bluuebunny/crossref_metadata_2025 huggingface dataset:
Umbilical Cord Blood T Cells Express Multiple Natural Cytotoxicity Receptors after IL-15 Stimulation, but Only NKp30 Is Functional
Authors: Tang Qin , Grzywacz Bartosz , Wang Hongbo , Kataria Nandini , Cao Qing , Wagner John E. , Blazar Bruce R. , Miller Jeffrey S. , Verneris Michael R.
Published: April 2014

The natural cytotoxicity receptors (NCRs) NKp30, NKp44, and NKp46 are thought to be NK lineage restricted. Herein we show that IL-15 induces NCR expression on umbilical cord blood (UCB) T cells. NCRs were mainly on CD8+ and CD56+ UCB T cells. Only NKp30 was functional as demonstrated by degranulation, IFN-γ release, redirected killing, and apoptosis. Since NCRs require adaptor proteins for function, the expressions of these adaptors were determined. The adaptors used by NKp30 and NKp46, FcεR1γ and CD3ζ, were detected in UCB T cells. There was a near absence of DAP12, the adaptor for NKp44, consistent with a hypofunctional state. NKp46 was on significantly fewer UCB T cells, possibly accounting for its lack of function. Adult peripheral blood (PB) T cells showed minimal NCR acquisition after culture with IL-15. Since UCB contains a high frequency of naive T cells, purified naive T cells from adult PB were tested. Although NKp30 was expressed on a small fraction of naive PB T cells, it was nonfunctional. In contrast to UCB, PB T cells lacked FcεR1γ expression. These results demonstrate differences between UCB and PB T cells regarding NCR expression and function. Such findings challenge the concept that NCRs are NK cell specific.
Regulatory T Cells Prevent Transfer of Type 1 Diabetes in NOD Mice Only When Their Antigen Is Present In Vivo
Authors: Tonkin Daniel R. , He Jing , Barbour Gene , Haskins Kathryn
Published: April 2014

Regulatory T cells (Tregs) can potentially be used as tools to suppress pathogenic T cells in autoimmune diseases such as type 1 diabetes. For use in therapy it is critically important to determine whether suppression by Tregs requires a population specific for the target of autoimmunity, such as pancreatic β cells in type 1 diabetes. Current reports in the NOD mouse model of type 1 diabetes are in conflict as to whether suppression of disease by Tregs is Ag-dependent. We have addressed this question by evaluating the effects of islet-specific TGF-β-induced Tregs in recipient mice in which the Treg Ag is either present or absent. Our data show that Treg numbers in pancreas are reduced in the absence of Ag and that there are Ag-dependent differences in the effects of Tregs on pathogenic T cells in the pancreas. By examining protection from diabetes induced by T cell transfer, we have clearly demonstrated that Tregs suppress only in the presence of their Ag and not in mice in which the islets lack the Treg Ag. Our results also suggest that in sufficiently large populations of polyclonal Tregs, there will be adequate numbers of islet-specific Tregs to suppress diabetes.
Promoter Analysis Reveals Critical Roles for SMAD-3 and ATF-2 in Expression of IL-23 p19 in Macrophages
Authors: Al-Salleeh Fahd , Petro Thomas M.
Published: April 2014

IL-23 p19/p40, produced by macrophages and dendritic cells, is critical for development of Th17 in several autoimmune diseases. In this study, bone marrow-derived (BMM) and splenic macrophages (SPM) from SJL/J mice, susceptible to autoimmune demyelinating disease following Theiler’s virus (TMEV) infection, expressed IL-23 in response to TMEV. We identified potential binding sites for IFN response factor (IRF)-3 (nt −734 to −731), Sma- and Mad-related protein (SMAD)-3 (nt −584 to −581), activating transcription factor (ATF)-2 (nt −571 to −568), IRF-7 (nt −533 to-525), and NF-κB (nt −215 to −209) in the murine p19 promoter. The p19prom in the pGL3 promoter-reporter vector responded to TMEV or poly(I:C), a TLR3 agonist in the RAW264.7 macrophage cell line. Deletions upstream from the IRF-3 site and mutations at the IRF-3, SMAD-3, ATF-2, or NF-κB, but not the IRF-7, sites significantly reduced promoter activity. ATF-2 or SMAD-3, but not IRF-3, short-hairpin RNA reduced p19 promoter activity and protein expression in RAW264.7 cells responding to TMEV. Chromosomal DNA immunoprecipitation assays revealed that SMAD-3 and ATF-2 bind to the endogenous p19 promoter in RAW264.7 cells and SJL/J SPM following challenge with TMEV. TGF-β1, which activates SMAD-3, was induced in RAW264.7 cells, BMM, and SPM by TMEV. Neutralizing Ab to TGF-β1 eliminated TMEV-induced IL-23 production and SMAD-3 activation in RAW264.7 cells, BMM, and SPM. Activation of ATF-2 was JNK, but not p38 or ERK MAPK dependent. Inhibition of the JNK, but also the ERK MAPK pathways decreased expression of p19. These results suggest that ATF-2 and SMAD-3 are transcription factors, which are, in addition to NF-κB, essential for IL-23 p19 expression.
Donor Deficiency of Decay-Accelerating Factor Accelerates Murine T Cell-Mediated Cardiac Allograft Rejection
Authors: Pavlov Vasile , Raedler Hugo , Yuan Shuguang , Leisman Staci , Kwan Wing-hong , Lalli Peter N. , Medof M. Edward , Heeger Peter S.
Published: April 2014

Decay-accelerating factor (DAF) is a cell surface regulator that accelerates the dissociation of C3/C5 convertases and thereby prevents the amplification of complement activation on self cells. In the context of transplantation, DAF has been thought to primarily regulate antibody-mediated allograft injury, which is in part serum complement-dependent. Based on our previously delineated link between DAF and CD4 T cell responses, we evaluated the effects of donor Daf1 (the murine homolog of human DAF) deficiency on CD8 T cell-mediated cardiac allograft rejection. MHC-disparate Daf1−/− allografts were rejected with accelerated kinetics compared with wild-type grafts. The accelerated rejection predominantly tracked with DAF’s absence on bone marrow-derived cells in the graft and required allograft production of C3. Transplantation of Daf1−/− hearts into wild-type allogeneic hosts augmented the strength of the anti-donor (direct pathway) T cell response, in part through complement-dependent proliferative and pro-survival effects on alloreactive CD8 T cells. The accelerated allograft rejection of Daf1−/− hearts occurred in recipients lacking anti-donor Abs. The results reveal that donor DAF expression, by controlling local complement activation on interacting T cell APC partners, regulates the strength of the direct alloreactive CD8+ T cell response. The findings provide new insights into links between innate and adaptive immunity that could be exploited to limit T cell-mediated injury to an allograft following transplantation.
T Cells from Leishmania major-Susceptible BALB/c Mice Have a Defect in Efficiently Up-Regulating CXCR3 upon Activation
Authors: Barbi Joseph , Brombacher Frank , Satoskar Abhay R.
Published: April 2014

Genetic background influences the outcome of Leishmania major infection. C57BL/6 mice mount a Th1 response and resolve infection. In contrast, BALB/c mice mount a Th2 response and develop chronic lesions. This susceptible phenotype is seen even though BALB/c mice generate IFN-γ-producing T cells at proportions similar to C57BL/6 mice in their lymph nodes (LN) early after infection. We had previously shown that chemokine receptor CXCR3 mediates immunity against L. major by recruiting IFN-γ-producing T cells to the lesions of C57BL/6 mice. Therefore, we hypothesized that IFN-γ-secreting T cells in BALB/c mice are unable to confer protection because they may be defective in up-regulating CXCR3. To test this hypothesis, we analyzed kinetics of CXCR3-expressing T cells in the LN and lesions of BALB/c and C57BL/6 mice during L. major infection. Additionally, we compared the ability of T cells from BALB/c and C57BL/6 mice to up-regulate CXCR3 upon activation. We found that resolution of L. major infection in C57BL/6 mice was associated with an increase in the proportion of CXCR3+ T cells in regional LN and lesions, whereas disease progression in BALB/c mice was associated with a decrease in these populations. Anti-CD3/CD28-activated T cells from naive BALB/c but not C57BL/6 mice were defective in up-regulating CXCR3. Impaired induction of CXCR3 on BALB/c T cells was not due to lack of IFN-γ and was mediated partially by IL-10 but not IL-4 or IL-13. We propose that defective CXCR3 up-regulation on T cells in BALB/c mice may contribute to L. major susceptibility.
Induction of a VLA-2 (CD49b)-Expressing Effector T Cell Population by a Cell-Based Neuroblastoma Vaccine Expressing CD137L
Authors: Yan Xiaocai , Johnson Bryon D. , Orentas Rimas J.
Published: April 2014

In malignancies where no universally expressed dominant Ag exists, the use of tumor cell-based vaccines has been proposed. We have modified a mouse neuroblastoma cell line to express either CD80 (B7.1), CD137L (4-1BBL), or both receptors on the tumor cell surface. Vaccines expressing both induce a strong T cell response that is unique in that among responding CD8 T cells, a T effector memory cell (TEM) response arises in which a large number of the TEM express the α-chain of VLA-2, CD49b. We demonstrate using both in vitro and in vivo assays that the CD49b+ CD8 T cell population is a far more potent antitumor effector cell population than nonfractionated CD8 or CD49b− CD8 T cells and that CD49b on vaccine-induced CD8 T cells mediates invasion of a collagen matrix. In in vivo rechallenge studies, CD49b+ T cells no longer expanded, indicating that CD49b TEM expansion is restricted to the initial response to vaccine. To demonstrate a mechanistic link between the expression of costimulatory molecules on the vaccine and CD49b on responding T cells, we stimulated naive T cells in vitro with artificial APC expressing different combinations of anti-CD3, anti-CD28, and CD137L. Although some mRNA encoding CD49b was induced by combining anti-CD3 with anti-CD28 or CD137L, the highest level was induced when all three signals were present. This indicates that CD49b expression results from additive costimulation and that the level of CD49b message serves as an indicator of the effectiveness of T cell activation by a cell-based vaccine.
Intrinsic and Induced Regulation of the Age-Associated Onset of Spontaneous Experimental Autoimmune Encephalomyelitis
Authors: Zhang Hong , Podojil Joseph R. , Luo Xunrong , Miller Stephen D.
Published: April 2014

Multiple sclerosis is characterized by perivascular CNS infiltration of myelin-specific CD4+ T cells and activated mononuclear cells. TCR transgenic mice on the SJL background specific for proteolipid protein (PLP)139–151 develop a high incidence of spontaneous experimental autoimmune encephalomyelitis (sEAE). We examined the intrinsic mechanisms regulating onset and severity of sEAE. CD4+ T cells isolated from the cervical lymph nodes, but not spleens, of diseased 5B6 transgenic mice are hyperactivated when compared with age-matched healthy mice and produce both IFN-γ and IL-17, indicating that the cervical lymph node is the initial peripheral activation site. The age-associated development of sEAE correlates with a decline in both the functional capacity of natural regulatory T cells (nTregs) and in PLP139–151-induced IL-10 production and a concomitant increase in IL-17 production. Anti-CD25-induced inactivation of nTregs increased the incidence and severity of sEAE. Conversely, induction of peripheral tolerance via the i.v. injection of PLP139–151-pulsed, ethylcarbodiimide-fixed APCs (PLP139–151-SP) inhibited the development of clinical disease concomitant with increased production of IL-10 and conversion of Foxp3+ Tregs from CD4+CD25− progenitors. These data indicate that heterogeneous populations of Tregs regulate onset of sEAE, and that induction of peripheral tolerance can be exploited to prevent/treat spontaneous autoimmune disease.
Swift Entry of Myelin-Specific T Lymphocytes into the Central Nervous System in Spontaneous Autoimmune Encephalomyelitis
Authors: Furtado Gláucia C. , Marcondes Maria Cecilia G. , Latkowski Jo-Ann , Tsai Julia , Wensky Allen , Lafaille Juan J.
Published: April 2014

Strong evidence supports that CNS-specific CD4+ T cells are central to the pathogenesis of multiple sclerosis and experimental autoimmune encephalomyelitis (EAE). Using a model of spontaneous EAE, we demonstrated that myelin basic protein (MBP)-specific CD4+ T cells up-regulate activation markers in the CNS-draining cervical lymph nodes at a time when there is no T cell activation anywhere else, including the CNS, and before the appearance of clinical signs. In spontaneous EAE, the number of MBP-specific T cell numbers does not build up gradually in the CNS; instead, a swift migration of IFN-γ-producing T cells into the CNS takes place ∼24 h before the onset of neurological signs of EAE. Surgical excision of the cervical lymph nodes in healthy pre-EAE transgenic mice delayed the onset of EAE and resulted in a less severe disease. In EAE induced by immunization with MBP/CFA, a similar activation of T cells in the draining lymph nodes of the injection site precedes the disease. Taken together, our results suggest that peripheral activation of T cells in draining lymph nodes is an early event in the development of EAE, which paves the way for the initial burst of IFN-γ-producing CD4+ T cell into the CNS.
Novel Role of IL-13 in Fibrosis Induced by Nonalcoholic Steatohepatitis and Its Amelioration by IL-13R-Directed Cytotoxin in a Rat Model
Authors: Shimamura Takeshi , Fujisawa Toshio , Husain Syed R. , Kioi Mitomu , Nakajima Atsushi , Puri Raj K.
Published: April 2014

Nonalcoholic steatohepatitis (NASH), the most common cause of chronic liver fibrosis, progresses to cirrhosis in up to 20% of patients. We report that hepatic stellate cells (HSC) in sinusoidal lesions of liver of patients with NASH express high levels of high-affinity IL-13R (IL-13Rα2), which is colocalized with smooth muscle actin, whereas fatty liver and normal liver specimens do not express IL-13Rα2. HSCs engineered to overexpress IL-13Rα2 respond to IL-13 and induce TGFB1 promoter activity and TGF-β1 production. We also developed NASH in rats by feeding a choline-deficient l-amino acid diet. These rats developed liver fibrosis as assessed by H&E staining, Masson’s trichrome and Sirius red staining, and hydroxyproline assays. Treatment of these rats with IL-13R-directed cytotoxin caused a substantial decline in fibrosis and liver enzymes without organ toxicity. These studies demonstrate that functional IL-13Rα2 are overexpressed in activated HSCs involved in NASH and that IL-13 cytotoxin ameliorates pathological features of NASH in rat liver, indicating a novel role of this cytotoxin in potential therapy.
A Novel Role for CD4+ T Cells in the Control of Cachexia
Authors: Wang Zhuangzhi , Zhao Chunfang , Moya Rosa , Davies Joanna D.
Published: April 2014

Cachexia is the dramatic weight loss and muscle atrophy seen in chronic disease states, including autoimmunity, cancer, and infection, and is often associated with lymphopenia. We have previously shown that CD4+ T cells that express the lowest density of CD44 (CD4+CD44v.low) are significantly reduced in diabetic NOD mice that are cachexic compared with diabetic mice that are not cachexic. Using this model, and a model of cancer cachexia, we test the hypothesis that CD4+CD44v.low cells play an active role in protecting the host from cachexia. CD4+CD44v.low cells, but not CD4+ cells depleted of CD44v.low cells, delay the onset of wasting when infused into either diabetic or prediabetic NOD recipients. However, no significant effect on the severity of diabetes was detected. In a model of cancer cachexia, they significantly reduce muscle atrophy, and inhibit muscle protein loss and DNA loss, even when given after the onset of cachexia. Protection from wasting and muscle atrophy by CD4+CD44v.low cells is associated with protection from lymphopenia. These data suggest, for the first time, a role for an immune cell subset in protection from cachexia, and further suggest that the mechanism of protection is independent of protection from autoimmunity.
Goblet Cell-Derived Resistin-Like Molecule β Augments CD4+ T Cell Production of IFN-γ and Infection-Induced Intestinal Inflammation
Authors: Nair Meera G. , Guild Katherine J. , Du Yurong , Zaph Colby , Yancopoulos George D. , Valenzuela David M. , Murphy Andrew , Stevens Sean , Karow Margaret , Artis David
Published: April 2014

The secreted goblet cell-derived protein resistin-like molecule β (RELMβ) has been implicated in divergent functions, including a direct effector function against parasitic helminths and a pathogenic function in promoting inflammation in models of colitis and ileitis. However, whether RELMβ influences CD4+ T cell responses in the intestine is unknown. Using a natural model of intestinal inflammation induced by chronic infection with gastrointestinal helminth Trichuris muris, we identify dual functions for RELMβ in augmenting CD4+ Th1 cell responses and promoting infection-induced intestinal inflammation. Following exposure to low-dose Trichuris, wild-type C57BL/6 mice exhibit persistent infection associated with robust IFN-γ production and intestinal inflammation. In contrast, infected RELMβ−/− mice exhibited a significantly reduced expression of parasite-specific CD4+ T cell-derived IFN-γ and TNF-α and failed to develop Trichuris-induced intestinal inflammation. In in vitro T cell differentiation assays, recombinant RELMβ activated macrophages to express MHC class II and secrete IL-12/23p40 and enhanced their ability to mediate Ag-specific IFN-γ expression in CD4+ T cells. Taken together, these data suggest that goblet cell-macrophage cross-talk, mediated in part by RELMβ, can promote adaptive CD4+ T cell responses and chronic inflammation following intestinal helminth infection.
IL-33 Induces Antigen-Specific IL-5+ T Cells and Promotes Allergic-Induced Airway Inflammation Independent of IL-4
Authors: Kurowska-Stolarska Mariola , Kewin Pete , Murphy Grace , Russo Remo C. , Stolarski Bartosz , Garcia Cristiana Couto , Komai-Koma Mousa , Pitman Nick , Li Yubin , McKenzie Andrew N. J. , Teixeira Mauro M. , Liew Foo Y. , Xu Damo
Published: April 2014

Type 2 cytokines (IL-4, IL-5, and IL-13) play a pivotal role in helminthic infection and allergic disorders. CD4+ T cells which produce type 2 cytokines can be generated via IL-4-dependent and -independent pathways. Although the IL-4-dependent pathway is well documented, factors that drive IL-4-independent Th2 cell differentiation remain obscure. We report here that the new cytokine IL-33, in the presence of Ag, polarizes murine and human naive CD4+ T cells into a population of T cells which produce mainly IL-5 but not IL-4. This polarization requires IL-1R-related molecule and MyD88 but not IL-4 or STAT6. The IL-33-induced T cell differentiation is also dependent on the phosphorylation of MAPKs and NF-κB but not the induction of GATA3 or T-bet. In vivo, ST2−/− mice developed attenuated airway inflammation and IL-5 production in a murine model of asthma. Conversely, IL-33 administration induced the IL-5-producing T cells and exacerbated allergen-induced airway inflammation in wild-type as well as IL-4−/− mice. Finally, adoptive transfer of IL-33-polarized IL-5+IL-4−T cells triggered airway inflammation in naive IL-4−/− mice. Thus, we demonstrate here that, in the presence of Ag, IL-33 induces IL-5-producing T cells and promotes airway inflammation independent of IL-4.
Activation of Invariant NKT Cells Ameliorates Experimental Ocular Autoimmunity by A Mechanism Involving Innate IFN-γ Production and Dampening of the Adaptive Th1 and Th17 Responses
Authors: Grajewski Rafael S. , Hansen Anna M. , Agarwal Rajeev K. , Kronenberg Mitchell , Sidobre Stephane , Su Shao Bo , Silver Phyllis B. , Tsuji Moriya , Franck Richard W. , Lawton Anne P. , Chan Chi-Chao , Caspi Rachel R.
Published: April 2014

Invariant NKT cells (iNKT cells) have been reported to play a role not only in innate immunity but also to regulate several models of autoimmunity. Furthermore, iNKT cells are necessary for the generation of the prototypic eye-related immune regulatory phenomenon, anterior chamber associated immune deviation (ACAID). In this study, we explore the role of iNKT cells in regulation of autoimmunity to retina, using a model of experimental autoimmune uveitis (EAU) in mice immunized with a uveitogenic regimen of the retinal Ag, interphotoreceptor retinoid-binding protein. Natural strain-specific variation in iNKT number or induced genetic deficiencies in iNKT did not alter baseline susceptibility to EAU. However, iNKT function seemed to correlate with susceptibility and its pharmacological enhancement in vivo by treatment with iNKT TCR ligands at the time of uveitogenic immunization reproducibly ameliorated disease scores. Use of different iNKT TCR ligands revealed dependence on the elicited cytokine profile. Surprisingly, superior protection against EAU was achieved with α-C-GalCer, which induces a strong IFN-γ but only a weak IL-4 production by iNKT cells, in contrast to the ligands α-GalCer (both IFN-γ and IL-4) and OCH (primarily IL-4). The protective effect of α-C-GalCer was associated with a reduction of adaptive Ag-specific IFN-γ and IL-17 production and was negated by systemic neutralization of IFN-γ. These data suggest that pharmacological activation of iNKT cells protects from EAU at least in part by a mechanism involving innate production of IFN-γ and a consequent dampening of the Th1 as well as the Th17 effector responses.
NFATc1 Regulates PD-1 Expression upon T Cell Activation
Authors: Oestreich Kenneth J. , Yoon Hyesuk , Ahmed Rafi , Boss Jeremy M.
Published: April 2014

PD-1 is a transmembrane protein involved in the regulation of immunological tolerance. Multiple studies have reported an association between high levels of PD-1 expressed on T cell surfaces and exhaustion in lymphocyte populations when challenged by chronic viral infections, such as HIV. By using model systems consisting of murine EL4 cells, which constitutively express PD-1, and primary murine CD8 T cells that express PD-1 upon T cell stimulation, we have identified two tissue-specific hypersensitive sites at the 5′ CR of the PD-1 locus. Gene reporter assays in CD8 T cells have shown that one of these sites has robust transcriptional activity in response to cell stimulation. Cell treatment with the calcineurin inhibitor cyclosporine A or a NFAT-specific inhibitor led to a sharp reduction in PD-1 expression in the constitutive and inducible systems. Furthermore, analysis of this region by chromatin immunoprecipitation assay revealed NFATc1 binding associated with gene activation in EL4 and primary CD8 T cells. Mutation of the NFATc1 binding site in PD-1 reporter constructs resulted in a complete loss of promoter activity. Together, these results demonstrate that PD-1 gene regulation occurs in part via the recruitment of NFATc1 to a novel regulatory element at the pdcd1 locus and provides the molecular mechanism responsible for the induction of PD-1 in response to T cell stimulation.
Distinct Regulation of Integrin-Dependent T Cell Conjugate Formation and NF-κB Activation by the Adapter Protein ADAP
Authors: Burbach Brandon J. , Srivastava Rupa , Medeiros Ricardo B. , O'Gorman William E. , Peterson Erik J. , Shimizu Yoji
Published: April 2014

Following TCR stimulation, T cells utilize the hematopoietic specific adhesion and degranulation-promoting adapter protein (ADAP) to control both integrin adhesive function and NF-κB transcription factor activation. We have investigated the molecular basis by which ADAP controls these events in primary murine ADAP−/− T cells. Naive DO11.10/ADAP−/− T cells show impaired adhesion to OVAp (OVA aa 323–339)-bearing APCs that is restored following reconstitution with wild-type ADAP. Mutational analysis demonstrates that the central proline-rich domain and the C-terminal domain of ADAP are required for rescue of T:APC conjugate formation. The ADAP proline-rich domain is sufficient to bind and stabilize the expression of SKAP55 (Src kinase-associated phosphoprotein of 55 kDa), which is otherwise absent from ADAP−/− T cells. Interestingly, forced expression of SKAP55 in the absence of ADAP is insufficient to drive T:APC conjugate formation, demonstrating that both ADAP and SKAP55 are required for optimal LFA-1 function. Additionally, the ADAP proline-rich domain is required for optimal Ag-induced activation of CD69, CD25, and Bcl-xL, but is not required for assembly of the CARMA1/Bcl10/Malt1 (caspase-recruitment domain (CARD) membrane-associated guanylate kinase (MAGUK) protein 1/B-cell CLL-lymphoma 10/mucosa-associated lymphoid tissue lymphoma translocation protein 1) signaling complex and subsequent TCR-dependent NF-κB activity. Our results indicate that ADAP is used downstream of TCR engagement to delineate two distinct molecular programs in which the ADAP/SKAP55 module is required for control of T:APC conjugate formation and functions independently of ADAP/CARMA1-mediated NF-κB activation.
Hepatitis C Virus Infection Sensitizes Human Hepatocytes to TRAIL-Induced Apoptosis in a Caspase 9-Dependent Manner
Authors: Lan Lin , Gorke Sebastian , Rau Sibylle J. , Zeisel Mirjam B. , Hildt Eberhard , Himmelsbach Kiyoshi , Carvajal-Yepes Monica , Huber Roman , Wakita Takaji , Schmitt-Graeff Annette , Royer Cathy , Blum Hubert E. , Fischer Richard , Baumert Thomas F.
Published: April 2014

Apoptosis of infected cells represents a key host defense mechanism against viral infections. The impact of apoptosis on the elimination of hepatitis C virus (HCV)-infected cells is poorly understood. The TRAIL has been implicated in the death of liver cells in hepatitis-infected but not in normal liver cells. To determine the impact of TRAIL on apoptosis of virus-infected host cells, we studied TRAIL-induced apoptosis in a tissue culture model system for HCV infection. We demonstrated that HCV infection sensitizes primary human hepatocytes and Huh7.5 hepatoma cells to TRAIL induced apoptosis in a dose- and time-dependent manner. Mapping studies identified the HCV nonstructural proteins as key mediators of sensitization to TRAIL. Using a panel of inhibitors targeting different apoptosis pathways, we demonstrate that sensitization to TRAIL is caspase-9 dependent and mediated in part via the mitochondrial pathway. Sensitization of hepatocytes to TRAIL-induced apoptosis by HCV infection represents a novel antiviral host defense mechanism that may have important implications for the pathogenesis of HCV infection and may contribute to the elimination of virus-infected hepatocytes.
Extracellular Gelsolin Binds Lipoteichoic Acid and Modulates Cellular Response to Proinflammatory Bacterial Wall Components
Authors: Bucki Robert , Byfield Fitzroy J. , Kulakowska Alina , McCormick Margaret E. , Drozdowski Wieslaw , Namiot Zbigniew , Hartung Thomas , Janmey Paul A.
Published: April 2014

The various functions of gelsolin in extracellular compartments are not yet clearly defined but include actin scavenging and antiinflammatory effects. Gelsolin was recently reported to bind endotoxin (LPS) from various Gram-negative bacteria with high affinity. In this study we investigate whether gelsolin also interacts with bacterial wall molecules of Gram-positive bacteria such as lipoteichoic acid (LTA) and whether gelsolin’s interaction with bacterial lipids from Gram-negative or Gram-positive bacteria affects their cellular inflammatory responses. A peptide based on the PPI binding site of gelsolin (160–169) binds purified LTA at the same molecular ratio that it binds phosphatidylinositol 4,5-bisphosphate. The OD of recombinant human plasma gelsolin was found to decrease following the addition of purified LTA, and the binding of gelsolin to LTA inhibits F-actin depolymerization by gelsolin. Simultaneously, the ability of LTA to activate translocation of NF-κB, E-selectin expression, and adhesion of neutrophils to LTA-treated human aortic endothelial cells was compromised by gelsolin. Gelsolin was able to partially inhibit LPS- or LTA-induced release of IL-8 from human neutrophils but was unable to prevent Gram-positive Bacillus subtilis or Gram-negative Pseudomonas aeruginosa growth and had no effect on the antibacterial activity of the cathelicidin-derived antibacterial peptide LL37. These data suggest that extracellular gelsolin is involved in the host immune recognition of LTA or LPS following release of these molecules from the bacterial outer membrane during cell division or attack by drugs and immune components.
Platelet-Activating Factor Production in the Spinal Cord of Experimental Allergic Encephalomyelitis Mice via the Group IVA Cytosolic Phospholipase A2-Lyso-PAFAT Axis
Authors: Kihara Yasuyuki , Yanagida Keisuke , Masago Kayo , Kita Yoshihiro , Hishikawa Daisuke , Shindou Hideo , Ishii Satoshi , Shimizu Takao
Published: April 2014

Platelet-activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) plays a critical role in inflammatory disorders including experimental allergic encephalomyelitis (EAE), an animal model for multiple sclerosis (MS). Although PAF accumulation in the spinal cord (SC) of EAE mice and cerebrospinal fluid of MS patients has been reported, little is known about the metabolic processing of PAF in these diseases. In this study, we demonstrate that the activities of phospholipase A2 (PLA2) and acetyl-CoA:lyso-PAF acetyltransferase (LysoPAFAT) are elevated in the SC of EAE mice on a C57BL/6 genetic background compared with those of naive mice and correlate with disease severity. Correspondingly, levels of groups IVA, IVB, and IVF cytosolic PLA2s, group V secretory PLA2, and LysoPAFAT transcripts are up-regulated in the SC of EAE mice. PAF acetylhydrolase activity is unchanged during the disease course. In addition, we show that LysoPAFAT mRNA and protein are predominantly expressed in microglia. Considering the substrate specificity and involvement of PAF production, group IVA cytosolic PLA2 is likely to be responsible for the increased PLA2 activity. These data suggest that PAF accumulation in the SC of EAE mice is profoundly dependent on the group IVA cytosolic PLA2/LysoPAFAT axis present in the infiltrating macrophages and activated microglia.
IFN Consensus Sequence Binding Protein (Icsbp) Is Critical for Eosinophil Development
Authors: Milanovic Maja , Terszowski Grzegorz , Struck Daniela , Liesenfeld Oliver , Carstanjen Dirk
Published: April 2014

IFN consensus sequence binding protein (Icsbp) (IFN response factor-8) is a hematopoietic transcription factor with dual functions in myelopoiesis and immunity. In this study, we report a novel role of Icsbp in regulating the development of eosinophils. Loss of Icsbp in mice leads to a reduction of eosinophils in different tissues. During parasite infection with the nematode Nippostrongylus brasiliensis, Icsbp-deficient mice fail to mount eosinophilia despite a vigorous IL-5 response. Numbers of phenotypically defined eosinophil progenitors are decreased and those progenitors have, on a per-cell basis, reduced eosinophil differentiation potential. The transcription factor Gata1, crucial for eosinophil development, is reduced expressed in committed eosinophil progenitors in wells as mature eosinophils. These findings identify Icsbp as a novel transcription factor critical for the development of the eosinophil lineage.
Immune Cell Activation by Enterotoxin Gene Cluster (egc)-Encoded and Non-egc Superantigens from Staphylococcus aureus
Authors: Grumann Dorothee , Scharf Sandra S. , Holtfreter Silva , Kohler Christian , Steil Leif , Engelmann Susanne , Hecker Michael , Völker Uwe , Bröker Barbara M.
Published: April 2014

The species Staphylococcus aureus harbors 19 superantigen gene loci, six of which are located in the enterotoxin gene cluster (egc). Although these egc superantigens are far more prevalent in clinical S. aureus isolates than non-egc superantigens, they are not a prominent cause of toxic shock. Moreover, neutralizing Abs against egc superantigens are very rare, even among carriers of egc-positive S. aureus strains. In search of an explanation, we have tested two non-exclusive hypotheses: 1) egc and non-egc superantigens have unique intrinsic properties and drive the immune system into different directions and 2) egc and non-egc superantigens are released by S. aureus under different conditions, which shape the immune response. A comparison of three egc (SEI, SElM, and SElO) and three non-egc superantigens (SEB, SElQ, and toxic shock syndrome toxin-1) revealed that both induced proliferation of human PBMC with comparable potency and elicited similar Th1/Th2-cytokine signatures. This was supported by gene expression analysis of PBMC stimulated with one representative superantigen from each group (SEI and SEB). They induced very similar transcriptional changes, especially of inflammation-associated gene networks, corresponding to a very strong Th1- and Th17-dominated immune response. In contrast, the regulation of superantigen release differed markedly between both superantigen groups. Egc-encoded proteins were secreted by S. aureus during exponential growth, while non-egc superantigens were released in the stationary phase. We conclude that the distinct biological behavior of egc and non-egc superantigens is not due to their intrinsic properties, which are very similar, but caused by their differential release by S. aureus.
Lipoteichoic Acid Induces HO-1 Expression via the TLR2/MyD88/c-Src/NADPH Oxidase Pathway and Nrf2 in Human Tracheal Smooth Muscle Cells
Authors: Lee I-Ta , Wang Shyi-Wu , Lee Chiang-Wen , Chang Chia-Chi , Lin Chih-Chung , Luo Shue-Fen , Yang Chuen-Mao
Published: April 2014

Heme oxygenase (HO)-1 is a stress-inducible rate-limiting enzyme in heme degradation that confers cytoprotection against oxidative injury and provides a vital function in maintaining tissue homeostasis. Increasing reports have indicated that lipoteichoic acid (LTA) exerts as LPS as an immune system-stimulating agent and plays a role in the pathogenesis of severe inflammatory responses induced by Gram-positive bacterial infection. We report that LTA is an inducer of HO-1 expression mediated through the signaling pathways in human tracheal smooth muscle cells (HTSMCs). LTA-induced HO-1 protein levels, mRNA expression, and promoter activity were attenuated by transfection with dominant negative mutants of TLR2 and MyD88, by pretreatment with the inhibitors of c-Src (PP1), NADPH oxidase (diphenylene iodonium chloride (DPI) and apocynin (APO)), and reactive oxygen species (ROS) scavenger (N-acetyl-l-cysteine) or by transfection with small interfering RNAs of Src and NF-E2-related factor 2 (Nrf2). LTA-stimulated translocation of p47phox and Nrf2 or ROS production was attenuated by transfection with dominant negative mutants of TLR2, MyD88, and c-Src and by pretreatment with DPI or APO. Furthermore, LTA-induced TLR2, MyD88, TNFR-associated factor (TRAF)6, c-Src, and p47phox complex formation was revealed by immunoprecipitation using an anti-TLR2 or anti-c-Src Ab followed by Western blot analysis against an anti-TLR2, anti-MyD88, anti-TRAF6, anti-c-Src, or anti-p47phox Ab. These results demonstrated that LTA-induced ROS generation was mediated through the TLR2/MyD88/TRAF6/c-Src/NADPH oxidase pathway, in turn initiates the activation of Nrf2, and ultimately induces HO-1 expression in HTSMCs.
Differential Production of IL-23 and IL-12 by Myeloid-Derived Dendritic Cells in Response to TLR Agonists
Authors: Roses Robert E. , Xu Shuwen , Xu Min , Koldovsky Ursula , Koski Gary , Czerniecki Brian J.
Published: April 2014

The recently delineated role for IL-23 in enhancing Th-17 activity suggests that regulation of its expression is distinct from that of IL-12. We hypothesized that independent TLR-mediated pathways are involved in the regulation of IL-12 and IL-23 production by myeloid-derived dendritic cells (DCs). The TLR 2 ligand, lipoteichoic acid (LTA), the TLR 4 ligand, LPS, and the TLR 7/8 ligand, resimiquod (R848), induced production of IL-23 by DCs. None of these TLR ligands alone induced significant IL-12 production, except when combined with IFN-γ or other TLR ligands. Notably, IL-23 production in response to single TLR ligands was inhibited by IL-4. DCs treated with single TLR agonists induced IL-17A production by allogeneic and Ag-specific memory CD4+ T cells, an effect that was abrogated by IL-23 neutralization. Moreover, these DCs stimulated IL-17A production by tumor peptide-specific CD8+ T cells. In contrast, DCs treated with dual signals induced naive and memory Th1 responses and enhanced the functional avidity of tumor-specific CD8+ T cells. These results indicate that distinct microbial-derived stimuli are required to drive myeloid DC commitment to IL-12 or IL-23 production, thereby differentially polarizing T cell responses.
Despite Biased TRBV Gene Usage against a Dominant HLA B57-Restricted Epitope, TCR Diversity Can Provide Recognition of Circulating Epitope Variants
Authors: Simons Brenna C. , VanCompernolle Scott E. , Smith Rita M. , Wei Jie , Barnett Louise , Lorey Shelly L. , Meyer-Olson Dirk , Kalams Spyros A.
Published: April 2014

The role of epitope-specific TCR repertoire diversity in the control of HIV-1 viremia is unknown. Further analysis at the clonotype level is important for understanding the structural aspects of the HIV-1 specific repertoire that directly relate to CTL function and ability to suppress viral replication. In this study, we performed in-depth analysis of T cell clonotypes directed against a dominantly recognized HLA B57-restricted epitope (KAFSPEVIPMF; KF11) and identified common usage of the TCR β-chain TRBV7 in eight of nine HLA B57 subjects examined, regardless of HLA B57 subtype. Despite this convergent TCR gene usage, structural and functional assays demonstrated no substantial difference in functional or structural avidity between TRBV7 and non-TRBV7 clonotypes and this epitopic peptide. In a subject where TRBV7-usage did not confer cross-reactivity against the dominant autologous sequence variant, another circulating TCR clonotype was able to preferentially recognize the variant peptide. These data demonstrate that despite selective recruitment of TCR for a conserved epitope over the course of chronic HIV-1 infection, TCR repertoire diversity may benefit the host through the ability to recognize circulating epitope variants.
Human C3 Deficiency Associated with Impairments in Dendritic Cell Differentiation, Memory B Cells, and Regulatory T Cells
Authors: Ghannam Arije , Pernollet Martine , Fauquert Jean-Luc , Monnier Nicole , Ponard Denise , Villiers Marie-Bernadette , Péguet-Navarro Josette , Tridon Arlette , Lunardi Joel , Gerlier Denis , Drouet Christian
Published: April 2014

Primary C3 deficiency, a rare autosomal inherited disease (OMIM 120700), was identified in a 2-year-old male suffering from recurrent pyogenic infections from early infancy with undetectable total complement hemolytic activity (CH50) and C3 values. The nonconsanguineous parents and the two patients’ two siblings had 50% normal serum C3 concentration. The molecular abnormality associated a paternal allele coding C3 with the missense mutation p.Ser550Pro and an apparently null maternal allele, with production of a defective protein that could no longer be secreted. Vaccination of the child did not induce a long-term Ab response. Accordingly, switched memory IgD−CD27+ B cells were barely detected, amounting to only 2.3% of peripheral blood CD19+ cells. Cells were significantly defective in stimulating alloreactive responses. The in vitro development of immature dendritic cells and their maturation capacity were greatly impaired, with decreased CD1a expression and IL-12p70 secretion ability. These cells were unable to induce autologous B cell proliferation and Ig secretion in the presence of CD40L and C3. Finally, the regulatory T cell development ability of CD4+ T cells after CD3 and CD46 activation in the presence of IL-2 was significantly impaired. Thus, the association of important functional defects of dendritic cells, acquisition of B cell memory, and regulatory T cells with human C3 deficiency strongly supports a major role for C3 in bridging innate and adaptive immunity in humans.
Homeostatic Regulation of Blood Neutrophil Counts
Authors: von Vietinghoff Sibylle , Ley Klaus
Published: April 2014

Blood neutrophil counts are determined by the differentiation and proliferation of precursor cells, the release of mature neutrophils from the bone marrow, margination, trafficking and transmigration through the endothelial lining, neutrophil apoptosis, and uptake by phagocytes. This brief review summarizes the regulation of blood neutrophil counts, which is in part controlled by G-CSF, IL-17, and IL-23. Neutrophils are retained in the bone marrow through interaction of CXCL12 with its receptor CXCR4. The relevance of this mechanism is illustrated by rare diseases in which disrupting the desensitization of CXCR4 results in failure to release mature neutrophils from bone marrow. Although blood neutrophil numbers in inbred mouse strains and individual human subjects are tightly controlled, their large variation among outbred populations suggests genetic factors. One example is benign ethnic neutropenia, which is found in some African Americans. Reduced and elevated neutrophil counts, even within the normal range, are associated with excess all-cause mortality.
Cutting Edge: Inhibition of NF-κB-Mediated TSLP Expression by Retinoid X Receptor
Authors: Lee Hai-Chon , Headley Mark B. , Iseki Masanori , Ikuta Koichi , Ziegler Steven F.
Published: April 2014

The epithelial-derived cytokine thymic stromal lymphopoietin (TSLP) has important roles in the initiation of allergic airway inflammation and the activation of dendritic cells. We have shown that the human TSLP gene is regulated in a NF-κB-dependent manner; however the factors that negatively regulate TSLP expression are not known. In this study we demonstrate that 9-cis-retinoic acid (9-cis-RA) is a negative regulator of TSLP expression in airway epithelial cells. This inhibition is manifested as a block in the IL-1β-mediated recruitment of NF-κB to the human TSLP promoter. 9-cis-RA-mediated inhibition is not restricted to TSLP gene expression but rather reflects a general inhibition of NF-κB activation, as other NF-κB-regulated-genes were also inhibited in a similar manner by 9-cis-RA treatment. Taken as a whole, these data demonstrate that inhibition of IL-1β-dependent genes by active retinoid X receptors involves antagonism of NF-κB signaling.
Cutting Edge: Autocrine TGF-β Sustains Default Tolerogenesis by IDO-Competent Dendritic Cells
Authors: Belladonna Maria L. , Volpi Claudia , Bianchi Roberta , Vacca Carmine , Orabona Ciriana , Pallotta Maria T. , Boon Louis , Gizzi Stefania , Fioretti Maria C. , Grohmann Ursula , Puccetti Paolo
Published: April 2014

CD8− and CD8+ dendritic cells (DCs) are distinct subsets of mouse splenic accessory cells with opposite but flexible programs of Ag presentation, leading to immunogenic and tolerogenic responses, respectively. In this study, we show that the default tolerogenic function of CD8+ DCs relies on autocrine TGF-β, which sustains the activation of IDO in response to environmental stimuli. CD8− DCs do not produce TGF-β, yet externally added TGF-β induces IDO and turns those cells from immunogenic into tolerogenic cells. The acquisition of a suppressive phenotype by CD8− DCs correlates with activation of the PI3K/Akt and noncanonical NF-κB pathways. These data are the first to link TGF-β signaling with IDO in controlling spontaneous tolerogenesis by DCs.
Cutting Edge: Immunity against a “Silent” Salivary Antigen of the Lyme Vector Ixodes scapularis Impairs Its Ability to Feed
Authors: Kotsyfakis Michalis , Anderson Jennifer M. , Andersen John F. , Calvo Eric , Francischetti Ivo M. B. , Mather Thomas N. , Valenzuela Jesus G. , Ribeiro José M. C.
Published: April 2014

Ixodes scapularis ticks transmit the Lyme disease agent in the United States. Although strong antitick immunity mediates tick rejection by certain vertebrates, only a few Ags have been molecularly characterized. We show that guinea pig vaccination against a secreted tick salivary immunomodulator, sialostatin L2, can lead to decreased feeding ability of I. scapularis nymphs. Increased rejection rate, prolonged feeding time, and apparent signs of inflammation were observed for nymphs attached to vaccinated animals, indicating a protective host immune response. Interestingly, sialostatin L2 humoral recognition does not take place upon repeated tick exposure in control animals, but only in the vaccinated animals that neutralize sialostatin L2 action. Therefore, we demonstrate an essential sialostatin L2 role upon nymphal infestation that can be blocked by vertebrate immunity and propose the discovery of similarly “silent” Ags toward the development of a multicomponent vaccine that will protect against tick bites and the pathogens they transmit.
Cutting Edge: Contact with Secondary Lymphoid Organs Drives Postthymic T Cell Maturation
Authors: Houston Evan G. , Nechanitzky Robert , Fink Pamela J.
Published: April 2014

T cell development, originally thought to be completed in the thymus, has recently been shown to continue for several weeks in the lymphoid periphery. The forces that drive this peripheral maturation are unclear. The use of mice transgenic for GFP driven by the RAG2 promoter has enabled the ready identification and analysis of recent thymic emigrants. Here, we show that recent thymic emigrant maturation is a progressive process and is promoted by T cell exit from the thymus. Further, we show that this maturation occurs within secondary lymphoid organs and does not require extensive lymphocyte recirculation.
Activation of Human Plasmacytoid Dendritic Cells by TLR9 Impairs FcγRII-Mediated Uptake of Immune Complexes and Presentation by MHC Class II
Authors: Benitez-Ribas Daniel , Tacken Paul , Punt Cornelis J. A. , de Vries I. Jolanda M. , Figdor Carl G.
Published: April 2014

Human plasmacytoid dendritic cells (pDCs)2 exploit Ag uptake receptors like CD32a for internalization of exogenous Ags. Activation of pDC by TLR9 ligand CpG-C induces strong maturation. Surprisingly, we observed that CpG-C-stimulated pDCs showed impaired Ag-specific T cell proliferation whereas the induction of allogeneic T cell proliferation was not affected. We demonstrated that signals from TLR9 caused a rapid down-regulation of the capacity of pDC to take-up Ab-Ag complexes without altering their CD32a expression, thus explaining the reduced Ag presentation. The recent contrasting biological responses that were observed upon TLR9 ligation in pDCs prompted us to study the effect of several TLR9 ligands. We observed that type I IFN-inducer CpG-A, localizing in the early endosomal compartment, did not affect CD32a function, whereas CpGs localizing in the late endosomes and inducing pDC maturation clearly inhibited CD32a-mediated Ag uptake and presentation. We conclude that TLR9 ligands not only determine the type of response, i.e., type I IFN production (innate immunity) or maturation (adaptive immunity), but also directly affect Ag presentation capacity of pDCs. We hypothesize that pDC, once activated via TLR9-ligands reaching the late endosomes, can only present initially sampled Ags and thus are protected from uptake and processing of additional potential self-Ags.