Bcl6 mediates the development of T follicular helper cells

Protection acquired upon intraperitoneal group a Streptococcus immunization is independent of concurrent adaptive immune responses but relies on macrophages and IFN-γ

Group A Streptococcus (GAS; Streptococcus pyogenes) is an important bacterial pathogen causing over 700 million superficial infections and around 500.000 deaths due to invasive disease or severe post-infection sequelae yearly. In spite of this major impact on society, there is currently no vaccine available against this bacterium. GAS strains can be separated into >250 distinct emm (M)-types, and protective immunity against GAS is believed to in part be dependent on type-specific antibodies. Here, we analyse the nature of protective immunity generated against GAS in a model of intraperitoneal immunization in mice. We demonstrate that multiple immunizations are required for the ability to survive a subsequent lethal challenge, and although significant levels of GAS-specific antibodies are produced, these are redundant for protection. Instead, our data show that the immunization-dependent protection in this model is induced in the absence of B and T cells and is accompanied by the induction of an altered acute cytokine profile upon subsequent infection, noticeable e.g. by the absence of classical pro-inflammatory cytokines and increased IFN-γ production. Further, the ability of immunized mice to survive a lethal infection is dependent on macrophages and the macrophage-activating cytokine IFN-γ. To our knowledge these findings are the first to suggest that GAS may have the ability to induce forms of trained innate immunity. Taken together, the current study proposes a novel role for the innate immune system in response to GAS infections that potentially could be leveraged for future development of effective vaccines.

An overview of host immune responses against Leishmania spp. infections

Leishmania spp. infections pose a significant global health challenge, affecting approximately 1 billion people across more than 88 endemic countries. This unicellular, obligate intracellular parasite causes a spectrum of diseases, ranging from localized cutaneous lesions to systemic visceral infections. Despite advancements in modern medicine and increased understanding of the parasite's etiology and associated diseases, treatment options remain limited to pentavalent antimonials, liposomal amphotericin B, and miltefosine. A deeper understanding of the interactions between immune and non-immune cells involved in the clearance of Leishmania spp. infections could uncover novel therapeutic strategies for this debilitating disease. This review highlights recent progress in elucidating how various cell types contribute to the regulation and resolution of Leishmania spp. infections.

Immunological characteristics of the recombinant pseudorabies virus with chimeric PCV Cap protein in pigs

Porcine circovirus type 2 (PCV2) is one of the main pathogens causing porcine circovirus-associated diseases (PCVAD). We recently reported the immunogenicity of the recombinant PRV with an envelope-embedded Cap protein of PCV2 (PRV-Cap) in mice. Here, we further evaluated the immunoprotective efficacy of PRV-Cap virus in pigs. Following vaccination, the PRV-Cap stimulated the production of neutralizing antibodies against PRV and PCV2, along with protected piglets from the challenge of the lethal PRV, the virulent PCV2b and PCV2d. Peripheral blood mononuclear cells analysis revealed that PRV-Cap virus effectively induced proliferation and activation of CD4 and CD8 T cells, as well as an increase in T follicular helper cells, although γδ T and B cells did not show significant differences. Compared to DMEM control piglets, the expanded CD4 and CD8 T cells exhibited an effector memory T cell phenotype, and in vitro stimulation led to PRV- and PCV2-specific IFN-γ and TNF-α secretion, peaking at 21 days post-immunization. In summary, PRV-Cap virus effectively prevents PRV, PCV2b and PCV2d challenges in piglets by simultaneously inducing both PRV- and PCV2-specific humoral and cellular immunity, indicating that PRV-Cap virus is a promising and safe candidate vaccine for combined PRV and PCV2 immunization.

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.

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.

The cellular factors that impair the germinal center in advanced age

Long-lasting immunological memory is a core feature of the adaptive immune system that allows an organism to have a potent recall response to foreign agents that have been previously encountered. Persistent humoral immunity is afforded by long-lived memory B cells and plasma cells, which can mature in germinal centers (GCs) in secondary lymphoid organs. The development of new GC-derived immunity diminishes with age, thereby impairing our immune system's response to both natural infections and vaccinations. This review will describe the current knowledge of how aging affects the cells and microenvironment of the GC. A greater understanding of how the GC changes with age, and how to circumvent these changes, will be critical for tailoring vaccines for older people. This area of research is critical given the twenty-first century will witness a doubling of the aging population and an increased frequency of pandemics.

Resveratrol as a BCL6 natural inhibitor suppresses germinal center derived Non-Hodgkin lymphoma cells growth

Non-Hodgkin lymphomas (NHL), including diffuse large B-cell lymphoma (DLBCL), Burkitt lymphoma (BL), and follicular lymphoma (FL), predominantly arise from B cells undergoing germinal center (GC) reactions. The transcriptional repressor B-cell lymphoma 6 (BCL6) is indispensable for GC formation and contributes to lymphomagenesis via its BTB domain-mediated suppression of target genes. Dysregulation of BCL6 underpins the pathogenesis of GC-derived NHL. While pharmacological targeting the BCL6-BTB domain has shown therapeutic promise, natural product-based inhibitors remain underexplored. In this study, resveratrol, a polyphenolic compound derived from grapes, was identified as a potent BCL6 inhibitor through a comprehensive screen of traditional Chinese medicine monomers using Homogeneous Time-Resolved Fluorescence (HTRF) assay. As a BCL6 natural inhibitor, resveratrol effectively disrupted the BCL6/SMRT interaction, reactivated suppressed gene expression, and inhibited the proliferation of GC-derived NHL cells. It also exhibited synergistic efficacy when combined with EZH2 and PRMT5 inhibitors. In vivo, resveratrol suppressed GC formation, reduced follicular helper T-cell frequencies, impaired class-switch recombination, and disrupted immunoglobulin affinity maturation. Furthermore, it markedly inhibited the progression of GC-derived NHL in animal models. Our findings demonstrate that resveratrol functions as a natural BCL6 inhibitor with significant therapeutic potential for the treatment of GC-derived NHL.

Small molecule BCL6-inhibition suppresses follicular T helper cell differentiation and plasma blast formation

B cell responses are dependent on specialized help provided by follicular T helper (Tfh). Tfh and B cells both express the transcription factor B-cell lymphoma 6 protein (BCL6) and targeting BCL6 may thus prevent humoral allo-immune responses after transplantation. In this study, the effects of the small molecule BCL6 inhibitor 79-6 on human T and B cell differentiation and proliferation were investigated. To this end, naïve CD4 helper T cells and resting B cells were stimulated polyclonally in the presence of 79-6. This compound suppressed proliferation, differentiation, and function of Tfh cells, and also the proliferation and differentiation of B cells. Plasma blast formation was affected, resulting in inhibition of antibody production by > 70 % at the highest concentration of 79-6 used. A time-dependent impact of 79-6 on B cell functions was also demonstrated during allo-antigen stimulation. In contrast to the condition of adding 79-6 at day 0, addition on day 3 or 7 hardly inhibited plasma blast formation. In conclusion, targeting BCL6 with 79-6 inhibits T and B cells' differentiation towards Tfh cells and plasma blasts and subsequent antibody production. Small molecule 79-6 is a promising compound which might prevent interaction between Tfh and B cells.

Tissue-Resident Th2 Cells in Type 2 Immunity and Allergic Diseases

Type 2 immunity represents a unique immune module that provides host protection against macro-parasites and noxious agents such as venoms and toxins. In contrast, maladaptive type 2 immune responses cause allergic diseases. While multiple cell types play important roles in type 2 immunity, recent studies in humans and murine models of chronic allergic diseases have shown that a distinct population of tissue-resident, CD4+ T helper type 2 (Th2) cells play a critical role in chronic allergic inflammation. The rules regulating Th2 cell differentiation have remained less well defined than other T cell subsets, but recent studies have shed new light into the specific mechanisms controlling Th2 cell biology in vivo. Here, we review our current understanding of the checkpoints regulating the development and function of tissue-resident Th2 cells with a focus on chronic allergic diseases. We discuss evidence for a barrier tissue checkpoint in initial Th2 cell priming, including the role of neuropeptides, damage-associated molecular patterns, and dendritic cell macro-clusters. Furthermore, we review the evidence for a second barrier tissue checkpoint that instructs the development of multi-cytokine producing, tissue-resident Th2 cells that orchestrate allergic inflammation. Lastly, we discuss potential approaches to therapeutically target tissue-resident Th2 cells in chronic allergic diseases.

The function of T cells in immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune disease, characterized by increased bleeding due to a reduced platelet count. The pathogenesis of ITP is very complex and involves autoantibody production and T-cell-mediated immune abnormalities. An imbalance of effector and regulatory CD4+ T cells and the breach of tolerance primarily cause ITP, leading to the dysfunctional development of autoreactive Th cells (including Th1, Th2, and Th17 cells) and Tregs. The loss of auto-platelet antigen tolerance in ITP results in autoantibody- and cytotoxic T-cell-mediated platelet clearance. T-cell-related genetic risk factors significantly influence the development and progression of this disease. New therapies targeting T cells have emerged as potentially effective cures for this disease. This review summarizes the role of T cells in ITP.

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.

Global research prospects and trends in TFH cells and tumors: a bibliometric analysis

Background

T follicular helper (TFH) cells, a subset of CD4+Th cells, play a critical role in B cell activation, proliferation, and differentiation primarily within B follicles in secondary lymphoid organs, essential processes for effective antibody responses. TFH cells are also implicated in various conditions, including autoimmune diseases, cancer, infectious diseases, allergies, and vaccine reactions. Despite their broad impact, a review of the literature on TFH cells and tumors has not been conducted. We aimed to fill this gap by providing a detailed analysis of the research landscape concerning TFH cells and tumors.

Method

We conducted a bibliometric analysis of literature on TFH cells and tumors from 2012 to 2024 using the Web of Science Core Collection (WoSCC). For an analysis of the global research landscape, we employed VOSviewer (version 1.6.20), CiteSpace 6.2.R6 software, and the "bibliometric" package in R language (version 4.3.2) to evaluate data on countries/regions, authors and cited authors, institutions, journals, references, and keywords. We also conducted a systematic review to summarize the global research trends, prospects, and hotspots in this field.

Results

Our analysis included contributions from 60 countries/regions, 7,864 authors, 35,853 cited authors, 1,756 institutions, 385 academic journals, 50883 references, 222 keywords, and 1,181published papers. Over the past decade, the volume of research on TFH cells and tumors had consistently increased. China published the most papers, more than double that of the United States. The top 2 authors ranked by publication volume were Gaulard, Philippe (14 articles, 379 citations), and De leval, Laurence (12 articles, 236 citations) Notably, 9 of the top 10 most published institutions were from China. Frontiers in Immunology and Immunity were the leading journals in publications and citations. A cluster analysis revealed a shift in research focus from "expression","B cells" and "survival" to "tumor microenvironment", "tumor infiltrating immune cells" and "immune infiltration" in recent years.

Conclusion

This bibliometric analysis suggests that TFH cells hold significant research value and potential clinical applications in tumor immunotherapy. Moreover, the bibliometric analysis offers valuable references and guidance for related research endeavors. It also points out the prevailing issues and challenges in TFH cell research, and underscores the need for further basic and clinical research to advance the related fields.

TRAF3 is critical for initial T follicular helper cell specification via coordination of the IL-6R/IL-2R-BCL6 signaling nexus

CD4+ T follicular helper (TFH) cells are essential for orchestrating robust humoral immunity, yet the signals that initiate TFH cell differentiation are not fully understood. We identified that the adapter protein TRAF3 was required for TFH cell differentiation and function during systemic inflammatory infections. Loss of CD4+ T cell-intrinsic TRAF3 impaired chromatin remodeling and transcriptional programming essential for TFH cell initiation and instead augmented TH1 development and function. TRAF3-deficient CD4+ T cells exhibited altered interleukin-6 (IL-6) and IL-2 responsiveness, which were coupled to failures in BCL6 expression. Enforced expression of either IL-6 receptor or BCL6 or blockade of IL-2 signaling was sufficient to rescue TFH cell differentiation. Human CD4+ T cells lacking TRAF3 exhibited impaired TFH polarization, supporting a conserved mechanism by which TRAF3 regulates CD4+ T cell fate determination. Thus, TRAF3 functions at the nexus of cytokine, transcriptional, and epigenetic nodes that promote the TFH cell specification during infection.

T follicular helper cell profiles differ by malaria antigen and for children compared to adults

Background

Circulating T-follicular helper (cTFH) cells have the potential to provide an additional correlate of protection against Plasmodium falciparum (Pf) as they are essential to promote B-cell production of long-lasting antibodies. Assessing the specificity of cTFH subsets to individual malaria antigens is vital to understanding the variation observed in antibody responses and identifying promising malaria vaccine candidates.

Methods

Using spectral flow cytometry and unbiased clustering analysis, we assessed antigen-specific cTFH cell recall responses in vitro to malaria vaccine candidates Pf-schizont egress antigen-1 (PfSEA-1A) and Pf-glutamic acid-rich protein (PfGARP) within a cross-section of children and adults living in a malaria-holoendemic region of western Kenya.

Findings

In children, a broad array of cTFH subsets (defined by cytokine and transcription factor expression) were reactive to both malaria antigens, PfSEA-1A and PfGARP, while adults had a narrow profile centering on cTFH17- and cTFH1/17-like subsets following stimulation with PfGARP only.

Interpretation

Because TFH17 cells are involved in the maintenance of memory antibody responses within the context of parasitic infections, our results suggest that PfGARP might generate longer-lived antibody responses compared to PfSEA-1A. These findings have intriguing implications for evaluating malaria vaccine candidates as they highlight the importance of including cTFH profiles when assessing interdependent correlates of protective immunity.

Immune Alterations and Viral Reservoir Atlas in SIV-Infected Chinese Rhesus Macaques

BACKGROUND/OBJECTIVES

Over the last decades, our projects have been dedicated to clarifying immunopathological and virological events associated with Human Immunodeficiency Virus (HIV) infection.

METHODS

By using non-human primate models of pathogenic and non-pathogenic lentiviral infections, we aimed at identifying the cells and tissues in which the virus persists, despite antiretroviral therapy (ART). Indeed, the eradication of viral reservoirs is a major challenge for HIV cure.

RESULTS

We present a series of results performed in rhesus macaques of Chinese origin deciphering the virological and immunological events associated with ART that can be of interest for people living with HIV.

CONCLUSIONS

This model could be of interest for understanding in whole body the clinical alteration that persist despite ART.

Skin autonomous antibody production regulates host-microbiota interactions

The microbiota colonizes each barrier site and broadly controls host physiology1. However, when uncontrolled, microbial colonists can also promote inflammation and induce systemic infection2. The unique strategies used at each barrier tissue to control the coexistence of the host with its microbiota remain largely elusive. Here we uncover that, in the skin, host-microbiota symbiosis depends on the ability of the skin to act as an autonomous lymphoid organ. Notably, an encounter with a new skin commensal promotes two parallel responses, both under the control of Langerhans cells. On one hand, skin commensals induce the formation of classical germinal centres in the lymph node associated with immunoglobulin G1 (IgG1) and IgG3 antibody responses. On the other hand, microbial colonization also leads to the development of tertiary lymphoid organs in the skin that can locally sustain IgG2b and IgG2c responses. These phenomena are supported by the ability of regulatory T cells to convert into T follicular helper cells. Skin autonomous production of antibodies is sufficient to control local microbial biomass, as well as subsequent systemic infection with the same microorganism. Collectively, these results reveal a compartmentalization of humoral responses to the microbiota allowing for control of both microbial symbiosis and potential pathogenesis.

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.

Dimethyl fumarate ameliorates chronic graft-versus-host disease by inhibiting Tfh differentiation via Nrf2

Chronic graft-versus-host disease (cGVHD), characterized by chronic tissue inflammation and fibrosis involving multiple organs, remains a major complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Dimethyl fumarate (DMF) is an anti-inflammatory drug approved for the treatment of multiple sclerosis and psoriasis. We previously reported that DMF effectively inhibits acute GVHD (aGVHD) while preserving the graft-versus-leukemia effect. However, the role of DMF in cGVHD progression remains unknown. Here, we found that DMF administration significantly suppresses follicular helper T cell (Tfh) differentiation, and germinal center formation and alleviates disease severity in different murine cGVHD models. Mechanistically, DMF treatment downregulates IL-21 transcription by activation of Nrf2, thus orchestrating Tfh-related gene programs both in mice and humans. The inhibitory role of DMF on Tfh cell differentiation was diminished in Nrf2 deficient T cells. Importantly, the therapeutic potential of DMF in clinical cGVHD has been validated in human data whereby DMF effectively reduces IL-21 production and Tfh cell generation in peripheral blood mononuclear cells from active cGVHD patients and further attenuates xenograft GVHD. Collectively, our findings reveal that DMF potently inhibits cGVHD development by repressing Tfh cell differentiation via Nrf2, paving the way for the treatment of cGVHD in the clinic.

Clonal relationships between Tph and Tfh cells in patients with SLE and in murine lupus

Pathologic T cell-B cell interactions drive disease in systemic lupus erythematosus (SLE). The T cells that activate B cell responses include T peripheral helper (Tph) and T follicular helper (Tfh) cells, yet the developmental and clonal relationships between these B cell-helper T cell populations are unclear. Here we use T cell receptor (TCR) profiling to demonstrate clonal overlap between Tph and Tfh cells in the circulation of patients with SLE. Expanded Tph and Tfh cell clones persist over the course of 1 year in patients with a new diagnosis of SLE, and clones are observed to shift both from Tfh to Tph cells and from Tph to Tfh cells over time. High resolution analysis of cells sorted as Tph cells (CXCR5- PD-1hi) and Tfh cells (CXCR5+ PD-1hi) from SLE patients revealed considerable heterogeneity among cells sorted as Tph cells and highlighted a specific cluster of cells that expressed transcriptomic features of activated B cell-helper T cells. This cell population, marked by expression of TOX and CXCL13, was found in both sorted Tph and Tfh cells, and was clonally linked in these two populations. Analysis of B cell-helper T cells in murine pristane-induced lupus demonstrated similar populations of Tph and Tfh cells in both lung and spleen with strong clonal overlap. T cell-specific loss of Bcl6 prevented accumulation of Tfh cells and reduced accumulation of Tph cells in pristane-treated mice, indicating a role for Bcl6 in the survival and expansion of both populations. Together, these observations demonstrate a shared developmental path among pathologically expanded Tph and Tfh cells in lupus. The persistence of expanded Tph and Tfh cells clones over time may impose barriers to induction of stable tolerance by immunosuppressive medications or by B cell depletion.

Mucosal immune response in biology, disease prevention and treatment

The mucosal immune system, as the most extensive peripheral immune network, serves as the frontline defense against a myriad of microbial and dietary antigens. It is crucial in preventing pathogen invasion and establishing immune tolerance. A comprehensive understanding of mucosal immunity is essential for developing treatments that can effectively target diseases at their entry points, thereby minimizing the overall impact on the body. Despite its importance, our knowledge of mucosal immunity remains incomplete, necessitating further research. The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has underscored the critical role of mucosal immunity in disease prevention and treatment. This systematic review focuses on the dynamic interactions between mucosa-associated lymphoid structures and related diseases. We delve into the basic structures and functions of these lymphoid tissues during disease processes and explore the intricate regulatory networks and mechanisms involved. Additionally, we summarize novel therapies and clinical research advances in the prevention of mucosal immunity-related diseases. The review also addresses the challenges in developing mucosal vaccines, which aim to induce specific immune responses while maintaining tolerance to non-pathogenic microbes. Innovative therapies, such as nanoparticle vaccines and inhalable antibodies, show promise in enhancing mucosal immunity and offer potential for improved disease prevention and treatment.

Follicular T cells and the control of IgE responses

Atopy is considered the epidemic of the 21st century, and while decades of research have established a direct link between Th2 cells driving pathogenic IgE-mediated allergic disease, only in the past years have T follicular helper (Tfh) cells emerged as pivotal drivers of these responses. In this review, we will examine the molecular mechanisms governing the IgE response, with a particular emphasis on the key cytokines and signaling pathways. We will discuss the exclusion of IgE-producing B cells from germinal centers and explore the recently established role of follicular T cell function and heterogeneity in driving or curtailing these immune responses. Additionally, we will assess the current state of major monoclonal antibodies and allergen immunotherapies designed to counteract Th2-driven inflammation, as well as reflect on the need to investigate how these biologics impact Tfh cell activity, differentiation, and function, as these insights could pave the way for much-needed therapeutic innovation in the treatment of allergic diseases.

Immunometabolic regulation of germinal centers and its implications for aging

Aging, metabolism, and immunity have long been considered distinct domains. Aging is primarily associated with the gradual decline of physiological functions, metabolism regulates energy production and maintains cellular processes, and the immune system manages innate and adaptive responses against pathogens and vaccines. However, recent studies have revealed that these three systems are intricately interconnected, collectively influencing an individual's response to stress and disease. This review explores the interplay between immunometabolism, T follicular helper cells, B cells, and aging, focusing on how these interactions impact immune function in the elderly.

Amelioration of immunoglobulin A vasculitis by suppression of the pathological expansion of T follicular helper 17 cells

The main pathogenic features of immunoglobulin A vasculitis (IgAV) are overactive B cells and elevated production of IgA, which requires help from T follicular helper 17 (Tfh17) cells. To evaluate the pathological role of Tfh17 cells in IgAV, we investigated the mechanism responsible for Tfh17 differentiation and explored how to ameliorate IgAV by modulating Tfh17 generation. Peripheral blood mononuclear cells from IgAV patients were analyzed by flow cytometry. In vitro culture was performed to assess the modulation of cytokine-induced phenotypes. IgAV rats were used to explore the therapeutic effects of IL-6 blockade and the regulatory functions of IL-6 in Tfh17 cells. Serum cytokine and IgA levels were measured by ELISA while histopathological changes were evaluated by H&E,PAS or immunofluorescence staining. Frequency of CD4+CXCR5+CCR6+ Tfh17 cells were increased in IgAV patients and associated with disease severity. There was also a significant infiltration of Tfh17 cells in the kidney of human IgAV nephritis patients. IL-6 promoted the dendritic cell production of TGF-β and Tfh17 differentiation. In IgAV rats, the in vivo blockade of IL-6 signaling inhibited Tfh17 differentiation, resulting in reduction of the germinal center and IgA production. Suppression of Tfh17 cells using IL-6 blockade greatly ameliorated clinical symptoms such as hemorrhagic rash and bloody stool and decreased IgA deposition and mesangial proliferation in the kidney in IgAV rats. Our findings suggest that suppression of Tfh17 differentiation can alleviate IgA-mediated vasculitis and may permit the development of tailored medicines for treating IgAV.

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.

Identification of immune-associated genes for the diagnosis of ulcerative colitis-associated carcinogenesis via integrated bioinformatics analysis

Background

UC patients suffer more from colorectal cancer (CRC) than the general population, which increases with disease duration. Early colonoscopy is difficult because ulcerative colitis-associated colorectal cancer (UCAC) lesions are flat and multifocal. Our study aimed to identify promising UCAC biomarkers that are complementary endoscopy strategies in the early stages.

Methods

The datasets may be accessed from the Gene Expression Omnibus and The Cancer Genome Atlas databases. The co-expressed modules of UC and CRC were determined via weighted co-expression network analysis (WGCNA). The biological mechanisms of the shared genes were exported for analysis using the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes. To identify protein interactions and hub genes, a protein-protein interaction network and CytoHubba analysis were conducted. To evaluate gene expression, external datasets and experimental validation of human colon tissues were utilized. The diagnostic value of core genes was examined through receiver operating characteristic (ROC) curves. Immune infiltration analysis was employed to investigate the associations between immune cell populations and hub genes.

Results

Three crucial modules were identified from the WGCNA of UC and CRC tissues, and 33 coexpressed genes that were predominantly enriched in the NF-κB pathway were identified. Two biomarkers (CXCL1 and BCL6) were identified via Cytoscape and validated in external datasets and human colon tissues. CRC patients expressed CXCL1 at the highest level, whereas UC and CRC patients showed higher levels than the controls. The UC cohort expressed BCL6 at the highest level, whereas the UC and CRC cohorts expressed it more highly than the controls. The hub genes exhibited significant diagnostic potential (ROC curve > 0.7). The immune infiltration results revealed a correlation among the hub genes and macrophages, neutrophils and B cells.

Conclusions

The findings of our research suggest that BCL6 and CXCL1 could serve as effective biomarkers for UCAC surveillance. Additionally, they demonstrated a robust correlation with immune cell populations within the CRC tumour microenvironment (TME). Our findings provide a valuable insight about diagnosis and therapy of UCAC.

BAFF promotes follicular helper T cell development and germinal center formation through BR3 signal

T follicular helper (Tfh) cells represent an important subset of CD4+ T cells that is crucial to the maturation and differentiation of B cells and the production of high-affinity antibodies. Because B cell activating-factor (BAFF), a vital B cell survival factor, is also crucial to B cell maturation and differentiation, we assessed the effects of BAFF on Tfh cell development and function. We demonstrated that deficiency of BAFF, but not of APRIL, markedly inhibited Tfh cell development, germinal center (GC) formation, and antigen-specific antibody production. The promoting effect of BAFF on Tfh cell development was dependent on expression of BR3 on T cells, and its promoting effect on GC formation was dependent on expression of BR3 on both T cells and B cells. BAFF directly promoted expression of the Tfh cell-characteristic genes via NF-κB signaling. This effect did need BR3 expression. Thus, BAFF not only has direct effects on B cells, but it also has direct effects on Tfh cell differentiation via engagement of BR3, which collectively promoted GC formation and production of high-affinity antibodies. This dual effect of BAFF on B cells and Tfh cells may help explain the clinical utility of BAFF antagonists in the management of certain autoimmune diseases.

Role of the Crosstalk B:Neoplastic T Follicular Helper Cells in the Pathobiology of Nodal T Follicular Helper Cell Lymphomas

Angioimmunoblastic T-cell lymphoma (AITL), the most common form of peripheral T-cell lymphoma, originates from follicular helper T (Tfh) cells and is notably resistant to current treatments. The disease progression and maintenance, at least in early stages, are driven by a complex interplay between neoplastic Tfh and clusters of B-cells within the tumor microenvironment, mirroring the functional crosstalk observed inside germinal centers. This interaction is further complicated by recurrent mutations, such as TET2 and DNMT3A, which are present in both Tfh cells and B-cells. These findings suggest that the symbiotic relationship between these 2 cell types could represent a therapeutic vulnerability. This review examines the key components and signaling mechanisms involved in the synapses between B-cells and Tfh cells, emphasizing their significant role in the pathobiology of AITL and potential as therapeutic targets.

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.

Clinical significance of T helper cell subsets in the peripheral blood and bone marrow of patients with multiple myeloma

Background

T helper (Th) cell subsets primarily assist B cells in differentiating into plasma cells in the germinal center. The mechanism of malignant transformation of plasma cells is an important target for the clinical treatment of MM; however, the mechanism remains unclear.

Methods

We collected the peripheral blood (PB) and bone marrow (BM) samples of 33 patients with MM. In addition, the PB was also collected from 25 normal healthy controls (HCs). We analyzed the percentages of Th cell subsets in the PB and BM samples of patients with MM.

Results

Tfh/CD4+ were positively correlated with the proportion of myeloma cells in the BM and PB samples (r = 0.592, P = 0.002 and r = 0.510, P = 0.010 respectively), and showed a strong correlation between the BM and PB samples (r = 0.6559, P = 0.0095). In the PB samples, the percentages of Th2/CD4+ and Tfh2/Tfh cells were significantly lower in patients with MM than in HCs (P = 0.00013 and P = 0.0004, respectively), whereas the percentage of Th17/CD4+ and Tfh17/Tfh was significantly higher in newly diagnosed patients with MM than in HCs (P = 0.0037 and P = 0.03, respectively), and all these cells showed a good predictive value for MM (area under the curve [AUC] 0.781, = 0.792, = 0.837, and 0.723 respectively). In the PB samples, all subsets of PD-1+ICOS- Tfh showed a noticeable downward trend in MM from newly diagnosed to non-remission and remission groups. In contrast, all subsets of PD-1-ICOS+ Tfh increased gradually.

Conclusion

Th cell subsets play an important role in the occurrence and development of MM and may provide a fundamental basis for identifying new immunotherapy targets and prognosis.

Clinical and prognostic significance of follicular helper and regulatory T cells in bladder cancer draining lymph nodes

Follicular helper and regulatory T cells (Tfh/TFR) cells are distinct subsets of CD4+ cells that have been recognized for their critical role in regulating cellular reactions within the germinal centers of lymphoid follicles. In the present study, we aimed to determine the presence and the frequency of these cells in draining lymph nodes of patients with bladder cancer (BC). Forty-six patients with BC who had undergone radical cystectomy and pelvic lymph node dissection were enrolled. Following routine pathological examination, a portion of the dissected lymph nodes was minced to obtain a single-cell suspension. Mononuclear cells were then separated using Ficoll-Hypaque gradient centrifugation, and the samples with proper viability (> 95%) were subjected to further analysis. To phenotype the follicular subsets, cells were stained with appropriate fluorochrome-conjugated antibodies specific for CD4, CXCR5, BCL6, and FOXP3. The cells were then acquired on a four-color flow cytometer. The data were analyzed with the FlowJo software version 10.8.1 package. Our analysis indicated that, on average 37.89 ± 16.36% of CD4+ lymphocytes in draining lymph nodes of patients with BC expressed CXCR5. The majority of them were negative for FOXP3, representing helper subsets (28.73 ± 13.66). A small percent simultaneously expressed BCL6 transcription factor (1.65% ± 1.35), designated as Tfh (CD4+BCL6+CXCR5+FOXP3-). While less than 10% of CD4+ lymphocytes expressed CXCR5 and FOXP3, 1.78 ± 2.54 were also positive for BCL6, known as TFR. Statistical analysis revealed that the frequency of both Tfh and TFR cells was higher in draining lymph nodes of patients with tumor-infiltrated nodes (P = 0.035 and P = 0.079, respectively) compared to those with negative ones. The percentage of these cells was also higher in high-grade tumors compared to low-grade ones (P = 0.031 for both). Our data collectively indicated that however approximately one third of CD4+ lymphocytes expressed CXCR5 and accordingly had the capacity to enter the follicles, less than 2% of them represented Tfh and TFR phenotypes. The percentage of these cells increased in progressed tumors and showed an association with negative prognostic factors.

BCL6 is required for the thymic development of TCRαβ+CD8αα+ intraepithelial lymphocyte lineage

TCRαβ+CD8αα+ intraepithelial lymphocytes (CD8αα+ αβ IELs) are a specialized subset of T cells in the gut epithelium that develop from thymic agonist selected IEL precursors (IELps). The molecular mechanisms underlying the selection and differentiation of this T cell type in the thymus are largely unknown. Here, we found that Bcl6 deficiency in αβ T cells resulted in the near absence of CD8αα+ αβ IELs. BCL6 was expressed by approximately 50% of CD8αα+ αβ IELs and by the majority of thymic PD1+ IELps after agonist selection. Bcl6 deficiency blocked early IELp generation in the thymus, and its expression in IELps was induced by thymic TCR signaling in an ERK-dependent manner. As a result of Bcl6 deficiency, the precursors of IELps among CD4+CD8+ double-positive thymocytes exhibited increased apoptosis during agonist selection and impaired IELp differentiation and maturation. Together, our results elucidate BCL6 as a crucial transcription factor during the thymic development of CD8αα+ αβ IELs.

A unique human cord blood CD8+CD45RA+CD27+CD161+ T-cell subset identified by flow cytometric data analysis using Seurat

Advances in single-cell level analytical techniques, especially cytometric approaches, have led to profound innovation in biomedical research, particularly in the field of clinical immunology. This has resulted in an expansion of high-dimensional data, posing great challenges for comprehensive and unbiased analysis. Conventional manual analysis is thus becoming untenable to handle these challenges. Furthermore, most newly developed computational methods lack flexibility and interoperability, hampering their accessibility and usability. Here, we adapted Seurat, an R package originally developed for single-cell RNA sequencing (scRNA-seq) analysis, for high-dimensional flow cytometric data analysis. Based on a 20-marker antibody panel and analyses of T-cell profiles in both adult blood and cord blood (CB), we showcased the robust capacity of Seurat in flow cytometric data analysis, which was further validated by Spectre, another high-dimensional cytometric data analysis package, and conventional manual analysis. Importantly, we identified a unique CD8+ T-cell population defined as CD8+CD45RA+CD27+CD161+ T cell that was predominantly present in CB. We characterised its IFN-γ-producing and potential cytotoxic properties using flow cytometry experiments and scRNA-seq analysis from a published dataset. Collectively, we identified a unique human CB CD8+CD45RA+CD27+CD161+ T-cell subset and demonstrated that Seurat, a widely used package for scRNA-seq analysis, possesses great potential to be repurposed for cytometric data analysis. This facilitates an unbiased and thorough interpretation of complicated high-dimensional data using a single analytical pipeline and opens a novel avenue for data-driven investigation in clinical immunology.

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

BACKGROUND

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

METHOD

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

RESULTS

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

CONCLUSION

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

CD4+ T cells exhibit distinct transcriptional phenotypes in the lymph nodes and blood following mRNA vaccination in humans

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and mRNA vaccination induce robust CD4+ T cell responses. Using single-cell transcriptomics, here, we evaluated CD4+ T cells specific for the SARS-CoV-2 spike protein in the blood and draining lymph nodes (dLNs) of individuals 3 months and 6 months after vaccination with the BNT162b2 mRNA vaccine. We analyzed 1,277 spike-specific CD4+ T cells, including 238 defined using Trex, a deep learning-based reverse epitope mapping method to predict antigen specificity. Human dLN spike-specific CD4+ follicular helper T (TFH) cells exhibited heterogeneous phenotypes, including germinal center CD4+ TFH cells and CD4+IL-10+ TFH cells. Analysis of an independent cohort of SARS-CoV-2-infected individuals 3 months and 6 months after infection found spike-specific CD4+ T cell profiles in blood that were distinct from those detected in blood 3 months and 6 months after BNT162b2 vaccination. Our findings provide an atlas of human spike-specific CD4+ T cell transcriptional phenotypes in the dLNs and blood following SARS-CoV-2 vaccination or infection.

Generation of antigen-specific memory CD4 T cells by heterologous immunization enhances the magnitude of the germinal center response upon influenza infection

Current influenza vaccine strategies have yet to overcome significant obstacles, including rapid antigenic drift of seasonal influenza viruses, in generating efficacious long-term humoral immunity. Due to the necessity of germinal center formation in generating long-lived high affinity antibodies, the germinal center has increasingly become a target for the development of novel or improvement of less-efficacious vaccines. However, there remains a major gap in current influenza research to effectively target T follicular helper cells during vaccination to alter the germinal center reaction. In this study, we used a heterologous infection or immunization priming strategy to seed an antigen-specific memory CD4+ T cell pool prior to influenza infection in mice to evaluate the effect of recalled memory T follicular helper cells in increased help to influenza-specific primary B cells and enhanced generation of neutralizing antibodies. We found that heterologous priming with intranasal infection with acute lymphocytic choriomeningitis virus (LCMV) or intramuscular immunization with adjuvanted recombinant LCMV glycoprotein induced increased antigen-specific effector CD4+ T and B cellular responses following infection with a recombinant influenza strain that expresses LCMV glycoprotein. Heterologously primed mice had increased expansion of secondary Th1 and Tfh cell subsets, including increased CD4+ TRM cells in the lung. However, the early enhancement of the germinal center cellular response following influenza infection did not impact influenza-specific antibody generation or B cell repertoires compared to primary influenza infection. Overall, our study suggests that while heterologous infection or immunization priming of CD4+ T cells is able to enhance the early germinal center reaction, further studies to understand how to target the germinal center and CD4+ T cells specifically to increase long-lived antiviral humoral immunity are needed.

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.

Differentiation and regulation of CD4+ T cell subsets in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease, and its hallmark pathological features are the loss of dopaminergic (DA) neurons in the midbrain substantia nigra pars compacta (SNpc) and the accumulation of alpha-synuclein (α-syn). It has been shown that the integrity of the blood-brain barrier (BBB) is damaged in PD patients, and a large number of infiltrating T cells and inflammatory cytokines have been detected in the cerebrospinal fluid (CSF) and brain parenchyma of PD patients and PD animal models, including significant change in the number and proportion of different CD4+ T cell subsets. This suggests that the neuroinflammatory response caused by CD4+ T cells is an important risk factor for the development of PD. Here, we systematically review the differentiation of CD4+ T cell subsets, and focus on describing the functions and mechanisms of different CD4+ T cell subsets and their secreted cytokines in PD. We also summarize the current immunotherapy targeting CD4+ T cells with a view to providing assistance in the diagnosis and treatment of PD.

Th17-to-Tfh plasticity during periodontitis limits disease pathology

Th17 cell plasticity is crucial for development of autoinflammatory disease pathology. Periodontitis is a prevalent inflammatory disease where Th17 cells mediate key pathological roles, yet whether they exhibit any functional plasticity remains unexplored. We found that during periodontitis, gingival IL-17 fate-mapped T cells still predominantly produce IL-17A, with little diversification of cytokine production. However, plasticity of IL-17 fate-mapped cells did occur during periodontitis, but in the gingiva draining lymph node. Here, some Th17 cells acquired features of Tfh cells, a functional plasticity that was dependent on IL-6. Notably, Th17-to-Tfh diversification was important to limit periodontitis pathology. Preventing Th17-to-Tfh plasticity resulted in elevated periodontal bone loss that was not simply due to increased proportions of conventional Th17 cells. Instead, loss of Th17-to-Tfh cells resulted in reduced IgG levels within the oral cavity and a failure to restrict the biomass of the oral commensal community. Thus, our data identify a novel protective function for a subset of otherwise pathogenic Th17 cells during periodontitis.

Reciprocal regulation of T follicular helper cells and dendritic cells drives colitis development

The immunological mechanisms underlying chronic colitis are poorly understood. T follicular helper (TFH) cells are critical in helping B cells during germinal center reactions. In a T cell transfer colitis model, a lymphoid structure composed of mature dendritic cells (DCs) and TFH cells was found within T cell zones of colonic lymphoid follicles. TFH cells were required for mature DC accumulation, the formation of DC-T cell clusters and colitis development. Moreover, DCs promoted TFH cell differentiation, contributing to colitis development. A lineage-tracing analysis showed that, following migration to the lamina propria, TFH cells transdifferentiated into long-lived pathogenic TH1 cells, promoting colitis development. Our findings have therefore demonstrated the reciprocal regulation of TFH cells and DCs in colonic lymphoid follicles, which is critical in chronic colitis pathogenesis.

Immunological characteristics of a recombinant alphaherpesvirus with an envelope-embedded Cap protein of circovirus

Introduction

Variant pseudorabies virus (PRV) is a newly emerged zoonotic pathogen that can cause human blindness. PRV can take advantage of its large genome and multiple non-essential genes to construct recombinant attenuated vaccines carrying foreign genes. However, a major problem is that the foreign genes in recombinant PRV are only integrated into the genome for independent expression, rather than assembled on the surface of virion.

Methods

We reported a recombinant PRV with deleted gE/TK genes and an inserted porcine circovirus virus 2 (PCV2) Cap gene into the extracellular domain of the PRV gE gene using the Cre-loxP recombinant system combined with the CRISPR-Cas9 gene editing system. This recombinant PRV (PRV-Cap), with the envelope-embedded Cap protein, exhibits a similar replication ability to its parental virus.

Results

An immunogenicity assay revealed that PRV-Cap immunized mice have 100% resistance to lethal PRV and PCV2 attacks. Neutralization antibody and ELISPOT detections indicated that PRV-Cap can enhance neutralizing antibodies to PRV and produce IFN-γ secreting T cells specific for both PRV and PCV2. Immunological mechanistic investigation revealed that initial immunization with PRV-Cap stimulates significantly early activation and expansion of CD69+ T cells, promoting the activation of CD4 Tfh cell dependent germinal B cells and producing effectively specific effector memory T and B cells. Booster immunization with PRV-Cap recalled the activation of PRV-specific IFN-γ+IL-2+CD4+ T cells and IFN-γ+TNF-α+CD8+ T cells, as well as PCV2-specific IFN-γ+TNF-α+CD8+ T cells.

Conclusion

Collectively, our data suggested an immunological mechanism in that the recombinant PRV with envelope-assembled PCV2 Cap protein can serve as an excellent vaccine candidate for combined immunity against PRV and PCV2, and provided a cost-effective method for the production of PRV- PCV2 vaccine.

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.

Resolvin D1 inhibits T follicular helper cell expansion in systemic lupus erythematosus

OBJECTIVE

Resolvin D1 (RvD1) is one of the specialized pro-resolving lipid mediators, which control inflammation resolution and regulate immune responses. Previous research showed that RvD1 could block the progression of systemic lupus erythematosus (SLE). However, the detailed mechanism remains to be fully understood.

METHOD

Plasma RvD1 levels, and proportions of T follicular helper cells (Tfh cells) were measured in SLE patients and healthy controls. Plasma RvD1 levels and proportions of Tfh cells were quantitated in an MRL/lpr mouse model of lupus treated with RvD1. Naïve CD4+ T cells were purified from MRL/lpr mice to study the effect of RvD1 on Tfh cell differentiation in vitro.

RESULTS

In patients, there were significant negative correlations between plasma RvD1 levels and Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) score, as well as between plasma RvD1 and anti-double-stranded DNA antibody levels, and numbers of peripheral Tfh cells and plasma cells. In MRL/lpr mice, the expected amelioration of disease phenotype and inflammatory response with RvD1 treatment correlated with decreased percentages of Tfh cells and plasma cells. In addition, the differentiation and proliferation of Tfh cells were markedly suppressed by RvD1 in vitro.

CONCLUSION

RvD1 may control SLE progression through the suppression of Tfh cell differentiation and subsequent inhibition of B-cell responses.

Mechanisms of antibody mediated immunity - Distinct in early life

Immune responses in early life are characterized by a failure to robustly generate long-lasting protective responses against many common pathogens or upon vaccination. This is associated with a reduced ability to generate T-cell dependent high affinity antibodies. This review highlights the differences in T-cell dependent antibody responses observed between infants and adults, in particular focussing on the alterations in immune cell function that lead to reduced T follicular helper cell-B cell crosstalk within germinal centres in early life. Understanding the distinct functional characteristics of early life humoral immunity, and how these are regulated, will be critical in guiding age-appropriate immunological interventions in the very young.

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.

T-Cell/B-Cell Interactions in Atherosclerosis

Atherosclerosis is a complex inflammatory disease in which the adaptive immune response plays an important role. While the overall impact of T and B cells in atherosclerosis is relatively well established, we are only beginning to understand how bidirectional T-cell/B-cell interactions can exert prominent atheroprotective and proatherogenic functions. In this review, we will focus on these T-cell/B-cell interactions and how we could use them to therapeutically target the adaptive immune response in atherosclerosis.

Follicular helper T cells: emerging roles in lymphomagenesis

Follicular helper T cells are a subset of CD4+ T cells that are fundamental to forming germinal centers, which are the primary sites of antibody affinity maturation and the proliferation of activated B cells. Follicular helper T cells have been extensively studied over the past 10 years, especially regarding their roles in cancer genesis. This review describes the characteristics of normal follicular helper T cells and focuses on the emerging link between follicular helper T cells and lymphomagenesis. Advances in lymphoma genetics have substantially expanded our understanding of the role of follicular helper T cells in lymphomagenesis. Moreover, we detail a range of agents and new therapies, with a major focus on chimeric antigen receptor T-cell therapy; these novel approaches may offer new treatment opportunities for patients with lymphomas.

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.

Adaptive Cellular Responses following SARS-CoV-2 Vaccination in Primary Antibody Deficiency Patients

Since the start of the COVID-19 pandemic, in a short span of 3 years, vaccination against SARS-CoV-2 has resulted in the end of the pandemic. Patients with inborn errors of immunity (IEI) are at an increased risk for SARS-CoV-2 infection; however, serious illnesses and mortality, especially in primary antibody deficiencies (PADs), have been lower than expected and lower than other high-risk groups. This suggests that PAD patients may mount a reasonable effective response to the SARS-CoV-2 vaccine. Several studies have been published regarding antibody responses, with contradictory reports. The current study is, perhaps, the most comprehensive study of phenotypically defined various lymphocyte populations in PAD patients following the SARS-CoV-2 vaccine. In this study, we examined, following two vaccinations and, in a few cases, prior to and following the 1st and 2nd vaccinations, subsets of CD4 and CD8 T cells (Naïve, TCM, TEM, TEMRA), T follicular helper cells (TFH1, TFH2, TFH17, TFH1/17), B cells (naïve, transitional, marginal zone, germinal center, IgM memory, switched memory, plasmablasts, CD21low), regulatory lymphocytes (CD4Treg, CD8Treg, TFR, Breg), and SARS-CoV-2-specific activation of CD4 T cells and CD8 T cells (CD69, CD137), SARS-CoV-2 tetramer-positive CD8 T cells, and CD8 CTL. Our data show significant alterations in various B cell subsets including Breg, whereas only a few subsets of various T cells revealed alterations. These data suggest that large proportions of PAD patients may mount significant responses to the vaccine.

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.

Specialized Tfh cell subsets driving type-1 and type-2 humoral responses in lymphoid tissue

Effective antibody responses are essential to generate protective humoral immunity. Different inflammatory signals polarize T cells towards appropriate effector phenotypes during an infection or immunization. Th1 and Th2 cells have been associated with the polarization of humoral responses. However, T follicular helper cells (Tfh) have a unique ability to access the B cell follicle and support the germinal center (GC) responses by providing B cell help. We investigated the specialization of Tfh cells induced under type-1 and type-2 conditions. We first studied homogenous Tfh cell populations generated by adoptively transferred TCR-transgenic T cells in mice immunized with type-1 and type-2 adjuvants. Using a machine learning approach, we established a gene expression signature that discriminates Tfh cells polarized towards type-1 and type-2 response, defined as Tfh1 and Tfh2 cells. The distinct signatures of Tfh1 and Tfh2 cells were validated against datasets of Tfh cells induced following lymphocytic choriomeningitis virus (LCMV) or helminth infection. We generated single-cell and spatial transcriptomics datasets to dissect the heterogeneity of Tfh cells and their localization under the two immunizing conditions. Besides a distinct specialization of GC Tfh cells under the two immunizations and in different regions of the lymph nodes, we found a population of Gzmk+ Tfh cells specific for type-1 conditions. In human individuals, we could equally identify CMV-specific Tfh cells that expressed Gzmk. Our results show that Tfh cells acquire a specialized function under distinct types of immune responses and with particular properties within the B cell follicle and the GC.