Continued Bcl6 expression prevents the transdifferentiation of established Tfh cells into Th1 cells during acute viral infection
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ABSTRACT: By using a temporally-controlled system for the ablation of Bcl6 and Cxcr5 speficially in CD4 T cells, the requirements of both factors for the maintenance of Tfh cells were investigated
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: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.
Project description:Tfh cells are required for T cell help to B cells, and BCL6 is the defining transcription factor of Tfh cells. However, the functions of Bcl6 in Tfh have largely remained unclear. Here we defined the BCL6 cistrome in primary human germinal center Tfh cells to assess mechanisms of BCL6 regulation of CD4 T cells, comparing and contrasting BCL6 function in T and B cells. BCL6 primarily acts as a repressor in Tfh cells, and BCL6 binding was associated with control of Tfh cell migration and repression of alternative cell fates. Interestingly, although some BCL6 bound genes possessed BCL6 DNA binding motifs, many BCL6-bound loci were instead characterized by the presence of DNA motifs for AP1 or STAT. AP1 complexes are key positive downstream mediators of TCR signaling and external stimuli. We show that BCL6 can directly bind AP1, and BCL6 depends on AP1 for recruitment to BCL6 binding sites with AP1 motifs, suggesting that BCL6 subverts AP1 activity. These findings reveal that BCL6 has broad and multifaceted effects on Tfh biology, and provide insight into how this master regulator mediates distinct cell-context dependent phenotypes. Sorted naM-CM-/ve tonsil cells were activated with anti-CD3+CD28 Ab coated beads and transduced with BCL6 or control lentiviral vectors as described. RNA was isolated at day 5 following LV infection and microarrays performed as discussed herein. RNA was isolated with the RNeasy Micro Kit (QIAGEN). The quantity and quality of the RNA were confirmed with a NanoDrop 2000c (Thermo Fisher Scientific) and an Experion Electrophoresis System (Bio-Rad). Samples (20 ng) were amplified with Illumina MessageAmp II aRNA Amplification Kits (Ambion), hybridized to HumanHT-12_V4 BeadChips (Illumina), and quantified with Genome Studio (Illumina). Normalized data (heatmap of blood cells) or raw data (heatmap of tonsil cells and Volcano plot) were analyzed with the GenePattern software suite.
Project description:Tfh cells are required for T cell help to B cells, and BCL6 is the defining transcription factor of Tfh cells. However, the functions of Bcl6 in Tfh have largely remained unclear. Here we defined the BCL6 cistrome in primary human germinal center Tfh cells to assess mechanisms of BCL6 regulation of CD4 T cells, comparing and contrasting BCL6 function in T and B cells. BCL6 primarily acts as a repressor in Tfh cells, and BCL6 binding was associated with control of Tfh cell migration and repression of alternative cell fates. Interestingly, although some BCL6 bound genes possessed BCL6 DNA binding motifs, many BCL6-bound loci were instead characterized by the presence of DNA motifs for AP1 or STAT. AP1 complexes are key positive downstream mediators of TCR signaling and external stimuli. We show that BCL6 can directly bind AP1, and BCL6 depends on AP1 for recruitment to BCL6 binding sites with AP1 motifs, suggesting that BCL6 subverts AP1 activity. These findings reveal that BCL6 has broad and multifaceted effects on Tfh biology, and provide insight into how this master regulator mediates distinct cell-context dependent phenotypes.
Project description:Tfh cells are required for T cell help to B cells, and BCL6 is the defining transcription factor of Tfh cells. However, the functions of Bcl6 in Tfh have largely remained unclear. Here we defined the BCL6 cistrome in primary human germinal center Tfh cells to assess mechanisms of BCL6 regulation of CD4 T cells, comparing and contrasting BCL6 function in T and B cells. BCL6 primarily acts as a repressor in Tfh cells, and BCL6 binding was associated with control of Tfh cell migration, TCR signaling, and repression of alternative cell fates. Interestingly, although some BCL6 bound genes possessed BCL6 DNA binding motifs, many BCL6-bound loci were instead characterized by the presence of DNA motifs for AP1 or STAT. AP1 complexes are key positive downstream mediators of TCR signaling and external stimuli. We show that BCL6 can directly bind AP1, and AP1 and BCL6 co-occupied BCL6 binding sites with AP1 motifs, suggesting that BCL6 subverts AP1 activity. These findings reveal that BCL6 has broad and multifaceted effects on Tfh biology, and provide insight into how this master regulator mediates distinct cell-context dependent phenotypes.
Project description:T follicular helper (Tfh) cells play a pivotal role in germinal center reactions, which requires Bcl6 transcription factor. To analyze their relationships with other effector T cell lineages and their stability in vivo, we developed and analyzed a new Bcl6 reporter mouse alone or together with other lineage reporter systems. Assisted with genome-wide transcriptome analysis, we show substantial plasticity of T cell differentiation in the early phase of immune response. At this stage, CXCR5 appears to be expressed in a Bcl6-independent manner. Once Bcl6 is highly expressed, Tfh cells can persist in vivo and some of them develop into memory cells. Together, our results indicate Bcl6 as a bona fide marker for Tfh polarized program. Three group of samples, with 2 biological replicates within each group and total of 6 samples were analyzed.
Project description:T follicular helper (Tfh) cells play a pivotal role in germinal center reactions, which requires Bcl6 transcription factor. To analyze their relationships with other effector T cell lineages and their stability in vivo, we developed and analyzed a new Bcl6 reporter mouse alone or together with other lineage reporter systems. Assisted with genome-wide transcriptome analysis, we show substantial plasticity of T cell differentiation in the early phase of immune response. At this stage, CXCR5 appears to be expressed in a Bcl6-independent manner. Once Bcl6 is highly expressed, Tfh cells can persist in vivo and some of them develop into memory cells. Together, our results indicate Bcl6 as a bona fide marker for Tfh polarized program.
Project description:We analyzed the transcriptome differences of BCL6-sufficient (CD4-Cre) and -insufficient (CD4-CrexBcl6fl/+) OT-II TFH cells. CD4-CrexBcl6fl/+ or control CD4-Cre OT-II T cells were transferred into CD45.1 Sap-/- mice. At day 3 post NP-OVA immunization, CXCR5hiPD-1hi TFH cells were sort-purified from the draining lymph node and prepared for RNA-seq analysis. Two technical repeats of ~200 cells per sample from each of 3 mice were included. BCL6-insufficient TFH cells differentially expressed many genes; among those downregulated were Stim1 and Plcg1, which code for STIM1 and PLCg1, respectively, that both impinge on calcium signaling downstream of TCR activation. Moreover, KEGG pathway analyses revealed that the calcium signaling-related pathway was generally upregulated in wildtype as compared to BCL6-insufficient TFH cells. These data support the notion that BCL6 control follicular T-B interactions by regulating multiple target genes involved in antigen-triggered calcium signaling in T cells.
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.