bluuebunny/crossref_metadata_2025 huggingface dataset:
Inchoate CD8+ T Cell Responses in Neonatal Mice Permit Influenza-Induced Persistent Pulmonary Dysfunction
Authors: You Dahui , Ripple Michael , Balakrishna Shrilatha , Troxclair Dana , Sandquist Dane , Ding Liren , Ahlert Terry A. , Cormier Stephania A.
Published: April 2014

Influenza infection remains a significant cause of pulmonary morbidity and mortality worldwide, with the highest hospitalization and mortality rates occurring in infants and elder adults. The mechanisms inducing this considerable morbidity and mortality are largely unknown. To address this question, we established a neonatal mouse model of influenza infection to test the hypothesis that the immaturity of the neonatal immune system is responsible for the severe pulmonary disease observed in infants. Seven-day-old mice were infected with influenza A virus (H1N1) and allowed to mature. As adults, these mice showed enhanced airway hyperreactivity, chronic pulmonary inflammation, and diffuse emphysematous-type lesions in the lungs. The adaptive immune responses of the neonates were much weaker than those of adults. This insufficiency appeared to be in both magnitude and functionality and was most apparent in the CD8+ T cell population. To determine the role of neonatal CD8+ T cells in disease outcome, adult, naive CD8+ T cells were adoptively transferred into neonates before infection. Neonatal mice receiving the adult CD8+ T cells had significantly lower pulmonary viral titers and greatly improved pulmonary function as adults (airway resistance similar to SHAM). Additional adoptive transfer studies using adult CD8+ T cells from IFN-γ-deficient mice demonstrated the importance of IFN-γ from CD8+ T cells in controlling the infection and in determining disease outcome. Our data indicate that neonates are more vulnerable to severe infections due to immaturity of their immune system and emphasize the importance of vaccination in infants.
PKCβΙΙ Augments NF-κB-Dependent Transcription at the CCL11 Promoter via p300/CBP-Associated Factor Recruitment and Histone H4 Acetylation
Authors: Clarke Deborah L. , Sutcliffe Amy , Deacon Karl , Bradbury Dawn , Corbett Lisa , Knox Alan J.
Published: April 2014

The transcription factor NF-κB plays a pivotal role in regulating inflammatory gene expression. Its effects are optimized by various coactivators, including histone acetyltransferases (HATs) such as CREB-binding protein/p300 and p300/CBP-associated factor (p/CAF). The molecular mechanisms regulating cofactor recruitment are poorly understood. In this study, we describe a novel role for protein kinase C (PKC) βΙΙ in augmenting NF-κB-mediated TNF-α-induced transcription of the target gene CCL11 in human airway smooth muscle cells by phosphorylating the HAT p/CAF. Studies using reporters, overexpression strategies, kinase-dead and HAT-defective mutants, and chromatin immunoprecipitation showed that PKCβII activation was not involved in NF-κB translocation, but facilitated NF-κB-mediated CCL11 transcription by colocalizing with and phosphorylating p/CAF, and thereby acetylating histone H4 and promoting p65 association with the CCL11 promoter. The effect was dependent on p/CAF’s HAT activity. Furthermore, mouse embryonic fibroblasts from PKCβ knockout mice showed markedly reduced TNF-α-induced CCL11 expression and NF-κB reporter activity that was restored on PKCβII overexpression, suggesting a critical role for this pathway. These data suggest a novel important biological role for PKCβΙΙ in NF-κB-mediated CCL11 transcription by p/CAF activation and histone H4 acetylation.
Gp130 Signaling Promotes Development of Acute Experimental Colitis by Facilitating Early Neutrophil/Macrophage Recruitment and Activation
Authors: Sander Leif E. , Obermeier Florian , Dierssen Uta , Kroy Daniela C. , Singh Anurag K. , Seidler Ursula , Streetz Konrad L. , Lutz Holger H. , Müller Werner , Tacke Frank , Trautwein Christian
Published: April 2014

IL-6 is known to play a crucial role in the pathogenesis of chronic intestinal inflammation by modulating T cell functions. In this study, we investigated the role of gp130, the common signal transducer for all IL-6 cytokines, in a murine model of acute T cell independent colitis to better characterize the impact of gp130 on innate immune cells and the early stages of inflammation. Experimental colitis was induced by dextran sulfate sodium treatment of mice with inducible systemic deletion of gp130 (MxCre/gp130−/−), macrophage/neutrophil-specific gp130-deficiency (LysCre/gp130−/−), or bone marrow chimeric mice and compared with wild-type controls (gp130f/f). Systemic deletion of gp130 (MxCre/gp130−/−) protected mice from severe colitis and wasting and attenuated the mucosal inflammatory infiltrate as well as local cytokine, chemokine, and adhesion molecule expression. Experiments in newly generated macrophage/neutrophil-specific gp130-deleted animals (LysCre/gp130−/−) and gp130 bone marrow chimeric mice, revealed a dual mechanism of proinflammatory effects mediated by gp130. Leukocyte recruitment was impaired in gp130-deleted animals and gp130-deleted recipients of wild-type bone marrow, demonstrating a central role of gp130-dependent signals in nonmyeloid cells for directing leukocytes to sites of inflammation, which was further confirmed in a model of sterile peritonitis. In contrast, macrophage/neutrophil-specific gp130 deficiency delayed and attenuated the disease but only marginally affected the inflammatory infiltrate, indicating a defective activation of mucosal leukocytes. We provide evidence that IL-6 cytokines acting via gp130 are required in the acute stages of intestinal inflammation by modulating the dynamics of innate immune cell recruitment and activation.
Production of C5a by ASP, a Serine Protease Released from Aeromonas sobria
Authors: Nitta Hidetoshi , Imamura Takahisa , Wada Yoshihiro , Irie Atsushi , Kobayashi Hidetomo , Okamoto Keinosuke , Baba Hideo
Published: April 2014

Aeromonas sobria causes pus and edema at sites of infection. However, the mechanisms underlying these effects have not been elucidated. C5a, the amino-terminal fragment of the complement 5th component (C5), mimics these events. To investigate the involvement of C5a in the pathophysiology of A. sobria infection, we examined release of C5a from human C5 by a serine protease (ASP), a putative virulence factor secreted by this bacterium. C5 incubated with enzymatically active ASP induced neutrophil migration in a dose-dependent manner from an ASP concentration of 3 nM and in an incubation time-dependent manner in as little as 7 min, with neutrophil accumulation in guinea pigs at intradermal injection sites and neutrophil superoxide release. These effects on neutrophils were inhibited by a C5a-receptor antagonist. The ASP incubation mixture with C5 but not C3 elicited vascular leakage in a dose- and incubation time-dependent manner, which was inhibited by a histamine H1-receptor antagonist. Together with these C5a-like activities, ASP cleaved C5 to release only one C5a Ag, the m.w. of which was similar to that of C5a. Immunoblotting using an anti-C5a Ab revealed generation of a C5a-like fragment from human plasma incubated with ASP. These results suggest that ASP-elicited neutrophil migration and vascular leakage via C5a production from C5 could occur in vivo, which was supported by that ASP did not affect functions of C5a and neutrophil C5a receptor. Through C5a generation, ASP could be associated with the induction of pus and edema caused by infection with this bacterium.
Characterization of HLA Class II/Peptide-TCR Interactions of the Immunodominant T Cell Epitope in Art v 1, the Major Mugwort Pollen Allergen
Authors: Jahn-Schmid Beatrice , Sirven Philémon , Leb Victoria , Pickl Winfried F. , Fischer Gottfried F. , Gadermaier Gabriele , Egger Matthias , Ebner Christof , Ferreira Fatima , Maillére Bernard , Bohle Barbara
Published: April 2014

More than 95% of mugwort pollen-allergic individuals are sensitized to Art v 1, the major allergen in mugwort pollen. Interestingly, the CD4 T cell response to Art v 1 involves only one single immunodominant peptide, Art v 125–36 (KCIEWEKAQHGA), and is highly associated with the expression of HLA-DR1. Therefore, we investigated the molecular basis of this unusual immunodominance among allergens. Using artificial APC expressing exclusively HLA-DRB1*0101 and HLA-DRA*0101, we formally showed that DR1 acts as restriction element for Art v 125–36-specific T cell responses. Further assessment of binding of Art v 125–36 to artificial HLA-DR molecules revealed that its affinity was high for HLA-DR1. Amino acid I27 was identified as anchor residue interacting with DR molecules in pocket P1. Additionally, Art v 125–36 bound with high affinity to HLA-DRB1*0301 and *0401, moderately to HLA-DRB1*1301 and HLA-DRB5*0101, and weakly to HLA-DRB1*1101 and *1501. T cell activation was also inducible by Art v 125–36-loaded, APC-expressing HLA molecules other than DR1, indicating degeneracy of peptide binding and promiscuity of TCR recognition. Specific binding of HLA-DRB1*0101 tetramers containing Art v 119–36 allowed the identification of Art v 125–36-specific T cells by flow cytometry. In summary, the immunodominance of Art v 125–36 relies on its affinity to DR1, but is not dictated by it. Future investigations at the molecular HLA/peptide/TCR and cellular level using mugwort pollen allergy as a disease model may allow new insights into tolerance and pathomechanisms operative in type I allergy, which may instigate new, T cell-directed strategies in specific immunotherapy.
Memory B Cells and Pneumococcal Antibody After Splenectomy
Authors: Wasserstrom Heather , Bussel James , Lim Lony C.-L. , Cunningham-Rundles Charlotte
Published: April 2014

Splenectomized patients are susceptible to bloodstream infections with encapsulated bacteria, potentially due to loss of blood filtering but also defective production of anticarbohydrate Ab. Recent studies propose that a lack of Ab is related to reduced numbers of IgM+ CD27+ memory B cells found after splenectomy. To test this, we analyzed CD27+ memory B cell subsets, IgG, and IgM pneumococcal Ab responses in 26 vaccinated splenectomized subjects in comparison to memory B cell subsets and Ab responses in healthy controls. As shown previously, the splenectomized autoimmune subjects had fewer total, isotype switched, and IgM+ CD27+ memory B cells as compared with controls, but there was no difference in memory B cells subsets between controls and splenectomized subjects with spherocytosis. There was no difference between the geometric mean IgG Ab response between normal controls and splenectomized subjects (p = 0.51; p = 0.81). Control subjects produced more IgM Ab than splenectomized autoimmune subjects (p = 0.01) but the same levels as subjects with spherocytosis (p = 0.15.) There was no correlation between memory B cell subsets and IgG or IgM Ab responses for controls or splenectomized subjects. These data suggest that splenectomy alone may not be the sole reason for loss of memory B cells and reduced IgM antipneumococcal Ab. Because subjects with autoimmunity had splenectomy at a significantly older age than participants with spherocytosis, these data suggest that an age-related loss of extra splenic sites necessary for the maintenance or function of memory B cells may lead to impaired immunity in these subjects.
TGF-β Utilizes SMAD3 to Inhibit CD16-Mediated IFN-γ Production and Antibody-Dependent Cellular Cytotoxicity in Human NK Cells
Authors: Trotta Rossana , Col Jessica Dal , Yu Jianhua , Ciarlariello David , Thomas Brittany , Zhang Xiaoli , Allard Jeffrey , Wei Min , Mao Hsiaoyin , Byrd John C. , Perrotti Danilo , Caligiuri Michael A.
Published: April 2014

TGF-β can be a potent suppressor of lymphocyte effector cell functions and can mediate these effects via distinct molecular pathways. The role of TGF-β in regulating CD16-mediated NK cell IFN-γ production and antibody-dependent cellular cytotoxicity (ADCC) is unclear, as are the signaling pathways that may be utilized. Treatment of primary human NK cells with TGF-β inhibited IFN-γ production induced by CD16 activation with or without IL-12 or IL-2, and it did so without affecting the phosphorylation/activation of MAP kinases ERK and p38, as well as STAT4. TGF-β treatment induced SMAD3 phosphorylation, and ectopic overexpression of SMAD3 resulted in a significant decrease in IFN-γ gene expression following CD16 activation with or without IL-12 or IL-2. Likewise, NK cells obtained from smad3−/− mice produced more IFN-γ in response to CD16 activation plus IL-12 when compared with NK cells obtained from wild-type mice. Coactivation of human NK cells via CD16 and IL-12 induced expression of T-BET, the positive regulator of IFN-γ, and T-BET was suppressed by TGF-β and by SMAD3 overexpression. An extended treatment of primary NK cells with TGF-β was required to inhibit ADCC, and it did so by inhibiting granzyme A and granzyme B expression. This effect was accentuated in cells overexpressing SMAD3. Collectively, our results indicate that TGF-β inhibits CD16-mediated human NK cell IFN-γ production and ADCC, and these effects are mediated via SMAD3.
Plasmacytoid Dendritic Cells Take Up Opsonized Antigen Leading to CD4+ and CD8+ T Cell Activation In Vivo
Authors: Björck Pia , Beilhack Andreas , Herman Edward I. , Negrin Robert S. , Engleman Edgar G.
Published: April 2014

Plasmacytoid dendritic cells (pDC) are the body’s main source of IFN-α, but, unlike classical myeloid DC (myDC), they lack phagocytic activity and are generally perceived as playing only a minor role in Ag processing and presentation. We show that murine pDC, as well as myDC, express Fcγ receptors (CD16/CD32) and can use these receptors to acquire Ag from immune complexes (IC), resulting in the induction of robust Ag-specific CD4+ and CD8+ T cell responses. IC-loaded pDC stimulate CD4+ T cells to proliferate and secrete a mixture of IL-4 and IFN-γ, and they induce CD8+ T cells to secrete IL-10 as well as IFN-γ. In contrast, IC-loaded myDC induce both CD4+ and CD8+ T cells to secrete mainly IFN-γ. These results indicate that pDC can shape an immune response by acquiring and processing opsonized Ag, leading to a predominantly Th2 response.
Staphylococcus aureus-Induced Plasmacytoid Dendritic Cell Activation Is Based on an IgG-Mediated Memory Response
Authors: Parcina Marijo , Wendt Constanze , Goetz Friedrich , Zawatzky Rainer , Zähringer Ulrich , Heeg Klaus , Bekeredjian-Ding Isabelle
Published: April 2014

Type I IFNs represent a major antimicrobial defense mechanism due to their property of enhancing immune responses by priming both innate and adaptive immune cells. Plasmacytoid dendritic cells (pDC) are the major source of type I IFN in the human body and represent innate immune cells involved in first-line defense against invading pathogens. Although pDC activation has been extensively studied upon stimulation with synthetic TLR ligands, viruses, and intracellular bacteria, there is only scarce information on extracellular bacteria. In this study we show that the triggering of human pDC-derived IFN-α secretion by Staphylococcus aureus is independent of TLR2 and specific for coagulase-positive staphylococci. Specificity of the pDC response to S. aureus is independent of the bacterial virulence factors protein A and α-toxin but is mediated by Ag-specific IgG and CD32. S. aureus-induced pDC activation can be blocked by inhibitory DNA oligonucleotides and chloroquine, suggesting that engagement of TLR7/9 by bacterial nucleic acids after CD32-mediated uptake of these compounds may play a central role in this process. Altogether, we propose that in marked contrast to nonselective TLR2-dependent activation of most innate immune cells, pDC activation by S. aureus represents an Ag-specific memory response since it requires the presence of class-switched immunoglobulins.
TLR2 Expression in Astrocytes Is Induced by TNF-α- and NF-κB-Dependent Pathways
Authors: Phulwani Nirmal K. , Esen Nilufer , Syed Mohsin Md. , Kielian Tammy
Published: April 2014

Astrocytes participate in CNS innate immune responses as evident by their ability to produce a wide array of inflammatory mediators upon exposure to diverse stimuli. Although we have established that astrocytes use TLR2 to signal inflammatory mediator production in response to Staphylococcus aureus, a common etiological agent of CNS infections, the signal transduction pathways triggered by this pathogen and how TLR2 expression is regulated remain undefined. Three disparate inhibitors that block distinct steps in the NF-κB pathway, namely SC-514, BAY 11-7082, and caffeic acid phenethyl ester, attenuated NO, TNF-α, and CXCL2 release from S. aureus-activated astrocytes. Among these proinflammatory mediators, autocrine/paracrine TNF-α was pivotal for augmenting TLR2 expression, since receptor levels were not elevated in astrocytes isolated from TNF-α knockout mice upon bacterial exposure. Since TLR2 is critical for signaling astrocytic cytokine production in response to S. aureus, we evaluated the effect of TNF-α loss on proinflammatory mediator release. Interestingly, among the molecules assayed, only NO production was significantly attenuated in TNF-α knockout astrocytes compared with wild-type cells. Similar results were obtained following LPS treatment, suggesting that TNF-α is an important regulator of astrocytic TLR2 expression and NO release in response to diverse microbial stimuli. In addition, NF-κB inhibitors attenuated TNF-α-induced TLR2 expression in astrocytes. Overall, this study suggests that two important anti-bacterial effector molecules, TLR2 and NO, are regulated, in part, by NF-κB-dependent autocrine/paracrine effects of TNF-α in astrocytes.
High Sensitivity of Intestinal CD8+ T Cells to Nucleotides Indicates P2X7 as a Regulator for Intestinal T Cell Responses
Authors: Heiss Kirsten , Jänner Nathalie , Mähnß Birgit , Schumacher Valéa , Koch-Nolte Friedrich , Haag Friedrich , Mittrücker Hans-Willi
Published: April 2014

The purinoreceptor P2X7 is expressed on subsets of T cells and mediates responses of these cells to extracellular nucleotides such as ATP or NAD+. We identified P2X7 as a molecule highly up-regulated on conventional CD8αβ+ and unconventional CD8αα+ T cells of the intestinal epithelium of mice. In contrast, CD8+ T cells derived from spleen, mesenteric lymph nodes, and liver expressed only marginal levels of P2X7. However, P2X7 was highly up-regulated on CD8+ T cells from spleen and lymph nodes when T cells were activated in the presence of retinoic acid. High P2X7 expression on intestinal CD8+ T cells as well as on CD8+ T cells incubated with retinoic acid resulted in enhanced sensitivity of cells to extracellular nucleotides. Both cell populations showed a high level of apoptosis following incubation with NAD+ and the ATP derivative 2′,3′-O-(benzoyl-4-benzoyl)-ATP, and injection of NAD+ caused selective in vivo depletion of intestinal CD8+ T cells. Following oral infection with Listeria monocytogenes, P2X7-deficient mice showed similar CD8+ T cell responses in the spleen, but enhanced responses in the intestinal mucosa, when compared with similarly treated wild-type control mice. Overall, our observations define P2X7 as a new regulatory element in the control of CD8+ T cell responses in the intestinal mucosa.
CD8+ Th17 Mediate Costimulation Blockade-Resistant Allograft Rejection in T-bet-Deficient Mice
Authors: Burrell Bryna E. , Csencsits Keri , Lu Guanyi , Grabauskiene Svetlana , Bishop D. Keith
Published: April 2014

While studying Th responses induced by cardiac transplantation, we observed that mice deficient in the Th1 transcription factor T-bet (T-bet−/−) mount both Th1 and Th17 responses, whereas wild-type recipients mount only Th1 responses. Cells producing both IFN-γ and IL-17 were readily detectable within the rejecting graft of T-bet−/− recipients, but were absent from the spleen, indicating that the in vivo microenvironment influences Th function. In addition, disrupting CD40-CD40L costimulatory interactions was highly effective at prolonging allograft survival in WT mice, but ineffective in T-bet−/− recipients. In this study, we report that CD8+ Th17 mediate costimulation blockade-resistant rejection in T-bet−/− allograft recipients. Depleting CD8+ cells or neutralizing IL-17 or the Th17-inducing cytokine IL-6 ablated the Th17 response and reversed costimulation blockade-resistant graft rejection. Neutralizing IL-4 in IFN-γ−/− allograft recipients did not induce Th17, suggesting that T-bet, rather than IL-4 and IFN-γ (known inhibitors of Th17), plays a critical role in negatively regulating Th17 in the transplant setting.
Pretransplant Infusion of Mesenchymal Stem Cells Prolongs the Survival of a Semiallogeneic Heart Transplant through the Generation of Regulatory T Cells
Authors: Casiraghi Federica , Azzollini Nadia , Cassis Paola , Imberti Barbara , Morigi Marina , Cugini Daniela , Cavinato Regiane Aparecida , Todeschini Marta , Solini Samantha , Sonzogni Aurelio , Perico Norberto , Remuzzi Giuseppe , Noris Marina
Published: April 2014

In this study, we investigated whether mesenchymal stem cells (MSC) had immunomodulatory properties in solid organ allotransplantation, using a semiallogeneic heart transplant mouse model, and studied the mechanism(s) underlying MSC tolerogenic effects. Either single (portal vein, day −7) or double (portal vein, day −7 and tail vein, day −1) pretransplant infusions of donor-derived B6C3 MSC in B6 recipients induced a profound T cell hyporesponsiveness and prolonged B6C3 cardiac allograft survival. The protolerogenic effect was abrogated when donor-derived MSC were injected together with B6C3 hematopoietic stem cells (HSC), suggesting that HSC negatively impact MSC immunomodulatory properties. Both the induction (pretransplant) and the maintenance phase (>100 days posttransplant) of donor-derived MSC-induced tolerance were associated with CD4+CD25+Foxp3+ Treg expansion and impaired anti-donor Th1 activity. MSC-induced regulatory T cells (Treg) were donor-specific since adoptive transfer of splenocytes from tolerant mice prevented the rejection of fully MHC-mismatched donor-specific secondary allografts but not of third-party grafts. In addition, infusion of recipient-derived B6 MSC tolerized a semiallogeneic B6C3 cardiac allograft, but not a fully MHC-mismatched BALB/c graft, and expanded Treg. A double i.v. pretransplant infusion of recipient-derived MSC had the same tolerogenic effect as the combined intraportal/i.v. MSC infusions, which makes the tolerogenic protocol applicable in a clinical setting. In contrast, single MSC infusions given either peritransplant or 1 day after transplant were less effective. Altogether these findings indicate that MSC immunomodulatory properties require HSC removal, partial sharing of MHC Ags between the donor and the recipient and pretransplant infusion, and are associated with expansion of donor-specific Treg.
Defects in Skin γδ T Cell Function Contribute to Delayed Wound Repair in Rapamycin-Treated Mice
Authors: Mills Robyn E. , Taylor Kristen R. , Podshivalova Katie , McKay Dianne B. , Jameson Julie M.
Published: April 2014

Disruptions in the normal program of tissue repair can result in poor wound healing, which perturbs the integrity of barrier tissues such as the skin. Such defects in wound repair occur in transplant recipients treated with the immunosuppressant drug rapamycin (sirolimus). Intraepithelial lymphocytes, such as γδ T cells in the skin, mediate tissue repair through the production of cytokines and growth factors. The capacity of skin-resident T cells to function during rapamycin treatment was analyzed in a mouse model of wound repair. Rapamycin treatment renders skin γδ T cells unable to proliferate, migrate, and produce normal levels of growth factors. The observed impairment of skin γδ T cell function is directly related to the inhibitory action of rapamycin on mammalian target of rapamycin. Skin γδ T cells treated with rapamycin are refractory to IL-2 stimulation and attempt to survive in the absence of cytokine and growth factor signaling by undergoing autophagy. Normal wound closure can be restored in rapamycin-treated mice by addition of the skin γδ T cell-produced factor, insulin-like growth factor-1. These studies not only reveal that mammalian target of rapamycin is a master regulator of γδ T cell function but also provide a novel mechanism for the increased susceptibility to nonhealing wounds that occurs during rapamycin administration.
Elevating Calcium in Th2 Cells Activates Multiple Pathways to Induce IL-4 Transcription and mRNA Stabilization
Authors: Guo Liying , Urban Joseph F. , Zhu Jinfang , Paul William E.
Published: April 2014

PMA and ionomycin cause T cell cytokine production. We report that ionomycin alone induces IL-4 and IFN-γ, but not IL-2, from in vivo- and in vitro-generated murine Th2 and Th1 cells. Ionomycin-induced cytokine production requires NFAT, p38, and calmodulin-dependent kinase IV (CaMKIV). Ionomycin induces p38 phosphorylation through a calcium-dependent, cyclosporine A-inhibitable pathway. Knocking down ASK1 inhibits ionomycin-induced p38 phosphorylation and IL-4 production. Ionomycin also activates CaMKIV, which, together with p38, induces AP-1. Cooperation between AP-1 and NFAT leads to Il4 gene transcription. p38 also regulates IL-4 production by mRNA stabilization. TCR stimulation also phosphorylates p38, partially through the calcium-dependent pathway; activated p38 is required for optimal IL-4 and IFN-γ.
SAP Enables T Cells to Help B Cells by a Mechanism Distinct from Th Cell Programming or CD40 Ligand Regulation
Authors: Kamperschroer Cris , Roberts Deborah M. , Zhang Yongqing , Weng Nan-ping , Swain Susan L.
Published: April 2014

Genetic mutations disrupting the function of signaling lymphocytic activation molecule-associated protein (SAP) lead to T cell intrinsic defects in T cell-dependent Ab responses. To better understand how SAP enables Th cells to help B cells, we first assessed whether molecules important for B cell help are dysregulated in SAP-deficient (SAP knockout (KO)) mice. CD40 ligand (CD40L) expression was enhanced on unpolarized SAP KO T cells; however, Th2 polarization returned their CD40L expression to wild-type levels without rescuing their ability to help B cells. CD40L also localized normally to the site of contact between SAP KO T cells and Ag-bearing B cells. Finally, CD40L-deficient Th cells and SAP KO Th cells differed in their abilities to help B cells in vitro. These data argue that Ab defects caused by SAP deficiency do not result from a loss of CD40L regulation or CD40L function on CD4 T cells. SAP KO Th cells additionally displayed normal patterns of migration and expression of ICOS and CXCR5. Global gene expression was remarkably similar in activated SAP KO vs wild-type T cells, prompting us to investigate whether SAP is necessary for “programming” T cells to become B cell helpers. By restricting SAP expression during differentiation, we determined that SAP is not required during the first 5 days of T cell activation/differentiation to generate Th cells capable of helping B cells. Instead, SAP is necessary for very late stages of differentiation or, most likely, for allowing Th cells to communicate during cognate T:B interactions.
Effector Mechanisms of the Autoimmune Syndrome in the Murine Model of Autoimmune Polyglandular Syndrome Type 1
Authors: DeVoss Jason J. , Shum Anthony K. , Johannes Kellsey P. A. , Lu Wen , Krawisz Anna K. , Wang Peter , Yang Ting , LeClair Norbert P. , Austin Cecilia , Strauss Erich C. , Anderson Mark S.
Published: April 2014

Mutations in the Aire gene result in a clinical phenomenon known as Autoimmune Polyglandular Syndrome (APS) Type I, which classically manifests as a triad of adrenal insufficiency, hypoparathyroidism, and chronic mucocutaneous infections. In addition to this triad, a number of other autoimmune diseases have been observed in APS1 patients including Sjögren’s syndrome, vitiligo, alopecia, uveitis, and others. Aire-deficient mice, the animal model for APS1, have highlighted the role of the thymus in the disease process and demonstrated a failure in central tolerance in aire-deficient mice. However, autoantibodies have been observed against multiple organs in both mice and humans, making it unclear what the specific role of B and T cells are in the pathogenesis of disease. Using the aire-deficient mouse as a preclinical model for APS1, we have investigated the relative contribution of specific lymphocyte populations, with the goal of identifying the cell populations which may be targeted for rational therapeutic design. In this study, we show that T cells are indispensable to the breakdown of self-tolerance, in contrast to B cells which play a more limited role in autoimmunity. Th1 polarized CD4+ T cells, in particular, are major contributors to the autoimmune response. With this knowledge, we go on to use therapies targeted at T cells to investigate their ability to modulate disease in vivo. Depletion of CD4+ T cells using a neutralizing Ab ameliorated the disease process. Thus, therapies targeted specifically at the CD4+ T cell subset may help control autoimmune disease in patients with APS1.
An Atypical NF-κB-Regulated Pathway Mediates Phorbol Ester-Dependent Heme Oxygenase-1 Gene Activation in Monocytes
Authors: Naidu Srivatsava , Wijayanti Nastiti , Santoso Sentot , Kietzmann Thomas , Immenschuh Stephan
Published: April 2014

Heme oxygenase (HO)-1 catalyzes the rate-limiting step of heme degradation and plays an important anti-inflammatory role via its enzymatic products carbon monoxide and biliverdin. In this study it is reported that the HO-1 gene is transcriptionally induced by the phorbol ester PMA in cell cultures of monocytic cells with a regulatory pattern that is different from that of LPS-dependent HO-1 induction in these cells. Activation of HO-1 by PMA was mediated via a newly identified κB element of the proximal rat HO-1 gene promoter region (−284 to −275). This HO-κB element was a nuclear target for the NF-κB subunit p65/RelA as determined by nuclear binding assays and transfection experiments with luciferase reporter gene constructs in RAW264.7 monocytes. Moreover, PMA-dependent induction of endogenous HO-1 gene expression and promoter activity was abrogated in embryonic fibroblasts from p65−/− mice. PMA-dependent HO-1 gene activation was reduced by an overexpressed dominant negative mutant of IκBα, but not by dominant negative IκB kinase-2, suggesting that the classical NF-κB pathway was not involved in this regulation. The antioxidant N-acetylcysteine and inhibitors of p38 MAPK or serine/threonine kinase CK2 blocked PMA-dependent HO-1 gene activation. Finally, it is demonstrated by luciferase assays with a Gal4-CHOP fusion protein that the activation of p38 MAPK by PMA was independent of CK2. Taken together, induction of HO-1 gene expression by PMA is regulated via an IκB kinase-independent, atypical NF-κB pathway that is mediated via the activation of p38 MAPK and CK2.
Characterization of T Cell Responses to the RgpA-Kgp Proteinase-Adhesin Complexes of Porphyromonas gingivalis in BALB/c Mice
Authors: Tam Vivian , O'Brien-Simpson Neil M. , Pathirana Rishi D. , Frazer Leanne T. , Reynolds Eric C.
Published: April 2014

Porphyromonas gingivalis is a Gram-negative bacterium strongly associated with chronic periodontitis, an inflammatory oral disease. A major virulence factor common to all characterized strains of P. gingivalis is the RgpA-Kgp proteinase-adhesin complexes (RgpA-Kgp complexes). In this study, we investigated T cell proliferative and cytokine responses to the RgpA-Kgp complexes and identified T cell epitopes in BALB/c mice utilizing Pepscan methodology. T cell proliferative responses were found to be predominantly directed toward the proteinase catalytic domains. Eleven T cell epitopes were identified using RgpA-Kgp-primed lymph node T cells (IL-4 dominant) and 21 using an RgpA-Kgp-specific T cell line (IFN-γ dominant), with 5 T cell epitopes, including the immunodominant epitope peptide 22, common to both T cell populations. Peptide 22 (439ANYTAHGSETAWADP453) from the Kgp proteinase catalytic domain induced a Th2 cytokine response in mice, and peptide 22-primed T cells had a Th2 cytokine profile when stimulated with the RgpA-Kgp complexes. Truncation and alanine scanning of peptide 22 identified the minimum epitope (442TAHGSETAWA451), and residues His444, Glu447, and Trp450 as critical for T cell proliferation. With a view to vaccine development, peptide 22 was incorporated into a synthetic peptide polymer. Peptide 22 polymer induced strong T cell proliferation and crossreactivity to native RgpA-Kgp complexes. In conclusion, we have identified a major T cell epitope of P. gingivalis and established that antigenicity of the T cell epitope is retained when delivered as a peptide polymer. The strategies employed here may have potential in the development of a synthetic peptide vaccine for P. gingivalis.
Essential Involvement of CX3CR1-Mediated Signals in the Bactericidal Host Defense during Septic Peritonitis
Authors: Ishida Yuko , Hayashi Takahito , Goto Takatsugu , Kimura Akihiko , Akimoto Shigeru , Mukaida Naofumi , Kondo Toshikazu
Published: April 2014

Cecal ligation and puncture (CLP) caused septic peritonitis in wild-type (WT) mice, with ∼33% mortality within 7 days after the procedure. Concomitantly, the protein level of intraperitoneal CX3CL1/fractalkine was increased, with infiltration by CX3CR1-expressing macrophages into the peritoneum. CLP induced 75% mortality in CX3CR1-deficient (CX3CR1−/−) mice, which, however, exhibited a similar degree of intraperitoneal leukocyte infiltration as WT mice. Despite this, CX3CR1−/− mice exhibited impairment in intraperitoneal bacterial clearance, together with a reduction in the expression of intraperitoneal inducible NO synthase (iNOS) and bactericidal proinflammatory cytokines, including IL-1β, TNF-α, IFN-γ, and IL-12, compared with WT mice. Bactericidal ability of peritoneal phagocytes such as neutrophils and macrophages was consistently attenuated in CX3CR1−/− mice compared with WT mice. Moreover, when WT macrophages were stimulated in vitro with CX3CL1, their bactericidal activity was augmented in a dose-dependent manner, with enhanced iNOS gene expression and subsequent NO generation. Furthermore, CX3CL1 enhanced the gene expression of IL-1β, TNF-α, IFN-γ, and IL-12 by WT macrophages with NF-κB activation. Thus, CX3CL1-CX3CR1 interaction is crucial for optimal host defense against bacterial infection by activating bacterial killing functions of phagocytes, and by augmenting iNOS-mediated NO generation and bactericidal proinflammatory cytokine production mainly through the NF-κB signal pathway, with few effects on macrophage infiltration.
Liver X Receptor Agonists Increase Airway Reactivity in a Model of Asthma via Increasing Airway Smooth Muscle Growth
Authors: Birrell Mark A. , De Alba Jorge , Catley Matthew C. , Hardaker Elizabeth , Wong Sissie , Collins Michael , Clarke Deborah L. , Farrow Stuart N. , Willson Timothy M. , Collins Jon L. , Belvisi Maria G.
Published: April 2014

The liver X receptors (LXRα/β) are orphan nuclear receptors that are expressed in a large number of cell types and have been shown to have anti-inflammatory properties. Nuclear receptors have previously proved to be amenable targets for small molecular mass pharmacological agents in asthma, and so the effect of an LXR ligand was assessed in models of allergic airway inflammation. LXR agonist, GW 3965, was profiled in rat and mouse models of allergic asthma. In the Brown Norway rats, GW 3965 (3–30 mg/kg) was unable to reduce the bronchoalveolar lavage eosinophilia associated with this model and had no impact on inflammatory biomarkers (eotaxin and IL-1β). The compound did significantly stimulate ABCA-1 (ATP-binding cassette A1) mRNA expression, indicating that there was adequate exposure/LXR activation. In the mouse model, the LXR ligand surprisingly increased airway reactivity, an effect that was apparent in both the Ag and nonchallenged groups. This increase was not associated with a change in lung tissue inflammation or number of mucus-containing cells. There was, however, a marked increase in airway smooth muscle thickness in both treated groups. We demonstrated an increase in contractile response to exogenous methacholine in isolated airways taken from LXR agonist-treated animals compared with the relevant control tissue. We corroborated these findings in a human system by demonstrating increased proliferation of cultured airway smooth muscle. This phenomenon, if evidenced in man, would indicate that LXR ligands may directly increase airway reactivity, which could be detrimental, especially in patients with existing respiratory disease and with already compromised lung function.
TLR-2 and IL-17A in Chitin-Induced Macrophage Activation and Acute Inflammation
Authors: Da Silva Carla A. , Hartl Dominik , Liu Wei , Lee Chun G. , Elias Jack A.
Published: April 2014

Chitin is a ubiquitous polysaccharide in fungi, insects, and parasites. To test the hypothesis that chitin is an important immune modulator, we characterized the ability of chitin fragments to regulate murine macrophage cytokine production in vitro and induce acute inflammation in vivo. In this study, we show that chitin is a size-dependent stimulator of macrophage IL-17A production and IL-17AR expression and demonstrate that these responses are TLR-2 and MyD88-dependent. We further demonstrate that IL-17A pathway activation is an essential event in the stimulation of some but not all chitin-stimulated cytokines and that chitin uses a TLR-2, MyD88-, and IL-17A-dependent mechanism(s) to induce acute inflammation. These studies demonstrate that chitin is a size-dependent pathogen-associated molecular pattern that activates TLR-2 and MyD88 in a novel IL-17A/IL-17AR-based innate immunity pathway.
Hydrogen Sulfide Augments Neutrophil Migration through Enhancement of Adhesion Molecule Expression and Prevention of CXCR2 Internalization: Role of ATP-Sensitive Potassium Channels
Authors: Dal-Secco Daniela , Cunha Thiago M. , Freitas Andressa , Alves-Filho José Carlos , Souto Fabrício O. , Fukada Sandra Y. , Grespan Renata , Alencar Nylane M. N. , Neto Alberto F. , Rossi Marcos A. , Ferreira Sérgio H. , Hothersall John S. , Cunha Fernando Q.
Published: April 2014

In this study, we have addressed the role of H2S in modulating neutrophil migration in either innate (LPS-challenged naive mice) or adaptive (methylated BSA (mBSA)-challenged immunized mice) immune responses. Treatment of mice with H2S synthesis inhibitors, dl-propargylglycine (PAG) or β-cyanoalanine, reduced neutrophil migration induced by LPS or methylated BSA (mBSA) into the peritoneal cavity and by mBSA into the femur/tibial joint of immunized mice. This effect was associated with decreased leukocyte rolling, adhesion, and P-selectin and ICAM-1 expression on endothelium. Predictably, treatment of animals with the H2S donors, NaHS or Lawesson’s reagent, enhanced these parameters. Moreover, the NaHS enhancement of neutrophil migration was not observed in ICAM-1-deficient mice. Neither PAG nor NaHS treatment changed LPS-induced CD18 expression on neutrophils, nor did the LPS- and mBSA-induced release of neutrophil chemoattractant mediators TNF-α, keratinocyte-derived chemokine, and LTB4. Furthermore, in vitro MIP-2-induced neutrophil chemotaxis was inhibited by PAG and enhanced by NaHS treatments. Accordingly, MIP-2-induced CXCR2 internalization was enhanced by PAG and inhibited by NaHS treatments. Moreover, NaHS prevented MIP-2-induced CXCR2 desensitization. The PAG and NaHS effects correlated, respectively, with the enhancement and inhibition of MIP-2-induced G protein-coupled receptor kinase 2 expression. The effects of NaHS on neutrophil migration both in vivo and in vitro, together with CXCR2 internalization and G protein-coupled receptor kinase 2 expression were prevented by the ATP-sensitive potassium (KATP+) channel blocker, glybenclamide. Conversely, diazoxide, a KATP+ channel opener, increased neutrophil migration in vivo. Together, our data suggest that during the inflammatory response, H2S augments neutrophil adhesion and locomotion, by a mechanism dependent on KATP+ channels.
Endogenous Hydrogen Sulfide Regulates Inflammatory Response by Activating the ERK Pathway in Polymicrobial Sepsis
Authors: Zhang Huili , Moochhala Shabbir M. , Bhatia Madhav
Published: April 2014

Hydrogen sulfide (H2S) up-regulates inflammatory response in several inflammatory diseases. However, to date, little is known about the molecular mechanism by which H2S provokes the inflammatory response in sepsis. Thus, the aim of this study was to investigate the signaling pathway underlying the proinflammatory role of H2S in cecal ligation and puncture (CLP)-induced sepsis. Male Swiss mice were subjected to CLP and treated with dl-propargylglycine (PAG; 50 mg/kg i.p., an inhibitor of H2S formation), NaHS (10 mg/kg, i.p., an H2S donor), or saline. PAG was administered 1 h before CLP, whereas NaHS was given at the time of CLP. CLP-induced sepsis resulted in a time-dependent increase in the synthesis of endogenous H2S. Maximum phosphorylation of ERK1/2 and degradation of IκBα in lung and liver were observed 4 h after CLP. Inhibition of H2S formation by PAG significantly reduced the phosphorylation of ERK1/2 in lung and liver 4 h after CLP, coupled with decreased degradation of IκBα and activation of NF-κB. In contrast, injection of NaHS significantly enhanced the activation of ERK1/2 in lung and liver, therefore leading to a further rise in tissue NF-κB activity. As a result, pretreatment with PAG significantly reduced the production of cytokines and chemokines in sepsis, whereas exogenous H2S greatly increased it. In addition, pretreatment with PD98059, an inhibitor of ERK kinase (MEK-1), significantly prevented NaHS from aggravating systemic inflammation in sepsis. In conclusion, the present study shows for the first time that H2S may regulate systemic inflammatory response in sepsis via ERK pathway.
Cross-Tolerization between Nod1 and Nod2 Signaling Results in Reduced Refractoriness to Bacterial Infection in Nod2-Deficient Macrophages
Authors: Kim Yun-Gi , Park Jong-Hwan , Daignault Stephanie , Fukase Koichi , Núñez Gabriel
Published: April 2014

Nod2 is an intracellular innate immune receptor that plays a role in host defense and susceptibility to inflammatory disease. We show in this study that macrophages rendered refractory to TLR4 and Nod2 signaling by exposure to LPS and muramyl dipeptide (MDP) exhibit impaired TNF-α and IL-6 production in response to pathogenic Listeria monocytogenes and Yersinia pseudotuberculosis as well as commensal bacteria including Escherichia coli and Bacteroides fragilis. Surprisingly, Nod2 deficiency was associated with impaired tolerization in response to pathogenic and commensal bacteria. Mechanistically, reduced tolerization of Nod2-null macrophages was mediated by recognition of bacteria through Nod1 because it was abolished in macrophages deficient in Nod1 and Nod2. Consistently, Nod2-null macrophages tolerant to LPS and MDP showed enhanced production of TNF-α and IL-6 as well as increased NF-κB and MAPK activation in response to the dipeptide KF1B, the Nod1 agonist. Furthermore, reduced tolerization of Nod2-deficient macrophages in response to bacteria was abolished when mutant macrophages were also rendered tolerant to the Nod1 ligand. Finally, MDP stimulation induced refractoriness not only to MDP, but also to iE-DAP stimulation, providing a mechanism to explain the reduced tolerization of Nod2-deficient macrophages infected with bacteria. These results demonstrate that cross-tolerization between Nod1 and Nod2 leads to increase recognition of both pathogenic and commensal bacteria in Nod2-deficient macrophages pre-exposed to microbial ligands.
Evidence for an Association between Thyroid-Stimulating Hormone and Insulin-Like Growth Factor 1 Receptors: A Tale of Two Antigens Implicated in Graves’ Disease
Authors: Tsui Shanli , Naik Vibha , Hoa Neil , Hwang Catherine J. , Afifiyan Nikoo F. , Sinha Hikim Amiya , Gianoukakis Andrew G. , Douglas Raymond S. , Smith Terry J.
Published: April 2014

Thyroid-stimulating hormone receptor (TSHR) plays a central role in regulating thyroid function and is targeted by IgGs in Graves’ disease (GD-IgG). Whether TSHR is involved in the pathogenesis of thyroid-associated ophthalmopathy (TAO), the orbital manifestation of GD, remains uncertain. TSHR signaling overlaps with that of insulin-like grow factor 1 receptor (IGF-1R). GD-IgG can activate fibroblasts derived from donors with GD to synthesize T cell chemoattractants and hyaluronan, actions mediated through IGF-1R. In this study, we compare levels of IGF-1R and TSHR on the surfaces of TAO and control orbital fibroblasts and thyrocytes and explore the physical and functional relationship between the two receptors. TSHR levels are 11-fold higher on thyrocytes than on TAO or control fibroblasts. In contrast, IGF-1R levels are 3-fold higher on TAO vs control fibroblasts. In pull-down studies using fibroblasts, thyrocytes, and thyroid tissue, Abs directed specifically against either IGF-1Rβ or TSHR bring both proteins out of solution. Moreover, IGF-1Rβ and TSHR colocalize to the perinuclear and cytoplasmic compartments in fibroblasts and thyrocytes by confocal microscopy. Examination of orbital tissue from patients with TAO reveals similar colocalization to cell membranes. Treatment of primary thyrocytes with recombinant human TSH results in rapid ERK phosphorylation which can be blocked by an IGF-1R-blocking mAb. Our findings suggest that IGF-1R might mediate some TSH-provoked signaling. Furthermore, they indicate that TSHR levels on orbital fibroblasts are considerably lower than those on thyrocytes and that this receptor associates with IGF-1R in situ and together may comprise a functional complex in thyroid and orbital tissue.
Cutting Edge: CD25+ Regulatory T Cells Prevent Expansion and Induce Apoptosis of B Cells Specific for Tissue Autoantigens
Authors: Ludwig-Portugall Isis , Hamilton-Williams Emma E. , Gottschalk Catherine , Kurts Christian
Published: April 2014

To study the role of CD25+ regulatory T cells (Tregs) in peripheral B cell tolerance, we generated transgenic rat insulin promoter RIP-OVA/HEL mice expressing the model Ags OVA and HEL in pancreatic islet β cells (where RIP is rat insulin promoter and HEL is hen egg lysozyme). Adoptively transferred transgenic OVA-specific CD4+ and CD8+ T cells proliferated only in the autoantigen-draining pancreatic lymph node (PLN), demonstrating pancreas-specific Ag expression. Transferred HEL-specific transgenic B cells (IgHEL cells) disappeared within 3 wk from transgenic but not from nontransgenic mice immunized with autoantigen. Depletion of CD25+ FoxP3+ cells completely restored IgHEL cell numbers. Treg exerted an analogous suppressive effect on endogenous HEL-specific autoreactive B cells. Tregs acted by inhibiting the proliferation of IgHEL cells in the spleen and PLN and by systemic induction of their apoptosis. Furthermore, they reduced BCR and MHC II surface expression on IgHEL cells in the PLN. These findings demonstrate that autoreactive B cells specific for a nonlymphoid tissue autoantigen are controlled by Tregs.