bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impaired TCR-Mediated Induction of Ki67 by Naive CD4+ T Cells Is Only Occasionally Corrected by Exogenous IL-2 in HIV-1 Infection
Authors: Sieg Scott F. , Bazdar Douglas A. , Lederman Michael M. 
Published: April 2014

AbstractPerturbations in naive T cell homeostasis and function may play a major role in the immunodeficiency that accompanies HIV infection. By examining naive CD4+ T cell function on a single cell basis, we provide evidence that these cells have significant qualitative defects in HIV disease. Ki67, a molecule expressed during cell cycle progression, is induced less efficiently among naive CD4+ T cells from HIV-infected individuals following activation with anti-TCR Ab. The impairment in Ki67 expression is evident even when a separate function, CD62L down-modulation, is within normal ranges. Moreover, the defects in Ki67 induction are only sometimes corrected by the addition of rIL-2 to cell cultures. An initial assessment of IL-2 unresponsiveness in cells from selected HIV-infected individuals suggests that the defect is not a consequence of impaired IL-2R expression or IL-2R signaling capability. Qualitative defects in naive T cells that cannot be routinely corrected by IL-2 have significant implications for disease pathogenesis and for strategies using IL-2 as a vaccine adjuvant in HIV disease.
EBV-Encoded Latent Membrane Protein 1 Cooperates with BAFF/BLyS and APRIL to Induce T Cell-Independent Ig Heavy Chain Class Switching
Authors: He Bing , Raab-Traub Nancy , Casali Paolo , Cerutti Andrea 
Published: April 2014

AbstractBy substituting the H chain C region of IgM with that of IgG, IgA, or IgE, class switching enables Abs to acquire new effector functions that are crucial for the neutralization of invading pathogens. Class switching occurs through class switch DNA recombination (CSR) and usually requires engagement of CD40 on B cells by CD40 ligand on Ag-activated CD4+ T cells. CSR must be tightly regulated because abnormal IgG and IgA production favors the onset of autoimmunity, whereas increased switching to IgE leads to atopy. These inflammatory disorders can be triggered or exacerbated by EBV infection. In this study, we show that EBV induces CD40-independent CSR from Cμ to multiple downstream Cγ, Cα, and Cε genes through latent membrane protein 1 (LMP1), a CD40-like viral protein that signals in a ligand-independent fashion. LMP1-induced CSR is associated with transcriptional activation of germline Cγ, Cα, and Cε genes and triggers the up-regulation of activation-induced cytidine deaminase, a crucial component of the CSR machinery. In addition, LMP1 induces B cells to express B cell-activating factor of the TNF family and a proliferation-inducing ligand, two molecules that mediate B cell survival and T cell-independent Ab production. B cell-activating factor of the TNF family and a proliferation-inducing ligand cooperate with LMP1 to induce Ig class switching because their neutralization by appropriate soluble decoy receptors attenuates CSR in LMP1-expressing B cells. By showing that LMP1 triggers T cell-independent CSR, our findings suggest that EBV could play an important role in the pathogenesis of disorders with aberrant IgG, IgA, and/or IgE production.
Specific Signaling Pathways Triggered by IL-2 in Human Vγ9Vδ2 T Cells: An Amalgamation of NK and αβ T Cell Signaling
Authors: Lafont Virginie , Loisel Séverine , Liautard Janny , Dudal Sherri , Sablé-teychené Magali , Liautard Jean-Pierre , Favero Jean 
Published: April 2014

AbstractThe global immune response can be simplified into two components: the innate and the acquired systems. The innate immune response comprises primarily macrophages and NK cells, while B and T cells orchestrate the acquired response. Human Vγ9Vδ2 T cells represent a minor T cell subpopulation in blood (1–5%) that is activated via the TCR by small nonpeptidic molecules. Their percentage dramatically increases during the early phase of infection by intracellular pathogens, and they display many characteristics of NK cells, which places them at a unique position within the immune system. Our aim was to explore the behavior of these cells when they are activated by a receptor that is common to NK and αβ T cells, and to determine signaling pathways and biological responses induced in these cells through this receptor. Thus, we investigated whether Vγ9Vδ2 T cells behave as NK cells or as αβ T cells. We demonstrated that IL-2 activates not only STAT3, STAT5, the phosphatidylinositol 3-kinase pathway, and extracellular signal-regulated kinase-2 pathway, but also STAT4 as in NK cells, and the p38 mitogen-activated protein kinase pathway as in αβ T cells. Moreover, IL-2 induces the production of IFN-γ in Vγ9Vδ2 T cells as observed in NK cells. Due to their double profiles, Vγ9Vδ2 T cells are at the interface of the innate and the acquired immune response and may therefore not only modulate the activity of innate cells, but also influence Th1/Th2 differentiation.
Timing of IFN-β Exposure during Human Dendritic Cell Maturation and Naive Th Cell Stimulation Has Contrasting Effects on Th1 Subset Generation: A Role for IFN-β-Mediated Regulation of IL-12 Family Cytokines and IL-18 in Naive Th Cell Differentiation
Authors: Nagai Taro , Devergne Odile , Mueller Thomas F. , Perkins David L. , van Seventer Jean Maguire , van Seventer Gijs A. 
Published: April 2014

AbstractType I IFNs, IFN-α and IFN-β, are early effectors of innate immune responses against microbes that can also regulate subsequent adaptive immunity by promoting antimicrobial Th1-type responses. In contrast, the ability of IFN-β to inhibit autoimmune Th1 responses is thought to account for some of the beneficial effects of IFN-β therapy in the treatment of relapsing remitting multiple sclerosis. To understand the basis of the paradoxical effects of IFN-β on the expression of Th1-type immune responses, we developed an in vitro model of monocyte-derived dendritic cell (DC)-dependent, human naive Th cell differentiation, in which one can observe both positive and negative effects of IFN-β on the generation of Th1 cells. In this model we found that the timing of IFN-β exposure determines whether IFN-β will have a positive or a negative effect on naive Th cell differentiation into Th1 cells. Specifically, the presence of IFN-β during TNF-α-induced DC maturation strongly augments the capacity of DC to promote the generation of IFN-γ-secreting Th1 cells. In contrast, exposure to IFN-β during mature DC-mediated primary stimulation of naive Th cells has the opposite effect, in that it inhibits Th1 cell polarization and promotes the generation of an IL-10-secreting T cell subset. Studies with blocking mAbs and recombinant cytokines indicate that the mechanism by which IFN-β mediates these contrasting effects on Th1 cell generation is at least in part by differentially regulating DC expression of IL-12 family cytokines (IL-12 and/or IL-23, and IL-27) and IL-18.
Role of Complement-Binding CD21/CD19/CD81 in Enhancing Human B Cell Protection from Fas-Mediated Apoptosis
Authors: Mongini Patricia K. A. , Jackson Anna E. , Tolani Sonia , Fattah Rasem J. , Inman John K. 
Published: April 2014

AbstractDefective expression of Fas leads to B cell autoimmunity, indicating the importance of this apoptotic pathway in eliminating autoreactive B cells. However, B cells with anti-self specificities occasionally escape such regulation in individuals with intact Fas, suggesting ways of precluding this apoptosis. Here, we examine whether coligation of the B cell Ag receptor (BCR) with the complement (C3)-binding CD21/CD19/CD81 costimulatory complex can enhance the escape of human B cells from Fas-induced death. This was warranted given that BCR-initiated signals induce resistance to Fas apoptosis, some (albeit not all) BCR-triggered events are amplified by coligation of BCR and the co-stimulatory complex, and several self Ags targeted in autoimmune diseases effectively activate complement. Using a set of affinity-diverse surrogate Ags (receptor-specific mAb:dextran conjugates) with varying capacity to engage CD21, it was established that BCR:CD21 coligation lowers the BCR engagement necessary for inducing protection from Fas apoptosis. Enhanced protection was associated with altered expression of several molecules known to regulate Fas apoptosis, suggesting a unique molecular model for how BCR:CD21 coligation augments protection. BCR:CD21 coligation impairs the generation of active fragments of caspase-8 via dampened expression of membrane Fas and augmented expression of FLIPL. This, in turn, diminishes the generation of cells that would be directly triggered to apoptosis via caspase-8 cleavage of caspase 3 (type I cells). Any attempt to use the mitochondrial apoptotic protease-activating factor 1 (Apaf-1)-dependent pathway for apoptosis (as type II cells) is further blocked because BCR:CD21 coligation promotes up-regulation of the mitochondrial antiapoptotic molecule, Bcl-2.
Differential Responses to IFN-α Subtypes in Human T Cells and Dendritic Cells
Authors: Hilkens Catharien M. U. , Schlaak Jörg F. , Kerr Ian M. 
Published: April 2014

AbstractType I IFNs (IFN-αβ) constitute a family of cytokines that have important antiviral and immunoregulatory properties and have been successfully used in the treatment of a wide variety of diseases. There are 12 functional human IFN-α subtypes and one IFN-β subtype that signal through the common cell surface IFN-αβR. To date, virtually no information is available on the specificity of IFN-α responses in immune cells. In this study, Janus kinase/STAT signaling and transcriptional responses to selected IFN-α subtypes in human T cells and dendritic cells were analyzed. Evidence for IFN-α subtype and cell type specificity was found. Also, differences between kinetics of expression of IFN-stimulated genes (ISGs) and in the requirements of individual ISGs for additional signaling pathways were observed. In particular, IFN-γ-inducible protein-10 (IP-10), a key chemokine in Th1-type inflammatory diseases, was differentially regulated. In dendritic cells, it was highly induced by IFN-α2 and IFN-α21 but much less efficiently by IFN-α1. It was only marginally induced by these subtypes in T cells. In marked contrast to other ISGs analyzed, optimum induction of IP-10 was dependent on activation of p38 kinase(s). The observed variations (subtype-, cell type-, and ISG-related differentials) provide further insight into the complexity and plasticity of the IFN-αβ response. Furthermore, the novel observation that IFN-α1 poorly induces IP-10 is potentially of clinical importance, because this subtype may be more beneficial in cases where Th1-mediated side effects (e.g., exacerbation of autoimmune diseases) are not desirable.
HLA-F Surface Expression on B Cell and Monocyte Cell Lines Is Partially Independent from Tapasin and Completely Independent from TAP
Authors: Lee Ni , Geraghty Daniel E. 
Published: April 2014

AbstractIn this study we examined HLA-F expression in normal cells and cell lines, with a particular focus on identifying cells that express surface protein. While HLA-F protein was expressed in a number of diverse tissues and cell lines, including bladder, skin, and liver cell lines, no surface expression could be detected in the majority of them. However, surface expression was observed on EBV-transformed lymphoblastoid cell lines and on some monocyte cell lines. Expression on B lymphoblastoid cell lines was observed, while no surface expression on normal B cells or on any peripheral blood lymphocytes could be detected. Surface expression correlated with the presence of a limited amount of endoglycosidase H (Endo H)-resistant HLA-F. However, clearly not all surface-expressed HLA-F was fully glycosylated. We further examined the requirement of HLA-F surface expression for functional TAP and tapasin molecules and identified a clear departure from the dependence shown by other class I molecules on TAP. In contrast, of the two surface glycosylation forms expressed, an Endo H-sensitive form was tapasin independent, while an Endo H-resistant form was clearly tapasin dependent. Finally, we tested whether HLA-F could be stabilized for surface expression without peptide by using the classical cold treatment for surface stabilization of empty class I. Of several cell lines tested, only MHC deletion mutant 721.221 demonstrated a typical class I phenotype, indicating that control of surface stabilization may have a genetic basis resident in the MHC.
Separate Functional Domains of Human MD-2 Mediate Toll-Like Receptor 4-Binding and Lipopolysaccharide Responsiveness
Authors: Re Fabio , Strominger Jack L. 
Published: April 2014

AbstractCellular responses to LPS are mediated by a cell surface receptor complex consisting of Toll-like receptor 4 (TLR4), MD-2, and CD14. MD-2 is a secreted protein that interacts with the extracellular portion of TLR4. Site-directed mutagenesis was used to identify the regions of human MD-2 involved in its ability to bind TLR4 and confer LPS responsiveness. A separate region of MD-2 was found to mediate each function. MD-2 binding to TLR4 was dependent on Cys95 and Cys105, which might form an intramolecular disulfide bond. Hydrophilic and charged residues surrounding this area, such as R90, K91, D100, and Y102, also contributed to the formation of the TLR4-MD-2 complex. A different region of MD-2 was found to be responsible for conferring LPS responsiveness. This region is not involved in TLR4 binding and is rich in basic and aromatic residues, several of which cooperate for LPS responsiveness and might represent a LPS binding site. Disruption of the endogenous MD-2-TLR4 complex by expression of mutant MD-2 inhibited LPS responses in primary human endothelial cells. Thus, our data indicate that MD-2 interaction with TLR4 is necessary but not sufficient for cellular response to LPS. Either of the two functional domains of MD-2 can be disrupted to impair LPS responses and therefore represent attractive targets for therapeutic interventions.z
Human CD94 Gene Expression: Dual Promoters Differing in Responsiveness to IL-2 or IL-15
Authors: Lieto Louis D. , Borrego Francisco , You Chi-hyun , Coligan John E. 
Published: April 2014

AbstractCD94 is a C-type lectin required for the dimerization of the CD94/NKG2 family of receptors, which are expressed on NK cells and T cell subsets. Little is known about CD94 gene expression and the elements that regulate CD94 transcription. In this study, we report that CD94 gene expression is regulated by distal and proximal promoters that transcribe unique initial exons specific to each promoter. This results in two species of transcripts; the previously described CD94 mRNA and a novel CD94C mRNA. All NK cells and CD94+, CD8+ αβ T cells transcribe CD94 mRNA. Stimulation of NK and CD8+ αβ T cells with IL-2 or IL-15 induced the transcription of CD94C mRNA. The distal and proximal promoters both contain elements with IFN-γ-activated and Ets binding sites, known as GAS/EBS. Additionally, an unknown element, termed site A, was identified in the proximal promoter. EMSA analyses showed that constitutive factors could bind to oligonucleotide probes containing each element. After treatment of primary NK cells with IL-2 or IL-15, separate inducible complexes could be detected with oligonucleotide probes containing either the proximal or distal GAS/EBS elements. These elements are highly conserved between mice and humans, which suggests that both species regulate CD94 gene expression via mechanisms that predate their evolutionary divergence.
Tapasin Is a Facilitator, Not an Editor, of Class I MHC Peptide Binding
Authors: Zarling Angela L. , Luckey Chance John , Marto Jarrod A. , White Forest M. , Brame Cynthia J. , Evans Anne M. , Lehner Paul J. , Cresswell Peter , Shabanowitz Jeffrey , Hunt Donald F. , Engelhard Victor H. 
Published: April 2014

AbstractTapasin has been proposed to function as a peptide editor to displace lower affinity peptides and/or to favor the binding of high affinity peptides. Consistent with this, cell surface HLA-B8 molecules in tapasin-deficient cells were less stable and the peptide repertoire was substantially altered. However, the binding affinities of peptides expressed in the absence of tapasin were unexpectedly higher, not lower. The peptide repertoire from cells expressing soluble tapasin was similar in both appearance and affinity to that presented in the presence of full-length tapasin, but the HLA-B8 molecules showed altered cell surface stability characteristics. Similarly, the binding affinities of HLA-A*0201-associated peptides from tapasin+ and tapasin− cells were equivalent, although steady state HLA-A*0201 cell surface expression was decreased and the molecules demonstrated reduced cell surface stability on tapasin− cells. These data are inconsistent with a role for tapasin as a peptide editor. Instead, we propose that tapasin acts as a peptide facilitator. In this role, it stabilizes the peptide-free conformation of class I MHC molecules in the endoplasmic reticulum and thus increases the number and variety of peptides bound to class I MHC. Full-length tapasin then confers additional stability on class I MHC molecules that are already associated with peptides.
V(D)J Recombination Frequencies Can Be Profoundly Affected by Changes in the Spacer Sequence
Authors: Montalbano Alina , Ogwaro Kisani M. , Tang Alan , Matthews Adam G. W. , Larijani Mani , Oettinger Marjorie A. , Feeney Ann J. 
Published: April 2014

AbstractEach V, D, and J gene segment is flanked by a recombination signal sequence (RSS), composed of a conserved heptamer and nonamer separated by a 12- or 23-bp spacer. Variations from consensus in the heptamer or nonamer at specific positions can dramatically affect recombination frequency, but until recently, it had been generally held that only the length of the spacer, but not its sequence, affects the efficacy of V(D)J recombination. In this study, we show several examples in which the spacer sequence can significantly affect recombination frequencies. We show that the difference in spacer sequence alone of two VHS107 genes affects recombination frequency in recombination substrates to a similar extent as the bias observed in vivo. We show that individual positions in the spacer can affect recombination frequency, and those positions can often be predicted by their frequency in a database of RSS. Importantly, we further show that a spacer sequence that has an infrequently observed nucleotide at each position is essentially unable to support recombination in an extrachromosmal substrate assay, despite being flanked by a consensus heptamer and nonamer. This infrequent spacer sequence RSS shows only a 2-fold reduction of binding of RAG proteins, but the in vitro cleavage of this RSS is ∼9-fold reduced compared with a good RSS. These data demonstrate that the spacer sequence should be considered to play an important role in the recombination efficacy of an RSS, and that the effect of the spacer occurs primarily subsequent to RAG binding.
Two Novel Fully Functional Isoforms of CX3CR1 Are Potent HIV Coreceptors
Authors: Garin Alexandre , Tarantino Nadine , Faure Sophie , Daoudi Mehdi , Lécureuil Cédric , Bourdais Anne , Debré Patrice , Deterre Philippe , Combadiere Christophe 
Published: April 2014

AbstractWe identified two novel isoforms of the human chemokine receptor CX3CR1, produced by alternative splicing and with N-terminal regions extended by 7 and 32 aa. Expression of the messengers coding these isoforms, compared with that of previously described V28 messengers, is lower in monocytes and NK cells, but higher in CD4+ T lymphocytes. CX3CR1 and its extended isoforms were expressed in HEK-293 cells and compared for expression, ligand binding, and cellular responses. In steady state experiments, all three CX3CR1 isoforms bound CX3CL1 with similar affinity. In kinetic binding studies, however, kon and koff were significantly greater for the extended CX3CR1 isoforms, thereby suggesting that the N-terminal extensions may alter the functions induced by CX3CL1. In signaling studies, all three CX3CR1 isoforms mediated agonist-dependent calcium mobilization, but the EC50 was lower for the extended than for the standard isoforms. In addition, chemotactic responses for these extended isoforms shifted left, also indicating a more sensitive response. Finally, the longer variants appeared to be more potent HIV coreceptors when tested in fusion and infection assays. In conclusion, we identified and characterized functionally two novel isoforms of CX3CR1 that respond more sensitively to CX3CL1 and HIV viral envelopes. These data reveal new complexity in CX3CR1 cell activation and confirm the critical role of the N-terminal domain of the chemokine receptors in ligand recognition and cellular response.
STAT-1α and IFN-γ as Modulators of TNF-α Signaling in Macrophages: Regulation and Functional Implications of the TNF Receptor 1:STAT-1α Complex
Authors: Wesemann Duane R. , Benveniste Etty N. 
Published: April 2014

AbstractTNF-α and IFN-γ cooperate in the activation of macrophages. TNF-α-dependent activation of NF-κB is stronger in the presence of IFN-γ. STAT-1α associates with TNFR1 in TNF-α-treated cells, and this association attenuates TNF-α-mediated NF-κB activation. We hypothesized that nuclear localization of STAT-1α due to IFN-γ signaling would preclude it from being recruited to the TNFR1 and therefore enhance TNF-α-induced NF-κB activation. In the RAW264.7 macrophage cell line, TNF-α treatment indeed recruits STAT-1α to the TNFR1, and this association is abrogated when cells are exposed to IFN-γ. TNF-α treatment induces a more robust activation of NF-κB in STAT-1α-deficient cells, and restoration of STAT-1α inhibits TNF-α-dependent NF-κB activation. Our results suggest that a receptor-proximal level of cross-talk exists between these two cytokine pathways: IFN-γ limits STAT-1α availability to the TNFR1 by depleting STAT-1α from the cytoplasm, thus allowing for optimal NF-κB activation upon TNF-α ligation.
Neuronal Calcium Sensor-1 and Phosphatidylinositol 4-Kinase β Regulate IgE Receptor-Triggered Exocytosis in Cultured Mast Cells
Authors: Kapp-Barnea Yaara , Melnikov Semyon , Shefler Irit , Jeromin Andreas , Sagi-Eisenberg Ronit 
Published: April 2014

Abstract
We examined the possible occurrence and function of neuronal Ca2+ sensor 1 (NCS-1/frequenin) in the mast cell line rat basophilic leukemia, RBL-2H3. This protein has been implicated in the control of neurosecretion from dense core granules in neuronal cells as well as in the control of constitutive secretory pathways in both yeast and mammalian cells. We show that RBL-2H3 cells, secretory cells of the immune system, endogenously express the 22-kDa NCS-1 protein as well as an immune-related 50-kDa protein. Both proteins associate in vivo with phosphatidylinositol 4-kinase β (PI4Kβ) and colocalize with the enzyme in the Golgi region. We show further that overexpression of NCS-1 in RBL-2H3 cells stimulates the catalytic activity of PI4Kβ, increases IgE receptor (FcεRI)-triggered hydrolysis of phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2), and stimulates FcεRI-triggered, but not Ca2+ ionophore-triggered, exocytosis. Conversely, expression of a kinase-dead mutant of PI4Kβ reduces PI4Kβ activity, decreases FcεRI-stimulated phosphatidylinositol 4,5-bisphosphate hydrolysis, and blocks FcεRI-triggered, but not Ca2+ ionophore-triggered, exocytosis. Our results indicate that PI(4)P, produced by the Golgi-localized PI4Kβ, is the rate-limiting factor in the synthesis of the pool of PI(4,5)P2 that serves as substrate for the generation of lipid-derived second messengers in FcεRI-triggered cells. We conclude that NCS-1 is involved in the control of regulated exocytosis in nonneural cells, where it contributes to stimulus-secretion coupling by interacting with PI4Kβ and positive regulation of its activity.