bluuebunny/crossref_metadata_2025 huggingface dataset:
CpG Oligonucleotides Are Potent Adjuvants for the Activation of Autoreactive Encephalitogenic T Cells In Vivo
Authors: Segal Benjamin M. , Chang John T. , Shevach Ethan M.
Published: April 2014

The mechanism of action of microbial adjuvants in promoting the differentiation of autoimmune effector cells remains to be elucidated. We demonstrate that CpG-containing oligodeoxynucleotides (ODN) can completely substitute for heat-killed mycobacteria in the priming of encephalitogenic myelin-reactive T cells in vivo. The adjuvanticity of the CpG ODN was secondary to their direct ability to induce IL-12 or to act synergistically with endogenous IL-12 to promote Th1 differentiation and encephalitogenicity. T cells primed in the absence of CpG with Ag and IFA alone appeared to be in a transitional state and had not undergone differentiation along a conventional Th pathway. Unlike Th2 cells, they expressed low levels of the IL-12Rβ2 subunit and retained the ability to differentiate into encephalitogenic effectors when reactivated in vitro under Th1-polarizing conditions. These results support the use of CpG ODN as adjuvants but also suggest that they could potentially trigger autoimmune disease in a susceptible individual.
Gestational Age-Dependent Expression of IL-10 and Its Receptor in Human Placental Tissues and Isolated Cytotrophoblasts
Authors: Hanna Nazeeh , Hanna Iman , Hleb Marija , Wagner Eric , Dougherty John , Balkundi Dhruv , Padbury James , Sharma Surendra
Published: April 2014

Control of antifetal immune responses is thought to be regulated locally by the placenta. Because the physiologic programming of the placenta across gestation is likely to influence the local immunity, we hypothesize that a potent anti-inflammatory cytokine such as IL-10 may be produced in a gestational age-dependent manner. In the present study, we examined the expression of IL-10 and its receptor in placental explants or freshly isolated cytotrophoblasts from different gestational ages and compared it with the expression profiles of other cytokines. First and second trimester placental tissues from normal pregnancies predominantly expressed IL-10, whereas the levels of IL-2, IL-4, and IFN-γ were mostly below detection throughout pregnancy. The expression of IL-10, but not its receptor, diminished significantly in term placental tissues collected “before” the onset of labor and did not change appreciably “after” labor. On the other hand, TNF-α and IL-1β were significantly up-regulated in response to labor-associated conditions. IL-10 expression was transcriptionally attenuated at term as observed in cytotrophoblasts. In contrast to the placental cytokine milieu, autologous PBMCs, when activated with PHA, secreted significant amounts of IL-2, IL-4, IL-10, and IFN-γ, albeit with a statistically significantly enhanced IL-10 production in first trimester compared with age-matched nonpregnant women. These data suggest that IL-10 is expressed in the placenta in a gestational age-dependent manner and that its down-regulation at term may be an important mechanism underlying the subtle changes associated with parturition.
Identification of Murine Germinal Center B Cell Subsets Defined by the Expression of Surface Isotypes and Differentiation Antigens
Authors: Shinall Stephen M. , Gonzalez-Fernandez Mercedes , Noelle Randolph J. , Waldschmidt Thomas J.
Published: April 2014

Germinal centers (GCs) are inducible lymphoid microenvironments that support the generation of memory B cells, affinity maturation, and isotype switching. Previously, phenotypic transitions following in vivo B cell activation have been exploited to discriminate GC from non-GC B cells in the mouse and to delineate as many as seven distinct human peripheral B cell subsets. To better understand the differentiative processes occurring within murine GCs, we sought to identify subpopulations of GC B cells corresponding to discrete stages of GC B cell ontogeny. We performed multiparameter flow-cytometric analyses of GC B cells at consecutive time points following immunization of BALB/c mice with SRBC. We resolved the murine GC compartment into subsets based on the differential expression of activation markers, surface Ig isotypes, and differentiation Ags. Class-switched and nonswitched GC B cells emerged contemporaneously, and their relative frequencies remained nearly constant throughout the GC reaction, perhaps reflecting the establishment of a steady state. A significant percentage of the nonswitched B cells with a GC phenotype exhibited surface markers associated with naive B cells, including CD23, surface IgD, and high levels of CD38 consistent with either prolonged recruitment into the GC reaction or protracted expression of these markers during differentiation within the GC. Expression of the activation marker BLA-1 was dynamic over time, with all GC B cells being positive early after immunization, followed by progressive loss as the GC reaction matured into the second and third week. Implications of these results concerning GC evolution are discussed.
Molecular Basis for Recognition of an Arthritic Peptide and a Foreign Epitope on Distinct MHC Molecules by a Single TCR
Authors: Basu Devraj , Horvath Stephen , Matsumoto Isao , Fremont Daved H. , Allen Paul M.
Published: April 2014

KRN TCR transgenic T cells recognize two self-MHC molecules: a foreign peptide, bovine RNase 42–56, on I-Ak and an autoantigen, glucose-6-phosphate isomerase 282–294, on I-Ag7. Because the latter recognition event initiates a disease closely resembling human rheumatoid arthritis, we investigated the structural basis of this pathogenic TCR’s dual specificity. While peptide recognition is altered to a minor degree between the MHC molecules, we show that the receptor’s cross-reactivity critically depends upon a TCR contact residue completely conserved in the foreign and self peptides. Further, the altered recognition of peptide derives from discrete differences on the MHC recognition surfaces and not the disparate binding grooves. This work provides a detailed structural comparison of an autoreactive TCR’s interactions with naturally occurring peptides on distinct MHC molecules. The capacity to interact with multiple self-MHCs in this manner increases the number of potentially pathogenic self-interactions available to a T cell.
GRID: A Novel Grb-2-Related Adapter Protein That Interacts with the Activated T Cell Costimulatory Receptor CD28
Authors: Ellis Jonathan H. , Ashman Claire , Burden M. Neil , Kilpatrick Katherine E. , Morse Mary A. , Hamblin Paul A.
Published: April 2014

Adapter proteins such as Grb2 play a central role in the formation of signaling complexes through their association with multiple protein binding partners. These interactions are mediated by specialized domains such as the well-characterized Src homology SH2 and SH3 motifs. Using yeast three-hybrid technology, we have identified a novel adapter protein, expressed predominantly in T lymphocytes, that associates with the activated form of the costimulatory receptor, CD28. The protein is a member of the Grb2 family of adapter proteins and contains an SH3-SH2-SH3 domain structure. A unique glutamine/proline-rich domain (insert domain) of unknown function is situated between the SH2 and N-terminal SH3 domains. We term this protein GRID for Grb2-related protein with insert domain. GRID coimmunoprecipitates with CD28 from Jurkat cell lysates following activation of CD28. Using mutants of CD28 and GRID, we demonstrate that interaction between the proteins is dependent on phosphorylation of CD28 at tyrosine 173 and integrity of the GRID SH2 domain, although there are also subsidiary stabilizing contacts between the PXXP motifs of CD28 and the GRID C-terminal SH3 domain. In addition to CD28, GRID interacts with a number of other T cell signaling proteins, including SLP-76 (SH2 domain-containing leukocyte protein of 76 kDa), p62dok, and RACK-1 (receptor for activated protein kinase C-1). These findings suggest that GRID functions as an adapter protein in the CD28-mediated costimulatory pathway in T cells.
Definition of Minimal Domains of Interaction Within the Recombination-Activating Genes 1 and 2 Recombinase Complex
Authors: Aidinis Vassilis , Dias Dora C. , Gomez Carlos A. , Bhattacharyya Debika , Spanopoulou Eugenia , Santagata Sandro
Published: April 2014

During V(D)J recombination, recognition and cleavage of the recombination signal sequences (RSSs) requires the coordinated action of the recombination-activating genes 1 and 2 (RAG1/RAG2) recombinase complex. In this report, we use deletion mapping and site-directed mutagenesis to determine the minimal domains critical for interaction between RAG1 and RAG2. We define the active core of RAG2 required for RSS cleavage as aa 1–371 and demonstrate that the C-terminal 57 aa of this core provide a dominant surface for RAG1 interaction. This region corresponds to the last of six predicted kelch repeat motifs that have been proposed by sequence analysis to fold RAG2 into a six-bladed β-propeller structure. Residue W317 within this sixth repeat is shown to be critical for mediating contact with RAG1 and concurrently for stabilizing binding and directing cleavage of the RSS. We also show that zinc finger B (aa 727–750) of RAG1 provides a dominant interaction domain for recruiting RAG2. In all, the data support a model of RAG2 as a multimodular protein that utilizes one of its six faces for establishing productive contacts with RAG1.
Structure of the Major Peanut Allergen Ara h 1 May Protect IgE-Binding Epitopes from Degradation
Authors: Maleki Soheila J. , Kopper Randall A. , Shin David S. , Park Chun-Wook , Compadre Cesar M. , Sampson Hugh , Burks A. Wesley , Bannon Gary A.
Published: April 2014

In the past decade, there has been an increase in allergic reactions to peanut proteins, sometimes resulting in fatal anaphylaxis. The development of improved methods for diagnosis and treatment of peanut allergies requires a better understanding of the structure of the allergens. Ara h 1, a major peanut allergen belonging to the vicilin family of seed storage proteins, is recognized by serum IgE from >90% of peanut-allergic patients. In this communication, Ara h 1 was shown to form a highly stable homotrimer. Hydrophobic interactions were determined to be the main molecular force holding monomers together. A molecular model of the Ara h 1 trimer was constructed to view the stabilizing hydrophobic residues in the three dimensional structure. Hydrophobic amino acids that contribute to trimer formation are at the distal ends of the three dimensional structure where monomer-monomer contacts occur. Coincidentally, the majority of the IgE-binding epitopes are also located in this region, suggesting that they may be protected from digestion by the monomer-monomer contacts. On incubation of Ara h 1 with digestive enzymes, various protease-resistant fragments containing IgE-binding sites were identified. The highly stable nature of the Ara h 1 trimer, the presence of digestion resistant fragments, and the strategic location of the IgE-binding epitopes indicate that the quaternary structure of a protein may play a significant role in overall allergenicity.
CD40 Ligand (CD154) Enhances the Th1 and Antibody Responses to Respiratory Syncytial Virus in the BALB/c Mouse
Authors: Tripp Ralph A. , Jones Les , Anderson Larry J. , Brown Michael P.
Published: April 2014

CD40 ligand (CD40L) is a cell surface costimulatory molecule expressed mainly by activated T cells. CD40L is critically important for T-B cell and T cell-dendritic cell interactions. CD40L expression promotes Th1 cytokine responses to protein Ags and is responsible for Ig isotype switching in B cells. Respiratory syncytial virus (RSV) is an important pathogen of young children and the elderly, which causes bronchiolitis and pneumonia. Studies of mice infected with RSV suggest that a Th2 cytokine response may be responsible for enhanced pulmonary disease. To investigate the effect CD40L has on RSV immunity, mice were infected simultaneously with RSV and either an empty control adenovirus vector or one expressing CD40L or were coimmunized with plasmid DNA vectors expressing CD40L and RSV F and/or G proteins and subsequently challenged with RSV. The kinetics of the intracellular and secreted cytokine responses, the cytotoxic T lymphocyte precursor frequency, NO levels in lung lavage, rates of virus clearance, and anti-RSV Ab titers were determined. These studies show that coincident expression of CD40L enhances the Th1 (IL-2 and IFN-γ) cytokine responses, increases the expression of TNF-α and NO, accelerates virus clearance, and increases the anti-F and anti-G Ab responses. These data suggest that CD40L may have the adjuvant properties needed to optimize the safety and efficacy of RSV vaccines.
Human Blood Monocytes Interact with Type I Collagen Through αxβ2 Integrin (CD11c-CD18, gp150-95)
Authors: Garnotel Roselyne , Rittié Laure , Poitevin Stéphane , Monboisse Jean-Claude , Nguyen Philippe , Potron Gérard , Maquart François-Xavier , Randoux Alain , Gillery Philippe
Published: April 2014

Human blood monocytes are attracted into connective tissues during early steps of inflammation and wound healing, and locally interact with resident cells and extracellular matrix proteins. We studied the effects of type I collagen on monocyte adhesion and superoxide anion production, using human monocytes elutriated from peripheral blood and type I collagen obtained from rat tail tendon. Both acid-soluble and pepsin-digested type I collagens promoted the adhesion of monocytes, whereas only acid-soluble collagen with intact telopeptides induced the production of superoxide. Adhesion and activation of monocytes on acid-soluble type I collagen depended on the presence of divalent cations. mAbs directed against integrin subunits CD11c and CD18 specifically inhibited adhesion and activation of monocytes on type I collagen. Protein membrane extracts obtained from monocytes were submitted to affinity chromatography on collagen I-Sepharose 4B, and analyzed by Western blotting using specific anti-integrin subunit Abs. In the case of both acid-soluble and pepsin-digested collagens, two bands were revealed with mAbs against CD11c and CD18 integrin subunits. Our results demonstrate that monocytes interact with type I collagen through CD11c-CD18 (αxβ2) integrins, which promote their adhesion and activation. For monocyte activation, specific domains of the type I collagen telopeptides are necessary. Interactions between monocytes and collagen are most likely involved in the cascade of events that characterize the initial phases of inflammation.
Expression of CXCR4 in Eosinophils: Functional Analyses and Cytokine-Mediated Regulation
Authors: Nagase Hiroyuki , Miyamasu Misato , Yamaguchi Masao , Fujisawa Takao , Ohta Ken , Yamamoto Kazuhiko , Morita Yutaka , Hirai Koichi
Published: April 2014

We examined the expression of transcripts of a panel of chemokine receptors in human eosinophils and found intense constitutive expression of CXCR4 mRNA. Although surface CXCR4 protein was hardly detectable in the peripheral blood or freshly isolated eosinophils, surface expression of CXCR4 became gradually apparent during incubation at 37°C. In contrast, the level of CCR3 expression was virtually unchanged during the incubation. Stromal cell-derived factor-1α (SDF-1α), the natural ligand of CXCR4, elicited an apparent Ca2+ influx in these cells and induced a strong migratory response comparable to that by eotaxin. The surface expression of CXCR4 in eosinophils was up-regulated by IFN-γ, TNF-α, and TGF-β while it was down-regulated by IL-4 and eosinophil-directed hemopoietins such as IL-5. The CXCR4 expression did not always parallel the apoptotic changes in cytokine-treated eosinophils. In contrast to IL-4 and IFN-γ, IL-5 potently reduced the level of CXCR4 mRNA. It seems unlikely that CXCR4 is fundamentally involved in the pathogenesis of allergic disorders by inducing the migration of eosinophils toward inflammatory sites, because a Th2-dominant state down-regulates eosinophil CXCR4 expression. However, CXCR4 may affect the size of the mobilizable pool by holding eosinophils at noninflamed tissues. Th2-dominant state may favor the liberation of eosinophils by down-regulating CXCR4 expression. The interplay between CXCR4 and SDF-1α in eosinophils potentially plays an important role in the accumulation of these cells at the allergic inflammatory sites.
Th2 Cell Membrane Factors in Association with IL-4 Enhance Matrix Metalloproteinase-1 (MMP-1) While Decreasing MMP-9 Production by Granulocyte-Macrophage Colony-Stimulating Factor-Differentiated Human Monocytes
Authors: Chizzolini Carlo , Rezzonico Roger , De Luca Carmelina , Burger Danielle , Dayer Jean-Michel
Published: April 2014

Monocytes/macrophages are directly involved in tissue remodeling and tissue destruction through the release of matrix metalloproteinases (MMP). In the present study, we examined the effect mediated by contact of polarized Th cells with mononuclear phagocytes on the production of MMP-1, MMP-9, and their inhibitor. Plasma cell membranes from Ag-activated Th1 and Th2 cells were potent inducers of MMP-1 production by THP-1 cells. Cell membrane-associated TNF was found to be only partially involved in MMP-1 induction by both Th1 and Th2 cells. In Th2 cells exclusively, membrane-associated IL-4 induced MMP-1 production by THP-1 cells. This membrane-associated IL-4 effect was additive to that of TNF and was specifically observed on MMP-1 as MMP-9 production was concomitantly inhibited. Similarly, soluble IL-4 induced THP-1 cells to produce MMP-1, its effect proving additive to that of soluble TNF and to that of cell membranes of mitogen-activated HUT-78 cells. Its activity was blocked by IL-4 neutralization, and was unaffected by the presence of indomethacin. These effects on THP-1 cells were observed at protein and mRNA levels. Although inhibitory on freshly isolated peripheral blood monocytes, soluble IL-4 enhanced T cell-induced MMP-1 and inhibited MMP-9 production both at protein and mRNA levels in monocytes cultured for 7 days in the presence of GM-CSF. Thus, in contrast with previously reported effects, Th2 and IL-4 specifically induce MMP-1 production by mononuclear phagocytes at various stages of differentiation. This IL-4 activity may be relevant to pathological conditions dominated by Th2 inflammatory responses, resulting in tissue remodeling and destruction.
NF-κB Regulates VCAM-1 Expression on Fibroblast-Like Synoviocytes
Authors: Li Ping , Sanz Iñaki , O’Keefe Regis J. , Schwarz Edward M.
Published: April 2014

Expression of VCAM-1 on synovial fibroblasts is a clinical hallmark of rheumatoid arthritis. The interaction of VCAM-1 and its integrin receptor very late Ag-4 is believed to be critically involved in the recruitment and retention of immune cells in the inflamed joints. To study the regulation of VCAM-1 in synovial fibroblasts, fibroblast-like synoviocytes (FLS) were isolated from the knee joints of normal mice and passaged repeatedly to obtain a homogeneous cell population. We have found that VCAM-1 is constitutively expressed on mouse FLS (mFLS) and that its surface expression is further increased after exposure to TNF-α. Nuclear translocation of transcription factor NF-κB including P50/P50 homodimer and P65/P50 heterodimer was activated by TNF-α treatment. In mFLS stably expressing a dominant-negative mutant of the inhibitory protein I-κBα- (mI-κB), which does not undergo proteolytic degradation, NF-κB remains in the cytosol and its activation in response to TNF-α is abolished. VCAM-1 protein expression after TNF-α stimulation was blocked in cells expressing the mI-κB. This effect is likely due to the loss of NF-κB-mediated transcription of VCAM-1, because the 5-fold increase in mRNA levels in response to TNF-α is absent in the mutant cells. To confirm these findings, we transduced mFLS with an adenoviral vector containing the mI-κB transgene. VCAM-1 expression was also blocked by mI-κB in this system, whereas cells transduced with a control adenoviral vector remained responsive to TNF-α. These results indicate that NF-κB mediates TNF-α-induced VCAM-1 expression on mFLS.
Differential Expression and Regulation of Toll-Like Receptors (TLR) in Human Leukocytes: Selective Expression of TLR3 in Dendritic Cells
Authors: Muzio Marta , Bosisio Daniela , Polentarutti Nadia , D’amico Giovanna , Stoppacciaro Antonella , Mancinelli Roberta , van’t Veer Cornelis , Penton-Rol Giselle , Ruco Luigi P. , Allavena Paola , Mantovani Alberto
Published: April 2014

Members of the Toll-like receptor (TLR) family probably play a fundamental role in pathogen recognition and activation of innate immunity. The present study used a systematic approach to analyze how different human leukocyte populations express specific transcripts for the first five characterized TLR family members. TLR1 was expressed in all leukocytes examined, including monocytes, polymorphonuclear leukocytes, T and B cells, and NK cells. In contrast TLR2, TLR4, and TLR5 were expressed in myelomonocytic elements. Exposure to bacterial products, such as LPS or lipoarabinomannan, or to proinflammatory cytokines increased TLR4 expression in monocytes and polymorphonuclear leukocytes, whereas IL-10 blocked this effect. TLR3 was only expressed in human dendritic cells (DC) wherein maturation induced by bacterial products or cytokines was associated with reduced expression. TLR3 mRNA expression was detected by in situ hybridization in DC and lymph nodes. These results demonstrate that TLR1 through TLR5 mRNAs are differentially expressed and regulated in human leukocytes. In particular, expression of TLR3 transcripts is restricted to DC that are the only elements which express the full TLR repertoire. These data suggest that TLR can be classified based on expression pattern as ubiquitous (TLR1), restricted (TLR2, TLR4, and TLR5 in myelomonocytic cells), and specific (TLR3 in DC) molecules.
Simian Immunodeficiency Virus (SIV)-Specific CTL Are Present in Large Numbers in Livers of SIV-Infected Rhesus Monkeys
Authors: Schmitz Jörn E. , Kuroda Marcelo J. , Veazey Ronald S. , Seth Aruna , Taylor Wesley M. , Nickerson Christine E. , Lifton Michelle A. , Dailey Peter J. , Forman Meryl A. , Racz Paul , Tenner-Racz Klara , Letvin Norman L.
Published: April 2014

The immunopathogenesis of AIDS-associated hepatitis was explored in the SIV/rhesus monkey model. The livers of SIV-infected monkeys showed a mild hepatitis, with a predominantly CD8+ T lymphocyte infiltration in the periportal fields and sinusoids. These liver-associated CD8+ T cells were comprised of a high percentage of SIV-specific CTL as defined by MHC class I/Gag peptide tetramer binding and Gag peptide epitope-specific lytic activity. There was insufficient viral replication in these livers to account for attracting this large number of functional virus-specific CTL to the liver. There was also no evidence that the predominant population of CTL were functionally end-stage cells trapped in the liver and destined to undergo apoptotic cell death in that organ. Interestingly, we noted that liver tetramer-binding cells showed an increased expression of CD62L, an adhesion molecule usually only rarely expressed on tetramer-binding cells. This observation suggests that the expression of specific adhesion molecules by CTL might facilitate the capture of these cells in the liver. These results demonstrate that functional SIV-specific CD8+ T cells are present in large numbers in the liver of chronically SIV-infected monkeys. Thus, the liver may be a trap for virus-specific cytotoxic T cells.
Novel Protein Transfection of Primary Rat Cortical Neurons Using an Antibody That Penetrates Living Cells
Authors: Weisbart Richard H. , Baldwin Roger , Huh Brian , Zack Debra Jeske , Nishimura Robert
Published: April 2014

An Ab-based system to deliver functional proteins into neurons was developed using the murine mAb, mAb 3E10. This was achieved by covalently conjugating catalase to the Ab so that the conjugate retained high activity for the degradation of hydrogen peroxide. Three-dimensional fluorescence microscopy was used to demonstrate penetration of the Ab into the nucleus of living primary cortical neurons. The Ab conjugate localized in both the cytoplasm and nucleus. Retention of catalase activity after penetration and distribution of conjugate was demonstrated by reduction in cell death following exposure of treated neurons to hydrogen peroxide. These studies illustrate the potential of this method for the intracellular delivery of therapeutic proteins.
Costimulation by B7-1 and B7-2 Is Required for Autoimmune Disease in MRL-FaslprMice
Authors: Kinoshita Koji , Tesch Greg , Schwarting Andreas , Maron Ruth , Sharpe Arlene H. , Kelley Vicki Rubin
Published: April 2014

Autoimmune lupus nephritis is dependent on infiltrating autoreactive leukocytes and Igs. B7 costimulatory molecules (B7-1 and B7-2) provide signals essential for T cell activation and Ig class switching. In MRL-Faslpr mice, a model of human lupus, although multiple tissues are targeted for autoimmune injury, nephritis is fatal. We identified intrarenal B7-1 and B7-2 expression, restricted to kidney-infiltrating leukocytes, before and increasing with progressive nephritis in MRL-Faslpr mice. Thus, we hypothesized that the B7 pathway is required for autoimmune disease in MRL-Faslpr mice. To investigate the role of B7 costimulatory molecules in this autoimmune disease, we generated a MRL-Faslpr strain deficient in B7-1 and B7-2. Strikingly, MRL-Faslpr mice lacking both B7 costimulators do not develop kidney (glomerular, tubular, interstitial, vascular) pathology, or proteinuria, and survive far longer. Intrarenal downstream effector transcripts (IFN-γ, IL-12, monocyte chemoattractant protein-1, CSF-1) linked to nephritis remained at normal levels compared with wild-type mice. Skin lesions and lymphoid enlargement characteristic of MRL-Faslpr mice were diminished in B7-1/B7-2-deficient MRL-Faslpr mice. B7-1/B7-2-deficient MRL-Faslpr mice did not develop leukocytic infiltrates, elevated serum IgG and isotypes (G1,G2b,G3), autoantibodies, and intrarenal IgG deposits. Our findings demonstrate that B7-1 and B7-2 costimulatory pathways are critical to the pathogenesis of autoimmune lupus.
Exceptional Resistance of Human H2 Glioblastoma Cells to Complement-Mediated Killing by Expression and Utilization of Factor H and Factor H-Like Protein 1
Authors: Junnikkala S. , Jokiranta T. S. , Friese M. A. , Jarva H. , Zipfel P. F. , Meri S.
Published: April 2014

Of over 20 nucleated cell lines we have examined to date, human H2 glioblastoma cells have turned out to be the most resistant to complement-mediated cytolysis in vitro. H2 cells expressed strongly the membrane attack complex inhibitor protectin (CD59), moderately CD46 (membrane cofactor protein) and CD55 (decay-accelerating factor), but no CD35 (complement receptor 1). When treated with a polyclonal anti-H2 Ab, anti-CD59 mAb, and normal human serum, only 5% of H2 cells became killed. Under the same conditions, 70% of endothelial-like EA.hy 926 cells and 40% of U251 control glioma cells were killed. A combined neutralization of CD46, CD55, and CD59 increased H2 lysis only minimally, demonstrating that these complement regulators are not enough to account for the resistance of H2 cells. After treatment with Abs and serum, less C5b-9 was deposited on H2 than on U251 and EA.hy 926 cell lines. A reason for the exceptional resistance of H2 cells was revealed when RT-PCR and protein biochemical methods showed that the H2 cells, unlike the other cell lines tested, actively produced the soluble complement inhibitors factor H and factor H-like protein 1. H2 cells were also capable of binding human factor H from the fluid phase to their cell surface and promoted the cleavage of C3b to its inactive form iC3b more efficiently than U251 and EA.hy 926 cells. In accordance, anti-factor H mAbs enhanced killing of H2 glioblastoma cells. Taken together, our results show that production and binding of factor H and factor H-like protein 1 is a novel mechanism that these malignant cells utilize to escape complement-mediated killing.
Altered Composition of the Immunological Synapse in an Anergic, Age-Dependent Memory T Cell Subset
Authors: Eisenbraun Michael D. , Tamir Ami , Miller Richard A.
Published: April 2014

In young mice, memory CD4 T lymphocytes with high P-glycoprotein activity (P-gphigh) are unresponsive to TCR stimulation in vitro but can be activated by PMA plus ionomycin. The proportion of these hyporesponsive cells increases considerably with age. The earliest events in T cell activation were studied in P-gphigh and P-gplow CD4 memory cells at the single-cell level using confocal immunofluorescence methods. Recruitment of both linker for activation of T cells (LAT) and protein kinase C-θ to the immunological synapse, i.e., the site of T cell interaction with stimulator cells, was greatly impaired in P-gphigh cells from both young and old mice. Translocation of NF-AT to the nucleus, CD69 expression, and proliferative capacity were also diminished to a similar extent in P-gphigh cells under the same activation conditions. In contrast, movement of c-Cbl to the synapse region occurred in a high proportion of CD4 memory T cells regardless of P-gp subset or age. Moreover, although P-gplow cells frequently recruited both c-Cbl and LAT to the APC synapse, cells in the less responsive P-gphigh subset frequently relocated c-Cbl, but not LAT, to the interface region. In some systems, c-Cbl can act as a negative regulator of receptor-dependent tyrosine kinases, and alterations of c-Cbl to LAT ratios in the P-gphigh subset may thus contribute to the hyporesponsiveness of this age-dependent, anergic memory cell population.
Immunodominance Among EBV-Derived Epitopes Restricted by HLA-B27 Does Not Correlate with Epitope Abundance in EBV-Transformed B-Lymphoblastoid Cell Lines
Authors: Crotzer Victoria L. , Christian Robert E. , Brooks Jill M. , Shabanowitz Jeffrey , Settlage Robert E. , Marto Jarrod A. , White Forest M. , Rickinson Alan B. , Hunt Donald F. , Engelhard Victor H.
Published: April 2014

Using synthetic peptides, the HLA-B27-restricted CTL response to EBV in asymptomatic virus carriers has been mapped to four epitope regions in EBV latent cycle Ags. One of these peptide-defined epitopes (RRIYDLIEL) tends to be immunodominant and is recognized in the context of all three B27 subtypes studied, B*2702, B*2704, and B*2705. The other peptide-defined epitopes induce responses only in the context of one subtype, the immunogenic combinations being RRARSLSAERY/B*2702, RRRWRRLTV/B*2704, and FRKAQIQGL/B*2705. We used immunoaffinity chromatography to isolate the naturally presented viral peptides associated with these MHC class I molecules on the surface of EBV-transformed B-LCL. Using CTL reconstitution assays in conjunction with mass spectrometry, we established that the naturally processed and presented peptides are identical with the previously identified synthetic sequences. Despite the subtype-specific immunogenicity of three of the four epitopes, all four epitope peptides were found in association with each of the three different HLA-B27 subtypes. Indeed, those peptides that failed to induce a response in the context of a particular HLA-B27 subtype were frequently presented at greater abundance by that subtype than were the immunogenic peptides. Furthermore, among the peptides that did induce a response, immunodominance did not correlate with epitope abundance; in fact the immunodominant RRIYDLIEL epitope was least abundant, being present at less than one copy per cell. The relationship of this unexpected finding to the persistence of EBV is discussed.
Inhibition of Human NK Cell-Mediated Killing by CD1 Molecules
Authors: Carbone Ennio , Terrazzano Giuseppe , Melián Augustin , Zanzi Delia , Moretta Lorenzo , Porcelli Steven , Kärre Klas , Zappacosta Serafino
Published: April 2014

It is now well established that NK cells recognize classical and nonclassical MHC class I molecules and that such recognition typically results in the inhibition of target cell lysis. Given the known structural similarities between MHC class I and non-MHC-encoded CD1 molecules, we investigated the possibility that human CD1a, -b, and -c proteins might also function as specific target structures for NK cell receptors. Here we report that expression of CD1a, -b, or -c can partially inhibits target cell lysis by freshly isolated human NK cells and cultured NK lines. The inhibitory effects of CD1 molecules on NK cell could be shown upon expression of individual CD1 proteins in transfected NK-sensitive target cells, and these effects could be reversed by incubation of the target cells with mAbs specific for the expressed form of CD1. Inhibitory effects of CD1 expression on NK-mediated lysis could also be shown for cultured human dendritic cells, which represent a cell type that prominently expresses the various CD1 proteins in vivo. In addition, the bacterial glycolipid Ags known to be bound and presented by CD1 proteins could significantly augment the observed inhibitory effects on target cell lysis by NK cells.
The Selective Proteasome Inhibitors Lactacystin and Epoxomicin Can Be Used to Either Up- or Down-Regulate Antigen Presentation at Nontoxic Doses
Authors: Schwarz Katrin , de Giuli Rita , Schmidtke Gunter , Kostka Susanne , van den Broek Maries , Kim Kyung Bo , Crews Craig M. , Kraft Regine , Groettrup Marcus
Published: April 2014

The complete inhibition of proteasome activities interferes with the production of most MHC class I peptide ligands as well as with cellular proliferation and survival. In this study we have investigated how partial and selective inhibition of the chymotrypsin-like activity of the proteasome by the proteasome inhibitors lactacystin or epoxomicin would affect Ag presentation. At 0.5–1 μM lactacystin, the presentation of the lymphocytic choriomeningitis virus-derived epitopes NP118 and GP33 and the mouse CMV epitope pp89–168 were reduced and were further diminished in a dose-dependent manner with increasing concentrations. Presentation of the lymphocytic choriomeningitis virus-derived epitope GP276, in contrast, was markedly enhanced at low, but abrogated at higher, concentrations of either lactacystin or epoxomicin. The inhibitor-mediated effects were thus epitope specific and did not correlate with the degradation rates of the involved viral proteins. Although neither apoptosis induction nor interference with cellular proliferation was observed at 0.5–1 μM lactacystin in vivo, this concentration was sufficient to alter the fragmentation of polypeptides by the 20S proteasome in vitro. Our results indicate that partial and selective inhibition of proteasome activity in vivo is a valid approach to modulate Ag presentation, with potential applications for the treatment of autoimmune diseases and the prevention of transplant rejection.
M-1/M-2 Macrophages and the Th1/Th2 Paradigm
Authors: Mills Charles D. , Kincaid Kristi , Alt Jennifer M. , Heilman Michelle J. , Hill Annette M.
Published: April 2014

Evidence is provided that macrophages can make M-1 or M-2 responses. The concept of M-1/M-2 fomented from observations that macrophages from prototypical Th1 strains (C57BL/6, B10D2) are more easily activated to produce NO with either IFN-γ or LPS than macrophages from Th2 strains (BALB/c, DBA/2). In marked contrast, LPS stimulates Th2, but not Th1, macrophages to increase arginine metabolism to ornithine. Thus, M-1/M-2 does not simply describe activated or unactivated macrophages, but cells expressing distinct metabolic programs. Because NO inhibits cell division, while ornithine can stimulate cell division (via polyamines), these results also indicate that M-1 and M-2 responses can influence inflammatory reactions in opposite ways. Macrophage TGF-β1, which inhibits inducible NO synthase and stimulates arginase, appears to play an important role in regulating the balance between M-1 and M-2. M-1/M-2 phenotypes are independent of T or B lymphocytes because C57BL/6 and BALB/c NUDE or SCID macrophages also exhibit M-1/M-2. Indeed, M-1/M-2 proclivities are magnified in NUDE and SCID mice. Finally, C57BL/6 SCID macrophages cause CB6F1 lymphocytes to increase IFN-γ production, while BALB/c SCID macrophages increase TGF-β production. Together, the results indicate that M-1- or M-2-dominant macrophage responses can influence whether Th1/Th2 or other types of inflammatory responses occur.
TNF-α-Induced Secretion of C-C Chemokines Modulates C-C Chemokine Receptor 5 Expression on Peripheral Blood Lymphocytes
Authors: Hornung Felicita , Scala Giuseppe , Lenardo Michael J.
Published: April 2014

Peripheral blood lymphocytes express CCR5, a chemokine receptor for immune cell migration and calcium signaling that serves as an important coreceptor for the HIV. After in vitro stimulation, CCR5 expression is dramatically increased on mature T lymphocytes, especially on the CD45RO+ memory subset. In this study, we report that TNF-α delays the surface expression of CCR5 on PBLs after activation and diminishes CCR5 irrespective of its initial level. Functional loss of CCR5 is reflected in a decreased capability of the treated cells to migrate and signal calcium after MIP-1β stimulation. The effect is mediated via the p80 type II TNF receptor (TNFR2), which induces NF-κB among other factors, leading to an enhanced secretion of the chemokines macrophage-inflammatory protein-1α, macrophage-inflammatory protein-1β, and RANTES. Expression of these chemokines directly down-regulates CCR5. These findings reveal a new regulatory mechanism utilized by activated peripheral T cells to modulate their chemotaxis and potentially other functions mediated by CCR5, including the infection of T lymphocytes by macrophage-tropic HIV strains.
Gender-Dependent IL-12 Secretion by APC Is Regulated by IL-10
Authors: Wilcoxen Scott C. , Kirkman Erlinda , Dowdell Kennichi C. , Stohlman Stephen A.
Published: April 2014

Female SJL mice preferentially mount Th1-immune responses and are susceptible to the active induction of experimental allergic encephalomyelitis. By contrast, young adult male SJL are resistant to experimental allergic encephalomyelitis due to an APC-dependent induction of Th2 cells. The basis for this gender-dependent differential T cell induction was examined by analysis of macrophage APC cytokine secretion during T cell activation. APC derived from females secrete IL-12, but not IL-10, during T cell activation. By contrast, APC derived from males secrete IL-10, but not IL-12, during T cell activation. Activation of T cells with APC derived from the opposite sex demonstrated that these cytokines were derived from the respective APC populations. Furthermore, inhibition of IL-10, but not TGF-β, during T cell activation resulted in the secretion of IL-12 by male-derived APC. APC from naive male mice, in which IL-10 was reduced in vivo before isolation, also secrete IL-12, demonstrating altered APC cytokine secretion was due to an environment high in IL-10 before Ag encounter. Finally, APC derived from castrated male mice preferentially secrete IL-12 during T cell activation. These data demonstrate a link between gonadal hormones and APC activity and suggest that these hormones alter the APC, thereby influencing cytokine secretion during initial T cell activation.
Correlation of T Cell Independence of Antibody Responses with Antigen Dose Reaching Secondary Lymphoid Organs: Implications for Splenectomized Patients and Vaccine Design
Authors: Ochsenbein Adrian F. , Pinschewer Daniel D. , Odermatt Bernhard , Ciurea Adrian , Hengartner Hans , Zinkernagel Rolf M.
Published: April 2014

Many natural viral and bacterial pathogens activate B cells independently of Th cells (TI Ags). This study analyzed the characteristics of the activation of B cells after immunization with various forms of viral Ags using different immunization routes and found a decreasing dependence on T help with increasing amounts of Ag recruited to the spleen. Repetitive antigenic structure facilitated TI B cell responses if Ag was present in lymphoid organs. These results suggest that 1) Ag dose and localization in secondary lymphoid organs are the key for B cell activation in the absence of T help; 2) early TI Ab responses are crucial to protect against systemically spreading acute cytopathic infectious agents; and 3) there may be new rationales for improved vaccine design.
The Murine Chemokine CXCL11 (IFN-Inducible T Cell α Chemoattractant) Is an IFN-γ- and Lipopolysaccharide- Inducible Glucocorticoid-Attenuated Response Gene Expressed in Lung and Other Tissues During Endotoxemia
Authors: Widney Daniel P. , Xia Yu-Rong , Lusis Aldons J. , Smith Jeffrey B.
Published: April 2014

A new murine chemokine was identified in a search for glucocorticoid-attenuated response genes induced in the lung during endotoxemia. The first 73 residues of the predicted mature peptide are 71% identical and 93% similar to human CXCL11/IFN-inducible T cell α chemoattractant (I-TAC) (alias β-R1, H174, IFN-inducible protein 9 (IP-9), and SCYB9B). The murine chemokine has six additional residues at the carboxyl terminus not present in human I-TAC. Identification of this cDNA as murine CXCL11/I-TAC is supported by phylogenetic analysis and by radiation hybrid mapping of murine I-TAC (gene symbol Scyb11) to mouse chromosome 5 close to the genes for monokine induced by IFN-γ (MIG) and IP10. Murine I-TAC mRNA is induced in RAW 264.7 macrophages by IFN-γ or LPS and is weakly induced by IFN-αβ. IFN-γ induction of murine I-TAC is markedly enhanced by costimulation with LPS or IL-1β in RAW cells and by TNF-α in both RAW cells and Swiss 3T3 fibroblasts. Murine I-TAC is induced in multiple tissues during endoxemia, with strongest expression in lung, heart, small intestine, and kidney, a pattern of tissue expression different from those of MIG and IP10. Peak expression of I-TAC message is delayed compared with IP10, both in lung after i.v. LPS and in RAW 264.7 cells treated with LPS or with IFN-γ. Pretreatment with dexamethasone strongly attenuates both IFN-γ-induced I-TAC expression in RAW cells and endotoxemia-induced I-TAC expression in lung and small intestine. The structural and regulatory similarities of murine and human I-TAC suggest that mouse models will be useful for investigating the role of this chemokine in human biology and disease.
Modulation of HLA-G Antigens Expression by Human Cytomegalovirus: Specific Induction in Activated Macrophages Harboring Human Cytomegalovirus Infection
Authors: Onno Myriam , Pangault Céline , Le Friec Gaëlle , Guilloux Valérie , André Patrice , Fauchet Renée
Published: April 2014

After infection, human CMV (HCMV) establishes a latent and persistent infection in immature myeloid progenitors and peripheral blood monocytes. Completion of the HCMV life cycle is possible upon maturation of monocytes to tissue macrophages and under permissive circumstances, e.g., immunosuppression. We investigated the hypothesis that HLA-G molecules could be induced during HCMV reactivation in activated macrophages to favor virus dissemination. In this study, we provide evidence that HLA-G Ags are produced during viral reactivation in macrophages generated after allogeneic stimulation of HCMV latently infected monocytes. While HLA-G surface expression is up-regulated, classical MHC-I molecules are partially down-regulated by HCMV. In vivo, bronchoalveolar macrophages collected from patients suffering from acute HCMV pneumonitis also express HLA-G molecules. The direct correlation between HLA-G Ag induction and HCMV infection was confirmed in U-373 MG astrocytoma cells. Soluble HLA-G expression is stimulated upon HCMV infection, and this modulation depends on the cooperative action of the two immediate-early-1 pp72 and immediate-early-2 pp86 products. Because HLA-G transcription is active in macrophages and U-373 MG astrocytoma cells, it is likely that the modulation of HLA-G protein expression during HCMV replication occurs at a post-transcriptional level. Our data suggest that induction of HLA-G molecules could be an additional mechanism that helps HCMV to subvert host defenses.
Plasmid DNA Encoding IFN-α1 Antagonizes Herpes Simplex Virus Type 1 Ocular Infection Through CD4+ and CD8+ T Lymphocytes
Authors: Noisakran Sansanee , Carr Daniel J. J.
Published: April 2014

The present study was undertaken to further characterize the anti-viral efficacy of a plasmid DNA encoding IFN-α1 against ocular herpes simplex virus type 1 (HSV-1) infection. In mice ocularly treated with plasmid DNA encoding IFN-α1, the efficacy of the transgene was inversely proportional to the amount of virus used to infect the mice. Ocular treatment of mice with the IFN-α1 transgene was the only mucosal route tested that showed efficacy against ocular HSV-1 infection compared with vaginal or intranasal delivery. Mice treated with the plasmid DNA encoding IFN-α1 showed a significant reduction in viral Ag expression in the eyes and trigeminal ganglion that correlated with a reduction in immune cell infiltration into the cornea and iris on days 3 and 6 postinfection, as evidenced by immunohistochemical staining. Depleting mice of either CD4+ or CD8+ T lymphocytes completely blocked the resistance to herpes simplex virus type 1-induced mortality in mice treated with the IFN-α1 transgene. In the absence of infection, the application of naked DNA encoding IFN-α1 significantly increased the levels of IL-6- and IFN-γ-inducible protein 10 transcript expression in the corneas 24 h post-treatment. Expression of the plasmid construct following topical application in the eye included the rectus muscles proximal to the cornea as well as the spleen. Collectively, the protective efficacy of the IFN-α1 transgene against ocular HSV-1 infection is dependent upon the local or distal participation of CD4+ and CD8+ T lymphocytes early in the course of the infection, suggesting an indirect effect of the transgene against HSV-1-induced mortality.
EBV Suppresses Prostaglandin E2 Biosynthesis in Human Monocytes
Authors: Savard Martin , Bélanger Carole , Tremblay Michel J. , Dumais Nancy , Flamand Louis , Borgeat Pierre , Gosselin Jean
Published: April 2014

It is well known that EBV has developed strategies to evade immune surveillance. Previously, EBV was shown to bind specifically to monocytes and regulate expression of proinflammatory mediators such as IL-1, IL-6, TNF-α, and leukotrienes. EBV was also found to affect phagocytosis of monocytes. In this study, we show that in addition to these effects, EBV suppresses the biosynthesis of PGE2, a pleiotropic immunomodulatory molecule that is synthesized by the dioxygenation of arachidonic acid via the cyclooxygenase (COX) pathway. This down-regulation of PGE2 formation involved the inhibition of the inducible COX-2 isoform expression both at the transcriptional and translational levels, whereas expression of the constitutive COX-1 isoform was unaltered. Furthermore, exposure of monocytes to EBV was found to impact on the NF-κB activation pathway, which plays an essential role in the induction of COX-2 in monocytes. The inhibition of PGE2 biosynthesis was relieved when the experiments were conducted in presence of phosphonoacetic acid, an inhibitor of herpesviruses DNA polymerase, indicating that viral replication and/or neosynthesized viral proteins were involved in this process. Thus, inhibition of PGE2 biosynthesis in monocytes may represent an additional mechanism underlying EBV pathogenicity.