bluuebunny/crossref_metadata_2025_split huggingface dataset:
Early Divergence of Fcε Receptor I Signals for Receptor Up-Regulation and Internalization from Degranulation, Cytokine Production, and Survival
Authors: Kitaura Jiro , Xiao Wenbin , Maeda-Yamamoto Mari , Kawakami Yuko , Lowell Clifford A. , Kawakami Toshiaki 
Published: April 2014

Abstract
Mast cells play a critical role in IgE-dependent immediate hypersensitivity. Monomeric IgE binding to its high affinity receptor (FcεRI) results in a number of biological outcomes in mouse mast cells, including increased surface expression of FcεRI and enhanced survival. IgE molecules display heterogeneity in inducing cytokine production; highly cytokinergic IgEs cause extensive FcεRI aggregation, leading to potent enhancement of survival and other activation events, whereas poorly cytokinergic IgEs can do so less efficiently. In this study, we demonstrate that IgE-induced receptor up-regulation is not sensitive to monovalent hapten, which can prevent receptor aggregation induced by IgE, whereas other activation events such as receptor internalization, degranulation, IL-6 production, and survival are sensitive to monovalent hapten. IgE-induced receptor up-regulation is also unique in that no Src family kinases, Syk, or Btk are required for it. By contrast, highly cytokinergic IgE-induced receptor internalization is dependent on Lyn, but not other Src family kinases, Syk, or Btk, whereas degranulation, IL-6 production, and survival require Syk. Weak to moderate stimulation with IgE plus anti-IgE or IgE plus Ag enhances survival, while stronger signals are required for degranulation and IL-6 production. Collectively, signals emanated from IgE-bound FcεRI for receptor up-regulation and internalization are shown to diverge at the receptor or receptor-proximal levels from those for other biological outcomes.
Induction of a CD4+ T Regulatory Type 1 Response by Cyclooxygenase-2-Overexpressing Glioma
Authors: Akasaki Yasuharu , Liu Gentao , Chung Nancy H. C. , Ehtesham Moneeb , Black Keith L. , Yu John S. 
Published: April 2014

Abstract
PGE2, synthesized by cyclooxygenase-2 (COX-2)-overexpressing tumor, is known to contribute to cellular immune suppression in cancer patients, but the mechanism remains unclear. We report the mechanism of a CD4+ T regulatory type 1 (Tr1) induction by CD11c+ mature dendritic cells (DCs) that phagocytose allogeneic and autologous COX-2-overexpressing glioma. A human glioma cell line, U-87MG, and primary cultured glioblastoma cells (MG-377) overexpressed COX-2. We did not detect IL-10Rα expression in these gliomas, and rIL-10 did not suppress their COX-2 expression. Exposure to COX-2-overexpressing glioma induced mature DCs to overexpress IL-10 and decreased IL-12p70 production. These DCs induced a Tr1 response, which is characterized by robust secretion of IL-10 and TGF-β with negligible IL-4 secretion by CD4+ T cells, and an inhibitory effect on admixed lymphocytes. Peripheral CD4+ T cell populations isolated from an MG-377 patient also predominantly demonstrated a Tr1 response against MG-377 cells. Selective COX-2 inhibition in COX-2-overexpressing gliomas at the time of phagocytic uptake by DCs abrogated this regulatory response and instead elicited Th1 activity. COX-2 stable transfectants in LN-18 (LN-18-COX2) also induced a Tr1 response. The effect of a COX-2 inhibition in LN-18-COX2 is reversible after administration of PGE2. Taken together, robust levels of PGE2 from COX-2-overexpressing glioma, which is unresponsive to IL-10 within the local microenvironment, may cause DCs to secrete high levels of IL-10. These results indicate that COX-2-overexpressing tumors induce a Tr1 response, which is mediated by tumor-exposed, IL-10-enhanced DCs.
Repertoire and Immunofocusing of CD8 T Cell Responses Generated by HIV-1 gag-pol and Expression Library Immunization Vaccines
Authors: Singh Rana A. K. , Barry Michael A. 
Published: April 2014

Abstract
Several gene-based vaccine approaches are being tested to drive multivalent cellular immune responses to control HIV-1 viral variants. To compare the utility of these approaches, HLA-A*0201 transgenic mice were genetically immunized with plasmids encoding wild-type (wt) gag-pol, codon-optimized (CO) gag-pol, and an expression library immunization (ELI) vaccine genetically re-engineered to express non-CO fragments of gag and pol fused to ubiquitin for proteasome targeting. Equimolar delivery of each vaccine into HLA-A*0201 transgenic mice generated CD8 T cell responses, with the ELI vaccine producing up to 10-fold higher responses than the wt or CO gag-pol plasmids against cognate and mutant epitopes. All three vaccines generated multivalent CD8 responses against varying numbers of epitopes after priming. However, when the animals were immunized again, the wt and CO gag-pol vaccines boosted only the responses against a subset of epitopes and attenuated the responses against all other Ags including epitopes from clade and drug-resistant viral variants. In contrast, the ELI vaccine boosted CD8 responses against all of the gag-pol Ags and against mutant epitopes from clade and drug-resistant variants. These data suggest that HIV-1 vaccines expressing structurally intact gag and pol proteins drive immunofocused CD8 responses that reduce the repertoire of T cell responses. In contrast, the genetically re-engineered ELI vaccine appears to better maintain the multivalent CD8 responses that may be required to control HIV-1 viral variants.
DNA Methylation Is a Nonredundant Repressor of the Th2 Effector Program
Authors: Makar Karen W. , Wilson Christopher B. 
Published: April 2014

Abstract
The extent to which DNA methylation contributes to proper regulation of murine T cell effector function is unclear. In this study, we show that in the absence of the maintenance DNA methyltransferase Dnmt1, silencing of IL-4, IL-5, IL-13, and IL-10 in CD8 T cells was abolished, and expression of these Th2 cytokines increased as much as 1000-fold compared with that of control CD8 T cells. Th2 cytokine expression also increased in Dnmt1−/− CD4 T cells, but the increase (∼20–40-fold for IL-4 and IL-10, ≤5-fold for IL-5 and IL-13) was less than for CD8 T cells. As a result, both Dnmt1−/− CD4 and CD8 T cells expressed high and comparable amounts of Th2 cytokines. Loss of Dnmt1 had more subtle effects on IL-2 (≤5-fold increase) and IFN-γ (∼5–10-fold increase) expression and did not affect the normal bias for greater IL-2 expression by CD4 T cells and greater IFN-γ expression by CD8 T cells, nor the exclusive expression of perforin and granzyme B by the CD8 T cells. These results indicate that Dnmt1 and DNA methylation are necessary to prevent cell autonomous Th2 cytokine expression in CD8 T cells but are not essential for maintaining proper T cell subset-specific expression of Th1 or CTL effectors. We also found that the expression of Th2 cytokines by Dnmt1−/− T cells was appropriately up-regulated in Th2 conditions and down-regulated in Th1 conditions, indicating that transcription factors and DNA methylation are complementary and nonredundant mechanisms by which the Th2 effector program is regulated.
IL-16 Activates Plasminogen-Plasmin System and Promotes Human Eosinophil Migration into Extracellular Matrix via CCR3-Chemokine-Mediated Signaling and by Modulating CD4 Eosinophil Expression
Authors: Ferland Claudine , Flamand Nicolas , Davoine Francis , Chakir Jamila , Laviolette Michel 
Published: April 2014

AbstractIncreased eosinophil counts are a major feature of asthmatic airways. Eosinophil recruitment requires migration through epithelium and tissue extracellular matrix by activation of proteases. We assessed the capacity of IL-16, a CD4+ cell chemotactic factor, to induce migration of eosinophils through a reconstituted basement membrane and evaluated the proteases, mediators, and receptors involved in this migration. IL-16 added to lower chambers of Invasion Chambers elicited eosinophil migration through Matrigel. This effect was decreased by inhibition of the plasminogen-plasmin system (Abs against urokinase plasminogen activator receptor or plasminogen depletion), but not by anti-matrix metalloproteinase-9 Abs. Abs against CD4 also inhibited IL-16-induced eosinophil migration. At the baseline level, few eosinophils (4.6% positive cells with a mean fluorescence of 0.9) expressed surface membrane CD4, while most permeabilized eosinophils (68% positive cells with a mean fluorescence of 18) express the CD4 Ag. TNF-pretreatment increased surface membrane CD4+ expression by 6-fold as previously described, and increased IL-16-induced cell migration by 2.2-fold. Incubation of eosinophils with IL-16 also increased surface membrane CD4 expression by 5.4-fold, supporting the role of CD4 as receptor for IL-16. Abs against CCR3, eotaxin, or RANTES blocked IL-16-induced migration. In conclusion, IL-16 promotes eosinophil migration in vitro, by activating the plasminogen-plasmin system and increasing the membrane expression of its receptor. This effect is initiated via CD4 and mediated via the release of CCR3 ligand chemokines. Interestingly, most eosinophils express intracellular CD4. Hence, IL-16 may play an important role in the recruitment of blood eosinophils to the bronchial mucosa of asthmatics.
Relevance of the Direct Pathway of Sensitization in Corneal Transplantation Is Dictated by the Graft Bed Microenvironment
Authors: Huq Syed , Liu Ying , Benichou Gilles , Dana M. Reza 
Published: April 2014

Abstract
Corneal grafts were until recently considered entirely devoid of resident APCs, giving rise to the tenet that alloantigen recognition is mediated exclusively by the indirect (host APC-dependent) pathway. The recent discovery of a resident myeloid corneal dendritic cell population that is normally MHC class II− but can readily up-regulate class II expression during inflammation led us to hypothesize that under certain conditions the direct pathway of allosensitization becomes operative. To test this, corneal allotransplants were performed in either inflamed (high-risk (HR)) or uninflamed (low-risk (LR)) host beds in mice, and the frequencies of host T cells activated via the direct pathway were determined. We found that directly primed CD4+ T cells were detected in the HR but not LR setting, and these cells displayed a clear Th1 phenotype by 2 wk after grafting. Moreover, the use of MHC class II knockout donor tissue led to significantly enhanced survival of HR but not LR allografts. Finally, we show that donor corneal APC demonstrate high expression of CD40, CD80, and CD86 costimulatory molecules when derived from HR but not LR grafts. These data are the first to report that a functional donor APC-dependent direct response is elicited in corneal transplant hosts when the graft bed is inflamed and underscore the relevance of the graft microenvironment in dictating the pathway of allosensitization.
Transcription of Ig Germline Genes in Single Human B Cells and the Role of Cytokines in Isotype Determination
Authors: Fear David J. , McCloskey Natalie , O’Connor Brian , Felsenfeld Gary , Gould Hannah J. 
Published: April 2014

AbstractWe have developed a critical test of the chromatin accessibility model of Ig isotype determination in which local unfolding of chromatin higher order structure (chromatin accessibility) in the region of specific germline genes in the H chain locus determines the Ab class to be expressed in the B cell. We show that multiple germline genes are constitutively transcribed in the majority of naive human B cells in a population. Thus, because chromatin in its higher order structure cannot be transcribed, the entire Ig H chain locus must be unfolded in naive B cells. We have also established that IL-4 and anti-CD40 act by enhancing transcription in the majority of cells, rather than by activating transcription in more of the cells. Transcriptional activity in the human H chain locus rules out the perturbation of chromatin higher order structure as a factor in isotype determination. We have also found that the levels of germline gene transcription cannot fully account for the levels of secretion of the different Ig isotypes, and that secretion of IgE, in particular, is suppressed relative to that of IgG.
MHC Class II Molecules Traffic into Lipid Rafts during Intracellular Transport
Authors: Poloso Neil J. , Muntasell Aura , Roche Paul A. 
Published: April 2014

Abstract
There have been many studies demonstrating that a portion of MHC class II molecules reside in detergent-insoluble membrane domains (commonly referred to as lipid rafts). We have proposed that the function of raft association is to concentrate specific MHC class II-peptide complexes in plasma membrane microdomains that can facilitate efficient T cell activation. We now show that MHC class II becomes lipid raft associated before binding antigenic peptides. Using pulse-chase radiolabeling techniques, we find that newly synthesized MHC class II and MHC class II-invariant chain complexes initially reside in a detergent-soluble membrane fraction and acquire detergent insolubility as they traffic to lysosomal Ag processing compartments. Monensin, an inhibitor of protein transport through the Golgi apparatus, blocks association of newly synthesized MHC class II with lipid rafts. Treatment of cells with leupeptin, which inhibits invariant chain degradation, leads to the accumulation of MHC class II in lipid rafts within the lysosome-like Ag-processing compartments. Raft fractionation of lysosomal membranes confirmed the presence of MHC class II in detergent-insoluble microdomains in Ag-processing compartments. These findings indicate that newly synthesized MHC class II complexes are directed to detergent-insoluble lipid raft microdomains before peptide loading, a process that may facilitate the loading of similar peptides on MHC class II complexes in these microdomains.
Complement Components C5 and C7: Recombinant Factor I Modules of C7 Bind to the C345C Domain of C5
Authors: Thai Chuong-Thu , Ogata Ronald T. 
Published: April 2014

Abstract
Studies reported over 30 years ago revealed that latent, nonactivated C5 binds specifically and reversibly to C6 and C7. These reversible reactions are distinct from the essentially nonreversible associations with activated C5b that occur during assembly of the membrane attack complex, but they likely involve some, perhaps many, of the same molecular contacts. We recently reported that these reversible reactions are mediated by the C345C (NTR) domain at the C terminus of the C5 α-chain. Earlier work by others localized the complementary binding sites to a tryptic fragment of C6 composed entirely of two adjacent factor I modules (FIMs), and to a larger fragment of C7 composed of its homologous FIMs as well as two adjoining short consensus repeat modules. In this work, we expressed the tandem FIMs from C7 in bacteria. The mobility on SDS-polyacrylamide gels, lack of free sulfhydryl groups, and atypical circular dichroism spectrum of the recombinant product rC7-FIMs were all consistent with a native structure. Using surface plasmon resonance, we found that rC7-FIMs binds specifically to both C5 and the rC5-C345C domain with KD ≈ 50 nM, and competes with C7 for binding to C5, as expected for an active domain. These results indicate that, like C6, the FIMs alone in C7 mediate reversible binding to C5. Based on available evidence, we suggest a model for an irreversible membrane attack complex assembly in which the C7 FIMs, but not those in C6, are bound to the C345C domain of C5 within the fully assembled complex.
Homologs of CD83 from Elasmobranch and Teleost Fish
Authors: Ohta Yuko , Landis Eric , Boulay Thomas , Phillips Ruth B. , Collet Bertrand , Secombes Chris J. , Flajnik Martin F. , Hansen John D. 
Published: April 2014

Abstract
Dendritic cells are one of the most important cell types connecting innate and adaptive immunity, but very little is known about their evolutionary origins. To begin to study dendritic cells from lower vertebrates, we isolated and characterized CD83 from the nurse shark (Ginglymostoma cirratum (Gici)) and rainbow trout (Oncorhynchus mykiss (Onmy)). The open reading frames for Gici-CD83 (194 aa) and Onmy-CD83 (218 aa) display ∼28–32% identity to mammalian CD83 with the presence of two conserved N-linked glycosylation sites. Identical with mammalian CD83 genes, Gici-CD83 is composed of five exons including conservation of phase for the splice sites. Mammalian CD83 genes contain a split Ig superfamily V domain that represents a unique sequence feature for CD83 genes, a feature conserved in both Gici- and Onmy-CD83. Gici-CD83 and Onmy-CD83 are not linked to the MHC, an attribute shared with mouse but not human CD83. Gici-CD83 is expressed rather ubiquitously with highest levels in the epigonal tissue, a primary site for lymphopoiesis in the nurse shark, whereas Onmy-CD83 mRNA expression largely paralleled that of MHC class II but at lower levels. Finally, Onmy-CD83 gene expression is up-regulated in virus-infected trout, and the promoter is responsive to trout IFN regulatory factor-1. These results suggest that the role of CD83, an adhesion molecule for cell-mediated immunity, has been conserved over 450 million years of vertebrate evolution.
IL-4-Induced Gene-1 Is a Leukocyte l-Amino Acid Oxidase with an Unusual Acidic pH Preference and Lysosomal Localization
Authors: Mason James M. , Naidu Mamta D. , Barcia Michele , Porti Debra , Chavan Sangeeta S. , Chu Charles C. 
Published: April 2014

Abstract
IL-4-induced gene-1 (Il4i1 or Fig1) initially isolated as a gene of unknown function from mouse B lymphocytes, is limited in expression to primarily immune tissues and genetically maps to a region of susceptibility to autoimmune disease. The predicted Il4i1 protein (IL4I1) sequence is most similar to apoptosis-inducing protein and Apoxin I, both l-amino acid oxidases (LAAO; Enzyme Commission 1.4.3.2). We demonstrate that IL4I1 has unique LAAO properties. IL4I1 has preference for aromatic amino acid substrates, having highest specific activity with phenylalanine. In support of this selectivity, IL4I1 is inhibited by aromatic competitors (benzoic acid and para-aminobenzoic acid), but not by nonaromatic LAAO inhibitors. Il4i1 protein and enzyme activity is found in the insoluble fraction of transient transfections, implying an association with cell membrane and possibly intracellular organelles. Indeed, IL4I1 has the unique property of being most active at acidic pH (pH 4), suggesting it may reside preferentially in lysosomes. IL4I1 is N-linked glycosylated, a requirement for lysosomal localization. Confocal microscopy of cells expressing IL4I1 translationally fused to red fluorescent protein demonstrated that IL4I1 colocalized with GFP targeted to lysosomes and with acriflavine, a green fluorescent dye that is taken up into lysosomes. Thus, IL4I1 is a unique mammalian LAAO targeted to lysosomes, an important subcellular compartment involved in Ag processing.
The Emerging Pathogen Moraxella catarrhalis Interacts with Complement Inhibitor C4b Binding Protein through Ubiquitous Surface Proteins A1 and A2
Authors: Nordström Therése , Blom Anna M. , Forsgren Arne , Riesbeck Kristian 
Published: April 2014

Abstract
Moraxella catarrhalis ubiquitous surface protein A2 (UspA2) mediates resistance to the bactericidal activity of normal human serum. In this study, an interaction between the complement fluid phase regulator of the classical pathway, C4b binding protein (C4BP), and M. catarrhalis mutants lacking UspA1 and/or UspA2 was analyzed by flow cytometry and a RIA. Two clinical isolates of M. catarrhalis expressed UspA2 at a higher density than UspA1. The UspA1 mutants showed a decreased C4BP binding (37.6% reduction), whereas the UspA2-deficient Moraxella mutants displayed a strongly reduced (94.6%) C4BP binding compared with the wild type. In addition, experiments with recombinantly expressed UspA150–770 and UspA230–539 showed that C4BP (range, 1–1000 nM) bound to the two proteins in a dose-dependent manner. The equilibrium constants (KD) for the UspA150–770 and UspA230–539 interactions with a single subunit of C4BP were 13 μM and 1.1 μM, respectively. The main isoform of C4BP contains seven identical α-chains and one β-chain linked together with disulfide bridges, and the α-chains contain eight complement control protein (CCP) modules. The UspA1 and A2 bound to the α-chain of C4BP, and experiments with C4BP lacking CCP2, CCP5, or CCP7 showed that these three CCPs were important for the Usp binding. Importantly, C4BP bound to the surface of M. catarrhalis retained its cofactor activity as determined by analysis of C4b degradation. Taken together, M. catarrhalis interferes with the classical complement activation pathway by binding C4BP to UspA1 and UspA2.
A Nonneutralizing Anti-HIV-1 Antibody Turns into a Neutralizing Antibody When Expressed on the Surface of HIV-1-Susceptible Cells: A New Way to Fight HIV
Authors: Lee Seung-Jae , Garza Laura , Yao Jun , Notkins Abner L. , Zhou Paul 
Published: April 2014

Abstract
During HIV-1 infection or vaccination, HIV-1 envelope spikes elicit Ab responses. Neutralizing Abs block viral entry by recognizing epitopes on spikes critical for their interaction with receptor, coreceptors or fusion. In contrast, nonneutralizing Abs fail to do so because they recognize epitopes either buried or exposed but not critical for viral entry. Previously, we produced a high-affinity human mAb against the cluster II determinant of gp41. This Ab or its recombinant Fab and single-chain Fv have been repeatedly shown to bind to HIV-1 gp160 or gp41, but fail to block viral entry. We report that, surprisingly, expression of this nonneutralizing anti-HIV-1 gp41 single-chain Fv on the surface of human CD4 T cells markedly inhibits HIV-1 replication and cell-cell fusion. The inhibition targets the HIV-1 envelope at the level of viral entry, regardless of HIV-1 tropism. Although this bona fide nonneutralizing Ab does not neutralize HIV-1 entry when produced as a soluble protein, it acts as a neutralizing Ab when expressed on the cell surface. Expressing Abs on the surface of HIV-1-susceptible cells can be a new way to fight HIV-1.
Selective Impairment of TLR-Mediated Innate Immunity in Human Newborns: Neonatal Blood Plasma Reduces Monocyte TNF-α Induction by Bacterial Lipopeptides, Lipopolysaccharide, and Imiquimod, but Preserves the Response to R-848
Authors: Levy Ofer , Zarember Kol A. , Roy Rene M. , Cywes Colette , Godowski Paul J. , Wessels Michael R. 
Published: April 2014

Abstract
Newborns are at increased risk of overwhelming infection, yet the mechanisms underlying this susceptibility are incompletely defined. In this study we report a striking 1- to 3-log decrease in sensitivity of monocytes in human neonatal cord blood, compared with monocytes in adult peripheral blood, to the TNF-α-inducing effect of multiple TLR ligands, including bacterial lipopeptides (BLPs), LPS, and the imidazoquinoline compound, imiquimod. In marked contrast, TNF-α release in response to R-848, a TLR ligand that is a congener of imiquimod, was equivalent in newborn and adult blood. Differences in ligand-induced TNF-α release correlated with divergent ligand-induced changes in monocyte TNF-α mRNA levels. Newborn and adult monocytes did not differ in basal mRNA or protein expression of TLRs or mRNA expression of functionally related molecules. Newborn monocytes demonstrated diminished LPS-induced, but equivalent R-848-induced, phosphorylation of p38 mitogen-activated protein kinase and altered BLP- and LPS-induced acute modulation of cognate receptors, suggesting that the mechanism accounting for the observed differences may be localized proximal to ligand recognition by surface TLRs. Remarkably, newborn plasma conferred substantially reduced BLP-, LPS-, and imiquimod-induced TNF-α release on adult monocytes without any effect on R-848-induced TNF-α release, reflecting differences in a plasma factor(s) distinct from soluble CD14. Impaired response to multiple TLR ligands may significantly contribute to immature neonatal immunity. Conversely, relative preservation of responses to R-848 may present unique opportunities for augmenting innate and acquired immunity in the human newborn.