scholarly journals A Crucial Role for the p110δ Subunit of Phosphatidylinositol 3-Kinase in B Cell Development and Activation

2002 ◽  
Vol 196 (6) ◽  
pp. 753-763 ◽  
Author(s):  
Elizabeth Clayton ◽  
Giuseppe Bardi ◽  
Sarah E. Bell ◽  
David Chantry ◽  
C. Peter Downes ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Critical Role ◽  
Cell Receptor ◽  
Calcium Flux ◽  
Phosphatidylinositol 3 Kinase ◽  
Marginal Zone B Cells ◽  
B Cell Homeostasis ◽  
Phosphatidylinositol 3

Mice lacking the p110δ catalytic subunit of phosphatidylinositol 3-kinase have reduced numbers of B1 and marginal zone B cells, reduced levels of serum immunoglobulins, respond poorly to immunization with type II thymus-independent antigen, and are defective in their primary and secondary responses to thymus-dependent antigen. p110δ−/− B cells proliferate poorly in response to B cell receptor (BCR) or CD40 signals in vitro, fail to activate protein kinase B, and are prone to apoptosis. p110δ function is required for BCR-mediated calcium flux, activation of phosphlipaseCγ2, and Bruton's tyrosine kinase. Thus, p110δ plays a critical role in B cell homeostasis and function.

RhoH-Deficient Mice Show Altered B Cell Populations In Vivo.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 2307-2307
Author(s):  
Abel Sanchez-Aguilera ◽  
Jose Cancelas ◽  
David A. Williams
Keyword(s):  
Bone Marrow ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Marginal Zone ◽  
Cell Receptor ◽  
Wild Type ◽  
Marginal Zone B Cells

Abstract RhoH is a GTPase-deficient, hematopoietic-specific member of the family of Rho GTPases (Li et al, 2002). RhoH has been described as regulating proliferation and engraftment of hematopoietic progenitor cells (Gu et al, 2005) and integrin-mediated adhesion in T cells (Cherry et al, 2004). Additionally, RhoH plays a critical role in T-cell development and T-cell receptor signaling (Gu et al, 2006; Dorn et al, 2007). However, the potential role of RhoH in the differentiation and biological functions of B cells are unknown. To answer these questions, we analyzed the B-cell phenotype of RhoH−/− mice and the in vitro properties of RhoH-deficient splenic B cells compared to their wild-type counterparts. RhoH−/− mice showed increased B-cell numbers in the bone marrow, mainly due to an increase in the number of pro-B, pre-B and immature B cells. In the spleen, lymph nodes and peripheral blood, RhoH−/− mice showed a significant decrease in the number of follicular (B-2) cells (B220+ CD93– IgDhigh CD21low). The number of splenic marginal zone B cells (B220+ CD93– IgDlow CD21high), plasma cells (CD93– CD38+ CD138+) in bone marrow and spleen, and B-1 cells (IgM+ CD5+) in peritoneal cavity were not significantly different from those in wild-type animals. These alterations have functional significance, since the serum concentrations of IgM and IgG1 were significantly lower in RhoH−/− mice. However, splenic B cells isolated from RhoH−/− mice did not show any significant differences in their in vitro activation by anti-IgM, CD40 ligation or IL-4 stimulation, nor did they differ in their proliferative response to lipopolysaccharide. In vitro migration of RhoH-deficient B cells in response to CXCL12 or CXCL13 was similar to that of wild-type B cells. Given the important role of RhoH in signal transduction downstream the T cell receptor, we investigated the possible role of RhoH in B cell receptor signaling. Although total splenic B cells from RhoH−/− mice showed markedly increased phosphorylation of SYK and ERK after anti-IgM stimulation compared to wild-type B cells, sorted populations of splenic B-2 and marginal zone B cells from RhoH−/− and wild-type animals did not differ in the activation of these kinases, suggesting that the observed difference can be attributed to the different cellular composition of the B cell compartment (i.e. B-2 vs marginal zone B cells) in RhoH−/− mice. These data imply that the phenotype observed in RhoH−/− mice may not reflect an intrinsic defect in B cells but may be attributed to crosstalk between B cells and other hematopoietic cell populations. Composition of B cell subsets in wild-type and RhoH−/− mice (total cell number ×106, ± standard deviation, N=9) Bone marrow Spleen (*) indicates p<0.05; (**), p<0.01; (***), p<0.005 RhoH+/+ RhoH−/− RhoH+/+ RhoH−/− total B cells 7.8±1.8 11.0±2.4 (**) total B cells 31.7±10.1 25.4±8.8 pro-B 0.12±0.03 0.15±0.04 (*) transitional 8.7±1.2 8.6±2.8 pre-B 2.6±0.6 3.8±0.8 (***) B-2 11.6±4.1 7.6±2.5 (*) immature 1.5±0.4 2.1±0.5 (*) marginal 3.2±1.1 3.9±1.6 mature 1.4±0.7 1.7±0.9

Ligation of tumour-produced mucins to CD22 dramatically impairs splenic marginal zone B-cells

2009 ◽  
Vol 417 (3) ◽  
pp. 673-683 ◽  
Author(s):  
Munetoyo Toda ◽  
Risa Hisano ◽  
Hajime Yurugi ◽  
Kaoru Akita ◽  
Kouji Maruyama ◽  
...  
Keyword(s):  
Sialic Acid ◽  
B Cells ◽  
B Cell ◽  
Marginal Zone ◽  
Cell Signalling ◽  
Negative Regulator ◽  
Mammary Adenocarcinoma ◽  
Marginal Zone B Cells ◽  
Tumour Bearing

CD22 [Siglec-2 (sialic acid-binding, immunoglobulin-like lectin-2)], a negative regulator of B-cell signalling, binds to α2,6- sialic acid-linked glycoconjugates, including a sialyl-Tn antigen that is one of the typical tumour-associated carbohydrate antigens expressed on various mucins. Many epithelial tumours secrete mucins into tissues and/or the bloodstream. Mouse mammary adenocarcinoma cells, TA3-Ha, produce a mucin named epiglycanin, but a subline of them, TA3-St, does not. Epiglycanin binds to CD22 and inhibits B-cell signalling in vitro. The in vivo effect of mucins in the tumour-bearing state was investigated using these cell lines. It should be noted that splenic MZ (marginal zone) B-cells were dramatically reduced in the mice bearing TA3-Ha cells but not in those bearing TA3-St cells, this being consistent with the finding that the thymus-independent response was reduced in these mice. When the mucins were administered to normal mice, a portion of them was detected in the splenic MZ associated with the MZ B-cells. Furthermore, administration of mucins to normal mice clearly reduced the splenic MZ B-cells, similar to tumour-bearing mice. These results indicate that mucins in the bloodstream interacted with CD22, which led to impairment of the splenic MZ B-cells in the tumour-bearing state.

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 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 Entry of B Cell Receptor into Signaling Domains Is Inhibited in Tolerant B Cells

2000 ◽  
Vol 191 (8) ◽  
pp. 1443-1448 ◽  
Author(s):  
Bennett C. Weintraub ◽  
Jesse Eunsuk Jun ◽  
Anthony C. Bishop ◽  
Kevan M. Shokat ◽  
Matthew L. Thomas ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
B Lymphocytes ◽  
Tyrosine Phosphatase ◽  
Antigen Receptor ◽  
Cell Receptor ◽  
Calcium Flux ◽  
Homogeneous Population ◽  
Kinase Activation ◽  
Antigen Receptor Signaling

Signal transduction through the B cell antigen receptor (BCR) is altered in B cells that express a receptor that recognizes self-antigen. To understand the molecular basis for the change in signaling in autoreactive B cells, a transgenic model was used to isolate a homogeneous population of tolerant B lymphocytes. These cells were compared with a similar population of naive B lymphocytes. We show that the BCR from naive B cells enters a detergent-insoluble domain of the cell within 6 s after antigen binding, before a detectable increase in BCR phosphorylation. This fraction appears to be important for signaling because it is enriched for lyn kinase but lacks CD45 tyrosine phosphatase and because the BCR that moves into this domain becomes more highly phosphorylated. Partitioning of the BCR into this fraction is unaffected by src family kinase inhibition. Tolerant B cells do not efficiently partition the BCR into the detergent-insoluble domain, providing an explanation for their reduced tyrosine kinase activation and calcium flux in response to antigen. These results identify an early, regulated step in antigen receptor signaling and self-tolerance.

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.

ZAP-70 Expression in Human B cells: Analysis of Normal Cells and Acute Lymphoblastic Leukemia (ALL) Cells with Pro/Pre B Phenotype.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4443-4443
Author(s):  
Marta Crespo ◽  
Neus Villamor ◽  
Eva Gine ◽  
Dolors Colomer ◽  
Teresa Marafioti ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Protein Tyrosine Kinase ◽  
Lymphoblastic Leukemia ◽  
Human Lymphocytes ◽  
Critical Role ◽  
Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Qrt Pcr ◽  
Human B Cells

Abstract ZAP-70 is a protein tyrosine kinase of the Syk/ZAP-70 family that plays a critical role in the signal transduction from the T-cell receptor. In human lymphocytes, ZAP-70 gene has been reported to be expressed in T and NK derived cells, and in IgVH unmutated B-chronic lymphocytic leukemia cells. More recently, ZAP-70 expression has been shown to be required for the development of pro-B cells to pre-B cells in mice. To ascertain the expression of ZAP-70 gene in human immature B-cell stages, we analyzed ZAP-70 protein and/or mRNA in normal human B cells at different stages of B cell maturation, including pro/pre-B cells and tumoral cells from 20 B-ALL. ZAP-70 expression was assessed by flow cytometry (FC), immunofluorescence (IF), and/or by quantitative real time RT-PCR (QRT-PCR). In normal bone marrow, ZAP-70 expression was found only in T and in immature B cells (CD19+/CD10+/CD20 −). Moreover, T cells -but no mature B cells- from normal tonsil expressed ZAP-70, as assessed by QRT-PCR and IF. In B-ALLs, a high ZAP-70 expression by FC was observed in 9/13 cases (mean, 82.6%, range 60–99%), whereas in 4 cases ZAP-70 was barely detectable (mean, 13%). By QRT-PCR, 10/16 B-ALLs showed levels of expression similar to ZAP-70 non-expressing cell lines and normal B-cells, whereas in the remaining cases ZAP-70 expression was 3–4 times higher than in normal mature B-cells. Taken together, a high expression of ZAP-70 was found in 11/21 (52%) B-ALLs. No relationship was observed between the level of ZAP-70 expression and the B-ALL maturation status. In conclusion, among normal B cell subsets ZAP-70 expression is restricted to B-cells with pro/pre phenotype. In addition, ZAP-70 is expressed in 52% of B-ALLs, probably as a reflection of their B-cell origin.

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.

Influence of Mir-155 On B-Cell Receptor Signaling in Chronic Lymphocytic Leukemia.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2343-2343
Author(s):  
Liguang Chen ◽  
Bing Cui ◽  
George Chen ◽  
Michelle Salcedo ◽  
Carlo M. Croce ◽  
...  
Keyword(s):  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Calcium Influx ◽  
Critical Role ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Calcium Flux ◽  
Expression Levels ◽  
Bcr Signaling

Abstract Abstract 2343 Poster Board II-320 B-cell receptor (BCR) signaling arguably plays an important role in the pathogenesis and/or progression of chronic lymphocytic leukemia. Ligation of the BCR by F(ab)2 anti-μ can induce phosphorylation of p72Syk, BLNK, phospholipase C-gamma (PLCγ) and other downstream adapter/signaling molecules, inducing intracellular calcium flux and cellular activation. Prior studies found that CLL cells that expressed unmutated Ig heavy-chain variable region genes (IGHV) and the zeta-associated protein of 70 kD (ZAP-70) generally experienced greater levels of activation following treatment with anti-μ than did CLL cells that lacked expression of ZAP-70. However, we found unusual cases that lacked expression of ZAP-70 that also responded vigorously to treatment with anti-μ, suggesting that other factors contribute to the noted differences in BCR-signaling. Analyses for expression of microRNAs by microarray revealed that CLL cells that used unmutated IGHV and that expressed ZAP-70 expressed higher levels of certain microRNAs than did cases that used mutated IGHV and that lacked expression of ZAP-70. One of such microRNA, miR-155, was found to target mRNA encoding SHIP-1, a phosphatase that plays a critical role in modulating the level of BCR signaling in normal B cells. Using quantitative assays for miR-155 we found high-level expression of this microRNA was associated with proficient BCR signaling in CLL. To examine whether miR-155 could modulate the levels of SHIP-1 and/or BCR signaling in CLL cells we transfected primary leukemia cells from each of multiple patients with control oligo-RNAs, miR-155, or a specific inhibitor of miR-155 (miR-155 inhibitor). Twenty-four hours later the cells were stimulated with anti-μ or control antibody and then examined 10 minutes later for expression of SHIP-1, induced calcium influx, or phosphorylation of kinases and adapter proteins that are involved in BCR signaling. CLL cells that had low expression levels of miR-155 and that were poorly responsive BCR had significantly higher levels of calcium influx and phosphorylated p72Syk, BLNK, and PLCγ in response to anti-μ following transfection with miR-155 than following mock transfection or transfection with control oligo-RNA. Conversely, CLL cells that had high expression levels of miR-155 and highly responsive BCR were made to have significantly higher amounts of SHIP-1 protein and to have significantly lower relative levels of phosphorylated protein and calcium influx in response to anti-μ following transfection with the miR-155 inhibitor than did mock transfected CLL cells. These results identify miR-155 as a factor that can modulate BCR signaling in CLL in part by regulating the relative expression level of SHIP-1. These results demonstrate that differential expression of microRNAs in CLL can influence physiologic features that potentially contribute to disease progression. Disclosures: No relevant conflicts of interest to declare.

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