mTOR Promotes Antiviral Humoral Immunity by Differentially Regulating CD4 Helper T Cell and B Cell Responses

ABSTRACT mTOR has important roles in regulation of both innate and adaptive immunity, but whether and how mTOR modulates humoral immune responses have yet to be fully understood. To address this issue, we examined the effects of rapamycin, a specific inhibitor of mTOR, on B cell and CD4 T cell responses during acute infection with lymphocytic choriomeningitis virus. Rapamycin treatment resulted in suppression of virus-specific B cell responses by inhibiting proliferation of germinal center (GC) B cells. In contrast, the number of memory CD4 T cells was increased in rapamycin-treated mice. However, the drug treatment caused a striking bias of CD4 T cell differentiation into Th1 cells and substantially impaired formation of follicular helper T (Tfh) cells, which are essential for humoral immunity. Further experiments in which mTOR signaling was modulated by RNA interference (RNAi) revealed that B cells were the primary target cells of rapamycin for the impaired humoral immunity and that reduced Tfh formation in rapamycin-treated mice was due to lower GC B cell responses that are essential for Tfh generation. Additionally, we found that rapamycin had minimal effects on B cell responses activated by lipopolysaccharide (LPS), which stimulates B cells in an antigen-independent manner, suggesting that rapamycin specifically inhibits B cell responses induced by B cell receptor stimulation with antigen. Together, these findings demonstrate that mTOR signals play an essential role in antigen-specific humoral immune responses by differentially regulating B cell and CD4 T cell responses during acute viral infection and that rapamycin treatment alters the interplay of immune cell subsets involved in antiviral humoral immunity. IMPORTANCE mTOR is a serine/threonine kinase involved in a variety of cellular activities. Although its specific inhibitor, rapamycin, is currently used as an immunosuppressive drug in transplant patients, it has been reported that rapamycin can also stimulate pathogen-specific cellular immunity in certain circumstances. However, whether and how mTOR regulates humoral immunity are not well understood. Here we found that rapamycin treatment predominantly inhibited GC B cell responses during viral infection and that this led to biased helper CD4 T cell differentiation as well as impaired antibody responses. These findings suggest that inhibition of B cell responses by rapamycin may play an important role in regulation of allograft-specific antibody responses to prevent organ rejection in transplant recipients. Our results also show that consideration of antibody responses is required in cases where rapamycin is used to stimulate vaccine-induced immunity.

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An Early CD4+ T Cell–dependent Immunoglobulin A Response to Influenza Infection in the Absence of Key Cognate T–B Interactions

Journal of Experimental Medicine ◽

10.1084/jem.20021745 ◽

2003 ◽

Vol 198 (7) ◽

pp. 1011-1021 ◽

Cited By ~ 85

Author(s):

Mark Y. Sangster ◽

Janice M. Riberdy ◽

Maricela Gonzalez ◽

David J. Topham ◽

Nicole Baumgarth ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

B Cells ◽

B Cell ◽

Cd4 T Cells ◽

Cd4 T Cell ◽

Mhc Ii ◽

Cell Responses ◽

Iga Response ◽

B Cell Responses

Contact-mediated interactions between CD4+ T cells and B cells are considered crucial for T cell–dependent B cell responses. To investigate the ability of activated CD4+ T cells to drive in vivo B cell responses in the absence of key cognate T–B interactions, we constructed radiation bone marrow chimeras in which CD4+ T cells would be activated by wild-type (WT) dendritic cells, but would interact with B cells that lacked expression of either major histocompatibility complex class II (MHC II) or CD40. B cell responses were assessed after influenza virus infection of the respiratory tract, which elicits a vigorous, CD4+ T cell–dependent antibody response in WT mice. The influenza-specific antibody response was strongly reduced in MHC II knockout and CD40 knockout mice. MHC II–deficient and CD40-deficient B cells in the chimera environment also produced little virus-specific immunoglobulin (Ig)M and IgG, but generated a strong virus-specific IgA response with virus-neutralizing activity. The IgA response was entirely influenza specific, in contrast to the IgG2a response, which had a substantial nonvirus-specific component. Our study demonstrates a CD4+ T cell–dependent, antiviral IgA response that is generated in the absence of B cell signaling via MHC II or CD40, and is restricted exclusively to virus-specific B cells.

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CD4 + T Cell‐Released Extracellular Vesicles Potentiate the Efficacy of the HBsAg Vaccine by Enhancing B Cell Responses

Advanced Science ◽

10.1002/advs.201802219 ◽

2019 ◽

Vol 6 (23) ◽

pp. 1802219 ◽

Cited By ~ 6

Author(s):

Jian Lu ◽

Jing Wu ◽

Feiting Xie ◽

Jie Tian ◽

Xinyi Tang ◽

...

Keyword(s):

T Cell ◽

B Cell ◽

Extracellular Vesicles ◽

Cd4 T Cell ◽

Cell Responses ◽

B Cell Responses

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Ectopic Lymphoid Follicles in Multiple Sclerosis: Centers for Disease Control?

Frontiers in Neurology ◽

10.3389/fneur.2020.607766 ◽

2020 ◽

Vol 11 ◽

Author(s):

Austin Negron ◽

Olaf Stüve ◽

Thomas G. Forsthuber

Keyword(s):

Multiple Sclerosis ◽

T Cells ◽

T Cell ◽

B Cells ◽

B Cell ◽

T Cell Responses ◽

Memory B Cells ◽

Lymphoid Follicles ◽

Cell Responses ◽

B Cell Responses

While the contribution of autoreactive CD4+ T cells to the pathogenesis of Multiple Sclerosis (MS) is widely accepted, the advent of B cell-depleting monoclonal antibody (mAb) therapies has shed new light on the complex cellular mechanisms underlying MS pathogenesis. Evidence supports the involvement of B cells in both antibody-dependent and -independent capacities. T cell-dependent B cell responses originate and take shape in germinal centers (GCs), specialized microenvironments that regulate B cell activation and subsequent differentiation into antibody-secreting cells (ASCs) or memory B cells, a process for which CD4+ T cells, namely follicular T helper (TFH) cells, are indispensable. ASCs carry out their effector function primarily via secreted Ig but also through the secretion of both pro- and anti-inflammatory cytokines. Memory B cells, in addition to being capable of rapidly differentiating into ASCs, can function as potent antigen-presenting cells (APCs) to cognate memory CD4+ T cells. Aberrant B cell responses are prevented, at least in part, by follicular regulatory T (TFR) cells, which are key suppressors of GC-derived autoreactive B cell responses through the expression of inhibitory receptors and cytokines, such as CTLA4 and IL-10, respectively. Therefore, GCs represent a critical site of peripheral B cell tolerance, and their dysregulation has been implicated in the pathogenesis of several autoimmune diseases. In MS patients, the presence of GC-like leptomeningeal ectopic lymphoid follicles (eLFs) has prompted their investigation as potential sources of pathogenic B and T cell responses. This hypothesis is supported by elevated levels of CXCL13 and circulating TFH cells in the cerebrospinal fluid (CSF) of MS patients, both of which are required to initiate and maintain GC reactions. Additionally, eLFs in post-mortem MS patient samples are notably devoid of TFR cells. The ability of GCs to generate and perpetuate, but also regulate autoreactive B and T cell responses driving MS pathology makes them an attractive target for therapeutic intervention. In this review, we will summarize the evidence from both humans and animal models supporting B cells as drivers of MS, the role of GC-like eLFs in the pathogenesis of MS, and mechanisms controlling GC-derived autoreactive B cell responses in MS.

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

Journal of Experimental Medicine ◽

10.1084/jem.20120774 ◽

2012 ◽

Vol 209 (10) ◽

pp. 1825-1840 ◽

Cited By ~ 67

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.

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B Cell Intrinsic STING Signaling Is Not Required for Autoreactive Germinal Center Participation

Frontiers in Immunology ◽

10.3389/fimmu.2021.782558 ◽

2021 ◽

Vol 12 ◽

Author(s):

Kenneth Green ◽

Thomas R. Wittenborn ◽

Cecilia Fahlquist-Hagert ◽

Ewa Terczynska-Dyla ◽

Nina van Campen ◽

...

Keyword(s):

B Cells ◽

B Cell ◽

Type I Interferon ◽

Affinity Maturation ◽

Antibody Responses ◽

Type I ◽

Cell Responses ◽

B Cell Responses ◽

Sting Pathway ◽

Humoral Responses

Germinal centers (GCs) are induced microanatomical structures wherein B cells undergo affinity maturation to improve the quality of the antibody response. Although GCs are crucial to appropriate humoral responses to infectious challenges and vaccines, many questions remain about the molecular signals driving B cell participation in GC responses. The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway is an important mediator of type I interferon and proinflammatory cytokine responses during infection and cellular stress. Recent studies have reported important roles for STING in B cell responses, including an impact on GC B cells and downstream antibody responses, which could have great consequences for vaccine design and understanding STING-associated interferonopathies. GCs are also involved in untoward reactions to autoantigens in a plethora of autoimmune disorders, and it is generally thought that these responses coopt the mechanisms used in foreign antigen-directed GCs. Here, we set out to investigate the importance of the cGAS-STING pathway in autoreactive B cell responses. In a direct competition scenario in a murine mixed bone marrow chimera model of autoreactive GCs, we find that B cell intrinsic deficiency of cGAS, STING, or the type I interferon receptor IFNAR, does not impair GC participation, whereas Toll-like receptor (TLR)-7 deficiency mediates a near-complete block. Our findings suggest that physiological B cell responses are strictly sustained by signals linked to BCR-mediated endocytosis. This wiring of B cell signals may enable appropriate antibody responses, while at the same time restricting aberrant antibody responses during infections and in autoimmune or autoinflammatory settings.

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Role of E4 in Eliciting CD4 T-Cell and B-Cell Responses to Adenovirus Vectors Delivered to Murine and Nonhuman Primate Lungs

Journal of Virology ◽

10.1128/jvi.72.7.6138-6145.1998 ◽

1998 ◽

Vol 72 (7) ◽

pp. 6138-6145 ◽

Cited By ~ 55

Author(s):

Narendra Chirmule ◽

Joseph V. Hughes ◽

Guang-Ping Gao ◽

Steven E. Raper ◽

James M. Wilson

Keyword(s):

T Cells ◽

T Cell ◽

B Cell ◽

Nonhuman Primate ◽

Neutralizing Antibodies ◽

T Cell Subsets ◽

Cd4 T Cell ◽

Cell Responses ◽

Adenovirus Vectors ◽

B Cell Responses

ABSTRACT Adenovirus vectors delivered to lung are being considered in the treatment of cystic fibrosis (CF). Vectors from which E1 has been deleted elicit T- and B-cell responses which confound their use in the treatment of chronic diseases such as CF. In this study, we directly compare the biology of an adenovirus vector from which E1 has been deleted to that of one from which E1 and E4 have been deleted, following intratracheal instillation into mouse and nonhuman primate lung. Evaluation of the E1 deletion vector in C57BL/6 mice demonstrated dose-dependent activation of both CD4 T cells (i.e., TH1 and TH2 subsets) and neutralizing antibodies to viral capsid proteins. Deletion of E4 and E1 had little impact on the CD4 T-cell proliferative response and cytolytic activity of CD8 T cells against target cells expressing viral antigens. Analysis of T-cell subsets from mice exposed to the vector from which E1 and E4 had been deleted demonstrated preservation of TH1 responses with markedly diminished TH2 responses compared to the vector with the deletion of E1. This effect was associated with reduced TH2-dependent immunoglobulin isotypes and markedly diminished neutralizing antibodies. Similar results were obtained in nonhuman primates. These studies indicate that the vector genotype can modify B-cell responses by differential activation of TH1 subsets. Diminished humoral immunity, as was observed with the E1 and E4 deletion vectors in lung, is indeed desired in applications of gene therapy where readministration of the vector is necessary.

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Allogeneic B Cell Response to H-Y Minor Histocompatibility Antigens after Donor Lymphocyte Infusion Correlates with Disease Response.

Blood ◽

10.1182/blood.v104.11.296.296 ◽

2004 ◽

Vol 104 (11) ◽

pp. 296-296

Author(s):

David B. Miklos ◽

Katherine H. Miller ◽

Haesook T. Kim ◽

Stephanie J. Lee ◽

Edwin P. Alyea ◽

...

Keyword(s):

T Cell ◽

Complete Remission ◽

B Cell ◽

Cell Response ◽

High Titer ◽

Donor Lymphocyte Infusion ◽

Antibody Responses ◽

Cell Responses ◽

Male Patients ◽

B Cell Responses

Abstract Donor lymphocyte infusion (DLI) can induce remission in many patients who relapse after allogeneic hematopoietic stem cell transplantation (HSCT). We have previously demonstrated that male HSCT patients with female donors frequently develop high-titer antibody responses to H-Y antigens that correlate with disease remission. DLI administered 6 months after T cell depleted HSCT results in a five-fold increase in peripheral B cell numbers. We sought to determine whether allogeneic B cell responses develop after DLI. We expressed 5 recombinant H-Y proteins (DBY, UTY, ZFY, RPS4Y and EIF1AY) and developed sensitive ELISA to quantify the development of specific anti-HY antibodies. First, we studied prophylactic DLI. Twenty-six patients who received T cell depleted HSCT followed 5–7 months later by prophylactic CD8 depleted DLI were tested for H-Y antibodies pre-DLI and 6–12 months after DLI. No H-Y antibodies were detected in any of the pre-DLI serum samples. However, all 6 male HSCT patients with female donors (F→M HSCT) developed high-titer antibodies against at least one H-Y antigen after DLI. In contrast, only 1/20 of the other donor/recipient gender combinations (4 M→M, 8 F→F, 8 M→F) resulted in H-Y antibody (p<0.005). Thus, mHA disparity is required for the development of allogeneic B cell responses after DLI. This robust development of H-Y antibody in 6/6 F→M patients who received TCD transplantation and prophylactic DLI was significantly greater than 3/9 who developed H-Y antibodies after receiving the same TCD HSCT without DLI (p=0.03). This suggests that DLI augments allogeneic B cell responses after T cell depleted HSCT. To examine the effects of therapeutic DLI, we studied 24 F→M HSCT patients who relapsed 60 days to 15 years (median 704 days) after transplant and subsequently received either unmanipulated DLI (1−3x107 CD3+ cells/kg; n=12) or CD8 depleted DLI (3x107 CD4+ cells/kg; n=12). Only 2/24 had any H-Y antibody at the time of relapse. After DLI, 17/24 (71%) developed antibody to at least one H-Y antigen, and this correlated with complete remission after DLI (p<0.001). Disease progression continued in all 7 patients who did not develop H-Y antibodies, but 15 of 17 patients who developed H-Y antibodies also attained complete remission. H-Y antibodies developed rapidly and were detected as early as 26 days after DLI. Fifteen of 17 patients (88%) became H-Y antibody positive before 150 days after DLI. In our previous study assessing HSCT alone, only 3 of 38 (8%) developed H-Y antibodies before 150 days. Complete remission was attained with similar frequencies after both CD8 depleted DLI (7/12) and unmanipulated DLI (8/12). However, significant differences were noted in H-Y antibody responses by DLI type. In contrast to unmanipulated DLI, patients receiving CD8 depleted DLI developed high-titer antibodies (p=0.045) against multiple H-Y antigens (p=0.012). In summary, H-Y antibodies frequently develop in male patients after infusion of female donor lymphocytes and this allogeneic B cell response correlates with clinical response to DLI. H-Y Antibody Results in Male Patients with Female Donors Any H-Y Antibody 2 or more H-Y Antibodies TCD HSCT + prophylactic CD8 depleted DLI 6/6 (100%) 4/6 (67%) TCD HSCT alone 3/9 (33%) 1/9 (11%) CD8 depleted DLI for relapse 9/12 (75%) 9/12 (75%) Unmanipulated DLI for relapse 8/12 (67%) 2/12 (17%)

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Critical Role of SAP in Progression and Reactivation but Not Maintenance of T Cell-Dependent Humoral Immunity

Molecular and Cellular Biology ◽

10.1128/mcb.01591-12 ◽

2013 ◽

Vol 33 (6) ◽

pp. 1223-1232 ◽

Cited By ~ 6

Author(s):

Ming-Chao Zhong ◽

André Veillette

Keyword(s):

T Cell ◽

B Cell ◽

Humoral Immunity ◽

Critical Role ◽

Lymphoproliferative Disease ◽

Germinal Center Reaction ◽

Cell Responses ◽

Cell Immunity ◽

B Cell Responses ◽

Signaling Lymphocytic Activation Molecule

Signaling lymphocytic activation molecule (SLAM)-associated protein (SAP) is a small adaptor molecule mutated in X-linked lymphoproliferative disease, a human immunodeficiency. SAP plays a critical role in the initiation of T cell-dependent B cell responses leading to germinal center reaction, the production of high-affinity antibodies, and B cell memory. However, whether SAP has a role in these responses beyond their initiation is not known. It is important to address this matter not only for mechanistic reasons but also because blockade of the SAP pathway is being contemplated as a means to treat autoimmune diseases in humans. Using an inducibly SAP deficient mouse, we found that SAP was required not only for the initiation but also for the progression of primary T cell-driven B cell responses to haptens. It was also necessary for the reactivation of T cell-dependent B cell immunity during secondary immune responses. These activities consistently correlated with the requirement of SAP for full expression of the lineage commitment factor Bcl-6 in follicular T helper (TFH) cells. However, once memory B cells and long-lived antibody-secreting cells were established, SAP became dispensable for maintaining T cell-dependent B cell responses. Thus, SAP is pivotal for nearly all phases, but not for maintenance, of T cell-driven B cell humoral immunity. These findings may have implications for the treatment of immune disorders by targeting the SAP pathway.

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