Bcl6-Mediated Transcriptional Regulation of Follicular Helper T cells (TFH)

Bcl6 controls the stability and suppressive function of regulatory T cells in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) ranks as the sixth most common cancer globally. Most studies in HNSCC demonstrated that regulatory T (Treg) cells confine the anti-tumor activity of effector T cells which may contribute to the immune escape and uncontrolled tumor progression. Here, we uncovered that the specific abrogation of Bcl6 in Treg cells resulted in significantly delayed malignant transformation of 4NQO-induced tumorigenesis. Bcl6 deficiency impairs the lineage stability of Treg cells by down-regulating the histone H3K4 trimethylation. Importantly, Bcl6 inhibition repressed the tumor growth of murine HNSCC and exhibited synergistic effects with immune checkpoint blockade therapy. These findings suggest that Bcl6 can be exploited as a promising therapeutic target for HNSCC treatment.

Hierarchical protein nano-crystalline hydrogel with extracellular vesicles for ectopic lymphoid structure formation

Among cancer therapies, immune checkpoint blockade (ICB) has emerged as a prominent approach, substantially enhancing anti-tumor immune responses. However, the efficacy of ICB is often limited in the absence of a pre-existing immune response within the tumor microenvironment. Here, we introduce a novel hierarchical protein hydrogel platform designed to facilitate the formation of artificial tertiary lymphoid structures (aTLS), thereby improving ICB efficacy. Through the integration of self-assembling ferritin protein nanocages, rec1-resilin protein, and CP05 peptide, our hierarchical hydrogels provide a structurally supportive and functionally adaptive scaffold capable of on-demand self-repair in response to mild thermal treatments. The effective encapsulation of extracellular vesicles (EVs) via the CP05 peptide ensures the formation of aTLS with germinal center-like structures within the hierarchical hydrogel. We demonstrate that, combined with ICB therapy, EV-loaded hierarchical hydrogels also induce the TLS within the tumor, markedly promoting immune responses against ICB-resistant tumor. This bioactive hydrogel platform offers a versatile tool for enhancing a broad range of immunotherapies, with potential applications extending beyond TLS to other frameworks that support complex tissue architectures.

Type 1 Diabetes Depends on CD4-Driven Expression of the Transcriptional Repressor Bcl6

High-affinity islet autoantibodies predict type 1 diabetes in mice and humans and implicate germinal centers (GCs) in disease pathogenesis. T follicular helper (Tfh) cells are increased in individuals with type 1 diabetes and alterations in Tfh-like cells in the peripheral blood predicted individual responses to abatacept. Tfh cells support GC responses and depend on the transcriptional repressor BCL6 for their maturation. Therefore, we hypothesized that CD4-driven deletion of Bcl6 would disrupt essential T- and B-cell interactions in GCs to prevent type 1 diabetes. To test this hypothesis, we generated Bcl6fl/fl-CD4.Cre.NOD mice and found they were completely protected against diabetes. Insulitis severity and tertiary lymphoid structure organization were preserved in the pancreas of Bcl6fl/fl-CD4.Cre.NOD mice, which did not show decreases in CD4+, CD8+, and B-cell numbers in the pancreas and draining lymph nodes, relative to control Bcl6fl/fl.NOD mice. CD4-driven loss of functional BCL6 resulted in significantly reduced GC B-cell and Tfh-cell numbers in the pancreatic lymph nodes and pancreas at late prediabetic intervals. Spontaneous anti-insulin autoantibody was blunted in Bcl6fl/fl-CD4.Cre.NOD mice. These data highlight BCL6 as a novel therapeutic target in type 1 diabetes.

ARTICLE HIGHLIGHTS

Germinal center B cells and CD4+ T follicular helper cells are implicated in the pathogenesis of type 1 diabetes and depend upon the transcriptional repressor BCL6 for their maturation. This study tests the dependence of type 1 diabetes development on BCL6 expression in CD4+ cells. Data presented here show that CD4-driven loss of Bcl6 blocks germinal center formation, spontaneous insulin autoantibody production, and type 1 diabetes in nonobese diabetic mice, despite normal tertiary lymphoid structure formation in pancreatic islets. This study highlights BCL6 as a potential immunomodulatory target in type 1 diabetes.

The TET-TDG axis in T cells and biological processes

Ten-eleven translocation (TET) proteins are dioxygenases that sequentially oxidize the methyl group of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC). All three epigenetic modifications are intermediates in DNA demethylation. In the "passive" (replication-dependent) DNA demethylation pathway, sequential oxidation reactions by TETs are essential and modified cytosines (C) are diluted at each cycle of DNA replication. In the "active" (replication-independent) DNA demethylation pathway, both thymine DNA glycosylase (TDG) and TETs play important roles. TDG removes 5fC and 5caC from 5fC:G and 5caC:G base pairs and these modified bases are replaced by unmodified C via base excision repair. Through epigenetic regulation of DNA demethylation, TETs and TDG are involved in cell development, differentiation, and homeostasis. The interplay between TDG and TETs is involved in embryo development, stem cell differentiation, neural development, immune responses, and tumorigenesis. Loss-of-function mutations of TET proteins in immune cells are associated with a variety of abnormalities, including inflammation, cancer, and clonal hematopoiesis, a condition related to aging. Loss of TETs also has a significant impact on the plasticity and differentiation of T cells, which contributes to inflammation and cancer. In this review, we describe recent findings in functions of TETs in T cell plasticity and differentiation and the TET-TDG axis in selected biological processes.

Differential memory enrichment of cytotoxic CD4 T cells in Parkinson's disease patients reactive to α-synuclein

Parkinson's disease (PD) is a complex neurodegenerative disease with a largely unknown etiology. Although the loss of dopaminergic neurons in the substantia nigra pars compacta is the pathological hallmark of PD, neuroinflammation also plays a fundamental role in PD pathology. We have previously reported that PD patients have increased frequencies of T cells reactive to peptides from α-synuclein (α-syn). However, not all PD participants respond to α-syn. Furthermore, we have previously found that CD4 T cells from PD participants responding to α-syn (PD_R) are transcriptionally distinct from PD participants not responding to α-syn (PD_NR). To gain further insight into the pathology of PD_R participants, we investigated surface protein expression of 11 proteins whose genes had previously been found to be differentially expressed when comparing PD_R and healthy control participants not responding to α-syn (HC_NR). We found that Cadherin EGF LAG seven-pass G-type receptor 2 (CELSR2) was expressed on a significantly higher proportion of CD4 effector memory T cells (TEM) in PD_R compared to HC_NR. Single-cell RNA sequencing analysis of cells expressing or not expressing CELSR2 revealed that PD_R participants have elevated frequencies of activated TEM subsets and an almost complete loss of cytotoxic TEM cells. Flow cytometry analyses confirmed that Granulysin+ CD4 cytotoxic TEM cells are reduced in PD_R. Taken together, these results provide further insight into the perturbation of T cell subsets in PD_R, and highlights the need for further investigation into the role of Granulysin+ CD4 cytotoxic TEM in PD pathology.

Inhibitior of Bcl6 by FX1 protects DSS induced colitis mice through anti-inflammatory effects

Introduction

Inflammatory bowel disease (IBD) is a complex immune-mediated condition, and biologics are the most commonly used drugs for its treatment. However, there are still cases of ineffective treatment. B-cell lymphoma 6 (Bcl6), a transcriptional suppressor, is known to have regulatory effects on multiple immune-associated cell subsets. FX1, a novel specific BCL6 Bric-à-brac (BTB) inhibitor, has shown positive effects in many disease models, but its effects and mechanisms in IBD control remain unclear.

Methods

We observed colon length and DAI score of colitis mice after treatment. HE staining section was used to evaluate colonic injury, while the expression of colonic pro-inflammatory cytokines by RT-qPCR. And differences in immune cell subsets between the two groups was analyzed by flow cytometry. Additionally, IHC and RT-qPCR were employed to evaluate the expression of colonic tight junction proteins. Furthermore, RAW264.7 cells and co-cultured Caco2 cells were detected by ELISA and RT-qPCR.

Results

In the treat group, colitis symptoms in mice were significantly improved, and there was a decrease in proportion of macrophages and protection of intestinal mucosal integrity-indicating anti-inflammatory effects of FX1. In cell experiments, we found that FX1 decreased secretion of pro-inflammatory factors by macrophages and increased expression of tight junction proteins in Caco2 cells after co-culture.

Discussion

The experimental findings demonstrate the inhibitory effect of FX1 on inflammation in murine colitis model as well as its potential mechanism. BCL6 is a potential target for treating IBD.

T cell dysregulation in rheumatoid arthritis: Recent advances and natural product interventions

Autoimmune diseases result from chronic and dysregulated activation of the immune system, culminating in pathological self-tissue damage. These disorders are primarily driven by adaptive immune responses, particularly those mediated by T and B lymphocytes, which mistakenly target self-antigens expressed in host tissues. In rheumatoid arthritis (RA), the pathogenesis is closely associated with the emergence of tissue-invasive effector T cells and the functional impairment of regulatory T cells (Tregs), both of which play pivotal roles in disease progression. Therapeutic interventions targeting these dysregulated T cell populations have emerged as a promising strategy for RA management. Although synthetic immunosuppressants remain the mainstay of RA treatment, their long-term application is often hampered by adverse effects, diminished therapeutic efficacy, and poor patient adherence. These limitations highlight the critical need for the development of novel therapeutic approaches. Natural compounds derived from medicinal plants have been widely utilized in the clinical management of RA, with growing evidence supporting their immunomodulatory potential, particularly in restoring T cell-mediated immune tolerance. This review aims to provide a comprehensive overview of recent advances in understanding T cell dysregulation in RA and to elucidate the mechanisms through which natural compounds regulate immune responses. By integrating current findings, this work seeks to offer a theoretical foundation for the optimized use of natural compounds in the treatment of RA, while exploring their potential in advancing precision medicine and personalized therapeutic strategies.

T-Follicular Helper Cells and Their Role in Autoimmune Diseases

T-follicular helper (Tfh) cells, a specialized subset of CD4+ cells, are the immune mediators connecting cellular and humoral immunity, as they lead B-cell proliferation within germinal centers, and orchestrate their response, including activation, class switching, and production of a diverse array of high-affinity antibodies. Their interactions with B cells is regulated by a wide complex of transcriptional and cytokine-driven pathways. A major contribution of Tfh cells to autoimmune diseases is through their production of cytokines, particularly IL-21, which supports the proliferation and differentiation of autoreactive B cells. Elevated levels of circulating Tfh-like cells and IL-21 have been observed in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) correlating strongly with disease severity and autoantibody levels. The feedback loop between Tfh cells and IL-21 or other signal pathways, such as Bcl-6, ICOS, and PD-1, not only sustains Tfh cell function but also drives the continuous expansion of autoreactive B cells, leading to chronic inflammation through the production of high-affinity pathogenic autoantibodies. By understanding these interactions, Tfh pathways may serve as potential therapeutic targets, with IL-21, ICOS, and PD1 blockades emerging as promising innovative therapeutic strategies to manage autoimmune diseases. Although a variety of studies have been conducted investigating the role of Tfh cells in SLE and RA, this review aims to reveal the gap in the literature regarding the role of such subpopulations in the pathogenesis of other autoimmune diseases, such as Anca-associated vasculitis (AAV), and express the need to conduct similar studies. Tfh cell-related biomarkers can be used to assess disease activity and transform autoimmune disease treatment, leading to more personalized and effective care for patients with chronic autoimmune conditions.

Management of T-cell malignancies: Bench-to-bedside targeting of epigenetic biology

The peripheral T-cell lymphomas (PTCL) are the only disease for which four histone deacetylase (HDAC) inhibitors have been approved globally as single agents. Although it is not clear why the PTCL exhibit such a vulnerability to these drugs, understanding the biological basis for this activity is essential. Many lines of data have established that the PTCL exhibit marked sensitivity to other epigenetically targeted drugs, including EZH2 and DNMT3 (DNA-methyltransferase 3) inhibitors. Even more compelling is the finding that combinations of drugs targeting the epigenetic biology of PTCL are beginning to produce provocative data, leading some to wonder if these agents can replace historical chemotherapy regimens routinely used for patients with the disease. Simultaneously, the field has identified a spectrum of mutations in genes governing epigenetic biology in many subtypes of PTCL, although the T follicular helper lymphomas, including angioimmunoblastic T-cell lymphoma, appear to be particularly enriched for these genetic features. While the direct relationship between the presence of any one of these mutations and responsiveness to a particular epigenetic drug has yet to be established, it is increasingly accepted that the PTCL may be the prototypical epigenetic disease as no other form of cancer has exhibited such a vulnerability to this diversity of epigenetically targeted agents. Herein, we comprehensively review this esoteric and rapidly evolving field to identify themes and lessons from these experiences that may guide efforts to improve outcomes of patients with T-cell neoplasms. Furthermore, we will discuss how these concepts might be applied to the broader field of cancer medicine.

Activation-induced cytidine deaminase in tertiary lymphoid structures: dual roles and implications in cancer prognosis

Activation-induced cytidine deaminase (AID) serves as a critical molecular orchestrator in the germinal center (GC) reaction within secondary lymphoid organs (SLOs), driving the production of high-affinity antibodies through somatic hypermutation. While its pathological implications are well-documented - including ectopic expression in non-B cell populations and transcriptional dysregulation linked to hematological malignancies and solid tumorigenesis - the cellular provenance of AID in solid tumors remains an unresolved paradox. This review advances two principal hypotheses: (1) AID may derive from tertiary lymphoid structures (TLSs), ectopic immune niches mirroring SLO organization, and (2) exhibits context-dependent transcriptional duality, capable of both potentiating and suppressing gene expression based on microenvironmental cues. Through systematic analysis of AID/GC involvement across cancer subtypes, we delineate mechanistic connections between lymphoid neogenesis and tumor progression. Our examination extends to TLS architecture, revealing three critical dimensions: (i) structural organization and cellular heterogeneity, (ii) developmental trajectories, and (iii) bidirectional interactions with tumor microenvironments. Crucially, we establish functional parallels between tumor-infiltrating B cells (TIL-Bs) in SLOs versus TLSs, while elucidating the differential roles of AID in canonical GC versus TLS-associated GC formation. This synthesis ultimately proposes that AID's functional dichotomy - acting as both oncogenic collaborator and tumor suppressor - underlies the paradoxical prognostic associations observed with TLS presence across malignancies. The review thereby provides a conceptual framework reconciling AID's dual functionality with the context-dependent immunobiology of tumor-associated lymphoid structures.

Molecular Biology and Functions of T Follicular Helper Cells in Cancer and Immunotherapy

T follicular helper (Tfh) cells are integral to the germinal center (GC) response and the development of potent humoral immunity. By priming B cells, Tfh cells can initiate both extrafollicular and GC-dependent Ab responses. The dynamic physical interactions between Tfh and B cells constitute the primary platform for Tfh cells to provide essential "help" factors to B cells, as well as for reciprocal signaling from B cells to sustain the helper state of Tfh cells. In recent years, significant advancements have been made in understanding the diverse roles of Tfh cells across various diseases, particularly in cancer. Notably, beyond the classical GC-Tfh cells, it is increasingly recognized that the Tfh cell phenotype is highly heterogeneous and dynamic, which adds complexity to their roles in disease contexts. This review aims to encapsulate progress in Tfh cell biology, with a focus on their role in cancer and immunotherapy.

Role of T Follicular Helper Cells in Viral Infections and Vaccine Design

T follicular helper (Tfh) cells are a specialized subset of CD4+ T lymphocytes that are essential for the development of long-lasting humoral immunity. Tfh cells facilitate B lymphocyte maturation, promote germinal center formation, and drive high-affinity antibody production. Our current knowledge of Tfh interactions with the humoral immune system effectors suggests that they have a critical role in supporting the immune response against viral infections. This review discusses the mechanisms through which Tfh cells influence anti-viral immunity, highlighting their interactions with B cells and their impact on antibody quality and quantity. We explore the role of Tfh cells in viral infections and examine how vaccine design can be improved to enhance Tfh cell responses. Innovative vaccine platforms, such as mRNA vaccines and self-assembling protein nanoplatforms (SAPNs), are promising strategies to enhance Tfh cell activation. Their integration and synergistic combination could further enhance immunity and Tfh responses (SAPN-RNA vaccines). In summary, we provide a comprehensive overview of the current insights into Tfh cells' role during viral infections, emphasizing their potential as strategic targets for innovative vaccine development.

Distinct features of a peripheral T helper subset that drives the B cell response in dengue virus infection

Dengue-virus-induced humoral immunity can increase the risk of severe disease, but the factors influencing this response are poorly understood. Here, we investigate the contribution of CD4+ T cells to B cell responses in human dengue infection. We identify a dominant peripheral PD-1+ T cell subset that accumulates in severe patients and could induce B cell differentiation via interleukin-21 (IL-21)-related pathway. Single-cell analyses reveal heterogeneity within PD-1+ cells, demonstrating the coexistence of subsets with "helper" (IL-21+) or "cytotoxic" characteristics. The IL-21+ subset displays a distinct clonotypic and transcriptomic signature compared to follicular helper T cells and persists as a memory in lymph nodes. Notably, we show that the IL-21+ subset seems to majorly drive the extrafollicular B cell responses in dengue. Our study establishes the peripheral IL-21+ subset as a potential determinant of the humoral response to dengue virus infection. These findings provide important insights into the T-cell-dependent regulation of humoral responses and can inform the design of effective dengue vaccines.

CD301b+ dendritic cell-derived IL-2 dictates CD4+ T helper cell differentiation

T helper (Th) cell differentiation is fundamental to functional adaptive immunity. Different subsets of dendritic cells (DC) preferentially induce different types of Th cells, but the DC-derived mechanism for Th type 2 (Th2) differentiation is not fully understood. Here, we show that in mice, CD301b+ DCs, a major Th2-inducing DC subset, drive Th2 differentiation through cognate interaction by rapidly inducing IL-2 receptor signalling in CD4+ T cells. Mechanistically, CD40 engagement prompts IL-2 production selectively from CD301b+ DCs to maximize CD25 expression in CD4+ T cells, which instructs the Th2 fate decision, while simultaneously skewing CD4+ T cells away from the T follicular helper fate. Moreover, CD301b+ DCs utilize their own CD25 to facilitate directed action of IL-2 toward cognate CD4+ T cells, as genetic deletion of CD25 in CD301b+ DCs results in reduced IL-2-mediated signalling in antigen-specific CD4+ T cells and hence their Th2 differentiation. These results highlight the critical role of DC-intrinsic CD40-IL-2 axis in Th cell fate decision.

Dnmt3a-dependent de novo DNA methylation enforces lineage commitment and preserves functionality of memory Th1 and Tfh cells

Following acute viral infection, naïve CD4+ T cells differentiate into T follicular helper (Tfh) and T helper 1 (Th1) cells that generate long-lived memory cells. However, it is unclear how memory Tfh and Th1 cells maintain their lineage commitment. We demonstrate that Tfh and Th1 lineages acquire distinct Dnmt3a-dependent de novo DNA methylation programs that are preserved into memory. Dnmt3a deletion impairs lineage commitment and functionality of memory Th1 and Tfh cells, resulting in aberrant Runx1 upregulation that represses germinal center Tfh cell differentiation. In contrast, transient pharmacological DNA methyltransferase inhibition during priming impairs repression of Tfh-associated genes while properly silencing Runx1, and results in enhanced Tfh cell functionality in primary and secondary responses to viral infections. Together, these findings demonstrate that Dnmt3a-mediated epigenetic programing is required to enforce T helper lineage commitment and preserve Tfh and Th1-specific functions during the recall response to infection, and reveal novel strategies to improve long-lived adaptive immunity against infectious diseases.

Therapeutic development towards T follicular helper cells as a molecular target in myasthenia gravis disease

This review intends to gather literature to provide a comprehensive understanding of the molecular mechanisms and role of T follicular helper cells (Tfh) in the interaction with germinal centers (GCs) in Myasthenia Gravis (MG) disease regarding new developments focusing on Tfh as a therapeutic target and its key regulator B cell lymphoma 6 (Bcl6). Tfh cells are CD4+ T cells specialized in providing signals for the activation and maturation of B cells plus the formation and maintenance of GCs; the role of Bcl6 stands as the key transcriptional factor for the survival of GCs and promotion of Tfh generation. Previous studies have demonstrated gene therapy to be beneficial by achieving re-establishment of "immune homeostasis" and amelioration of the proinflammatory process.

Full-length mRNA sequencing resolves novel variation in 5' UTR length for genes expressed during human CD4 T-cell activation

Isoform sequencing (Iso-Seq) uses long-read technology to produce highly accurate full-length reads of mRNA transcripts. Visualization of individual mRNA molecules can reveal new details of transcript variation within understudied portions of mRNA, such as the 5' untranslated region (UTR). Differential 5' UTRs may contain motifs, upstream open reading frames (uORFs), and secondary structures that can serve to regulate translation or further indicate changes in promoter usage, where transcriptional control may impact protein expression levels. To begin to explore isoform variation during T-cell activation, we generated the first Iso-Seq reference transcriptome of activated human CD4 T cells. Within this dataset, we discovered many novel splice- and end-variant transcripts. Remarkably, one in every eight genes expressed in our dataset was found to have a notable proportion of transcripts with 5' UTR lengthened by over 100 bp compared to the longest corresponding UTR within the Gencode dataset. Among these end-variant transcripts, two novel isoforms were identified for CXCR5, a chemokine receptor associated with T follicular helper cell (Tfh) function and differentiation. When investigated in a model cell system, these lengthened UTR conferred reduced transcript stability and, for one of these isoforms, short uORFs introduced by the added length altered protein expression kinetics. This study highlights instances in which current reference databases are incomplete relative to the information obtained by long-read sequencing of intact mRNA. Iso-Seq is thus a promising approach to better understanding the plasticity of promoter usage, alternative splicing, and UTR sequences that influence RNA stability and translation efficiency.

IRF5 Controls Plasma Cell Generation and Antibody Production via Distinct Mechanisms Depending on the Antigenic Trigger

Elevated levels of serum autoantibodies are a hallmark of systemic lupus erythematosus (SLE) and are produced by plasma cells in response to a variety of antigenic triggers. In SLE, the triggers are complex and may include both T cell-dependent/-independent and TLR-dependent/-independent mechanisms of immune activation, which ultimately contributes to the significant immune dysregulation seen in patients at the level of cytokine production and cellular activation (B cells, T cells, dendritic cells, neutrophils and macrophages). Interferon regulatory factor 5 (IRF5) has been identified as an autoimmune susceptibility gene and polymorphisms in IRF5 associate with altered expression and hyper-activation in distinct SLE immune cell subsets. To gain further insight into the mechanisms that drive IRF5-mediated SLE immune activation, we characterised wild-type (WT) and Irf5 -/- Balb/c mice in response to immunisation. WT and Irf5 -/- Balb/c mice were immunised to activate various signalling pathways in vivo followed by systemic immunophenotyping and detection of antibody production by multi-colour flow cytometry and ELISPOT. We identified two pathways, TLR9-dependent and T cell-dependent that resulted in IRF5 cell type-specific function. Immunisation with either CpG-B + Alum or NP-KLH + Alum but not with R848 + Alum, NP-LPS + Alum or NP-Ficoll+Alum resulted in decreased plasma cell generation and reduced antibody production in Irf5 -/- mice. Notably, the mechanism(s) leading to this downstream phenotype was distinct. In CpG-B + Alum immunised mice, we found reduced activation of plasmacytoid dendritic cells, resulting in reduced IFNα and IL6 production in Irf5 -/- mice. Conversely, mice immunised with NP-KLH + Alum had reduced numbers of T follicular helper cells and germinal centre B cells with reduced expression of Bcl6 in Irf5 -/- mice. Moreover, T follicular helper cells from Irf5 -/- mice were functionally defective. Even though the downstream phenotype of reduced antibody production in Irf5 -/- mice was conserved between T cell-dependent and TLR9-dependent immunisation, the mechanisms leading to this phenotype were antigen- and cell type-specific.

CD6 regulates CD4 T follicular helper cell differentiation and humoral immunity during murine coronavirus infection

During activation, the T cell transmembrane receptor CD6 becomes incorporated into the T cell immunological synapse where it can exert both co-stimulatory and co-inhibitory functions. Given the ability of CD6 to carry out opposing functions, this study sought to determine how CD6 regulates early T cell activation in response to viral infection. Infection of CD6-deficient mice with a neurotropic murine coronavirus resulted in greater activation and expansion of CD4 T cells in the draining lymph nodes. Further analysis demonstrated that there was also preferential differentiation of CD4 T cells into T follicular helper cells, resulting in accelerated germinal center responses and emergence of high-affinity virus-specific antibodies. Given that CD6 conversely supports CD4 T cell activation in many autoimmune models, we probed potential mechanisms of CD6-mediated suppression of CD4 T cell activation during viral infection. Analysis of CD6 binding proteins revealed that infection-induced upregulation of Ubash3a, a negative regulator of T cell receptor (TCR) signaling, was hindered in CD6-deficient lymph nodes. Consistent with greater T cell activation and reduced UBASH3a activity, the T cell receptor signal strength was intensified in CD6-deficient CD4 T cells. These results reveal a novel immunoregulatory role for CD6 in limiting CD4 T cell activation and deterring CD4 T follicular helper cell differentiation, thereby attenuating antiviral humoral immunity.

IMPORTANCE

CD6 monoclonal blocking antibodies are being therapeutically administered to inhibit T cell activation in autoimmune disorders. However, the multifaceted nature of CD6 allows for multiple and even opposing functions under different circumstances of T cell activation. We therefore sought to characterize how CD6 regulates T cell activation in the context of viral infections using an in vivo murine coronavirus model. In contrast to its role in autoimmunity, but consistent with its function in the presence of superantigens, we found that CD6 deficiency enhances CD4 T cell activation and CD4 T cell help to germinal center-dependent antiviral humoral responses. Finally, we provide evidence that CD6 regulates transcription of its intracellular binding partner UBASH3a, which suppresses T cell receptor (TCR) signaling and consequently T cell activation. These findings highlight the context-dependent flexibility of CD6 in regulating in vivo adaptive immune responses, which may be targeted to enhance antiviral immunity.

T follicular helper and memory B cells in IgE recall responses

IgE antibodies raised against innocuous environmental antigens cause allergic diseases like allergic rhinitis, food allergy, and allergic asthma. While some allergies are often outgrown, others (peanut, shellfish, tree nut) are lifelong in the majority of individuals. Lifelong allergies are the result of persistent production of allergen-specific IgE. However, IgE antibodies and the plasma cells that secrete them tend to be short-lived. Persistent allergen-specific IgE titres are thought to be derived from the continued renewal of IgE plasma cells from memory B cells in response to allergen encounters. The initial generation of allergen-specific IgE is driven by B cell activation by IL-4 producing Tfh cells, but the cellular and molecular mechanisms of the long-term production of IgE are poorly characterized. This review investigates the mechanisms governing IgE production and Tfh activation in the primary and recall responses, towards the objective of identifying molecular targets for therapeutic intervention that durably inactivate the IgE recall response.

Efficient gene deletion of Integrin alpha 4 in primary mouse CD4 T cells using CRISPR RNA pair-mediated fragmentation

The functional specialization of CD4 T lymphocytes into various subtypes, including TH1 and TFH cells, is crucial for effective immune responses. TFH cells facilitate B cell differentiation within germinal centers, while TH1 cells are vital for cell-mediated immunity against intracellular pathogens. Integrin α4, a cell surface adhesion molecule, plays significant roles in cell migration and co-stimulatory signaling. In this study, we investigated the role of Integrin α4 in regulating TFH and TH1 cell populations during acute viral infection using CRISPR-Cas9 gene editing. To effectively delete the Itga4 in primary mouse CD4 T cells, we selected various combinations of crRNAs and generated ribonucleoprotein complexes with fluorochrome-conjugated tracrRNAs and Cas9 proteins. These crRNA pairs enhanced gene deletion by generating deletions in the gene. By analyzing the effects of Itga4 deficiency on TFH and TH1 cell differentiation during acute LCMV infection, we found that optimized crRNA pairs significantly increased the TH1 cell population. Our results highlight the importance of selecting and combining appropriate crRNAs for effective CRISPR-Cas9 gene editing in primary CD4 T cells. Additionally, our study demonstrates the role of Integrin α4 in regulating the differentiation of CD4 T cells, suggesting the potential molecular mechanisms driving T cell subset differentiation through integrin targeting.

T follicular helper cell is essential for M2 macrophage polarization and pulmonary vascular remodeling in hypoxia-induced pulmonary hypertension

BACKGROUND

Hypoxia-induced pulmonary hypertension (HPH) is a subgroup of type 3 pulmonary hypertension that may cause early right ventricular failure and eventual cardiac failure, which lacks potential therapeutic targets. Our previous research demonstrated that T follicular helper (TFH) cells that produce IL-21 were involved in HPH. However, the molecular mechanisms of TFH/IL-21-mediated pathogenesis of HPH have been elusive. Here we investigate the role of TFH cells and IL-21 in HPH.

METHODS

Studies were performed in C57BL/6 mice or IL-21 knockout mice exposed to chronic hypoxia to induce PH, and examined by hemodynamics. Molecular and cellular studies were performed in mouse lung and pulmonary arterial smooth muscle cells (PASMCs). M2 signature gene (Fizz1), M1 signature genes (iNos, IL-12β and MMP9), GC B cell and its marker GL-7, caspase-1, M2 macrophages, TFH cells, Bcl-6 and IL-21 level were measured. Proliferation rate of PASMCs was measured by EdU. Pyroptosis was assessed using Hoechst 33,342/PI double fluorescent staining.

RESULTS

In response to chronic hypoxia exposure-induced pulmonary hypertension, IL-21-/- mice or downregulation of TFH cells in WT mice developed blunted pulmonary hypertension, attenuated pulmonary vascular remodelling. Furthermore, chronic hypoxia exposure significantly increased the germinal center (GC) B cell responses, which were not present in IL-21-/- mice or downregulation of TFH cells in WT mice. Importantly, IL-21 promoted the polarization of primary alveolar macrophages toward the M2 phenotype. Consistently, significantly enhanced expression of M2 macrophage marker Fizz1 were detected in the bronchoalveolar lavage fluid of HPH mice. Moreover, alveolar macrophages that had been cultivated with IL-21 promoted PASMCs proliferation and pyroptosis in vitro, while a selective CX3CR1 antagonist, AZD8797 (AZD), significantly attenuated the proliferation and pyroptosis of the PASMCs. Finally, ECM1 knockdown promoted IL-2-STAT5 signaling and inhibited Bcl-6 signaling to inhibit TFH differentiation in HPH.

CONCLUSIONS

TFH/IL-21 axis amplified pulmonary vascular remodelling in HPH. This involved M2 macrophage polarization, PASMCs proliferation and pyroptosis. These data suggested that TFH/IL-21 axis may be a novel therapeutic target for the treatment of HPH.

Concomitant loss of TET2 and TET3 results in T cell expansion and genomic instability in mice

Ten eleven translocation (TET) proteins are tumor suppressors that through their catalytic activity oxidize 5-methylcytosine to 5-hydroxymethylcytosine, to promote DNA demethylation and to regulate gene expression. Notably, TET2 is one of the most frequently mutated genes in hematological malignancies, including T cell lymphomas. However, murine models with deletion of TET2 do not exhibit T cell expansion, presumably due to redundancy with other members of the TET family of proteins. In order to gain insight on the TET mediated molecular events that safeguard T cells from aberrant proliferation we performed serial adoptive transfers of murine CD4 T cells that lack concomitantly TET2 and TET3 to fully immunocompetent congenic mice. Here we show a progressive acquisition of malignant traits upon loss of TET2 and TET3 that is characterized by loss of genomic integrity, acquisition of aneuploidy and upregulation of the protooncogene Myc.

The transcriptional repressor B cell lymphoma 6 regulates CXCR3 chemokine and human leukocyte antigen II expression in endothelial cells

Interferon gamma (IFN-γ) induces an endothelial proimmunogenic phenotype through the JAK/STAT1 pathway, which can shape the activation of alloreactive leukocytes in transplant rejection. In immune cells, the DNA-binding protein B cell lymphoma 6 (BCL6) controls the transcription of inflammatory genes. This study tested if BCL6 modulates IFN-γ-induced gene expression in endothelial cells. In vitro, BCL6 was IFN-γ-inducible in primary human endothelium, along with CXCR3 chemokines and human leukocyte antigen (HLA). BCL6, HLA II, and CXCL9 were also increased in human cardiac transplants during acute rejection. Knockdown of BCL6 augmented, whereas overexpression and BTB domain inhibitors (BCL6-BTBi) suppressed, HLA II and CXCR3 chemokine expression but not HLA I. Further, BCL6 had a greater effect on HLA-DR and DP but was less involved in regulating HLA-DQ expression. The effect correlated with BCL6 binding motifs in or near affected genes. The BCL6 DNA recognition sequence was highly similar to that of STAT1, and BTBi reduced STAT1's transcriptional activity in vitro. Our results show for the first time that BCL6 selectively controls IFN-γ-induced endothelial gene expression, advancing our understanding of the endogenous mechanisms regulating donor immunogenicity.

The conformational epitope of Ara h 5 was crucial to the severe reactivity of peanut allergy

Conformational epitopes are associated with the development of food allergic tolerance and the severity of food allergy. Peanut can trigger severe anaphylactic reactions, however, the reason behind the severe allergic reactions caused by peanut remains unexplained. The purpose of this article was to provide an explanation for the severe allergy caused by peanut, focusing on the conformational epitopes of Ara h 5 and Ara h 8 allergens that exhibit cross-reactivity with asthma reactions. Ara h 5 and Ara h 8 proteins were prepared by an Escherichia coli expression system. IgE reactivity of 37 patients with allergy toward Ara h 5 and Ara h 8 allergens was assessed by using IgE-binding assays, dot blot and western blot. The allergenicity of Ara h 5 and Ara h 8 protein was analysed in mouse model. Conformational IgE epitopes of Ara h 5 was identified using phage peptide library and the Pepitope Server. Compared to Ara h 8, the conformational epitope of Ara h 5 protein was crucial in the process of sensitization. Ara h 5 showed a stronger IgE reactivity and the ability to induce β-hexosaminidase release. Ara h 5 caused more severe lung inflammation than Ara h 8 protein. While Ara h 8 caused more severe intestinal inflammation than Ara h 5. The results showed that the conformational epitope sequences of Ara h 5 were WETIYSR and FHWWYLK. The results provide a theoretical basis for the production of hypoallergenic peanut protein and the immunotherapy of peanut allergy.

The active form of vitamin D (calcitriol) promotes CXCR5 expression during follicular helper T cell differentiation

Follicular helper T (Tfh) cells promote B cell differentiation and antibody production in the B cell follicles of secondary lymphoid organs. Tfh cells express their signature transcription factor BCL6, interleukin (IL)-21, and surface molecules including inducible T cell costimulator (ICOS), programmed cell death-1 (PD-1), and C-X-C motif chemokine receptor 5 (CXCR5). Migration of Tfh cells to B cell follicles largely depends on the CXCR5 expression induced by interactions with antigen-presenting dendritic cells in the T cell area. How Tfh cells acquire sufficient levels of CXCR5 expression, however, has remained unclear. Using our in vitro culture system to generate CXCR5low Tfh-like cells from naive CD4+ T cells with IL-6 in the absence of other cell types, we found that the active form of vitamin D, calcitriol, markedly enhanced CXCR5 expression after the release from persistent T cell receptor (TCR) stimulation. CH-223191, an aryl hydrocarbon receptor antagonist, further enhanced CXCR5 expression. IL-12 but not IL-4, in place of IL-6, also supported calcitriol to enhance CXCR5 expression even before the release from TCR stimulation, whereas the cell viability sharply decreased after the release. The Tfh-like cells generated with IL-6 and calcitriol exhibited chemotaxis toward C-X-C motif chemokine ligand 13 (CXCL13), expressed IL-21, and helped B cells to produce IgG antibodies in vitro more efficiently than Tfh-like cells generated without added calcitriol. Calcitriol injections into antigen-primed mice increased the proportion of CXCR5+PD-1+CD4+ cells in their lymphoid organs, and enhanced T cell entry into B cell follicles. These results suggest that calcitriol promotes CXCR5 expression in developing Tfh cells and regulates their functional differentiation.

Complimentary vertebrate Wac models exhibit phenotypes relevant to DeSanto-Shinawi Syndrome

Monogenic syndromes are associated with neurodevelopmental changes that result in cognitive impairments, neurobehavioral phenotypes including autism and attention deficit hyperactivity disorder (ADHD), and seizures. Limited studies and resources are available to make meaningful headway into the underlying molecular mechanisms that result in these symptoms. One such example is DeSanto-Shinawi Syndrome (DESSH), a rare disorder caused by pathogenic variants in the WAC gene. Individuals with DESSH syndrome exhibit a recognizable craniofacial gestalt, developmental delay/intellectual disability, neurobehavioral symptoms that include autism, ADHD, behavioral difficulties and seizures. However, no thorough studies from a vertebrate model exist to understand how these changes occur. To overcome this, we developed both murine and zebrafish Wac/wac deletion mutants and studied whether their phenotypes recapitulate those described in individuals with DESSH syndrome. We show that the two Wac models exhibit craniofacial and behavioral changes, reminiscent of abnormalities found in DESSH syndrome. In addition, each model revealed impacts to GABAergic neurons and further studies showed that the mouse mutants are susceptible to seizures, changes in brain volumes that are different between sexes and relevant behaviors. Finally, we uncovered transcriptional impacts of Wac loss of function that will pave the way for future molecular studies into DESSH. These studies begin to uncover some biological underpinnings of DESSH syndrome and elucidate the biology of Wac, with advantages in each model.

Systemic inflammation and lymphocyte activation precede rheumatoid arthritis

Some autoimmune diseases, including rheumatoid arthritis (RA), are preceded by a critical subclinical phase of disease activity. Proactive clinical management is hampered by a lack of biological understanding of this subclinical 'at-risk' state and the changes underlying disease development. In a cross-sectional and longitudinal multi-omics study of peripheral immunity in the autoantibody-positive at-risk for RA period, we identified systemic inflammation, proinflammatory-skewed B cells, expanded Tfh17-like cells, epigenetic bias in naive T cells, TNF+IL1B+ monocytes resembling a synovial macrophage population, and CD4 T cell transcriptional features resembling those suppressed by abatacept (CTLA4-Ig) in RA patients. Our findings characterize pathogenesis prior to clinical diagnosis and suggest the at-risk state exhibits substantial immune alterations that could potentially be targeted for early intervention to delay or prevent autoimmunity. We provide a suite of tools at https://apps.allenimmunology.org/aifi/insights/ra-progression/ to facilitate exploration and enhance accessibility of this extensive dataset.

TCR-CD3 signal strength regulates plastic coexpression of IL-4 and IFN-γ in Tfh-like cells

The development of T follicular helper (Tfh) cells is an ongoing process resulting in the formation of various Tfh subsets. Despite advancements, the precise impact of T cell receptor (TCR) stimulation on this process remains incompletely understood. This study explores how TCR-CD3 signaling strength influences naive CD4+ T cell differentiation into Tfh-like cells and the concurrent expression of interleukin-21 (IL-21), interleukin-4 (IL-4), and interferon-gamma (IFN-γ). Strong TCR-CD3 stimulation induces proliferation and increased IL-21 expression in Tfh-like cells, which exhibit a characteristic phenotype expressing CXCR5 and PD1. The coexpression of IL-4 and IFN-γ in IL-21-producing Tfh-like cells is controlled by the strength TCR-CD3 stimulation; low stimulation favors IL-4, while strong stimulation enhances IFN-γ secretion. Exogenous addition of the effector cytokines IL-21 and IL-4 further modulate cytokine coexpression. These findings highlight the intricate regulatory mechanisms governing cytokine production and plasticity in Tfh-like cells, providing insights into B cell response modulation. In vivo, antigen availability may regulate Tfh cell plasticity, impacting subsequent B cell differentiation, emphasizing the need for further exploration through animal models or antigen-specific Tfh cell analyses in human lymph node biopsies.

B Cell Lymphoma 6 (BCL6): A Conserved Regulator of Immunity and Beyond

B cell lymphoma 6 (BCL6) is a conserved multi-domain protein that functions principally as a transcriptional repressor. This protein regulates many pivotal aspects of immune cell development and function. BCL6 is critical for germinal center (GC) formation and the development of high-affinity antibodies, with key roles in the generation and function of GC B cells, follicular helper T (Tfh) cells, follicular regulatory T (Tfr) cells, and various immune memory cells. BCL6 also controls macrophage production and function as well as performing a myriad of additional roles outside of the immune system. Many of these regulatory functions are conserved throughout evolution. The BCL6 gene is also important in human oncology, particularly in diffuse large B cell lymphoma (DLBCL) and follicular lymphoma (FL), but also extending to many in other cancers, including a unique role in resistance to a variety of therapies, which collectively make BCL6 inhibitors highly sought-after.

T peripheral helper (Tph) cells, a marker of immune activation in cancer and autoimmune disorders

T peripheral helper (Tph) cells are a newly discovered subtype of CD4+ T cells that have emerged as the counterpart of T follicular helper (Tfh) cells in the peripheral tissues. These two cell types share some common characteristics, such as high levels of PD1 and CXCL13 expression, but differ in the expression of transcription factors and chemokine receptors. Tph cells have been studied in relation to B cells' effector functions, including cytokines production and antibody-mediated immune responses. However, their role in the inflammatory-mediated development of malignancies remains poorly understood. Tph cells were initially identified in the synovium of rheumatoid arthritis patients and have since been found to be expanded in several autoimmune diseases. They have been linked to a worse prognosis in autoimmune conditions, but intriguingly, their presence has been correlated with better outcomes in certain types of cancer. The functions of Tph cells are still being investigated, but recent data suggests their involvement in the assembly of tertiary lymphoid structures (TLS). Furthermore, their interaction with B cells, which have been mainly described as possessing a memory phenotype, promotes their development. In this review, we explore the role of Tph cells in peripheral immune responses during cancer and autoimmune disorders.

Tertiary lymphoid structures in diseases: immune mechanisms and therapeutic advances

Tertiary lymphoid structures (TLSs) are defined as lymphoid aggregates formed in non-hematopoietic organs under pathological conditions. Similar to secondary lymphoid organs (SLOs), the formation of TLSs relies on the interaction between lymphoid tissue inducer (LTi) cells and lymphoid tissue organizer (LTo) cells, involving multiple cytokines. Heterogeneity is a distinguishing feature of TLSs, which may lead to differences in their functions. Growing evidence suggests that TLSs are associated with various diseases, such as cancers, autoimmune diseases, transplant rejection, chronic inflammation, infection, and even ageing. However, the detailed mechanisms behind these clinical associations are not yet fully understood. The mechanisms by which TLS maturation and localization affect immune function are also unclear. Therefore, it is necessary to enhance the understanding of TLS development and function at the cellular and molecular level, which may allow us to utilize them to improve the immune microenvironment. In this review, we delve into the composition, formation mechanism, associations with diseases, and potential therapeutic applications of TLSs. Furthermore, we discuss the therapeutic implications of TLSs, such as their role as markers of therapeutic response and prognosis. Finally, we summarize various methods for detecting and targeting TLSs. Overall, we provide a comprehensive understanding of TLSs and aim to develop more effective therapeutic strategies.

Identification of Lupus-Associated Genes in the Pathogenesis of Pre-eclampsia Via Bioinformatic Analysis

Pre-eclampsia (PE) is a severe pregnancy complication that is more common in patients with systemic lupus erythematosus (SLE). Although the exact causes of these conditions are not fully understood, the immune system plays a key role. To investigate the connection between SLE and PE, we analyzed genes associated with SLE that may contribute to the development of PE. We collected 9 microarray data sets from the NCBI GEO database and used Limma to identify the differentially expressed genes (DEGs). In addition, we employed weighted gene co-expression network analysis (WGCNA) to pinpoint the hub genes of SLE and examined immune infiltration using Cibersort. By constructing a protein-protein interaction (PPI) network and using CytoHubba, we identified the top 20 PE hub genes. Subsequently, we created a nomogram and conducted a receiver operating characteristic (ROC) analysis to predict the risk of PE. Our analysis, including gene set enrichment analysis (GSEA) and PE DEGs enrichment analysis, revealed significant involvement in placenta development and immune response. Two pivotal genes, BCL6 and MME, were identified, and their validity was confirmed using 5 data sets. The nomogram demonstrated good diagnostic performance (AUC: 0.82-0.96). Furthermore, we found elevated expression levels of both genes in SLE peripheral blood mononuclear cells (PBMCs) and PE placental specimens within the case group. Analysis of immune infiltration in the SLE data set showed a strong positive correlation between the expression of both genes and neutrophil infiltration. BCL6 and MME emerged as crucial genes in lupus-related pregnancies associated with the development of PE, for which we devised a nomogram. These findings provide potential candidate genes for further research in the diagnosis and understanding of the pathophysiology of PE.

Neutralization activity in chronic HIV infection is characterized by a distinct programming of follicular helper CD4 T cells

A subset of people living with HIV (PLWH) can produce broadly neutralizing antibodies (bNAbs) against HIV, but the lymph node (LN) dynamics that promote the generation of these antibodies are poorly understood. Here, we explored LN-associated histological, immunological, and virological mechanisms of bNAb generation in a cohort of anti-retroviral therapy (ART)-naïve PLWH. We found that participants who produce bNAbs, termed neutralizers, have a superior LN-associated B cell follicle architecture compared with PLWH who do not. The latter was associated with a significantly higher in situ prevalence of Bcl-6hi follicular helper CD4 T cells (TFH), expressing a molecular program that favors their differentiation and stemness, and significantly reduced IL-10 follicular suppressor CD4 T cells. Furthermore, our data reveal possible molecular targets mediating TFH- B cell interactions in neutralizers. Together, we identify cellular and molecular mechanisms that contribute to the development of bNAbs in PLWH.

CD6 Regulates CD4 T Follicular Helper Cell Differentiation and Humoral Immunity During Murine Coronavirus Infection

During activation the T cell transmembrane receptor CD6 becomes incorporated into the T cell immunological synapse where it can exert both co-stimulatory and co-inhibitory functions. Given the ability of CD6 to carry out opposing functions, this study sought to determine how CD6 regulates early T cell activation in response to viral infection. Infection of CD6 deficient mice with a neurotropic murine coronavirus resulted in greater activation and expansion of CD4 T cells in the draining lymph nodes. Further analysis demonstrated that there was also preferential differentiation of CD4 T cells into T follicular helper cells, resulting in accelerated germinal center responses and emergence of high affinity virus specific antibodies. Given that CD6 conversely supports CD4 T cell activation in many autoimmune models, we probed potential mechanisms of CD6 mediated suppression of CD4 T cell activation during viral infection. Analysis of CD6 binding proteins revealed that infection induced upregulation of Ubash3a, a negative regulator of T cell receptor signaling, was hindered in CD6 deficient lymph nodes. Consistent with greater T cell activation and reduced UBASH3a activity, the T cell receptor signal strength was intensified in CD6 deficient CD4 T cells. These results reveal a novel immunoregulatory role for CD6 in limiting CD4 T cell activation and deterring CD4 T follicular helper cell differentiation, thereby attenuating antiviral humoral immunity.

[Progress of IL-21 and Tfh Mediated Immunotherapy in Non-small Cell Lung Cancer]

Non-small cell lung cancer (NSCLC) is a prevalent and aggressive global malignancy. Conventional surgical treatments, radiotherapy, chemotherapy, and targeted therapies often fall short in halting disease progression due to inherent limitations, resulting in suboptimal prognosis. Despite the advent of immunotherapy drugs offering new hope for NSCLC treatment, current efficacy remains insufficient to meet all patient needs. Therefore, actively exploring novel immunotherapeutic approaches to further reduce mortality rates in NSCLC patients has become a crucial focus of NSCLC research. This article aims to systematically review the anti-tumor effects of interleukin-21 and follicular helper T cells in NSCLC immunotherapy by summarizing and analyzing relevant literatures from both domestic and international sources, as well as exploring the potential for enhancing NSCLC treatment prospects through immune checkpoint regulation via immunotherapeutic means.
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Oligoclonal CD4+CXCR5+ T cells with a cytotoxic phenotype appear in tonsils and blood

In clinical situations, peripheral blood accessible CD3+CD4+CXCR5+ T-follicular helper (TFH) cells may have to serve as a surrogate indicator for dysregulated germinal center responses in tissues. To determine the heterogeneity of TFH cells in peripheral blood versus tonsils, CD3+CD4+CD45RA-CXCR5+ cells of both origins were sorted. Transcriptomes, TCR repertoires and cell-surface protein expression were analysed by single-cell RNA sequencing, flow cytometry and immunohistochemistry. Reassuringly, all blood-circulating CD3+CD4+CXCR5+ T-cell subpopulations also appear in tonsils, there with some supplementary TFH characteristics, while peripheral blood-derived TFH cells display markers of proliferation and migration. Three further subsets of TFH cells, however, with bona fide T-follicular gene expression patterns, are exclusively found in tonsils. One additional, distinct and oligoclonal CD4+CXCR5+ subpopulation presents pronounced cytotoxic properties. Those 'killer TFH (TFK) cells' can be discovered in peripheral blood as well as among tonsillar cells but are located predominantly outside of germinal centers. They appear terminally differentiated and can be distinguished from all other TFH subsets by expression of NKG7 (TIA-1), granzymes, perforin, CCL5, CCR5, EOMES, CRTAM and CX3CR1. All in all, this study provides data for detailed CD4+CXCR5+ T-cell assessment of clinically available blood samples and extrapolation possibilities to their tonsil counterparts.

CBLs downregulation foretells T cell ubiquitination leading to autoimmunity

In a study published in the July issue of Immunity, Li et al.1 demonstrate that expression of the E3 ubiquitin ligases CBL and CBL-B is downregulated in Tfh cells in SLE with Tfh cell expansion and autoimmunity. This leads to reduced ubiquitination of the T cell costimulator ICOS which regulates proteostasis of the Tfh cell transcription factor BCL6 via chaperone-mediated autophagy.

Deficiency of CBL and CBLB ubiquitin ligases leads to hyper T follicular helper cell responses and lupus by reducing BCL6 degradation

Recent evidence reveals hyper T follicular helper (Tfh) cell responses in systemic lupus erythematosus (SLE); however, molecular mechanisms responsible for hyper Tfh cell responses and whether they cause SLE are unclear. We found that SLE patients downregulated both ubiquitin ligases, casitas B-lineage lymphoma (CBL) and CBLB (CBLs), in CD4+ T cells. T cell-specific CBLs-deficient mice developed hyper Tfh cell responses and SLE, whereas blockade of Tfh cell development in the mutant mice was sufficient to prevent SLE. ICOS was upregulated in SLE Tfh cells, whose signaling increased BCL6 by attenuating BCL6 degradation via chaperone-mediated autophagy (CMA). Conversely, CBLs restrained BCL6 expression by ubiquitinating ICOS. Blockade of BCL6 degradation was sufficient to enhance Tfh cell responses. Thus, the compromised expression of CBLs is a prevalent risk trait shared by SLE patients and causative to hyper Tfh cell responses and SLE. The ICOS-CBLs axis may be a target to treat SLE.

RACK1 enhances STAT3 stability and promotes T follicular helper cell development and function during blood-stage Plasmodium infection in mice

CD4+ T cells are central mediators of protective immunity to blood-stage malaria, particularly for their capacity in orchestrating germinal center reaction and generating parasite-specific high-affinity antibodies. T follicular helper (Tfh) cells are predominant CD4+ effector T cell subset implicated in these processes, yet the factors and detailed mechanisms that assist Tfh cell development and function during Plasmodium infection are largely undefined. Here we provide evidence that receptor for activated C kinase 1 (RACK1), an adaptor protein of various intracellular signals, is not only important for CD4+ T cell expansion as previously implied but also plays a prominent role in Tfh cell differentiation and function during blood-stage Plasmodium yoelii 17XNL infection. Consequently, RACK1 in CD4+ T cells contributes significantly to germinal center formation, parasite-specific IgG production, and host resistance to the infection. Mechanistic exploration detects specific interaction of RACK1 with STAT3 in P. yoelii 17XNL-responsive CD4+ T cells, ablation of RACK1 leads to defective STAT3 phosphorylation, accompanied by substantially lower amount of STAT3 protein in CD4+ T cells, whereas retroviral overexpression of RACK1 or STAT3 in RACK1-deficient CD4+ T cells greatly restores STAT3 activity and Bcl-6 expression under the Tfh polarization condition. Further analyses suggest RACK1 positively regulates STAT3 stability by inhibiting the ubiquitin-proteasomal degradation process, thus promoting optimal STAT3 activity and Bcl-6 induction during Tfh cell differentiation. These findings uncover a novel mechanism by which RACK1 participates in posttranslational regulation of STAT3, Tfh cell differentiation, and subsequent development of anti-Plasmodium humoral immunity.

Development of a PCSK9-targeted nanoparticle vaccine to effectively decrease the hypercholesterolemia

Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to the low-density lipoprotein receptor (LDLR) and mediates its internalization and degradation, resulting in an increase in LDL cholesterol levels. Recently, PCSK9 emerged as a therapeutic target for hypercholesterolemia and atherosclerosis. In this study, we develop a PCSK9 nanoparticle (NP) vaccine by covalently conjugating the catalytic domain (aa 153-aa 454, D374Y) of PCSK9 to self-assembled 24-mer ferritin NPs. We demonstrate that the PCSK9 NP vaccine effectively induces interfering antibodies against PCSK9 and reduces serum lipids levels in both a high-fat diet-induced hypercholesterolemia model and an adeno-associated virus-hPCSK9D374Y-induced hypercholesterolemia model. Additionally, the vaccine significantly reduces plaque lesion areas in the aorta and macrophages infiltration in an atherosclerosis mouse model. Furthermore, we discover that the vaccine's efficacy relied on T follicular help cells and LDLR. Overall, these findings suggest that the PCSK9 NP vaccine holds promise as an effective treatment for hypercholesterolemia and atherosclerosis.

ETV5 promotes lupus pathogenesis and follicular helper T cell differentiation by inducing osteopontin expression

Follicular helper T (TFH) cells mediate germinal center reactions to generate high affinity antibodies against specific pathogens, and their excessive production is associated with the pathogenesis of systemic autoimmune diseases such as systemic lupus erythematosus (SLE). ETV5, a member of the ETS transcription factor family, promotes TFH cell differentiation in mice. In this study, we examined the role of ETV5 in the pathogenesis of lupus in mice and humans. T cell-specific deletion of Etv5 alleles ameliorated TFH cell differentiation and autoimmune phenotypes in lupus mouse models. Further, we identified SPP1 as an ETV5 target that promotes TFH cell differentiation in both mice and humans. Notably, extracellular osteopontin (OPN) encoded by SPP1 enhances TFH cell differentiation by activating the CD44-AKT signaling pathway. Furthermore, ETV5 and SPP1 levels were increased in CD4+ T cells from patients with SLE and were positively correlated with disease activity. Taken together, our findings demonstrate that ETV5 is a lupus-promoting transcription factor, and secreted OPN promotes TFH cell differentiation.

Clinicopathological role of Cyclin A2 in uterine corpus endometrial carcinoma: Integration of tissue microarrays and ScRNA-Seq

BACKGROUND

The comprehensive expression level and potential molecular role of Cyclin A2 (CCNA2) in uterine corpus endometrial carcinoma (UCEC) remains undiscovered.

METHODS

UCEC and normal endometrium tissues from in-house and public databases were collected for investigating protein and messenger RNA expression of CCNA2. The transcription factors of CCNA2 were identified by the Cistrome database. The prognostic significance of CCNA2 in UCEC was evaluated through univariate and multivariate Cox regression as well as Kaplan-Meier curve analysis. Single-cell RNA-sequencing (scRNA-seq) analysis was performed to explore cell types in UCEC, and the AUCell algorithm was used to investigate the activity of CCNA2 in different cell types.

RESULTS

A total of 32 in-house UCEC and 30 normal endometrial tissues as well as 720 UCEC and 165 control samples from public databases were eligible and collected. Integrated calculation showed that the CCNA2 expression was up-regulated in the UCEC tissues (SMD = 2.43, 95% confidence interval 2.23∼2.64). E2F1 and FOXM1 were identified as transcription factors due to the presence of binding peaks on transcription site of CCNA2. CCNA2 predicted worse prognosis in UCEC. However, CCNA2 was not an independent prognostic factor in UCEC. The scRNA-seq analysis disclosed five cell types: B cells, T cells, monocytes, natural killer cells, and epithelial cells in UCEC. The expression of CCNA2 was mainly located in B cells and T cells. Moreover, CCNA2 was active in T cells and B cells using the AUCell algorithm.

CONCLUSION

CCNA2 was up-regulated and mainly located in T cells and B cells in UCEC. Overexpression of CCNA2 predicted unfavorable prognosis of UCEC.

Transcriptional regulation of Tfh dynamics and the formation of immunological synapses

Inside germinal centers (GCs), antigen-specific B cells rely on precise interactions with immune cells and strategic localization between the dark and light zones to clonally expand, undergo affinity maturation, and differentiate into long-lived plasma cells or memory B cells. Follicular helper T (Tfh) cells, the key gatekeepers of GC-dependent humoral immunity, exhibit remarkable dynamic positioning within secondary lymphoid tissues and rely on intercellular interactions with antigen-presenting cells (APCs) during their differentiation and execution of B-cell-facilitating functions within GCs. In this review, we briefly cover the transcriptional regulation of Tfh cell differentiation and function and explore the molecular mechanisms governing Tfh cell motility, their interactions with B cells within GCs, and the impact of their dynamic behavior on humoral responses.

DEAD-box helicase 17 (DDX17) protects cardiac function by promoting mitochondrial homeostasis in heart failure

DEAD-box helicase 17 (DDX17) is a typical member of the DEAD-box family with transcriptional cofactor activity. Although DDX17 is abundantly expressed in the myocardium, its role in heart is not fully understood. We generated cardiomyocyte-specific Ddx17-knockout mice (Ddx17-cKO), cardiomyocyte-specific Ddx17 transgenic mice (Ddx17-Tg), and various models of cardiomyocyte injury and heart failure (HF). DDX17 is downregulated in the myocardium of mouse models of heart failure and cardiomyocyte injury. Cardiomyocyte-specific knockout of Ddx17 promotes autophagic flux blockage and cardiomyocyte apoptosis, leading to progressive cardiac dysfunction, maladaptive remodeling and progression to heart failure. Restoration of DDX17 expression in cardiomyocytes protects cardiac function under pathological conditions. Further studies showed that DDX17 can bind to the transcriptional repressor B-cell lymphoma 6 (BCL6) and inhibit the expression of dynamin-related protein 1 (DRP1). When DDX17 expression is reduced, transcriptional repression of BCL6 is attenuated, leading to increased DRP1 expression and mitochondrial fission, which in turn leads to impaired mitochondrial homeostasis and heart failure. We also investigated the correlation of DDX17 expression with cardiac function and DRP1 expression in myocardial biopsy samples from patients with heart failure. These findings suggest that DDX17 protects cardiac function by promoting mitochondrial homeostasis through the BCL6-DRP1 pathway in heart failure.

Heterogeneity and plasticity of tissue-resident memory T cells in skin diseases and homeostasis: a review

Skin tissue-resident memory T (Trm) cells are produced by antigenic stimulation and remain in the skin for a long time without entering the peripheral circulation. In the healthy state Trm cells can play a patrolling and surveillance role, but in the disease state Trm cells differentiate into various phenotypes associated with different diseases, exhibit different localizations, and consequently have local protective or pathogenic roles, such as disease recurrence in vitiligo and maintenance of immune homeostasis in melanoma. The most common surface marker of Trm cells is CD69/CD103. However, the plasticity of tissue-resident memory T cells after colonization remains somewhat uncertain. This ambiguity is largely due to the variation in the functionality and ultimate destination of Trm cells produced from memory cells differentiated from diverse precursors. Notably, the presence of Trm cells is not stationary across numerous non-lymphoid tissues, most notably in the skin. These cells may reenter the blood and distant tissue sites during the recall response, revealing the recycling and migration potential of the Trm cell progeny. This review focuses on the origin and function of skin Trm cells, and provides new insights into the role of skin Trm cells in the treatment of autoimmune skin diseases, infectious skin diseases, and tumors.

Modulation of PKM2 inhibits follicular helper T cell differentiation and ameliorates inflammation in lupus-prone mice

OBJECTIVES

Expansion of follicular helper T (Tfh) cells and abnormal glucose metabolism are present in patients with systemic lupus erythematosus (SLE). Pyruvate kinase M2 (PKM2) is one of the key glycolytic enzymes, and the underlying mechanism of PKM2-mediated Tfh cell glycolysis in SLE pathogenesis remains elusive.

METHODS

We analyzed the percentage of Tfh cells and glycolysis in CD4+ T cells from SLE patients and healthy donors and performed RNA sequencing analysis of peripheral blood CD4+ T cells and differentiated Tfh cells from SLE patients. Following Tfh cell development in vitro and following treatment with PKM2 activator TEPP-46, PKM2 expression, glycolysis, and signaling pathway proteins were analyzed. Finally, diseased MRL/lpr mice were treated with TEPP-46 and assessed for treatment effects.

RESULTS

We found that Tfh cell percentage and glycolysis levels were increased in SLE patients and MRL/lpr mice. TEPP-46 induced PKM2 tetramerization, thereby inhibiting Tfh cell glycolysis levels. On the one hand, TEPP-46 reduced the dimeric PKM2 entering the nucleus and reduced binding to the transcription factor BCL6. On the other hand, TEPP-46 inhibited the AKT/GSK-3β pathway and glycolysis during Tfh cell differentiation. Finally, we confirmed that TEPP-46 effectively alleviated inflammatory damage in lupus-prone mice and reduced the expansion of Tfh cells in vivo.

CONCLUSIONS

Our results demonstrate the involvement of PKM2-mediated glycolysis in Tfh cell differentiation and SLE pathogenesis, and PKM2 could be a key therapeutic target for the treatment of SLE.

Genomic deletion of Bcl6 differentially affects conventional dendritic cell subsets and compromises Tfh/Tfr/Th17 cell responses

Conventional dendritic cells (cDC) play key roles in immune induction, but what drives their heterogeneity and functional specialization is still ill-defined. Here we show that cDC-specific deletion of the transcriptional repressor Bcl6 in mice alters the phenotype and transcriptome of cDC1 and cDC2, while their lineage identity is preserved. Bcl6-deficient cDC1 are diminished in the periphery but maintain their ability to cross-present antigen to CD8+ T cells, confirming general maintenance of this subset. Surprisingly, the absence of Bcl6 in cDC causes a complete loss of Notch2-dependent cDC2 in the spleen and intestinal lamina propria. DC-targeted Bcl6-deficient mice induced fewer T follicular helper cells despite a profound impact on T follicular regulatory cells in response to immunization and mounted diminished Th17 immunity to Citrobacter rodentium in the colon. Our findings establish Bcl6 as an essential transcription factor for subsets of cDC and add to our understanding of the transcriptional landscape underlying cDC heterogeneity.

PD-L1- and IL-4-expressing basophils promote pathogenic accumulation of T follicular helper cells in lupus

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by anti-nuclear autoantibodies whose production is promoted by autoreactive T follicular helper (TFH) cells. During SLE pathogenesis, basophils accumulate in secondary lymphoid organs (SLO), amplify autoantibody production and disease progression through mechanisms that remain to be defined. Here, we provide evidence for a direct functional relationship between TFH cells and basophils during lupus pathogenesis, both in humans and mice. PD-L1 upregulation on basophils and IL-4 production are associated with TFH and TFH2 cell expansions and with disease activity. Pathogenic TFH cell accumulation, maintenance, and function in SLO were dependent on PD-L1 and IL-4 in basophils, which induced a transcriptional program allowing TFH2 cell differentiation and function. Our study establishes a direct mechanistic link between basophils and TFH cells in SLE that promotes autoantibody production and lupus nephritis.

Contrasting roles for IgM and B-cell MHCII expression in Brucella abortus S19 vaccine-mediated efficacy against B. melitensis infection

Brucellosis, caused by the bacterium Brucella, poses a significant global threat to both animal and human health. Although commercial live Brucella vaccines including S19, RB51, and Rev1 are available for animals, their unsuitability for human use and incomplete efficacy in animals necessitate the further study of vaccine-mediated immunity to Brucella. In this study, we employed in vivo B-cell depletion, as well as immunodeficient and transgenic mouse models, to comprehensively investigate the roles of B cells, antigen uptake and presentation, antibody production, and class switching in the context of S19-mediated immunity against brucellosis. We found that antibody production, and in particular secretory IgM plays a protective role in S19-mediated immunity against virulent Brucella melitensis early after the challenge in a manner associated with complement activation. While T follicular helper cell deficiency dampened IgG production and vaccine efficacy at later stages of the challenge, this effect appeared to be independent of antibody production and rather was associated with altered T-cell function. By contrast, B-cell MHCII expression negatively impacted vaccine efficacy at later timepoints after the challenge. In addition, B-cell depletion after vaccination, but before the challenge, enhanced S19-mediated protection against brucellosis, suggesting a deleterious role of B cells during the challenge phase. Collectively, our findings indicate antibody production is protective, while B-cell MHCII expression is deleterious, to live vaccine-mediated immunity against brucellosis.

IMPORTANCE

Brucella is a neglected zoonotic pathogen with a worldwide distribution. Our study delves into B-cell effector functions in live vaccine-mediated immunity against brucellosis. Notably, we found antibody production, particularly secretory IgM, confers protection against virulent Brucella melitensis in vaccinated mice, which was associated with complement activation. By contrast, B-cell MHCII expression negatively impacted vaccine efficacy. In addition, B-cell depletion after vaccination, but before the B. melitensis challenge, enhanced protection against infection, suggesting a detrimental B-cell role during the challenge phase. Interestingly, deficiency of T follicular helper cells, which are crucial for aiding germinal center B cells, dampened vaccine efficacy at later stages of challenge independent of antibody production. This study underscores contrasting and phase-dependent roles of B-cell effector functions in vaccine-mediated immunity against Brucella.