bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulation of Fas-Dependent Apoptosis: A Dynamic Process Controlling Both the Persistence and Death of CD4 Regulatory T Cells and Effector T Cells
Authors: Banz Alice , Pontoux Christiane , Papiernik Martine
Published: April 2014

We have previously shown that regulatory CD25+CD4+ T cells are resistant to clonal deletion induced by viral superantigen in vivo. In this work we report that isolated CD25+CD4+ T cells activated in vitro by anti-CD3 Ab are resistant to Fas-induced apoptosis, in contrast to their CD25−CD4+ counterparts. Resistance of CD25+CD4+ T cells to Fas-dependent activation-induced cell death is not linked to their inability to produce IL-2 or to their ability to produce IL-10. The sensitivity of both populations to Fas-induced apoptosis can be modulated in vitro by changing the CD25+CD4+:CD25−CD4+ T cell ratio. The sensitivity of CD25−CD4+ T cells to apoptosis can be reduced, while the sensitivity of CD25+CD4+ T cells can be enhanced. Modulation of Fas-dependent apoptosis is associated with changes in cytokine production. However, while CD25−CD4+ T cell apoptosis is highly dependent on IL-2 (production of which is inhibited by CD25+CD4+ T cells in coculture), modulation of CD25+CD4+ T cell apoptosis is IL-2 independent. Taken together, these results suggest that CD25+CD4+ and CD25−CD4+ T cell sensitivity to Fas-dependent apoptosis is dynamically modulated during immune responses; this modulation appears to help maintain a permanent population of regulatory T cells required to control effector T cells.
The B Cell Antigen Receptor Regulates the Transcriptional Activator β-Catenin Via Protein Kinase C-Mediated Inhibition of Glycogen Synthase Kinase-3
Authors: Christian Sherri L. , Sims Peter V. , Gold Michael R.
Published: April 2014

β-Catenin is a transcriptional activator that is regulated by glycogen synthase kinase-3 (GSK-3). GSK-3 is constitutively active in unstimulated cells where it phosphorylates β-catenin, targeting β-catenin for rapid degradation. Receptor-induced inhibition of GSK-3 allows β-catenin to accumulate in the cytoplasm and then translocate to the nucleus where it promotes the transcription of genes such as c-myc and cyclin D1. Wnt hormones, the best known regulators of β-catenin, inhibit GSK-3 via the Disheveled protein. However, GSK-3 is also inhibited when it is phosphorylated by Akt, a downstream target of phosphatidylinositol 3-kinase (PI3K). We have previously shown that B cell Ag receptor (BCR) signaling leads to activation of PI3K and Akt as well as inhibition of GSK-3. Therefore, we hypothesized that BCR engagement would induce the accumulation of β-catenin via a PI3K/Akt/GSK-3 pathway. We now show that BCR ligation causes an increase in the level of β-catenin in the nuclear fraction of B cells as well as an increase in β-catenin-dependent transcription. Direct inhibition of GSK-3 by LiCl also increased β-catenin levels in B cells. This suggests that GSK-3 keeps β-catenin levels low in unstimulated B cells and that BCR-induced inhibition of GSK-3 allows the accumulation of β-catenin. Surprisingly, we found that the BCR-induced phosphorylation of GSK-3 on its negative regulatory sites, as well as the subsequent up-regulation of β-catenin, was not mediated by Akt but by the phospholipase C-dependent activation of protein kinase C. Thus, the BCR regulates β-catenin levels via a phospholipase C/protein kinase C/GSK-3 pathway.
Rapid Chromatin Remodeling of Toll-Like Receptor 2 Promoter During Infection of Macrophages withMycobacterium avium
Authors: Wang Tianyi , Lafuse William P. , Takeda Kiyoshi , Akira Shizuo , Zwilling Bruce S.
Published: April 2014

We have previously reported that NF-κB and stimulating factor 1 elements within the proximal mouse Toll-like receptor 2 (TLR2) promoter region are required for the transcriptional activation of TLR2 expression following infection with Mycobacterium avium. In the present study, we found that a rapid increase in both DNase I sensitivity and restriction enzyme accessibility at the TLR2 promoter region occurred following infection with M. avium. Increase in restriction enzyme accessibility at the TLR2 promoter region covering the NF-κB and stimulating factor 1 elements was associated with the induction of TLR2 expression at the mRNA level. Furthermore, the increase in restriction enzyme accessibility at the TLR2 promoter region did not appear to result from binding of NF-κB, but rather depended on a TLR2-myeloid differentiation factor 88 signaling pathway. Together our results indicate that chromatin remodeling occurs at TLR2 promoter region following infection with M. avium, allowing the access of transcription factors to initiate the transcription of TLR2.
Effect of Environmental Antigens on the Ig Diversification and the Selection of Productive V-J Joints in the Bursa
Authors: Arakawa Hiroshi , Kuma Kei-ichi , Yasuda Masahiro , Ekino Shigeo , Shimizu Akira , Yamagishi Hideo
Published: April 2014

In chickens, a single set of unique functional segments of both Ig H and L chain genes is rearranged during early embryogenesis to generate a pool of B cell progenitors that will be diversified in the bursa by gene conversion, forming the preimmune repertoire. After hatching, bursal cells are exposed to environmental Ags in the bursal lumen. We prepared B cells from each single bursal follicle and used PCR-directed Ig L chain gene analysis to study the differentiation of B cells and the effect of antigenic stimulation from the bursal lumen on the neonatal chicken B cell repertoire formation. Selective amplification of B cell clones with a productive V-J joint was observed during the late embryonic stage, possibly by the interaction with ligands expressed on the bursal stroma and further accelerated in the neonatal chicken. Administration of the artificial Ags into the bursal lumen before the isolation of bursa by bursal duct ligation in the embryo caused a significant increase in lymphocytes with a productive V-J joint in the neonatal chicken bursa compared with the isolated bursa. Intra- and interclonal diversity of a complementarity-determining region measured by an evolutionary distance increased during bursal development. Clonal diversification did not require stimulation by artificial Ags from the bursal lumen. Thus, the preimmune repertoire in the bursa is generated by gene conversion during Ag-independent B cell proliferation, and antigenic stimulation from the bursal epithelium to bursal B cells plays roles in the selection of clones with a productive V-J joint.
A Putative Silencer Element in the IL-5 Gene Recognized by Bcl6
Authors: Arima Masafumi , Toyama Hirochika , Ichii Hirohito , Kojima Satoko , Okada Seiji , Hatano Masahiko , Cheng Gang , Kubo Masato , Fukuda Takeshi , Tokuhisa Takeshi
Published: April 2014

The Bcl6 gene is ubiquitously expressed in adult murine tissues and its product functions as a sequence-specific transcriptional repressor. Bcl6-deficient mice displayed eosinophilic inflammation caused by overproduction of Th2 cytokines. The regulatory mechanism of those cytokine productions by Bcl6 is controversial. When CD4+ T cells from Bcl6-deficient and lck-Bcl6-transgenic mice were stimulated with anti-CD3 Abs, production of IL-5 among Th2 type cytokines was preferentially affected by the amount of Bcl6 in the T cells. We found a putative Bcl6-binding sequence (IL5BS) on the 3′ untranslated region in the murine and human IL-5 genes, and specific binding of Bcl6 protein to the sequence was confirmed by gel retardation assay and chromatin immunoprecipitation assay. The binding activity of endogenous Bcl6 was transiently diminished in Th2 but not in Th1 clones after anti-CD3 stimulation. The exogenous Bcl6 repressed expression of the reporter gene with the IL5BS in K562 cells and the repressor activity was lost by a point mutation of the IL5BS. Furthermore, the IL5BS was required for Bcl6 to repress expression of the IL-5 cDNA. Thus, the IL5BS may act as a silencer element for Bcl6 to repress expression of the IL-5 gene.
Immunogenically Fit Subunit Vaccine Components Via Epitope Discovery from Natural Peptide Libraries
Authors: Matthews Leslie J. , Davis Robert , Smith George P.
Published: April 2014

Antigenic peptides that bind pathogen-specific Abs are a potential source of subunit vaccine components. To be effective the peptides must be immunogenically fit: when used as immunogens they must elicit Abs that cross-react with native intact pathogen. In this study, antigenic peptides obtained from phage display libraries through epitope discovery were systematically examined for immunogenic fitness. Peptides selected from random peptide libraries, in which the phage-displayed peptides are encoded by synthetic degenerate oligonucleotides, had marginal immunogenic fitness. In contrast, 50% of the peptides selected from a natural peptide library, in which phage display segments of actual pathogen polypeptides, proved very successful. Epitope discovery from natural peptide libraries is a promising route to subunit vaccines.
Bivalent Ligands with Rigid Double-Stranded DNA Spacers Reveal Structural Constraints on Signaling by FcεRI
Authors: Paar Jodi M. , Harris Nancie T. , Holowka David , Baird Barbara
Published: April 2014

Degranulation of mast cells and basophils during the allergic response is initiated by Ag-induced cross-linking of cell surface IgE-FcεRI receptor complexes. To investigate how separation distances between cross-linked receptors affect the competency of signal transduction, we synthesized and characterized bivalent dinitrophenyl (DNP)-modified dsDNA oligomers with rigid spacing lengths of ∼40–100 Å. All of these bivalent ligands effectively bind and cross-link anti-DNP IgE with similar affinities in the nanomolar range. The 13-mer (dsDNA length of 44 Å), 15-mer (51 Å), and flexible 30-mer ligands stimulate similar amounts of cellular degranulation, about one-third of that with multivalent Ag, whereas the 20-mer (68 Å) ligand is less effective and the rigid 30-mer (102 Å) ligand is ineffective. Surprisingly, all stimulate tyrosine phosphorylation of FcεRI β, Syk, and linker for activation of T cells to similar extents as multivalent Ag at optimal ligand concentrations. The magnitudes of Ca2+ responses stimulated by these bivalent DNP-dsDNA ligands are small, implicating activation of Ca2+ mobilization by stimulated tyrosine phosphorylation as a limiting process. The results indicate that structural constraints on cross-linked IgE-FcεRI complexes imposed by these rigid DNP-dsDNA ligands prevent robust activation of signaling immediately downstream of early tyrosine phosphorylation events. To account for these results, we propose that activation of a key downstream target is limited by the spacing between cross-linked, phosphorylated receptors and their associated components.
A Role for Inducible Costimulator Protein in the CD28- Independent Mechanism of Resistance to Toxoplasma gondii
Authors: Villegas Eric N. , Lieberman Linda A. , Mason Nicola , Blass Sarah L. , Zediak Valerie P. , Peach Robert , Horan Tom , Yoshinaga Steve , Hunter Christopher A.
Published: April 2014

Long-term resistance to Toxoplasma gondii is dependent on the development of parasite-specific T cells that produce IFN-γ. CD28 is a costimulatory molecule important for optimal activation of T cells, but CD28−/− mice are resistant to T. gondii, demonstrating that CD28-independent mechanisms regulate T cell responses during toxoplasmosis. The identification of the B7-related protein 1/inducible costimulator protein (ICOS) pathway and its ability to regulate the production of IFN-γ suggested that this pathway may be involved in the CD28-independent activation of T cells required for resistance to T. gondii. In support of this hypothesis, infection of wild-type or CD28−/− mice with T. gondii resulted in the increased expression of ICOS by activated CD4+ and CD8+ T cells. In addition, both costimulatory pathways contributed to the in vitro production of IFN-γ by parasite-specific T cells and when both pathways were blocked, there was an additive effect that resulted in almost complete inhibition of IFN-γ production. Although in vivo blockade of the ICOS costimulatory pathway did not result in the early mortality of wild-type mice infected with T. gondii, it did lead to increased susceptibility of CD28−/− mice to T. gondi associated with reduced serum levels of IFN-γ, increased parasite burden, and increased mortality compared with the control group. Together, these results identify a critical role for ICOS in the protective Th1-type response required for resistance to T. gondii and suggest that ICOS and CD28 are parallel costimulatory pathways, either of which is sufficient to mediate resistance to this intracellular pathogen.
Identification of T Cell Epitopes on the 33-kDa Fragment of Plasmodium yoelii Merozoite Surface Protein 1 and Their Antibody-Independent Protective Role in Immunity to Blood Stage Malaria
Authors: Wipasa Jiraprapa , Hirunpetcharat Chakrit , Mahakunkijcharoen Yuvadee , Xu Huji , Elliott Salenna , Good Michael F.
Published: April 2014

Merozoite surface protein 1 (MSP1) of malaria parasites undergoes proteolytic processing at least twice before invasion into a new RBC. The 42-kDa fragment, a product of primary processing, is cleaved by proteolytic enzymes giving rise to MSP133, which is shed from the merozoite surface, and MSP119, which is the only fragment carried into a new RBC. In this study, we have identified T cell epitopes on MSP133 of Plasmodium yoelii and have examined their function in immunity to blood stage malaria. Peptides 20 aa in length, spanning the length of MSP133 and overlapping each other by 10 aa, were analyzed for their ability to induce T cell proliferation in immunized BALB/c and C57BL/6 mice. Multiple epitopes were recognized by these two strains of mice. Effector functions of the dominant epitopes were then investigated. Peptides Cm15 and Cm21 were of particular interest as they were able to induce effector T cells capable of delaying growth of lethal P. yoelii YM following adoptive transfer into immunodeficient mice without inducing detectable Ab responses. Homologs of these epitopes could be candidates for inclusion in a subunit vaccine.
Segregation of B and T Cell Epitopes of Treponema pallidum Repeat Protein K to Variable and Conserved Regions During Experimental Syphilis Infection
Authors: Morgan Cecilia A. , Molini Barbara J. , Lukehart Sheila A. , Van Voorhis Wesley C.
Published: April 2014

Robust immune responses clear millions of treponemes to resolve lesions of primary and secondary syphilis, but cannot clear the treponemes that lead to debilitating and sometimes fatal tertiary syphilis. It is also known that the rabbit model and humans can be reinfected with heterologous isolates. How some treponemes are able to escape the immune system is unknown. In our laboratories rabbits immunized with the Seattle Nichols strain Treponema pallidum repeat protein K (TprK) were previously shown to have attenuated lesion development following challenge. In other isolates, TprK was shown to have seven discrete variable regions, with sequence variation among and within isolates. Using overlapping synthetic 20-aa peptides, we demonstrate that during experimental infection with the Nichols strain, the T cell responses are directed to conserved regions, while the Ab responses are directed primarily to variable regions. Abs from rabbits immunized with recombinant TprK recognized conserved and variable regions, suggesting that the conserved regions are inherently as immunogenic as the variable regions. TprK variability may allow some treponemes to escape recognition from Abs. The variable region heterogeneity may help explain the lack of protection against heterologous isolates.
Heat Shock Protein 70 Is a Potential Virulence Factor in MurineToxoplasmaInfection Via Immunomodulation of Host NF-κB and Nitric Oxide
Authors: Dobbin Caroline A. , Smith Nicholas C. , Johnson Alan M.
Published: April 2014

We propose that the 70-kDa heat shock protein (HSP70) protects virulent Toxoplasma gondii from the effects of the host by immunomodulation. This hypothesis was tested using quercetin and antisense oligonucleotides targeting the start codon of the virulent T. gondii HSP70 gene. Oligonucleotides were transiently transfected into two virulent (RH, ENT) and two avirulent (ME49, C) strains of T. gondii, significantly reducing HSP70 expression in treated parasites. Virulent parasites with reduced HSP70 expression displayed reduced proliferation in vivo, as measured by the number of tachyzoites present in spleens of infected mice. They also exhibited an enhanced rate of conversion from tachyzoites to bradyzoites in vitro. Our results implicate HSP70 as a means by which virulent strains of T. gondii evade host proinflammatory responses: when RAW 264.7 cells were exposed to parasites with reduced HSP70 expression, differential expression of inducible NO synthase (iNOS) and cell NO production were observed between infections with normal and HSP70-deficient T. gondii. iNOS message levels were significantly increased when host cells were infected with HSP70 reduced virulent tachyzoites and HSP70-related inhibition of iNOS transcription resulted in altered host NO production by virulent T. gondii infection. Virulent parasites expressing reduced levels of HSP70 initiated significantly more NF-κB activation in host splenocytes than infections with untreated parasites. Neither proliferative ability nor conversion from tachyzoites to bradyzoites was affected by lack of HSP70 in avirulent strains of T. gondii. Furthermore, avirulent T. gondii strains induced high levels of host iNOS expression and NO production, regardless of HSP70 expression in these parasites, and inhibition of HSP70 had no significant effects on translocation of NF-κB to the nucleus. Therefore, the 70-kDa parasite stress protein may be part of an important survival strategy by which virulent strains down-regulate host parasiticidal mechanisms.
Differential Effects of Ebselen on Neutrophil Recruitment, Chemokine, and Inflammatory Mediator Expression in a Rat Model of Lipopolysaccharide-Induced Pulmonary Inflammation
Authors: Haddad El-Bdaoui , McCluskie Kerryn , Birrell Mark A. , Dabrowski Dominika , Pecoraro Michela , Underwood Steve , Chen Bei , De Sanctis George T. , Webber Steve E. , Foster Martyn L. , Belvisi Maria G.
Published: April 2014

We postulated that the seleno-organic compound ebselen would attenuate neutrophil recruitment and activation after aerosolized challenge with endotoxin (LPS) through its effect as an antioxidant and inhibitor of gene activation. Rats were given ebselen (1–100 mg/kg i.p.) followed by aerosolized LPS exposure (0.3 mg/ml for 30 min). Airway inflammatory indices were measured 4 h postchallenge. Bronchoalveolar lavage (BAL) fluid cellularity and myeloperoxidase activity were used as a measure of neutrophil recruitment and activation. RT-PCR analysis was performed in lung tissue to assess gene expression of TNF-α, cytokine-induced neutrophil chemoattractant-1 (CINC-1), macrophage-inflammatory protein-2 (MIP-2), ICAM-1, IL-10, and inducible NO synthase. Protein levels in lung and BAL were also determined by ELISA. Ebselen pretreatment inhibited neutrophil influx and activation as assessed by BAL fluid cellularity and myeloperoxidase activity in cell-free BAL and BAL cell homogenates. This protective effect was accompanied by a significant reduction in lung and BAL fluid TNF-α and IL-1β protein and/or mRNA levels. Ebselen pretreatment also prevented lung ICAM-1 mRNA up-regulation in response to airway challenge with LPS. This was not a global effect of ebselen on LPS-induced gene expression, because the rise in lung and BAL CINC-1 and MIP-2 protein levels were unaffected as were lung mRNA expressions for CINC-1, MIP-2, IL-10, and inducible NO synthase. These data suggest that the anti-inflammatory properties of ebselen are achieved through an inhibition of lung ICAM-1 expression possibly through an inhibition of TNF-α and IL-1β, which are potent neutrophil recruiting mediators and effective inducers of ICAM-1 expression.
Cutting Edge: Thymocyte-Independent and Thymocyte-Dependent Phases of Epithelial Patterning in the Fetal Thymus
Authors: Klug David B. , Carter Carla , Gimenez-Conti Irma B. , Richie Ellen R.
Published: April 2014

Thymic epithelial cells (TECs) in adult mice have been classified into distinct subsets based on keratin expression profiles. To explore the emergence of TEC subsets during ontogeny, we analyzed keratin 8 and keratin 5 expression at several stages of fetal development in normal C57BL/6J mice. In addition, thymic epithelial development and compartmentalization were explored in recombination-activating gene 2/common cytokine receptor γ-chain-deficient and Ikaros-null mice that sustain early and profound blocks in thymocyte differentiation. The results demonstrate that initial patterning of the thymic epithelial compartment as defined by differential keratin expression does not depend on inductive signals from hematopoietic cells. However, thymocyte-derived signals are required during late fetal stages for continued development and maintenance of TEC subsets in the neonate and adult.
Severe Immunodeficiency Has Opposite Effects on Neuronal Survival in Glutamate-Susceptible and -Resistant Mice: Adverse Effect of B Cells
Authors: Schori Hadas , Lantner Frida , Shachar Idit , Schwartz Michal
Published: April 2014

The resistance of rats or mice to glutamate-induced toxicity depends on their ability to spontaneously manifest a T cell-dependent response to the insult. Survival of retinal ganglion cells (RGCs) exposed to glutamate in BALB/c SCID mice (a strain relatively resistant to glutamate toxicity) was significantly worse than in the wild type. In the susceptible C57BL/6J mouse strain, however, significantly more RGCs survived among SCID mutants than in the matched wild type. RGC survival in the SCID mutants of the two strains was similar. These results suggest 1) that immunodeficiency might be an advantage in strains incapable of spontaneously manifesting protective T cell-dependent immunity and 2) that B cells might be destructive in such cases. After exposure of RGCs to toxic glutamate concentrations in three variants of B cell-deficient C57BL/6J mice, namely muMT−/− (B cell knockout mice) and Ii−/− mice reconstituted with transgenically expressed low levels of Ii p31 isoforms (p31 mice) or Ii p41 isoforms (p41 mice), significantly more RGCs survived in these mice than in the wild type. The improved survival was diminished by replenishment of the B cell-deficient mice with B cells derived from the wild type. It thus seems that B cells have an adverse effect on neuronal recovery after injury, at least in a strain that is unable to spontaneously manifest a T cell-dependent protective mechanism. These findings have clear implications for the design of immune-based therapies for CNS injury.
Enforced Expression ofRunx2Perturbs T Cell Development at a Stage Coincident with β-Selection
Authors: Vaillant François , Blyth Karen , Andrew Linda , Neil James C. , Cameron Ewan R.
Published: April 2014

The development of T cells in the thymus is regulated by a series of stage-specific transcription factors. Deregulated expression of these factors can lead to alterations in thymocyte development with the production of aberrant cell subsets and predispose to tumor formation. The three genes of the Runx family are multilineage regulators of differentiation that have been reported to be expressed in the T cell lineage. However, their roles in thymocyte development and T cell function are largely unknown. While the Runx2/Cbfa1/AML3/Pebp2αa gene plays a primary role in osteogenesis and regulates a number of key bone regulatory genes, we show here that Runx2 is also expressed during the earliest phase of thymic development, in the double-negative subset. Furthermore, enforced expression of Runx2 in transgenic mice under the CD2 promoter was found to affect T cell development at a stage coincident with β-selection, resulting in an expansion of double-negative CD4 and CD8 immature single-positive cells. Unlike wild-type controls this preselection population (CD4−CD8+heat-stable Ag+TCR−) is in a nonproliferative state, but appears to be primed for further transformation events. Overall the data suggest that Runx2 accelerates development to the CD8 immature single-positive stage, but retards subsequent differentiation to the double-positive stage. Thus, Runx2 joins a small group of transcription factors that can interfere with early T cell development, cause an expansion of a specific subset, and predispose to lymphoma.
Surfactant Protein D Reduces Alveolar Macrophage Apoptosis In Vivo
Authors: Clark Howard , Palaniyar Nades , Strong Peter , Edmondson Jess , Hawgood Samuel , Reid Kenneth B. M.
Published: April 2014

Surfactant protein D (SP-D) is a molecule of the innate immune system that recognizes the patterns of surface carbohydrate on pathogens and targets them for phagocytosis and killing. SP-D-deficient mice show an increased number of macrophages in the alveolar space, excess surfactant phospholipid, overproduction of reactive oxygen species, and the development of emphysema. We report here that SP-D-deficient mice have a 5- to 10-fold increase in the number of apoptotic and necrotic alveolar macrophages, as defined by annexin V and propidium iodine staining, respectively. Intrapulmonary administration of a truncated 60-kDa fragment of human recombinant SP-D reduces the number of apoptotic and necrotic alveolar macrophages and partially corrects the lipid accumulation in SP-D-deficient mice. The same SP-D fragment binds preferentially to apoptotic and necrotic alveolar macrophages in vitro, suggesting that SP-D contributes to immune homeostasis in the lung by recognizing and promoting removal of necrotic and apoptotic cells.
A Role for the α-Chain Connecting Peptide Motif in Mediating TCR-CD8 Cooperation
Authors: Naeher Dieter , Luescher Immanuel F. , Palmer Ed
Published: April 2014

To generate peripheral T cells that are both self-MHC restricted and self-MHC tolerant, thymocytes are subjected to positive and negative selection. How the TCR discriminates between positive and negative selection ligands is not well understood, although there is substantial evidence that the CD4 and CD8 coreceptors play an important role in this cell fate decision. We have previously identified an evolutionarily conserved motif in the TCR, the α-chain connecting peptide motif (α-CPM), which allows the TCR to deliver positive selection signals. Thymocytes expressing α-CPM-deficient receptors do not undergo positive selection, whereas their negative selection is not impaired. In this work we studied the ligand binding and receptor function of α-CPM-deficient TCRs by generating T cell hybridomas expressing wild-type or α-CPM-deficient forms of the T1 TCR. This Kd-restricted TCR is specific for a photoreactive derivative of the Plasmodium berghei circumsporozoite peptide252–260 IASA-YIPSAEK(ABA)I and is therefore amenable to TCR photoaffinity labeling. The experiments presented in this work show that α-CPM-deficient TCRs fail to cooperate with CD8 to enhance ligand binding and functional responses.
Preventing NK Cell Activation by Donor Dendritic Cells Enhances Allospecific CD4 T Cell Priming and Promotes Th Type 2 Responses to Transplantation Antigens
Authors: Coudert Jérôme D. , Coureau Christiane , Guéry Jean-Charles
Published: April 2014

Although much progress has been made in understanding the role of NK cells in bone marrow transplantation, little is known about their function in CD4 T cell-mediated allograft rejection. We have previously shown that in the absence of CD8 T lymphocyte priming, the in vivo default development pathway of alloreactive CD4 T cells was strongly biased toward Th2 phenotype acquisition. In this study, we investigate the impact of NK cells on the activation and differentiation of alloreactive CD4 T cells in various donor/recipient combinations. Our data demonstrate that defective inhibition of host NK cells by donor APCs including dendritic cells (DCs) results in diminished allospecific Th cell responses associated with the development of effector Th cells producing IFN-γ rather than type 2 cytokines. Turning host NK cells off was sufficient to restore strong alloreactive CD4 T cell priming and Th2 cell development. Similar results were obtained by analyzing the effect of NK cell activation on CD4 T cell responses to skin allografts. However, despite the dramatic effect of NK cells on alloreactive Th1/Th2 cell development, the kinetics of skin graft rejection were not affected. Thus, Th2 differentiation is a major pathway of alloreactive CD4 T cell development during solid organ transplant rejection, as long as host NK and CD8 T cells are not activated. We propose the hypothesis that MHC class I-driven interactions between donor DCs and host NK cells or CD8 T cells might result in DC-carried signals controlling the dynamics of alloreactive CD4 T cell priming and polarization.
Regulation and Specificity ofMHC2TAPromoter Usage in Human Primary T Lymphocytes and Cell Line
Authors: Wong Athena W. , Ghosh Nilanjan , McKinnon Karen P. , Reed William , Piskurich Janet F. , Wright Kenneth L. , Ting Jenny P.-Y.
Published: April 2014

Although activated human T cells express MHC class II antigens, the regulation of these antigens in T cells is poorly understood. This study focuses on the control of the MHC2TA gene in these cells. MHC2TA encodes the transcriptional master regulator of MHC class II, the class II trans-activator (CIITA). It has at least three distinct promoters (PI, PIII, and PIV), each active in an overlapping subset of cell types and directing a slightly different product. This report used highly purified blood T cells prepared by negative immunoselection to analyze CIITA. Real-time PCR analysis indicates that resting T cells do not express detectable CIITA transcript, while activated T cells express the PIII CIITA form. Transient transfection of activated blood T cells using wild-type and mutant PIII promoter-reporter constructs shows that two promoter elements, activation response element-1 (ARE-1) and ARE-2, are important for PIII function. cAMP response element binding protein, a known activator of gene expression in activated T cells, activates PIII in primary T cells. However, an intact ARE-2 site is not required for this activation, indicating that cAMP response element binding protein does not activate via this site. EMSAs indicate that an activating transcription factor/cAMP response element binding protein/cAMP response element modulator family member, but not phosphorylated cAMP response element binding protein-1, binds to ARE-2. ARE-2 also forms a complex with an unidentified protein. The ARE-2 binding protein is constitutively expressed in a DR+ T cell line, reflecting differences between the DR+ cell line and primary blood lymphocytes. These results show that MHC2TA PIII is induced in activated T lymphocytes, and that the induced binding of ARE-2 is a crucial step in this process.
Differential Kinetics of Antigen-Specific CD4+ and CD8+ T Cell Responses in the Regression of Retrovirus-Induced Sarcomas
Authors: Schepers Koen , Toebes Mireille , Sotthewes Gitte , Vyth-Dreese Florry A. , Dellemijn Trees A. M. , Melief Cornelis J. M. , Ossendorp Ferry , Schumacher Ton N. M.
Published: April 2014

Despite the accepted role for CD4+ T cells in immune control, little is known about the development of Ag-specific CD4+ T cell immunity upon primary infection. Here we use MHC class II tetramer technology to directly visualize the Ag-specific CD4+ T cell response upon infection of mice with Moloney murine sarcoma and leukemia virus complex (MoMSV). Significant numbers of Ag-specific CD4+ T cells are detected both in lymphoid organs and in retrovirus-induced lesions early during infection, and they express the 1B11-reactive activation-induced isoform of CD43 that was recently shown to define effector CD8+ T cell populations. Comparison of the kinetics of the MoMSV-specific CD4+ and CD8+ T cell responses reveals a pronounced shift toward CD8+ T cell immunity at the site of MoMSV infection during progression of the immune response. Consistent with an important early role of Ag-specific CD4+ T cell immunity during MoMSV infection, CD4+ T cells contribute to the generation of virus-specific CD8+ T cell immunity within the lymphoid organs and are required to promote an inflammatory environment within the virus-infected tissue.
Vaccination with Recombinant Alphavirus or Immune-Stimulating Complex Antigen Against Respiratory Syncytial Virus
Authors: Chen Margaret , Hu Ke-Fei , Rozell Björn , Örvell Claes , Morein Bror , Liljeström Peter
Published: April 2014

Respiratory syncytial virus (RSV) causes severe respiratory diseases in infants and young children. Inappropriate immunity to the virus can lead to disease enhancement upon subsequent infection. In this study, we have characterized the antiviral immunity elicited by the recombinant Semliki Forest virus (SFV) encoding the RSV fusion (F) and attachment (G) protein, and compared with that induced by the immune-stimulating complex (ISCOM)-incorporated FG proteins. Antiviral immunity against RSV elicited nasally or parentally by either of the immunogen having divergent profiles could reduce lung RSV titers upon challenge. However, resistance to RSV without disease enhancement was only observed in those vaccinated with SFV recombinants via nasal route. Presence of postvaccination pulmonary IFN-γ response to the H-2Kd-restricted T cell epitope (F85–93; KYKNAVTEL) was found to be associated with absence of enhanced pulmonary disease and goblet cell hyperplasia as well as reduced Th2-cytokine expression. This result demonstrates that the SFV recombinants can result in enhanced clearance of RSV without enhancing the RSV-associated disease, and underlines the importance in priming pulmonary MHC class I-restricted T cells when RSV FG-based vaccines are used.
Complement-Induced Impairment of Innate Immunity During Sepsis
Authors: Huber-Lang Markus S. , Younkin Ellen M. , Sarma J. Vidya , McGuire Stephanie R. , Lu Kristina T. , Guo Ren Feng , Padgaonkar Vaishalee A. , Curnutte John T. , Erickson Richard , Ward Peter A.
Published: April 2014

This study defines the molecular basis for defects in innate immunity involving neutrophils during cecal ligation/puncture (CLP)-induced sepsis in rats. Blood neutrophils from CLP rats demonstrated defective phagocytosis and defective assembly of NADPH oxidase, the latter being due to the inability of p47phox to translocate from the cytosol to the cell membrane of neutrophils after cell stimulation by phorbol ester (PMA). The appearance of these defects was prevented by in vivo blockade of C5a in CLP rats. In vitro exposure of neutrophils to C5a led to reduced surface expression of C5aR and defective assembly of NADPH oxidase, as defined by failure in phosphorylation of p47phox and its translocation to the cell membrane, together with failure in phosphorylation of p42/p44 mitogen-activated protein kinases. These data identify a molecular basis for defective innate immunity involving neutrophils during sepsis.
The Early IL-4 Response toLeishmania majorand the Resulting Th2 Cell Maturation Steering Progressive Disease in BALB/c Mice Are Subject to the Control of Regulatory CD4+CD25+ T Cells
Authors: Aseffa Abraham , Gumy Alain , Launois Pascal , MacDonald H. Robson , Louis Jacques A. , Tacchini-Cottier Fabienne
Published: April 2014

Susceptibility and development of Th2 cells in BALB/c mice infected with Leishmania major result from early IL-4 production by Vβ4Vα8 CD4+ T cells in response to the Leishmania homolog of mammalian RACK1 Ag. A role for CD4+CD25+ regulatory T cells in the control of this early IL-4 production was investigated by depleting in vivo this regulatory T cell population. Depletion induced an increase in the early burst of IL-4 mRNA in the draining lymph nodes of BALB/c mice, and exacerbated the course of disease with higher levels of IL-4 mRNA and protein in their lymph nodes. We further showed that transfer of 107 BALB/c spleen cells that were depleted of CD4+CD25+ regulatory T cells rendered SCID mice susceptible to infection and allowed Th2 differentiation while SCID mice reconstituted with 107 control BALB/c spleen cells were resistant to infection with L. major and developed a Th1 response. Treatment with a mAb against IL-4 upon infection with L. major in SCID mice reconstituted with CD25-depleted spleen cells prevented the development of Th2 polarization and rendered them resistant to infection. These results demonstrate that CD4+CD25+ regulatory T cells play a role in regulating the early IL-4 mRNA and the subsequent development of a Th2 response in this model of infection.
Induction of CD8+ T Lymphocytes by Salmonella typhimurium Is Independent of Salmonella Pathogenicity Island 1-Mediated Host Cell Death
Authors: Wijburg Odilia L. C. , van Rooijen Nico , Strugnell Richard A.
Published: April 2014

Salmonella are intracellular bacterial pathogens that reside and replicate inside macrophages, and attenuated strains of Salmonella typhimurium can be used to deliver heterologous Ags for MHC class I and/or MHC class II-restricted presentation. Recently, it was shown that invasion of macrophages by S. typhimurium may result in the death of host macrophages via a mechanism harboring features of apoptotic and necrotic cell death. However, it is unknown whether this bacterial-induced host cell death affects immunity. In addition, it has been hypothesized that macrophage death following infection with S. typhimurium and subsequent uptake of apoptotic cells by APC are fundamental to the induction of CTL responses. In this study we investigated the in vivo induction of Ag-specific CD8+ T lymphocyte responses and compared CD8+ T lymphocyte responses elicited with S. typhimurium strains carrying a mutation in their invA gene, and therefore an inability to induce Salmonella pathogenicity island 1 (SPI-1)-mediated macrophage death, with responses elicited by an attenuated ΔaroAD strain. Ag-specific CD8+ T lymphocyte responses were analyzed using IFN-γ ELISPOT, tetramer binding, and in vivo and in vitro CTL assays. Our results showed that ΔaroAD and ΔaroADΔinvA induced comparable levels of Ag-specific CD8+ T lymphocyte responses as well as protective, Ag-specific B and CD4+ T lymphocyte immunity. Furthermore, experiments in macrophage-depleted mice showed that CD8+ T lymphocyte responses were effectively induced in the absence of macrophages. Together, our results imply that in this infection model, SPI-1-mediated cell death does not affect the immunological defense response and is not important for the induction of CD8+ T lymphocyte responses.
Suppression of Monocyte Chemoattractant Protein 1, But Not IL-8, by Alprazolam: Effect of Alprazolam on c-Rel/p65 and c-Rel/p50 Binding to the Monocyte Chemoattractant Protein 1 Promoter Region
Authors: Oda Taiko , Ueda Atsuhisa , Shimizu Noriaki , Handa Hiroshi , Kasahara Tadashi
Published: April 2014

Alprazolam is a hypnotic/tranquilizer that has been shown to specifically inhibit the platelet-activating factor (PAF)-induced aggregation of human platelets. The goal of this study was to elucidate whether alprazolam modulates IL-1α-initiated responses. For this purpose we investigated the effects of alprazolam on the IL-1α-induced production of inflammatory cytokines (IL-8 and monocyte chemoattractant protein 1 (MCP-1)) in a human glioblastoma cell line, T98G, and explored the signaling pathways involved. We found that alprazolam inhibited IL-1α-elicited MCP-1 production within a range of 0.1–3 μM. In contrast, it did not inhibit IL-1α-induced IL-8 production. Although NF-κB is involved in regulating the IL-1α-induced expression of MCP-1 and IL-8, the degradation of IκB-α stimulated by IL-1α was not inhibited by alprazolam. Alprazolam prevented NF-κB from binding to the MCP-1 promoter region (the A2 and A1 oligonucleotide probes), but binding of NF-κB to IL-8/NF-κB was not inhibited. Moreover, alprazolam inhibited c-Rel/p50 binding to the A2 oligonucleotide probe, but not p50/p65 from binding to the IL-8/NF-κB site. While AP-1 is involved in regulating the IL-1α-induced expression of IL-8, but not MCP-1, alprazolam potentiated the binding of c-Jun/c-Fos to the AP-1 oligonucleotide probe. These results show that the inhibition of IL-1α-mediated MCP-1 production by alprazolam is mainly due to inhibition of c-Rel/p65 and c-Rel/p50 binding to the MCP-1 promoter region, since alprazolam did not affect the IL-1α-mediated activation of NF-κB (p50/p65) or AP-1 (c-Jun/c-Fos) binding to the IL-8 promoter region. In conclusion, a new action of alprazolam was elucidated, as shown in the inhibition of c-Rel/p65- and c-Rel/p50-regulated transcription.
IL-4 and IL-12 Regulate Proteoglycan-Induced Arthritis Through Stat-Dependent Mechanisms
Authors: Finnegan Alison , Grusby Michael J. , Kaplan Charles D. , O’Neill Shannon K. , Eibel Hermann , Koreny Tamas , Czipri Matyas , Mikecz Katalin , Zhang Jian
Published: April 2014

IL-4, a well-recognized modulator of macrophage activation, is perceived as an anti-inflammatory cytokine; however, under certain circumstances IL-4 may function as a proinflammatory cytokine. We have previously demonstrated that IL-4 treatment of mice with proteoglycan-induced arthritis (PGIA) inhibited the development of disease. To determine whether the capacity of IL-4 to inhibit disease is dependent on IL-4-mediated regulation of IL-12, we assessed the requirement for IL-4 in modulating development of PGIA. Immunization of mice, lacking IL-4 and Stat6, with proteoglycan results in a significant increase in arthritis severity in comparison to wild-type controls, suggesting that arthritis severity is regulated by IL-4 through a Stat6-dependent mechanism. Concomitant with exacerbated disease in IL-4−/− mice, there is a significant increase in the systemic production of proinflammatory cytokines IL-12, TNF-α, and IFN-γ and in levels of mRNA transcripts for proinflammatory cytokines and chemokines in joints. Disease is suppressed in Stat4−/− mice indicating that elevated levels of IL-12 contribute to exacerbation of arthritis and that suppression is accompanied by reduced levels of IFN-γ production. In support of this, IFN-γ−/− mice are protected from PGIA and the degree of inflammation is similar to Stat4−/− mice. The decrease in disease severity in IFN-γ−/− and Stat4−/− mice correlates with diminished TNF-α levels but there is no switch to a Th2-type response. Taken together, these results suggest that IL-4 regulates the severity of disease in PGIA by controlling IL-12 production, which in turn regulates the magnitude of IFN-γ expression through a Stat4-dependent pathway.
TCR Rearrangement in Lymphocytes Infiltrating Melanoma Metastases After Administration of Autologous Dinitrophenyl-Modified Vaccine
Authors: Manne Jayanthi , Mastrangelo Michael J. , Sato Takami , Berd David
Published: April 2014

Administration of a vaccine consisting of autologous melanoma cells modified with a hapten, dinitrophenyl (DNP), induces T cell infiltration of metastatic sites. We have reported an analysis of these infiltrating T cells, indicating that certain TCR-Vβ gene segments are greatly overexpressed. In this study, we investigate the rearrangement of the TCR-Vβ as well as the junctional diversity in T cells infiltrating melanoma metastases following treatment with DNP vaccine. In 19 of 26 control specimens, V-D-J length analysis showed the expected polyclonal patterns. In contrast, postvaccine tumors from 9 of 10 patients showed dominant peaks of V-D-J junction size in one or more Vβ families. Dominant peaks were seen most frequently in six Vβ families (Vβ7, 12, 13, 14, 16, and 23) and were never seen in seven others. Further analysis of the oligoclonal Vβ products showed dominant peaks in the J region as well. Of particular interest was the finding that Vβ and Jβ peaks were similar in inflamed metastases obtained at different times or from different sites from the same patient. Although 6 of 10 patients expressed HLA-A1, there was no common pattern of TCR rearrangements among them. Finally, the amplified PCR products from seven of these specimens were cloned and sequenced and the amino acid sequence of the complementarity-determining region 3 was deduced. In six of seven specimens, the same complementarity-determining region 3 sequence was repeated in at least two clones and in five of seven in at least three clones. Our study indicates that DNP vaccine induces the expansion of particular T cell clones that may be agents of its antitumor effects.
MHC Class I Alleles Influence Set-Point Viral Load and Survival Time in Simian Immunodeficiency Virus-Infected Rhesus Monkeys
Authors: Mühl Thorsten , Krawczak Michael , ten Haaft Peter , Hunsmann Gerhard , Sauermann Ulrike
Published: April 2014

In HIV-infected humans and SIV-infected rhesus macaques, host genes influence viral containment and hence the duration of the disease-free latency period. Our knowledge of the rhesus monkey immunogenetics, however, is limited. In this study, we describe partial cDNA sequences of five newly discovered rhesus macaque (Mamu) class I alleles and PCR-based typing techniques for the novel and previously published Mhc class I alleles. Using 15 primer pairs for PCR-based typing and DNA sequence analysis, we identified at least 21 Mhc class I alleles in a cohort of 91 SIV-infected macaques. The results confirm the presence of multiple class I genes in rhesus macaques. Of these alleles, Mamu-A*01 was significantly associated with lower set-point viral load and prolonged survival time. Mamu-A*1303 was associated with longer survival and a “novel” Mhc class I allele with lower set-point viral load. The alleles are frequent in rhesus macaques of Indian origin (12–22%). In addition, survival probability of individual SIV-infected rhesus monkeys increased with their number of alleles considered to be associated with longer survival. The results contribute to improve the interpretation and quality of preclinical studies in rhesus monkeys.
Cutting Edge: Toll-Like Receptor (TLR)2- and TLR4-Mediated Pathogen Recognition in Resistance to Airborne Infection with Mycobacterium tuberculosis
Authors: Reiling Norbert , Hölscher Christoph , Fehrenbach Alexandra , Kröger Svenja , Kirschning Carsten J. , Goyert Sanna , Ehlers Stefan
Published: April 2014

Innate resistance against Mycobacterium tuberculosis is thought to depend critically on engagement of pattern recognition receptors on macrophages. However, the relative contribution of these receptors for containing M. tuberculosis infection has remained unexplored in vivo. To address this issue, we infected mice defective in CD14, TLR2, or TLR4 with M. tuberculosis by aerosol. Following infection with 100 mycobacteria, either mutant strain was as resistant as congenic control mice. Granuloma formation, macrophage activation, and secretion of proinflammatory cytokines in response to low-dose aerosol infection were identical in mutant and control mice. However, high-dose aerosol challenge with 2000 CFU M. tuberculosis revealed TLR2-, but not TLR4-defective mice to be more susceptible than control mice. In conclusion, while TLR2 signaling contributes to innate resistance against M. tuberculosis in borderline situations, its function, and that of CD14 and TLR4, in initiating protective responses against naturally low-dose airborne infection is redundant.