Project description:Follicular T helper cells (Tfh) provide critical help to B cells for germinal center (GC) formation. Mutations affecting SLAM-associated Protein (SAP) prevent GC formation due to defective T-B cell interactions, yet effects on Tfh cell differentiation remain unclear. We describe the in vitro differentiation of functionally-competent “Tfh-like” cells that expressed Interleukin-21, Tfh markers, and Bcl6, and rescued GC formation in SAP-deficient hosts better than other T helper (Th) cells. SAP-deficient Tfh-like cells appeared virtually indistinguishable from wildtype, yet failed to support GCs in vivo. Interestingly, both Tfh-like and in vivo-derived Tfh cells could produce effector cytokines in response to polarizing conditions. Moreover, Th1, Th2 and Th17 cells could be reprogrammed to obtain Tfh characteristics. ChIP-Seq analyses revealed positive epigenetic markings on Tbx21, Gata3 and Rorc in Tfh-like and ex vivo Tfh cells, and Bcl6 in other Th cell populations, supporting the concept of plasticity between Tfh and other Th cells. Epigenetic modifications were evaluated in ChIP-Seq studies by profiling histone H3K4 and H3K27 trimethylation marks between Th1, Th2, Th17, Tfh-like, and CXCR5+PD-1+ sorted Tfh-like in vitro generated T helper cell populations and ex vivo derived Tfh cells.
Project description:We found that a number of Tfh cells downmodulated BCL6 protein after their development, and we sought to compare the gene expression between BCL6-hi Tfh cells and BCL6-low Tfh cells. CD4+ T cells were sorted from immunized and non-immunized mice for RNA extraction and hybridization on Affymetrix microarrays. Bcl6yfp/+ OT-II cells were transferred to congenic recipient mice, and immunized with NP-OVA in CFA subcutaneously. Seven or ten days after immunization, cells were collected from draining lymph nodes, and sorted on FACSAria by the expression of CXCR5, PD-1 and BCL6-YFP. Naive CD4+ T cells were CD4+ CD44lo CD62Lhi cells from unimmunized mice.
Project description:Follicular helper T (Tfh) are a subset of CD4+ T helper cells that provide help to germinal center B cells and mediate the development of long-lived humoral immunity. Tfh cells dysregulation is associated with several major autoimmune diseases. Although recent studies showed Tfh cells differentiation is controlled by the transcription factor Bcl6, cytokines and cell-cell signals, limited information is available on the proteome and post-translational modifications (PTM) of proteins in human Tfh cells. In this study, using TMT labeling technique, antibody-based affinity enrichment and high-resolution LC-MS/MS analysis, we investigated quantitative proteome and acetylome in human naive CD4+ T cells and in vitro induced Tfh (iTfh) cells. In total, we identified 802 up-regulated proteins and 598 down-regulated proteins at the threshold of 1.5 folds in iTfh cells compared to naive CD4+ T cells. With the aid of intensive bioinformatics, biological process, cellular compartment, molecular function, KEGG pathway and protein-protein interaction of these differentially expressed proteins were revealed. Moreover, our acetylome data showed that 22 lysine acetylated proteins are up-regulated and 26 lysine acetylated proteins are down-regulated in iTfh cells compared to the naive CD4+ T cells, among which 11 differentially acetylated lysine residues in core histone were identified, indicating proteins acetylation and epigenetic mechanism are involved in regulating Tfh cells differentiation. These data provide a significant resource for studies of Tfh differentiation and normal and perturbed Tfh cell function.
Project description:T follicular helper (Tfh) cells constitute an essential cell type in the induction of antibodies. We report that CD4 T cells lacking Foxo1 almost uniformly became CXCR5int Tfh cells following immunization. Moreover, a Foxo1 loss-of-function complemented an Icos mutation allowing the appearance of Tfh cells along with follicular, class-switched B cells and IgG isotype anti-DNA antibodies. Similarly, FOXO1 deficient Tfh differentiation displayed a substantially reduced dependence on ICOSL. Functional and molecular analyses show that FOXO1 regulates Tfh differentiation through a broad program of gene expression exemplified by positive regulation of Icos and negative regulation of Bcl6. These results demonstrate that a key step in Tfh differentiation is the ICOS-initiated activation of the PI3K-AKT pathway resulting in the inactivation of FOXO1. Performed ChIP-seq analysis to examine the role of foxo1 in the development of Tfh cells
Project description:Follicular helper T (Tfh) cells comprise an important subset of helper T cells; however, their relationship with other helper lineages is incompletely understood. Herein, we show IL-12 acting via signal transducer and activator of transcription 4 (STAT4) induced both Il21 and Bcl6 genes, generating cells with features of both Tfh and Th1 cells. However, STAT4 also induced T-bet. Using ChIP-seq, we defined the genome-wide targets of T-bet and found that it repressed Bcl6 and other markers of Tfh cells, thereby attenuating the nascent Tfh-like phenotype in the late phase of Th1 specification. Finally, Tfh-like T cells were rapidly generated following Toxoplasma gondii infection in mice, but T-bet constrained Tfh cells expansion and consequent germinal center formation and antibody production. Our data argue that Tfh and Th1 share a transitional stage through the signal mediated by STAT4, which promotes both phenotypes. However, T-bet represses Tfh functionalities, promoting full Th1 differentiation. The roles of STAT4 and T-bet to determine T helper cell fate were investigated by comparing DNA binding profiles of STAT4 and T-bet in Th1 conditions. The functional outcome was further evaluated by profiling DNase hypersensitivity sites and histone epigenetic marks between WT and STAT4-deficient or T-bet-deficient T cells in Th1 conditions.
Project description:CD4+ T follicular helper cells (TFH) are critical for the formation and function of B cell responses to infection or immunization, but also play an important role in autoimmunity. The factors that contribute to the differentiation of this helper cell subset are incompletely understood, although several cytokines including IL-6, IL-21 and IL-12 can promote TFH cell formation. Yet, none of these factors, nor their downstream cognate STATs, have emerged as non-redundant, essential drivers of TFH cells. This suggests a model in which multiple factors can contribute to the phenotypic characteristics of TFH cells. As type I interferons (IFNs) are often generated in immune responses, we set out to investigate if these factors are relevant to TFH cell differentiation. Type I IFNs promote Th1 responses, thus one possibility was these factors antagonized TFH-expressed genes. However, we show that type I IFNs (IFN-α/β) induced Bcl6 expression, the master regulator transcription factor for TFH cells, and CXCR5 and PD-1 (encoded by Pdcd1), key surface molecules expressed by TFH cells. In contrast, type I IFNs failed to induce IL-21, the signature cytokine for TFH cells. The induction of Bcl6 was regulated directly by STAT1, which bound to the Bcl6, Cxcr5 and Pdcd1 loci. These data suggest that type I IFNs (IFN-α/β) and STAT1 can contribute to some features of TFH cells but are inadequate in inducing complete programming of this subset. The role of STAT1 in type I interferon treated CD4+ T cells was investigated by Chip-seq of STAT1.
Project description:Follicular T helper cells (Tfh) provide critical help to B cells for germinal center (GC) formation. Mutations affecting SLAM-associated Protein (SAP) prevent GC formation due to defective T-B cell interactions, yet effects on Tfh cell differentiation remain unclear. We describe the in vitro differentiation of functionally-competent “Tfh-like” cells that expressed Interleukin-21, Tfh markers, and Bcl6, and rescued GC formation in SAP-deficient hosts better than other T helper (Th) cells. SAP-deficient Tfh-like cells appeared virtually indistinguishable from wildtype, yet failed to support GCs in vivo. Interestingly, both Tfh-like and in vivo-derived Tfh cells could produce effector cytokines in response to polarizing conditions. Moreover, Th1, Th2 and Th17 cells could be reprogrammed to obtain Tfh characteristics. ChIP-Seq analyses revealed positive epigenetic markings on Tbx21, Gata3 and Rorc in Tfh-like and ex vivo Tfh cells, and Bcl6 in other Th cell populations, supporting the concept of plasticity between Tfh and other Th cells.
Project description:T follicular helper (Tfh) cell is a unique T cell subset specialized in promoting germinal center reactions. Bcl6 has been identified as an obligatory transcription factor in Tfh cells; however, the molecular mechanism underlying Bcl6 function still remains unknown. Here, we combined genome-wide Bcl6 occupancy and transcriptome profiling to systemically analyze Bcl6 targets in Tfh cells. We found that Bcl6 exhibits unique binding preferences in Tfh cells from those in Th9, B cells and macrophage and its binding is closely associated with decrease in 5-hydroxymethylcytosine (5hmC). Importantly, Bcl6 directly binds to the IL-7R/CD127 gene and suppresses its expression. Bcl6 also binds the same sequences recognized by signal transducer and activator of transcription (STAT) 5, downstream of IL-7R. Bcl6 promotes CD127loPDhi Tfh cell differentiation; deletion of the Bcl6 gene in T cells results in enhanced IL-7R-STAT5 signaling and substantial expansion of CD127hiPDlo non-Tfh cells. Our study thus systemically examines Bcl6-controlled regulatory networks and provides novel insights into its biological functions in Tfh cells.
Project description:T follicular helper (TFH) cells are a distinct type of CD4 T cells that are essential for most antibody and B lymphocyte responses. TFH regulation and dysregulation is involved in a range of diseases. Bcl6 is the lineage defining transcription factor of TFH cells and its activity is essential for TFH cell differentiation and function. However, how Bcl6 controls TFH biology has largely remained unclear, at least in part due to intrinsic challenges of connecting repressors to gene upregulation in complex cell types with multiple possible differentiation fates. Multiple competing models were tested here by a series of experimental approaches to determine that Bcl6 exhibits negative autoregulation and controls pleiotropic attributes of TFH differentiation and function (migration, costimulation, inhibitory receptors, and cytokines) via multiple repressor-of-repressor gene circuits.
Project description:T follicular helper (TFH) cells are a distinct type of CD4 T cells that are essential for most antibody and B lymphocyte responses. TFH regulation and dysregulation is involved in a range of diseases. Bcl6 is the lineage defining transcription factor of TFH cells and its activity is essential for TFH cell differentiation and function. However, how Bcl6 controls TFH biology has largely remained unclear, at least in part due to intrinsic challenges of connecting repressors to gene upregulation in complex cell types with multiple possible differentiation fates. Multiple competing models were tested here by a series of experimental approaches to determine that Bcl6 exhibits negative autoregulation and controls pleiotropic attributes of TFH differentiation and function (migration, costimulation, inhibitory receptors, and cytokines) via multiple repressor-of-repressor gene circuits.