bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel Diversity in IL-4-Mediated Responses in Resting Human Naive B Cells Versus Germinal Center/Memory B Cells
Authors: Wagner Eric F. , Hanna Nazeeh , Fast Loren D. , Kouttab Nicola , Shank Peter R. , Vazquez Aime , Sharma Surendra 
Published: April 2014

AbstractRecent studies have defined several phenotypic and molecular changes associated with the maturation of naive human B cells within the milieu of germinal centers. Although naive B cells serve as natural precursors to germinal center (GC)/memory (M) subpopulations, little is known about the physiological requirements for the survival of the naive B cell pool in the absence of cell-cell contact or Ag-mediated activation. Because IL-4 induces expression of several membrane receptors such as CD23 which are uniquely present on resting human naive B lymphocytes, we hypothesized that these cells might be intrinsically programmed to respond to IL-4 in the absence of cell division. Using buoyant density-dependent isolation and further enrichment by negative/positive selection of human naive and GC/M subpopulations, we characterized cytokine receptor moieties on these cells and analyzed their survival and growth in the presence of IL-4 or IL-10. Resting naive B cells expressed significantly higher IL-4 receptor α-chain on their cell surface than the combined GC/M subpopulation. The IL-10 receptor and the IL-2 receptor γc chain were almost equally expressed on both subpopulations. When cultured in vitro, the addition of IL-4, but not IL-10, protected naive B cells from apoptosis in the absence of activation and growth. However, IL-4 exerted no such effect on resting GC/M B cells. These data support the hypothesis that IL-4 plays a pivotal role in the survival and maintenance of resting human naive B cells.
Regulation of MHC Class II Signal Transduction by the B Cell Coreceptors CD19 and CD22
Authors: Bobbitt Kevin R. , Justement Louis B. 
Published: April 2014

AbstractThe major histocompatability class II heterodimer (class II) is expressed on the surface of both resting and activated B cells. Although it is clear that class II expression is required for Ag presentation to CD4+ T cells, substantial evidence suggests that class II serves as a signal transducing receptor that regulates B cell function. In ex vivo B cells primed by Ag receptor (BCR) cross-linking and incubation with IL-4, or B cell lines such as K46-17μmλ, class II ligation leads to the activation of protein tyrosine kinases, including Lyn and Syk and subsequent phospholipase Cγ-dependent mobilization of Ca2+. In this study, experiments demonstrated reciprocal desensitization of class II and BCR signaling upon cross-linking of either receptor, suggesting that the two receptors transduce signals via common processes and/or effector proteins. Because class II and BCR signal transduction pathways exhibit functional similarities, additional studies were conducted to evaluate whether class II signaling is regulated by BCR coreceptors. Upon cross-linking of class II, the BCR coreceptors CD19 and CD22 were inducibly phosphorylated on tyrosine residues. Phosphorylation of CD22 was associated with increased recruitment and binding of the protein tyrosine phosphatase SHP-1. Similarly, tyrosine phosphorylation of CD19 resulted in recruitment and binding of Vav and phosphatidylinositol 3-kinase. Finally, co-cross-linking studies demonstrated that signaling via class II was either attenuated (CD22/SHP-1) or enhanced (CD19/Vav and phosphatidylinositol 3-kinase), depending on the coreceptor that was brought into close proximity. Collectively, these results suggest that CD19 and CD22 modulate class II signaling in a manner similar to that for the BCR.
TNF-Related Apoptosis-Inducing Ligand-Induced Apoptosis of Melanoma Is Associated with Changes in Mitochondrial Membrane Potential and Perinuclear Clustering of Mitochondria
Authors: Thomas Wayne D. , Zhang Xu Dong , Franco Agustin V. , Nguyen Tam , Hersey Peter 
Published: April 2014

AbstractPast studies have shown that TNF-related apoptosis-inducing ligand (TRAIL) induced apoptosis in a high proportion of cultured melanoma by caspase-dependent mechanisms. In the present studies we have examined whether TRAIL-induced apoptosis of melanoma was mediated by direct activation of effector caspases or whether apoptosis was dependent on changes in mitochondrial membrane potential (MMP) and mitochondrial-dependent pathways of apoptosis. Changes in MMP were measured by fluorescent emission from rhodamine 123 in mitochondria. TRAIL, but not TNF-α or Fas ligand, was shown to induce marked changes in MMP in melanoma, which showed a high correlation with TRAIL-induced apoptosis. This was associated with activation of proapoptotic protein Bid and release of cytochrome c into the cytosol. Overexpression of B cell lymphoma gene 2 (Bcl-2) inhibited TRAIL-induced release of cytochrome c, changes in MMP, and apoptosis. The pan caspase inhibitor z-Val-Ala-Asp-fluoromethylketone (zVAD-fmk) and the inhibitor of caspase-8 (z-Ile-Glu-Thr-Asp-fluoromethylketone; zIETD-fmk) blocked changes in MMP and apoptosis, suggesting that the changes in MMP were dependent on activation of caspase-8. Activation of caspase-9 also appeared necessary for TRAIL-induced apoptosis of melanoma. In addition, TRAIL, but not TNF-α or Fas ligand, was shown to induce clustering of mitochondria around the nucleus. This process was not essential for apoptosis but appeared to increase the rate of apoptosis. Taken together, these results suggest that TRAIL induces apoptosis of melanoma cells by recruitment of mitochondrial pathways to apoptosis that are dependent on activation of caspase-8. Therefore, factors that regulate the mitochondrial pathway may be important determinants of TRAIL-induced apoptosis of melanoma.
Priming by Microbial Antigens from the Intestinal Flora Determines the Ability of CD4+ T Cells to Rapidly Secrete IL-4 in BALB/c Mice Infected withLeishmania major
Authors: Julia Valérie , McSorley Stephen S. , Malherbe Laurent , Breittmayer Jean-Philippe , Girard-Pipau Fernand , Beck Alain , Glaichenhaus Nicolas 
Published: April 2014

AbstractInfection of BALB/c mice with Leishmania major results in the rapid accumulation of IL-4 transcripts within CD4+ T cells that react to the parasite Leishmania homologue of mammalian RACK1 (LACK) Ag. Because memory/effector cells secrete IL-4 more rapidly than naive cells, we sought to analyze the phenotype of these lymphocytes before infection. Indeed, a fraction of LACK-specific CD4+ T cells expressed a typical CD62 ligandlowCD44highCD45RBlow phenotype in uninfected mice. LACK-specific T cells were primed in gut-associated lymphoid tissues by cross-reactive microbial Ags as demonstrated by their reactivity with bacterial extracts and by the ability of APCs from the mesenteric LN of BALB/c mice to induce their proliferation. Also, mice in which the digestive tract has been decontaminated exhibited a reduced proportion of LACK-specific T cells expressing a memory/effector phenotype and did not exhibit the early accumulation of IL-4 transcripts induced by L. major. Thus, LACK-specific T cells represent a subset of CD4+ T cells which have acquired the ability to rapidly secrete IL-4 as the result of their priming by cross-reactive microbial Ags. Tracking the fate of these cells may provide information about the regulation of cell-mediated immune responses to gut Ags in physiological and pathological situations.
Reconstitution of T Cell-Specific Transcription Directed by Composite NFAT/Oct Elements
Authors: Bert Andrew G. , Burrows Joanna , Hawwari Abbas , Vadas Mathew A. , Cockerill Peter N. 
Published: April 2014

Abstract
The complex nature of most promoters and enhancers makes it difficult to identify key determinants of tissue-specific gene expression. Furthermore, most tissue-specific genes are regulated by transcription factors that have expression profiles more widespread than the genes they control. NFAT is an example of a widely expressed transcription factor that contributes to several distinct patterns of cytokine gene expression within the immune system and where its role in directing specificity remains undefined. To investigate distinct combinatorial mechanisms employed by NFAT to regulate tissue-specific transcription, we examined a composite NFAT/AP-1 element from the widely active GM-CSF enhancer and a composite NFAT/Oct element from the T cell-specific IL-3 enhancer. The NFAT/AP-1 element was active in the numerous cell types that express NFAT, but NFAT/Oct enhancer activity was T cell specific even though Oct-1 is ubiquitous. Conversion of the single Oct site in the IL-3 enhancer to an AP-1 enabled activation outside of the T cell lineage. By reconstituting the activities of both the IL-3 enhancer and its NFAT/Oct element in a variety of cell types, we demonstrated that their T cell-specific activation required the lymphoid cofactors NIP45 and OCA-B in addition to NFAT and Oct family proteins. Furthermore, the Oct family protein Brn-2, which cannot recruit OCA-B, repressed NFAT/Oct enhancer activity. Significantly, the two patterns of combinatorial regulation identified in this study mirror the cell-type specificities of the cytokine genes that they govern. We have thus established that simple composite transcription factor binding sites can indeed establish highly specific patterns of gene expression.
The Noncoding Regions of HLA-DRB Uncover Interlineage Recombinations as a Mechanism of HLA Diversification
Authors: Kotsch Katja , Blasczyk Rainer 
Published: April 2014

AbstractThe mechanisms generating new alleles at the MHC loci are still unknown in detail, and several proposals have been made to explain the extent of polymorphism. The patchwork pattern of polymorphism in the 2nd exon of HLA-DRB1 recommends this locus as a model for the study of the potential of interallelic gene conversion. In general, the inference of gene conversion-like events based exclusively on exon sequence comparisons may be misleading because the identity of the putative donor allele remains unknown. In this study, we describe five alleles of the HLA-DRB1 gene, which intron regions give evidence for interlineage recombination events either strictly located at the 2nd exon or involving the adjacent introns. Furthermore, we show that the noncoding regions provide important clues to the mechanisms of the generation of new alleles, and our results indicate that interlineage recombinations may be hidden and are perhaps more frequent than currently expected.
Vesicular Localization and Characterization of a Novel Post-Proline-Cleaving Aminodipeptidase, Quiescent Cell Proline Dipeptidase
Authors: Chiravuri Murali , Agarraberes Fernando , Mathieu Suzanne L. , Lee Henry , Huber Brigitte T. 
Published: April 2014

AbstractA large number of chemokines, cytokines, and signal peptides share a highly conserved X-Pro motif on the N-terminus. The cleavage of this N-terminal X-Pro dipeptide results in functional alterations of chemokines such as RANTES, stroma-derived factor-1, and macrophage-derived chemokine. Until recently, CD26/DPPIV was the only known protease with the ability to cleave N-terminal X-Pro motifs at neutral pH. We have isolated and cloned a novel serine protease, quiescent cell proline dipeptidase (QPP), with substrate specificity similar to that of CD26/DPPIV. In this paper we show that QPP, like CD26/DPPIV, is synthesized with a propeptide and undergoes N-glycosylation. Interestingly, this glycosylation is required for QPP enzymatic activity, but not for its localization. Unlike the cell surface molecule, CD26/DPPIV, QPP is targeted to intracellular vesicles that are distinct from lysosomes. Proteinase K treatment of intact vesicles indicates that QPP is located within the vesicles. These vesicles appear to have a secretory component, as QPP is secreted in a functionally active form in response to calcium release. The presence of QPP in the vesicular compartment suggests that molecules bearing the N-terminal X-Pro motif can be cleaved at multiple sites within and outside the cell. These results expand the potential site(s) and scope of a process that appears to be an important mechanism of post-translational regulation.
Induction of Antitumor Immunity by Vaccination of Dendritic Cells Transfected with MUC1 RNA
Authors: Koido Shigeo , Kashiwaba Masahiro , Chen Dongshu , Gendler Sandra , Kufe Donald , Gong Jianlin 
Published: April 2014

AbstractDendritic cells (DC) are potent APCs. In this study, murine bone marrow-derived DC were transfected with RNA encoding the MUC1 Ag that is aberrantly overexpressed in human breast and other carcinomas. The MUC1 RNA-transfected DC exhibited cell surface expression of MUC1 and costimulatory molecules. After injection at the base of the tail, the transfected DC were detectable in inguinal lymph nodes by dual immunochemical staining. Vaccination of wild-type mice with MUC1 RNA-transfected DC induced anti-MUC1 immune responses against MUC1-positive MC38/MUC1, but not MUC1-negative, tumor cells. Mice immunized with the transfected DC were protected against challenge with MC38/MUC1 tumor cells. Furthermore, mice with established MC38/MUC1 tumors were eliminated after receiving the vaccination. CTLs isolated from mice immunized with the transfected DC exhibited specific cytolytic activity against MC38/MUC1 tumor cells. In contrast to these findings, there was little if any anti-MUC1 immunity induced with the transfected DC in MUC1 transgenic (MUC1.Tg) mice. However, coadministration of the transfected DC and IL-12 reversed the unresponsiveness to MUC1 Ag in MUC1.Tg mice and induced MUC1-specific immune responses. These findings demonstrate that vaccination of DC transfected with MUC1 RNA and IL-12 reverses tolerance to MUC1 and induces immunity against MUC1-positive tumors.
Identification of a Role for NF-κB2 in the Regulation of Apoptosis and in Maintenance of T Cell-Mediated Immunity toToxoplasma gondii
Authors: Caamaño Jorge , Tato Cristina , Cai Guifang , Villegas Eric N. , Speirs Kendra , Craig Linden , Alexander James , Hunter Christopher A. 
Published: April 2014

AbstractThe NF-κB family of transcription factors are involved in the regulation of innate and adaptive immune functions associated with resistance to infection. To assess the role of NF-κB2 in the regulation of cell-mediated immunity, mice deficient in the NF-κB2 gene (NF-κB2−/−) were challenged with the intracellular parasite Toxoplasma gondii. Resistance to this opportunistic pathogen is dependent on the production of IL-12, which is required for the development of innate NK cell and adaptive T cell responses dominated by the production of IFN-γ necessary to control replication of this parasite. Although wild-type controls were resistant to T. gondii, NF-κB2−/− mice developed severe toxoplasmic encephalitis and succumbed to disease between 3 and 10 wk following infection. However, NF-κB2 was not required for the ability of macrophages to produce IL-12 or to inhibit parasite replication and during the acute stage of infection, NF-κB2−/− mice had no defect in their ability to produce IL-12 or IFN-γ and infection-induced NK cell responses appeared normal. In contrast, during the chronic phase of the infection, susceptibility of NF-κB2−/− mice to toxoplasmic encephalitis was associated with a reduced capacity of their splenocytes to produce IFN-γ associated with a loss of CD4+ and CD8+ T cells. This loss of T cells correlated with increased levels of apoptosis and with elevated expression of the pro-apoptotic molecule Fas by T cells from infected NF-κB2−/− mice. Together, these results suggest a role for NF-κB2 in the regulation of lymphocyte apoptosis and a unique role for this transcription factor in maintenance of T cell responses required for long-term resistance to T. gondii.
Clonal Expansions in Acute EBV Infection Are Detectable in the CD8 and not the CD4 Subset and Persist with a Variable CD45 Phenotype
Authors: Maini Mala K. , Gudgeon Nancy , Wedderburn Lucy R. , Rickinson Alan B. , Beverley Peter C. L. 
Published: April 2014

AbstractWe have applied a sensitive global analysis of TCR heterogeneity to compare clonal dynamics of CD4+ and CD8+ T cells in acute infectious mononucleosis. Using this approach, we are able to identify a broad representation of the total virus-specific population without the bias of in vitro culture and then to track their phenotype and fate by their unique molecular footprint. We demonstrate a large number of Ag-driven clones using different TCRs in the acute phase, all CD8+. The diverse large clones generated in the CD8 subset in response to this virus contrast with the complete lack of detectable clonal expansion in the CD4 compartment. Many of the same clones remain detectable in directly ex vivo CD8+ T cells for at least a year after resolution of infectious mononucleosis, although the clone size is reduced. Thus, memory CD8 cells following EBV infection persist at relatively high circulating frequency and represent a subset of the large range of clonotypes comprising the acute effectors. Separation of samples into CD45RA (naive) and CD45RO (memory) fractions shows the accumulation of identical CDR3 region defined clonotypes in both CD45RO and CD45RA fractions and sequencing confirms that dominant long-lived monoclonal expansions can reside in the CD45RA pool.
Bacterial Killing Is Enhanced by Expression of Lysozyme in the Lungs of Transgenic Mice
Authors: Akinbi Henry T. , Epaud Ralph , Bhatt Hetal , Weaver Timothy E. 
Published: April 2014

Abstract
To assess the role of lysozyme in pulmonary host defense in vivo, transgenic mice expressing rat lysozyme cDNA in distal respiratory epithelial cells were generated. Two transgenic mouse lines were established in which the level of lysozyme protein in bronchoalveolar (BAL) lavage fluid was increased 2- or 4-fold relative to that in WT mice. Lung structure and cellular composition of BAL were not altered by the expression of lysozyme. Lysozyme activity in BAL was significantly increased (6.6- and 17-fold) in 5-wk-old animals from each transgenic line. To determine whether killing of bacteria was enhanced by expression of rat lysozyme, 5-wk-old transgenic mice and WT littermates were infected with 106 CFU of group B streptococci or 107 CFU of a mucoid strain of Pseudomonas aeruginosa by intratracheal injection. Killing of group B streptococci was significantly enhanced (2- and 3-fold) in the mouse transgenic lines at 6 h postinfection and was accompanied by a decrease in systemic dissemination of pathogen. Killing of Pseudomonas aeruginosa was also enhanced in the transgenic lines (5- and 30-fold). Twenty-four hours after administration of Pseudomonas aeruginosa, all transgenic mice survived, whereas 20% of the WT mice died. Increased production of lysozyme in respiratory epithelial cells of transgenic mice enhanced bacterial killing in the lung in vivo, and was associated with decreased systemic dissemination of pathogen and increased survival following infection.
Gene Expressions of Toll-Like Receptor 2, But Not Toll-Like Receptor 4, Is Induced by LPS and Inflammatory Cytokines in Mouse Macrophages
Authors: Matsuguchi Tetsuya , Musikacharoen Tipayaratn , Ogawa Tomohiko , Yoshikai Yasunobu 
Published: April 2014

AbstractToll-like receptors (TLRs) are a family of mammalian homologues of Drosophila Toll and play important roles in host defense. Two of the TLRs, TLR2 and TLR4, mediate the responsiveness to LPS. Here the gene expression of TLR2 and TLR4 was analyzed in mouse macrophages. Mouse splenic macrophages responded to an intraperitoneal injection or in vitro treatment of LPS by increased gene expression of TLR2, but not TLR4. Treatment of a mouse macrophage cell line with LPS, synthetic lipid A, IL-2, IL-15, IL-1β, IFN-γ, or TNF-α significantly increased TLR2 mRNA expression, whereas TLR4 mRNA expression remained constant. TLR2 mRNA increase in response to synthetic lipid A was severely impaired in splenic macrophages isolated from TLR4-mutated C3H/HeJ mice, suggesting that TLR4 plays an essential role in the process. Specific inhibitors of mitogen-activated protein/extracellular signal-regulated kinase kinase and p38 kinase did not significantly inhibit TLR2 mRNA up-regulation by LPS. In contrast, LPS-mediated TLR2 mRNA induction was abrogated by pretreatment with a high concentration of curcumin, suggesting that NF-κB activation may be essential for the process. Taken together, our results indicate that TLR2, in contrast to TLR4, can be induced in macrophages in response to bacterial infections and may accelerate the innate immunity against pathogens.
Toll-Like Receptor 4, But Not Toll-Like Receptor 2, Is a Signaling Receptor forEscherichiaandSalmonellaLipopolysaccharides
Authors: Tapping Richard I. , Akashi Sachiko , Miyake Kensuke , Godowski Paul J. , Tobias Peter S. 
Published: April 2014

AbstractTwo members of the mammalian Toll-like receptor (TLR) family, TLR2 and TLR4, have been implicated as receptors mediating cellular activation in response to bacterial LPS. Through the use of mAbs raised against human TLR2 and TLR4, we have conducted studies in human cell lines and whole blood to ascertain the relative contribution of these receptors to LPS induced cytokine release. We show that the contribution of TLR2 and TLR4 to LPS-induced cellular activation correlates with the relative expression levels of these two TLRs in a given cell type. In addition, we have found that significant differences in cell stimulatory activity exist between various smooth and rough LPS types that cannot be ascribed to known LPS structural features. These results suggest that impurities in the LPS may be responsible for some of the activity and this would be in agreement with recently published results of others. Upon repurification, none of the commercial LPS preparations activate cells through TLR2, but continue to stimulate cells with comparable activity through TLR4. Our results confirm recent findings that TLR4, but not TLR2, mediates cellular activation in response to LPS derived from both Escherichia coli and Salmonella minnesota. Additionally, we show that TLR4 is the predominant signaling receptor for LPS in human whole blood.