BCL6 controls contact-dependent help delivery during follicular T-B cell interactions

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.

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.

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.

Transcriptomic and proteomic analysis reveals the mechanism of chicken cecum response to Salmonella enterica serovar Enteritidis inoculation

Salmonella enterica serovar Enteritidis (SE) incurs foodborne illnesses and poses a severe threat to poultry industry and human health. However, the molecular mechanisms underlying chicken responding to SE inoculation remain elusive. Here, we characterized the transcriptome and proteome of chicken cecum 3 days post SE inoculation. Totally, there were 332 differentially expressed genes and 563 differentially expressed protein identified. The upregulated genes were enriched in immune-related processes. The downregulated proteins mainly correlated with metabolic process. The correlation coefficient between the transcriptome and proteome was 0.14. Collectively, we characterized the landscape of mRNAs and proteins in chicken cecum following SE inoculation and found SE inoculation induced chicken immune system at transcriptomic level but impaired the metabolism at protein level. The differences may be caused by complex post-transcriptional regulatory mechanisms or time-dependent delays. Our findings would extend the understanding of the molecular mechanisms underlying chicken responding to SE inoculation.

Enhancing the Deformability of the Adjuvant: Achieving Lymph Node Targeted Delivery to Elicit a Long-Lasting Immune Protection

A key challenge in vaccine development is to induce an effective and durable immune response. Live virus vaccines induce lifelong antibody responses; however, the immune responses induced by inactivated or subunit vaccines decrease gradually. Activation of the germinal center (GC) reaction, which generates long-lived plasma cells (LLPCs), is a key mediator of long-term antibody responses. To enhance the activation of GC, lymph node-targeted delivery of the vaccine is promoted by enhancing the deformability of the delivery vector. In this study, a double emulsion is designed with strong deformability and containing chitosan nanoparticles (CSNP) in the internal aqueous phase (WNP) for efficient antigen loading, called WNP/O/W. The flexible oil layer and the internally loaded positively charged particles endow the emulsion with strong deformability, continuously enrich model antigen ovalbumin (OVA) in the lymph nodes, activate germinal center B (GC B) cells and T follicular helper (TFH) cells, induce LLPCs, and obtain high-level antibody persistence for more than 5 months, which is significantly better than the traditional oil emulsion adjuvant. Concurrently, it also improves the immune-protective effect in aged mice. Altogether, these results indicate that WNP/O/W achieves lymph node targeted delivery by strengthening deformability, generating high-intensity antibody responses, and long-lasting immune protection.

Immune imbalance in Lupus Nephritis: The intersection of T-Cell and ferroptosis

Ferroptosis is a novel form of cell death characterized by unlimited accumulation of iron-dependent lipid peroxides. It is often accompanied by disease, and the relationship between ferroptosis of immune cells and immune regulation has been attracting increasing attention. Initially, it was found in cancer research that the inhibition of regulatory T cell (Treg) ferroptosis and the promotion of CD8+ T cell ferroptosis jointly promoted the formation of an immune-tolerant environment in tumors. T-cell ferroptosis has subsequently been found to have immunoregulatory effects in other diseases. As an autoimmune disease characterized by immune imbalance, T-cell ferroptosis has attracted attention for its potential in regulating immune balance in lupus nephritis. This article reviews the metabolic processes within different T-cell subsets in lupus nephritis (LN), including T follicular helper (TFH) cells, T helper (Th)17 cells, Th1 cells, Th2 cells, and Treg cells, and reveals that these cellular metabolisms not only facilitate the formation of a T-cell immune imbalance but are also closely associated with the occurrence of ferroptosis. Consequently, we hypothesize that targeting the metabolic pathways of ferroptosis could become a novel research direction for effectively treating the immune imbalance in lupus nephritis by altering T-cell differentiation and the incidence of ferroptosis.

Mechanism and therapeutic targets of circulating immune cells in diabetic retinopathy

Diabetic retinopathy (DR) continues to be the leading cause of preventable vision loss among working-aged adults, marked by immune dysregulation within the retinal microenvironment. Typically, the retina is considered as an immune-privileged organ, where circulating immune cells are restricted from entry under normal conditions. However, during the progression of DR, this immune privilege is compromised as circulating immune cells breach the barrier and infiltrate the retina. Increasing evidence suggests that vascular and neuronal degeneration in DR is largely driven by the infiltration of immune cells, particularly neutrophils, monocyte-derived macrophages, and lymphocytes. This review delves into the mechanisms and therapeutic targets associated with these immune cell populations in DR, offering a promising and innovative approach to managing the disease.

Quercetin ameliorates lupus symptoms by promoting the apoptosis of senescent Tfh cells via the Bcl-2 pathway

Systemic lupus erythematosus (SLE) is an autoimmune disorder that commonly affects the skin, kidneys, joints, and various other systemic tissues, with its development intricately linked to the process of immunosenescence. Quercetin (QC), a phytochemical that occurs naturally, demonstrates many different biological capabilities, such as antibacterial, antioxidant, and anti-inflammatory activities. Our investigation found that QC effectively reduced kidney damage and relieved mesenteric lymph nodes (mLNs) swelling in MRL/lpr lupus mice. Moreover, QC has been found to decrease the number of senescent follicular helper T (Tfh) cells, a pivotal kind of T cells that contribute to the progression of SLE. In vitro, QC exhibited the capacity to modulate mRNA expression levels, with the downregulation of IL-6, IL21-AS1, IL-27, BCL6, and BCL2L12, and the upregulation of FOXP1 and BIM. This modulation resulted in the suppression of Tfh cells differentiation and the enhancement of apoptosis in senescent CD4+ T cells. In addition, the HuProtTM Human Proteome Microarray revealed that QC can directly bind to BCL-2 protein and therefore promote the apoptosis of senescent CD4+ T cell. As a result, our investigative elucidate the potent inhibitory action of QC on the ontogeny of Tfh cells, along with its capacity to abrogate the immunosenescent phenotype. This positions QC as a promising therapeutic strategy for treating SLE.

Occurrence and role of Tph cells in various renal diseases

A new population of peripheral helper T (Tph) cells has been identified and contributed to various autoimmune diseases. Tph cells can secrete interleukin-21 (IL-21), interferon (IFN) and C-X-C motif chemokine ligand 13 (CXCL13) to moderate renal disease. Moreover, Tph cells can congregate in huge numbers and immerse within inflamed tissue. Compared to Tfh cells, Tph cells express high programmed cell death protein 1 (PD-1), major histocompatibility complex II (MHC-II), C-C chemokine receptor 2 (CCR2) and C-C chemokine receptor 5 (CCR5) but often lack expression of the chemokine receptor C-X-C chemokine receptor 5 (CXCR5). They display features distinct from other T cells, which are uniquely poised to promote responses and antibody production of B cells within pathologically inflamed non-lymphoid tissues and a key feature of Tph cells. In this review, we summarize recent findings on the role of Tph cells in chronic kidney disease, acute kidney injury, kidney transplantation and various renal diseases.

Effect of Moniezia Benedeni infection on ileal transcriptome profile characteristics of sheep

BACKGROUND

The intestinal mucosal immune system, renowned for its precise and sensitive regulation, can provide comprehensive and effective protection for the body, among which the ileum is a critical induction site for regulating mucosal immune homeostasis. Moniezia benedeni parasitizes the small intestine of sheep and can cause serious pathological damage or even death to the host when the infection is severe. In this study, 5 sheep infected with Moniezia benedeni were selected as the infected group, and 5 uninfected sheep were selected as the control group. The ileal transcriptome profile characteristics of Moniezia benedeni infection were analyzed based on RNA-seq sequencing technology, aiming to lay a foundation for further exploring the perception mechanism of sheep intestines to Moniezia benedeni infection and formulating effective prevention and control strategies.

RESULTS

The results showed that a total of 3,891 differentially expressed genes (DEGs) were detected in the ileum tissues of sheep between the infected and control groups with 2,429 up-regulated genes and 1,462 down-regulated genes. GO and KEGG pathway enrichment analysis of differential genes, as well as Clue GO analysis showed that differential genes were significantly enriched in immune and metabolic-related biological processes and signaling pathways. Particularly, in immune-related signaling pathways, the B cell receptor signaling pathway was significantly down-regulated, while in metabolic regulation related signaling pathways, Bile secretion, Fat digestion and absorption and Vitamin digestion and absorption were notably up-regulated. On this basis, the differential core genes related to immune metabolism were verified by qRT-PCR method. The results showed that OVAR, CD3E, CD8A, CD4 and CD28 were significantly up-regulated (P < 0.05), while CIITA, BLNK, BCL6 and CD79A were significantly down-regulated (P < 0.05), which were consistent with transcriptome sequencing data.

CONCLUSIONS

The results demonstrated that Moniezia benedeni infection significantly affected the immune and metabolic processes in sheep ileum, particularly, it significantly inhibited the activation process of host B cells, and also led to an overactive function of bile acid metabolism. This finding provides a solid foundation for further elucidating the response mechanism of Peyer's patches in sheep ileum to Moniezia tapeworm infection.

Follicular CD8+ T cells promote immunoglobulin production and demyelination in multiple sclerosis and a murine model

Emerging evidence underscores the importance of CD8+ T cells in the pathogenesis of multiple sclerosis (MS), but the precise mechanisms remain ambiguous. This study intends to elucidate the involvement of a novel subset of follicular CD8+ T cells (CD8+CXCR5+ T) in MS and an experimental autoimmune encephalomyelitis (EAE) murine model. The expansion of CD8+CXCR5+ T cells was observed in both MS patients and EAE mice during the acute phase. In relapsing MS patients, higher frequencies of circulating CD8+CXCR5+ T cells were positively correlated with new gadolinium-enhancement lesions in the central nervous system (CNS). In EAE mice, frequencies of CD8+CXCR5+ T cells were also positively correlated with clinical scores. These cells were found to infiltrate into ectopic lymphoid-like structures in the spinal cords during the peak of the disease. Furthermore, CD8+CXCR5+ T cells, exhibiting high expression levels of ICOS, CD40L, IL-21, and IL-6, were shown to facilitate B cell activation and differentiation through a synergistic interaction between CD40L and IL-21. Transferring CD8+CXCR5+ T cells into naïve mice confirmed their ability to enhance the production of anti-MOG35-55 antibodies and contribute to the disease progression. Consequently, CD8+CXCR5+ T cells may play a role in CNS demyelination through heightening humoral immune responses.

Correlation of cTfh cells and memory B cells with AMR after renal transplantation

Renal transplantation is the preferred treatment option for patients with end-stage renal disease (ESRD) in a clinical setting. Antibody mediated rejection (AMR) is one of the leading causes of graft dysfunction. To address the current shortcomings in the early diagnosis and treatment of AMR in clinical practice, this article analyzes the distribution of different circulating T follicular helper (cTfh) cell subtypes and B cell subpopulations in peripheral blood and detects the cytokine levels of chemokine ligand 13 (CXCL13), interleukin-21 (IL-21), and interleukin-4 (IL-4) related to cTfh cells in peripheral blood of kidney transplant recipients. Moreover, we also explore the correlation between cTfh cells, peripheral blood memory B cells, and AMR, their value as early predictive indicators of AMR, and explore potential therapeutic targets for AMR patients. Our results indicate that the proportion of cTfh cells increased at the onset of AMR, which plays an important role in antigen-specific B-cell immune regulation. Activation of cTfh cells in AMR patients correlates with phenotypes of memory B cells and plasma blasts. cTfh cells and memory B cells have promising diagnostic efficacies and predictive values for AMR. The proportion of cTfh cells to CD4+ T cells and the proportion of memory B cells to CD19+ B cells are correlated with serum creatinine levels, indicating that cTfh cells and memory B cells may be involved in the progression of AMR. In addition, the CXCL13, IL-21, and IL-4, which were associated with cTfh cells, may be involved in the onset of AMR.

Roles of Menin in T cell differentiation and function: Current knowledge and perspectives

The commitment to specific T lymphocytes (T cell) lineages is governed by distinct transcription factors, whose expression is modulated through epigenetic mechanisms. Unravelling these epigenetic mechanisms that regulate T cell differentiation and function holds significant importance for understanding T cells. Menin, a multifunctional scaffolding protein, is implicated in various cellular processes, such as cell proliferation, cell cycle control, DNA repair and transcriptional regulation, primarily through epigenetic mechanisms. Existing research indicates Menin's impact on T cell differentiation and function, while a comprehensive and systematic review is currently lacking to consolidate these findings. In the current review, we have highlighted recent studies on the role of Menin in T cell differentiation and function, focusing mainly on its impact on the memory Th2 maintenance, Th17 differentiation and maintenance, CD4+ T cell senescence, and effector CD8+ T cell survival. Considering Menin's crucial function in maintaining effector T cell function, the potential of inhibiting Menin activity in mitigating inflammatory diseases associated with excessive T cell activation has also been emphasised.

Synergistic effects of oral inoculation with a recombinant Lactobacillus plantarum NC8 strain co-expressing interleukin-2 and interleukin-17B on the efficacy of the infectious bronchitis vaccine in chickens

Mucosal vaccination strategies are easier to implement than others in large-scale poultry farming. However, the adjuvants that are approved for veterinary use, which are predominantly aluminum- and oil-emulsion-based adjuvants, are not suitable for mucosal vaccination and carry a risk of adverse reactions. In this study, we engineered a novel Lactobacillus plantarum NC8 strain that co-expresses chicken interleukin-2 (IL-2) and IL-17B, which we designated NC8-ChIL2-17B, and evaluated its potential as an oral immunoadjuvant. The immunomodulatory properties of NC8-ChIL2-17B were evidenced by its ability to activate macrophages and inhibit the proliferation of infectious bronchitis virus (IBV) in vitro. We then confirmed its immunoadjuvant activity in vivo by orally administering NC8-ChIL2-17B along with a commercial IBV vaccine to chicks. The results indicated that NC8-ChIL2-17B enhanced the immune response elicited by the IBV vaccine and increased the levels of IBV-specific IgG and sIgA antibodies produced in response to IBV infection. Additionally, administration of NC8-ChIL2-17B promoted weight gain and beneficially modulated the gut microbiota, resulting in improved chicken performance. These findings suggest that oral administration of NC8-ChIL2-17B is a promising strategy to enhance the immune efficacy of the IBV vaccine in chickens, offering an efficacious alternative adjuvant.

Canine mesenteric lymph nodes (MLNs) characterization by sc-RNAseq: insights compared to human and mouse MLNs

In the human and veterinary fields, oral vaccines generate considerable interest. In dogs, these vaccines are newly developed, and understanding their mechanisms is crucial. Mesenteric lymph nodes (MLNs) and Peyer's patches (PPs) are important sites for gastrointestinal mucosal induction, yet canine MLNs lack sufficient information. To address this, we collected MLN samples from healthy dogs, performed flow cytometry to characterize immune cells, and conducted single-cell RNA sequencing (scRNA-seq) to explore subpopulations, particularly B and T lymphocytes. This effort enabled the characterization of canine MLN's main cell populations and the construction of a predictive atlas, as well as the identification of particularities of this area.

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.

Single-cell transcriptome profiles the heterogeneity of tumor cells and microenvironments for different pathological endometrial cancer and identifies specific sensitive drugs

Endometrial cancer (EC) is a highly heterogeneous malignancy characterized by varied pathology and prognoses, and the heterogeneity of its cancer cells and the tumor microenvironment (TME) remains poorly understood. We conducted single-cell RNA sequencing (scRNA-seq) on 18 EC samples, encompassing various pathological types to delineate their specific unique transcriptional landscapes. Cancer cells from diverse pathological sources displayed distinct hallmarks labeled as immune-modulating, proliferation-modulating, and metabolism-modulating cancer cells in uterine clear cell carcinomas (UCCC), well-differentiated endometrioid endometrial carcinomas (EEC-I), and uterine serous carcinomas (USC), respectively. Cancer cells from the UCCC exhibited the greatest heterogeneity. We also identified potential effective drugs and confirmed their effectiveness using patient-derived EC organoids for each pathological group. Regarding the TME, we observed that prognostically favorable CD8+ Tcyto and NK cells were prominent in normal endometrium, whereas CD4+ Treg, CD4+ Tex, and CD8+ Tex cells dominated the tumors. CXCL3+ macrophages associated with M2 signature and angiogenesis were exclusively found in tumors. Prognostically relevant epithelium-specific cancer-associated fibroblasts (eCAFs) and SOD2+ inflammatory CAFs (iCAFs) predominated in EEC-I and UCCC groups, respectively. We also validated the oncogenic effects of SOD2+ iCAFs in vitro. Our comprehensive study has yielded deeper insights into the pathogenesis of EC, potentially facilitating personalized treatments for its varied pathological types.

[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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Heterologous booster vaccination enhances antibody responses to SARS-CoV-2 by improving Tfh function and increasing B-cell clonotype SHM frequency

Heterologous prime-boost has broken the protective immune response bottleneck of the COVID-19 vaccines. however, the underlying mechanisms have not been fully elucidated. Here, we investigated antibody responses and explored the response of germinal center (GC) to priming with inactivated vaccines and boosting with heterologous adenoviral-vectored vaccines or homologous inactivated vaccines in mice. Antibody responses were dramatically enhanced by both boosting regimens. Heterologous immunization induced more robust GC activation, characterized by increased Tfh cell populations and enhanced helper function. Additionally, increased B-cell activation and antibody production were observed in a heterologous regimen. Libra-seq was used to compare the differences of S1-, S2- and NTD-specific B cells between homologous and heterologous vaccination, respectively. S2-specific CD19+ B cells presented increased somatic hypermutations (SHMs), which were mainly enriched in plasma cells. Moreover, a heterologous booster dose promoted the clonal expansion of B cells specific to S2 and NTD regions. In conclusion, the functional role of Tfh and B cells following SARS-CoV-2 heterologous vaccination may be important for modulating antibody responses. These findings provide new insights for the development of SARS-CoV-2 vaccines that induce more robust antibody response.

The aged microenvironment impairs BCL6 and CD40L induction in CD4+ T follicular helper cell differentiation

Weakened germinal center responses by the aged immune system result in diminished immunity against pathogens and reduced efficacy of vaccines. Prolonged contacts between activated B cells and CD4+ T cells are crucial to germinal center formation and T follicular helper cell (Tfh) differentiation, but it is unclear how aging impacts the quality of this interaction. Peptide immunization confirmed that aged mice have decreased expansion of antigen-specific germinal center B cells and reduced antibody titers. Furthermore, aging was associated with accumulated Tfh cells, even in naïve mice. Despite increased numbers, aged Tfh had reduced expression of master transcription factor BCL6 and increased expression of the ectonucleotidase CD39. In vitro activation revealed that proliferative capacity was maintained in aged CD4+ T cells, but not the costimulatory molecule CD40L. When activated in vitro by aged antigen-presenting cells, young CD4+ naïve T cells generated reduced numbers of activated cells with upregulated CD40L. To determine the contribution of cell-extrinsic influences on antigen-specific Tfh induction, young, antigen-specific B and CD4+ T cells were adoptively transferred into aged hosts prior to peptide immunization. Transferred cells had reduced expansion and differentiation into germinal center B cell and Tfh and reduced antigen-specific antibody titers when compared to young hosts. Young CD4+ T cells transferred aged hosts differentiated into Tfh cells with reduced PD-1 and BCL6 expression, and increased CD39 expression, though they maintained their mitochondrial capacity. These results highlight the role of the lymphoid microenvironment in modulating CD4+ T cell differentiation, which contributes to impaired establishment and maintenance of germinal centers.

Targeting TFH cells is a novel approach for donor-specific antibody desensitization of allograft candidates: an in vitro and in vivo study

The presence of donor-specific antibodies (DSA) are associated with graft failure either following human leukocyte antigen (HLA)-mismatched allogeneic stem cell transplantation or after organ transplantation. Although targeting B cells and plasma cells have been used for desensitization, there have been reports of failure. T-follicular helper (Tfh) cells assist B cells in differentiating into antibody-secreting plasma cells. We used haploidentical allograft as a platform to investigate the possibility of targeting Tfh cells to desensitize DSA. The quantities of circulating Tfh (cTfh) cell subsets in allograft candidates were abnormal, and these cells, including the cTfh2 and cTfhem cell subsets, were positively related to the production of anti-HLA antibodies. Ex vivo experiments showed that the cTfh cells of anti-HLA antibody-positive allograft candidates could induce B cells to differentiate into DSA-producing plasmablasts. The immune synapse could be involved in the assistance of cTfh cells to B cells in antibody production. In vitro experiments and in vivo clinical pilot studies indicated that targeting cTfh cells with sirolimus can inhibit their auxiliary function in assisting B cells. Ex vivo and in vivo studies demonstrated the effect of sirolimus and rituximab on DSA desensitization compared with either sirolimus or rituximab alone (60%, 43.75%, and 30%, respectively). Our findings provide new insight into the role of Tfh cells in the pathogenesis of DSA production in HLA-mismatched transplant candidates. Our data also indicate that targeting Tfh cells is a novel strategy for DSA desensitization and combination of sirolimus and rituximab might be a potential therapy. The prospective cohort of this study is registered at http://www.chictr.org.cn as #ChiCTR-OPC-15006672.

IRF4 induces M1 macrophage polarization and aggravates ulcerative colitis progression by the Bcl6-dependent STAT3 pathway

Ulcerative colitis (UC) is an idiopathic chronic intestinal inflammation. An increasing body of evidence shows that macrophages play an important role in the pathogenesis of UC. Interferon regulatory factor 4 (IRF4) is crucial for the development of autoimmune diseases via regulating immune cells. This research was designed to explore the function of IRF4 in UC and its association with macrophage polarization. The in vitro model of UC was established by stimulating colonic epithelial cells with tumor necrosis factor α (TNF-α). A mouse model of UC was constructed by injecting C57BL/6 mice with dextran sulfate sodium salt. Flow cytometry was used to assess percentage of CD11b+ CD86+ and CD11b+ CD206+ cells in bone marrow macrophages. Occult blood tests were used to detect hematochezia. Hematoxylin and eosin staining assay was used to assess colon pathological changes. Enzyme-linked immunosorbent assay (ELISA) was used to detect concentrations of inflammatory cytokines. The interaction of IRF4 and B-cell lymphoma 6 (Bcl6) was confirmed using GST pull-down and coimmunoprecipitation assays. Our findings revealed that IRF4 promoted cell apoptosis and stimulated M1 macrophage polarization in vitro. Furthermore, IRF4 aggravated symptoms of the mouse model of UC and aggravated M1 macrophage polarization in vivo. IRF4 negatively regulated Bcl6 expression. Downregulation of Bcl6 promoted apoptosis and M1 macrophage polarization in the presence of IRF4 in vitro and in vivo. Moreover, Bcl6 positively mediated the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway. In conclusion, IRF4 aggravated UC progression through promoting M1 macrophage polarization via Bcl6/JAK2/STAT3 pathway. These findings suggested that IRF4 might be a good target to competitively inhibit or to treat with UC.

Defective mitochondria remodelling in B cells leads to an aged immune response

The B cell response in the germinal centre (GC) reaction requires a unique bioenergetic supply. Although mitochondria are remodelled upon antigen-mediated B cell receptor stimulation, mitochondrial function in B cells is still poorly understood. To gain a better understanding of the role of mitochondria in B cell function, here we generate mice with B cell-specific deficiency in Tfam, a transcription factor necessary for mitochondrial biogenesis. Tfam conditional knock-out (KO) mice display a blockage of the GC reaction and a bias of B cell differentiation towards memory B cells and aged-related B cells, hallmarks of an aged immune response. Unexpectedly, blocked GC reaction in Tfam KO mice is not caused by defects in the bioenergetic supply but is associated with a defect in the remodelling of the lysosomal compartment in B cells. Our results may thus describe a mitochondrial function for lysosome regulation and the downstream antigen presentation in B cells during the GC reaction, the dysruption of which is manifested as an aged immune response.

The differentiation courses of the Tfh cells: a new perspective on autoimmune disease pathogenesis and treatment

The follicular helper T cells are derived from CD4+T cells, promoting the formation of germinal centers and assisting B cells to produce antibodies. This review describes the differentiation process of Tfh cells from the perspectives of the initiation, maturation, migration, efficacy, and subset classification of Tfh cells, and correlates it with autoimmune disease, to provide information for researchers to fully understand Tfh cells and provide further research ideas to manage immune-related diseases.

Dynamic Multiplex Tissue Imaging in Inflammation Research

Inflammation is a highly dynamic process with immune cells that continuously interact with each other and parenchymal components as they migrate through tissue. The dynamic cellular responses and interaction patterns are a function of the complex tissue environment that cannot be fully reconstructed ex vivo, making it necessary to assess cell dynamics and changing spatial patterning in vivo. These dynamics often play out deep within tissues, requiring the optical focus to be placed far below the surface of an opaque organ. With the emergence of commercially available two-photon excitation lasers that can be combined with existing imaging systems, new avenues for imaging deep tissues over long periods of time have become available. We discuss a selected subset of studies illustrating how two-photon microscopy (2PM) has helped to relate the dynamics of immune cells to their in situ function and to understand the molecular patterns that govern their behavior in vivo. We also review some key practical aspects of 2PM methods and point out issues that can confound the results, so that readers can better evaluate the reliability of conclusions drawn using this technology.

Helios characterized circulating follicular helper T cells with enhanced functional phenotypes and was increased in patients with systemic lupus erythematosus

Helios was related to the immunosuppressive capacity and stability of regulatory T cells. However, the significance of Helios in follicular help T (TFH) and follicular regulatory T (TFR) cells is unclear. This research aimed to clarify the significance of Helios (IKZF2) in TFH and TFR cells and its clinical value in systemic lupus erythematosus (SLE). IKZF2 mRNA in different cell subsets was analyzed. Helios+ percentages in TFH and TFR cells were identified in the peripheral blood of 75 SLE patients and 62 HCs (healthy controls). PD-1 and ICOS expression were compared between Helios+ and Helios- cells. The capacity of TFH cells to secrete IL-21 and TFR cells to secrete IL-10 was measured. Correlation analysis and receiver operating characteristic (ROC) curve analysis were conducted to assess the clinical significance of Helios-related TFH and TFR cell subsets in SLE. There was Helios expression in TFH and TFR cells. PD-1 and ICOS were lower in Helios+ TFR than in Helios- TFR. ICOS was increased in Helios+ TFH cells compared with Helios- TFH cells, and ICOS in Helios+ TFH cells was downregulated in SLE. Helios+ TFH cells secreted more IL-21 than Helios- TFH cells, and Helios+ TFH cells from SLE patients had a stronger IL-21 secretion than HCs. Helios+ TFH percentages were negatively correlated with C3 and C4 and positively related to CRP and SLEDAI, and the AUC of Helios+ TFH to distinguish SLE from HC was 0.7959. Helios characterizes circulating TFH cells with enhanced function. Increased Helios+ TFH cells could reflect the autoimmune status of SLE.

Progenitor-like exhausted SPRY1+CD8+ T cells potentiate responsiveness to neoadjuvant PD-1 blockade in esophageal squamous cell carcinoma

Neoadjuvant immune checkpoint blockade (ICB) demonstrates promise in operable esophageal squamous cell carcinoma (ESCC), but lacks available efficacy biomarkers. Here, we perform single-cell RNA-sequencing of tumors from patients with ESCC undergoing neoadjuvant ICB, revealing a subset of exhausted CD8+ T cells expressing SPRY1 (CD8+ Tex-SPRY1) that displays a progenitor exhausted T cell (Tpex) phenotype and correlates with complete response to ICB. We validate CD8+ Tex-SPRY1 cells as an ICB-specific predictor of improved response and survival using independent ICB-/non-ICB cohorts and demonstrate that expression of SPRY1 in CD8+ T cells enforces Tpex phenotype and enhances ICB efficacy. Additionally, CD8+ Tex-SPRY1 cells contribute to proinflammatory phenotype of macrophages and functional state of B cells, which thereby promotes antitumor immunity by enhancing CD8+ T cell effector functions. Overall, our findings unravel progenitor-like CD8+ Tex-SPRY1 cells' role in effective responses to ICB for ESCC and inform mechanistic biomarkers for future individualized immunotherapy.

Germinal center reaction and output: recent advances

The germinal center (GC) reaction is unique in that it incorporates clonal expansion, somatic mutagenesis, affinity-based selection, and differentiation events all in one tightly packed but highly dynamic microenvironment to produce affinity-matured plasma cells (PCs) or memory B cells (MBCs). Here, we review recent advances in our understanding of how cyclic expansion and selection are orchestrated, how stringency and efficiency of selection are maintained, and how external signals are integrated in B cells to promote post-GC development of PCs and MBCs.

Small-molecule BCL6 inhibitor protects chronic cardiac transplant rejection and inhibits T follicular helper cell expansion and humoral response

Background: B cell lymphoma 6 (BCL6) is an important transcription factor of T follicular helper (Tfh) cells, which regulate the humoral response by supporting the maturation of germinal center B cells and plasma cells. The aim of this study is to investigate the expansion of T follicular helper cells and the effect of the BCL6 inhibitor FX1 in acute and chronic cardiac transplant rejection models.

Methods: A mouse model of acute and chronic cardiac transplant rejection was established. Splenocytes were collected at different time points after transplantation for CXCR5+PD-1+ and CXCR5+BCL6+ Tfh cells detection by flow cytometry (FCM). Next, we treated the cardiac transplant with BCL6 inhibitor FX1 and the survival of grafts was recorded. The hematoxylin and eosin, Elastica van Gieson, and Masson staining of cardiac grafts was performed for the pathological analysis. Furthermore, the proportion and number of CD4+ T cells, effector CD4+ T cells (CD44+CD62L−), proliferating CD4+ T cells (Ki67+), and Tfh cells in the spleen were detected by FCM. The cells related to humoral response (plasma cells, germinal center B cells, IgG1+ B cells) and donor-specific antibody were also detected.

Results: We found that the Tfh cells were significantly increased in the recipient mice on day 14 post transplantation. During the acute cardiac transplant rejection, even the BCL6 inhibitor FX1 did not prolong the survival or attenuate the immune response of cardiac graft, the expansion of Tfh cell expansion inhibit. During the chronic cardiac transplant rejection, FX1 prolonged survival of cardiac graft, and prevented occlusion and fibrosis of vascular in cardiac grafts. FX1 also decreased the proportion and number of splenic CD4+ T cells, effector CD4+ T cells, proliferating CD4+ T cells, and Tfh cells in mice with chronic rejection. Moreover, FX1 also inhibited the proportion and number of splenic plasma cells, germinal center B cells, IgG1+ B cells, and the donor-specific antibody in recipient mice.

Conclusion: We found BCL6 inhibitor FX1 protects chronic cardiac transplant rejection and inhibits the expansion of Tfh cells and the humoral response, which suggest that BCL6 is a potential therapeutic target of the treatment for chronic cardiac transplant rejection.

Targeting Bcl-6 prevents sclerodermatous chronic graft-versus-host disease by abrogating T follicular helper differentiation in mice

BACKGROUND

Chronic graft-versus-host disease (cGVHD) is the most common cause of non-relapse mortality (NRM) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). CD4⁺ follicular helper T (Tfh) cells, specialized providers of T cell help to B cells, play a vital role in GVHD pathogenesis. B-cell lymphoma-6 (Bcl-6) transcription factor has been shown to be required for Tfh-mediated germinal center reactions. In this study, we would like to evaluate the effect of Bcl-6 on Tfh function in sclerodermatous cGVHD and the efficacy of Bcl-6 inhibitors (Bcl-6i) for treating a minor histocompatibility complex (miHC) mismatch model of sclerodermatous cGVHD (scl-cGVHD).

METHODS

A minor histocompatibility haploidentical model of scl-cGVHD was established and received intraperitoneal injection of 79-6, a small-molecule inhibitor of Bcl-6. The clinical manifestations and survival times of cGVHD mice were recorded. The histological assessment was performed by hematoxylin-eosin (HE) and Masson's trichrome staining on the skin and lung tissues. Tfh cells and germinal center B cells in the spleen and peripheral blood were detected by flow cytometry. The cellular markers were immunostained in different organs. ELISA was performed to detect cytokine secretion.

RESULTS

Bcl-6 inhibition by 79-6 improved the clinical manifestation of scl-cGVHD mice and prolonged their survival. The histopathologic damage, particular the fibrotic changes of scl-cGVHD mice was significantly relieved after 79-6 treatment. Furthermore, 79-6 treatment not only suppressed the development and function of Tfh and Tph cells in the peripheral blood, but also reduced the survival of Tfh cells in the spleen. Moreover, 79-6 decreased the frequency of GC plasmocytes accompanied by a reduction in IL-21.

CONCLUSIONS

Our study demonstrates that Bcl-6 inhibitor could prevent murine sclerodermatous chronic graft-versus-host disease by abrogating T follicular helper differentiation and suppressing the function of GC B cells, indicating that Bcl-6 inhibition may be a potential treatment for patients with cGVHD.

T follicular helper cells in autoimmune diseases

T follicular helper (Tfh) cells with the phenotype of mainly expressing surface molecules C-X-C motif chemokine receptor type 5 (CXCR5), inducible co-stimulator (ICOS), secreting cytokine interleukin-21 (IL-21) and requiring the transcription factor B cell lymphoma 6 (BCL-6) have been recently defined as a new subset of CD4⁺ T cells. They exist in germinal centers (GCs) of lymphoid organs and in peripheral blood. With the ability to promote B cell development, GC formation and antibody production, Tfh cells play critical roles in the pathogenesis of many autoimmune diseases, such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), primary Sjögren's syndrome (pSS), etc. The aberrant proliferation and function of Tfh cells will cause the pathological process like autoantibody production and tissue injury. In this paper, we review the recent advances in Tfh cell biology and their roles in autoimmune diseases, with a mention of their use as therapeutic targets, which will shed more light on the pathogenesis and treatment of certain autoimmune diseases.

Phenotypes of peripheral CD4+ T helper cell subsets in pregnant women with HBeAg-negative chronic asymptomatic HBV carriers

Background

Chronic hepatitis B virus (HBV) infection is a major public health problem worldwide, and mother-to-child transmission is the key mode of HBV infection. CD4⁺ T helper (Th) cells play a critical role in the immune microenvironment of specific maternal tolerance to the foetus during pregnancy. However, the roles of Th cell subsets in pregnant women (PW) with chronic asymptomatic HBV carriers (ASCs) remain completely unclear. Here, we aimed to characterize CD4⁺ T-cell immunity in PW with hepatitis Be antigen (HBeAg)-negative chronic ASCs.

Methods

Human peripheral blood mononuclear cells (PBMCs) from PW without HBV infection or with chronic ASCs and healthy controls (HC) were isolated, and CD4⁺ Th cell subsets were detected by flow cytometry in addition to serum cytokines. Serological HBV markers, liver function and hormone levels of these individuals were also tested.

Results

The frequencies of circulating T follicular helper (Tfh) type 2 (Tfh2) cells were significantly evaluated, but Tfh1 cell frequencies were notably decreased in PW compared to HC. Moreover, the frequencies of Th22 cells were only notably increased in PW with chronic ASCs in comparison with PW. Additionally, increased levels of serum IL-4 were positively correlated with Tfh2 cell frequencies in healthy PW. Interestingly, serum P4 levels were positively associated with the frequencies of circulating Tfh2 or Th2 cells but were negatively related to the frequencies of circulating Tfh17 or Th17 cells in healthy PW. Although there were some changes in the other CD4⁺ Th cell frequencies and cytokine levels or other references, significant differences were not found among HC, healthy PW, PW with HBeAg-negative chronic ASCs.

Conclusion

CD4⁺ Th cell subsets played a critical role in the immune microenvironment of PW, and these findings provided potential evidence for why PW with chronic ASCs did not receive antenatal antiviral prophylaxis.

BCL6 is regulated by the MAPK/ELK1 axis and promotes KRAS-driven lung cancer

Mutational activation of KRAS is a common oncogenic event in lung cancer, yet effective therapies are still lacking. Here, we identify B cell lymphoma 6 (BCL6) as a lynchpin in KRAS-driven lung cancer. BCL6 expression was increased upon KRAS activation in lung tumor tissue in mice and was positively correlated with the expression of KRAS-GTP, the active form of KRAS, in various human cancer cell lines. Moreover, BCL6 was highly expressed in human KRAS-mutant lung adenocarcinomas and was associated with poor patient survival. Mechanistically, the MAPK/ERK/ELK1 signaling axis downstream of mutant KRAS directly regulated BCL6 expression. BCL6 maintained the global expression of prereplication complex components; therefore, BCL6 inhibition induced stalling of the replication fork, leading to DNA damage and growth arrest in KRAS-mutant lung cancer cells. Importantly, BCL6-specific knockout in lungs significantly reduced the tumor burden and mortality in the LSL-Kras^G12D/+ lung cancer mouse model. Likewise, pharmacological inhibition of BCL6 significantly impeded the growth of KRAS-mutant lung cancer cells both in vitro and in vivo. In summary, our findings reveal a crucial role of BCL6 in promoting KRAS-addicted lung cancer and suggest BCL6 as a therapeutic target for the treatment of this intractable disease.

Peyer's patch TH17 cells are dispensable for gut IgA responses to oral immunization

T helper 17 (T_H17) cells located at the Peyer's patch (PP) inductive site and at the lamina propria effector site of the intestinal immune system are responsive to both pathogenic and commensal bacteria. Their plasticity to convert into follicular helper T (T_FH) cells has been proposed to be central to gut immunoglobulin A (IgA) responses. Here, we used an IL-17A fate reporter mouse and an MHC-II tetramer to analyze antigen-specific CD4⁺ T cell subsets and isolate them for single-cell RNA sequencing after oral immunization with cholera toxin and ovalbumin. We found a T_FH-dominated response with only rare antigen-specific T_H17 cells (<8%) in the PP. A clonotypic analysis provided little support that clonotypes were shared between T_FH and T_H17 cells, arguing against T_H17 plasticity as a major contributor to T_FH differentiation. Two mouse models of T_H17 deficiency confirmed that gut IgA responses to oral immunization do not require T_H17 cells, with CD4^CreRorc^fl/fl mice exhibiting normal germinal centers in PP and unperturbed total IgA production in the intestine.

T Cell Help in the Autoreactive Germinal Center

The germinal center serves as a site of B cell selection and affinity maturation, critical processes for productive adaptive immunity. In autoimmune disease tolerance is broken in the germinal center reaction, leading to production of autoreactive B cells that may propagate disease. Follicular T cells are crucial regulators of this process, providing signals necessary for B cell survival in the germinal center. Here we review the emerging roles of follicular T cells in the autoreactive germinal center. Recent advances in immunological techniques have allowed study of the gene expression profiles and repertoire of follicular T cells at unprecedented resolution. These studies provide insight into the potential role follicular T cells play in preventing or facilitating germinal center loss of tolerance. Improved understanding of the mechanisms of T cell help in autoreactive germinal centers provides novel therapeutic targets for diseases of germinal center dysfunction.

The oncoprotein BCL6 enables solid tumor cells to evade genotoxic stress

Genotoxic agents remain the mainstay of cancer treatment. Unfortunately, the clinical benefits are often countered by a rapid tumor adaptive response. Here, we report that the oncoprotein B cell lymphoma 6 (BCL6) is a core component that confers solid tumor adaptive resistance to genotoxic stress. Multiple genotoxic agents promoted BCL6 transactivation, which was positively correlated with a weakened therapeutic efficacy and a worse clinical outcome. Mechanistically, we discovered that treatment with the genotoxic agent etoposide led to the transcriptional reprogramming of multiple pro-inflammatory cytokines, among which the interferon-α and interferon-γ responses were substantially enriched in resistant cells. Our results further revealed that the activation of interferon/signal transducer and activator of transcription 1 axis directly upregulated BCL6 expression. The increased expression of BCL6 further repressed the tumor suppressor PTEN and consequently enabled resistant cancer cell survival. Accordingly, targeted inhibition of BCL6 remarkably enhanced etoposide-triggered DNA damage and apoptosis both in vitro and in vivo. Our findings highlight the importance of BCL6 signaling in conquering solid tumor tolerance to genotoxic stress, further establishing a rationale for a combined approach with genotoxic agents and BCL6-targeted therapy.

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

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

Identification of the Association Between Toll-Like Receptors and T-Cell Activation in Takayasu’s Arteritis

To explore the relationships between Toll-like receptors (TLRs) and the activation and differentiation of T-cells in Takayasu’s arteritis (TAK), using real-time fluorescence quantitative polymerase chain reaction, mRNA abundance of 29 target genes in peripheral blood mononuclear cells (PBMCs) were detected from 27 TAK patients and 10 healthy controls. Compared with the healthy control group, the untreated TAK group and the treated TAK group had an increased mRNA level of TLR2 and TLR4. A sample-to-sample matrix revealed that 80% of healthy controls could be separated from the TAK patients. Correlation analysis showed that the inactive-treated TAK group exhibited a unique pattern of inverse correlations between the TLRs gene clusters (including TLR1/2/4/6/8, BCL6, TIGIT, NR4A1, etc) and the gene cluster associated with T-cell activation and differentiation (including TCR, CD28, T-bet, GATA3, FOXP3, CCL5, etc). The dynamic gene co-expression network indicated the TAK groups had more active communication between TLRs and T-cell activation than healthy controls. BCL6, CCL5, FOXP3, GATA3, CD28, T-bet, TIGIT, IκBα, and NR4A1 were likely to have a close functional relation with TLRs at the inactive stage. The co-expression of TLR4 and TLR6 could serve as a biomarker of disease activity in treated TAK (the area under curve/sensitivity/specificity, 0.919/100%/90.9%). The largest gene co-expression cluster of the inactive-treated TAK group was associated with TLR signaling pathways, while the largest gene co-expression cluster of the active-treated TAK group was associated with the activation and differentiation of T-cells. The miRNA sequencing of the plasma exosomes combining miRDB, DIANA-TarBase, and miRTarBase databases suggested that the miR-548 family miR-584, miR-3613, and miR-335 might play an important role in the cross-talk between TLRs and T-cells at the inactive stage. This study found a novel relation between TLRs and T-cell in the pathogenesis of autoimmune diseases, proposed a new concept of TLR-co-expression signature which might distinguish different disease activity of TAK, and highlighted the miRNA of exosomes in TLR signaling pathway in TAK.