bluuebunny/crossref_metadata_2025_split huggingface dataset:
No Significant CTL Cross-Priming by Dendritic Cell-Derived Exosomes during Murine Lymphocytic Choriomeningitis Virus Infection
Authors: Coppieters Ken , Barral Ana María , Juedes Amy , Wolfe Tom , Rodrigo Evelyn , Théry Clotilde , Amigorena Sebastian , von Herrath Matthias G. 
Published: February 2009

Abstract
Exosomes are small membrane vesicles of endocytic origin that are secreted by most cells in culture, but are also present in serum. They contain a wide array of protein ligands on their surface, which has led to the hypothesis that they might mediate intercellular communication. Indeed, data support that exosomes can transfer Ags to dendritic cells (DC), and, interestingly, that these DC can subsequently induce T cell priming or tolerance. We have investigated whether this concept can be expanded to antiviral immunity. We isolated exosomes from supernatant of cultured bone marrow-derived DC (BMDC) that were infected with lymphocytic choriomeningitis virus (LCMV) or loaded with an immunodominant LCMV peptide, and characterized them by flow cytometry upon binding to beads. We then incubated the exosome preparations with BMDC and looked at their potential to activate LCMV gp33-specific naive and memory CD8 T cells. We found that exosomes do not significantly contribute to CD8 T cell cross-priming in vitro. Additionally, exosomes derived from in vitro-infected BMDC did not exhibit significant in vivo priming activity, as evidenced by the lack of protection following exosome vaccination. Thus, DC-derived exosomes do not appear to contribute significantly to CTL priming during acute LCMV infection.
Human CD4+ Memory T Cells Are Preferential Targets for Bystander Activation and Apoptosis
Authors: Bangs Sarah C. , Baban Dilair , Cattan Helen J. , Li Chris Ka-Fi , McMichael Andrew J. , Xu Xiao-Ning 
Published: February 2009

Abstract
There is much evidence that T cells may be activated via mechanisms that act independently of direct TCR ligation. Despite this, the question of whether such forms of bystander T cell activation occur during immune responses is hotly debated. To address some outstanding questions, we set up an in vitro system within which to analyze bystander T cell activation in human T cells, in the absence of the possibility for TCR cross-reactivity. In addition, we have investigated the genetic, phenotypic, and functional characteristics of bystander-activated T cells. In this study, we show that bystander T cell activation is, indeed, observed during a specific immune response, and that it occurs preferentially among CD4+ memory T cells. Furthermore, bystander-activated T cells display a distinct gene expression profile. The mechanism for bystander T cell activation involves soluble factors, and the outcome is an elevated level of apoptosis. This may provide an explanation for the attrition of T cell memory pools of heterologous specificity during immune responses to pathogens such as viruses.
Intact Bacteria Inhibit the Induction of Humoral Immune Responses to Bacterial-Derived and Heterologous Soluble T Cell-Dependent Antigens
Authors: Chattopadhyay Gouri , Chen Quanyi , Colino Jesus , Lees Andrew , Snapper Clifford M. 
Published: February 2009

Abstract
During infections with extracellular bacteria, such as Streptococcus pneumoniae (Pn), the immune system likely encounters bacterial components in soluble form, as well as those associated with the intact bacterium. The potential cross-regulatory effects on humoral immunity in response to these two forms of Ag are unknown. We thus investigated the immunologic consequences of coimmunization with intact Pn and soluble conjugates of Pn-derived proteins and polysaccharides (PS) as a model. Coimmunization of mice with Pn and conjugate resulted in marked inhibition of conjugate-induced PS-specific memory, as well as primary and memory anti-protein Ig responses. Inhibition occurred with unencapsulated Pn, encapsulated Pn expressing different capsular types of PS than that present in the conjugate, and with conjugate containing protein not expressed by Pn, but not with 1-μm latex beads in adjuvant. Inhibition was long-lasting and occurred only during the early phase of the immune response, but it was not associated with tolerance. Pn inhibited the trafficking of conjugate from the splenic marginal zone to the B cell follicle and T cell area, strongly suggesting a potential mechanism for inhibition. These data suggest that during infection, bacterial-associated Ags are the preferential immunogen for antibacterial Ig responses.
IL-10-Dependent S100A8 Gene Induction in Monocytes/Macrophages by Double-Stranded RNA
Authors: Endoh Yasumi , Chung Yuen Ming , Clark Ian A. , Geczy Carolyn L. , Hsu Kenneth 
Published: February 2009

Abstract
The S100 calcium-binding proteins S100A8 and S100A9 are elevated systemically in patients with viral infections. The S100A8-S100A9 complex facilitated viral replication in human CD4+ T lymphocytes latently infected with HIV-1- and S100A8-induced HIV-1 transcriptional activity. Mechanisms inducing the S100 genes and the potential source of these proteins following viral activation are unknown. In this study, we show that S100A8 was induced in murine macrophages, and S100A8 and S100A9 in human monocytes and macrophages, by polyinosinic:polycytidylic acid, a dsRNA mimetic. Induction was at the transcriptional level and was IL-10 dependent. Similar to LPS-induced S100A8, induction by dsRNA was dependent on p38 and ERK MAPK. Protein kinase R (PKR) mediates antiviral defense and participates in MyD88-dependent/independent signaling triggered by TLR4 or TLR3. Like IL-10, S100 induction by polyinosinic:polycytidylic acid and by LPS was inhibited by the specific PKR inhibitor 2-aminopurine, indicating a novel IL-10, PKR-dependent pathway. Other mediators such as IFN-β, which synergized with dsRNA, may also be involved. C/EBPβ bound the defined promoter region in response to dsRNA. S100A8 was expressed in lungs of mice infected with influenza virus and was maximal at day 8 with strong immunoreactivity in epithelial cells lining the airways and in mononuclear cells and declined early in the recovery phase, implying down-regulation by mediator(s) up-regulated during resolution of the infection. IL-10 is implicated in viral persistence. Since S100A8/S100A9 levels are likely to be maintained in conditions where IL-10 is raised, these proteins may contribute to viral persistence in patients infected by some RNA viruses.
Down-Regulation of MHC Class II Expression through Inhibition of CIITA Transcription by Lytic Transactivator Zta during Epstein-Barr Virus Reactivation
Authors: Li Dan , Qian Lu , Chen Changguo , Shi Ming , Yu Ming , Hu Meiru , Song Lun , Shen Beifen , Guo Ning 
Published: February 2009

Abstract
The presentation of peptides to T cells by MHC class II molecules is of critical importance in specific recognition to a pathogen by the immune system. The level of MHC class II directly influences T lymphocyte activation. The aim of this study was to identify the possible mechanisms of the down-regulation of MHC class II expression by Zta during EBV lytic cycle. The data in the present study demonstrated that ectopic expression of Zta can strongly inhibit the constitutive expression of MHC class II and CIITA in Raji cells. The negative effect of Zta on the CIITA promoter activity was also observed. Scrutiny of the DNA sequence of CIITA promoter III revealed the presence of two Zta-response element (ZRE) motifs that have complete homology to ZREs in the DR and left-hand side duplicated sequence promoters of EBV. By chromatin immunoprecipitation assays, the binding of Zta to the ZRE221 in the CIITA promoter was verified. Site-directed mutagenesis of three conserved nucleotides of the ZRE221 substantially disrupted Zta-mediated inhibition of the CIITA promoter activity. Oligonucleotide pull-down assay showed that mutation of the ZRE221 dramatically abolished Zta binding. Analysis of the Zta mutant lacking DNA binding domain revealed that the DNA-binding activity of Zta is required for the trans repression of CIITA. The expression of HLA-DRα and CIITA was restored by Zta gene silencing. The data indicate that Zta may act as an inhibitor of the MHC class II pathway, suppressing CIITA transcription and thus interfering with the expression of MHC class II molecules.
Single Nucleotide Changes in the Human Iγ1 and Ιγ4 Promoters Underlie Different Transcriptional Responses to CD40
Authors: Sinquett Frank L. , Dryer Rebecca L. , Marcelli Valentina , Batheja Ameesha , Covey Lori R. 
Published: February 2009

Abstract
Analysis of subclass-specific germline transcription in activated peripheral B cells revealed a highly biased expression pattern of the four Iγ transcripts to signals through CD40 and IL-4. This difference was most pronounced when comparing the profile of Iγ1 and Iγ4 transcripts and was not expected given the very high degree of sequence conservation between promoters. In this report, the influence of sequence differences on the regulation of the Iγ1 and Iγ4 promoters has been investigated given the highly muted transcriptional activity of the Iγ4 promoter. Two regions were analyzed where single nucleotide differences corresponded to major changes in transcriptional activity. These regions were the previously defined CD40 response region containing three putative NF-κB-binding sites and the downstream 36-bp region containing CREB/activating transcription factor and κB6 sites. Mutation of a single nucleotide at position 6 within the Iγ4 κB6 site increased promoter activity to ∼50% of the activity of the Iγ1 promoter. Furthermore, elevated promoter strength corresponded with increased binding of p50, p65, c-Rel, RelB, and p300 proteins to a level comparable with that of Iγ1. Minor nucleotide changes to both the Iγ4 CD40 response region and the 36-bp element resulted in a response undistinguishable from an Iγ1 response, suggesting cooperation between the two regulatory regions for optimal transcriptional activity. Collectively, these mutational analyses suggest that minor sequence differences contribute to the composition and affinity of transcriptional protein complexes regulating subclass-specific germline transcription, which in part impacts the overall level of class switch recombination to targeted CH regions.
The Expression of Heparin-Binding Epidermal Growth Factor-Like Growth Factor by Regulatory Macrophages
Authors: Edwards Justin P. , Zhang Xia , Mosser David M. 
Published: February 2009

Abstract
We previously described a population of regulatory macrophages that produced high levels of IL-10 and low levels of IL-12/23. We now describe and characterize the expression of heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) by these macrophages. HB-EGF has previously been associated with a number of physiological and pathological conditions, including tumor growth and angiogenesis. The induction of HB-EGF in regulatory macrophages is due to new transcription and not to increased mRNA stability. The transcription factor Sp1 is a major factor in HB-EGF production, and knockdown of Sp1 substantially diminishes HB-EGF production. Sp1 was recruited to three sites within the first 2 kb of the HB-EGF promoter following stimulation, and the site located at −83/−54 was required for HB-EGF promoter activity. These regions of the promoter become more accessible to endonuclease activity following macrophage activation, and this accessibility was contingent on activation of the MAPK, ERK. We show that several experimental manipulations that give rise to regulatory macrophages also result in HB-EGF production. These observations indicate that in addition to the secretion of the anti-inflammatory cytokine IL-10, another novel characteristic of regulatory macrophages is the production of angiogenic HB-EGF.
The Sequestosome 1/p62 Attenuates Cytokine Gene Expression in Activated Macrophages by Inhibiting IFN Regulatory Factor 8 and TNF Receptor-Associated Factor 6/NF-κB Activity
Authors: Kim Ji Young , Ozato Keiko 
Published: February 2009

Abstract
Sequestosome 1/p62 (p62) is a scaffold/adaptor protein with multiple functions implicated for neuronal and bone diseases. It carries a ubiquitin binding domain through which it mediates proteasome-dependent proteolysis. In addition, p62 is reported to regulate NF-κB activity in some cells. To date, however, the role of p62 in innate immunity has not been fully elucidated. In this study, we report that IFN-γ plus TLR signaling stimulates late expression of p62 in murine macrophages. Overexpression of p62 inhibited expression of multiple cytokines, IL-12p40, TNF-α, IL-1β, IL-6, and IFN-β, whereas p62 underexpression by small hairpin RNA markedly elevated their expression, indicating that p62 is a broad negative regulator of cytokine expression in stimulated macrophages. We show that p62 interacts with IFN regulatory factor 8 and Ro52, the transcription factor and ubiquitin E3 ligase that are important for IL-12p40 expression. This interaction, detectable at a late stage in stimulated macrophages, led to increased polyubiquitination and destabilization of IFN regulatory factor 8. We also show that upon macrophage stimulation, p62 binds to TNFR-associated factor 6, another E3 ligase important for NF-κB activation, but later this interaction was replaced by the recruitment of the deubiquitinating enzyme, cylindromatosis, an inhibitor of NF-κB activity. Recruitment of cylindromatosis coincided with reduced TNFR-associated factor 6 autoubiquitination and lower NF-κB activation. Our results indicate that p62 orchestrates orderly regulation of ubiquitin modification processes in macrophages to ensure attenuation of cytokine transcription postactivation. Together, p62 may provide a mechanism by which to control excessive inflammatory responses after macrophage activation.
Intestinal Tolerance Is Converted to Autoimmune Enteritis upon PD-1 Ligand Blockade
Authors: Reynoso Erika D. , Elpek Kutlu G. , Francisco Loise , Bronson Roderick , Bellemare-Pelletier Angélique , Sharpe Arlene H. , Freeman Gordon J. , Turley Shannon J. 
Published: February 2009

Abstract
The B7 family member programmed death-1 ligand (PD-L1) has been shown to play an inhibitory role in the regulation of T cell responses in several organs. However, the role of PD-L1 in regulating tolerance to self-Ags of the small intestine has not been previously addressed. In this study, we investigated the role of PD-L1 in CD8+ T cell tolerance to an intestinal epithelium-specific Ag using the iFABP-tOVA transgenic mouse model, in which OVA is expressed as a self-Ag throughout the small intestine. Using adoptive transfer of naive OVA-specific CD8+ T cells, we show that loss of PD-1:PD-L1 signaling, by either Ab-mediated PD-L1 blockade or transfer of PD-1−/− T cells, leads to considerable expansion of OVA-specific CD8+ T cells and their differentiation into effector cells capable of producing proinflammatory cytokines. A fatal CD8+ T cell-mediated inflammatory response develops rapidly against the small bowel causing destruction of the epithelial barrier, severe blunting of intestinal villi, and recruitment and activation of myeloid cells. This response is highly specific because immune destruction selectively targets the small intestine but not other organs. Collectively, these results indicate that loss of the PD-1:PD-L1 inhibitory pathway breaks CD8+ T cell tolerance to intestinal self-Ag, thus leading to severe enteric autoimmunity.
Regulation of Mature ADAM17 by Redox Agents for L-Selectin Shedding
Authors: Wang Yue , Herrera Amy H. , Li Ying , Belani Kiran K. , Walcheck Bruce 
Published: February 2009

Abstract
L-selectin is constitutively expressed by neutrophils and plays a key role in directing these cells to sites of inflammation. Upon neutrophil activation, L-selectin is rapidly and efficiently down-regulated from the cell surface by ectodomain shedding. We have directly shown that A disintegrin and metalloprotease 17 (ADAM17) is a primary and nonredundant sheddase of L-selection by activated neutrophils in vivo. Following cell activation, intracellular signals lead to the induction of ADAM17’s enzymatic activity; however, the target of this inducer mechanism remains unclear. Our study provides evidence of an activation mechanism that involves the extracellular region of the mature form of cell surface ADAM17 and not its intracellular region. We demonstrate that the catalytic activity of purified ADAM17 lacking a prodomain and its intracellular region is diminished under mild reducing conditions by DTT and enhanced by H2O2 oxidation. Moreover, H2O2 reversed ADAM17 inhibition by DTT. The treatment of neutrophils with H2O2 also induced L-selectin shedding in an ADAM17-dependent manner. These findings suggest that thiol-disulfide conversion occurring in the extracellular region of ADAM17 may be involved in its activation. An analysis of ADAM17 revealed that within its disintegrin/cysteine-rich region are two highly conserved, vicinal cysteine sulfhydryl motifs (cysteine-X-X-cysteine), which are well-characterized targets for thiol-disulfide exchange in various other proteins. Using a cell-based ADAM17 reconstitution assay, we demonstrate that the cysteine-X-X-cysteine motifs are critical for L-selectin cleavage. Taken together, our findings suggest that reduction-oxidation modifications of cysteinyl sulfhydryl groups in mature ADAM17 may serve as a mechanism for regulating the shedding of L-selectin following neutrophil stimulation.
Asthma-Related Environmental Fungus, Alternaria, Activates Dendritic Cells and Produces Potent Th2 Adjuvant Activity
Authors: Kobayashi Takao , Iijima Koji , Radhakrishnan Suresh , Mehta Vinay , Vassallo Robert , Lawrence Christopher B. , Cyong Jong-Chol , Pease Larry R. , Oguchi Katsuji , Kita Hirohito 
Published: February 2009

Abstract
Asthma is thought to result from dysregulated Th2-like airway inflammatory responses to the environment. Although the etiology of asthma is not fully understood in humans, clinical and epidemiological evidence suggest a potential link between exposure to environmental fungi, such as Alternaria, and development and/or exacerbation of asthma. The goal of this project was to investigate the mechanisms of airway Th2 responses by using Alternaria as a clinically relevant model for environmental exposure. Airway exposure of naive animals to an experimental Ag, OVA, or a common allergen, short ragweed pollen, induced no or minimal immune responses to these Ags. In contrast, mice developed strong Th2-like immune responses when they were exposed to these Ags in the presence of Alternaria extract. Extracts of other fungi, such as Aspergillus and Candida, showed similar Th2 adjuvant effects, albeit not as potently. Alternaria stimulated bone marrow-derived dendritic cells (DCs) to express MHC class II and costimulatory molecules, including OX40 ligand, in vitro. Importantly, Alternaria inhibited IL-12 production by activated DCs, and DCs exposed to Alternaria enhanced Th2 polarization of CD4+ T cells. Furthermore, adoptive airway transfer of DCs, which had been pulsed with OVA in the presence of Alternaria, showed that the recipient mice had enhanced IgE Ab production and Th2-like airway responses to OVA. Thus, the asthma-related environmental fungus Alternaria produces potent Th2-like adjuvant effects in the airways. Such immunogenic properties of certain environmental fungi may explain their strong relationships with human asthma and allergic diseases.
Immune Reconstitution during Pneumocystis Lung Infection: Disruption of Surfactant Component Expression and Function by S-Nitrosylation
Authors: Atochina-Vasserman Elena N. , Gow Andrew J. , Abramova Helen , Guo Chang-Jiang , Tomer Yaniv , Preston Angela M. , Beck James M. , Beers Michael F. 
Published: February 2009

Abstract
Pneumocystis pneumonia (PCP), the most common opportunistic pulmonary infection associated with HIV infection, is marked by impaired gas exchange and significant hypoxemia. Immune reconstitution disease (IRD) represents a syndrome of paradoxical respiratory failure in patients with active or recently treated PCP subjected to immune reconstitution. To model IRD, C57BL/6 mice were selectively depleted of CD4+ T cells using mAb GK1.5. Following inoculation with Pneumocystis murina cysts, infection was allowed to progress for 2 wk, GK1.5 was withdrawn, and mice were followed for another 2 or 4 wk. Flow cytometry of spleen cells demonstrated recovery of CD4+ cells to &gt;65% of nondepleted controls. Lung tissue and bronchoalveolar lavage fluid harvested from IRD mice were analyzed in tandem with samples from CD4-depleted mice that manifested progressive PCP for 6 wks. Despite significantly decreased pathogen burdens, IRD mice had persistent parenchymal lung inflammation, increased bronchoalveolar lavage fluid cellularity, markedly impaired surfactant biophysical function, and decreased amounts of surfactant phospholipid and surfactant protein (SP)-B. Paradoxically, IRD mice also had substantial increases in the lung collectin SP-D, including significant amounts of an S-nitrosylated form. By native PAGE, formation of S-nitrosylated SP-D in vivo resulted in disruption of SP-D multimers. Bronchoalveolar lavage fluid from IRD mice selectively enhanced macrophage chemotaxis in vitro, an effect that was blocked by ascorbate treatment. We conclude that while PCP impairs pulmonary function and produces abnormalities in surfactant components and biophysics, these responses are exacerbated by IRD. This worsening of pulmonary inflammation, in response to persistent Pneumocystis Ags, is mediated by recruitment of effector cells modulated by S-nitrosylated SP-D.
IFN-β Impairs Superoxide-Dependent Parasite Killing in Human Macrophages: Evidence for a Deleterious Role of SOD1 in Cutaneous Leishmaniasis
Authors: Khouri Ricardo , Bafica André , Silva Maria da Purificação Pereira , Noronha Almerio , Kolb Jean-Pierre , Wietzerbin Juana , Barral Aldina , Barral-Netto Manoel , Van Weyenbergh Johan 
Published: February 2009

Abstract
Type I IFNs (IFN-α/β) have only recently gained considerable attention as immunomodulators in nonviral infectious diseases. IFN-β has been shown to protect, in a NO-dependent manner, against murine Old World leishmaniasis caused by Leishmania major, but data in New World leishmaniasis are lacking. We found that IFN-β dose-dependently increases parasite burden in Leishmania amazonensis- as well as Leishmania braziliensis-infected human macrophages, independent of endogenous or exogenous NO. However, IFN-β significantly reduced superoxide release in Leishmania-infected as well as uninfected human macrophages. This decrease in superoxide production was paralleled by a significant IFN-β-mediated increase in superoxide dismutase 1 (SOD1) protein levels. Additionally, IFN-β inhibition of leishmanicidal activity was mimicked by SOD1 and antagonized by either pharmacological or small interfering RNA-mediated inhibition of SOD1. Finally, pronounced SOD1 expression in situ was demonstrated in biopsies from New World cutaneous leishmaniasis patients. These findings reveal a hitherto unknown IFN-β/SOD1 axis in Leishmania infection and suggest that inhibition of SOD-associated pathways could serve as strategy in the treatment of L. amazonensis as well as L. braziliensis infection, major human pathogens.