scholarly journals The Viral Latency-Associated Nuclear Antigen Augments the B-Cell Response to Antigen In Vivo

2010 ◽  
Vol 84 (20) ◽  
pp. 10653-10660 ◽  
Author(s):  
Sang-Hoon Sin ◽  
Farnaz D. Fakhari ◽  
Dirk P. Dittmer
Keyword(s):  
B Cells ◽  
B Cell ◽  
Knockout Mice ◽  
Marginal Zone ◽  
Viral Latency ◽  
Kaposi Sarcoma ◽  
Cell Receptor ◽  
Selective Advantage ◽  
Nuclear Antigen

ABSTRACT Gammaherpesviruses, including Kaposi sarcoma-associated herpesvirus (KSHV), establish latency in B cells. We hypothesized that the KSHV latency-associated nuclear antigen (LANA/orf73) provides a selective advantage to infected B cells by driving proliferation in response to antigen. To test this, we used LANA B-cell transgenic mice. Eight days after immunization with antigen without adjuvant, LANA mice had significantly more activated germinal center (GC) B cells (CD19+ PNA+ CD71+) than controls. This was dependent upon B-cell receptor since LANA did not restore the GC defect of CD19 knockout mice. However, LANA was able to restore the marginal zone defect in CD19 knockout mice.

scholarly journals WASP confers selective advantage for specific hematopoietic cell populations and serves a unique role in marginal zone B-cell homeostasis and function

Blood ◽  
2008 ◽  
Vol 112 (10) ◽  
pp. 4139-4147 ◽  
Author(s):  
Lisa S. Westerberg ◽  
Miguel A. de la Fuente ◽  
Fredrik Wermeling ◽  
Hans D. Ochs ◽  
Mikael C. I. Karlsson ◽  
...  
Keyword(s):  
T Cells ◽  
B Cells ◽  
B Cell ◽  
Marginal Zone ◽  
Hematopoietic Cells ◽  
Selective Advantage ◽  
Relative Contribution ◽  
B Cell Homeostasis ◽  
And Function

Abstract Development of hematopoietic cells depends on a dynamic actin cytoskeleton. Here we demonstrate that expression of the cytoskeletal regulator WASP, mutated in the Wiskott-Aldrich syndrome, provides selective advantage for the development of naturally occurring regulatory T cells, natural killer T cells, CD4+ and CD8+ T lymphocytes, marginal zone (MZ) B cells, MZ macrophages, and platelets. To define the relative contribution of MZ B cells and MZ macrophages for MZ development, we generated wild-type and WASP-deficient bone marrow chimeric mice, with full restoration of the MZ. However, even in the presence of MZ macrophages, only 10% of MZ B cells were of WASP-deficient origin. We show that WASP-deficient MZ B cells hyperproliferate in vivo and fail to respond to sphingosine-1-phosphate, a crucial chemoattractant for MZ B-cell positioning. Abnormalities of the MZ compartment in WASP−/− mice lead to aberrant uptake of Staphylococcus aureus and to a reduced immune response to TNP-Ficoll. Moreover, WASP-deficient mice have increased levels of “natural” IgM antibodies. Our findings reveal that WASP regulates both development and function of hematopoietic cells. We demonstrate that WASP deficiency leads to an aberrant MZ that may affect responses to blood-borne pathogens and peripheral B-cell tolerance.

scholarly journals Viral latency locus augments B-cell response in vivo to induce chronic marginal zone enlargement, plasma cell hyperplasia, and lymphoma

Blood ◽  
2013 ◽  
Vol 121 (15) ◽  
pp. 2952-2963 ◽  
Author(s):  
Sang-Hoon Sin ◽  
Dirk P. Dittmer
Keyword(s):  
Cell Proliferation ◽  
Transgenic Mice ◽  
B Cell ◽  
Cell Response ◽  
Marginal Zone ◽  
Viral Latency ◽  
Kaposi Sarcoma ◽  
Cell Hyperplasia ◽  
Key Points

Key PointsKaposi sarcoma associated herpesvirus miRNAs and latent proteins drive B-cell proliferation. Viral miRNAs and latent proteins induce BCR and TLR hyper-responsivness in transgenic mice.

Vav proteins regulate peripheral B-cell survival

Blood ◽  
2005 ◽  
Vol 106 (7) ◽  
pp. 2391-2398 ◽  
Author(s):  
Elena Vigorito ◽  
Laure Gambardella ◽  
Francesco Colucci ◽  
Simon McAdam ◽  
Martin Turner
Keyword(s):  
B Cells ◽  
B Cell ◽  
Marginal Zone ◽  
Cell Receptor ◽  
Cross Linking ◽  
Marginal Zone B Cells ◽  
Survival Signal ◽  
B Cell Survival ◽  
Follicular B Cells ◽  
Deficient Mice

AbstractMice lacking all 3 Vav proteins fail to produce significant numbers of recirculating follicular or marginal zone B cells. Those B cells that do mature have shortened lifespans. The constitutive nuclear factor-kappaB (NF-κB) activity of resting naive B cells required Vav function and expression of cellular reticuloendotheliosis (c-Rel). Rel-A was reduced in Vav-deficient B cells. Furthermore, expression of the NF-κB-regulated antiapoptotic genes A1 and Bcl-2 was reduced in mature Vav-deficient B cells. Overexpression of Bcl-2 restored the number of mature follicular B cells in the spleens of Vav-deficient mice. When activated by B-cell receptor (BCR) cross-linking, Vav-deficient B cells failed to activate NF-κB. Vav proteins thus regulate an NF-κB-dependent survival signal in naive B cells and are required for NF-κB function after BCR cross-linking.

scholarly journals A Gammaherpesvirus Bcl-2 Ortholog Blocks B Cell Receptor-Mediated Apoptosis and Promotes the Survival of Developing B Cells In Vivo

2014 ◽  
Vol 10 (2) ◽  
pp. e1003916 ◽  
Author(s):  
Carrie B. Coleman ◽  
Jennifer E. McGraw ◽  
Emily R. Feldman ◽  
Alexa N. Roth ◽  
Lisa R. Keyes ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Receptor ◽  
B Cell Receptor

scholarly journals Epstein-Barr Virus LMP2A Alters In Vivo and In Vitro Models of B-Cell Anergy, but Not Deletion, in Response to Autoantigen

2005 ◽  
Vol 79 (12) ◽  
pp. 7355-7362 ◽  
Author(s):  
Michelle A. Swanson-Mungerson ◽  
Robert G. Caldwell ◽  
Rebecca Bultema ◽  
Richard Longnecker
Keyword(s):  
B Cells ◽  
B Cell ◽  
Epstein Barr Virus ◽  
Nuclear Translocation ◽  
Cell Receptor ◽  
Barr Virus ◽  
Low Levels ◽  
Epstein Barr

ABSTRACT A significant percentage of the population latently harbors Epstein-Barr virus (EBV) in B cells. One EBV-encoded protein, latent membrane protein 2A (LMP2A), is expressed in tissue culture models of EBV latent infection, in human infections, and in many of the EBV-associated proliferative disorders. LMP2A constitutively activates proteins involved in the B-cell receptor (BCR) signal transduction cascade and inhibits the antigen-induced activation of these proteins. In the present study, we investigated whether LMP2A alters B-cell receptor signaling in primary B cells in vivo and in vitro. LMP2A does not inhibit antigen-induced tolerance in response to strong stimuli in an in vivo tolerance model in which B cells are reactive to self-antigen. In contrast, LMP2A bypasses anergy induction in response to low levels of soluble hen egg lysozyme (HEL) both in vivo and in vitro as determined by the ability of LMP2A-expressing HEL-specific B cells to proliferate and induce NF-κB nuclear translocation after exposure to low levels of antigen. Furthermore, LMP2A induces NF-κB nuclear translocation independent of BCR cross-linking. Since NF-κB is required to bypass tolerance induction, this LMP2A-dependent NF-κB activation may complete the tolerogenic signal induced by low levels of soluble HEL. Overall, the findings suggest that LMP2A may not inhibit BCR-induced signals under all conditions as previously suggested by studies with EBV immortalized B cells.

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.

Cas-L/Hef1 Is Required for Marginal Zone B Cell Maintenance and Lymphocyte Trafficking.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3920-3920
Author(s):  
Sachiko Seo ◽  
Takashi Asai ◽  
Toshiki Saito ◽  
Takahiro Suzuki ◽  
Motoshi Ichikawa ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Marginal Zone ◽  
Cell Receptor ◽  
Cell Number ◽  
Lymphoid Organs ◽  
Adhesion Assay ◽  
Lymphocyte Migration ◽  
Lymphocyte Trafficking ◽  
Deficient Mice

Abstract Cas-L (Crk-associated substrate lymphocyte type) which is also known as Hef1 (human enhancer of filamentation 1) was first identified as a protein tyrosine-phosphorylated upon stimulation of b1 integrin. Cas-L possesses a single Src homology (SH) 3 domain and multiple YXXP motifs (substrate domain) as a member of Cas protein family, and is well expressed in peripheral lymphocytes. Previous studies suggest that Cas-L might be involved in Bcr-Abl positive leukemia and adult T cell leukemia. However, the biological function of Cas-L in lymphocytes is little known. We generated Cas-L-deficient mice using a gene targeting strategy. The mice showed a deficit of marginal zone (MZ) B cells and a decrease of cell number in secondary lymphoid organs. To elucidate the mechanism of the MZ B cell defect, the reciprocal bone marrow transfer assays were performed. The results revealed that the defect of MZ B cells in Cas-L-deficient mice is cell autonomous. Next, we analyzed B cell receptor signaling by measurement of intracellular Ca2+ concentration and lymphocyte proliferation. However, we could not find any significant differences between wild type and Cas-L-deficient mice. Cas-L-deficient lymphocytes showed reduced chemotactic response to CXCL12 and CXCL13. The adhesion assay also showed the decreased adhesiveness to VCAM-1 and ICAM-1, which are important for retention of MZ B cells in spleen. Moreover, we found that the lymphocyte trafficking to spleen and lymph nodes was altered in Cas-L-deficient mice. Thus, Cas-L affects homeostasis of MZ B cells and peripheral lymphoid organs, which is considered to be relevant to impaired lymphocyte migration and adhesion.

Enhanced B Cell Activation in the Absence of CD81

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 2578-2578
Author(s):  
Mrinmoy Sanyal ◽  
Rosemary Fernandez ◽  
Shoshana Levy
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Activation ◽  
Cell Receptor ◽  
Free Calcium ◽  
B Cell Activation ◽  
Membrane Reorganization ◽  
A Cell

Abstract CD81 is a component of the CD19/CD21 coreceptor complex in B cells. This tetraspanin molecule was previously shown to enable membrane reorganization in B cells responding to complement-bound antigens. Here we stimulated B cells via their B cell receptor (BCR) and demonstrate that Cd81−/− B cells fluxed higher intracellular free calcium ion along with increased phosphorylation of PLCγ2 and Syk. The stimulated Cd81−/− B cells also proliferated faster and secreted higher amounts of antibodies. Moreover, activation of the TLR4 pathway in Cd81−/− B cells induced increased proliferation and antibody secretion. Furthermore, Cd81−/− mice mounted a significantly higher immune response to T-cell independent antigens than their wildtype counterparts. Finally, analysis of Cd81−/− B cells that were generated by bone marrow transplantation into Rag1−/− mice confirmed a cell intrinsic hyperactive phenotype. Taken together, these results indicate that CD81 plays a negative role in B cell activation in vitro and in vivo.

scholarly journals The LMP2A ITAM Is Essential for Providing B Cells with Development and Survival Signals In Vivo

2000 ◽  
Vol 74 (19) ◽  
pp. 9115-9124 ◽  
Author(s):  
Mark Merchant ◽  
Robert G. Caldwell ◽  
Richard Longnecker
Keyword(s):  
B Cells ◽  
Transgenic Mice ◽  
B Cell ◽  
Tyrosine Kinases ◽  
Cell Receptor ◽  
Lytic Replication ◽  
Barr Virus ◽  
Bcr Signaling ◽  
Survival Signals

ABSTRACT In Epstein-Barr virus-transformed B cells, known as lymphoblastoid cell lines (LCLs), LMP2A binds the tyrosine kinases Syk and Lyn, blocking B-cell receptor (BCR) signaling and viral lytic replication. SH2 domains in Syk mediate binding to a phosphorylated immunoreceptor tyrosine-based activation motif (ITAM) in LMP2A. Mutation of the LMP2A ITAM in LCLs eliminates Syk binding and allows for full BCR signaling, thereby delineating the significance of the LMP2A-Syk interaction. In transgenic mice, LMP2A causes a developmental alteration characterized by a block in surface immunoglobulin rearrangement resulting in BCR-negative B cells. Normally B cells lacking cognate BCR are rapidly apoptosed; however, LMP2A transgenic B cells develop and survive without a BCR. When bred into the recombinase activating gene 1 null (RAG−/−) background, all LMP2A transgenic lines produce BCR-negative B cells that develop and survive in the periphery. These data indicate that LMP2A imparts developmental and survival signals to B cells in vivo. In this study, LMP2A ITAM mutant transgenic mice were generated to investigate whether the LMP2A ITAM is essential for the survival phenotype in vivo. LMP2A ITAM mutant B cells develop normally, although transgene expression is comparable to that in previously described nonmutated LMP2A transgenic B cells. Additionally, LMP2A ITAM mutant mice are unable to promote B-cell development or survival when bred into the RAG−/− background or when grown in methylcellulose containing interleukin-7. These data demonstrate that the LMP2A ITAM is required for LMP2A-mediated developmental and survival signals in vivo.

Sign in / Sign up

Export Citation Format

Share Document