scholarly journals Role of C'3 and Fc receptors in B-lymphocyte activation.

1975 ◽  
Vol 141 (3) ◽  
pp. 647-663 ◽  
Author(s):  
G Möller ◽  
A Coutinho
Keyword(s):  
B Cells ◽  
B Cell ◽  
Polyclonal Antibody ◽  
B Lymphocyte ◽  
Fc Receptors ◽  
Lymphocyte Activation ◽  
Antibody Synthesis ◽  
B Lymphocyte Activation ◽  
Cell Induction

Attempts were made to identify the non-Ig lymphocyte receptor responsible for B-cell induction by antigen and polyclonal B-cell activators (PBA). As a first step, the role of C'3 and Fc receptors was analyzed. It was shown that complement could be fixed onto B cells to such an extent that the lymphocytes could not bind complement-coated red cells, but this did not result in induction of polyclonal antibody synthesis, nor did it inhibit the lymphocytes response to PBA. However, the C'3 receptros possessed a passive focussing role in the induction of polyclonal antibody responses. Thus, PBA that had fixed complement activated polyclonal responses at lower concentrations than the same substances that had not fixed complement. Most likely the dual binding of PBA molecules to B cells by the PBA and the C'3 receptors caused more PBA molecules to be bound to each cell. However, the focussing function of the C'3 receptors was several orders of magnitude smaller than that of the Ig receptors. Analogous studies were carried out with Fc receptors. Binding of different types of antigen-antibody complexes did not cause activation of polyclonal or specific antibody synthesis, nor did it significantly interfere with induction of antibody synthesis by PBA substances.

Role of B-Lymphocyte Stimulator (BLyS) in Waldenstrom’s Macroglobulinemia.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 601-601
Author(s):  
Sherine F. Elsawa ◽  
Anne J. Novak ◽  
Deanna M. Grote ◽  
Steven C. Zeismer ◽  
Thomas E. Witzig ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
B Lymphocyte ◽  
Waldenström’S Macroglobulinemia ◽  
Immunoglobulin Production ◽  
B Lymphocyte Stimulator ◽  
Waldenstrom's Macroglobulinemia ◽  
Waldenstrom’S Macroglobulinemia ◽  
Waldenström's Macroglobulinemia

Abstract Waldenstrom’s macroglobulinemia (WM) is a serious and frequently fatal disorder characterized by the production of a monoclonal IgM protein, a lymphoplasmacytic infiltrate in the bone marrow, and associated symptoms including anemia, lymphadenopathy and hyperviscosity. Many of the mechanisms leading to this disease are not yet known. It is clear, however, that there is dysregulation of the balance between cell proliferation and programmed cell death. BLyS (B-lymphocyte stimulator) is a TNF family member expressed by monocytes, neutrophils, macrophages, and dendritic cells. BLyS has been shown to be critical for maintenance of normal B cell development and homeostasis, and has been found to stimulate lymphocyte growth. BLyS is overexpressed in a variety of B-cell malignancies and has been shown to inhibit apoptosis in malignant B-cells. Studies of the effects of BLyS on B cell physiology have shown that it also regulates immunoglobulin secretion. In previous work, we have shown that malignant B cells from patients with WM are able to bind soluble BLyS and variably express the BLyS receptors, BAFF-R, TACI and BCMA. We also found expression of BLyS in bone marrow specimens by immunohistochemistry and elevated serum BLyS levels in patients with WM. The goal of this study was to determine the functional role of BLyS-receptor ligand system in Waldenstrom’s macroglobulinemia and its relevance to the increased immunoglobulin production seen in this disease. Using cells from WM patients, we first examined the ability of BLyS to increase the secretion of IgM by malignant B cells. BLyS, alone or in combination with cytokines that induce plasmacytic differentiation and immunoglobulin production (IL-2, IL-6, IL-10 and IL-12), was found to increase IgM secretion by malignant B cells. Mean baseline IgM levels significantly increased in cells treated with BLyS (p=0.03), cytokines (p=0.0002) and a combination of BLyS and cytokines (p<0.0001). We then determined the effect of BLyS on the survival of malignant B cells using Annexin-V/PI staining. Compared to cells cultured in media alone, BLyS was found to increase viability of malignant B cells from WM patients. Cell viability was normalized relative to the media-alone control and the median relative viability increased significantly compared to controls (median increase 41.2%; range 8 – 46%). Next, we examined the ability of BLyS to modulate cell proliferation using thymidine incorporation. Using WM patient samples, BLyS was found to significantly enhance the proliferation of malignant B cells (p=0.0002). Furthermore, addition of anti-Ig antibody further enhanced the ability of BLyS to promote the proliferation of malignant B cells (p<0.0001). In summary, we have demonstrated that BLyS enhances IgM secretion by malignant B cells from patients with Waldenstrom’s macroglobulinemia. We have also demonstrated the ability of BLyS to enhance the survival and proliferation of malignant B cells. Strategies to inhibit BLyS may potentially have therapeutic efficacy in Waldenstrom’s macroglobulinemia.

scholarly journals Antigen-induced B lymphocyte activation involves the p21ras and ras.GAP signaling pathway.

1993 ◽  
Vol 178 (5) ◽  
pp. 1765-1769 ◽  
Author(s):  
A H Lazarus ◽  
K Kawauchi ◽  
M J Rapoport ◽  
T L Delovitch
Keyword(s):  
B Cells ◽  
B Cell ◽  
Signaling Pathway ◽  
Tyrosine Phosphorylation ◽  
Cell Activation ◽  
B Lymphocyte ◽  
Lymphocyte Activation ◽  
Nucleotide Exchange ◽  
Western Blots ◽  
B Lymphoma

Ligation of a B lymphocyte surface immunoglobulin (sIg) antigen receptor (AgR) by its specific Ag ligand initiates a signaling pathway that culminates in B cell activation. However, many events of this pathway have not been elucidated. Here we present three novel findings that demonstrate directly that AgR-mediated signaling in B cells functions by the p21ras/ras.GAP-dependent pathway. First, stimulation of TA3 7.9 Ag-specific murine B lymphoma cells for 2 min with either Ag or F(ab')2 anti-IgM induces p21ras activation as measured by an increase in the GTP/GDP ratio of its bound nucleotides. This activation of p21ras does not occur via a change in its guanine nucleotide exchange rate. Second, Ag stimulation results in the inhibition of activity of p120 ras.GAP, a protein that regulates p21ras activation. Tyrosine phosphorylation of ras.GAP occurs within 1 min after Ag stimulation but is no longer detectable at 20 min after stimulation, at which time ras.GAP activity remains inhibited. Thus, tyrosine phosphorylation of ras.GAP is not required for the inhibition of its activity. Third, despite the role proposed for a ras.GAP-associated p190 protein in the control of ras.GAP activity in B cells, p190 was not detectable either in anti-ras.GAP immunoprecipitates of [35S]methionine labeled lysates of Ag-stimulated or -unstimulated 7.9 cells or as a tyrosine phosphoprotein in Western blots of anti-ras.GAP immunoprecipitates of Ag-stimulated 7.9 cell lysates. Inasmuch as the TA3 7.9 B lymphoma is representative of a mature, sIgM-bearing B cell, our observations raise the intriguing possibility that the capacity of p190 to associate with ras.GAP and regulate the activities of ras.GAP and p21ras in a B cell is dependent on the stage of differentiation of the B cell.

Regulation of B-lymphocyte activation by the PH domain adaptor protein Bam32/DAPP1

2007 ◽  
Vol 35 (2) ◽  
pp. 181-182 ◽  
Author(s):  
A.J. Marshall ◽  
T. Zhang ◽  
M. Al-Alwan
Keyword(s):  
B Cell ◽  
B Lymphocyte ◽  
Second Messengers ◽  
Lymphocyte Activation ◽  
Adaptor Protein ◽  
Cell Receptor ◽  
Pleckstrin Homology Domain ◽  
Ph Domain ◽  
B Lymphocyte Activation ◽  
Signal Transduction Proteins

PI3Ks (phosphoinositide 3-kinases) play critical roles in BCR (B-cell receptor) signalling via the generation of 3-phosphoinositide second messengers. Recruitment of PH domain (pleckstrin homology domain)-containing signal transduction proteins to the plasma membrane through binding to 3-phosphoinositide second messengers represents a major effector mechanism for PI3Ks. Here, we review data on the PH domain-containing adaptor protein Bam32 (B-cell adaptor molecule of 32 kDa)/DAPP1 (dual adaptor for phosphotyrosine and 3-phosphoinositides 1), focusing on its functions in B-lymphocyte activation. Present results support the view that Bam32/DAPP1 mediates multiple PI3K-dependent responses in B-cells through membrane-proximal mechanisms involving Src kinases, Rac1, F-actin and mitogen-activated protein kinases, resulting in selective effects on BCR-mediated proliferation, antigen presentation and generation of antibody responses.

scholarly journals B-cell-stimulatory factor 1 reverses Fc receptor-mediated inhibition of B-lymphocyte activation.

1987 ◽  
Vol 84 (17) ◽  
pp. 6254-6258 ◽  
Author(s):  
A. O'Garra ◽  
K. P. Rigley ◽  
M. Holman ◽  
J. B. McLaughlin ◽  
G. G. Klaus
Keyword(s):  
B Cell ◽  
B Lymphocyte ◽  
Lymphocyte Activation ◽  
Fc Receptor ◽  
B Lymphocyte Activation ◽  
Stimulatory Factor

scholarly journals Comparative In Vitro Immune Stimulation Analysis of Primary Human B Cells and B Cell Lines

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Kristien Van Belle ◽  
Jean Herman ◽  
Louis Boon ◽  
Mark Waer ◽  
Ben Sprangers ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Lines ◽  
Cell Activation ◽  
B Lymphocyte ◽  
Cell Model ◽  
Lymphocyte Activation ◽  
Screening Assay ◽  
Human B Cells

B cell specific immunomodulatory drugs still remain an unmet medical need. Utilisation of validated simplified in vitro models would allow readily obtaining new insights in the complexity of B cell regulation. For this purpose we investigated which human B lymphocyte stimulation assays may be ideally suited to investigate new B lymphocyte immunosuppressants. Primary polyclonal human B cells underwent in vitro stimulation and their proliferation, production of immunoglobulins (Igs) and of cytokines, and expression of cell surface molecules were analysed using various stimuli. ODN2006, a toll-like receptor 9 (TLR9) agonist, was the most potent general B cell stimulus. Subsequently, we investigated on which human B cell lines ODN2006 evoked the broadest immunostimulatory effects. The Namalwa cell line proved to be the most responsive upon TLR9 stimulation and hence may serve as a relevant, homogeneous, and stable B cell model in an in vitro phenotypic assay for the discovery of new targets and inhibitors of the B cell activation processes. As for the read-out for such screening assay, it is proposed that the expression of activation and costimulatory surface markers reliably reflects B lymphocyte activation.

scholarly journals Regulation of B Lymphocyte Development by Histone H2A Deubiquitinase BAP1

2021 ◽  
Vol 12 ◽  
Author(s):  
Yun Hsiao Lin ◽  
Yue Liang ◽  
HanChen Wang ◽  
Lin Tze Tung ◽  
Michael Förster ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Cycle Progression ◽  
B Lymphocyte ◽  
Cell Development ◽  
B Cell Development ◽  
Lymphocyte Development ◽  
A Cell ◽  
B Lymphocyte Development

BAP1 is a deubiquitinase (DUB) of the Ubiquitin C-terminal Hydrolase (UCH) family that regulates gene expression and other cellular processes, via deubiquitination of histone H2AK119ub and other substrates. BAP1 is an important tumor suppressor in human, expressed and functional across many cell-types and tissues, including those of the immune system. B lymphocytes are the mediators of humoral immune response, however the role of BAP1 in B cell development and physiology remains poorly understood. Here we characterize a mouse line with a selective deletion of BAP1 within the B cell lineage (Bap1fl/fl mb1-Cre) and establish a cell intrinsic role of BAP1 in the regulation of B cell development. We demonstrate a depletion of large pre-B cells, transitional B cells, and mature B cells in Bap1fl/fl mb1-Cre mice. We characterize broad transcriptional changes in BAP1-deficient pre-B cells, map BAP1 binding across the genome, and analyze the effects of BAP1-loss on histone H2AK119ub levels and distribution. Overall, our work establishes a cell intrinsic role of BAP1 in B lymphocyte development, and suggests its contribution to the regulation of the transcriptional programs of cell cycle progression, via the deubiquitination of histone H2AK119ub.

scholarly journals Control of B-lymphocyte function. I. Inactivation of mitogenesis by interactions with surface immunoglobulin and Fc-receptor molecules.

1976 ◽  
Vol 144 (4) ◽  
pp. 882-896 ◽  
Author(s):  
C L Sidman ◽  
E R Unanue
Keyword(s):  
B Cells ◽  
B Cell ◽  
B Lymphocyte ◽  
Regulatory Mechanism ◽  
Fc Receptor ◽  
Mouse Spleen ◽  
Lymphocyte Function ◽  
Spleen Cells ◽  
Surface Immunoglobulin

Mouse spleen cells were incubated with anti-Ig antibodies for 1 h, washed, exposed to LPS for 1 h, washed, and their DNA synthetic responses assayed 2 days later. It was shown that the 1-h incubation with anti-Ig antibodies produced a profound, internal, and long lasting state of inactivation in the B cells. Experiments with anti-Ig fragments and other ligands showed that the inactivation occurred optimally when both surface Ig molecules and Fc receptors were bound simultaneously. The role of the classical capping and clearing cycle was also investigated. It was shown that capping and clearing were neither necessary nor sufficient for the inactivation to occur, and that the signals, but only secondarily the ligands themselves, were transmitted across the membrane. Capping and clearing were viewed as a natural regulatory mechanism by which the B cell attempts to clear its membrane of perturbations and signals from the exterior.

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