scholarly journals Human lymphoma mutations reveal CARD11 as the switch between self-antigen–induced B cell death or proliferation and autoantibody production

2012 ◽  
Vol 209 (11) ◽  
pp. 1907-1917 ◽  
Author(s):  
Yogesh S. Jeelall ◽  
James Q. Wang ◽  
Hsei-Di Law ◽  
Heather Domaschenz ◽  
Herman K.H. Fung ◽  
...  
Keyword(s):  
Cell Death ◽  
B Cell ◽  
Antigen Receptors ◽  
Autoantibody Production ◽  
Molecular Change ◽  
Cell Responses ◽  
Self Tolerance ◽  
Human Lymphoma ◽  
Self Antigen

Self-tolerance and immunity are actively acquired in parallel through a poorly understood ability of antigen receptors to switch between signaling death or proliferation of antigen-binding lymphocytes in different contexts. It is not known whether this tolerance-immunity switch requires global rewiring of the signaling apparatus or if it can arise from a single molecular change. By introducing individual CARD11 mutations found in human lymphomas into antigen-activated mature B lymphocytes in mice, we find here that lymphoma-derived CARD11 mutations switch the effect of self-antigen from inducing B cell death into T cell–independent proliferation, Blimp1-mediated plasmablast differentiation, and autoantibody secretion. Our findings demonstrate that regulation of CARD11 signaling is a critical switch governing the decision between death and proliferation in antigen-stimulated mature B cells and that mutations in this switch represent a powerful initiator for aberrant B cell responses in vivo.

scholarly journals Activated PI3Kδ breaches multiple B cell tolerance checkpoints and causes autoantibody production

2019 ◽  
Vol 217 (2) ◽  
Author(s):  
Anthony Lau ◽  
Danielle T. Avery ◽  
Katherine Jackson ◽  
Helen Lenthall ◽  
Stefano Volpi ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Peripheral Tolerance ◽  
Gain Of Function ◽  
Autoantibody Production ◽  
Self Tolerance ◽  
A Cell ◽  
Phosphoinositide 3 Kinase ◽  
Self Antigen

Antibody-mediated autoimmune diseases are a major health burden. However, our understanding of how self-reactive B cells escape self-tolerance checkpoints to secrete pathogenic autoantibodies remains incomplete. Here, we demonstrate that patients with monogenic immune dysregulation caused by gain-of-function mutations in PIK3CD, encoding the p110δ catalytic subunit of phosphoinositide 3-kinase (PI3K), have highly penetrant secretion of autoreactive IgM antibodies. In mice with the corresponding heterozygous Pik3cd activating mutation, self-reactive B cells exhibit a cell-autonomous subversion of their response to self-antigen: instead of becoming tolerized and repressed from secreting autoantibody, Pik3cd gain-of-function B cells are activated by self-antigen to form plasmablasts that secrete high titers of germline-encoded IgM autoantibody and hypermutating germinal center B cells. However, within the germinal center, peripheral tolerance was still enforced, and there was selection against B cells with high affinity for self-antigen. These data show that the strength of PI3K signaling is a key regulator of pregerminal center B cell self-tolerance and thus represents a druggable pathway to treat antibody-mediated autoimmunity.

scholarly journals Apoptosis and in vivo models to study the molecules related to this phenomenon

2010 ◽  
Vol 8 (4) ◽  
pp. 495-497 ◽  
Author(s):  
Adriana Luchs ◽  
Claudia Pantaleão
Keyword(s):  
Cell Death ◽  
B Cell ◽  
Ectopic Expression ◽  
B Cell Lymphoma ◽  
Murine Models ◽  
In Vivo Models ◽  
Large B Cell Lymphoma ◽  
Pathological Conditions ◽  
Pharmacological Targets

ABSTRACT Apoptosis or programmed cell death is a physiological process, essential for eliminating cells in excess or that are no longer necessary to the organism, acting on tissue homeostasis, although the phenomenon is also involved in pathological conditions. Apoptosis promotes activation of biochemical pathways inside cells called caspase pathway, of the proteins responsible for the cleavage of several cell substrates, leading to cell death. Antiapoptotic members of the Bcl-2 family (B cell CLL/lymphoma 2), that belong to the intrinsic route of the activation of caspases, such as Bcl-xL (extra-large B-cell lymphoma) and Bcl-w (Bcl-2-like 2), act predominantly to prevent that pro-apoptotic members, such as Bax (Bcl-2-associated X protein) and Bak (Bcl-2 relative bak) lead to cell death. Antiapoptotic molecules are considered potentially oncogenic. Murine models are known to be valuable systems for the experimental analysis of oncogenes in vivo, and for the identification of pharmacological targets for cancer and to assess antitumor therapies. Given the importance of tumorigenesis studies on the immune responses to cancer and the possibility of investigating the participation of antiapoptotic molecules in tumor progression in vivo, the development of new models may be platforms for studies on tumorigenesis, immune antitumor responses, investigation of the ectopic expression of antiapoptotic molecules and immunotherapies for tumors.

scholarly journals Activation-induced cell death of self-reactive regulatory T cells drives autoimmunity

2019 ◽  
Vol 116 (52) ◽  
pp. 26788-26797
Author(s):  
Ester Badami ◽  
Olivier N. F. Cexus ◽  
Sonia Quaratino
Keyword(s):  
T Cells ◽  
Cell Death ◽  
Lymph Nodes ◽  
Autoimmune Thyroiditis ◽  
The Self ◽  
Thyroid Peroxidase ◽  
Activation Induced Cell Death ◽  
Self Antigen ◽  
Draining Lymph Nodes

Activation of self-reactive T cells is a major driver to autoimmunity and is suppressed by mechanisms of regulation. In a humanized model of autoimmune thyroiditis, we investigated the mechanism underlying break of tolerance. Here, we found that a human TCR specific for the self-antigen thyroid peroxidase (TPO) is positively selected in the thymus of RAG KO mice on both T effector (Teff) and T regulatory (Treg) CD4+Foxp3+cells. In vivo Teffare present in all immune organs, whereas the TPO-specific Tregare present in all lymphoid organs with the exception of the thyroid-draining lymph nodes. We suggest that the presence of TPO in the thyroid draining lymph nodes induces the activation of Teffand the depletion of Tregvia activation-induced cell death (AICD). Our findings provide insights on the failure of the mechanisms of immune tolerance, with potential implications in designing immunotherapeutic strategies.

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.

scholarly journals Interferon gamma inhibits apoptotic cell death in B cell chronic lymphocytic leukemia.

1993 ◽  
Vol 177 (1) ◽  
pp. 213-218 ◽  
Author(s):  
M Buschle ◽  
D Campana ◽  
S R Carding ◽  
C Richard ◽  
A V Hoffbrand ◽  
...  
Keyword(s):  
Cell Death ◽  
Chronic Lymphocytic Leukemia ◽  
Programmed Cell Death ◽  
B Cell ◽  
Interferon Gamma ◽  
Lymphocytic Leukemia ◽  
Malignant Cells ◽  
Ifn Gamma ◽  
Cell Chronic Lymphocytic Leukemia

The malignant, CD5+ B lymphocytes of B cell chronic lymphocytic leukemia (B-CLL) die by apoptosis in vitro. This is in contrast to the prolonged life span of the leukemic cells in vivo and likely reflects the lack of essential growth factors in the tissue culture medium. We found that interferon gamma (IFN-gamma) inhibits programmed cell death and promotes survival of B-CLL cells in culture. This effect may also be important in vivo: increased serum levels of IFN-gamma, ranging from 60 to > 2,200 pg/ml, were found in 7 of 10 B-CLL samples tested, whereas the sera of 10 healthy individuals did not contain detectable levels of this cytokine (< 20 pg/ml). High levels of IFN-gamma message were detected in RNA from T cell-depleted B-CLL peripheral blood samples by Northern blot analysis. Synthesis of IFN-gamma by B-CLL lymphocytes was confirmed by in situ hybridization and flow cytometry. The majority of B-CLL cells (74-82%) expressed detectable levels of IFN-gamma mRNA, and CD19+ B-CLL cells were labeled with anti-IFN-gamma monoclonal antibodies. These results show that IFN-gamma inhibits programmed cell death in B-CLL cells and suggest that the malignant cells are able to synthesize this cytokine. By delaying apoptosis, IFN-gamma may extend the life span of the malignant cells and thereby contribute to their clonal accumulation.

scholarly journals Immunoglobulin M and D antigen receptors are both capable of mediating B lymphocyte activation, deletion, or anergy after interaction with specific antigen.

1992 ◽  
Vol 176 (4) ◽  
pp. 991-1005 ◽  
Author(s):  
R Brink ◽  
C C Goodnow ◽  
J Crosbie ◽  
E Adams ◽  
J Eris ◽  
...  
Keyword(s):  
T Cell ◽  
B Cells ◽  
Transgenic Mice ◽  
B Lymphocyte ◽  
Specific Antigen ◽  
Antigen Receptors ◽  
Antigen B ◽  
Self Antigen ◽  
Clonal Anergy

A series of immunoglobulin (Ig)-transgenic mice were generated to study the functional capabilities of the IgM and IgD classes of B lymphocyte antigen receptor in regulating both cellular development and responses to specific antigen. B cells from Ig-transgenic mice expressing either hen-egg lysozyme (HEL)-specific IgM or IgD alone were compared with B cells from mice that coexpressed IgM and IgD of the same anti-HEL specificity. In all three types of Ig-transgenic mice, conventional B cells specific for HEL exhibited exclusion of endogenous Ig expression and matured to populate the usual microenvironments in peripheral lymphoid tissues. These peripheral B cells could be stimulated by HEL through either IgM or IgD antigen receptors to generate T cell dependent antibody production in vivo or to enhance T cell independent proliferative responses to lipopolysaccharide in vitro. Conversely, when HEL was encountered in vivo as a self-antigen, B cells expressing HEL-specific IgM or IgD alone were both rendered tolerant. In each case this occurred by clonal anergy in response to soluble autologous HEL, and clonal deletion when HEL was recognized as a membrane-bound self-antigen. Taken together, these findings indicate that IgM and IgD antigen receptors expressed alone on conventional B cells can support normal differentiation, antigen-dependent activation, and induction of self-tolerance, the only overt difference lying in a greater degree of receptor downregulation for IgM relative to IgD after induction of clonal anergy by soluble HEL.

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