Tfh Cell Differentiation Research Articles

149 The promoting effect of SIRT1 on Tfh cell differentiation and its potential role in the pathogenesis of lupus

149 The promoting effect of SIRT1 on Tfh cell differentiation and its potential role in the pathogenesis of lupus

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

Risk prediction of de novo donor-specific antibody (dnDSA) formation is crucial for understanding the long-term prognostic impact of kidney transplantation (KT). Recently, follicular helper T (Tfh) cells, a subtype of CD4+ T cells, have been reported to play an important role in dnDSA formation after solid organ transplantation. Given the growing recognition of the importance of Tfh cells in generating a strong humoral immune response, we examined whether polymorphisms in Tfh cell-related molecules were associated with dnDSA formation after KT. Eighty-three patients who underwent living-donor KT between January 2013 and February 2020 at Hiroshima University Hospital were included in the study. Six Tfh cell-related molecules (BCL6, CXCR5, CXCL13, ICOS, CD40L, and IL21) that are important for Tfh cell differentiation and maturation in secondary lymphoid tissues were investigated. CTLA4, which is important for Tfh-cell activation, was also investigated. Single nucleotide polymorphisms (SNPs) in the genes for these molecules were detected using Taq Man SNP genotyping and evaluated for their association with dnDSA formation after KT. Of the 83 KT recipients, 8 developed dnDSAs during the observation period. No statistically significant differences were observed in the baseline characteristics between patients with and without dnDSA formation, except for donor age. Among the 7 Tfh cell-related molecules, the incidence of dnDSA formation was associated with CXCR5 and CTLA4 SNPs. Furthermore, combining these 2 SNPs enabled more significant stratification of dnDSA formation. Our findings indicate that genetic polymorphisms in Tfh cell-related molecules are predisposing factors for dnDSA formation after KT.

MAIT cells activate dendritic cells to promote TFH cell differentiation and induce humoral immunity

Protective immune responses against respiratory pathogens, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza virus, are initiated by the mucosal immune system. However, most licensed vaccines are administered parenterally and are largely ineffective at inducing mucosal immunity. The development of safe and effective mucosal vaccines has been hampered by the lack of a suitable mucosal adjuvant. In this study we explore a class of adjuvant that harnesses mucosal-associated invariant T (MAIT) cells. We show evidence that intranasal immunization of MAIT cell agonists co-administered withprotein, including the spike receptor binding domain from SARS-CoV-2 virus and hemagglutinin from influenza virus, induce protective humoral immunity and immunoglobulin A production. MAIT cell adjuvant activity is mediated by CD40L-dependent activation of dendritic cells and subsequent priming of T follicular helper cells. In summary, we show that MAIT cells are promising vaccine targets that can be utilized as cellular adjuvants in mucosal vaccines.

Deficient leptin receptor signaling in T cells of human SLE.

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease mainly mediated by IgG autoantibody. While follicular helper T (Tfh) cells are crucial for supporting IgG autoantibody generation in human SLE, underlying mechanisms for Tfh cell mal-differentiation remain unclear. In total, 129 SLE patients and 37 healthy donors were recruited for this study. Circulating leptin was determined by ELISA from patients with SLE and healthy individuals. CD4 T cells isolated from SLE patients and healthy donors were activated with anti-CD3/CD28 beads under cytokine-unbiased conditions in the presence or absence of recombinant leptin protein, followed by detection for Tfh cell differentiation by quantifying intracellular transcription factor Bcl-6 and cytokine IL-21. AMPK activation was assessed by analyzing phosphor-AMPK using phosflow cytometry and immunoblots. Leptin receptor expression was determined using flow cytometry and its overexpression was achieved by transfection with an expression vector. Humanized SLE chimeras were induced by injecting patients' immune cells into immune-deficient NSG mice and used for translational studies. Circulating leptin was elevated in patients with SLE, inversely associated with disease activity. In healthy individuals, leptin efficiently inhibited Tfh cell differentiation through inducing AMPK activation. Meanwhile, leptin receptor deficiency was a feature of CD4 T cells in SLE patients, impairing the inhibitory effect of leptin on the differentiation of Tfh cells. As a result, we observed the coexistence of high circulating leptin and increased Tfh cell frequencies in SLE patients. Accordingly, overexpression of leptin receptor in SLE CD4 T cells abrogated Tfh cell mal-differentiation and IgG anti-dsDNA generation in humanized lupus chimeras. Leptin receptor deficiency blocks the inhibitory effect of leptin on SLE Tfh cell differentiation, serving as a promising therapeutic target for lupus management.

Multidimensional Analysis of Lung Lymph Nodes in a Mouse Model of Allergic Lung Inflammation following and Indeno[1,2,3-cd]pyrene Exposure.

Ambient particulate matter with an aerodynamic diameter of () is suggested to act as an adjuvant for allergen-mediated sensitization and recent evidence suggests the importance of T follicular helper (Tfh) cells in allergic diseases. However, the impact of exposure and its absorbed polycyclic aromatic hydrocarbon (PAHs) on Tfh cells and humoral immunity remains unknown. We aimed to explore the impact of environmental and indeno[1,2,3-cd]pyrene (IP), a prominent PAH, as a model, on Tfh cells and the subsequent pulmonary allergic responses. - or IP-mediated remodeling of cellular composition in lung lymph nodes (LNs) was determined by mass cytometry in a house dust mite (HDM)-induced mouse allergic lung inflammation model. The differentiation and function of Tfh cells in vitro were analyzed by flow cytometry, quantitative reverse transcription polymerase chain reaction, enzyme-linked immunosorbent assay, chromatin immunoprecipitation, immunoprecipitation, and western blot analyses. Mice exposed to during the HDM sensitization period demonstrated immune cell population shifts in lung LNs as compared with those sensitized with HDM alone, with a greater number of differentiated Tfh2 cells, enhanced allergen-induced immunoglobulin E (IgE) response and pulmonary inflammation. Similarly enhanced phenotypes were also found in mice exposed to IP and sensitized with HDM. Further, IP administration was found to induce interleukin-21 (Il21) and Il4 expression and enhance Tfh2 cell differentiation in vitro, a finding which was abrogated in aryl hydrocarbon receptor (AhR)-deficient T cells. Moreover, we showed that IP exposure increased the interaction of AhR and cellular musculoaponeurotic fibrosarcoma (c-Maf) and its occupancy on the Il21 and Il4 promoters in differentiated Tfh2 cells. These findings suggest that the (IP)-AhR-c-Maf axis in Tfh2 cells was important in allergen sensitization and lung inflammation, thus adding a new dimension in the understanding of Tfh2 cell differentiation and function and providing a basis for establishing the environment-disease causal relationship. https://doi.org/10.1289/EHP11580.

Liver X receptor controls follicular helper T cell differentiation via repression of TCF-1

Liver X receptor (LXR) is a critical regulator of cholesterol homeostasis that inhibits T cell receptor (TCR)-induced proliferation by altering intracellular sterol metabolism. However, the mechanisms by which LXR regulates helper T cell subset differentiation remain unclear. Here, we demonstrate that LXR is a crucial negative regulator of follicular helper T (Tfh) cells invivo. Both mixed bone marrow chimera and antigen-specific T cell adoptive cotransfer studies show a specific increase in Tfh cells among LXRβ-deficient CD4+ T cell population in response to immunization and lymphocytic choriomeningitis mammarenavirus (LCMV) infection. Mechanistically, LXRβ-deficient Tfh cells express augmented levels of T cell factor 1 (TCF-1) but comparable levels of Bcl6, CXCR5, and PD-1 in comparison with those of LXRβ-sufficient Tfh cells. Loss of LXRβ confers inactivation of GSK3β induced by either AKT/Extracellular signal-regulated kinase (ERK) activation or Wnt/β-catenin pathway, leading to elevated TCF-1 expression in CD4+ Tcells. Conversely, ligation of LXR represses TCF-1 expression and Tfh cell differentiation in both murine and human CD4+ Tcells. LXR agonist significantly diminishes Tfh cells and the levels of antigen-specific IgG upon immunization. These findings unveil a cell-intrinsic regulatory function of LXR in Tfh cell differentiation via the GSK3β-TCF1 pathway, which may serve as a promising target for pharmacological intervention in Tfh-mediated diseases.

Olfactory Ecto-mesenchymal Stem Cell-derived Exosomes Ameliorate Murine Sjögren's Syndrome via Suppressing Tfh Cell Response.

To investigate the effect of olfactory ecto-mesenchymal stem cell-derived exosomes (OE-MSC-Exos) on T follicular helper (Tfh) cell response and their implication in treating experimental Sjögrens syndrome (ESS). C57BL/6 mice were immunized with salivary glands (SG) proteins to induce ESS mouse model. OE-MSC-Exos were added to the Tfh cell polarization condition, and the proportion of Tfh cells was detected by FCM. The PD-L1 of OE-MSCs was silenced with small interfering RNA to extract siPD-L1-OE-MSC-Exos. We found that transfer of OE-MSC-Exos markedly attenuated disease progression and reduced Tfh cell response in mice with ESS. In culture, OE-MSC-Exos potently inhibited the differentiation of Tfh cells from naïve T cells. Moreover, OE-MSC-Exos expressed high level of the ligand for the programmed cell death protein 1 (PD-L1), knocking down PD-L1 expression in OE-MSC-Exos significantly decreased their capacity to suppress Tfh cell differentiation in vitro. Consistently, transfer of OE-MSC-Exos with PD-L1 knockdown exhibited profoundly diminished therapeutic effect in ESS mice, accompanied with sustained Tfh cell response and high levels of autoantibody production. Our results suggest that OE-MSC-Exos may exert their therapeutic effect in ameliorating ESS progression via suppressing Tfh cell response in a PD-L1-dependent manner.

LncRNA IL21-AS1 interacts with hnRNPU protein to promote IL21 overexpression and aberrant differentiation of Tfh cells in systemic lupus erythematosus.

The aberrant differentiation of T follicular helper (Tfh) cells plays an important role in the pathogenesis of systemic lupus erythematosus (SLE). However, the mechanism of regulating Tfh cells differentiation remains unclear. Long noncoding RNAs (lncRNAs) act as important regulators in the processes of innate and adaptive immune response. Whether lncRNAs are involved in regulating Tfh cell differentiation and autoimmune responses need to be further identified. The characters and functions of human IL21-AS1 and its mouse homologous lncRNA (mIl21-AS) were investigated by a series of biochemical assays and cell transfection assay. mIl21-AS1 regulating humoral immune response in vivo was explored by keyhole limpet haemocyanin (KLH) and chronic graft versus host disease (cGVHD) model. Human IL21-AS1 and its mouse homologous lncRNA (mIl21-AS) were identified and cloned. We uncovered that IL21-AS1 was highly expressed in CD4+ T cells of SLE patients and Tfh cells, which promoted differentiation of Tfh cells. Mechanistically, IL21-AS1 bound heterogeneous nuclear ribonucleoprotein U and recruited acetyltransferases CREB-binding protein to the promoter of IL21, leading to the transcriptional activation of IL21 and Tfh cells differentiation through increasing Histone H3 acetylation level on IL21 promoter. Moreover, Tfh proportion and antibodies production were significantly increased in mIl21-AS knock-in mice immunized with KLH. mIl21-AS1 overexpression also exacerbated the lupus-like phenotype in cGVHD mice model. Our results demonstrate that IL21-AS1 activates IL21 transcription via epigenetic mechanism to promote germinal centre response, adding insight into the molecular regulation of autoimmune pathogenesis and providing a novel target for SLE treatment.

Regulation of follicular T helper cell differentiation in antitumor immunity.

Follicular T helper (Tfh) cells are a subset of CD4+ T cells that play an important role in the formation of germinal centers and the maturation and differentiation of affinity-matured B cells. Recent studies have demonstrated important functions of Tfh cells in tertiary lymphoid structures of tumors, revealing great potential of Tfh cells in tumor immunity. However, Tfh development is incompletely understood. The differentiation of Tfh cells is a complex, multistage process regulated at the DNA, RNA and protein levels. This review just summarizes current research on the molecular mechanisms of Tfh cell differentiation to better understand the role of Tfh cells in antitumor immunity.

The NPM1-TYK2 Chimeric Fusion Promotes Activation of STAT Family Signaling, Skewing Towards Tfh Functional Subset Differentiation and Mature T-Cell Lymphomagenesis

Introduction Peripheral T cell lymphomas are heterogeneous neoplasms of post thymic T cells with distinct clinical, pathological and genetic characteristics. We previously identified the NPM1-TYK2 fusion in patients with CD30+ lymphoproliferative disorders, including 15% of primary cutaneous ALK− anaplastic large cell lymphoma. The oncogenicity of NPM1-TYK2 and its effect on T cell differentiation, the molecular mechanisms and signaling pathways through which it drives lymphomagenesis invivo remain unknown. Methods To investigate the effect of NPM1-TYK2 on oncogenesis and T cell differentiation, we established a conditional transgenic model (CD4-NPM1-TYK2). To investigate cooperativity with Trp53, CD4-NPM1-TYK2 mice were crossed with Trp53 floxed mice to generate CD4ΔTrp53-NPM1-TYK2 mice with T cell-specific concomitant heterozygous loss of Trp53. Mice (n = 15 per genotype) were monitored over time for tumor development. Hematopoietic organs were harvested and subjected to histolopathological and immunophenotypic analysis. Serum cytokine and immunoglobulin profiles were analyzed by Luminex multiplex immunoassays. The effects of NPM1-TYK2 on the physiological function of T cells were examined by growth curves and cell cycle analysis using anti-CD3/CD28 stimulated CD4+ T cells from CD4-NPM1-TYK2 mice in vitro. To evaluate the signaling sequences of NPM1-TYK2 expression, unbiased mass spectrometry (MS)-driven phosphoproteomics was performed. The pharmacological effect of Deucravacitinib, an allosteric TYK2 inhibitor, on NPM1-TYK2+ murine T cells and human T cell lymphoma-derived cells were examined. ResultsCD4-NPM1-TYK2 mice showed significant splenomegaly (n = 20; 104.8 mg vs 86.5 mg) and developed lymphoma with hepatomegaly due to atypical neoplastic infiltrates. Notably, CD4ΔTrp53-NPM1-TYK2 mice (n = 5; 15.4 months) exhibited an earlier onset of lymphoma compared to CD4-NPM1-TYK2 mice (n = 4; 19.8 months). Immunophenotypic characterization of CD4+ T cells from the spleen of CD4-NPM1-TYK2 mice (n = 7) revealed an increase in effector T cells (CD44+/CD62L−, 51.5% vs 39.4%) and a decrease in naïve T cells (CD44−/CD62L+, 32.9% vs 44.8%), suggesting NPM1-TYK2 promotes effector T cell differentiation in vivo. Among all T helper cell subtypes, increased Tfh cells was observed in CD4-NPM1-TYK2 mice (n = 8; ICOS+/CXCR5+/PD1+/BCL6+, 27.4% vs 15.5%), indicating NPM1-TYK2 mediates the commitment of Tfh cell skewing in vivo. Serum cytokine profile of CD4-NPM1-TYK2 mice also showed elevated Tfh-related cytokines (n = 4; IL-1β, IL-4, IL-6, IL-10, IL-12). Tfh cells are crucial for the formation of germinal center (GC) B cells and their differentiation into plasma cells. Elevated expansion of GC B cells (n = 5; CD95+/PNA+, 4.8% vs 3.8%) was also observed. Increased plasma cells (B220−/CD138+, 9.1% vs 3.8%) and elevated immunoglobulins (n = 6; IgA, IgG2b) in the serum corroborated observed lymphoplasmacytic cells in the histology of CD4-NPM1-TYK2 mice. Among MS-identified phosphoproteins demonstrating the YX(2-5)L motif of JAK family kinase substrates, we observed elevated levels of tyrosine phosphopeptides implicating STAT1/3/5 activation. Western blotting of CD4+ T cells from CD4-NPM1-TYK2 mice revealed hyperphosphorylation of STAT1/3/5. NPM1-TYK2+ T cells (n = 3 per genotype) were hyperreactive to stimulation in vitro, displaying increased activated cells (CD69+/CD25+, 83/80% vs 76/73%). The growth curves of NPM1-TYK2+ T cells showed increased growth (2.6-fold) with more proliferating cells in the S phase of cell cycle (31% vs 25%) whilst control CD4+ T cells stopped proliferating 10 days post-stimulation. Intriguingly, the NPM1-TYK2-mediated growth-promoting effect was attenuated by Deucravacitinib. Conclusion Conditional transgenic expression of NPM1-TYK2 in mature T-cell lineage promotes Tfh cell differentiation accompanied by intense GC B cell and plasma cell expansion, and hepatosplenomegaly with disseminated lymphoma accelerated by concomitant heterozygous ablation of Trp53in vivo. The biologic effects of NPM1-TYK2 expression are propagated through STAT1/3/5 activation. These data provide novel insights on the signaling, cellular immunologic and oncogenic consequences of NPM1-TYK2 expression in CD4+ T cells. Our studies implicate NPM1-TYK2 as a de facto oncogene in vivo and provides a valuable pre-clinical model for precision medicine. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

The hippo kinase MST1 negatively regulates the differentiation of follicular helper T cells.

Follicular helper T (TFH ) cells are essential for inducing germinal centre (GC) reactions to mediate humoral adaptive immunity and antiviral effects, but the mechanisms of TFH cell differentiation remain unclear. Here, we found that the hippo kinase MST1 is critical for TFH cell differentiation, GC formation, and antibody production under steady-state conditions and viral infection. MST1 deficiency intrinsically enhanced TFH cell differentiation and GC reactions in vivo and in vitro. Mechanistically, mTOR and HIF1α signalling is involved in glucose metabolism and increased glycolysis and decreased OXPHOS, which are critically required for MST1 deficiency-directed TFH cell differentiation. Moreover, upregulated Foxo3 expression is critically responsible for TFH cell differentiation induced by Mst1-/- . Thus, our findings identify a previously unrecognized relationship between hippo kinase MST1 signalling and mTOR-HIF1α-metabolic reprogramming coupled with Foxo3 signalling in reprogramming TFH cell differentiation.

Identification and Characterization of Antigenic Properties of Schistosoma japonicum Heat Shock Protein 90α Derived Peptides.

It is known that schistosome-derived antigens induce innate and adaptive immune responses that are essential for the formation of hepatic immunopathology. Here, we screened and synthesized four peptides derived from Schistosoma japonicum (S. japonicum) heat shock protein 90α (Sjp90α-1, -2, -3, and -4), which is widely expressed in adults and eggs of the genus S. japonicum and induces remarkable immune reactions. To define the antigenicity of these peptides, we stimulated splenocytes with peptides, and the results showed that only the Sjp90α-1 peptide could predominately induce the activation of dendritic cells (DCs) and macrophages as well as alter the proportion of follicular helper T (Tfh) cells. Next, CD4+ T cells were purified and cocultured with mouse bone-marrow-derived DCs (BMDCs) with or without Sjp90α-1 peptide stimulation in vitro, and the results showed that Sjp90α-1-stimulated BMDCs can significantly induce CD4+ T-cell differentiation into Tfh cells, while the direct stimulation of CD4+ T cells with Sjp90α-1 did not induce Tfh cells, indicating that the Sjp90α-1 peptide promotes Tfh cell differentiation depending on the presence of DCs. Furthermore, we selected and prepared an Sjp90α-1-peptide-based antibody and illustrated that it has excellent reactivity with the immunizing peptide and detects a single band of 29 kDa corresponding to the Sjp90α protein. The immunolocalization results showed that the protein recognized by this Sjp90α-1-peptide-based antibody is present in the mature eggs and the tegument of adults, implying that the parasite-derived peptide has a potential interaction with the host immune system. Finally, we evaluated antipeptide IgG antibodies and revealed a significantly higher level of anti-Sjp90α-1 peptide IgG antibodies in mice 3 weeks after S. japonicum infection. In conclusion, we illustrate that these synthetic peptides warrant further investigation by evaluating their antigen-specific immune response and their ability to efficiently induce Tfh cells. Moreover, they may constitute a potentially helpful method for the laboratory diagnosis of schistosomiasis japonica.

Diabetes mellitus aggravates humoral immune response in myasthenia gravis by promoting differentiation and activation of circulating Tfh cells

Myasthenia gravis (MG) is a T-cell-dependent, antibody-mediated autoimmune disease. Diabetes mellitus (DM) is a chronic metabolic disease characterized by hyperglycemia and emerging evidence indicates its profound impacts on the immune homeostasis. Previous studies and our data showed DM might serve as an independent risk factor of MG, yet the underlying immune and molecular mechanisms remain to be addressed. Our study observed that circulating Tfh (cTfh) cells were increased in MG patients with DM and expressed a high level of ICOS. Besides, positive correlations between activated cTfh cells and plasmablasts were documented. Further studies demonstrated hyperglycemia promoted the differentiation and activation of Tfh cells which, in turn, caused abnormal plasmablasts differentiation and antibody secretion through the mTOR signaling pathway. These results indicated DM might aggravate the aberrant humoral immunity in MG patients by augmenting Tfh cells differentiation and function and tight glycemic control might be beneficial for MG patients with DM.

Tonsillar Microbiome-Derived Lantibiotics Induce Structural Changes of IL-6 and IL-21 Receptors and Modulate Host Immunity.

Emerging evidence emphasizes the functional impacts of host microbiome on the etiopathogenesis of autoimmune diseases, including rheumatoid arthritis (RA). However, there are limited mechanistic insights into the contribution of microbial biomolecules especially microbial peptides toward modulating immune homeostasis. Here, by mining the metagenomics data of tonsillar microbiome, a deficiency of the encoding genes of lantibiotic peptides salivaricins in RA patients is identified, which shows strong correlation with circulating immune cells. Evidence is provided that the salivaricins exert immunomodulatory effects in inhibiting T follicular helper (Tfh) cell differentiation and interleukin‐21 (IL‐21) production. Mechanically, salivaricins directly bind to and induce conformational changes of IL‐6 and IL‐21 receptors, thereby inhibiting the bindings of IL‐6 and IL‐21 to their receptors and suppressing the downstream signaling pathway. Finally, salivaricin administration exerts both prophylactic and therapeutic effects against experimental arthritis in a murine model of RA. Together, these results provide a mechanism link of microbial peptides‐mediated immunomodulation.

Exploring the mechanism of berberine-mediated Tfh cell immunosuppression

BackgroundOur previous research revealed a novel function of berberine (BBR), a clinically relevant plant-derived alkaloid, as a suppressor of follicular T helper (Tfh) cell proliferation in secondary lymphoid organs of BBR-treated mice that underwent immunization for collagen-induced arthritis (CIA) in DBA1/J mice. Due to the importance of Tfh cell and B cell interactions in the generation of T cell-dependent humoral responses, the suppression of Tfh cell activity may have implications for the general safety of BBR as a prophylactic dietary supplement, and its potential use in antibody-driven autoimmune and hypersensitivity disorders. PurposeThis research aims to characterize BBR's impact on the activation, differentiation, and proliferation of Tfh cells by examining the expression of key extracellular signaling molecules, as well as the activity of intracellular signaling molecules involved in the Ca2+-calcineurin-NFAT pathway and STAT3 phosphorylation, following activation. Study designIn vitro experimental study using primary tissues. MethodsTo explore the direct effects of BBR on the proliferation and differentiation of Tfh cells, isolated naïve CD4+ T cells (>95% pure) were activated and differentiated into pre- Tfh cells in the presence or absence of BBR. The resulting Tfh cell populations and the expression of the key extracellular molecules CXCR5, ICOS, and PD-1 were measured. In addition, we examined the impact of BBR treatment on the activity of key intracellular signaling molecules involved in Tfh cell activation and differentiation following TCR ligation and/or CD28 signaling (p-ZAP-70, p-Lck, p-PLCγ1, NFATc1 and intracellular calcium, Ca2+, concentrations), as well as IL-6 signaling (p-STAT3). ResultsTreatment with BBR significantly reduced the expression of both CXCR5 (p < 0.01) and ICOS (p < 0.005), but not PD-1, and reduced the percentage of Tfh cells within the total CD4+ T cell population. BBR treatment also led to a reduction in intracellular Ca2+ flux, activation of p-STAT3, and IL-21 production. ConclusionOur observations provide insight into the mechanism of BBR-mediated Tfh cell suppression and suggest that BBR treatment can directly inhibit Tfh cell activity, perhaps through interfering with cytokine receptor or downstream signaling.

The Differentiation and Maintenance of SARS-CoV-2-Specific Follicular Helper T Cells.

Upon acute viral infection, virus-specific CD4+ T cells differentiate into either TH1 cells or follicular helper T (TFH) cells. The molecular pathways governing such bimodal cell fate commitment remain elusive. Additionally, effector virus-specific TFH cells further differentiate into corresponding memory population, which confer long-term protection against re-infection of same viruses by providing immediate help to virus-specific memory B cells. Currently, the molecular mechanisms underlying the long-term maintenance of memory TFH cells are largely unknown. In this review, we discuss current understanding of early differentiation of virus-specific effector TFH cells and long-term maintenance of virus-specific memory TFH cells in mouse models of viral infection and patients of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

TOX promotes follicular helper T cell differentiation in patients with primary Sjögren's syndrome.

Whether naive CD4+ T cells are dysregulated and associated with the overactivation of CD4+ T cells in primary SS (pSS) remains unclear. We aimed to explore the role and underlying mechanism of naive CD4+ T cells in pSS. We examined the activation, proliferation and differentiation of naive CD4+ T cells from pSS patients and healthy controls. Differentially expressed genes were identified using RNA sequencing, and were overexpressed or silenced to determine the gene regulating follicular helper T (Tfh) cells. Assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) with chromatin immunoprecipitation with high-throughput sequencing (ChIP-seq) was performed to explore the epigenetic mechanism. Naive CD4+ T cells were treated with pSS-related cytokines to explore the upstream signalling pathway. pSS naive CD4+ T cells had higher potentials of activation, proliferation and differentiation towards Tfh cells. Thymocyte selection-associated high mobility group box protein (TOX) was upregulated in pSS naive CD4+ T cells and promoted T cell activation and Tfh cell polarization. TOX silencing in pSS naive CD4+ T cells downregulated B cell lymphoma 6 (BCL6) expression and altered levels of multiple Tfh-associated genes. ChIP-seq analysis implied that TOX bound to the BCL6 locus, where there were accessible regions found by ATAC-seq. IFN-α induced TOX overexpression, which was attenuated by Janus kinase (JAK) and signal transducer and activator of transcription 1 (STAT1) inhibitors. Our data suggest that TOX in pSS naive CD4+ T cells is upregulated, which facilitates Tfh cell differentiation. Mechanistically, IFN-α induces TOX overexpression in naive CD4+ T cells through JAK-STAT1 signalling and TOX regulates BCL6 expression. Therefore, IFN-α-JAK-STAT1 signalling and TOX might be potential therapeutic targets in pSS.

Astragaloside IV ameliorates pulmonary vascular remodeling in hypoxia-induced pulmonary hypertension by restraining the T follicular helper cell response and expanding T follicular regulatory cell response

BackgroundPulmonary hypertension (PH) is a progressive disorder lacking a validated and effective therapy which characterized by elevated pulmonary arterial pressure, vascular remodeling and eventual death. FDA approved sildenafil is being used as a first-line drug for PH, however, neither survival rates nor quality of life have been improved because of side effects and patient noncompliance. Thus, the exploration of novel therapeutic drugs is urgently needed. Astragaloside IV (ASIV) exhibits a protective effect on HPH, but its mechanisms of action is unclear. HypothesisCD4+T cell subsets, Tfh and Tfr cells, may contribute to the development of chronic hypoxia-induced PH (HPH). We hypothesized that ASIV could effectively ameliorates pulmonary vascular remodeling of HPH by restraining the Tfh cell response and expanding Tfr cell response. Methods and resultsHPH mice model was established by exposure to chronic hypoxia for 21 days. Mice were randomly assigned to six groups: NaCl group, model group, SN group (100 mg/kg of sildenafil), low-dose group (20 mg/kg of ASIV), medium-dose group (40 mg/kg of ASIV) and high-dose group (80 mg/kg of ASIV). Primary culture and identification of distal pulmonary artery smooth muscle cells (PASMCs) in mice were established. Here, we demonstrated that ASIV treatment could significantly ameliorate the increase of mean PAP, RV/ (LV+S) ratio and PAMT in HPH mice. ASIV inhibited Tfh cell differentiation and IL-21 production, but promoted Tfr cell differentiation and TGF-β, IL-10 production. Chronic hypoxia promoted germinal center B cell responses, which inhibited by ASIV. ASIV regulated Tfh and Tfr cell differentiation by inhibiting the phosphorylation of mTOR signaling pathway, and the effect of ASIV-H was better than that observed in the SN group. ASIV inhibited the proliferation, migration and adhesion of PASMCs in vitro. Moreover, ASIV significantly downregulated the protein level of RhoA and upregulated the protein level of p27 in PASMCs under hypoxic condition. ConclusionCollectively, ASIV may regulate Tfh and Tfr cell responses to subsequently repress pulmonary vascular remodeling and hypoxic pulmonary hypertension.

The Aryl Hydrocarbon Receptor Modulates T Follicular Helper Cell Responses to Influenza Virus Infection in Mice.

T follicular helper (Tfh) cells support Ab responses and are a critical component of adaptive immune responses to respiratory viral infections. Tfh cells are regulated by a network of signaling pathways that are controlled, in part, by transcription factors. The aryl hydrocarbon receptor (AHR) is an environment-sensing transcription factor that modulates many aspects of adaptive immunity by binding a range of small molecules. However, the contribution of AHR signaling to Tfh cell differentiation and function is not known. In this article, we report that AHR activation by three different agonists reduced the frequency of Tfh cells during primary infection of C57BL/6 mice with influenza A virus (IAV). Further, using the high-affinity and AHR-specific agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin, we show that AHR activation reduced Tfh cell differentiation and T cell-dependent B cell responses. Using conditional AHR knockout mice, we demonstrated that alterations of Tfh cells and T cell-dependent B cell responses after AHR activation required the AHR in T cells. AHR activation reduced the number of T follicular regulatory (Tfr) cells; however, the ratio of Tfr to Tfh cells was amplified. These alterations to Tfh and Tfr cells during IAV infection corresponded with differences in expression of BCL6 and FOXP3 in CD4+ T cells and required the AHR to have a functional DNA-binding domain. Overall, these findings support that the AHR modulates Tfh cells during viral infection, which has broad-reaching consequences for understanding how environmental factors contribute to variation in immune defenses against infectious pathogens, such as influenza and severe acute respiratory syndrome coronavirus.

Metabolic regulation of follicular helper T cell differentiation in a mouse model of lupus

Follicular helper T (TFH) cells are expanded in systemic lupus erythematosus (SLE), where they are required for production of high affinity autoantibodies. A better understanding of the mechanisms that regulate the differentiation of TFH cells is critical. Naïve T cells from lupus-prone B6.NZM2410.Sle1.Sle2.Sle3 (TC) mice showed an intrinsic higher capacity to differentiate into TFH cells. Metabolic reprogramming is a vital regulatory mechanism for T cell differentiation, but how metabolic pathways contribute to TFH cell expansion in SLE remains elusive. Here we show that glycolysis, mTOR signaling, FAO, and the activity of complex V of the electron transport chain support TFH lineage commitment. Blocking complex I uniquely decreased the expansion of TFH cells from lupus-prone mice, and inhibition of some pathways had a greater effect in lupus-prone than control TFH cells. However, blocking glutaminolysis, complex III and ADP/ATP translocase did not affect TFH cell expansion. Together, our results identified novel intrinsic metabolic requirements for TFH cell differentiation, and further defined the differential metabolic pathways that support the expansion of TFH cells in lupus-prone mice. Together, our data indicates the crucial but distinct roles for metabolic pathways in TFH cell differentiation and provide a comprehensive experimental basis for fully understanding the precise roles of distant metabolic signaling in regulating the TFH cell differentiation.