Project description:Upon antigen recognition B cells undertake a bifurcated response in which some cells rapidly differentiate into plasmablasts while others undergo affinity maturation in germinal centers (GC). We uncover a double negative feedback loop between interferon regulatory factors IRF4 and IRF8, which regulates the initial bifurcation of activated B cells as well as the GC response. IRF8 dampens BCR signaling, facilitates antigen specific interaction with helper T cells, and promotes selection of high affinity clones while antagonizing IRF4 driven plasmablast differentiation. Genomic analysis reveals concentration dependent action of IRF4 and IRF8 in regulating distinctive gene expression programs. Stochastic modeling suggests that the double negative feedback is sufficient to initiate bifurcating B cell developmental trajectories. Naïve B cells were isolated from Irf8+/+ (wild type, WT) mice spleen and activated in vitro with 10μg/ml LPS (Sigma). CD138hi IgMhi (IRF4hi*) cells and CD138lo IgMlo (IRF8hi*) cells were sorted by flow cytometry at 72 hours. Total RNA was prepared by using Rneasy Mini kit (Qiagen) and sequenced with Illumina HiSeq2500. Alignment was performed with Taphat2, and transcript abundance quantification using Cuffdiff function from Cufflinks. GC B cells were sorted from CD19cre/+ Irf8+/+ (Ctrl) or CD19cre/+ Irf8flox/flox (Irf8 cKO) mice on dpi 13 post NP-KLH immunization. Total RNA was prepared by using Rneasy Mini kit (Qiagen) and amplified with with Ovation RNA-Seq System v2 (NuGEN). The data were analyzed by Wardrobe. More details are provided in the manuscript.
Project description:Upon antigen recognition B cells undertake a bifurcated response in which some cells rapidly differentiate into plasmablasts while others undergo affinity maturation in germinal centers (GC). We uncover a double negative feedback loop between interferon regulatory factors IRF4 and IRF8, which regulates the initial bifurcation of activated B cells as well as the GC response. IRF8 dampens BCR signaling, facilitates antigen specific interaction with helper T cells, and promotes selection of high affinity clones while antagonizing IRF4 driven plasmablast differentiation. Genomic analysis reveals concentration dependent action of IRF4 and IRF8 in regulating distinctive gene expression programs. Stochastic modeling suggests that the double negative feedback is sufficient to initiate bifurcating B cell developmental trajectories. Naïve B cells were isolated from wild type (WT) mice spleen and activated in vitro with 10μg/ml LPS (Sigma). ChIP was performed by using anti-IRF4, -IRF8 antibodies (Santa Cruz Biotech). For massively parallel sequencing, 10-20 μg of chromatin fragments from indicated samples were immunoprecipitated by using anti-IRF-4 and anti-IRF8 antibodies, and DNA libraries were prepared with Illumina Kit. DNA was sequenced by using the Illumina HiSeq2500. Reads were aligned to the mouse genome (mm9) by using Taphat2 and peak calling were performed by homer 2. GC B cells were sorted from WT mice on dpi 13 post NP-KLH immunization. Cells were flash frozen immediately and process by Active Motif for IRF8 ChIP-Seq. Reads were aligned to mm9 by using BAM and peak calling were performed by using MACS. More details are provided in the manuscript.
Project description:Upon antigen recognition B cells undertake a bifurcated response in which some cells rapidly differentiate into plasmablasts while others undergo affinity maturation in germinal centers (GC). We uncover a double negative feedback loop between interferon regulatory factors IRF4 and IRF8, which regulates the initial bifurcation of activated B cells as well as the GC response. IRF8 dampens BCR signaling, facilitates antigen specific interaction with helper T cells, and promotes selection of high affinity clones while antagonizing IRF4 driven plasmablast differentiation. Genomic analysis reveals concentration dependent action of IRF4 and IRF8 in regulating distinctive gene expression programs. Stochastic modeling suggests that the double negative feedback is sufficient to initiate bifurcating B cell developmental trajectories.
Project description:Upon antigen recognition B cells undertake a bifurcated response in which some cells rapidly differentiate into plasmablasts while others undergo affinity maturation in germinal centers (GC). We uncover a double negative feedback loop between interferon regulatory factors IRF4 and IRF8, which regulates the initial bifurcation of activated B cells as well as the GC response. IRF8 dampens BCR signaling, facilitates antigen specific interaction with helper T cells, and promotes selection of high affinity clones while antagonizing IRF4 driven plasmablast differentiation. Genomic analysis reveals concentration dependent action of IRF4 and IRF8 in regulating distinctive gene expression programs. Stochastic modeling suggests that the double negative feedback is sufficient to initiate bifurcating B cell developmental trajectories.
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:Interferon regulatory factor 4 (IRF4) is an IRF family transcription factor with critical roles in lymphoid development and in regulating the immune response. IRF4 binds DNA weakly owing to a carboxy-terminal auto-inhibitory domain, but cooperative binding with factors such as PU.1 or SPIB in B cells increases binding affinity, allowing IRF4 to regulate genes containing ETS–IRF composite elements (EICEs; 5'-GGAAnnGAAA-3'). Here we show that in mouse CD4+ T cells, where PU.1/SPIB expression is low, and in B cells, where PU.1 is well expressed, IRF4 unexpectedly can cooperate with activator protein-1 (AP1) complexes to bind to AP1–IRF4 composite (5'-TGAnTCA/GAAA-3') motifs that we denote as AP1–IRF composite elements (AICEs). Moreover, BATF–JUN family protein complexes cooperate with IRF4 in binding to AICEs in pre-activated CD4+ T cells stimulated with IL-21 and in TH17 differentiated cells. Importantly, BATF binding was diminished in Irf4-/- T cells and IRF4 binding was diminished in Batf-/- T cells, consistent with functional cooperation between these factors. Moreover, we show that AP1 and IRF complexes cooperatively promote transcription of the Il10 gene, which is expressed in TH17 cells and potently regulated by IL-21. These findings reveal that IRF4 can signal via complexes containing ETS or AP1 motifs depending on the cellular context, thus indicating new approaches for modulating IRF4-dependent transcription. Genome-wide transcription factors mapping and binding of IRF4, BATF, IRF8, STAT3, JUN etc in WT, Irf4-/- and Batf-/- mice in different cell types (B cells, CD4+ T cells and TH17 cells) cultured with or without IL-21 was conducted. RNA-Seq is conducted in mouse B cells, CD4+ T cells, TH1/TH2/TH9/TH17/Treg.
Project description:Subset-specific and progenitor gene expression analysis of Klf4+/+ and Klf4-/- DCs. The two major lineages of classical dendritic cells (cDCs) express and require either IRF8 or IRF4 transcription factors for their development and function. IRF8-dependent cDCs promote anti-viral and T-helper 1 (Th1) cell responses, whereas IRF4-expressing cDCs have been implicated in controlling both Th2 and Th17 cell responses. Here, we have provided evidence that Kruppel-like factor 4 (Klf4) is required in IRF4-expressing cDCs to promote Th2 but not Th17 cell responses in vivo. Conditional Klf4 deletion within cDCs impaired Th2 cell responses during Schistosoma mansoni infection, Schistosoma egg antigen (SEA) immunization, and house dust mite challenge (HDM), without affecting cytotoxic T lymphocyte (CTL), Th1 and Th17 cell responses to herpes simplex virus, Toxoplasma gondii and Citrobacter rodentium infections. Further, Klf4 deletion reduced IRF4 expression in pre-cDCs and resulted in selective loss of IRF4-expressing cDCs subsets in several tissues. These results indicate that Klf4 guides a transcriptional program promoting IRF4-expressing cDCs heterogeneity. Bone marrow progenitors and skin draining LN subsets were harvested from 4 Klf4fl/fl cre negative or Vav1-icre mice and were sorted to >95% purity on the FACS Aria 3.