Project description:Differentiation of B cells into antibody secreting cells (ASCs), plasmablasts and plasma cells, is regulated by a network of transcription factors. Within this network factors including PAX5 and BCL6 prevent ASC differentiation and maintain the B cell phenotype whereas BLIMP-1 and high IRF4 expression promote plasmacytic differentiation. BLIMP-1 is thought to induce immunoglobulin secretion. While IRF4 is needed for the survival of ASCs, its role in the regulation of antibody secretion has been controversial. BCL6-deficient DT40 B cell line has upregulated BLIMP-1 expression and secrete antibodies. In order to study the role of IRF4 in regulation of antibody secretion we have created a double knockout (DKO) DT40 B cell line deficient in both IRF4 and BCL6. This DKO cell line did not upregulate PRDM1 (the gene encoding for BLIMP-1) expression or secrete IgM. Even enforced BLIMP-1 expression in DKO cells or IRF4-deficient cells could not induce IgM secretion while it did in WT cells. However, enforced IRF4 expression in DKO cells induced strong IgM secretion. Our findings support a model where IRF4 expression in addition to BLIMP-1 expression is required to induce antibody secretion.
Project description:Transcriptional regulation of cell fate decisions in the immune system endows cells with specialized function; an iterative process that adapts to the changing landscape of infections. As coordinators of the immune system, T helper cells of the CD4+ lineage possess the ability to differentiate into an array of functional cell states in order to guide the response towards antibody production via the formation of T follicular helper (Tfh) cells or inflammation by the generation of T effector (Teff) cells. Tfh–Teff cell fate choice is mediated by the BCL6–Blimp-1 counter-antagonistic gene regulatory module, polarizing Tfh and Teff cells, respectively. A key question is how T helper cells establish and negotiate BCL6–Blimp-1 counter antagonism to control the output of Tfh and Teff cells. We show that the T cell receptor (TCR)-signal induced transcription factor, IRF4, is necessary for the generation of both BCL6-expressing Tfh cells and Blimp-1-expressing Teff cells. Importantly, we show that increasing TCR signal strength augments the amounts of IRF4 expressed as well as Teff cell fate trajectories that occur at the expense of Tfh cells. Using an orthogonal genetic system, based on a tet-inducible allele of Irf4, we demonstrate that increasing IRF4 expression during priming redirected Tfh cell fate choices towards those of Teff. Importantly, promotion of Teff cell fate trajectories by increased IRF4 expression occurred independently of IL-2 signals. At the molecular level, we link greater IRF4 abundance with its recruitment to low affinity DNA binding sites embedded within regulatory elements affiliated with the Teff gene program, including Blimp-1. Together, these results demonstrate that the Irf4 locus functions as the “reader” of TCR signal strength, in turn, the concentration dependent activity of the IRF4 transcription factor “writes” T helper cell fate choice.
Project description:The goal of this study was to profile Blimp1 binding in E18.5 small intestine using a Blimp-1-eGFP knock-in allele, and to compare Blimp-1-eGFP genomic binding with Irf-1 genomic binding in normal small intestine. Changes in Irf-1 binding between wild type and Prdm1/Blimp-1 mutant small intestine were also assessed. ChIP-seq was performed for Blimp-1-eGFP in duplicate in E18.5 small intestine expressing the fusion protein using anti-GFP antibody. As a negative control a single anti-GFP ChIP was also performed in wild type small intestine. ChIP-seq for Irf-1 was performed in duplicate in both wild type and Prdm1/Blimp-1 mutant E18.5 small intestine using an anti-Irf-1 antibody. Duplicate IgG ChIP control in wild types was performed as a negative control. All samples had an associated input chromatin sample sequenced.
Project description:This is a mathematical mechanistic immunobiochemical model that incorporates T cell pathways that control programmed cell death protein 1 (PD-1) expression. A core component of the model is a kinetic motif, termed a PD-1 Double Incoherent Feed-Forward Loop (DIFFL), which reflects known interactions between IRF4, Blimp-1, and Bcl-6.
Project description:Blimp-1 regulates the overall accumulation of virus-specific CD8+ T cells during acute viral infections. Increased proliferation and survival of Blimp-1-deficient CD8+ T cells is promoted by persistent cytokine responsiveness, resulting from sustained expression of CD25 and CD27. Knockdown of these genes reduced the Blimp-1-deficient CD8+ T cell response. Genome-wide ChIP-sequencing analysis identified CD25 and CD27 genes as direct targets of Blimp-1. At the peak of the anti-viral response, but not earlier, Blimp-1 recruited the histone modifying enzymes G9a and HDAC2 to the Il2ra and Cd27 loci, thereby repressing expression of these genes. In the absence of Blimp-1, the Il2ra and Cd27 genes exhibited enhanced histone H3-acetylation and reduced histone H3K9-trimethylation. These data elucidate a central mechanism by which Blimp-1 acts as an epigenetic regulator, enhancing the numbers of short-lived effector cells while suppressing the development of memory precursor CD8+ T cells. NaM-CM-/ve CD8+ T cells from OT-I TCR transgenic Rag1-/- mice were stimulated with anti-CD3 and anti-CD28 for three days in vitro, in the presence of IL-2 to up-regulate Blimp-1 protein. Genome-wide mapping of Blimp-1 binding in mouse CD8+ T cells was conducted.
Project description:The transcription factor BATF is required for Th17 and TFH differentiation. Here, we show that BATF also has a fundamental role in regulating effector CD8+ T cell differentiation. BATF-deficient CD8+ T cells show profound defects in effector expansion and undergo proliferative and metabolic catastrophe early after antigen encounter. BATF, together with IRF4 and Jun proteins, binds to and promotes early expression of genes encoding lineage-specific transcription-factors (T-bet and Blimp-1) and cytokine receptors, while paradoxically repressing genes encoding effector molecules (IFNg and granzyme B). Thus, BATF amplifies TCR-dependent transcription factor expression and augments inflammatory signal propagation but restrains effector gene expression. This checkpoint prevents irreversible commitment to an effector fate until a critical threshold of downstream transcriptional activity has been achieved. This is an examination of 5 different transcription factors (TFs) with 5 different histone modifications in effector CD8+ T cells. Two of the TFs (BATF and IRF4) and the histone modifications were replicated. Appropriate control sequence files for ChIP input, IgG ChIP, and Total H3 are also included.
Project description:Blimp-1 regulates the overall accumulation of virus-specific CD8+ T cells during acute viral infections. Increased proliferation and survival of Blimp-1-deficient CD8+ T cells is promoted by persistent cytokine responsiveness, resulting from sustained expression of CD25 and CD27. Knockdown of these genes reduced the Blimp-1-deficient CD8+ T cell response. Genome-wide ChIP-sequencing analysis identified CD25 and CD27 genes as direct targets of Blimp-1. At the peak of the anti-viral response, but not earlier, Blimp-1 recruited the histone modifying enzymes G9a and HDAC2 to the Il2ra and Cd27 loci, thereby repressing expression of these genes. In the absence of Blimp-1, the Il2ra and Cd27 genes exhibited enhanced histone H3-acetylation and reduced histone H3K9-trimethylation. These data elucidate a central mechanism by which Blimp-1 acts as an epigenetic regulator, enhancing the numbers of short-lived effector cells while suppressing the development of memory precursor CD8+ T cells.
Project description:Background & Aims: The precise mechanism underlying the attenuation of the antigen-specific B cell response induced by therapeutic vaccination during chronic HBV infection remains unclear. The development of vaccines or strategies targeting this impediment through rational design could potentially result in significant advancements in the treatment of chronic hepatitis B. Methods: A mouse model with a knock-in of a B cell receptor specific to the hepatitis B virus surface antigen was generated under the name E6F6-B. This model was utilized to investigate the temporal and spatial patterns of humoral responses induced by therapeutic vaccination in the presence of persistent antigen stimulation. Through the use of multiple transcriptome sequencing techniques, the differentiation trajectory of HBsAg-specific B cells post therapeutic vaccination during chronic hepatitis B infection was elucidated. Results: In light of the E6F6-B transfer model, a significant reduction in antibody secreting cells were observed two weeks after vaccination. Additionally, an atypical pre-plasma cell population (BLIMP-1+ IRF4+ CD40- CD138-) was identified as a consequence of persistent BCR signaling in the absence of CD40 co-stimulation. A therapeutic antibody-induced suppression of BCR signaling revitalized the HBsAg-specific B cell response.
Project description:Background & Aims: The precise mechanism underlying the attenuation of the antigen-specific B cell response induced by therapeutic vaccination during chronic HBV infection remains unclear. The development of vaccines or strategies targeting this impediment through rational design could potentially result in significant advancements in the treatment of chronic hepatitis B. Methods: A mouse model with a knock-in of a B cell receptor specific to the hepatitis B virus surface antigen was generated under the name E6F6-B. This model was utilized to investigate the temporal and spatial patterns of humoral responses induced by therapeutic vaccination in the presence of persistent antigen stimulation. Through the use of multiple transcriptome sequencing techniques, the differentiation trajectory of HBsAg-specific B cells post therapeutic vaccination during chronic hepatitis B infection was elucidated. Results: In light of the E6F6-B transfer model, a significant reduction in antibody secreting cells were observed two weeks after vaccination. Additionally, an atypical pre-plasma cell population (BLIMP-1+ IRF4+ CD40- CD138-) was identified as a consequence of persistent BCR signaling in the absence of CD40 co-stimulation. A therapeutic antibody-induced suppression of BCR signaling revitalized the HBsAg-specific B cell response.