scholarly journals The Transcription Factor Bach2 Is Phosphorylated at Multiple Sites in Murine B Cells but a Single Site Prevents Its Nuclear Localization

2015 ◽  
Vol 291 (4) ◽  
pp. 1826-1840 ◽  
Author(s):  
Ryo Ando ◽  
Hiroki Shima ◽  
Toru Tamahara ◽  
Yoshihiro Sato ◽  
Miki Watanabe-Matsui ◽  
...  
Keyword(s):  
Transcription Factor ◽  
B Cells ◽  
B Cell ◽  
Mtor Pathway ◽  
Immunoglobulin M ◽  
Mass Spectrometry Analysis ◽  
Nuclear Accumulation ◽  
Single Mutation ◽  
Activated B Cells

The transcription factor Bach2 regulates the immune system at multiple points, including class switch recombination (CSR) in activated B cells and the function of T cells in part by restricting their terminal differentiation. However, the regulation of Bach2 expression and its activity in the immune cells are still unclear. Here, we demonstrated that Bach2 mRNA expression decreased in Pten-deficient primary B cells. Bach2 was phosphorylated in primary B cells, which was increased upon the activation of the B cell receptor by an anti-immunoglobulin M (IgM) antibody or CD40 ligand. Using specific inhibitors of kinases, the phosphorylation of Bach2 in activated B cells was shown to depend on the phosphatidylinositol 3-kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR) pathway. The complex of mTOR and Raptor phosphorylated Bach2 in vitro. We identified multiple new phosphorylation sites of Bach2 by mass spectrometry analysis of epitope-tagged Bach2 expressed in the mature B cell line BAL17. Among the sites identified, serine 535 (Ser-535) was critical for the regulation of Bach2 because a single mutation of Ser-535 abolished cytoplasmic accumulation of Bach2, promoting its nuclear accumulation in pre-B cells, whereas Ser-509 played an auxiliary role. Bach2 repressor activity was enhanced by the Ser-535 mutation in B cells. These results suggest that the PI3K-Akt-mTOR pathway inhibits Bach2 by both repressing its expression and inducing its phosphorylation in B cells.

scholarly journals The autoantigen-binding B cell repertoires of normal and of chronically graft-versus-host-diseased mice.

1987 ◽  
Vol 165 (6) ◽  
pp. 1675-1687 ◽  
Author(s):  
A G Rolink ◽  
T Radaszkiewicz ◽  
F Melchers
Keyword(s):  
T Cells ◽  
B Cells ◽  
B Cell ◽  
The Other ◽  
Cell Populations ◽  
Foreign Antigen ◽  
Alloreactive T Cells ◽  
Polyclonal Activator ◽  
Activated B Cells

A quantitative analysis of the frequencies of autoantibody-producing B cells in GVHD and in normal mice has been undertaken by generating collections of hybridomas of activated B cells. These hybridomas secreted sufficient quantities of Ig to allow binding analyses on a panel of autoantigens. B cells have been activated in a variety of ways. In vivo they were activated by injection of alloreactive T cells of one parent, leading to GVHD by a foreign antigen, sheep erythrocytes, in a secondary response, or by the polyclonal activator LPS. B cells from an experimentally unstimulated animal were used for an analysis of the normal background. In vitro B cells were activated by alloreactive T cells or by LPS. The frequencies of hybridomas and, therefore, of activated B cells producing autoantibodies to DNA or to kidney were not significantly different in mice activated by a graft-vs.-host T cell response as compared with B cell populations activated by any of the other procedures. They were found to compose 7.1-17.1% of the total repertoire of activated B cells. Moreover, the frequencies of autoantibody-producing activated B cells does not change with time after induction of the graft-vs.-host reaction. The pattern and frequencies of autoantigen-binding specificities to cytoskeleton, smooth muscle, nuclei, mitochondria, and DNA were not found to be different in any of the groups of hybridomas. The single notable exception, found in GVHD mice, were hybridomas producing autoantibodies to kidney proximal tubular brush border. These results allow the conclusion that autoantigen-binding B cells exist in an activated state in GVHD mice, as well as in mice activated by a foreign antigen or by a polyclonal activator, in B cell populations activated in vitro either by alloreactive T cells or by a polyclonal activator, and even in the background of experimentally unstimulated animals. T cell-mediated graft-vs.-host activation, in large part, does not lead to a selective expansion of autoantigen-binding B cells. The main difference between the graft-vs.-host-activated B cell repertoire and all others is that approximately 90% of teh autoantibodies were of the IgG class, whereas al autoantibodies found in the other groups were IgM.

CD40 inhibits B cell apoptosis by upregulating bcl-xL expression and blocking oxidant accumulation

1997 ◽  
Vol 272 (3) ◽  
pp. C950-C956 ◽  
Author(s):  
W. Fang ◽  
K. A. Nath ◽  
M. F. Mackey ◽  
R. J. Noelle ◽  
D. L. Mueller ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cd40 Ligand ◽  
Antioxidant Response ◽  
Immunoglobulin M ◽  
Inhibitory Protein ◽  
Wehi 231 ◽  
Immature Mouse

Signaling through the CD40 receptor on human and murine B lymphocytes is necessary for germinal center formation and immunoglobulin class switching in vivo and rescues B cells from apoptosis triggered by cross-linking of surface immunoglobulin M in vitro. Ligation of CD40 on the immature mouse B cell line WEHI-231 with recombinant CD40 ligand (CD40L) was found to protect cells from apoptosis after gamma irradiation, as well as that following treatment with the sphingomyelin ceramide or compounds that deplete intracellular glutathione. CD40 signaling led to a rapid increase in the expression of the apoptosis inhibitory protein Bcl-xL. In addition, the apoptosis-induced accumulation of intracellular oxidants in WEHI-231 B cells was rapidly diminished by CD40 crosslinking. This antioxidant response was observed within 1 h and coincided with a preservation of intracellular thiols. These findings indicate that CD40 signaling induces a generalized cellular resistance to apoptosis characterized by an upregulation of Bcl-xL and changes in the intracellular redox potential.

scholarly journals Cd5 Maintains Tolerance in Anergic B Cells

2000 ◽  
Vol 191 (5) ◽  
pp. 883-890 ◽  
Author(s):  
Keli L. Hippen ◽  
Lina E. Tze ◽  
Timothy W. Behrens
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Receptor ◽  
Immunoglobulin M ◽  
B Cell Tolerance ◽  
Cell Responses ◽  
B Cell Anergy ◽  
Clonal Anergy

Clonal anergy of autoreactive B cells is a key mechanism regulating tolerance. Here, we show that anergic B cells express significant surface levels of CD5, a molecule normally found on T cells and a subset of B-1 cells. Breeding of the hen egg lysozyme (HEL) transgenic model for B cell anergy onto the CD5 null background resulted in a spontaneous loss of B cell tolerance in vivo. Evidence for this included elevated levels of anti-HEL immunoglobulin M (IgM) antibodies in the serum of CD5−/− mice transgenic for both an HEL-specific B cell receptor (BCR) and soluble lysozyme. “Anergic” B cells lacking CD5 also showed enhanced proliferative responses in vitro and elevated intracellular Ca2+ levels at rest and after IgM cross-linking. These data support the hypothesis that CD5 negatively regulates Ig receptor signaling in anergic B cells and functions to inhibit autoimmune B cell responses.

CD40 Ligand Activation Alters B Cell Migration to Secondary Lymphoid Organs.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 935-935
Author(s):  
Yvonne A. Efebera ◽  
Tahamtan Ahmadi ◽  
Amanda Flies ◽  
David H. Sherr
Keyword(s):  
B Cells ◽  
Lymph Nodes ◽  
B Cell ◽  
Cd40 Ligand ◽  
Lymphoid Organs ◽  
Cell Populations ◽  
Secondary Lymphoid Organs ◽  
Activated B Cells

Abstract Background: An increased understanding of the requirements for antigen presentation has encouraged development of cell-based cancer vaccines. Trials using dendritic cells (DC) as antigen presenting cells (APC) for immunotherapy of several malignancies have shown considerable success. However, the difficulty in generating large numbers of DC required for these immunizations has led to the search for alternative APC. One such candidate is the CD40 ligand (CD40L)-activated B cell, populations of which can readily be expanded in vitro. To be an effective vehicle for antigen presentation to T cells, CD40L-activated B cells must be capable of migrating to secondary lymphoid organs. Therefore, CD40L-activated B cell migration following subcutaneous or intravenous injection was evaluated. Methods: Splenic B cells from GFP transgenic mice were activated with CD40L + IL-4 and expanded in vitro prior to i.v. or s.c. injection of 3–4 x 107 into C57BL/6 mice. Recipient mice were sacrificed 2 hrs or 1–14 days thereafter and the percentage of GFP+/B220+ B cells quantified in spleens and lymph nodes by flow cytometry. Localization of these cells within lymphoid organs was determined by immunohistochemistry. In some experiments, activated C57BL/6 B cells were labeled with carboxy fluorescein succinimidyl ester (CFSE) to evaluate cell growth in vivo. Results: Murine B cell populations were readily expanded by culture on CD40L-transfected L cells in the presence of IL-4. CD40L-activated B cells expressed high levels of CD80, CD86, and LFA-1 but decreased levels of L-selectin relative to naive cells. Following i.v. injection, activated B cells were detected in spleens and lymph nodes within 1 day. Peak concentrations of activated B cells were noted in spleens and lymph nodes on days 7 (4.8% of injected cells) and 10 (1.25% of injected cells) respectively, suggesting expansion of the activated B cell population in vivo. Naive B cells injected i.v. were detected within 1 day but their number declined precipitously thereafter. Following s.c. injection, peak levels of CD40L-activated B cells were noted on day 5 (spleens) and day 7 (lymph nodes). As determined by immunohistochemistry, both CD40L-activated and naïve B cells injected i.v. appeared in B cell regions of spleens and lymph nodes. While the kinetics of accumulation of CD40L-activated B cells injected s.c. or i.v. were similar, s.c. injected CD40L-activated B cells homed to the T cell regions of spleens and lymph nodes. CFSE experiments indicated that these activated B cells continue to grow in vivo. In contrast, naïve B cells injected s.c. only appeared in B cell regions. Conclusion: CD40L-activated B cell populations can readily be expanded in vitro, CD40L-activated B cells migrate to secondary lymphoid organs even when injected s.c., activated B cell populations expand in vivo, and s.c. injected, CD40L-activated B cells preferentially home to T cell regions of secondary lymphoid organs. These results suggest that this effective APC may serve as an important vehicle for delivery and presentation of exogenous (e.g. tumor) antigens to T cells in vivo.

scholarly journals Impaired hematopoiesis in mice lacking the transcription factor Sp3

Blood ◽  
2003 ◽  
Vol 102 (3) ◽  
pp. 858-866 ◽  
Author(s):  
Pieter Fokko van Loo ◽  
Peter Bouwman ◽  
Kam-Wing Ling ◽  
Sabine Middendorp ◽  
Guntram Suske ◽  
...  
Keyword(s):  
Transcription Factor ◽  
B Cell ◽  
Perinatal Death ◽  
Myeloid Cell ◽  
Immunoglobulin M ◽  
Cell Proliferation And Differentiation ◽  
Transplantation Assay ◽  
Factor Specificity

Abstract As the zinc-finger transcription factor specificity protein 3 (Sp3) has been implicated in the regulation of many hematopoietic-specific genes, we analyzed the role of Sp3 in hematopoiesis. At embryonic day 18.5 (E18.5), Sp3-/- mice exhibit a partial arrest of T-cell development in the thymus and B-cell numbers are reduced in liver and spleen. However, pre–B-cell proliferation and differentiation into immunoglobulin M–positive (IgM+) B cells in vitro are not affected. At E14.5 and E16.5, Sp3-/- mice exhibit a significant delay in the appearance of definitive erythrocytes in the blood, paralleled by a defect in the progression of differentiation of definitive erythroid cells in vitro. Perinatal death of the null mutants precludes the analysis of adult hematopoiesis in Sp3-/- mice. We therefore investigated the ability of E12.5 Sp3-/- liver cells to contribute to the hematopoietic compartment in an in vivo transplantation assay. Sp3-/- cells were able to repopulate the B- and T-lymphoid compartment, albeit with reduced efficiency. In contrast, Sp3-/- cells showed no significant engraftment in the erythroid and myeloid lineages. Thus, the absence of Sp3 results in cell-autonomous hematopoietic defects, affecting in particular the erythroid and myeloid cell lineages.

scholarly journals Enhanced B Cell Expansion, Survival, and Humoral Responses by Targeting Death Receptor 6

2002 ◽  
Vol 197 (1) ◽  
pp. 51-62 ◽  
Author(s):  
Clint S. Schmidt ◽  
Jinqi Liu ◽  
Tonghai Zhang ◽  
Ho Yeong Song ◽  
George Sandusky ◽  
...  
Keyword(s):  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Cell Expansion ◽  
Death Receptor ◽  
Immunoglobulin M ◽  
Type I ◽  
Factor C

Targeted disruption of death receptor (DR)6 results in enhanced CD4+ T cell expansion and T helper cell type 2 differentiation after stimulation. Similar to T cells, DR6 is expressed on resting B cells but is down-regulated upon activation. We examined DR6−/− B cell responses both in vitro and in vivo. In vitro, DR6−/− B cells undergo increased proliferation in response to anti–immunoglobulin M, anti-CD40, and lipopolysaccharide. This hyperproliferative response was due, at least in part, to both increased cell division and reduced cell apoptosis when compared with wild-type B cells. Consistent with these observations, increased nuclear levels and activity of nuclear factor κB transcription factor, c-Rel, and elevated Bcl-xl expression were observed in DR6−/− B cells upon stimulation. In addition, DR6−/− B cells exhibited higher surface levels of CD86 upon activation and were more effective as antigen-presenting cells in an allogeneic T cell proliferation response. DR6−/− mice exhibited enhanced germinal center formation and increased titers of immunoglobulins to T-dependent as well as T-independent type I and II antigens. This is the first demonstration of a regulatory role of DR6 in the activation and function of B cells.

scholarly journals Blimp-1-Dependent Repression of Pax-5 Is Required for Differentiation of B Cells to Immunoglobulin M-Secreting Plasma Cells

2002 ◽  
Vol 22 (13) ◽  
pp. 4771-4780 ◽  
Author(s):  
Kuo-I Lin ◽  
Cristina Angelin-Duclos ◽  
Tracy C. Kuo ◽  
Kathryn Calame
Keyword(s):  
B Cells ◽  
B Cell ◽  
B Lymphocyte ◽  
Critical Role ◽  
Cell Lineage ◽  
Immunoglobulin M ◽  
Dependent Manner ◽  
Plasmacytic Differentiation

ABSTRACT B-cell lineage-specific activator protein (BSAP), encoded by the Pax-5 gene, is critical for B-cell lineage commitment and B-cell development but is not expressed in terminally differentiated B cells. We demonstrate a direct connection between BSAP and B-lymphocyte-induced maturation protein 1 (Blimp-1), a transcriptional repressor that is sufficient to drive plasmacytic differentiation. Blimp-1 binds a site on the Pax-5 promoter in vitro and in vivo and represses the Pax-5 promoter in a binding-site-dependent manner. By ectopically expressing Blimp-1 or a competitive inhibitor of Blimp-1, we show that Blimp-1 is both necessary and sufficient to repress Pax-5 during plasmacytic differentiation of primary splenic B cells. Blimp-1-dependent repression of Pax-5 is sufficient to regulate BSAP targets CD19 and J chain and is necessary but not sufficient to induce XBP-1. We further show that repression of Pax-5 is required for Blimp-1 to drive differentiation of splenocytes to immunoglobulin M-secreting cells. Thus, repression of Pax-5 plays a critical role in the Blimp-1-dependent program of plasmacytic differentiation.

scholarly journals Soluble and Membrane-bound Forms of Signaling Lymphocytic Activation Molecule (SLAM) Induce Proliferation and Ig Synthesis by Activated Human B Lymphocytes

1997 ◽  
Vol 185 (6) ◽  
pp. 993-1004 ◽  
Author(s):  
Juha Punnonen ◽  
Benjamin G. Cocks ◽  
José M. Carballido ◽  
Bruce Bennett ◽  
David Peterson ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Activation ◽  
B Cell Activation ◽  
Human B Cells ◽  
Membrane Bound ◽  
Signaling Lymphocytic Activation Molecule ◽  
Ig Synthesis ◽  
Activated B Cells

In this study it is shown that both membrane-bound and soluble forms of signaling lymphocytic activation molecule (SLAM) induce proliferation and Ig synthesis by activated human B cells. Activated B cells express the membrane-bound form of SLAM (mSLAM), the soluble (s) and the cytoplasmic (c) isoforms of SLAM, and the expression levels of mSLAM on B cells are rapidly upregulated after activation in vitro. Importantly, recombinant sSLAM and L cells transfected with mSLAM efficiently enhance B cell proliferation induced by anti-μ mAbs, anti-CD40 mAbs or Staphylococcus aureus Cowan I (SAC) in the presence or absence of IL-2, IL-4, IL-10, IL-12, or IL-15. sSLAM strongly enhances proliferation of both freshly isolated B cells and B cells derived from long-term in vitro cultures, indicating that SLAM acts not only during the initial phase of B cell activation but also during the expansion of preactivated B cells. In addition, sSLAM enhances production of IgM, IgG, and IgA by B cells activated by antiCD40 mAbs. SLAM has recently been shown to be a high affinity self-ligand, and the present data suggest that signaling through homophilic SLAM–SLAM binding during B–B and B–T cell interactions enhances the expansion and differentiation of activated B cells.

scholarly journals Function of B cells expressing a human immunoglobulin M rheumatoid factor autoantibody in transgenic mice.

1993 ◽  
Vol 177 (1) ◽  
pp. 109-118 ◽  
Author(s):  
H Tighe ◽  
P P Chen ◽  
R Tucker ◽  
T J Kipps ◽  
J Roudier ◽  
...  
Keyword(s):  
B Cells ◽  
Transgenic Mice ◽  
B Cell ◽  
Rheumatoid Factor ◽  
Significant Proportion ◽  
Immunoglobulin M ◽  
Major Function ◽  
Low Concentrations ◽  
Antigen Presenting

We have generated transgenic mice that express the immunoglobulin (Ig)M heavy chain and kappa light chain genes coding for a human IgM rheumatoid factor (RF), Les. Transgenic B cells expressing human IgM RF show striking similarities to their counterparts in normal humans. They comprise a significant proportion of the adult B cell population, but secrete only low levels of RF into the serum. The RF transgene-expressing B cells localize to primary B cell follicles and the mantle zone regions of secondary follicles in the spleen. Using these mice we have been able to show that one of the central functions of normal RF-expressing B cells may be to act as highly efficient antigen-presenting cells for low concentrations of immune-complexed antigen. High levels of secretion of IgM RF can not be induced under normal circumstances, although RF-expressing B cells proliferate well in vitro to both aggregated human IgG and anti-human IgM antibodies. However, these mice are not intrinsically secretion deficient. By crossing the RF transgenic mice with the autoimmune MRL/lpr background, we find a dramatic increase, > 200-fold, in levels of serum RF. The results strongly suggest that a major function of normal resting RF B cells is unrelated to antibody secretion. Rather, the RF B cells in the follicles may play a role in antigen presentation and regulation of immune responses to antibody-bound nonself-, and possibly self-antigens. This physiologic role of RF B cells may be disrupted in RF-associated autoimmune disease.

scholarly journals Plasmablasts derive from CD23-negative activated B cells after the extinction of IL-4/STAT6 signaling and IRF4 induction

Blood ◽  
2020 ◽  
Author(s):  
Amandine Pignarre ◽  
Fabrice Chatonnet ◽  
Gersende Caron ◽  
Marion Haas ◽  
Fabienne Desmots-Loyer ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Initial Response ◽  
Degradation Process ◽  
B Cell Differentiation ◽  
Similar Phenotype ◽  
Fate Decision ◽  
Activated B Cells

The terminal differentiation of B cells into antibody-secreting cells (ASCs) is a critical component of adaptive immune responses. However, it is a very sensitive process, which dysfunctions lead to a great variety of lymphoproliferative neoplasia including germinal center-derived lymphomas. To better characterize the late genomic events driving the ASC differentiation of human primary naive B cells, we used our in vitro differentiation system and a combination of RNA sequencing with ATAC-seq. Our results evidenced two mechanisms driving human terminal B cell differentiation. Firstly, after an initial response to IL-4, cells that committed to an ASC fate downregulated the CD23 marker and IL-4 signaling, whereas cells that maintained IL-4 signaling did not differentiate. Secondly, human CD23-negative cells also increased IRF4 protein to levels required for ASC differentiation, but independently of the ubiquitin-mediated degradation process previously described in the mouse. Finally, we showed that CD23-negative cells (i) carried the imprint of their previous activated B-cell status, (ii) were precursors of plasmablasts, and (iii) had a similar phenotype to in vivo pre-plasmablasts. Altogether, our results provide an unprecedented genomic characterization of the fate decision between activated B cells and plasmablast, which gives new insights in pathological mechanisms driving lymphoma biology.

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