B Cells at the Interface of Innate and Adoptive Immunity: Identification of IRF8 Target Genes in Germinal Center B Cells

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 4914-4914
Author(s):  
Dong-Mi Shin ◽  
Chang-Hoon Leeand Herbert Morse
Keyword(s):  
Signal Transduction ◽  
Innate Immunity ◽  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Cell Activation ◽  
Target Genes ◽  
Negative Regulator ◽  
B Cell Differentiation ◽  
And Function

Abstract IRF8 is a transcription factor widely expressed in hematopoietic cells and best known for its effects on myeloid and dendritic cell (DC) differentiation and function. Recent studies showed that IRF8 is expressed at low levels in naïve B cells, at significantly increased levels in germinal center (GC) B cells but little if at all in plasma cells. In GC, IRF8 was shown to contribute to the regulation of AID and BCL6. To better understand IRF8 contributions to the biology of mature B cells and possibly to transformation, we studied three mouse and three human lymphoma cell lines of GC origin by ChIP-Chip (C-C) analyses for IRF8 and POLII targets. We identified 87 IRF8 targets that were common to mouse and human B cells and were also positive for POLII. 17/18 of these putative IRF8 targets tested by PCR ChIP analyses were validated. IRF8 is transcriptionally activated by IFNg, and many of the newly identified targets were previously known to be IFN-responsive. Analyses of the targets identified 14 that contribute to various aspects of innate immunity at the cell surface (CD37, HSP90B1, Ly86), via signal transduction (AZI2, NFKBIZ, STAT2, IRF9), or with direct anti-viral activity (ADAR, PML, S100, ZC3HAV1 and others). Another 19 are active contributors to acquired immune functions of B cells with many involved in peptide processing and antigen presentation by both MHC class I and class II molecules (B2M, CD74, TAP1, TAP2, CTSS and 20S proteosomal components) and some in signal transduction (BLK, BLNK). Still others are active in B cell differentiation and function (MS4A1 [CD20], ELF1 and GNA13). CYLD plays in both arenas as a negative regulator of RIG-I-mediated antiviral responses and by regulating proper B cell activation after BCR ligation. The regulatory contributions of IRF8 to innate immunity in DC, macrophages, granulocytes and now B cells as well as elements of acquired immunity in B cells suggest that it contributes to an evolutionary bridge that positions a single cell type to integrate critical defense mechanisms from the innate and acquired immune repertoires.

scholarly journals B Cell-Intrinsic SHP1 Expression Promotes the Gammaherpesvirus-Driven Germinal Center Response and the Establishment of Chronic Infection

2019 ◽  
Vol 94 (1) ◽  
Author(s):  
K. E. Johnson ◽  
P. T. Lange ◽  
C. N. Jondle ◽  
P. J. Volberding ◽  
U. M. Lorenz ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Chronic Infection ◽  
Cell Activation ◽  
Tyrosine Phosphatase ◽  
Viral Latency ◽  
Negative Regulator ◽  
B Cell Differentiation

ABSTRACT Gammaherpesviruses are ubiquitous pathogens that establish lifelong infections in the majority of adults worldwide. Chronic gammaherpesvirus infection has been implicated in both lymphomagenesis and, somewhat controversially, autoimmune disease development. Pathogenesis is largely associated with the unique ability of gammaherpesviruses to usurp B cell differentiation, specifically, the germinal center response, to establish long-term latency in memory B cells. The host tyrosine phosphatase SHP1 is known as a brake on immune cell activation and is downregulated in several gammaherpesvirus-driven malignancies. However, here we demonstrate that B cell- but not T cell-intrinsic SHP1 expression supports the gammaherpesvirus-driven germinal center response and the establishment of viral latency. Furthermore, B cell-intrinsic SHP1 deficiency cooperated with gammaherpesvirus infection to increase the levels of double-stranded DNA-reactive antibodies at the peak of viral latency. Thus, in spite of decreased SHP1 levels in gammaherpesvirus-driven B cell lymphomas, B cell-intrinsic SHP1 expression plays a proviral role during the establishment of chronic infection, suggesting that the gammaherpesvirus-SHP1 interaction is more nuanced and is modified by the stage of infection and pathogenesis. IMPORTANCE Gammaherpesviruses establish lifelong infection in a majority of adults worldwide and are associated with a number of malignancies, including B cell lymphomas. These viruses infect naive B cells and manipulate B cell differentiation to achieve a lifelong infection of memory B cells. The germinal center stage of B cell differentiation is important as both an amplifier of the viral latent reservoir and the target of malignant transformation. In this study, we demonstrate that expression of tyrosine phosphatase SHP1, a negative regulator that normally limits the activation and proliferation of hematopoietic cells, enhances the gammaherpesvirus-driven germinal center response and the establishment of chronic infection. The results of this study uncover an intriguing beneficial interaction between gammaherpesviruses that are presumed to profit from B cell activation and a cellular phosphatase that is traditionally perceived to be a negative regulator of the same processes.

scholarly journals Restriction of memory B cell differentiation at the germinal center B cell positive selection stage

2020 ◽  
Vol 217 (7) ◽  
Author(s):  
Amparo Toboso-Navasa ◽  
Arief Gunawan ◽  
Giulia Morlino ◽  
Rinako Nakagawa ◽  
Andrea Taddei ◽  
...  
Keyword(s):  
B Cells ◽  
Positive Selection ◽  
B Cell ◽  
Cell Fate ◽  
Germinal Center ◽  
Target Genes ◽  
Zinc Finger Protein ◽  
B Cell Differentiation ◽  
Repressor Complex ◽  
Selection Stage

Memory B cells (MBCs) are key for protection from reinfection. However, it is mechanistically unclear how germinal center (GC) B cells differentiate into MBCs. MYC is transiently induced in cells fated for GC expansion and plasma cell (PC) formation, so-called positively selected GC B cells. We found that these cells coexpressed MYC and MIZ1 (MYC-interacting zinc-finger protein 1 [ZBTB17]). MYC and MIZ1 are transcriptional activators; however, they form a transcriptional repressor complex that represses MIZ1 target genes. Mice lacking MYC–MIZ1 complexes displayed impaired cell cycle entry of positively selected GC B cells and reduced GC B cell expansion and PC formation. Notably, absence of MYC–MIZ1 complexes in positively selected GC B cells led to a gene expression profile alike that of MBCs and increased MBC differentiation. Thus, at the GC positive selection stage, MYC–MIZ1 complexes are required for effective GC expansion and PC formation and to restrict MBC differentiation. We propose that MYC and MIZ1 form a module that regulates GC B cell fate.

scholarly journals Complete Block of Early B Cell Differentiation in Mice Lacking the Endosomal Adaptor Protein p14

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 1026-1026
Author(s):  
Marcin Lyszkiewicz ◽  
Daniel Kotlarz ◽  
Natalia Zietara ◽  
Gudrun Brandes ◽  
Jana Diestelhorst ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Target Genes ◽  
Conflicts Of Interest ◽  
Adaptor Protein ◽  
Cell Development ◽  
B Cell Development ◽  
B Cell Differentiation ◽  
Knock Out ◽  
And Function

Abstract Human primary immunodeficiency caused by a point mutation in the 3' untranslated region of the endosomal adaptor protein p14 (also known as Lamtor2) resulted in severely impaired function of neutrophils, B cells, T cells and melanocytes. However, complexity of the phenotype and scarcity of human material preclude in-depth studies. Therefore, to gain insight into the role of p14 in B cell development and function, we generated loxP conditional knock-out mice. Using mb-1-Cre mice we demonstrated that loss of p14 at the preB1 stage lead to a complete block of B cell development, resulting in the absence of IgM-positive B cells. Further, to test the significance of p14 deficiency in peripheral organs, we took advantage of CD19-Cre mice, which have limited efficiency in deleting target genes in the bone marrow, but reach up to 95% efficiency in spleen. Thus, we could demonstrate that later in B cell development, p14 was essential for the generation and activation of mature B lymphocytes. While B1 cell development was maintained, splenic follicular B cells were massively reduced in the absence of p14. Furthermore, activation of B cell receptor (BCR) resulted in impaired intracellular signalling and proliferation of p14 deficient B cells. In particular, lack of p14 lead to delayed internalization of BCR and endosomal processing associated with impaired mobilization of Ca++ from intracellular stores as well as aberrant phosphorylation of BCR-associated kinases. In conclusion, our data revealed that p14 is a critical regulator of B cell development and function, which acts by modulating BCR signalling. Disclosures No relevant conflicts of interest to declare.

MicroRNAs Regulate Mature B Cell Differentiation

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 705-705
Author(s):  
Jenny Zhang ◽  
Dereje D. Jima ◽  
Cassandra L. Jacobs ◽  
Eva Gottwein ◽  
Grace Huang ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Target Genes ◽  
Expression Patterns ◽  
Microrna Expression ◽  
Seed Sequence ◽  
B Cell Differentiation ◽  
Cell Stage

Abstract Background: Mature B cell differentiation provides an important mechanism for the acquisition of adaptive immunity. Malignancies derived from mature B cells are common and constitute the majority of leukemias and lymphomas. MicroRNAs are known to play a role in oncogenesis, lineage-selection, and immune cell function, including early B cell differentiation. However, the full extent and function of microRNA expression during mature B cell differentiation and in B cell malignancies are not known. Methods: From normal young patients undergoing tonsillectomies, we sorted the mature B cell subsets (naive, germinal center, memory and plasma) using FACS, based on their expression of CD19, CD38, IgD and CD27. These sorted B cells were profiled for microRNA expression using a highly sensitive multiplexed real-time PCR assay, as well as for gene expression at the whole genome level using Affymetrix U133plus microarrays. miRNA targets can be predicted based on seed sequence matching of their 2–8 nt to the 3′UTR of gene transcripts. For each B cell stage, we experimentally validated microRNA regulation of predicted target genes of interest, LMO2, MYBL1 and PRDM1, by microRNA over-expression experiments and luciferase assays. Results: We found that microRNAs have a characteristic expression pattern that defines each mature B cell stage. Examination of both microRNA and mRNA expression showed that in each B cell population, the target genes predicted based on seed matching were expressed at lower levels, results that were highly significant (P<1E-10). We found that differential microRNA expression is important at every B cell stage transition, and differentially expressed microRNAs frequently target differentially expressed transcription factors. In the naive to germinal center B cell and germinal center B cell to memory cell transitions, we found that miR-223 had an inverse relationship with its predicted target genes LMO2 and MYBL1. To test this relationship predicted based on seed pairing, in Germinal Center-derived BJAB cells, we over-expressed miR-223 by introducing its precursor, and saw a subsequent knockdown of LMO2 and MYBL1 at both the mRNA and protein level. We confirmed seed sequence specificity by comparing miR-223 knockdown of luciferase reporter activity on the LMO2 3′UTR compared to its seed sequence mutant. We further found that miR-9 and miR-30 family members directly regulate PRDM1 (blimp1), a master regulator of the GC to PC transition. In U266 cells (PC-derived), introduction of miR-9 and miR-30 family precursor resulted in decreased PRDM1 protein expression, although transcript levels were not changed, consistent with previous evidence that miRNA can regulate at the post-transcriptional steps. We further profiled over 50 tumors derived from various B cell malignancies (small lymphocytic lymphoma, Burkitt lymphoma, and the molecular subsets of diffuse large B cell lymphoma) and found that these malignancies maintain the expression patterns of their respective lineage; microRNA expression profiles of normal B cells could correctly classify the lineage of these tumors in over 80% of the cases. In contrast to other malignancies, common lymphomas do not down-regulate microRNAs, but rather maintain the microRNA-expression patterns of their normal B-cell counterparts. Conclusion: Through concomitant microRNA and mRNA-profiling, we demonstrate a regulatory role for microRNAs at every stage in mature B-cell differentiation. Further, we have experimentally identified a direct role for the microRNA-regulation of key transcription factors in B-cell differentiation: LMO2, MYBL1 and PRDM1 (Blimp1). Thus, our data demonstrate that microRNAs may be important in maintaining the mature B-cell phenotype in normal and malignant B-cells.

scholarly journals Germinal Center Marker GL7 Probes Activation-Dependent Repression of N-Glycolylneuraminic Acid, a Sialic Acid Species Involved in the Negative Modulation of B-Cell Activation

2007 ◽  
Vol 27 (8) ◽  
pp. 3008-3022 ◽  
Author(s):  
Yuko Naito ◽  
Hiromu Takematsu ◽  
Susumu Koyama ◽  
Shizu Miyake ◽  
Harumi Yamamoto ◽  
...  
Keyword(s):  
Sialic Acid ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Cell Activation ◽  
Germinal Centers ◽  
Negative Regulator ◽  
B Cell Activation ◽  
Germinal Center B Cells

ABSTRACT Sialic acid (Sia) is a family of acidic nine-carbon sugars that occupies the nonreducing terminus of glycan chains. Diversity of Sia is achieved by variation in the linkage to the underlying sugar and modification of the Sia molecule. Here we identified Sia-dependent epitope specificity for GL7, a rat monoclonal antibody, to probe germinal centers upon T cell-dependent immunity. GL7 recognizes sialylated glycan(s), the α2,6-linked N-acetylneuraminic acid (Neu5Ac) on a lactosamine glycan chain(s), in both Sia modification- and Sia linkage-dependent manners. In mouse germinal center B cells, the expression of the GL7 epitope was upregulated due to the in situ repression of CMP-Neu5Ac hydroxylase (Cmah), the enzyme responsible for Sia modification of Neu5Ac to Neu5Gc. Such Cmah repression caused activation-dependent dynamic reduction of CD22 ligand expression without losing α2,6-linked sialylation in germinal centers. The in vivo function of Cmah was analyzed using gene-disrupted mice. Phenotypic analyses showed that Neu5Gc glycan functions as a negative regulator for B-cell activation in assays of T-cell-independent immunization response and splenic B-cell proliferation. Thus, Neu5Gc is required for optimal negative regulation, and the reaction is specifically suppressed in activated B cells, i.e., germinal center B cells.

OCT2 (Octamer Binding Protein 2): An Essential Role in Germinal Center B Cell Differentiation and the “Achilles Heel” of Derived Lymphomas.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 362-362 ◽  
Author(s):  
Stella M Ranuncolo ◽  
Vu Ngo ◽  
Georg Lenz ◽  
Wenming Xiao ◽  
George Wright ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Cell Lines ◽  
Germinal Center ◽  
Target Genes ◽  
B Cell Differentiation ◽  
Pou Domain ◽  
Germinal Center B Cell ◽  
Octamer Motif

Abstract Abstract 362 To identify genes requiered for the proliferation and survival of Diffuse Large B Cell Lymphomas (DLBCL) we conducted an “Achilles Heel” RNA interference screen in cell lines model of ABC (Activated B cell-like) and GCB (Germinal Center B-cell like) DLBCL subtypes. One of the most toxic small hairpins RNAs (shRNAs) in this screen targeted Oct2, encoding a POU domain transcriptional activator. Unlike Oct1, which is constitutively expressed in many cell types, Oct2 is primarily lymphoid restricted. It was identified by virtue of its ability to bind the highly conserved DNA octamer motif (ATGCAAAT) within immunoglobulin (Ig) genes promoters. The B cell specific co-activator OCA-B interacts with the POU domain of the octamer binding proteins enhancing their transactivation potential. Although Oct2 and OCA-B are not essential for Ig transcription, they are required for germinal center (GC) B cell differentiation. To understand the massive apoptotic cell death of DLBCL cells following shRNA Oct2 induction we investigated the genetic pathways controlled by Oct2. We profiled gene expression changes in DLBCL cell lines after knocking down Oct2 and merged this data set with data from genome-wide assessment of Oct2 and OCA-B binding sites, coupling chromatin immunoprecipitation (ChiP) with high-throughput sequencing technologies (ChIP-Seq). ChIP-Seq uncovered an extensive network of Oct2 target genes in DLBCL cells. More than 60% of the Oct2 target genes also showed OCA-B biding. This Oct2/OCA-B overlaping set of targets was enriched for genes selectively expressed in pan-B cells and GC B cells. We found that Oct2/OCA-B lie upstream many of the main transcription factors known to play an essential role in inducing and mantaining the GC stage of B cell development such as BCL6, MTA3, PU.1, IRF8, SpiB and OCA-B, among others. Oct2/OCA-B target these genes both in DLBCL cells and in normal human primary centroblasts. Strikingly, among Oct-2 downstream effectors, BCL6 cDNA was enough to rescue both ABC and GCB DLBCL cells from the Oct2 shRNA lethal effect. The Oct2/OCA-B binding of BCL6 promoter was confirmed in vivo by single locus ChIP in different GCB-DLBCL cell lines as well as in primary centroblasts isolated from human tonsils. Gel shifts experiments showed Oct2 binding to more than one non canonical octamer motif within the BCL6 promoter. Furthermore, computational analysis of the BCL6 promoter region bound by Oct2, showed PU.1 binding sites. Knocked down of PU.1 decreased Oct2 enrichment and viceversa suggesting cooperative Oct2/PU.1 biding to BCL6 pomoter. ChIP-Seq findings opened an entire and exciting new chapter in the Oct2 biology field. Pou transcription factors were suppossed to regulate the activity of octamer containing promoters. Interestingly, Oct2 binds to and control the expression of many GC specific genes that do not harbor a “canonical octamer” motif. Eventhough Oct2 is expressed throughout the different stages of B cell maturation, both mRNA and protein levels are enhanced in centroblasts as compared to pre-GC B cells. We found Oct2 capable of inducing its own expression as well as Oct-1 and OCA-B. This autoregulatory circuit might partially account for the Oct2 predominant role in GC specific genes expression control. By array cGH, high level amplification of Oct2 and OCA-B was found in less than 10% of non Hodgkin lymphoma patients samples. Nonetheless, these lymphoma cells become addicted to the Oct2 controlled network that sustain cell survival and proliferation, wich turns Oct2 into an attractive therapeutic target for non Hodking lymphoma patients. This critical Oct2 DLBCL cells dependency, is an example of “non oncogene addiction” that we recently defined based on our RNA interference screening. Oct-2 controls a network of regulatory relationships that sustain both normal GC B cells and malignant counterparts. In summary, we showed that Oct2 and OCA-B lie upstream of BCL6, one of the critical regulators of germinal center B cell differentiation. This suggests that Oct2-directed therapy should kill the same DLBCLs as BCL6-directed therapy. Furthermore, all GC and Post-GC B cells that were tested requiere Oct-2 for survival, indicating that Oct2-directed therapy might have a broder activity spectrum than the BCL6-directed therapy. The Oct2/OCA-B binding interface would be amenable to attack with potential manageable toxicity, since this interaction is exclusively required in GC B cells. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Regulation of normal B-cell differentiation and malignant B-cell survival by OCT2

2016 ◽  
Vol 113 (14) ◽  
pp. E2039-E2046 ◽  
Author(s):  
Daniel J. Hodson ◽  
Arthur L. Shaffer ◽  
Wenming Xiao ◽  
George W. Wright ◽  
Roland Schmitz ◽  
...  
Keyword(s):  
B Cells ◽  
Dna Binding ◽  
B Cell ◽  
Germinal Center ◽  
Target Genes ◽  
B Cell Lymphoma ◽  
Conditional Knockout ◽  
B Cell Differentiation ◽  
Germinal Center B Cells

The requirement for the B-cell transcription factor OCT2 (octamer-binding protein 2, encoded by Pou2f2) in germinal center B cells has proved controversial. Here, we report that germinal center B cells are formed normally after depletion of OCT2 in a conditional knockout mouse, but their proliferation is reduced and in vivo differentiation to antibody-secreting plasma cells is blocked. This finding led us to examine the role of OCT2 in germinal center-derived lymphomas. shRNA knockdown showed that almost all diffuse large B-cell lymphoma (DLBCL) cell lines are addicted to the expression of OCT2 and its coactivator OCA-B. Genome-wide chromatin immunoprecipitation (ChIP) analysis and gene-expression profiling revealed the broad transcriptional program regulated by OCT2 that includes the expression of STAT3, IL-10, ELL2, XBP1, MYC, TERT, and ADA. Importantly, genetic alteration of OCT2 is not a requirement for cellular addiction in DLBCL. However, we detected amplifications of the POU2F2 locus in DLBCL tumor biopsies and a recurrent mutation of threonine 223 in the DNA-binding domain of OCT2. This neomorphic mutation subtly alters the DNA-binding preference of OCT2, leading to the transactivation of noncanonical target genes including HIF1a and FCRL3. Finally, by introducing mutations designed to disrupt the OCT2–OCA-B interface, we reveal a requirement for this protein–protein interface that ultimately might be exploited therapeutically. Our findings, combined with the predominantly B-cell–restricted expression of OCT2 and the absence of a systemic phenotype in our knockout mice, suggest that an OCT2-targeted therapeutic strategy would be efficacious in both major subtypes of DLBCL while avoiding systemic toxicity.

scholarly journals Hyaluronate-CD44 Interactions Can Induce Murine B-Cell Activation

Blood ◽  
1997 ◽  
Vol 89 (8) ◽  
pp. 2901-2908 ◽  
Author(s):  
Asimah Rafi ◽  
Mitzi Nagarkatti ◽  
Prakash S. Nagarkatti
Keyword(s):  
T Cells ◽  
B Cells ◽  
B Cell ◽  
Cell Activation ◽  
Critical Role ◽  
Surface Glycoprotein ◽  
B Cell Differentiation ◽  
B Cell Activation ◽  
Cell Surface Glycoprotein ◽  
Immunodeficient Mice

Abstract CD44 is a widely distributed cell surface glycoprotein whose principal ligand has been identified as hyaluronic acid (HA), a major component of the extracellular matrix (ECM). Recent studies have demonstrated that activation through CD44 leads to induction of effector function in T cells and macrophages. In the current study, we investigated whether HA or monoclonal antibodies (MoAbs) against CD44 would induce a proliferative response in mouse lymphocytes. Spleen cells from normal and nude, but not severe combined immunodeficient mice, exhibited strong proliferative responsiveness to stimulation with soluble HA or anti-CD44 MoAbs. Furthermore, purified B cells, but not T cells, were found to respond to HA. HA was unable to stimulate T cells even in the presence of antigen presenting cells (APC) and was unable to act as a costimulus in the presence of mitogenic or submitogenic concentrations of anti-CD3 MoAbs. In contrast, stimulation of B cells with HA in vitro, led to B-cell differentiation as measured by production of IgM antibodies in addition to increased expression of CD44 and decreased levels of CD45R. The fact that the B cells were responding directly to HA through its binding to CD44 and not to any contaminants or endotoxins was demonstrated by the fact that F(ab)2 fragments of anti-CD44 MoAbs or soluble CD44 fusion proteins could significantly inhibit the HA-induced proliferation of B cells. Also, HA-induced proliferation of B cells was not affected by the addition of polymixin B, and B cells from lipopolysaccharide (LPS)-unresponsive C3H/HeJ strain responded strongly to stimulation with HA. Furthermore, HA, but not chondroitin-sulfate, another major component of the ECM, induced B-cell activation. It was also noted that injection of HA intraperitoneally, triggered splenic B cell proliferation in vivo. Together, the current study demonstrates that interaction between HA and CD44 can regulate murine B-cell effector functions and that such interactions may play a critical role during normal or autoimmune responsiveness of B cells.

scholarly journals NFκB1 is essential to prevent the development of multiorgan autoimmunity by limiting IL-6 production in follicular B cells

2016 ◽  
Vol 213 (4) ◽  
pp. 621-641 ◽  
Author(s):  
Elisha de Valle ◽  
George Grigoriadis ◽  
Lorraine A. O’Reilly ◽  
Simon N. Willis ◽  
Mhairi J. Maxwell ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Receptor Activation ◽  
Spontaneous Generation ◽  
B Cell Differentiation ◽  
Toll Like Receptor ◽  
Intrinsic Loss ◽  
And Function ◽  
Follicular B Cells

We examined the role of NFκB1 in the homeostasis and function of peripheral follicular (Fo) B cells. Aging mice lacking NFκB1 (Nfκb1−/−) develop lymphoproliferative and multiorgan autoimmune disease attributed in large part to the deregulated activity of Nfκb1−/− Fo B cells that produce excessive levels of the proinflammatory cytokine interleukin 6 (IL-6). Despite enhanced germinal center (GC) B cell differentiation, the formation of GC structures was severely disrupted in the Nfκb1−/− mice. Bone marrow chimeric mice revealed that the Fo B cell–intrinsic loss of NFκB1 led to the spontaneous generation of GC B cells. This was primarily the result of an increase in IL-6 levels, which promotes the differentiation of Fo helper CD4+ T cells and acts in an autocrine manner to reduce antigen receptor and toll-like receptor activation thresholds in a population of proliferating IgM+ Nfκb1−/− Fo B cells. We demonstrate that p50-NFκB1 represses Il-6 transcription in Fo B cells, with the loss of NFκB1 also resulting in the uncontrolled RELA-driven transcription of Il-6. Collectively, our findings identify a previously unrecognized role for NFκB1 in preventing multiorgan autoimmunity through its negative regulation of Il-6 gene expression in Fo B cells.

scholarly journals Regulation of the germinal center gene program by interferon (IFN) regulatory factor 8/IFN consensus sequence-binding protein

2005 ◽  
Vol 203 (1) ◽  
pp. 63-72 ◽  
Author(s):  
Chang Hoon Lee ◽  
Mark Melchers ◽  
Hongsheng Wang ◽  
Ted A. Torrey ◽  
Rebecca Slota ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Transcriptional Activation ◽  
Germinal Center ◽  
Target Genes ◽  
Fluorescent Protein ◽  
Binding Protein ◽  
Consensus Sequence ◽  
B Cell Lymphoma ◽  
Regulatory Factor

Interferon (IFN) consensus sequence-binding protein/IFN regulatory factor 8 (IRF8) is a transcription factor that regulates the differentiation and function of macrophages, granulocytes, and dendritic cells through activation or repression of target genes. Although IRF8 is also expressed in lymphocytes, its roles in B cell and T cell maturation or function are ill defined, and few transcriptional targets are known. Gene expression profiling of human tonsillar B cells and mouse B cell lymphomas showed that IRF8 transcripts were expressed at highest levels in centroblasts, either from secondary lymphoid tissue or transformed cells. In addition, staining for IRF8 was most intense in tonsillar germinal center (GC) dark-zone centroblasts. To discover B cell genes regulated by IRF8, we transfected purified primary tonsillar B cells with enhanced green fluorescent protein–tagged IRF8, generated small interfering RNA knockdowns of IRF8 expression in a mouse B cell lymphoma cell line, and examined the effects of a null mutation of IRF8 on B cells. Each approach identified activation-induced cytidine deaminase (AICDA) and BCL6 as targets of transcriptional activation. Chromatin immunoprecipitation studies demonstrated in vivo occupancy of 5′ sequences of both genes by IRF8 protein. These results suggest previously unappreciated roles for IRF8 in the transcriptional regulation of B cell GC reactions that include direct regulation of AICDA and BCL6.

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