bluuebunny/crossref_metadata_2025_split huggingface dataset:
CD45 Function Is Regulated by an Acidic 19-Amino Acid Insert in Domain II That Serves as a Binding and Phosphoacceptor Site for Casein Kinase 2
Authors: Greer Susanna F. , Wang Yan-ni , Raman Chander , Justement Louis B. 
Published: April 2014

AbstractIn this study experiments were conducted to elucidate the physical/functional relationship between CD45 and casein kinase 2 (CK2). Immunoprecipitation experiments demonstrated that CK2 associates with CD45 and that this interaction is inducible upon Ag receptor cross-linking in B and T cell lines as well as murine thymocytes and splenic B cells. However, yeast two-hybrid analysis failed to demonstrate a physical interaction between the individual CK2 α, α′, or β subunits and CD45. In contrast, a yeast three-hybrid assay in which either CK2 α and β or α′ and β subunits were coexpressed with the cytoplasmic domain of CD45, demonstrated that both CK2 subunits are necessary for the interaction with CD45. Experiments using the yeast three-hybrid assay also revealed that a 19-aa acidic insert in domain II of CD45 mediates the physical interaction between CK2 and CD45. Structure/function experiments in which wild-type or mutant CD45RA and CD45RO isoforms were expressed in CD45-deficient Jurkat cells revealed that the 19-aa insert is important for optimal CD45 function. The ability of both CD45RA and CD45RO to reconstitute CD3-mediated signaling based on measurement of calcium mobilization and mitogen-activated protein kinase activation was significantly decreased by deletion of the 19-aa insert. Mutation of four serine residues within the 19-aa insert to alanine affected CD45 function to a similar extent compared with that of the deletion mutants. These findings support the hypothesis that a physical interaction between the CD45 cytoplasmic domain and CK2 is important for post-translational modification of CD45, which, in turn, regulates its catalytic function.
Regulation of NK Cell-Mediated Cytotoxicity by the Adaptor Protein 3BP2
Authors: Jevremovic Dragan , Billadeau Daniel D. , Schoon Renee A. , Dick Christopher J. , Leibson Paul J. 
Published: April 2014

AbstractStimulation of lymphocytes through multichain immune recognition receptors activates multiple signaling pathways. Adaptor proteins play an important role in integrating these pathways by their ability to simultaneously bind multiple signaling components. Recently, the 3BP2 adaptor protein has been shown to positively regulate the transcriptional activity of T cells. However, the mechanisms by which signaling components are involved in this regulation remain unclear, as does a potential role for 3BP2 in the regulation of other cellular functions. Here we describe a positive regulatory role for 3BP2 in NK cell-mediated cytotoxicity. We also identify p95vav and phospholipase C-γ isoforms as binding partners of 3BP2. Our results show that tyrosine-183 of 3BP2 is specifically involved in this interaction and that this residue critically influences 3BP2-dependent function. Therefore, 3BP2 regulates NK cell-mediated cytotoxicity by mobilizing key downstream signaling effectors.
Quantitative Relationship Between MHC Class II-Superantigen Complexes and the Balance of T Cell Activation Versus Death
Authors: Lavoie Pascal M. , McGrath Helen , Shoukry Naglaa H. , Cazenave Pierre-André , Sékaly Rafick-Pierre , Thibodeau Jacques 
Published: April 2014

AbstractThe binding of bacterial superantigens (SAgs) is profoundly affected by the nature of the MHC class II-associated antigenic peptide. It was proposed that this limitation in the density of SAgs displayed at the surface of APCs is important for efficient TCR serial triggering as well as for preventing apoptosis of the responding T lymphocytes. Here, we have addressed quantitatively the size of this SAg-receptive pool of HLA-DR molecules that are available to bind and present staphylococcal enterotoxin A (SEA) at the surface of B lymphocytes. Our binding curves, depletion experiments, and quantitative immunoprecipitations show that about half the HLA-DR class II molecules on B cells are refractory to SEA binding. Yet, as compared with typical nominal Ags, an unusually high amount of class II-SAg complexes can be presented to T cells. This characteristic appears to be necessary for SAg-induced T cell apoptosis. When &lt;0.3% of the total cell surface MHC class II molecules are occupied by SEA, T cells undergo a normal sequence of early activation events. However, presentation of a ligand density beyond this threshold results in T cell activation that is readily aborted by apoptosis but only after a few cell divisions. Thus, we confirm the existence of MHC class II subsets that are structurally unable to present SEA and provide a quantitative framework to account for the ability of bacterial SAgs to induce peripheral activation vs tolerance in the host.
Processing of Immunosuppressive Pro-TGF-β1,2 by Human Glioblastoma Cells Involves Cytoplasmic and Secreted Furin-Like Proteases
Authors: Leitlein Jens , Aulwurm Steffen , Waltereit Robert , Naumann Ulrike , Wagenknecht Bettina , Garten Wolfgang , Weller Michael , Platten Michael 
Published: April 2014

AbstractTGF-β is a putative mediator of immunosuppression associated with malignant glioma and other types of cancer. Subtilisin-like proprotein convertases such as furin are thought to mediate TGF-β processing. Here we report that human malignant glioma cell lines express furin mRNA and protein, exhibit furin-like protease (FLP) activity, and release active furin into the cell culture supernatant. FLP activity is not modulated by exogenous TGF-β or neutralizing TGF-β Abs. Exposure of LN-18 and T98G glioma cell lines to the furin inhibitor, decanoyl-Arg-Val-Lys-Arg-chloromethylketone, inhibits processing of the TGF-β1 and TGF-β2 precursor molecules and, consequently, the release of mature bioactive TGF-β molecules. Ectopic expression of PDX, a synthetic antitrypsin analog with antifurin activity, in the glioma cells inhibits FLP activity, TGF-β processing, and TGF-β release. Thus, subtilisin-like proprotein convertases may represent a novel target for the immunotherapy of malignant glioma and other cancers or pathological conditions characterized by enhanced TGF-β bioactivity.
Extrathymic Development of Vα11 T Cells in Placenta During Pregnancy and Their Possible Physiological Role
Authors: Yamasaki Masahiko , Sasho Takahisa , Moriya Hideshige , Kanno Masamoto , Harada Michishige , Kamada Noriaki , Shimizu Eiko , Nakayama Toshinori , Taniguchi Masaru 
Published: April 2014

AbstractThe molecular and cellular mechanisms of the feto-maternal immune responses in the placenta in connection with natural abortion remain unclear. In this report we provide evidence that Vα11 T cells developed in the placenta may be responsible for the induction of natural abortion. The majority of Vα11 TCRs detected during pregnancy showed a consensus motif in the CDR3 region, similar to that of anti-GM3 TCR clones, and were of maternal origin. Vα11 TCRs were found in the middle to late stages of gestation due to de novo generation in the placenta, not to migration from the maternal side, as evidenced by the significant increases in the out-of-frame Vα11 TCR mRNA and the copy number of circular DNA generated by Vα11 gene rearrangements. Furthermore, administration of anti-Vα11 Ab to pregnant mice resulted in a significant decrease in the incidence of fetal demise, suggesting that Vα11 T cells detected in the placenta develop extrathymically and are involved in natural abortion.
Novel G Protein-Coupled Responses in Leukocytes Elicited by a Chemotactic Bacteriophage Displaying a Cell Type-Selective Binding Peptide
Authors: Jaye David L. , Edens Heather A. , Mazzucchelli Luca , Parkos Charles A. 
Published: April 2014

AbstractRecently, we identified a neutrophil-binding phage displaying a novel peptide motif, GPNLTGRW. It was determined that this peptide, when displayed on bacteriophage (FGP phage), elicits a transient increase in cytosolic calcium. Here, we show that FGP phage stimulate neutrophil chemotaxis and induce a pertussis toxin-sensitive rise in cytosolic calcium in monocytes as well as in neutrophils. In contrast to the calcium response elicited by classical chemoattractants fMLP and IL-8, the FGP phage-elicited response in neutrophils is dependent on extracellular calcium and is mediated by receptor-activated, divalent cation channels. Consistent with G protein-coupled receptor signaling, FGP phage effect homologous and reciprocal heterologous desensitization with fMLP- and IL-8-stimulated calcium responses. Like non-G protein-coupled responses, the FGP-elicited calcium transient is abolished with phosphoinositide-3-kinase inactivation. Nonetheless, specific binding of GTP to neutrophil membranes follows stimulation with FGP phage, further supporting involvement of G proteins. However, FGP phage neither bind to nor elicit a calcium response from transfectant cells harboring known candidate G protein-coupled receptors. These data together suggest that the elicited responses are mediated by a novel G protein-coupled receptor or represent novel responses of a known receptor.
Recognition of HLA-Cw4 but Not HLA-Cw6 by the NK Cell Receptor Killer Cell Ig-Like Receptor Two-Domain Short Tail Number 4
Authors: Katz Gil , Markel Gal , Mizrahi Sa’ar , Arnon Tal I. , Mandelboim Ofer 
Published: April 2014

Abstract
NK cells are cytotoxic to virus-infected and tumor cells that have lost surface expression of class I MHC proteins. Target cell expression of class I MHC proteins inhibits NK cytotoxicity through binding to inhibitory NK receptors. In contrast, a similar family of activating NK receptors, characterized by the presence of a charged residue in their transmembrane portion and a truncated cytoplasmic tail, augment lysis by NK cells when ligated by an appropriate class I MHC protein. However, the class I MHC specificity of many of these activating NK receptors is still unknown. Here, we show enhanced lysis of HLA-Cw4 but not HLA-Cw6-expressing cells, by a subset of NK clones. This subset may express killer cell Ig-like receptor two-domain short tail number 4 (KIR2DS4), as suggested by staining with various mAb. It is still possible, however, that these clones may express receptors other than KIR2DS4 that might recognize HLA-Cw4. Binding of KIR2DS4-Ig fusion protein to cells expressing HLA-Cw4 but not to those expressing HLA-Cw6 was also observed. The binding of KIR2DS4-Ig to HLA-Cw4 is weaker than that of killer cell Ig-like receptor two-domain long tail number 1 (KIR2DL1)-Ig fusion protein; however, such weak recognition is capable of inhibiting lysis by an NK transfectant expressing a chimeric molecule of KIR2DS4 fused to the transmembrane and cytoplasmic portion of KIR2DL1. Residue α14 is shown to be important in the KIR2DS4 binding to HLA-Cw4. Implications of the role of the activating NK receptors in immunosurveillance are discussed.
Factors Affecting the Efficiency of CD8+ T Cell Cross-Priming with Exogenous Antigens
Authors: Maecker Holden T. , Ghanekar Smita A. , Suni Maria A. , He Xiao-Song , Picker Louis J. , Maino Vernon C. 
Published: April 2014

AbstractProcessing of exogenous protein Ags by APC leads predominantly to presentation of peptides on class II MHC and, thus, stimulation of CD4+ T cell responses. However, “cross-priming” can also occur, whereby peptides derived from exogenous Ags become displayed on class I MHC molecules and stimulate CD8+ T cell responses. We compared the efficiency of cross-priming with exogenous proteins to use of peptide Ags in human whole blood using a flow cytometry assay to detect T cell intracellular cytokine production. CD8+ T cell responses to whole CMV proteins were poorly detected (compared with peptide responses) in most CMV-seropositive donors. Such responses could be increased by using higher doses of Ag than were required to achieve maximal CD4+ T cell responses. A minority of donors displayed significantly more efficient CD8+ T cell responses to whole protein, even at low Ag doses. These responses were MHC class I-restricted and dependent upon proteosomal processing, indicating that they were indeed due to cross-priming. The ability to efficiently cross-prime was not a function of the number of dendritic cells in the donor’s blood. Neither supplementation of freshly isolated dendritic cells nor use of cultured, Ag-pulsed dendritic cells could significantly boost CD8 responses to whole-protein Ags in poorly cross-priming donors. Interestingly, freshly isolated monocytes performed almost as well as dendritic cells in inducing CD8 responses via cross-priming. In conclusion, the efficiency of cross-priming appears to be poor in most donors and is dependent upon properties of the individual’s APC and/or T cell repertoire. It remains unknown whether cross-priming ability translates into any clinical advantage in ability to induce CD8+ T cell responses to foreign Ags.
Stat6 Is Necessary and Sufficient for IL-4’s Role in Th2 Differentiation and Cell Expansion
Authors: Zhu Jinfang , Guo Liying , Watson Cynthia J. , Hu-Li Jane , Paul William E. 
Published: April 2014

AbstractIL-4 plays a critical role in the differentiation of TCR-stimulated naive CD4 T cells to the Th2 phenotype. In response to IL-4, the IL-4R activates a set of phosphotyrosine binding domain-containing proteins, including insulin receptor substrate 1/2, Shc, and IL-4R interacting protein, as well as Stat6. Stat6 has been shown to be required for Th2 differentiation. To determine the roles of the phosphotyrosine binding adaptors in Th2 differentiation, we prepared a retrovirus containing a mutant of the human (h)IL-4R α-chain, Y497F, which is unable to recruit these adaptors. The mutant hIL-4Rα, as well as the wild-type (WT) hIL-4Rα, was introduced into naive CD4 T cells. Upon hIL-4 stimulation, Y497F worked as well as the WT hIL-4Rα in driving Th2 differentiation, as measured by Gata3 up-regulation and IL-4 production. Furthermore, IL-4-driven cell expansion was also normal in the cells infected with Y497F, although cells infected with Y497F were not capable of phosphorylating insulin receptor substrate 2. These results suggest that the signal pathway mediated by Y497 is dispensable for both IL-4-driven Th2 differentiation and cell expansion. Both WT and Y497F hIL-4Rα lose the ability to drive Th2 differentiation and cell expansion in Stat6-knockout CD4 T cells. A constitutively activated form of Stat6 introduced into CD4 T cells resulted in both Th2 differentiation and enhanced cell expansion. Thus, activated Stat6 is necessary and sufficient to mediate both IL-4-driven Th2 differentiation and cell expansion in CD4 T cells.
A Role for TGF-β in the Generation and Expansion of CD4+CD25+ Regulatory T Cells from Human Peripheral Blood
Authors: Yamagiwa Satoshi , Gray J. Dixon , Hashimoto Shigeo , Horwitz David A. 
Published: April 2014

AbstractAn elusive goal in transplanting organs across histocompatibility barriers has been the induction of specific tolerance to avoid graft rejection. A considerable body of evidence exists that the thymus produces regulatory T cells that suppress the response of other T cells to antigenic stimulation. We report that TGF-β can induce certain CD4+ T cells in the naive (CD45RA+RO−) fraction in human peripheral blood to develop powerful, contact-dependent suppressive activity that is not antagonized by anti-TGF-β or anti-IL-10 mAbs. The costimulatory effects of TGF-β on naive CD4+ T cells up-regulated CD25 and CTLA-4 expression, increased their transition to the activated phenotype, but decreased activation-induced apoptosis. Suppressive activity was concentrated in the CD25+ fraction. These CD4+CD25+ regulatory cells prevented CD8+ T cells from proliferating in response to alloantigens and from becoming cytotoxic effector cells. Moreover, these regulatory cells exerted their suppressive activities in remarkably low numbers and maintained these effects even after they are expanded. Once activated, their suppressive properties were Ag nonspecific. Although &lt;1% of naive CD4+ T cells expressed CD25, depletion of this subset before priming with TGF-β markedly decreased the generation of suppressive activity. This finding suggests that CD4+CD25+ regulatory T cells induced ex vivo are the progeny of thymus-derived regulatory T cells bearing a similar phenotype. The adoptive transfer of these regulatory T cells generated and expanded ex vivo has the potential to prevent rejection of allogeneic organ grafts.
Evidence for Epigenetic Mechanisms That Silence Both Basal and Immune-Stimulated Transcription of the IL-8 Gene
Authors: Wen Xiaoming , Wu Gary D. 
Published: April 2014

Abstract
It is becoming increasingly clear that epigenetic silencing of gene transcription plays a critical role in the regulation of gene expression in many biological processes. Tight regulation of immunomodulatory substances that are important for the initiation of the inflammatory cascade, such as chemoattractive cytokines, is essential to prevent initiation of unrestrained immune activation. Using the Caco-2 intestinal cell line as a model, we reveal two distinctly different mechanisms by which the gene for the neutrophil chemoattractive cytokine IL-8 is silenced. Nuclear run-on studies, as well as stably transfected reporter and marked minigene constructs, demonstrate that cellular differentiation inhibits immune-activated transcription of the IL-8 gene, a mechanism that is dependent on histone deacetylase activity. Unexpectedly, this silencing mechanism does not involve previously described regulatory elements in the IL-8 promoter but rather cis-acting regions located at a distance from the IL-8 gene locus. Genomic elements distant to the immediate IL-8 locus are also required to silence aberrant basal transcriptional activity of the IL-8 promoter in the absence of immune activation. However, in this case, silencing occurs in a histone deacetylase-independent fashion. These findings were confirmed in transgenic mice in which, in the absence of these elements, aberrant IL-8 gene activity was present primarily in the intestinal tract. Epigenetic silencing of cytokine gene transcription through distant genomic elements is an important level of gene regulation that may be relevant to the pathogenesis of immunologic disease states.
Differential Expression of Inducible Costimulator-Ligand Splice Variants: Lymphoid Regulation of Mouse GL50-B and Human GL50 Molecules
Authors: Ling Vincent , Wu Paul W. , Miyashiro Joy S. , Marusic Suzana , Finnerty Heather F. , Collins Mary 
Published: April 2014

AbstractThe process of immunological costimulation between APC and T cells is mediated by protein ligand:receptor interactions. To date, costimulatory receptors known to be expressed by T cells include the structurally related proteins CD28 and the inducible costimulator (ICOS). The ligands to human and mouse ICOS, human GL50 (hGL50), and mouse GL50 (mGL50) were recently cloned and demonstrated to have sequence similarity to the CD28 ligands B7-1 and B7-2. Examination of mGL50 cDNA transcripts by 3′RACE revealed an alternatively spliced form, mGL50-B, that encoded a protein product with a divergent 27-aa intracellular domain. Both mGL50- and mGL50-B-transfected cells exhibited binding to human and mouse ICOS-Ig fusion protein, indicating that the alternate cytoplasmic domain of mGL50-B does not interfere with extracellular interactions with ICOS receptor. Flow cytometric and RT-PCR analysis of BALB/c and RAG1−/− mice splenocytes demonstrate that freshly isolated B cells, T cells, macrophages, and dendritic cells express both splice variant forms of ICOS ligand. Comparative analyses with the human ICOS ligand splice variants hGL50 and B7-H2 indicate that differential splicing at the junction of cytoplasmic exon 6 and exon 7 may be a common method by which GL50-ICOS immunological costimulatory processes are regulated in vivo.
Proteomic Analysis of Dendritic Cell-Derived Exosomes: A Secreted Subcellular Compartment Distinct from Apoptotic Vesicles
Authors: Théry Clotilde , Boussac Muriel , Véron Philippe , Ricciardi-Castagnoli Paola , Raposo Graça , Garin Jerôme , Amigorena Sebastian 
Published: April 2014

AbstractDendritic cells constitutively secrete a population of small (50–90 nm diameter) Ag-presenting vesicles called exosomes. When sensitized with tumor antigenic peptides, dendritic cells produce exosomes, which stimulate anti-tumor immune responses and the rejection of established tumors in mice. Using a systematic proteomic approach, we establish the first extensive protein map of a particular exosome population; 21 new exosomal proteins were thus identified. Most proteins present in exosomes are related to endocytic compartments. New exosomal residents include cytosolic proteins most likely involved in exosome biogenesis and function, mainly cytoskeleton-related (cofilin, profilin I, and elongation factor 1α) and intracellular membrane transport and signaling factors (such as several annexins, rab 7 and 11, rap1B, and syntenin). Importantly, we also identified a novel category of exosomal proteins related to apoptosis: thioredoxin peroxidase II, Alix, 14-3-3, and galectin-3. These findings led us to analyze possible structural relationships between exosomes and microvesicles released by apoptotic cells. We show that although they both represent secreted populations of membrane vesicles relevant to immune responses, exosomes and apoptotic vesicles are biochemically and morphologically distinct. Therefore, in addition to cytokines, dendritic cells produce a specific population of membrane vesicles, exosomes, with unique molecular composition and strong immunostimulating properties.
Characterization of a Pattern Recognition Protein, a Masquerade-Like Protein, in the Freshwater Crayfish Pacifastacus leniusculus
Authors: Lee So Young , Söderhäll Kenneth 
Published: April 2014

Abstract
A multifunctional masquerade-like protein has been isolated, purified, and characterized from hemocytes of the freshwater crayfish, Pacifastacus leniusculus. It was isolated by its Escherichia coli binding property, and it binds to formaldehyde-treated Gram-negative bacteria as well as to yeast, Saccharomyces cerevisiae, whereas it does not bind to formaldehyde-fixed Gram-positive bacteria. The intact masquerade (mas)-like protein is present in crayfish hemocytes as a heterodimer composed of two subunits with molecular masses of 134 and 129 kDa. Under reducing conditions the molecular masses of the intact proteins are not changed. After binding to bacteria or yeast cell walls, the mas-like protein is processed by a proteolytic enzyme. The 134 kDa of the processed protein yields four subunits of 65, 47, 33, and 29 kDa, and the 129-kDa protein results in four subunits of 63, 47, 33, and 29 kDa in 10% SDS-PAGE under reducing conditions. The 33-kDa protein could be purified by immunoaffinity chromatography using an Ab to the C-terminal part of the mas-like protein. This subunit of the mas-like protein has cell adhesion activity, whereas the two intact proteins, 134 and 129 kDa, have binding activity to LPSs, glucans, Gram-negative bacteria, and yeast. E. coli coated with the mas-like protein were more rapidly cleared in crayfish than only E. coli, suggesting this protein is an opsonin. Therefore, the cell adhesion and opsonic activities of the mas-like protein suggest that it plays a role as an innate immune protein.