCII might be a potential approach for the treatment of this condition.

Two populations of circulating PD-1hiCD4 T cells with distinct B cell helping capacity are elevated in early rheumatoid arthritis

Objective

A novel population of B helper cells, phenotypically CD4+CXCR5−PD-1hi, has been described in the synovial tissues and peripheral blood of seropositive RA patients, and termed ‘peripheral helper T’ (Tph) cells. Contrary to CD4+CXCR5+PD-1hi follicular helper T (Tfh), Tph cells are not located in lymphoid organs but accumulate in inflamed tissues. Our objective was to study the frequency of circulating Tph (cTph) and circulating Tfh cell counterparts (cTfh) in patients with early RA (eRA).

Methods

Freshly isolated peripheral blood mononuclear cells from 56 DMARD-naïve eRA patients and 56 healthy controls were examined by flow cytometry. Autologous cocultures of naïve or memory B cells were established with isolated peripheral blood Tph or Tfh cells.

Results

Seropositive (RF+ and/or ACPA+, n = 38) but not seronegative eRA patients (n = 18) demonstrated increased frequencies and absolute numbers of cTph and cTfh cells. cTph but not cTfh cells expressed CCR2. Those eRA patients who experienced a significant clinical improvement at 12 months demonstrated a marked decrease of their cTph cell numbers whereas their cTfh cell numbers remained unchanged. Both isolated Tph and isolated Tfh cells were able to induce maturation of memory B cells, whereas only Tfh cells could differentiate naïve B cells.

Conclusion

Two populations of PD-1hiCD4 T cells with distinct phenotype and B cell helping capacity are increased in the peripheral blood of seropositive eRA patients. Whereas cTph cells are present only in patients with an active disease, cTfh cells seem to be constitutively elevated.

T-cells interact with B cells, dendritic cells, and fibroblast-like synoviocytes as hub-like key cells in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory synovitis-based systemic disease characterized by invasive joint inflammation and synovial hyperplasia, which can lead to arthrentasis and defunctionalization. Previous research has shown that T cells, B cells, dendritic cells (DCs), and fibroblast-like synoviocytes (FLSs) play vital roles in the regulation of RA. Both T follicular helper (Tfh) cells and helper T (Th) 17 cells play immunomodulatory roles in RA. Moreover, interleukin-23 (IL-23), and IL-17 are vital to the pathogenesis of RA. T cells behave as a hub, in that B cells, DCs, and FLSs can interact with T cells to inhibit their activation and interfere with the process of RA. T cells cooperate with B cells, DCs, and FLSs to maintain the stability of the immune system under physiological conditions. However, under pathological conditions, the balance is disrupted, and the interaction of T cells with other cells may intensify disease progression. This review focuses on the interaction of T cells with B cells, DCs, and FLSs in different tissues and organs of RA patients and animal models, and highlight that the interplay between immune cells may underline the unique function of T cells and the application prospect of targeting T cell treatment for RA.

Enhanced IL-6/phosphorylated STAT3 signaling is related to the imbalance of circulating T follicular helper/T follicular regulatory cells in patients with rheumatoid arthritis

Background

Follicular helper T (Tfh) cells are specialized in helping B lymphocytes, which play a central role in autoimmune diseases that have a major B cell component, such as in rheumatoid arthritis (RA). Follicular regulatory T (Tfr) cells control the over-activation of Tfh and B cells in germinal centers. Dysregulation of Tfh cells and Tfr cells has been reported to be involved in the pathogenesis of some autoimmune diseases. However, the balance of Tfh and Tfr cells, and their roles in the development and progression of RA are still not clear.

Methods

In this study, we enrolled 44 patients with RA (20 patients with active RA and 24 patients with inactive RA) and 20 healthy controls, and analyzed the frequencies of circulating Tfh and Tfr cells, expression of programmed death-1 (PD-1), inducible co-stimulator (ICOS), intracellular IL-21, and pSTAT3 in Tfh cells, and serum levels of IL-6. The correlation among these parameters and that of Tfh or Tfr cells with disease activity were also analyzed.

Results

Patients with RA (especially active RA) had higher frequencies of Tfh cells, but lower percentages of Tfr cells, thereby resulting in elevated ratios of Tfh/Tfr. Expression levels of PD-1 and IL-21 in Tfh cells were higher in patients with RA than in healthy subjects, while no difference in ICOS expression was observed between patients and controls. Both pSTAT3 expression and serum IL-6 levels increased in patients with RA, and positive correlation between them was observed. Additionally, pSTAT3 expression was positively correlated with Tfh cell frequency. The Disease Activity Score in 28 joints based on C-reactive protein (DAS28-CRP) was negatively correlated with Tfr cell frequency, but was positively correlated with both Tfh/Tfr ratio and PD-1 expression.

Conclusions

Results demonstrated that enhanced IL-6/pSTAT3 signaling may contribute to promotion of Tfh cells, consequently skewing the ratio of Tfh to Tfr cells, which may be crucial for disease progression in RA.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1690-0) contains supplementary material, which is available to authorized users.

T Cell/B Cell Collaboration and Autoimmunity: An Intimate Relationship

Co-ordinated interaction between distinct cell types is a hallmark of successful immune function. A striking example of this is the carefully orchestrated cooperation between helper T cells and B cells that occurs during the initiation and fine-tuning of T-cell dependent antibody responses. While these processes have evolved to permit rapid immune defense against infection, it is becoming increasingly clear that such interactions can also underpin the development of autoimmunity. Here we discuss a selection of cellular and molecular pathways that mediate T cell/B cell collaboration and highlight how in vivo models and genome wide association studies link them with autoimmune disease. In particular, we emphasize how CTLA-4-mediated regulation of CD28 signaling controls the engagement of secondary costimulatory pathways such as ICOS and OX40, and profoundly influences the capacity of T cells to provide B cell help. While our molecular understanding of the co-operation between T cells and B cells derives from analysis of secondary lymphoid tissues, emerging evidence suggests that subtly different rules may govern the interaction of T and B cells at ectopic sites during autoimmune inflammation. Accordingly, the phenotype of the T cells providing help at these sites includes notable distinctions, despite sharing core features with T cells imparting help in secondary lymphoid tissues. Finally, we highlight the interdependence of T cell and B cell responses and suggest that a significant beneficial impact of B cell depletion in autoimmune settings may be its detrimental effect on T cells engaged in molecular conversation with B cells.

Insights Into the Molecular Mechanisms of T Follicular Helper-Mediated Immunity and Pathology

T follicular helper (Tfh) cells play key role in providing help to B cells during germinal center (GC) reactions. Generation of protective antibodies against various infections is an important aspect of Tfh-mediated immune responses and the dysregulation of Tfh cell responses has been implicated in various autoimmune disorders, inflammation, and malignancy. Thus, their differentiation and maintenance must be closely regulated to ensure appropriate help to B cells. The generation and function of Tfh cells is regulated by multiple checkpoints including their early priming stage in T zones and throughout the effector stage of differentiation in GCs. Signaling pathways activated downstream of cytokine and costimulatory receptors as well as consequent activation of subset-specific transcriptional factors are essential steps for Tfh cell generation. Thus, understanding the mechanisms underlying Tfh cell-mediated immunity and pathology will bring into spotlight potential targets for novel therapies. In this review, we discuss the recent findings related to the molecular mechanisms of Tfh cell differentiation and their role in normal immune responses and antibody-mediated diseases.

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.

The chemokine receptor CCR7 is a promising target for rheumatoid arthritis therapy

The chemokine receptor CCR7 and its ligands CCL19 and CCL21 guide the homing and positioning of dendritic and T cells in lymphoid organs, thereby contributing to several aspects of adaptive immunity and immune tolerance. In the present study, we investigated the role of CCR7 in the pathogenesis of collagen-induced arthritis (CIA). By using a novel anti-human CCR7 antibody and humanized CCR7 mice, we evaluated CCR7 as a target in this autoimmune model of rheumatoid arthritis (RA). Ccr7-deficient mice were completely resistant to CIA and presented severely impaired antibody responses to collagen II (CII). Selective CCR7 expression on dendritic cells restored arthritis severity and anti-CII antibody titers. Prophylactic and therapeutic treatment of humanized CCR7 mice with anti-human CCR7 mAb 8H3-16A12 led to complete resistance to CIA and halted CIA progression, respectively. Our data demonstrate that CCR7 signaling is essential for the induction of CIA and identify CCR7 as a potential therapeutic target in RA.

Signal Transducer and Activator of Transcription 3 Hyperactivation Associates With Follicular Helper T Cell Differentiation and Disease Activity in Rheumatoid Arthritis

Follicular helper T (Tfh) cells are the specialized CD4⁺ T cell subset that supports B cells to produce high-affinity antibodies and generate humoral memory. Not only is the function of Tfh cells instrumental to mount protect antibodies but also to support autoantibody production and promote systemic inflammation in autoimmune diseases. However, it remains unclear how the activation of Tfh cells is driven in autoimmune diseases. Here, we report that in patients with rheumatoid arthritis (RA), excessive generation of CXCR5⁺PD-1⁺ memory Tfh cells was observed and the frequency of memory Tfh cells correlated with disease activity score calculator for RA (DAS28). The differentiation of Tfh cells is dependent on signal transducer and activator of transcription 3 (STAT3), the key transcription factor downstream of cytokine signal pathways. A drastic increase of phosphorylated STAT3 (pSTAT3) in CD4⁺ T cells were detected in RA patients who also produced larger amounts of STAT3-stimulating cytokines, including IL-6, IL-21, IL-10, and leptin than those of healthy controls. Importantly, the phosphorylation status of STAT3 in CD4⁺ T cells positively correlated with the plasma concentration of IL-6 and the frequency of memory Tfh cells. This study reveals an IL-6-pSTAT3-Tfh immunoregulatory axis in the pathogenesis of RA and reinforces its candidature as biomarkers and targets for diagnosis and therapy.

ICOS Signaling Controls Induction and Maintenance of Collagen-Induced Arthritis

ICOS is a key costimulatory receptor facilitating differentiation and function of follicular helper T cells and inflammatory T cells. Rheumatoid arthritis patients were shown to have elevated levels of ICOS⁺ T cells in the synovial fluid, suggesting a potential role of ICOS-mediated T cell costimulation in autoimmune joint inflammation. In this study, using ICOS knockout and knockin mouse models, we found that ICOS signaling is required for the induction and maintenance of collagen-induced arthritis (CIA), a murine model of rheumatoid arthritis. For the initiation of CIA, the Tyr¹⁸¹-based SH2-binding motif of ICOS that is known to activate PI3K was critical for Ab production and expansion of inflammatory T cells. Furthermore, we found that Tyr¹⁸¹-dependent ICOS signaling is important for maintenance of CIA in an Ab-independent manner. Importantly, we found that a small molecule inhibitor of glycolysis, 3-bromopyruvate, ameliorates established CIA, suggesting an overlap between ICOS signaling, PI3K signaling, and glucose metabolism. Thus, we identified ICOS as a key costimulatory pathway that controls induction and maintenance of CIA and provide evidence that T cell glycolytic pathways can be potential therapeutic targets for rheumatoid arthritis.