scholarly journals Requirement for three signals in "T-independent" (lipopolysaccharide-induced) as well as in T-dependent B cell responses.

1982 ◽  
Vol 155 (3) ◽  
pp. 666-680 ◽  
Author(s):  
R H Zubler ◽  
A L Glasebrook
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Activation ◽  
B Cell Activation ◽  
Cell Responses ◽  
Surface Immunoglobulin ◽  
Culture Cells ◽  
B Cell Responses ◽  
Helper Factor ◽  
To Receive

The requirements for different activation signals in the generation of plaque-forming cell (PFC) responses by positively selected B (surface immunoglobulin-positive) cells were analyzed in low-density cultures to minimize the possible effects of contaminating T cells. Using this system, it is demonstrated that not only in T helper cell (TH)-dependent but also in lipopolysaccharide (LPS)-dependent (i.e., so-called T-independent) PFC responses, the resting B cells have to receive at least three different signals: (a) a major histocompatibility complex (MHC)-specific TH signal that can be bypassed by LPS, (b) an antigen signal, and (c) a second TH signal medicated by MHC- and antigen-unspecific helper factor(s) for B cell responses (BHF) that cannot by bypassed by LPS. Specifically, contact of surface immunoglobulin-positive cells with cloned allo-I-A-specific TH or LPS induced a polyclonal PFC response without significant proliferation, whereas contact with BHF alone (obtained as supernatants from different cloned TH, EL-4 thymoma cells, or secondary mixed leukocyte culture cells) had no effect. Only when LPS, antigen, and BHF, or, alternatively, allo-TH (producing themselves BHF) and antigen were present did clonally expanded PFC responses occur. Thus, the data indicate that both an LPS (or specific TH) signal and an antigen signal are required to render the B cells responsive to BHF. BHF seems to act essentially as a nonspecific growth factor, whereas differentiation into antibody-secreting cells appears to be a preprogrammed consequence of B cell activation by an LPS or specific TH signal.

scholarly journals Extrafollicular B cell activation by marginal zone dendritic cells drives T cell–dependent antibody responses

2012 ◽  
Vol 209 (10) ◽  
pp. 1825-1840 ◽  
Author(s):  
Craig P. Chappell ◽  
Kevin E. Draves ◽  
Natalia V. Giltiay ◽  
Edward A. Clark
Keyword(s):  
Dendritic Cells ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Cell Activation ◽  
Marginal Zone ◽  
Receptor Expression ◽  
B Cell Activation ◽  
Cell Responses ◽  
B Cell Responses

Dendritic cells (DCs) are best known for their ability to activate naive T cells, and emerging evidence suggests that distinct DC subsets induce specialized T cell responses. However, little is known concerning the role of DC subsets in the initiation of B cell responses. We report that antigen (Ag) delivery to DC-inhibitory receptor 2 (DCIR2) found on marginal zone (MZ)–associated CD8α− DCs in mice leads to robust class-switched antibody (Ab) responses to a T cell–dependent (TD) Ag. DCIR2+ DCs induced rapid up-regulation of multiple B cell activation markers and changes in chemokine receptor expression, resulting in accumulation of Ag-specific B cells within extrafollicular splenic bridging channels as early as 24 h after immunization. Ag-specific B cells primed by DCIR2+ DCs were remarkably efficient at driving naive CD4 T cell proliferation, yet DCIR2-induced responses failed to form germinal centers or undergo affinity maturation of serum Ab unless toll-like receptor (TLR) 7 or TLR9 agonists were included at the time of immunization. These results demonstrate DCIR2+ DCs have a unique capacity to initiate extrafollicular B cell responses to TD Ag, and thus define a novel division of labor among splenic DC subsets for B cell activation during humoral immune responses.

scholarly journals Targeting Vaccine-Induced Extrafollicular Pathway of B Cell Differentiation Improves Rabies Postexposure Prophylaxis

2017 ◽  
Vol 91 (8) ◽  
Author(s):  
Shannon L. Haley ◽  
Evgeni P. Tzvetkov ◽  
Samantha Meuwissen ◽  
Joseph R. Plummer ◽  
James P. McGettigan
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Activation ◽  
Antibody Responses ◽  
B Cell Differentiation ◽  
B Cell Activation ◽  
Postexposure Prophylaxis ◽  
Effective Prevention ◽  
Cell Responses ◽  
B Cell Responses

ABSTRACT Vaccine-induced B cells differentiate along two pathways. The follicular pathway gives rise to germinal centers (GCs) that can take weeks to fully develop. The extrafollicular pathway gives rise to short-lived plasma cells (PCs) that can rapidly secrete protective antibodies within days of vaccination. Rabies virus (RABV) postexposure prophylaxis (PEP) requires rapid vaccine-induced humoral immunity for protection. Therefore, we hypothesized that targeting extrafollicular B cell responses for activation would improve the speed and magnitude of RABV PEP. To test this hypothesis, we constructed, recovered, and characterized a recombinant RABV-based vaccine expressing murine B cell activating factor (BAFF) (rRABV-mBAFF). BAFF is an ideal molecule to improve early pathways of B cell activation, as it links innate and adaptive immunity, promoting potent B cell responses. Indeed, rRABV-mBAFF induced a faster, higher antibody response in mice and enhanced survivorship in PEP settings compared to rRABV. Interestingly, rRABV-mBAFF and rRABV induced equivalent numbers of GC B cells, suggesting that rRABV-mBAFF augmented the extrafollicular B cell pathway. To confirm that rRABV-mBAFF modulated the extrafollicular pathway, we used a signaling lymphocytic activation molecule (SLAM)-associated protein (SAP)-deficient mouse model. In response to antigen, SAP-deficient mice form extrafollicular B cell responses but do not generate GCs. rRABV-mBAFF induced similar anti-RABV antibody responses in SAP-deficient and wild-type mice, demonstrating that BAFF modulated immunity through the extrafollicular and not the GC B cell pathway. Collectively, strategies that manipulate pathways of B cell activation may facilitate the development of a single-dose RABV vaccine that replaces current complicated and costly RABV PEP. IMPORTANCE Effective RABV PEP is currently resource- and cost-prohibitive in regions of the world where RABV is most prevalent. In order to diminish the requirements for rabies immunoglobulin (RIG) and multiple vaccinations for effective prevention of clinical rabies, a more rapidly protective vaccine is needed. This work presents a successful approach to rapidly generate antibody-secreting PCs in response to vaccination by targeting the extrafollicular B cell pathway. We demonstrate that the improved early antibody responses induced by rRABV-mBAFF confer improved protection against RABV in a PEP model. Significantly, activation of the early extrafollicular B cell pathway, such as that demonstrated here, could improve the efficacy of vaccines targeting other pathogens against which rapid protection would decrease morbidity and mortality.

scholarly journals Anti-CD40 antibody KPL-404 inhibits T cell-mediated activation of B cells from healthy donors and autoimmune patients

2021 ◽  
Vol 23 (1) ◽  
Author(s):  
John Marken ◽  
Sujatha Muralidharan ◽  
Natalia V. Giltiay
Keyword(s):  
Flow Cytometry ◽  
B Cells ◽  
B Cell ◽  
Cell Activation ◽  
Cytokine Production ◽  
B Cell Activation ◽  
Cell Responses ◽  
Healthy Donors ◽  
B Cell Responses

Abstract Background CD40-CD40L is a key co-stimulatory pathway for B cell activation. As such, its blockade can inhibit pathogenic B cell responses in autoimmune diseases, such as Sjogren’s syndrome (SjS) and systemic lupus erythematosus (SLE). In this study, we examined the in vitro effects of KPL-404, a humanized anti-CD40 monoclonal antibody (Ab), on primary human B cells derived from either healthy donors (HD) or autoimmune patients and compared them to the effects of G28-5, a partially antagonistic anti-CD40 antibody. Methods PBMCs from HD or SjS and SLE patients were cultured in high-density cell cultures in the presence of IgG4 isotype control or anti-CD40 Abs KPL-404 or G28-5. Cells were stimulated with anti-CD3/CD28 cross-linking reagent ImmunoCult (IC) to induce CD40L-CD40-mediated B cell responses. B cell proliferation and activation, measured by dilution of proliferation tracker dye and the upregulation of CD69 and CD86, respectively, were assessed by flow cytometry. Anti-CD40 Ab cell-internalization was examined by imaging flow cytometry. Cytokine release in the PBMC cultures was quantified by bead-based multiplex assay. Results KPL-404 binds to CD40 expressed on different subsets of B cells without inducing cell depletion, or B cell proliferation and activation in in vitro culture. Under the same conditions, G28-5 promoted proliferation of and increased CD69 expression on otherwise unstimulated B cells. KPL-404 efficiently blocked the CD40L-CD40-mediated activation of B cells from HD at concentrations between 1 and 10 μg/ml. Treatment with KPL-404 alone did not promote cytokine production and blocked the production of IFNβ in healthy PBMC cultures. KPL-404 efficiently blocked CD40L-CD40-mediated activation of B cells from patients with SjS and SLE, without affecting their anti-IgM responses or affecting their cytokine production. Consistent with the differences of their effects on B cell responses, KPL-404 was not internalized by cells, whereas G28-5 showed partial internalization upon CD40 binding. Conclusions Anti-CD40 mAb KPL-404 showed purely antagonistic effects on B cells and total PBMCs. KPL-404 inhibited CD40L-CD40-mediated B cell activation in PBMC cultures from both healthy controls and autoimmune patients. These data support the therapeutic potential of CD40 targeting by KPL-404 Ab for inhibiting B cell responses in SjS and SLE.

scholarly journals Arp2/3 complex-driven spatial patterning of the BCR enhances immune synapse formation, BCR signaling and B cell activation

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Madison Bolger-Munro ◽  
Kate Choi ◽  
Joshua M Scurll ◽  
Libin Abraham ◽  
Rhys S Chappell ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Activation ◽  
Synapse Formation ◽  
Critical Role ◽  
Transcriptional Responses ◽  
Immune Synapse ◽  
Cell Responses ◽  
Bcr Signaling ◽  
B Cell Responses

When B cells encounter antigens on the surface of an antigen-presenting cell (APC), B cell receptors (BCRs) are gathered into microclusters that recruit signaling enzymes. These microclusters then move centripetally and coalesce into the central supramolecular activation cluster of an immune synapse. The mechanisms controlling BCR organization during immune synapse formation, and how this impacts BCR signaling, are not fully understood. We show that this coalescence of BCR microclusters depends on the actin-related protein 2/3 (Arp2/3) complex, which nucleates branched actin networks. Moreover, in murine B cells, this dynamic spatial reorganization of BCR microclusters amplifies proximal BCR signaling reactions and enhances the ability of membrane-associated antigens to induce transcriptional responses and proliferation. Our finding that Arp2/3 complex activity is important for B cell responses to spatially restricted membrane-bound antigens, but not for soluble antigens, highlights a critical role for Arp2/3 complex-dependent actin remodeling in B cell responses to APC-bound antigens.

scholarly journals Type 1 interferon supports B cell responses to polysaccharide antigens but is not required for MPL/TDCM adjuvant effects on innate B cells

2021 ◽  
Author(s):  
Ariel Spurrier ◽  
Jamie Jennings-Gee ◽  
Karen Haas
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Activation ◽  
Lipid A ◽  
Type I ◽  
Type I Ifn ◽  
Cell Responses ◽  
Monophosphoryl Lipid A ◽  
B Cell Responses ◽  
Adjuvant Effects

We previously described monophosphoryl lipid A (MPL) and synthetic cord factor, trehalose-6,6-dicorynomycolate (TDCM) significantly increases antibody (Ab) responses to T cell independent type 2 antigens (TI-2 Ags) in a manner dependent on B cell-intrinsic TLR4 expression as well as MyD88 and TRIF adapter proteins. Given the requirement for TRIF in optimal MPL/TDCM adjuvant effects and the capacity of MPL to drive type I IFN production, we aimed to investigate the extent to which adjuvant effects on TI-2 Ab responses depend on type I IFN receptor (IFNAR) signaling. We found IFNAR-/- mice had impaired early TI-2 Ag-induced B cell activation and expansion and that B cell-intrinsic type I IFN signaling on B cells was essential for normal antibody responses to TI-2 Ags, including haptenated Ficoll and the pneumococcal vaccine, Pneumovax23. However, MPL/TDCM significantly increased TI-2 IgM and IgG responses in IFNAR-/- mice. MPL/TDCM enhanced TI-2 Ab production primarily by activating innate B cells (B-1b and splenic CD23- B cells) as opposed to CD23+ enriched follicular B cells. In summary, our study highlights an important role for type I IFN in supporting early B cell responses to TI-2 Ags through B cell-expressed IFNAR, but nonetheless demonstrates an MPL/TDCM adjuvant significantly increases TI-2 Ab responses independently of type I IFN signaling and does so by predominantly supporting increased polysaccharide-specific Ab production by innate B cell populations.

scholarly journals Effects of Friend Virus Infection and Regulatory T Cells on the Antigen Presentation Function of B Cells

mBio ◽  
2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Tyler C. Moore ◽  
Ronald J. Messer ◽  
Lorena M. Gonzaga ◽  
Jennifer M. Mather ◽  
Aaron B. Carmody ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cells ◽  
Regulatory T Cells ◽  
B Cell ◽  
Cell Activation ◽  
T Cell Responses ◽  
B Cell Activation ◽  
Friend Virus ◽  
Cell Responses

ABSTRACTFriend virus (FV) is a naturally occurring mouse retrovirus that infects dividing cells of the hematopoietic lineage, including antigen-presenting cells (APCs). The infection of APCs by viruses often induces their dysfunction, and it has been shown that FV infection reduces the ability of dendritic cells (DCs) to prime critical CD8+T cell responses. Nonetheless, mice mount vigorous CD8+T cell responses, so we investigated whether B cells might serve as alternative APCs during FV infection. Directex vivoanalysis of B cells from FV-infected mice revealed that infected but not uninfected B cells upregulated expression of the costimulatory molecules CD80, CD86, and CD40, as well as major histocompatibility complex class II (MHC-II) molecules. Furthermore,in vitrostudies showed that, compared to uninfected B cells from the same mice, the FV-infected B cells had significantly enhanced APC function, as measured by their capacity to prime CD8+T cell activation and proliferation. Thus, in contrast to DCs, infection of B cells with FV enhanced their APC capacity and ability to stimulate the CD8+T cell responses essential for virus control. FV infections also induce the activation and expansion of regulatory T cells (Tregs), so it was of interest to determine the impact of Tregs on B cell activation. The upregulation of costimulatory molecule expression and APC function of B cells was even more strongly enhanced byin vivodepletion of regulatory T cells than infection. Thus, Tregs exert potent homeostatic suppression of B cell activation that is partially overcome by FV infection.IMPORTANCEThe primary role of B cells in immunity is considered the production of pathogen-specific antibodies, but another, less-well-studied, function of B cells is to present foreign antigens to T cells to stimulate their activation and proliferation. Dendritic cells (DCs) are considered the most important antigen-presenting cells (APCs) for CD8+T cells, but DCs lose APC function when infected with Friend virus (FV), a model retrovirus of mice. Interestingly, B cells were better able to stimulate CD8+T cell responses when they were infected with FV. We also found that the activation status of B cells under homeostatic conditions was potently modulated by regulatory T cells. This study illustrates an important link between B cell and T cell responses and illustrates an additional mechanism by which regulatory T cells suppress critical T cell responses during viral infections.

scholarly journals Immunoglobulin-mediated signal transduction in B cells from CD45-deficient mice.

1996 ◽  
Vol 183 (1) ◽  
pp. 329-334 ◽  
Author(s):  
T Benatar ◽  
R Carsetti ◽  
C Furlonger ◽  
N Kamalia ◽  
T Mak ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Activation ◽  
Buoyant Density ◽  
Lymphoid Tissues ◽  
B Cell Activation ◽  
Normal Numbers ◽  
Cell Responses ◽  
Deficient Mice

CD45 expression is essential for immunoglobulin (Ig)-mediated B cell activation. Treatments with either anti-Ig or anti-CD45 suggest that CD45 may facilitate early signaling events such as calcium mobilization, and phosphoinositide hydrolyis as well as later events leading to transcription of genes such as c-myc. To examine the role of CD45 more extensively, CD45-deficient mice were generated by disruption of exon 6. Although normal numbers of B cells were found in peripheral lymphoid tissues, CD45-deficient cells failed to proliferate upon IgM crosslinking. In the present study, we demonstrate that the fraction of high buoyant density B cells is reduced while low buoyant density cells are increased. Moreover, there is a significant decline in the number of splenic B cells of the mature IgDhi, IgMlo phenotype. Although both the basal and anti-Ig-induced levels of phosphorylation of Ig-alpha and phospholipase C gamma 2 are indistinguishable from that observed in CD45+ control B cells, a major distinction was found in Ca2+ mobilization. While anti-Ig-induced mobilization of intracellular Ca2+ stores was normal, influx from extracellular sources was abrogated. This finding reveals a novel pathway of regulating B cell responses mediated by CD45.

scholarly journals Arp2/3 complex-driven spatial patterning of the BCR enhances immune synapse formation, BCR signaling and cell activation

2018 ◽  
Author(s):  
Madison Bolger-Munro ◽  
Kate Choi ◽  
Joshua Scurll ◽  
Libin Abraham ◽  
Rhys Chappell ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Activation ◽  
Synapse Formation ◽  
Critical Role ◽  
Transcriptional Responses ◽  
Immune Synapse ◽  
Cell Responses ◽  
Bcr Signaling ◽  
B Cell Responses

AbstractWhen B cells encounter antigens on the surface of an antigen-presenting cell (APC), B cell receptors (BCRs) are gathered into microclusters that recruit signaling enzymes. These microclusters then move centripetally and coalesce into the central supramolecular activation cluster of an immune synapse. The mechanisms controlling BCR organization during immune synapse formation, and how this impacts BCR signaling, are not fully understood. We show that this coalescence of BCR microclusters depends on the actin-related protein 2/3 (Arp2/3) complex, which nucleates branched actin networks. Moreover, in murine B cells this dynamic spatial reorganization of BCR microclusters amplifies proximal BCR signaling reactions and enhances the ability of membrane-associated antigens to induce transcriptional responses and proliferation. Our finding that Arp2/3 complex activity is important for B cell responses to spatially-restricted membrane-bound antigens, but not for soluble antigens, highlights a critical role for Arp2/3 complex-dependent actin remodelling in B cell responses to APC-bound antigens.

scholarly journals Dominant extrafollicular B cell responses in severe COVID-19 disease correlate with robust viral-specific antibody production but poor clinical outcomes

2020 ◽  
Author(s):  
Matthew C. Woodruff ◽  
Richard P. Ramonell ◽  
Kevin S. Cashman ◽  
Doan C. Nguyen ◽  
Ankur Singh Saini ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Activation ◽  
B Cell Activation ◽  
Specific Patient ◽  
Antibody Secreting Cell ◽  
Cell Responses ◽  
Specific Antibody Production ◽  
Early Production ◽  
B Cell Responses

Abstract/IntroductionA wide clinical spectrum has become a hallmark of the SARS-CoV-2 (COVID-19) pandemic, although its immunologic underpinnings remain to be defined. We have performed deep characterization of B cell responses through high-dimensional flow cytometry to reveal substantial heterogeneity in both effector and immature populations. More notably, critically ill patients displayed hallmarks of extrafollicular B cell activation as previously described in autoimmune settings. Extrafollicular activation correlated strongly with large antibody secreting cell expansion and early production of high levels of SARS-CoV-2-specific antibodies. Yet, these patients fared poorly with elevated inflammatory biomarkers, multi-organ failure, and death. Combined, the findings strongly indicate a major pathogenic role for immune activation in subsets of COVID-19 patients. Our study suggests that, as in autoimmunity, targeted immunomodulatory therapy may be beneficial in specific patient subpopulations that can be identified by careful immune profiling.

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