bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of MHC Class II Antigen Presentation by Sorting of Recycling HLA-DM/DO and Class II within the Multivesicular Body
Authors: van Lith Marcel , van Ham Marieke , Griekspoor Alexander , Tjin Esther , Verwoerd Desiree , Calafat Jero , Janssen Hans , Reits Eric , Pastoors Liesbeth , Neefjes Jacques 
Published: April 2014

AbstractMHC class II molecules bind antigenic peptides in the late endosomal/lysosomal MHC class II compartments (MIIC) before cell surface presentation. The class II modulatory molecules HLA-DM and HLA-DO mainly localize to the MIICs. Here we show that DM/DO complexes continuously recycle between the plasma membrane and the lysosomal MIICs. Like DMβ and the class II-associated invariant chain, the DOβ cytoplasmic tail contains potential lysosomal targeting signals. The DOβ signals, however, are not essential for internalization of the DM/DO complex from the plasma membrane or targeting to the MIICs. Instead, the DOβ tail determines the distribution of both DM/DO and class II within the multivesicular MIIC by preferentially localizing them to the limiting membrane and, in lesser amounts, to the internal membranes. This distribution augments the efficiency of class II antigenic peptide loading by affecting the efficacy of lateral interaction between DM/DO and class II molecules. Sorting of DM/DO and class II molecules to specific localizations within the MIIC represents a novel way of regulating MHC class II Ag presentation.
Toll-Like Receptor 2-Dependent Inhibition of Macrophage Class II MHC Expression and Antigen Processing by 19-kDa Lipoprotein ofMycobacterium tuberculosis
Authors: Noss Erika H. , Pai Rish K. , Sellati Timothy J. , Radolf Justin D. , Belisle John , Golenbock Douglas T. , Boom W. Henry , Harding Clifford V. 
Published: April 2014

AbstractMycobacterium tuberculosis (MTB) induces vigorous immune responses, yet persists inside macrophages, evading host immunity. MTB bacilli or lysate was found to inhibit macrophage expression of class II MHC (MHC-II) molecules and MHC-II Ag processing. This report characterizes and identifies a specific component of MTB that mediates these inhibitory effects. The inhibitor was extracted from MTB lysate with Triton X-114, isolated by gel electroelution, and identified with Abs to be MTB 19-kDa lipoprotein. Electroelution- or immunoaffinity-purified MTB 19-kDa lipoprotein inhibited MHC-II expression and processing of both soluble Ags and Ag 85B from intact MTB bacilli. Inhibition of MHC-II Ag processing by either MTB bacilli or purified MTB 19-kDa lipoprotein was dependent on Toll-like receptor (TLR) 2 and independent of TLR 4. Synthetic analogs of lipopeptides from Treponema pallidum also inhibited Ag processing. Despite the ability of MTB 19-kDa lipoprotein to activate microbicidal and innate immune functions early in infection, TLR 2-dependent inhibition of MHC-II expression and Ag processing by MTB 19-kDa lipoprotein during later phases of macrophage infection may prevent presentation of MTB Ags and decrease recognition by T cells. This mechanism may allow intracellular MTB to evade immune surveillance and maintain chronic infection.
Negative Selection of T Cells byHelicobacter pylorias a Model for Bacterial Strain Selection by Immune Evasion
Authors: Wang Jide , Brooks Edward G. , Bamford Kathleen B. , Denning Timothy L. , Pappo Jacques , Ernst Peter B. 
Published: April 2014

AbstractThe majority of humans infected with Helicobacter pylori maintain a lifelong infection with strains bearing the cag pathogenicity island (PAI). H. pylori inhibits T cell responses and evades immunity so the mechanism by which infection impairs responsiveness was investigated. H. pylori caused apoptotic T cell death, whereas Campylobacter jejuni did not. The induction of apoptosis by H. pylori was blocked by an anti-Fas Ab (ZB4) or a caspase 8 inhibitor. In addition, a T cell line with the Fas rendered nonfunctional by a frame shift mutation was resistant to H. pylori-induced death. H. pylori strains bearing the cag PAI preferentially induced the expression of Fas ligand (FasL) on T cells and T cell death, whereas isogenic mutants lacking these genes did not. Inhibiting protein synthesis blocked FasL expression and apoptosis of T cells. Preventing the cleavage of FasL with a metalloproteinase inhibitor increased H. pylori-mediated killing. Thus, H. pylori induced apoptosis in Fas-bearing T cells through the induction of FasL expression. Moreover, this effect was linked to bacterial products encoded by the cag PAI, suggesting that persistent infection with this strain may be favored through the negative selection of T cells encountering specific H. pylori Ags.
Modulation of Macrophage Cytokine Production by ES-62, a Secreted Product of the Filarial NematodeAcanthocheilonema viteae
Authors: Goodridge Helen S. , Wilson Emma H. , Harnett William , Campbell Carol C. , Harnett Margaret M. , Liew Foo Y. 
Published: April 2014

AbstractParasite survival and host health may depend on the ability of the parasite to modulate the host immune response by the release of immunomodulatory molecules. Excretory-secretory (ES)-62, one such well-defined molecule, is a major secreted protein of the rodent filarial nematode Acanthocheilonema viteae, and has homologues in human filarial nematodes. Previously we have shown that ES-62 is exclusively associated with a Th2 Ab response in mice. Here we provide a rationale for this polarized immune response by showing that the parasite molecule suppresses the IFN-γ/LPS-induced production, by macrophages, of bioactive IL-12 (p70), a key cytokine in the development of Th1 responses. This suppression of the induction of a component of the host immune response extends to the production of the proinflammatory cytokines IL-6 and TNF-α, but not NO. The molecular mechanism underlying these findings awaits elucidation but, intriguingly, the initial response of macrophages to ES-62 is to demonstrate a low and transient release of these cytokines before becoming refractory to further release induced by IFN-γ/LPS. The relevance of our observations is underscored by the finding that macrophages recovered from mice exposed to “physiological” levels of ES-62 by the novel approach of continuous release from implanted osmotic pumps in vivo were similarly refractory to release of IL-12, TNF-α, IL-6, but not NO, ex vivo. Therefore, our results suggest that exposure to ES-62 renders macrophages subsequently unable to produce Th1/proinflammatory cytokines. This likely contributes to the generation of immune responses with an anti-inflammatory Th2 phenotype, a well-documented feature of filarial nematode infection.
Inhibition of Endotoxin-Induced Macrophage Chemokine Production by Vasoactive Intestinal Peptide and Pituitary Adenylate Cyclase-Activating Polypeptide In Vitro and In Vivo
Authors: Delgado Mario , Ganea Doina 
Published: April 2014

AbstractInflammatory chemokines recruit various populations of immune cells that initiate and maintain the inflammatory response against foreign Ags. Although such a response is necessary for the elimination of the Ag, the inflammation has to be eventually resolved in a healthy organism. Neuropeptides such as vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP), released after antigenic stimulation, contribute to the termination of an inflammatory response primarily by inhibiting the production of proinflammatory cytokines. Here we investigated the effects of VIP and PACAP on chemokine production. We report that VIP and PACAP inhibit the expression of the macrophage-derived CXC chemokines macrophage inflammatory protein-2 and KC (IL-8), and of the CC chemokines MIP-1α, MIP-1β, monocyte chemoattractant protein 1, and RANTES in vivo and in vitro. The inhibition of chemokine gene expression correlates with an inhibitory effect of VIP/PACAP on NF-κB binding and transactivating activity. The VIP/PACAP inhibition of both chemokine production and of NF-κB binding and transactivating activity is mediated through the specific VIP receptor VPAC1, and involves both cAMP-dependent and -independent intracellular pathways. In an in vivo model of acute peritonitis, the inhibition of chemokine production by VIP/PACAP leads to a significant reduction in the recruitment of polymorphonuclear cells, macrophages, and lymphocytes into the peritoneal cavity. These findings support the proposed role of VIP and PACAP as key endogenous anti-inflammatory agents and describe a novel mechanism, i.e., the inhibition of the production of macrophage-derived chemokines.
Cooperation of Toll-Like Receptor 2 and 6 for Cellular Activation by Soluble Tuberculosis Factor andBorrelia burgdorferiOuter Surface Protein A Lipoprotein: Role of Toll-Interacting Protein and IL-1 Receptor Signaling Molecules in Toll-Like Receptor 2 Signaling
Authors: Bulut Yonca , Faure Emmanuelle , Thomas Lisa , Equils Ozlem , Arditi Moshe 
Published: April 2014

AbstractToll-like receptor 2 (TLR2) and TLR4 play important roles in innate immune responses to various microbial agents. We have previously shown that human dermal endothelial cells (HMEC) express TLR4, but very little TLR2, and respond to LPS, but not to Mycobacterium tuberculosis 19-kDa lipoprotein, unless transfected with TLR2. Here we report that HMEC are unresponsive to several additional biologically relevant TLR2 ligands, including, phenol-soluble modulin (PSM), a complex of three small secreted polypeptides from the skin commensal Staphylococcus epidermidis, soluble tuberculosis factor (STF), and Borrelia burgdorferi outer surface protein A lipoprotein (OspA-L). Expression of TLR2 renders HMEC responsive to all these ligands. We further characterized the signaling pathway in response to STF, OspA-L, and PSM in TLR2-transfected HMEC. The TLR2 signaling pathway for NF-κB trans-activation shares the IL-1R signaling molecules. Dominant negative constructs of TLR2 or TLR6 inhibit the responses of STF and OspA-L as well as PSM in TLR2-transfected HMEC, supporting the concept of functional cooperation between TLR2 and TLR6 for all these TLR2 ligands. Moreover, we show that Toll-interacting protein (Tollip) coimmunoprecipitates with TLR2 and TLR4 using HEK 293 cells, and overexpression of Tollip inhibits NF-κB activation in response to TLR2 and TLR4 signaling. Collectively, these findings suggest that there is functional interaction between TLR2 and TLR6 in the cellular response to STF and OspA-L in addition to S. epidermidis (PSM) Ags, and that engagement of TLR2 triggers a signaling cascade, which shares the IL-1R signaling molecules, similar to the TLR4-LPS signaling cascade. Our data also suggest that Tollip may be an important constituent of both the TLR2 and TLR4 signaling pathways.
Human Eosinophils and Human High Affinity IgE Receptor Transgenic Mouse Eosinophils Express Low Levels of High Affinity IgE Receptor, but Release IL-10 upon Receptor Activation
Authors: Kayaba Hiroyuki , Dombrowicz David , Woerly Gaetane , Papin Jean-Paul , Loiseau Sylvie , Capron Monique 
Published: April 2014

AbstractFcεRI expressed by human eosinophils is involved in IgE-mediated cytotoxicity reactions toward the parasite Schistosoma mansoni in vitro. However, because receptor expression is low on these cells, its functional role is still controversial. In this study, we have measured surface and intracellular expression of FcεRI by blood eosinophils from hypereosinophilic patients and normal donors. The number of unoccupied receptors corresponded to ∼4,500 Ab binding sites per cell, whereas 50,000 Ab binding sites per cell were detected intracellularly. Eosinophils from patients displayed significantly more unoccupied receptors than cells from normal donors. This number correlated to both serum IgE concentrations and to membrane-bound IgE. The lack of FcεRI expression by mouse eosinophils has hampered further studies. To overcome this fact and experimentally confirm our findings on human eosinophils, we engineered IL-5 × hFcεRIα double-transgenic mice, whose bone marrow, blood, spleen, and peritoneal eosinophils expressed FcεRI levels similar to levels of human eosinophils, after 4 days culture with IgE in the presence of IL-5. Both human and mouse eosinophils were able to secrete IL-10 upon FcεRI engagement. Thus, comparative analysis of cells from patients and from a relevant animal model allowed us to clearly demonstrate that FcεRI-mediated eosinophil activation leads to IL-10 secretion. Through FcεRI expression, these cells are able to contribute to both the regulation of the immune response and to its effector mechanisms.
Cutting Edge: Control of CD8+ T Cell Activation by CD4+CD25+ Immunoregulatory Cells
Authors: Piccirillo Ciriaco A. , Shevach Ethan M. 
Published: April 2014

Abstract
CD4+CD25+ regulatory T cells inhibit organ-specific autoimmune diseases induced by CD4+CD25− T cells and are potent suppressors of CD4+CD25− T cell activation in vitro. We demonstrate that CD4+CD25+ T cells also suppress both proliferation and IFN-γ production by CD8+ T cells induced either by polyclonal or Ag-specific stimuli. CD4+CD25+ T cells inhibit the activation of CD8+ responders by inhibiting both IL-2 production and up-regulation of IL-2Rα-chain (CD25) expression. Suppression is mediated via a T-T interaction as activated CD4+CD25+ T cells suppress the responses of TCR-transgenic CD8+ T cells stimulated with soluble peptide-MHC class I tetramers in the complete absence of APC. These results broaden the immunoregulatory role played by CD4+CD25+ T cells in the prevention of autoimmune diseases, but also raise the possibility that they may hinder the induction of effector CD8+ T cells to tumor or foreign Ags.
Clonotypic Structure of the Human CD4+ Memory T Cell Response to Cytomegalovirus
Authors: Bitmansour Arlene D. , Waldrop Shar L. , Pitcher Christine J. , Khatamzas Elham , Kern Florian , Maino Vernon C. , Picker Louis J. 
Published: April 2014

Abstract
High steady-state frequencies of CMV-specific CD4+ memory T cells are maintained in CMV-exposed subjects, and these cells are thought to play a key role in the immunologic control of this permanent infection. However, the essential components of this response are poorly defined. Here, we report the use of a step-wise application of flow cytometric and molecular techniques to determine the number and size of the TCR Vβ-defined clonotypes within freshly obtained CMV-specific CD4+ memory T cell populations of four healthy, CMV-exposed human subjects. This analysis revealed a stable clonotypic hierarchy in which 1–3 dominant clonotypes are maintained in concert with more numerous subdominant and minor clonotypes. These dominant clonotypes accounted for 10–50% of the overall CMV response, and comprised from 0.3 to 4.0% of peripheral blood CD4+ T cells. Two subjects displayed immunodominant responses to single epitopes within the CMV matrix phosphoprotein pp65; these single epitope responses were mediated by a single dominant clonotype in one subject, and by multiple subdominant and minor clonotypes in the other. Thus, the CMV-specific CD4+ T cell memory repertoire in normal subjects is characterized by striking clonotypic dominance and the potential for epitope focusing, suggesting that primary responsibility for immunosurveillance against CMV reactivation rests with a handful of clones recognizing a limited array of CMV determinants. These data have important implications for the understanding of mechanisms by which a genetically stable chronic viral pathogen such as CMV is controlled, and offer possible insight into the failure of such control for a genetically flexible pathogen like HIV-1.
CD1d-Restricted NKT Cells: An Interstrain Comparison
Authors: Hammond Kirsten J. L. , Pellicci Daniel G. , Poulton Lynn D. , Naidenko Olga V. , Scalzo Anthony A. , Baxter Alan G. , Godfrey Dale I. 
Published: April 2014

AbstractCD1d-restricted Vα14-Jα281 invariant αβTCR+ (NKT) cells are well defined in the C57BL/6 mouse strain, but they remain poorly characterized in non-NK1.1-expressing strains. Surrogate markers for NKT cells such as αβTCR+CD4−CD8− and DX5+CD3+ have been used in many studies, although their effectiveness in defining this lineage remains to be verified. Here, we compare NKT cells among C57BL/6, NK1.1-congenic BALB/c, and NK1.1-congenic nonobese diabetic mice. NKT cells were identified and compared using a range of approaches: NK1.1 expression, surrogate phenotypes used in previous studies, labeling with CD1d/α-galactosylceramide tetramers, and cytokine production. Our results demonstrate that NKT cells and their CD4/CD8-defined subsets are present in all three strains, and confirm that nonobese diabetic mice have a numerical and functional deficiency in these cells. We also highlight the hazards of using surrogate phenotypes, none of which accurately identify NKT cells, and one in particular (DX5+CD3+) actually excludes these cells. Finally, our results support the concept that NK1.1 expression may not be an ideal marker for CD1d-restricted NKT cells, many of which are NK1.1-negative, especially within the CD4+ subset and particularly in NK1.1-congenic BALB/c mice.
Rejection of Mouse Cardiac Allografts by Costimulation in trans
Authors: Mandelbrot Didier A. , Kishimoto Koji , Auchincloss Hugh , Sharpe Arlene H. , Sayegh Mohamed H. 
Published: April 2014

Abstract
The activation of T cells by B7 costimulation in trans has been demonstrated in vitro, but the in vivo relevance is unknown. To study costimulation in trans of CD4+ T cells in vivo, we performed cardiac transplants from B7-1/B7-2-deficient mice to recipients that do not express MHC class II molecules on peripheral APCs, but do have functional CD4+ T cells (II−/4+ mice). This model restricts the B7-dependent activation of CD4+ T cells to costimulation in trans and excludes any contribution from indirect Ag presentation. We find that II−/4+ recipients reject B7-deficient grafts as rapidly as wild-type grafts, suggesting that costimulation in trans can mediate rejection as potently as costimulation in cis. Treatment of II−/4+ recipients of B7-deficient grafts with depleting Abs to CD4 or CD8 demonstrates that indirect Ag presentation to CD8+ cells does not significantly contribute to rejection. This is the first demonstration that costimulation in trans can mediate an immune response in vivo and has important therapeutic implications.
IL-15 Is Expressed by Dendritic Cells in Response to Type I IFN, Double-Stranded RNA, or Lipopolysaccharide and Promotes Dendritic Cell Activation
Authors: Mattei Fabrizio , Schiavoni Giovanna , Belardelli Filippo , Tough David F. 
Published: April 2014

AbstractCytokines that are induced by infection may contribute to the initiation of immune responses through their ability to stimulate dendritic cells (DCs). In this paper, we have addressed the role of IL-15 in DC activation, investigating its expression by DCs in response to three different signals of infection and examining its ability to stimulate DCs. We report that the expression of both IL-15 and the IL-15 receptor α-chain are increased in splenic DCs from mice inoculated with dsRNA (poly(I:C)), LPS, or IFN-αβ, and in purified murine splenic DCs treated with IFN-αβ in vitro. Furthermore, IL-15 itself was able to activate DCs, as in vivo or in vitro exposure of splenic DCs to IL-15 resulted in an up-regulation of costimulatory molecules, markedly increased production of IFN-γ by DC and an enhanced ability of DCs to stimulate Ag-specific CD8+ T cell proliferation. The magnitude of all of the IL-15-induced changes in DCs was reduced in mice deficient for the IFN-αβ receptor, suggesting a role for IFN-αβ in the stimulation of DCs by IL-15. These results identify IL-15 as a stimulatory cytokine for DCs with the potential for autocrine activity and link its effects to expression of IFN-αβ.
Mature Dendritic Cells Prime Functionally Superior Melan-A-Specific CD8+ Lymphocytes as Compared with Nonprofessional APC
Authors: Salio Mariolina , Shepherd Dawn , Dunbar P. Rod , Palmowski Michael , Murphy Kristine , Wu Lijun , Cerundolo Vincenzo 
Published: April 2014

Abstract
Priming of melan-A26/27–35-specific CTL occurs only in a fraction of late stage melanoma patients, whereas during the early stages of the disease and in healthy volunteers, melan-A CTL have functional and phenotypic markers consistent with a naive phenotype. To study the requirements for expansion of naive melan-A CTL from healthy donors, we set up an in vitro priming protocol and, using tetramer assays, we demonstrate that the activity and phenotype of the expanded melan-A CTL are profoundly influenced by the type of APC used. Priming by nonprofessional APC leads to expansion of melan-A CTL with reduced cytolytic activity and low level of IFN-γ secretion. In contrast, mature dendritic cells (DC) expand cytolytic and IFN-γ-producing melan-A CTL. Priming by mature DC is also efficient at low peptide concentration and requires only one round of stimulation. Finally, we observed that a significant fraction of CD45RO+ melan-A CTL primed by mature DC expresses high levels of the homing receptor CD62L, whereas CTL primed by nonprofessional APC express CD62L in lower percentages and at lower levels. These results suggest that suboptimal priming by nonprofessional APC could account for the presence in vivo of dysfunctional cells and strongly support the immunotherapeutic use of mature DC for expansion of effector and memory Ag-specific CTL.
Differences in the Expression of Human Class I MHC Alleles and Their Associated Peptides in the Presence of Proteasome Inhibitors
Authors: Luckey Chance John , Marto Jarrod A. , Partridge Megan , Hall Ed , White Forest M. , Lippolis John D. , Shabanowitz Jeffrey , Hunt Donald F. , Engelhard Victor H. 
Published: April 2014

AbstractWe have studied the contributions of proteasome inhibitor-sensitive and -insensitive proteases to the generation of class I MHC-associated peptides. The cell surface expression of 13 different human class I MHC alleles was inhibited by as much as 90% or as little as 40% when cells were incubated with saturating concentrations of three different proteasome inhibitors. Inhibitor-resistant class I MHC expression was not due to TAP-independent expression or preexisting internal stores of peptides. Furthermore, it did not correlate with the amount or specificity of residual proteasome activity as determined in in vitro proteolysis assays and was not augmented by simultaneous incubation with multiple inhibitors. Mass spectrometry was used to directly characterize the peptides expressed in the presence and absence of proteasome inhibitors. The number of peptide species detected correlated with the levels of class I detected by flow cytometry. Thus, for many alleles, a significant proportion of associated peptide species continue to be generated in the presence of saturating levels of proteasome inhibitors. Comparison of the peptide-binding motifs of inhibitor-sensitive and -resistant class I alleles further suggested that inhibitor-resistant proteolytic activities display a wide diversity of cleavage specificities, including a trypsin-like activity. Sequence analysis demonstrated that inhibitor-resistant peptides contain diverse carboxyl termini and are derived from protein substrates dispersed throughout the cell. The possible contributions of inhibitor-resistant proteasome activities and nonproteasomal proteases residing in the cytosol to the peptide profiles associated with many class I MHC alleles are discussed.