bluuebunny/crossref_metadata_2025_split huggingface dataset:
CD4 Dimers Constitute the Functional Component Required for T Cell Activation
Authors: Moldovan Maria-Cristina , Yachou Abdelkader , Lévesque Karine , Wu Hao , Hendrickson Wayne A. , Cohen Eric A. , Sékaly Rafick-Pierre 
Published: April 2014

Abstract
The CD4 molecule plays a key role in the development and activation of helper T cells. Dimerization and oligomerization is often a necessary step in the function of several cell surface receptors. Herein, we provide direct biochemical evidence confirming the presence of CD4 as dimers in transfected cells from hemopoetic and fibroblastic origin as well as in primary T cells. Such dimers are also observed with murine CD4 confirming selective pressure during evolution to maintain such a structure. Using a series of point mutations, we have precisely mapped the dimerization site at residues K318 and Q344 within the fourth extracellular domain of CD4. These residues are highly conserved and their mutation results in interference with dimer formation. More importantly, we demonstrate that dimer formation is essential for the coligand and coreceptor functions of CD4 in T cell activation. These data strongly suggest that CD4 dimerization is necessary for helper T cell function.
Regulation of Constitutive TCR Internalization by the ζ-Chain
Authors: D’Oro Ugo , Munitic Ivana , Chacko George , Karpova Tatiana , McNally James , Ashwell Jonathan D. 
Published: April 2014

Abstract
The ability of a T cell to be activated is critically regulated by the number of TCRs expressed on the plasma membrane. Cell surface TCR expression is influenced by dynamic processes such as synthesis and transport of newly assembled receptors, endocytosis of surface TCR, and recycling to the plasma membrane of internalized receptors. In this study, the internalization of fluorescently labeled anti-TCR Abs was used to analyze constitutive endocytosis of TCRs on T cells, and to investigate the role of the ζ-chain in this process. We found that cell surface TCRs lacking ζ were endocytosed more rapidly than completely assembled receptors, and that reexpression of full-length ζ led to a dose-dependent decrease in the rate of TCR internalization. Rapid TCR internalization was also observed with CD4+CD8+ thymocytes from ζ-deficient mice, whereas TCR internalization on thymocytes from CD3-δ deficient animals was slow, similar to that of wild-type thymocytes. This identifies a specific role for ζ in the regulation of constitutive receptor internalization. Furthermore, chimeric ζ molecules containing non-native intracellular amino acid sequences also led to high levels of TCR expression and reduced TCR cycling. These effects were dependent solely on the length of the intracellular tail, ruling out a role for intracellular ζ-specific interactions with other molecules as a mechanism for regulating TCR internalization. Rather, these findings strongly support a model in which the ζ-chain stabilizes TCR residency on the cell surface, and functions to maintain cell surface receptor expression by sterically blocking internalization sequences in other TCR components.
Making Sense of the Diverse Ligand Recognition by NKG2D
Authors: Radaev Sergei , Kattah Michael , Zou Zhongcheng , Colonna Marco , Sun Peter D. 
Published: April 2014

Abstract
NKG2D recognizes multiple diverse ligands. Despite recent efforts in determining the crystal structures of NKG2D-ligand complexes, the principle governing this receptor-ligand recognition and hence the criteria for identifying unknown ligands of NKG2D remain central issues to be resolved. Here we compared the molecular recognition between NKG2D and three of the known ligands, UL16 binding protein (ULBP), MHC class I-like molecule, and retinoic acid early inducible gene as observed in the ligand-complexed crystal structures. The comparison shows that while the receptor uses a common interface region to bind the three diverse ligands, each ligand forms a distinct, but overlapping, set of hydrogen bonds, hydrophobic interactions, and salt bridges, illustrating the underlying principle of NKG2D-ligand recognition being the conservation in overall shape complementarity and binding energy while permitting variation in ligand sequence through induced fit recognition. To further test this hypothesis and to distinguish between diverse recognition and promiscuous ligand binding, four ULBP3 interface mutations, H21A, E76A, R82M, and D169A, were generated to each disrupt a single hydrogen bond or salt bridge. All mutant ULBP3 displayed reduced receptor binding, suggesting a specific, rather than promiscuous, receptor-ligand recognition. Mutants with severe loss of binding affect the receptor interactions that are mostly buried. Finally, a receptor-ligand recognition algorithm was developed to assist the identification of diverse NKG2D ligands based on evaluating the potential hydrogen bonds, hydrophobic interactions, and salt bridges at the receptor-ligand interface.
Mycobacterium aviumInfection and Modulation of Human Macrophage Gene Expression
Authors: Greenwell-Wild Teresa , Vázquez Nancy , Sim Davis , Schito Marco , Chatterjee Delphi , Orenstein Jan M. , Wahl Sharon M. 
Published: April 2014

AbstractMycobacterium avium is a facultative intracellular pathogen cleared rapidly via intact host defense mechanisms. In the absence of adequate T cell function, as occurs in HIV-1-induced immunodeficiency, M. avium becomes an opportunistic infection with uncontrolled replication and reinfection of macrophage hosts. How M. avium infects, survives, and replicates in macrophages without signaling an effective microbicidal counterattack is unresolved. To address whether M. avium signals the expression of molecules, which influence mycobacterial survival or clearance, human monocyte-derived macrophage cultures were exposed to M. avium. Within minutes, M. avium, or its cell wall lipoarabinomannan, binds to the adherent macrophages and induces a spectrum of gene expression. In this innate response, the most abundant genes detected within 2 h by cDNA expression array involved proinflammatory chemokines, cytokines including TNF-α and IL-1, and adhesion molecules. Associated with this rapid initial up-regulation of recruitment and amplification molecules was enhanced expression of transcription factors and signaling molecules. By 24 h, this proinflammatory response subsided, and after 4 days, when some bacteria were being degraded, others escaped destruction to replicate within intracellular vacuoles. Under these conditions, inducible NO synthase was not up-regulated and increased transferrin receptors may facilitate iron-dependent mycobacterial growth. Sustained adhesion molecule and chemokine expression along with the formation of multinucleated giant cells appeared consistent with in vivo events. Thus, in the absence of T lymphocyte mediators, macrophages are insufficiently microbicidal and provide a nonhostile environment in which mycobacteria not only survive and replicate, but continue to promote recruitment of new macrophages to perpetuate the infection.
B7/CD28-Dependent CD4+CD25+ Regulatory T Cells Are Essential Components of the Memory-Protective Immunity to Candida albicans
Authors: Montagnoli Claudia , Bacci Angela , Bozza Silvia , Gaziano Roberta , Mosci Paolo , Sharpe Arlene H. , Romani Luigina 
Published: April 2014

Abstract
Protective immunity to the fungus Candida albicans is mediated by Ag-specific Th1 cells. Paradoxically, some Th2 cytokines are required for the maintenance of Th1-mediated immune resistance to the fungus. Therefore, in addition to the Th1/Th2 balance, other mechanisms seem to be involved in the regulation of Th1 immunity to the fungus. Here we show that CD4+CD25+ T cells, negatively regulating antifungal Th1 reactivity, are generated in mice with candidiasis. CD4+CD25+ T cells were not generated in B7-2- or CD28-deficient mice or in condition of IL-10 signaling deficiency. Accordingly, although capable of efficiently restricting the fungal growth, these mice experienced inflammatory pathology and were incapable of resistance to reinfection. CD4+CD25+ T cells poorly proliferated in vitro; were highly enriched for cells producing IL-4, IL-10, and TGF-β; and required IL-10-producing, Candida hypha-activated dendritic cells for generation. Adoptive transfer of CD4+CD25+ T cells or IL-10-producing dendritic cells restored resistance to reinfection and decreased inflammation in B7-2-deficient mice. These results show that oral tolerance induced by Candida hyphae is required for the occurrence of long-lasting protective immunity after yeast priming. The implication is that preventing reactivation rather than favoring sterilizing immunity to ubiquitous fungal pathogens may represent the ultimate expectation of vaccine-based strategies.
IFN-γ-Induced Apoptosis and Microbicidal Activity in Monocytes Harboring the Intracellular Bacterium Coxiella burnetii Require Membrane TNF and Homotypic Cell Adherence
Authors: Dellacasagrande Jérôme , Ghigo Eric , Raoult Didier , Capo Christian , Mege Jean-Louis 
Published: April 2014

Abstract
IFN-γ is critical for the protection against intracellular bacteria through activation of the antimicrobial machinery of phagocytes. Coxiella burnetii, the etiological agent of Q fever, is a strictly intracellular bacterium that inhabits monocytes/macrophages. We previously showed that IFN-γ induced C. burnetii killing by promoting the apoptosis of infected monocytes. We show in this study that IFN-γ-induced apoptosis of infected monocytes was characterized by a time- and dose-dependent activation of caspase-3. IFN-γ-mediated caspase-3 activation and C. burnetii killing depend on the expression of membrane TNF. Indeed, TNF was transiently expressed on the cell surface of infected monocytes a few hours after IFN-γ treatment. In addition, anti-TNF Abs inhibited IFN-γ-mediated caspase-3 activation whereas soluble TNF had no effect on infected cells. Concomitantly, IFN-γ induced homotypic adherence of C. burnetii-infected monocytes. The latter required the interaction of β2 integrins with CD54. When adherence was disrupted by pipetting, by a combination of Abs specific for CD11b, CD18, and CD54, or by an antisense oligonucleotide targeting CD18 mRNA, both cell apoptosis and bacterial killing induced by IFN-γ were inhibited. Thus, adherence via CD54/β2 integrins together with membrane TNF are required to eliminate C. burnetii-infected cells through cell contact-dependent apoptosis. Our results reveal a new component of the antimicrobial arsenal mobilized by IFN-γ against infection by intracellular bacteria.
Evolution of the Cutaneous Immune Response to Experimental Haemophilus ducreyi Infection and Its Relevance to HIV-1 Acquisition
Authors: Humphreys Tricia L. , Schnizlein-Bick Carol T. , Katz Barry P. , Baldridge Lee Ann , Hood Antoinette F. , Hromas Robert A. , Spinola Stanley M. 
Published: April 2014

Abstract
Haemophilus ducreyi causes the sexually transmitted disease chancroid, which facilitates HIV-1 transmission. Skin biopsies were obtained from subjects experimentally infected with H. ducreyi to study the evolution of the immune response and immunophenotypes relevant to transmission of HIV-1. Compared with peripheral blood, there was an enrichment of T cells and macrophages after 48 h of infection in the skin. Neutrophils became the predominant cell type by 7–9 days. By immunohistochemistry, macrophage-inflammatory protein-1α was not present early in infection, but was abundant at later stages. RANTES was present throughout the papular and pustular stages of experimental infection, but not present in uninfected control skin. Stromal cell-derived factor-1 was present at low levels in all samples examined. Macrophages in lesions had significantly increased expression of CCR5 and CXCR4 compared with peripheral blood cells, and CD4 T cells had significant up-regulation of CCR5. The magnitude of increased expression of these receptors was not replicated when PBMCs were incubated with H. ducreyi or H. ducreyi lipooligosaccharide in vitro. Together with the disruption of mucosal and skin barriers, the presence of cells with up-regulated HIV-1 coreceptors in H. ducreyi-infected lesions may provide an environment that facilitates the acquisition of R5 (CCR5), X4 (CXCR4), and dual-tropic HIV-1 strains.
GM-CSF Transgene-Based Adjuvant Allows the Establishment of Protective Mucosal Immunity Following Vaccination with Inactivated Chlamydia trachomatis
Authors: Lu Hang , Xing Zhou , Brunham Robert C. 
Published: April 2014

Abstract
Cellular and humoral immune responses induced following murine Chlamydia trachomatis infection confer almost sterile protection against homologous reinfection. On the other hand, immunization with inactivated organism induces little protective immunity in this model system. The underlying mechanism(s) that determines such divergent outcome remains unclear, but elucidating the mechanism will probably be important for chlamydial vaccine development. One of the distinct differences between the two forms of immunization is that chlamydia replication in epithelial cells causes the secretion of a variety of proinflammatory cytokines and chemokines, such as GM-CSF, that may mobilize and mature dendritic cells and thereby enhance the induction of protective immunity. Using a murine model of C. trachomatis mouse pneumonitis lung infection and intrapulmonary adenoviral GM-CSF transfection, we demonstrate that the expression of GM-CSF in the airway compartment significantly enhanced systemic Th1 cellular and local IgA immune responses following immunization with inactivated organisms. Importantly, immunized mice had significantly reduced growth of chlamydia and exhibited less severe pulmonary inflammation following challenge infection. The site of GM-CSF transfection proved important, since mice immunized with inactivated organisms after GM-CSF gene transfer by the i.p. route exhibited little protection against pulmonary challenge, although i.p. immunization generated significant levels of systemic Th1 immune responses. The obvious difference between i.p. and intrapulmonary immunization was the absence of lung IgA responses following i.p. vaccination. In aggregate, the findings demonstrate that the local cytokine environment is critical to the induction of protective immunity following chlamydial vaccination and that GM-CSF may be a useful adjuvant for a chlamydial vaccine.
Endocytic Internalization of Adenovirus, Nonspecific Phagocytosis, and Cytoskeletal Organization Are Coordinately Regulated in Alveolar Macrophages by GM-CSF and PU.1
Authors: Berclaz Pierre-Yves , Zsengellér Zsuzsanna , Shibata Yoko , Otake Kazuhisa , Strasbaugh Steven , Whitsett Jeffrey A. , Trapnell Bruce C. 
Published: April 2014

AbstractGM-CSF gene-targeted (GM−/−) mice have impaired pulmonary clearance of bacterial and fungal pathogens by alveolar macrophages (AMs). Because AMs also clear adenovirus from the lung, the role of GM-CSF in endocytic internalization of adenovirus by AMs was evaluated. Pulmonary clearance of adenovirus was severely impaired in GM−/− mice compared to wild-type (GM+/+) mice as determined by Southern analysis of viral DNA. Internalization of adenovirus by AMs was deficient in GM−/− mice in vivo and in vitro as determined by uptake of fluorescently labeled adenovirus or by PCR quantification of adenoviral DNA internalized within AMs. An AM cell line previously established from GM−/− mice (mAM) had impaired internalization of adenovirus and transferrin-coated 100-nm latex beads compared to MH-S, a GM+/+ AM cell line. Phagocytosis of 4-μm latex beads was also impaired in mAM cells as determined by confocal and fluorescence microscopy. Retroviral vector-mediated reconstitution of PU.1 expression in cultured GM−/− AMs restored phagocytosis of 4-μm beads, endocytosis of adenovirus, and transferrin-coated 100-nm beads (independent of integrin αV and transferrin receptors, respectively), and restored normal cytoskeletal organization, filamentous actin distribution, and stimulated formation of filopodia. Interestingly, mRNA for the phosphoinositide 3 kinase p110γ isoform, important in macrophage phagocytic function, was absent in GM−/− AMs and was restored by PU.1 expression. These data show that GM-CSF, via PU.1, regulates endocytosis of small (∼100 nm) pathogens/inert particles and phagocytosis of very large inert particles and suggests regulation of cytoskeletal organization by GM-CSF/PU.1 as the molecular basis of this control.
In Vivo IL-10 Production Reactivates Chronic Pulmonary Tuberculosis in C57BL/6 Mice
Authors: Turner Joanne , Gonzalez-Juarrero Mercedes , Ellis Debi L. , Basaraba Randy J. , Kipnis Andre , Orme Ian M. , Cooper Andrea M. 
Published: April 2014

Abstract
The production of immunosuppressive cytokines, such as IL-10 and TGF-β, has been documented in individuals diagnosed with active tuberculosis. In addition, IL-10 production is increased within the lungs of mice that have chronic mycobacterial infection. Therefore, we hypothesized that the down-regulatory properties of IL-10 might contribute to the reactivation of chronic Mycobacterium tuberculosis infection in mice. To determine the influence of IL-10 on the course of infection, transgenic mice producing increased amounts of IL-10 under the control of the IL-2 promotor were infected with M. tuberculosis via the respiratory route. Mice that overexpressed IL-10 showed no increase in susceptibility during the early stages of infection, but during the chronic phase of the infection showed evidence of reactivation tuberculosis with a highly significant increase in bacterial numbers within the lungs. Reactivation was associated with the formation of macrophage-dominated lesions, decreased mRNA production for TNF and IL-12p40, and a decrease in Ag-specific IFN-γ secretion. These data support the hypothesis that IL-10 plays a pivotal role during the chronic/latent stage of pulmonary tuberculosis, with increased production playing a potentially central role in promoting reactivation tuberculosis.
A Novel Interaction of Outer Membrane Protein A with C4b Binding Protein Mediates Serum Resistance of Escherichia coli K1
Authors: Prasadarao Nemani V. , Blom Anna M. , Villoutreix Bruno O. , Linsangan Linette C. 
Published: April 2014

Abstract
Escherichia coli is an important pathogen that causes meningitis in neonates. The development of bacteremia preceding the traversal across the blood-brain barrier is a prerequisite for this pathogen that obviously must survive the bactericidal activity of serum. Here we report that outer membrane protein A (OmpA) of Escherichia coli contributes to serum resistance by binding to C4b binding protein (C4bp), a complement fluid phase regulator. C4bp contains seven identical α-chains and one β-chain linked together with disulfide bridges. We found that OmpA binds the α-chain of C4bp, which is composed of eight homologous complement control protein (CCP) modules. Binding studies using mutants of recombinant C4bp that lack one CCP at a time suggest that CCP3 is the major site of interaction with OmpA. Furthermore, we demonstrate that the N terminus of OmpA interacts with C4bp. Binding of C4bp to OmpA is not significantly inhibited in the presence of either C4b or heparin and is not salt sensitive, implying that it is hydrophobic in nature, suggesting a novel interaction between OmpA and C4bp. A compelling observation in this study is that synthetic peptides corresponding to CCP3 sequences block the binding of C4bp to OmpA and also significantly enhance serum bactericidal activity.
HIV-1 Protein Vpr Suppresses IL-12 Production from Human Monocytes by Enhancing Glucocorticoid Action: Potential Implications of Vpr Coactivator Activity for the Innate and Cellular Immunity Deficits Observed in HIV-1 Infection
Authors: Mirani Marco , Elenkov Ilia , Volpi Simona , Hiroi Naoki , Chrousos George P. , Kino Tomoshige 
Published: April 2014

Abstract
The HIV-1 protein Vpr has glucocorticoid receptor coactivator activity, potently increasing the sensitivity of glucocorticoid target tissues to cortisol. Patients with AIDS and normal cortisol secretion have manifestations compatible with glucocorticoid hypersensitivity of the immune system, such as suppression of innate and cellular immunities. The latter can be explained by glucocorticoid-induced inhibition of cytokine networks regulating innate and Th1-driven cellular immunity. We demonstrated that extracellularly administered Vpr protein dose-dependently potentiated glucocorticoid-induced suppression of both mRNA expression and secretion of IL-12 subunit p35 and IL-12 holo-protein, but not IL-12 subunit p40 or IL-10, by human monocytes/macrophages stimulated with LPS or heat-killed, formalin-fixed Staphylococcus aureus (Cowan strain 1). This effect was inhibited by the glucocorticoid receptor antagonist RU 486. Also, Vpr changed the expression of an additional five glucocorticoid-responsive genes in the same direction as dexamethasone and was active in potentiating the trans-activation, but not the trans-repression, properties of the glucocorticoid receptor on nuclear factor κB- or activating protein 1-regulated simple promoters. Thus, extracellular Vpr enhances the suppressive actions of the ligand-activated glucocorticoid receptor on IL-12 secretion by human monocytes/macrophages. Through this effect, Vpr may contribute to the suppression of innate and cellular immunities of HIV-1-infected individuals and AIDS patients.
On the Pathogenic Role of Brain-Sequestered αβ CD8+ T Cells in Experimental Cerebral Malaria
Authors: Belnoue Elodie , Kayibanda Michèle , Vigario Ana M. , Deschemin Jean-Christophe , Rooijen Nico van , Viguier Mireille , Snounou Georges , Rénia Laurent 
Published: April 2014

Abstract
Cerebral malaria (CM) develops in a small proportion of persons infected with Plasmodium falciparum and accounts for a substantial proportion of the mortality due to this parasite. The actual pathogenic mechanisms are still poorly understood, and in humans investigations of experimental CM are unethical. Using an established Plasmodium berghei-mouse CM model, we have investigated the role of host immune cells at the pathological site, the brain. We report in this study the detailed quantification and characterization of cells, which migrated and sequestered to the brain of mice with CM. We demonstrated that CD8+ αβ T cells, which sequester in the brain at the time when neurological symptoms appear, were responsible for CM mortality. These observations suggest a mechanism which unifies disparate observations in humans.