Browsing by Subject "Bcl6"

Now showing 1 - 8 of 8
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    AMP kinase promotes Bcl6 expression in both mouse and human T cells
    (Elsevier, 2017-01) Xie, Markus M.; Amet, Tohti; Liu, Hong; Yu, Qigui; Dent, Alexander L.; Department of Microbiology and Immunology, School of Medicine
    The transcription factor Bcl6 is a master regulator of follicular helper T (TFH) cells, and understanding the signaling pathway that induces Bcl6 and TFH cell differentiation is therefore critical. IL-2 produced during T cell activation inhibits Bcl6 expression but how TFH cells evade IL-2 inhibition is not completely understood. Here we show that Bcl6 is highly up-regulated in activated CD4 T cells following glucose deprivation (GD), and this pathway is insensitive to inhibition by IL-2. Similar to GD, the glucose analog 2-deoxyglucose (2DG) inhibits glycolysis, and 2DG induced Bcl6 expression in activated CD4 T cells. The metabolic sensor AMP kinase (AMPK) is activated when glycolysis is decreased, and the induction of Bcl6 by GD was inhibited by the AMPK antagonist compound C. Additionally, activation of AMPK by the drug AICAR caused Bcl6 up-regulation in activated CD4 T cells. When mice were immunized with KLH using AICAR as an adjuvant, there was a strong TFH–dependent enhancement of KLH-specific antibody (Ab) responses, and higher Bcl6 expression in TFH cells in vivo. Activation of AMPK strongly induced BCL6 and the up-regulation of TFH cell marker expression by human CD4 T cells. Our data reveal a major new pathway for TFH cell differentiation, conserved by both mouse and human T cells. Mature TFH cells are reported to have a lower metabolic state compared to TH1 cells. Our data indicates that decreased metabolism may be deterministic for TFH cell differentiation, and not simply a result of TFH cell differentiation.
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    Bcl6 and Blimp1 reciprocally regulate ST2+ Treg-cell development in the context of allergic airway inflammation
    (Elsevier, 2020) Koh, Byunghee; Ulrich, Benjamin J.; Nelson, Andrew S.; Panangipalli, Gayathri; Kharwadkar, Rakshin; Wu, Wenting; Xie, Markus M.; Fu, Yongyao; Turner, Matthew J.; Paczesny, Sophie; Janga, Sarath Chandra; Dent, Alexander L.; Kaplan, Mark H.; Pediatrics, School of Medicine
    Background Bcl6 is required for the development of T follicular helper cells and T follicular regulatory (Tfr) cells that regulate germinal center responses. Bcl6 also affects the function of regulatory T (Treg) cells. Objective The goal of this study was to define the functions of Bcl6 in Treg cells, including Tfr cells, in the context of allergic airway inflammation. Methods We used a model of house dust mite sensitization to challenge wild-type, Bcl6fl/fl Foxp3-Cre, and Prdm1 (Blimp1)fl/fl Foxp3-Cre mice to study the reciprocal roles of Bcl6 and Blimp1 in allergic airway inflammation. Results In the house dust mite model, Tfr cells repress the production of IgE and Bcl6+ Treg cells suppress the generation of type 2 cytokine–producing cells in the lungs. In mice with Bcl6-deficient Treg cells, twice as many ST2+ (IL-33R+) Treg cells develop as are observed in wild-type mice. ST2+ Treg cells in the context of allergic airway inflammation are Blimp1 dependent, express type 2 cytokines, and share features of visceral adipose tissue Treg cells. Bcl6-deficient Treg cells are more susceptible, and Blimp1-deficient Treg cells are resistant, to acquiring the ST2+ Treg–cell phenotype in vitro and in vivo in response to IL-33. Bcl6-deficient ST2+ Treg cells, but not Bcl6-deficient ST2+ conventional T cells, strongly promote allergic airway inflammation when transferred into recipient mice. Lastly, ST2 is required for the exacerbated allergic airway inflammation in Bcl6fl/fl Foxp3-Cre mice. Conclusions During allergic airway inflammation, Bcl6 and Blimp1 play dual roles in regulating Tfr-cell activity in the germinal center and in the development of ST2+ Treg cells that promote type 2 cytokine responses.
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    Bcl6 is a subset-defining transcription factor of lymphoid tissue inducer-like ILC3
    (Cell Press, 2023) Tachó-Piñot, Roser; Stamper, Christopher T.; King, James I.; Matei-Rascu, Veronika; Richardson, Erin; Li, Zhi; Roberts, Luke B.; Bassett, John W.; Melo-Gonzalez, Felipe; Fiancette, Rémi; Lin, I-Hsuan; Dent, Alexander; Harada, Yohsuke; Finlay, Conor; Mjösberg, Jenny; Withers, David R.; Hepworth, Matthew R.; Microbiology and Immunology, School of Medicine
    Innate lymphoid cells (ILCs) are tissue-resident effector cells with roles in tissue homeostasis, protective immunity, and inflammatory disease. Group 3 ILCs (ILC3s) are classically defined by the master transcription factor RORγt. However, ILC3 can be further subdivided into subsets that share type 3 effector modules that exhibit significant ontological, transcriptional, phenotypic, and functional heterogeneity. Notably lymphoid tissue inducer (LTi)-like ILC3s mediate effector functions not typically associated with other RORγt-expressing lymphocytes, suggesting that additional transcription factors contribute to dictate ILC3 subset phenotypes. Here, we identify Bcl6 as a subset-defining transcription factor of LTi-like ILC3s in mice and humans. Deletion of Bcl6 results in dysregulation of the LTi-like ILC3 transcriptional program and markedly enhances expression of interleukin-17A (IL-17A) and IL-17F in LTi-like ILC3s in a manner in part dependent upon the commensal microbiota-and associated with worsened inflammation in a model of colitis. Together, these findings redefine our understanding of ILC3 subset biology.
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    Bcl6 promotes follicular helper T-cell differentiation and PD-1 expression in a Blimp1-independent manner in mice
    (Wiley, 2017-07) Xie, Markus M.; Koh, Byung-Hee; Hollister, Kristin; Wu, Hao; Sun, Jie; Kaplan, Mark H.; Dent, Alexander L.; Department of Microbiology and Immunology, IU School of Medicine
    The transcription factors Bcl6 and Blimp1 have opposing roles in the development of the follicular helper T (TFH) cells: Bcl6 promotes and Blimp1 inhibits TFH-cell differentiation. Similarly, Bcl6 activates, while Blimp1 represses, expression of the TFH-cell marker PD-1. However, Bcl6 and Blimp1 repress each other's expression, complicating the interpretation of the regulatory network. Here we sought to clarify the extent to which Bcl6 and Blimp1 independently control TFH-cell differentiation by generating mice with T-cell specific deletion of both Bcl6 and Blimp1 (double conditional KO [dcKO] mice). Our data indicate that Blimp1 does not control TFH-cell differentiation independently of Bcl6. However, a population of T follicular regulatory (TFR) cells developed independently of Bcl6 in dcKO mice. We have also analyzed regulation of IL-10 and PD-1, two genes controlled by both Bcl6 and Blimp1, and observed that Bcl6 regulates both genes independently of Blimp1. We found that Bcl6 positively regulates PD-1 expression by inhibiting the ability of T-bet/Tbx21 to repress Pdcd1 transcription. Our data provide a novel mechanism for positive control of gene expression by Bcl6, and illuminate how Bcl6 and Blimp1 control TFH-cell differentiation.
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    Follicular regulatory T cells repress cytokine production by follicular helper T cells and optimize IgG responses in mice
    (Wiley, 2016-05) Wu, Hao; Chen, Yuxin; Liu, Hong; Xu, Lin-Lin; Teuscher, Paula; Wang, Shixia; Lu, Shan; Dent, Alexander L.; Department of Microbiology & Immunology, IU School of Medicine
    Follicular helper T (Tfh) cells provide crucial help to germinal center B (GCB) cells for proper antibody production, and a specialized subset of regulatory T cells, follicular regulatory T (Tfr) cells, modulate this process. However, Tfr-cell function in the GC is not well understood. Here, we define Tfr cells as a CD4(+) Foxp3(+) CXCR5(hi) PD-1(hi) CD25(low) TIGIT(high) T-cell population. Furthermore, we have used a novel mouse model ("Bcl6FC") to delete the Bcl6 gene in Foxp3(+) T cells and thus specifically deplete Tfr cells. Following immunization, Bcl6FC mice develop normal Tfh- and GCB-cell populations. However, Bcl6FC mice produce altered antigen-specific antibody responses, with reduced titers of IgG and significantly increased IgA. Bcl6FC mice also developed IgG antibodies with significantly decreased avidity to antigen in an HIV-1 gp120 "prime-boost" vaccine model. In an autoimmune lupus model, we observed strongly elevated anti-DNA IgA titers in Bcl6FC mice. Additionally, Tfh cells from Bcl6FC mice consistently produce higher levels of Interferon-γ, IL-10 and IL-21. Loss of Tfr cells therefore leads to highly abnormal Tfh-cell and GCB-cell responses. Overall, our study has uncovered unique regulatory roles for Tfr cells in the GC response.
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    IL-33 Mediated Th2 Effector Functions are Suppressed in Tregs by Bcl6 and Regulated by Sex
    (2024-08) Lee, Kyu Been; Dent, Alexander; Richer, Martin; Robinson, Christopher; Yang, Kai
    Allergic airway inflammation (asthma) is a prevalent and uncurable disease worldwide, affecting many individuals’ quality of life. Although asthma does not form from a singular cause, one primary mediator comes from the exposure to environmental allergens and the improper activation of the T cell subset: T helper 2 (Th2) cells. Th2 cells produce pro-inflammatory cytokines and promote the activation and recruitment of various pro-inflammatory cells into the lung, causing greater damage and inflammatory responses in the organ. Th2 cell’s activation is regulated by another T cell subset, Regulatory T (Treg) cells, by expressing anti-inflammatory cytokines and downregulating the inflammatory response. On the contrary, the release of interleukin-33 (IL-33) from damaged lung epithelial cells transitions Tregs into Th2-like Tregs (ST2+ Tregs) which release both pro-and anti-inflammatory cytokines and cannot suppress the inflammatory disease. However, transcriptional repressor protein B cell lymphoma 6 (Bcl6) provides Tregs a stable follicular phenotype and suppresses the ST2+ Treg transition. Preliminary data revealed that Bcl6 repressive function is dependent on mouse sex, in which Tregs of male mice are more resistant to the ST2+ Treg phenotype than those of female mice. However, the removal of Bcl6 also removed the sex-dependent suppression against the ST2+ Treg transition. The project therefore sought to further confirm and answer whether Bcl6 suppressed the ST2+ Treg phenotype in a sex-dependent manner, ultimately leading to a sex-biased asthma prevalence and severity. We utilized quantitative polymerase chain reaction (qPCR) and next-generation sequencing techniques to uncover which genes Bcl6 regulates, how IL-33 affects chromatin accessibility/gene expression, and what relation sex hormones have with Bcl6 in the expression of Th2 cytokines from Tregs. Currently, we have discovered that estrogen-like chemicals in common cell culturing media may be acting on the estrogen receptor of Tregs and causing differential gene expressions based on media conditions. We also determined that Bcl6 is acting independently of mouse sex to suppress Th2 genes in Tregs, contrary to preliminary findings. Overall, we have obtained insight on the role of the estrogen receptor and Bcl6’s mechanism of suppression in relation to sex.
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    Regulation of the germinal center reaction by T helper cells and T regulatory cells
    (2016-04-11) Wu, Hao; Dent, Alexander L.; Kaplan, Mark H.; Turner, Matthew J.; Zhou, Baohua
    Germinal Centers (GCs) are transient lymphoid structures that arise in lymphoid organs in response to T cell-dependent antigen. Within the GC, follicular T helper (TFH) cells promote GC B cell differentiation and in turn the proper antibody production to protect us from invading pathogens. We wished to study the regulation of this process by transcription factors STAT3 and Bcl6. STAT3 is important for both TFH cell differentiation and IL-4 production by Th2 cells. IL-4 is a major functional cytokine produced by TFH cells. To dissect the role of STAT3 in IL-4 production by TFH cells, we generated T cell-specific conditional STAT3 knockout mice (STAT3KO). Compared to WT mice, TFH cell differentiation in STAT3KO mice was partially impaired, both in spleen following sheep red blood cells (SRBC) immunization and in Peyer's patches (PPs). In STAT3KO mice, the numbers of splenic GC B cells were markedly decreased, whereas PP GC B cells developed at normal numbers and IgG1 class switching was greatly increased. Unexpectedly, we found that STAT3 intrinsically suppressed the expression of IL-4 and Bcl6 in TFH cells. Mechanistically, in vitro repression of IL-4 expression in CD4 T cells by Bcl6 required STAT3 function. Apart from TFH cells, the GC reaction is also controlled by regulatory follicular T helper (TFR) cells, a subset of Treg cells. To study the mechanism of how TFR cells regulate the GC reaction, we generated mice specifically lacking TFR cells by specifically deleting Bcl6 in Treg cells. Following immunization, these "Bcl6FC" mice developed normal TFH and GC B cell populations. However, Bcl6FC mice produced altered antigen-specific antibody responses, with reduced titers of IgG and increased IgA. Bcl6FC mice also developed IgG antibodies with significantly decreased avidity to antigen in an HIV-1 gp120 "prime-boost" vaccine model. Additionally, TFH cells from Bcl6FC mice produced higher levels of Interferon-γ, IL-10 and IL-21. Loss of TFR cells therefore leads to highly abnormal TFH and GC B cell responses. Overall, our studies have uncovered unexpected regulatory roles of STAT3 in TFH cell function as well as the novel regulatory roles of TFR cells on cytokine production by TFH cells and on antibody production.
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    The transcriptional repressor Bcl6 controls the stability of regulatory T cells by intrinsic and extrinsic pathways
    (Wiley, 2015-05) Sawant, Deepali V.; Wu, Hao; Yao, Weiguo; Sehra, Sarita; Kaplan, Mark H.; Dent, Alexander L.; Department of Microbiology & Immunology, IU School of Medicine
    Foxp3(+) regulatory T (Treg) cells are essential to maintain immune homeostasis, yet controversy exists about the stability of this cell population. Bcl6-deficient (Bcl6(-/-) ) mice develop severe and spontaneous T helper type 2 (Th2) inflammation and Bcl6-deficient Treg cells are ineffective at controlling Th2 responses. We used a lineage tracing approach to analyse the fate of Treg cells in these mice. In the periphery of Bcl6(-/-) mice, increased numbers of Foxp3-negative 'exTreg' cells were found, particularly in the CD25(+) population. ExTreg cells from Bcl6(-/-) mice expressed increased interleukin-17 (IL-17) and extremely elevated levels of Th2 cytokines compared with wild-type exTreg cells. Although Treg cells normally express only low levels of cytokines, Treg cells from Bcl6(-/-) mice secreted higher levels of IL-4, IL-5, IL-13 and IL-17 than wild-type conventional T cells. Next, Treg-specific conditional Bcl6-deficient (Bcl6(Foxp3-/-) ) mice were analysed. Bcl6(Foxp3-/-) mice do not develop inflammatory disease, indicating a requirement for non-Treg cells for inflammation in Bcl6(-/-) mice, and have normal numbers of exTreg cells. We induced Th2-type allergic airway inflammation in Bcl6(Foxp3-/-) mice, and found that while exTreg cytokine expression was normal, Bcl6-deficient Treg cells expressed higher levels of the Th2-specific regulator Gata3 than Bcl6(+) Treg cells. Bcl6(Foxp3-/-) mice had increased numbers of Th2 cells after induction of airway inflammation and increased T cells in the bronchoalveolar lavage fluid. These data show both Treg-intrinsic and Treg-extrinsic roles for Bcl6 in controlling Treg cell stability and Th2 inflammation, and support the idea that Bcl6 expression in Treg cells is critical for controlling Th2 responses.