Helper Function Research Articles

Nanovaccine administration route is critical to obtain pertinent iNKt cell help for robust anti-tumor T and B cell responses

ABSTRACT Nanovaccines, co-delivering antigen and invariant natural killer T (iNKT) cell agonists, proved to be very effective in inducing anti-tumor T cell responses due to their exceptional helper function. However, it is known that iNKT cells are not equally present in all lymphoid organs and nanoparticles do not get evenly distributed to all immune compartments. In this study, we evaluated the effect of the vaccination route on iNKT cell help to T and B cell responses for the first time in an antigen and agonist co-delivery setting. Intravenous administration of PLGA nanoparticles was mainly targeting liver and spleen where iNKT1 cells are abundant and induced the highest serum IFN-y levels, T cell cytotoxicity, and Th-1 type antibody responses. In comparison, after subcutaneous or intranodal injections, nanoparticles mostly drained or remained in regional lymph nodes where iNKT17 cells were abundant. After subcutaneous and intranodal injections, antigen-specific IgG2 c production was hampered and IFN-y production, as well as cytotoxic T cell responses, depended on sporadic systemic drainage. Therapeutic anti-tumor experiments also demonstrated a clear advantage of intravenous injection over intranodal or subcutaneous vaccinations. Moreover, tumor control could be further improved by PD-1 immune checkpoint blockade after intravenous vaccination, but not by intranodal vaccination. Anti PD-1 antibody combination mainly exerts its effect by prolonging the cytotoxicity of T cells. Nanovaccines also demonstrated synergism with anti-4-1BB agonistic antibody treatment in controlling tumor growth. We conclude that nanovaccines containing iNKT cell agonists shall be preferentially administered intravenously, to optimally reach cellular partners for inducing effective anti-tumor immune responses.

RCy3: Network biology using Cytoscape from within R.

RCy3 is an R package in Bioconductor that communicates with Cytoscape via its REST API, providing access to the full feature set of Cytoscape from within the R programming environment. RCy3 has been redesigned to streamline its usage and future development as part of a broader Cytoscape Automation effort. Over 100 new functions have been added, including dozens of helper functions specifically for intuitive data overlay operations. Over 40 Cytoscape apps have implemented automation support so far, making hundreds of additional operations accessible via RCy3. Two-way conversion with networks from \textit{igraph} and \textit{graph} ensures interoperability with existing network biology workflows and dozens of other Bioconductor packages. These capabilities are demonstrated in a series of use cases involving public databases, enrichment analysis pipelines, shortest path algorithms and more. With RCy3, bioinformaticians will be able to quickly deliver reproducible network biology workflows as integrations of Cytoscape functions, complex custom analyses and other R packages.

RCy3: Network biology using Cytoscape from within R

RCy3 is an R package in Bioconductor that communicates with Cytoscape via its REST API, providing access to the full feature set of Cytoscape from within the R programming environment. RCy3 has been redesigned to streamline its usage and future development as part of a broader Cytoscape Automation effort. Over 100 new functions have been added, including dozens of helper functions specifically for intuitive data overlay operations. Over 40 Cytoscape apps have implemented automation support so far, making hundreds of additional operations accessible via RCy3. Two-way conversion with networks from \textit{igraph} and \textit{graph} ensures interoperability with existing network biology workflows and dozens of other Bioconductor packages. These capabilities are demonstrated in a series of use cases involving public databases, enrichment analysis pipelines, shortest path algorithms and more. With RCy3, bioinformaticians will be able to quickly deliver reproducible network biology workflows as integrations of Cytoscape functions, complex custom analyses and other R packages.

RCy3: Network biology using Cytoscape from within R

RCy3 is an R package in Bioconductor that communicates with Cytoscape via its REST API, providing access to the full feature set of Cytoscape from within the R programming environment. RCy3 has been redesigned to streamline its usage and future development as part of a broader Cytoscape Automation effort. Over 100 new functions have been added, including dozens of helper functions specifically for intuitive data overlay operations. Over 40 Cytoscape apps have implemented automation support so far, making hundreds of additional operations accessible via RCy3. Two-way conversion with networks from \ extit{igraph} and \ extit{graph} ensures interoperability with existing network biology workflows and dozens of other Bioconductor packages. These capabilities are demonstrated in a series of use cases involving public databases, enrichment analysis pipelines, shortest path algorithms and more. With RCy3, bioinformaticians will be able to quickly deliver reproducible network biology workflows as integrations of Cytoscape functions, complex custom analyses and other R packages.

Guided Polarization of iPSC-Derived CD4SP Helper T Cells By CRISPR/Cas9-Based Genome-Editing

Guided Polarization of iPSC-Derived CD4SP Helper T Cells By CRISPR/Cas9-Based Genome-Editing

306. CD8+ T-Cell Responses to Chronic Hepatitis C in Pregnancy

BackgroundChronic hepatitis C virus (HCV) infection is marked by stable, high -level viremia and a failed T-cell response. HCV-specific CD4+ helper T cells are rare, and CD8+ cytotoxic T cells are functionally exhausted or ineffective due to viral escape mutations. Postpartum, a subset of infected women experience a substantial drop in viremia. Preliminary data indicate that this unusual viral decline may be linked to a resurgence of HCV-specific CD4+ T cells producing Th1 cytokines. How improved CD4+ helper T-cell function might affect viral replication in this scenario is not established. Here we tested the hypothesis that improved CD4+ T cell help mediates control of chronic HCV replication through enhanced CD8+ T-cell function.MethodsWe examined plasma HCV RNA viral load (VL) and HCV-specific T-cell responses in 33 women with chronic HCV during the third trimester (T3) and at 3 months postpartum (3P). HCV-specific CD4+ and CD8+ T-cell IL2 and IFNγ responses were measured by intracellular cytokine staining following stimulation of peripheral blood mononuclear cells with peptide pools corresponding to the HCV proteins NS3, NS4a, and NS4B.ResultsMedian VL dropped from 5.87 log10 at T3 to 5.25 log10 at 3P (P < 0.0001, Wilcoxson signed rank), with a wide range from +0.4 log10 to -4.2 log10. The degree of decline correlated significantly with improved frequencies of HCV-specific CD4+ T cells producing IFNγ (P = 0.015 Spearman) but did not correlate with CD8+ T-cell changes. Nevertheless, improved T helper function correlated with increased HCV-specific CD8+ T-cell function (ΔCD4+IL2+ vs. ΔCD8+IFNγ+, P = 0.015 Spearman, graph 1; ΔCD4+IFNγ+ vs. CD8+IFNγ+ at 3P, P = 0.004 Spearman, graph 2).ConclusionDespite no significant association between virus-specific CD8+ T-cell Tc1 cytokine production and postpartum viral control, our data suggest that recovery of CD4+ T-cell help may augment CD8+ T-cell function. Further study incorporating viral genomic sequences to focus on intact class I epitopes is needed to clarify the relationship of improved CD8+ function and viral control in this unique model of immune restoration. Disclosures All authors: No reported disclosures.

RCy3: Network biology using Cytoscape from within R

RCy3 is an R package in Bioconductor that communicates with Cytoscape via its REST API, providing access to the full feature set of Cytoscape from within the R programming environment. RCy3 has been redesigned to streamline its usage and future development as part of a broader Cytoscape Automation effort. Over 100 new functions have been added, including dozens of helper functions specifically for intuitive data overlay operations. Over 40 Cytoscape apps have implemented automation support so far, making hundreds of additional operations accessible via RCy3. Two-way conversion with networks from \textit{igraph} and \textit{graph} ensures interoperability with existing network biology workflows and dozens of other Bioconductor packages. These capabilities are demonstrated in a series of use cases involving public databases, enrichment analysis pipelines, shortest path algorithms and more. With RCy3, bioinformaticians will be able to quickly deliver reproducible network biology workflows as integrations of Cytoscape functions, complex custom analyses and other R packages.

Cytotoxic and Helper T Cell Memory is Programmed by Mhc-Independent Generic Programs

The prevailing 'division of labor' concept in cellular immunity is that CD8+ T cells primarily utilize cytotoxic functions to kill target cells, while CD4+ T cells exert helper/inducer functions. Multiple subsets of CD4+ memory T cells have been characterized by distinct chemokine receptor expression. Here, we demonstrate that analogous CD8+ memory T-cell subsets are present characterized by identical chemokine receptor expression signatures. Among them, Tc2, Tc17 and Tc22 cells, in contrast to Tc1 and Tc17+1 cells, expressed IL-6R but not SLAMF7, completely lacked cytotoxicity and instead displayed helper functions including CD40L expression. CD8+ helper T cells exhibited a unique TCR repertoire, expressed genes related to skin resident memory T cells (TRM) and were altered in the inflammatory skin disease psoriasis. Our findings provide evidence that the conventional view of CD4+ and CD8+ T cell capabilities and functions in human health and disease needs to be revised.

The nlrx r package: A next‐generation framework for reproducible NetLogo model analyses

Abstract Agent‐based models find wide application in all fields of science where large‐scale patterns emerge from properties of individuals. Due to increasing capacities of computing resources it was possible to improve the level of detail and structural realism of next‐generation models in recent years. However, this is at the expense of increased model complexity, which requires more efficient tools for model exploration, analysis and documentation that enable reproducibility, repeatability and parallelization. NetLogo is a widely used environment for agent‐based model development, but it does not provide sufficient built‐in tools for extensive model exploration, such as sensitivity analyses. One tool for controlling NetLogo externally is the r‐package RNetLogo. However, this package is not suited for efficient, reproducible research as it has stability and resource allocation issues, is not straightforward to be setup and used on high performance computing clusters and does not provide utilities, such as storing and exchanging metadata, in an easy way. We present the r‐package nlrx, which overcomes stability and resource allocation issues by running NetLogo simulations via dynamically created XML experiment files. Class objects make setting up experiments more convenient and helper functions provide many parameter exploration approaches, such as Latin Hypercube designs, Sobol sensitivity analyses or optimization approaches. Output is automatically collected in user‐friendly formats and can be post‐processed with provided utility functions. nlrx enables reproducibility by storing all relevant information and simulation output of experiments in one r object which can conveniently be archived and shared. We provide a detailed description of the nlrx package functions and the overall workflow. We also present a use case scenario using a NetLogo model, for which we performed a sensitivity analysis and a genetic algorithm optimization. The nlrx package is the first framework for documentation and application of reproducible NetLogo simulation model analysis.

Transcriptional Analysis of Lennert Lymphoma Reveals a Unique Profile and Identifies Novel Therapeutic Targets.

Lennert lymphoma (LL) is a lymphoepithelioid morphological variant of peripheral T-cell lymphoma—not otherwise specified (PTCL/NOS), clinically characterized by better prognosis if compared with other PTCL/NOS. Although well characterized as far as morphology and phenotype are concerned, very little is known regarding its molecular features. In this study, we investigated the transcriptional profile of this tumor aiming 1) to identify its cellular counterparts; 2) to better define its relation with other PTCLs—and, therefore, its possible position in lymphoma classification; and 3) to define pathogenetic mechanisms, possibly unveiling novel therapeutic targets. To address these issues, we performed gene and microRNA expression profiling on LL and other PTCL/NOS cases; we identified different genes and microRNAs that discriminated LL from other PTCL/NOS. Particularly, LL revealed a molecular signature significantly enriched in helper function and clearly distinguishable from other PTCL/NOS. Furthermore, PI3K/Akt/mTOR pathway emerged as novel potential therapeutic target. In conclusion, based on the already known particular morphological and clinical features, the new molecular findings support the hypothesis that LL might be classified as a separate entity. Preclinical and clinical studies testing the efficacy of PI3K/MTOR inhibitors in this setting are warranted.

Long Non-Coding RNA Function in CD4+ T Cells: What We Know and What Next?

The non-coding genome has previously been regarded as “junk” DNA; however, emerging evidence suggests that the non-coding genome accounts for some of the greater biological complexity observed in mammals. Research into long non-coding RNAs (lncRNAs) has gathered speed in recent years, and a growing body of evidence has implicated lncRNAs in a vast range of cellular functions including gene regulation, chromosome organisation and splicing. T helper cells offer an ideal platform for the study of lncRNAs given they function as part of a complex cellular network and undergo remarkable and finely regulated gene expression changes upon antigenic stimulation. Using various knock down and RNA interaction studies several lncRNAs have been shown to be crucial for T helper cell differentiation, activation and function. Given that RNA targeting therapeutics are rapidly gaining attention, further understanding the mechanistic role of lncRNAs in a T helper context is an exciting area of research, as it may unearth a wide range of new candidate targets for treatment of CD4+ mediated pathologies.

Circulating CXCR5\u2212PD-1hi peripheral T helper cells are associated with progression to type 1 diabetes

Aims/hypothesisType 1 diabetes is preceded by a period of asymptomatic autoimmunity characterised by positivity for islet autoantibodies. Therefore, T helper cell responses that induce B cell activation are likely to play a critical role in the disease process. Here, we aimed to evaluate the role of a recently described subset, C-X-C motif chemokine receptor type 5-negative, programmed cell death protein 1-positive (CXCR5−PD-1hi) peripheral T helper (Tph) cells, in human type 1 diabetes.MethodsThe phenotype of blood CXCR5−PD-1hi CD4+ T cells was analysed by multicolour flow cytometry. The frequencies of circulating CXCR5−PD-1hi T cells were analysed in a cohort of 44 children with newly diagnosed type 1 diabetes, 40 autoantibody-positive (AAb+) at-risk children and 84 autoantibody-negative healthy control children, and the findings were replicated in a separate cohort of 15 children with newly diagnosed type 1 diabetes and 15 healthy control children.ResultsCirculating CXCR5−PD-1hi Tph cells share several features associated with B cell helper function with circulating CXCR5+PD-1hi follicular T helper (Tfh) cells. Moreover, the frequency of circulating Tph cells was increased in children with newly diagnosed type 1 diabetes, especially in those who are positive for multiple autoantibodies. Importantly, circulating Tph cells were also increased in autoantibody-positive at-risk children who later progressed to type 1 diabetes.Conclusions/interpretationOur results demonstrate that circulating CXCR5−PD-1hi Tph cells are associated with progression to clinical type 1 diabetes. Consequently, Tph cells could have potential both as a biomarker of disease progression and as a target for immunotherapy in type 1 diabetes.

Abstract 2313: Enhanced activity of second-generation MAGE-A4 SPEAR T-cells through co-expression of a CD8α homodimer

Abstract Affinity enhanced T-cell receptors (TCRs) have shown promise in the clinic. Second-generation strategies that enhance T-cell function alongside the TCR may improve the depth and durability of anti-tumor responses. In this second-generation TCR study, we added a CD8α homodimer to our MAGE-A4c1032TCR, a first-generation TCR currently being tested in a clinical trial (NCT03132922). Transduction of HLA class I-restricted, specific peptide enhanced affinity receptor (SPEAR) TCRs into peripheral blood lymphocytes creates both cytotoxic (CD8+) and helper (CD4+) T-cells of the same specificity; however, the lack of CD8 co-receptors on CD4+ T-cells may affect binding avidity of the engineered TCR. The addition of CD8α co-receptor into CD4+ T-cells alongside the engineered TCR (CD8α_MAGE-A4c1032) is anticipated to increase TCR binding avidity and enhance the polyfunctional response of CD4+ T-cells against tumor antigens, thereby widening the immune response to the tumor through dendritic cell (DC) activation and enhanced cytotoxicity. The effect of co-expressing the CD8α co-receptor on the MAGE-A4c1032TCR was assessed by in vitro assays addressing proof of concept for increased potency, focusing on CD4+ function, in parallel with assessment of potential safety issues. In assays involving antigen-positive tumor cell lines co-cultured with T-cells, we demonstrated improved T-cell engagement, as measured by increased CD40L on the T-cell surface in response to antigen. There were modest improvements in T-cell proliferation and cytokine production in response to tumor cells, particularly when isolated CD4+ cells were analyzed. However, when immature DCs were added to the co-culture, a more marked improvement with the second-generation T-cells was seen. DCs and T-cells in conditions containing CD8α_MAGE-A4c1032T-cells produced higher levels of cytokines and chemokines (e.g. IL-12, MIG for DCs, IFNγ, IL-2 for T-cells) than in conditions that contained MAGE-A4c1032T-cells without the CD8α co-receptor. Flow cytometry analyses illustrated T-cell-driven maturation of the DCs during the course of the co-culture. We also saw that second-generation CD4+ T-cells expressing the CD8α homodimer were able to kill antigen-expressing 3D tumor line microspheres, an additional benefit to the improvement of CD4+ helper functions. No changes in TCR specificity, sensitivity, or aberrant cytokine release arose from co-expressing the CD8α co-receptor in T-cells transduced with the MAGE-A4c1032TCR, suggesting no change to the existing safety profile. These data illustrate improved engagement and function in the CD4+ T-cells transduced with CD8α_MAGE-A4c1032, without additional off-target reactivity. The second generation CD8α_MAGE-A4 SPEAR T-cells are expected to improve long term T-cell functions as well as immediate anti-tumor activity in vivo. Citation Format: Victoria E. Anderson, Anika M. Weber, Guy E. Wiedermann, Anette Pachnio, Sumaya Dauleh, Tina Ahmed, Roslin Y. Docta, Adriano Quattrini, George Pope, Laura Quinn, Thomas M. Ashton, Helen M. Tunbridge, Joseph P. Sanderson, Andrew B. Gerry. Enhanced activity of second-generation MAGE-A4 SPEAR T-cells through co-expression of a CD8α homodimer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2313.

A role for antibodies in natural HIV control.

Rare patients naturally control HIV replication without antiretroviral therapy. Understanding the mechanisms implicated in natural HIV control will inform the development of immunotherapies against HIV. Elite controllers are known for developing efficient antiviral T-cell responses, but recent findings suggest that antibody responses also play a significant role in HIV control. We review the key studies that uncovered a potent memory B-cell response and highly functional anti-HIV antibodies in elite controllers, and explore the mechanisms that may account for the distinct properties of their humoral response. Elite controllers maintain a large HIV-specific memory B-cell pool that is sustained by efficient T follicular helper function. Neutralizing antibody rarely show high titers in controllers, but seem capable, at least in certain cases, of neutralizing contemporaneous viral strains. In addition, elite controllers display a unique HIV-specific antibody profile in terms of isotype, antigen specificity, and glycosylation pattern, resulting in polyfunctional antibody effector functions that may promote infected cell lysis and prime effectors of the antiviral immune response. Lessons from elite controller studies argue for the importance of integrating the many parameters defining a polyfunctional antibody response when evaluating candidate vaccines and immunotherapeutic approaches directed at HIV.

Recapitulation of HDV infection in a fully permissive hepatoma cell line allows efficient drug evaluation

Hepatitis delta virus (HDV) depends on the helper function of hepatitis B virus (HBV), which provides the envelope proteins for progeny virus secretion. Current infection-competent cell culture models do not support assembly and secretion of HDV. By stably transducing HepG2 cells with genes encoding the NTCP-receptor and the HBV envelope proteins we produce a cell line (HepNB2.7) that allows continuous secretion of infectious progeny HDV following primary infection. Evaluation of antiviral drugs shows that the entry inhibitor Myrcludex B (IC50: 1.4 nM) and interferon-α (IC50: 28 IU/ml, but max. 60–80% inhibition) interfere with primary infection. Lonafarnib inhibits virus secretion (IC50: 36 nM) but leads to a substantial intracellular accumulation of large hepatitis delta antigen and replicative intermediates, accompanied by the induction of innate immune responses. This work provides a cell line that supports the complete HDV replication cycle and presents a convenient tool for antiviral drug evaluation.

The effects of altered TGFβ signaling on human T follicular helper cell development and function

Abstract T follicular helper (Tfh) cells are a subset of CD4+ T cells that play a crucial role in the development of memory B cells and plasma cells. T follicular regulatory (Tfr) cells oppose Tfh cells and suppress humoral immune responses. Patients with Loeys-Dietz Syndrome (LDS) type 1 and 2 have an autosomal dominant mutation in the genes encoding TGFβ Receptor 1 or 2, respectively, and have a strong predisposition to develop allergic diseases. We hypothesized that altered development and function of Tfh cells could contribute to increased IgE-mediated allergic phenotypes in LDS. Comparing a cohort of pediatric LDS patients with age-matched healthy volunteers, we found that LDS patients have significantly higher levels of serum IgE and IgG and lower levels of IgM. Congruently, LDS patients have an increased frequency of memory T cells, Th2 cells, and Tfh cells and a significantly lower frequency of Tfr cells. The increase in Tfh cells in LDS was restricted to the CCR4+ CCR6− subset, which has been associated with Th2 immune responses. In vitro, Tfh cells from LDS patients co-cultured with autologous naïve B cells demonstrated a greater ability to induce plasma cell differentiation compared to age-matched healthy volunteers. Additionally, naïve CD4+ T cells from LDS patients cultured in the presence of recombinant TGFβ1 and IL-12 or IL-4 were more likely to differentiate into Tfh cells compared to healthy age-matched controls, suggesting a cell-intrinsic propensity for naïve CD4+ T cells in LDS patients to acquire a Tfh fate. Collectively, our data suggest that LDS mutations alter the development and function of Tfh cells in a manner that promotes IgE-mediated disease.

Intrinsic factor Recognition Promotes Th17/Th1 Autoimmune Gastric Inflammation in Patients with Pernicious Anemia

Abstract The intrinsic factor (IF) is the major humoral autoantigen in pernicious anemia (PA)/autoimmune gastritis. Although many studies have examined the autoantibody response to intrinsic factor and H+,K+-ATPase, no information is available on possible pathogenic mechanisms mediated by IF-specific gastric T cells. The aim of this study was to investigate IF-specific T cells in the gastric mucosa of PA patients and define their functional properties. In vivo-activated T cells from the infiltrates of the gastric mucosa of PA patients were isolated and cloned. We investigated the ability of the gastric T-cell clones to proliferate and produce cytokines in response to IF, as well as their helper function for antibody production and their cytolytic potential. For the first time we provide evidence that gastric mucosa of PA patients harbour a high proportion (20%) of autoreactive activated CD4+ T-cell clones that specifically recognize IF. Most of these clones (94%) showed a Th17 or Th1 profile. Virtually all IF-specific clones produced TNFα, IL-21 and provided substantial help for B-cell immunoglobulin production. Most mucosa-derived IF-specific T-cell clones expressed perforin-mediated cytotoxicity and induced Fas-Fas ligand-mediated apoptosis in target cells. Altogether, our results suggest that chronic autoantigen-induced T cell– dependent B-cell activation is responsible for the local synthesis of IF autoantibodies found in the sera and indicate that activation of IF-specific Th17 and Th1 T cells in the gastric mucosa represent a key effector mechanism in PA suggesting that the Th17/Th1 pathway may represent a novel target for the prevention and treatment of the disease.

Production of Peanut-Specific IgE in a Food Allergy Model Is Promoted by T Follicular Regulatory Cells Via an IL-10-Dependent Pathway

Abstract T follicular regulatory (TFR) cells are a specialized subset of Foxp3+ T cells found within the germinal center (GC) reaction and its role remains controversial. Here, we have used a peanut allergy model in mice to examine the role of TFR cells in controlling the production of antigen-specific IgE and IgE-controlled anaphylaxis. Using a mouse model with a specific loss of TFR cells (Foxp3-cre Bcl6-flox mice), we found TFR cells play an essential role in promoting and maintaining GC B cells, IgE production and anaphylaxis. Compared to control mice, TFR-deficient mice lacked circulating peanut-specific IgE four weeks after the priming period and anaphylactic responses were significantly weakened. The loss of IgE in TFR-deficient mice coincided with a marked decrease in GC B cells and peanut-specific IgG1. Similarly, deletion of regulatory T cells using FOXP3DTR mice abolished peanut-specific IgE and IgG1 responses. We identified a positive role for TFR cells in the IgE response using Foxp3-cre Pten-flox mice, which have augmented TFR cell responses, higher peanut-specific IgE and increased GC B cells. Mechanistically, TFR cells require Blimp1 controlled IL-10 to promote GC B cell survival and IgE production. Further studies using mice deficient of IL-10Ra (Mb1-cre Il10ra-flox mice) showed IL-10 signaling was pivotal for GC B and Ab responses. Blocking IL-10 signals in vivo mimicked the loss of IgE levels in TFR-deficient mice and rescued mice from anaphylaxis. Our data unexpectedly show that TFR cells have a critical helper function in the production of GC-dependent IgE, in part by producing IL-10. These studies have provided greater understanding of how allergic immune responses are controlled by the GC reaction.

Interleukin-17/Interleukin-21 and Interferon-γ producing T cells specific for β2 Glycoprotein I in atherosclerosis inflammation of systemic lupus erythematosus patients with antiphospholipid syndrome.

Systemic lupus erythematosus is frequently associated with antiphospholipid syndrome. Patients with lupus-antiphospholipid syndrome are characterized by recurrent arterial/venous thrombosis, miscarriages, and persistent presence of autoantibodies against phospholipid-binding proteins, such as β2-Glycoprotein I. We investigated the cytokine production induced by β2-Glycoprotein I in activated T cells that infiltrate in vivo atherosclerotic lesions of lupus-antiphospholipid syndrome patients. We examined the helper function of β2-Glycoprotein I-specific T cells for tissue factor production, as well as their cytolytic potential and their helper function for antibody production. Lupus-antiphospholipid syndrome patients harbor in vivo activated CD4+ T cells that recognize β2-Glycoprotein I in atherosclerotic lesions. β2-Glycoprotein I induces T-cell proliferation and expression of both Interleukin-17/Interleukin-21 and Interferon-γ in plaque-derived T-cell clones. β2-Glycoprotein I-specific T cells display strong help for monocyte tissue factor production, and promote antibody production in autologous B cells. Moreover, plaque-derived β2-Glycoprotein I-specific CD4+ T lymphocytes express both perforin-mediated and Fas/FasLigand-mediated-cytotoxicity. Altogether, our results indicate that β2-Glycoprotein I is able to elicit a local Interleukin-17/Interleukin-21 and Interferon-γ inflammation in lupus-antiphospholipid syndrome patients that might lead, if unabated, to plaque instability and subsequent arterial thrombosis, suggesting that the T helper 17/T helper 1 pathway may represent a novel target for the prevention and treatment of the disease.

TFH cells in bystander and cognate interactions with B cells.

Follicular T-helper (TFH ) cells play a crucial role in three aspects of the germinal center (GC) response. They promote GC formation, arbitrate competition among GC B cells to determine the outcome of affinity maturation, and regulate GC output of memory and plasma cells to shape the long-lived humoral immune memory. Of fundamental importance are dynamic physical interactions between TFH and B cells, which are the main platform for TFH cells to deliver "help" factors to B cells and also for reciprocal signaling from B cells to maintain the helper state of TFH cells. Recent work has significantly expanded our understanding of how T-B interactions are spatiotemporally regulated and molecularly orchestrated to fulfill those TFH functions. In this review, we elaborate two modes of T-B interactions, the antigen-specific or cognate mode in which TFH cells engage individual antigen-presenting B cells and the antigen nonspecific bystander mode in which TFH cells are engaged with the ensemble of follicular B cells. We discuss findings that indicate how short-lived cognate T-B contacts coupled with an intercellular positive feedback drive affinity-based selection and how bystander interactions between T and B cells regulate follicular T-cell recruitment and maintenance of an appropriate helper state. We argue that this combination of bystander and cognate interactions with B cells constantly shapes the internal state of TFH cells and provides the platform to execute their helper functions.