bluuebunny/crossref_metadata_2025_split huggingface dataset:
CpG-A Oligonucleotides Induce a Monocyte-Derived Dendritic Cell-Like Phenotype That Preferentially Activates CD8 T Cells
Authors: Krug Anne , Rothenfusser Simon , Selinger S. , Bock C. , Kerkmann M. , Battiany J. , Sarris A. , Giese Thomas , Speiser D. , Endres Stefan , Hartmann Gunther 
Published: April 2014

Abstract
Human B cells and plasmacytoid dendritic cells recognize CpG motifs within microbial DNA via Toll-like receptor 9. Two functionally distinct types of CpG motif containing oligonucleotides (CpG ODN) have been described, CpG-A and CpG-B. In contrast to CpG-B, CpG-A induces high amounts of type I IFN (IFN-α and IFN-β) in plasmacytoid dendritic cells. In the present study, we examined the effects of CpG-A on human primary monocytes. In PBMC stimulated with CpG-A and GM-CSF, monocytes showed excellent survival, increased in size and granularity, and within 3 days developed a dendritic cell-like phenotype that was characterized by down-regulation of CD14, partial up-regulation of CCR7, and an increased surface expression of costimulatory and Ag-presenting molecules. This effect could be inhibited by a combination of blocking Abs to type I IFN, and no such CpG-A-induced changes were observed in purified monocytes. Although IL-12 production by this dendritic cell-like phenotype required additional stimulation with CD40 ligand, this cell type spontaneously up-regulated IL-15 expression. Consistent with the known effect of IL-15 on effector and memory CD8 T cells, the frequency of CCR7−/CD45RA− CD8 T cells was selectively increased in allogeneic T cell assays. Furthermore, this dendritic cell type was more potent to support both the generation and the IFN-γ production of autologous influenza matrix peptide-specific memory CD8 T cells as compared with dendritic cells generated in the presence of GM-CSF and IL-4. In conclusion, monocytes exposed to the cytokine milieu provided by CpG-A rapidly develop a dendritic cell-like phenotype that is well equipped to support CD8 T cell responses.
Expression of a Constitutively Active Stat6 In Vivo Alters Lymphocyte Homeostasis with Distinct Effects in T and B Cells
Authors: Bruns Heather A. , Schindler Ulrike , Kaplan Mark H. 
Published: April 2014

Abstract
IL-4 is a critical cytokine in the regulation of immune responses and genesis of atopy. Engagement of the IL-4R activates multiple signaling pathways, including the transcription factor Stat6. Stat6-deficient mice demonstrate the importance of this factor in lymphocyte proliferation, gene expression, and Th cell differentiation. Recently, a mutant Stat6 (Stat6VT) was generated that is transcriptionally active independent of IL-4 stimulation. To determine the ability of a constitutively active Stat6 to mimic IL-4-stimulated responses, we have generated transgenic mice expressing Stat6VT under control of the CD2 locus control region, restricting expression to lymphoid populations. The phenotype of Stat6VT transgenic mice is similar, but not identical, to IL-4 transgenic mice, suggesting a critical role for Stat6-independent signaling pathways in the generation of some IL-4 responses in vivo. The expression of a constitutively active Stat6 in vivo increases surface expression of IL-4-induced genes and increases serum levels of IgG1 and IgE, compared with nontransgenic mice. Stat6VT expression increases Th2 differentiation in vivo and in vitro. Stat6VT expression also dramatically alters homeostasis of peripheral lymphocyte populations resulting in decreased CD3+ cells and increased B220+ cells, compared with nontransgenic littermates. Altered T and B cell populations correlate with an activated phenotype and increased cell death in transgenic T cell, but not B cell, populations. Together these results suggest that expression of a constitutively active Stat6 has distinct effects on B and T lymphocytes.
Gangliosides from Human Melanoma Tumors Impair Dendritic Cell Differentiation from Monocytes and Induce Their Apoptosis
Authors: Péguet-Navarro Josette , Sportouch Myriam , Popa Iuliana , Berthier Odile , Schmitt Daniel , Portoukalian Jacques 
Published: April 2014

AbstractGangliosides are ubiquitous membrane-associated glycosphingolipids, which are involved in cell growth and differentiation. Most tumor cells synthesize and shed large amounts of gangliosides into their microenvironment, and many studies have unraveled their immunosuppressive properties. In the present study we analyzed the effects of GM3 and GD3 gangliosides, purified from human melanoma tumors, on the differentiation of monocyte-derived dendritic cells (MoDC). At concentrations close to those detected in the sera from melanoma patients, both gangliosides dose-dependently inhibit the phenotypic and functional differentiation of MoDC, as assessed by a strong down-regulation of CD1a, CD54, CD80, and CD40 Ags and impaired allostimulatory function on day 6 of culture. Furthermore, GM3 and GD3 gangliosides decreased the viable cell yield and induced significant DC apoptosis. Finally, addition of GD3 to differentiating DC impaired their subsequent maturation induced by CD154. The resulting DC produced low amounts of IL-12 and large amounts of IL-10, a cytokine pattern that might hamper an efficient antitumor immune response. In conclusion, the results demonstrate that gangliosides impair the phenotypic and functional differentiation of MoDC and induce their apoptosis, which may be an additional mechanism of human melanoma escape.
IL-4 Potentiates Activated T Cell Apoptosis Via an IL-2-Dependent Mechanism
Authors: Zhang Jian , Bárdos Tamás , Shao Qing , Tschopp Jurg , Mikecz Katalin , Glant Tibor T. , Finnegan Alison 
Published: April 2014

Abstract
Activation-induced cell death (AICD) of T cells is one of the major mechanisms of peripheral tolerance. The regulation of AICD by IL-4 is poorly understood. In this study, we report that AICD in IL-4-deficient T cells is significantly reduced compared with that in wild-type T cells. This impaired AICD correlates with the failure to induce degradation of cellular FLIP. IL-4-mediated enhancement of AICD and cellular FLIP degradation requires a Janus kinase/STAT-6 signaling pathway. Unexpectedly, these effects of IL-4 could be blocked by a neutralizing anti-IL-2 Ab, and addition of rIL-2 could completely restore the defective AICD in IL-4-deficient T cells. Furthermore, IL-4 regulates the T cell thresholds for IL-2 signaling during AICD. These data suggest that IL-4 promotes AICD via an IL-2-dependent mechanism.
Presentation by Recycling MHC Class II Molecules of an Influenza Hemagglutinin-Derived Epitope That Is Revealed in the Early Endosome by Acidification
Authors: Sinnathamby Gomathinayagam , Eisenlohr Laurence C. 
Published: April 2014

Abstract
We investigated the roles of nascent and recycling MHC class II molecules (MHC II) in the presentation of two well-defined I-Ed-restricted epitopes that are within distinct regions of the influenza virus hemagglutinin (HA) protein. The site 3 epitope (S3; residues 302–313) lies in the stalk region that unfolds in response to mild acidification, while the site 1 epitope (S1; residues 107–119) is situated in the stable globular domain. In a murine B lymphoma cell line and an I-Ed-transfected fibroblast cell line, presentation from inactivated virus of S3 is inhibited by primaquine, a compound that prevents recycling of cell surface proteins, including MHC II, while S1 presentation is unaffected. In contrast, brefeldin A, an agent that inhibits exit of proteins from the endoplasmic reticulum, selectively inhibited S1 presentation without affecting S3 presentation, suggesting that S1 presentation requires nascent MHC II. The use of agents that perturb endosomal function revealed a requirement for acidification of internalized viral particles for presentation of both epitopes. Notably, all compounds tested had similar effects on presentation of the two epitopes derived from endogenously synthesized HA. Thus, recycling I-Ed molecules appear to be crucial for capturing and presenting an epitope that is revealed in mild acidic conditions following the uptake of virions or the synthesis of Ag, while nascent I-Ed molecules are required for presentation of a second epitope located in a structurally constrained region of the same polypeptide. Viral glycoproteins, such as HA, may have been a major impetus for the evolutionary establishment of this recycling pathway.
Two Developmentally Distinct Populations of Dendritic Cells Inhabit the Adult Mouse Thymus: Demonstration by Differential Importation of Hematogenous Precursors Under Steady State Conditions
Authors: Donskoy Elina , Goldschneider Irving 
Published: April 2014

Abstract
Although a variety of lymphoid and myeloid precursors can generate thymic dendritic cells (DCs) under defined experimental conditions, the developmental origin(s) of DCs in the steady state thymus is unknown. Having previously used selective combinations of normal, parabiotic, and radioablated mice to demonstrate that blood-borne prothymocytes are imported in a gated and competitive manner, we used a similar approach in this study to investigate the importation of the hematogenous precursors of thymic DCs. The results indicate that two developmentally distinct populations of DC precursors normally enter the adult mouse thymus. The first population is indistinguishable from prothymocytes according to the following criteria: 1) inefficient (&lt;20%) exchange between parabiotic partners; 2) gated importation by the thymus; 3) competitive antagonism for intrathymic niches; 4) temporally linked generation of thymocytes and CD8αhigh DCs; and 5) absence from prothymocyte-poor blood samples. The second population differs diametrically from prothymocytes in each of these properties, and appears to enter the thymus in at least a partially differentiated state. The resulting population of DCs has a CD8α−/low phenotype, and constitutes ∼50% of total thymic DCs. The presence of two discrete populations of DCs in the steady state thymus implies functional heterogeneity consistent with evidence implicating lymphoid DCs in the negative selection of effector thymocytes and myeloid DCs in the positive selection of regulatory thymocytes.
Prevention of Autoantibody-Mediated Graves’-Like Hyperthyroidism in Mice with IL-4, a Th2 Cytokine
Authors: Nagayama Yuji , Mizuguchi Hiroyuki , Hayakawa Takao , Niwa Masami , McLachlan Sandra M. , Rapoport Basil 
Published: April 2014

Abstract
Graves’ hyperthyroidism has long been considered to be a Th2-type autoimmune disease because it is directly mediated by autoantibodies against the thyrotropin receptor (TSHR). However, several lines of evidence have recently challenged this concept. The present study evaluated the Th1/Th2 paradigm in Graves’ disease using a recently established murine model involving injection of adenovirus expressing the TSHR (AdCMVTSHR). Coinjection with adenovirus expressing IL-4 (AdRGDCMVIL-4) decreased the ratio of Th1/Th2-type anti-TSHR Ab subclasses (IgG2a/IgG1) and suppressed the production of IFN-γ by splenocytes in response to TSHR Ag. Importantly, immune deviation toward Th2 was accompanied by significant inhibition of thyroid-stimulating Ab production and reduction in hyperthyroidism. However, in a therapeutic setting, injection of AdRGDCMVIL-4 alone or in combination with AdCMVTSHR into hyperthyroid mice had no beneficial effect. In contrast, coinjection of adenoviruses expressing IL-12 and the TSHR promoted the differentiation of Th1-type anti-TSHR immune responses as demonstrated by augmented Ag-specific IFN-γ secretion from splenocytes without changing disease incidence. Coinjection of adenoviral vectors expressing IL-4 or IL-12 had no effect on the titers of anti-TSHR Abs determined by ELISA or thyroid-stimulating hormone-binding inhibiting Ig assays, suggesting that Ab quality, not quantity, is responsible for disease induction. Our observations demonstrate the critical role of Th1 immune responses in a murine model of Graves’ hyperthyroidism. These data may raise a cautionary note for therapeutic strategies aimed at reversing Th2-mediated autoimmune responses in Graves’ disease in humans.
The MHC Class I-Like IgG Receptor Controls Perinatal IgG Transport, IgG Homeostasis, and Fate of IgG-Fc-Coupled Drugs
Authors: Roopenian Derry C. , Christianson Gregory J. , Sproule Thomas J. , Brown Aaron C. , Akilesh Shreeram , Jung Nadja , Petkova Stefka , Avanessian Lia , Choi Eun Young , Shaffer Daniel J. , Eden Peter A. , Anderson Clark L. 
Published: April 2014

Abstract
Abs of the IgG isotype are efficiently transported from mother to neonate and have an extended serum t1/2 compared with Abs of other isotypes. Circumstantial evidence suggests that the MHC class I-related protein, the neonatal FcR (FcRn), is the FcR responsible for both in vivo functions. To understand the phenotypes imposed by FcRn, we produced and analyzed mice with a defective FcRn gene. The results provide direct evidence that perinatal IgG transport and protection of IgG from catabolism are mediated by FcRn, and that the latter function is key to IgG homeostasis, essential for generating a potent IgG response to foreign Ags, and the basis of enhanced efficacy of Fc-IgG-based therapeutics. FcRn is therefore a promising therapeutic target for enhancing protective humoral immunity, treating autoimmune disease, and improving drug efficacy.
The B Cell Coreceptor CD22 Associates with AP50, a Clathrin-Coated Pit Adapter Protein, Via Tyrosine-Dependent Interaction
Authors: John BinuJoy , Herrin Brantley R. , Raman Chander , Wang Yan-ni , Bobbitt Kevin R. , Brody Brian A. , Justement Louis B. 
Published: April 2014

Abstract
The B cell coreceptor CD22 plays an important role in regulating signal transduction via the B cell Ag receptor. Studies have shown that surface expression of CD22 can be modulated in response to binding of ligand (i.e., mAb). Thus, it is possible that alterations in the level of CD22 expression following binding of natural ligand(s) may affect its ability to modulate the Ag receptor signaling threshold at specific points during B cell development and differentiation. Therefore, it is important to delineate the physiologic mechanism by which CD22 expression is controlled. In the current study, yeast two-hybrid analysis was used to demonstrate that CD22 interacts with AP50, the medium chain subunit of the AP-2 complex, via tyrosine-based internalization motifs in its cytoplasmic domain. This interaction was further characterized using yeast two-hybrid analysis revealing that Tyr843 and surrounding amino acids in the cytoplasmic tail of CD22 comprise the primary binding site for AP50. Subsequent studies using transfectant Jurkat cell lines expressing wild-type or mutant forms of CD22 demonstrated that either Tyr843 or Tyr863 is sufficient for mAb-mediated internalization of CD22 and that these motifs are involved in its interaction with the AP-2 complex, as determined by coprecipitation of α-adaptin. Finally, experiments were performed demonstrating that treatment of B cells with either intact anti-Ig Ab or F(ab′)2 blocks ligand-mediated internalization of CD22. In conclusion, these studies demonstrate that internalization of CD22 is dependent on its association with the AP-2 complex via tyrosine-based internalization motifs.
The Mechanism of CD47-Dependent Killing of T Cells: Heterotrimeric Gi-Dependent Inhibition of Protein Kinase A
Authors: Manna Partha Pratim , Frazier William A. 
Published: April 2014

AbstractCD47 has been implicated in both positive and negative regulation of T cells as well as in T cell death. To clarify the role of CD47 in T cell function, we have studied the mechanism of T cell death in response to CD47 ligands, including mAb 1F7, thrombospondin-1, and a CD47 agonist peptide derived from it. CD47−/− Jurkat T cells (JINB8) were resistant to killing by all three ligands, indicating the essential role of CD47. Primary human T cells were also killed by CD47 ligands, but only after activation with anti-CD3. CD47-mediated cell death occurred without active caspases, DNA fragmentation, or Bcl-2 degradation. Pretreatment of Jurkat and primary T cells with pertussis toxin (PTX) prevented CD47-mediated death, indicating the involvement of Giα. Pretreatment of T cells with 8-bromo cAMP, forskolin, or 3-isobutyl-1-methylxanthine prevented the CD47-mediated apoptosis, and 1F7 dramatically reduced intracellular cAMP levels, an effect reversed with PTX. H89 and protein kinase A (PKA) inhibitor peptide, a specific PKA inhibitor, prevented rescue of T cells by PTX, 8-bromo cAMP, and forskolin, indicating a direct role for one or more PKA substrates. Thus, CD47-mediated killing of activated T cells occurs by a novel pathway involving regulation of cAMP levels by heterotrimeric Giα with subsequent effects mediated by PKA.
Murine Flt3 Ligand Expands Distinct Dendritic Cells with Both Tolerogenic and Immunogenic Properties
Authors: Miller George , Pillarisetty Venu G. , Shah Alaap B. , Lahrs Svenja , DeMatteo Ronald P. 
Published: April 2014

AbstractHuman Flt3 ligand can expand dendritic cells (DC) and enhance immunogenicity in mice. However, little is known about the effects of murine Flt3 ligand (mFlt3L) on mouse DC development and function. We constructed a vector to transiently overexpress mFlt3L in mice. After a single treatment, up to 44% of splenocytes became CD11c+ and the total number of DC increased 100-fold. DC expansion effects lasted for &gt;35 days. mFlt3L DC were both phenotypically and functionally distinct. They had increased expression of MHC and costimulatory molecules and expressed elevated levels of B220 and DEC205 but had minimal CD4 staining. mFlt3L DC also had a markedly altered cytokine profile, including lowered secretion of IL-6, IL-10, IFN-γ, and TNF-α, but had a slightly increased capacity to stimulate T cells in vitro. However, in a variety of in vivo models, DC expanded by mFlt3L induced tolerogenic effects on T cells. Adoptive transfer of Ag-pulsed mFlt3L splenic DC to naive mice actually caused faster rates of tumor growth and induced minimal CTL compared with control DC. mFlt3L also failed to protect against tumors in which human Flt3 ligand was protective, but depletion of CD4+ T cells restored tumor protection. Our findings 1) demonstrate that mFlt3L has distinct effects on DC development, 2) suggest an important role for mFlt3L in generating DC that have tolerogenic effects on T cells, and 3) may have application in immunotherapy in generating massive numbers of DC for an extended duration.
Toll-Like Receptor 3 Mediates a More Potent Antiviral Response Than Toll-Like Receptor 4
Authors: Doyle Sean E. , O’Connell Ryan , Vaidya Sagar A. , Chow Edward K. , Yee Kathleen , Cheng Genhong 
Published: April 2014

Abstract
We have recently described an IFN regulatory factor 3-mediated antiviral gene program that is induced by both Toll-like receptor (TLR)3 and TLR4 ligands. In our current study, we show that activation of IFN/viral response gene expression in primary macrophage cells is stronger and prolonged with TLR3 stimulation compared with that of TLR4. Our data also reveal that the cytoplasmic tails of both TLR3 and TLR4 can directly interact with myeloid differentiation factor 88 (MyD88). However, although Toll/IL-1 receptor homology domain-containing adaptor protein/MyD88 adaptor-like is able to associate with TLR4, we were unable to detect any interaction between Toll/IL-1 receptor homology domain-containing adaptor protein/MyD88 adaptor-like and TLR3. By using quantitative real-time PCR assays, we found that TLR3 expression is inducible by both TLR3 and TLR4 ligands, while TLR4 expression is not inducible by these same stimuli. Furthermore, using cells derived from mice deficient in the IFN-αβR, we show that both TLR3 and TLR4 require IFN-β autocrine/paracrine feedback to induce TLR3 expression and activate/enhance genes required for antiviral activity. More specifically, a subset of antiviral genes is initially induced independent of IFN-β, yet the cytokine further enhances expression at later time points. This was in contrast to a second set of genes (including TLR3) that is induced only after IFN-β production. Taken together, our data argue that, despite both TLR3 and TLR4 being able to use IFN-β to activate/enhance antiviral gene expression, TLR3 uses multiple mechanisms to enhance and sustain the antiviral response more strongly than TLR4.
Activated, But Not Resting, T Cells Can Be Recognized and Killed by Syngeneic NK Cells
Authors: Rabinovich Brian A. , Li Jennifer , Shannon John , Hurren Rose , Chalupny Jan , Cosman David , Miller Richard G. 
Published: April 2014

Abstract
We demonstrate that IL-2-activated NK cells or lymphokine-activated killer cells recognize and kill syngeneic CD4+ and CD8+ T cells that have been activated by APCs. Induction with APC required TCR-specific Ag, and lysis was perforin mediated. Brefeldin A, which disrupts protein transport, inhibited the sensitivity induced by activation. In BALB/c, expression of NKG2D ligands correlated with lysis and could be inhibited by brefeldin A. As well, addition of anti-NKG2D mAb to a killing assay completely abrogated lysis. Transduction of mouse NKG2D into a human NK cell line, YTSeco, conferred upon it the ability to kill activated BALB/c T cells, indicating that NKG2D is necessary for recognition. Our data provide a basis for studying a role for NK cells in T cell regulation.
Ligation of Retinoic Acid Receptor α Regulates Negative Selection of Thymocytes by Inhibiting Both DNA Binding of nur77 and Synthesis of Bim
Authors: Szegezdi Éva , Kiss Ildikó , Simon Ágnes , Blaskó Bernadett , Reichert Uwe , Michel Serge , Sándor Mátyás , Fésüs László , Szondy Zsuzsa 
Published: April 2014

Abstract
Negative selection refers to the selective deletion of autoreactive thymocytes. Its molecular mechanisms have not been well defined. Previous studies in our laboratory have demonstrated that retinoic acids, physiological ligands for the nuclear retinoid receptors, selectively inhibit TCR-mediated death under in vitro conditions, and the inhibition is mediated via the retinoic acid receptor (RAR) α. The present studies were undertaken to investigate whether ligation of RARα leads to inhibition of TCR-mediated death in vivo and to identify the molecular mechanisms involved. Three models of TCR-mediated death were studied: anti-CD3-mediated death of thymocytes in wild-type mice, and Ag- and bacterial superantigen-driven thymocyte death in TCR-transgenic mice expressing a receptor specific for a fragment of pigeon cytochrome c in the context of the Ek (class II MHC) molecule. Our data demonstrate that the molecular program of both anti-CD3- and Ag-driven, but not that of superantigen-mediated apoptosis involves up-regulation of nur77, an orphan nuclear receptor, and bim, a BH3-only member of the proapoptotic bcl-2 protein family, proteins previously implicated to participate in the negative selection. Ligation of RARα by the synthetic agonist CD336 inhibited apoptosis, DNA binding of nur77, and synthesis of bim induced by anti-CD3 or the specific Ag, but had no effect on the superantigen-driven cell death. Our data imply that retinoids are able to inhibit negative selection in vivo as well, and they interfere with multiple steps of the T cell selection signal pathway.