bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cutting Edge: Influence of the TCR Vβ Domain on the Avidity of CD1d:α-Galactosylceramide Binding by Invariant Vα14 NKT Cells
Authors: Schümann Jens , Voyle Roger B. , Wei Bing-Yuan , MacDonald H. Robson 
Published: April 2014

Abstract
CD1d tetramers loaded with α-galactosylceramide (α-GalCer) bind selectively to mouse invariant Vα14 (Vα14i) NKT cells and their human counterparts. Whereas tetramer binding strictly depends on the expression of a Vα14-Jα18 chain in murine NKT cells, the associated β-chain (typically expressing Vβ8.2 or Vβ7) appears not to influence tetramer binding. In this study, we describe novel α-GalCer-loaded mouse and human CD1d-IgG1 dimers, which revealed an unexpected influence of the TCR-β chain on the avidity of CD1d:α-GalCer binding. A subset of Vα14i NKT cells clearly discriminated α-GalCer bound to mouse or human CD1d on the basis of avidity differences conferred by the Vβ domain of the TCR-β chain, with Vβ8.2 conferring higher avidity binding than Vβ7.
Tapasin−/− and TAP1−/− Macrophages Are Deficient in Vacuolar Alternate Class I MHC (MHC-I) Processing due to Decreased MHC-I Stability at Phagolysosomal pH
Authors: Chefalo Peter J. , Grandea Andres G. , Van Kaer Luc , Harding Clifford V. 
Published: April 2014

AbstractAlternate class I MHC (MHC-I) Ag processing via cytosolic or vacuolar pathways leads to cross-presentation of exogenous Ag to CD8 T cells. Vacuolar alternate MHC-I processing involves phagolysosomal Ag proteolysis and peptide binding to MHC-I in post-Golgi compartments. We report the first study of alternate MHC-I Ag processing in tapasin−/− cells and experiments with tapasin−/− and TAP1−/− macrophages that characterize alternate MHC-I processing. Tapasin promotes retention of MHC-I in the endoplasmic reticulum (ER) for loading with high affinity peptides, whereas tapasin−/− cells allow poorly loaded MHC-I molecules to exit the ER. Hypothetically, we considered that a large proportion of post-Golgi MHC-I on tapasin−/− cells might be peptide-receptive, enhancing alternate MHC-I processing. In contrast, alternate MHC-I processing was diminished in both tapasin−/− and TAP1−/− macrophages. Nonetheless, these cells efficiently presented exogenous peptide, suggesting a loss of MHC-I stability or function specific to vacuolar processing compartments. Tapasin−/− and TAP1−/− macrophages had decreased MHC-I stability and increased susceptibility of MHC-I to inactivation by acidic conditions (correlating with vacuolar pH). Incubation of tapasin−/− or TAP1−/− cells at 26°C decreased susceptibility of MHC-I to acid pH and reversed the deficiency in alternate MHC-I processing. Thus, tapasin and TAP are required for MHC-I to bind ER-derived stabilizing peptides to achieve the stability needed for alternate MHC-I processing via peptide exchange in acidic vacuolar processing compartments. Acidic pH destabilizes MHC-I, but also promotes peptide exchange, thereby enhancing alternate MHC-I Ag processing. These results are consistent with alternate MHC-I Ag processing mechanisms that involve binding of peptides to MHC-I within acidic vacuolar compartments.
Paxillin Binding to the α4 Integrin Subunit Stimulates LFA-1 (Integrin αLβ2)-Dependent T Cell Migration by Augmenting the Activation of Focal Adhesion Kinase/Proline-Rich Tyrosine Kinase-2
Authors: Rose David M. , Liu Shouchun , Woodside Darren G. , Han Jaewon , Schlaepfer David D. , Ginsberg Mark H. 
Published: April 2014

Abstract
Engagement of very late Ag-4 (integrin α4β1) by ligands such as VCAM-1 markedly stimulates leukocyte migration mediated by LFA-1 (integrin αLβ2). This form of integrin trans-regulation in T cells requires the binding of paxillin to the α4 integrin cytoplasmic domain. This conclusion is based on the abolition of trans-regulation in Jurkat T cells by an α4 mutation (α4(Y991A)) that disrupts paxillin binding. Furthermore, cellular expression of an α4-binding fragment of paxillin that blocks the α4-paxillin interaction, selectively blocked VCAM-1 stimulation of αLβ2-dependent cell migration. The α4-paxillin association mediates trans-regulation by enhancing the activation of tyrosine kinases, focal adhesion kinase (FAK) and/or proline-rich tyrosine kinase-2 (Pyk2), based on two lines of evidence. First, disruption of the paxillin-binding site in the α4 tail resulted in much less α4β1-mediated phosphorylation of Pyk2 and FAK. Second, transfection with cDNAs encoding C-terminal fragments of Pyk2 and FAK, which block the function of the intact kinases, blocked α4β1 stimulation of αLβ2-dependent migration. These results define a proximal protein-protein interaction of an integrin cytoplasmic domain required for trans-regulation between integrins, and establish that augmented activation of Pyk2 and/or FAK is an immediate signaling event required for the trans-regulation of integrin αLβ2 by α4β1.
Deleterious Effect of HIV-1 Plasma Viremia on B Cell Costimulatory Function
Authors: Malaspina Angela , Moir Susan , Kottilil Shyamasundaran , Hallahan Claire W. , Ehler Linda A. , Liu Shuying , Planta Marie A. , Chun Tae-Wook , Fauci Anthony S. 
Published: April 2014

Abstract
HIV infection leads to numerous immunologic defects, including impaired B cell function. An effective humoral response requires bidirectional interactions between B cells and CD4+ T cells, critical of which are interactions between CD80/CD86 expressed on activated B cells and CD28 expressed on responder CD4+ T cells. In the present study, we examined the effect of active HIV replication on B cell costimulatory function. Induction of CD80/CD86 on B cells following B cell receptor and CD40 triggering and responsiveness of CD4+ T cells to activated B cells were investigated in a system where B cells of HIV-infected patients were compared concurrently to B cells of HIV-negative donors. In contrast to HIV-aviremic patients, B cells of HIV-viremic patients were ineffective at stimulating CD4+ T cells, as measured by the induction of activation markers and proliferation. The importance of interactions of CD80/CD86 and CD28 in activating CD4+ T cells was clear; the ablation of a normal response following the addition of neutralizing anti-CD86/CD80 Abs mirrored the response of CD4+ T cells to B cells of HIV-viremic patients, while the addition of exogenous CD28 ligands partially restored the poor CD4+ T cell response to the B cells of HIV-viremic patients. Ineffective B cell costimulatory function in HIV-viremic patients was associated with low induction of CD80/CD86 expression on B cells. Our findings further delineate the scope of defects associated with cognate B cell-CD4+ T cell interactions in HIV infection and suggest that therapeutic interventions designed to enhance CD28-dependent costimulatory pathways may help restore immune functions.
Suppression of T Cell Signaling by Polyunsaturated Fatty Acids: Selectivity in Inhibition of Mitogen-Activated Protein Kinase and Nuclear Factor Activation
Authors: Zeyda Maximilian , Szekeres Andreas B. , Säemann Marcus D. , Geyeregger René , Stockinger Hannes , Zlabinger Gerhard J. , Waldhäusl Werner , Stulnig Thomas M. 
Published: April 2014

AbstractPolyunsaturated fatty acids (PUFAs) are known to suppress inflammatory and autoimmune responses and, therefore, clinical applications of PUFAs as immunomodulatory substances are extensively studied. PUFAs are known to inhibit T cell responses, but with respect to TCR/CD3-mediated signal transduction only a block in CD3-induced phospholipase Cγ1/calcium signaling has been shown so far. In this study, we investigated PUFA-mediated changes in downstream T cell signal transduction. We show that among the mitogen-activated protein kinase families activation of c-Jun NH2-terminal kinase, but not phosphorylation of extracellular signal-regulated kinase-1/-2 or p38 is inhibited. CD3/CD28-induced activity of NF-AT was markedly reduced by PUFA treatment, while activation of other nuclear receptors (AP-1 and NF-κB) remained unaltered. Furthermore, IL-2 promoter activity, IL-2 and IL-13 mRNA levels, IL-2 secretion, and IL-2R α-chain expression were significantly diminished by PUFA treatment, whereas the expression of IFN-γ, IL-4, IL-10, and CD69 remained essentially unaffected by PUFAs. In conclusion, PUFA treatment of T cells inhibits selectively c-Jun NH2-terminal kinase and NF-AT activation, resulting in diminished production of IL-2 and IL-13.
Immunologically Induced, Complement-Dependent Up-Regulation of the Prion Protein in the Mouse Spleen: Follicular Dendritic Cells Versus Capsule and Trabeculae
Authors: Lötscher Marius , Recher Mike , Hunziker Lukas , Klein Michael A. 
Published: April 2014

Abstract
The expression of the prion protein (PrP) in the follicular dendritic cell network of germinal centers in the spleen is critical for the splenic propagation of the causative agent of prion diseases. However, a physiological role of the prion protein in the periphery remains elusive. To investigate the role and function of PrP expression in the lymphoid system we treated naive mice i.v. with preformed immune complexes or vesicular stomatitis virus. Immunohistochemistry and Western blot analysis of the spleen revealed that 8 days after immunization, immune complexes and vesicular stomatitis virus had both induced a strong increase of PrP expression in the follicular dendritic cell network. Remarkably, this up-regulation did not occur in mice that lack an early factor of the complement cascade, C1q, a component which has been shown previously to facilitate early prion pathogenesis. In addition to the variable PrP level in the germinal centers, we detected steady and abundant PrP expression in the splenic capsule and trabeculae, which are structural elements that have not been associated before with PrP localization. The abundant trabeculo-capsular PrP expression was also evident in spleens of Rag-1-deficient mice, which have been shown before to be incapable of prion expansion. We conclude that trabeculocapsular PrP is not sufficient for splenic prion propagation. Furthermore, our observations may provide important clues for a physiological function of the prion protein and allow a new view on the role of complement and PrP in peripheral prion pathogenesis.
Functional Epitope on Human Neutrophil Flavocytochrome b558
Authors: Burritt James B. , Foubert Thomas R. , Baniulis Danas , Lord Connie I. , Taylor Ross M. , Mills John S. , Baughan Travis D. , Roos Dirk , Parkos Charles A. , Jesaitis Algirdas J. 
Published: April 2014

Abstract
mAb NL7 was raised against purified flavocytochrome b558, important in host defense and inflammation. NL7 recognized the gp91phox flavocytochrome b558 subunit by immunoblot and bound to permeabilized neutrophils and neutrophil membranes. Epitope mapping by phage display analysis indicated that NL7 binds the 498EKDVITGLK506 region of gp91phox. In a cell-free assay, NL7 inhibited in vitro activation of the NADPH oxidase in a concentration-dependent manner, and had marginal effects on the oxidase substrate Michaelis constant (Km). mAb NL7 did not inhibit translocation of p47phox, p67phox, or Rac to the plasma membrane, and bound its epitope on gp91phox independently of cytosolic factor translocation. However, after assembly of the NADPH oxidase complex, mAb NL7 bound the epitope but did not inhibit the generation of superoxide. Three-dimensional modeling of the C-terminal domain of gp91phox on a corn nitrate reductase template suggests close proximity of the NL7 epitope to the proposed NADPH binding site, but significant separation from the proposed p47phox binding sites. We conclude that the 498EKDVITGLK506 segment resides on the cytosolic surface of gp91phox and represents a region important for oxidase function, but not substrate or cytosolic component binding.
Biochemical Features of the MHC-Related Protein 1 Consistent with an Immunological Function
Authors: Miley Michael J. , Truscott Steven M. , Yu Yik Yeung Lawrence , Gilfillan Susan , Fremont Daved H. , Hansen Ted H. , Lybarger Lonnie 
Published: April 2014

Abstract
MHC-related protein (MR)1 is an MHC class I-related molecule encoded on chromosome 1 that is highly conserved among mammals and is more closely related to classical class I molecules than are other nonclassical class I family members. In this report, we show for the first time that both mouse and human MR1 molecules can associate with the peptide-loading complex and can be detected at low levels at the surface of transfected cells. We also report the production of recombinant human MR1 molecules in insect cells using highly supplemented media and provide evidence that the MR1 H chain can assume a folded conformation and is stoichiometrically associated with β2-microglobulin, similar to class I molecules. Cumulatively, these findings demonstrate that surface expression of MR1 is possible but may be limited by a specific ligand or associated molecule.
Structure-Function Relationships of Human C5a and C5aR
Authors: Huber-Lang Markus S. , Sarma J. Vidya , McGuire Stephanie R. , Lu Kristina T. , Padgaonkar Vaishalee A. , Younkin Ellen M. , Guo Ren Feng , Weber Christian H. , Zuiderweg Erik R. , Zetoune Firas S. , Ward Peter A. 
Published: April 2014

AbstractUsing peptides that represent linear regions of the powerful complement activation product, C5a, or loops that connect the four α helices of C5a, we have defined the ability of these peptides to reduce binding of 125I-C5a to human neutrophils, inhibit chemotactic responses of neutrophils to C5a, and reduce H2O2 production in neutrophils stimulated with PMA. The data have defined likely sites of interaction of C5a with C5aR. The peptides had no functional activity per se on neutrophils and did not interfere with neutrophil responses to the unrelated chemotactic peptide, N-formyl-Met-Leu-Phe. Although previous data have suggested that there are two separate sites on C5a reactive with C5aR, the current data suggest that C5a interacts with C5aR in a manner that engages three discontinuous regions of C5a.
A Role for Macrophage Inflammatory Protein-3α/CC Chemokine Ligand 20 in Immune Priming During T Cell-Mediated Inflammation of the Central Nervous System
Authors: Kohler Rachel E. , Caon Adriana C. , Willenborg David O. , Clark-Lewis Ian , McColl Shaun R. 
Published: April 2014

AbstractChemokines are a family of cytokines that exhibit selective chemoattractant properties for target leukocytes and play a significant role in leukocyte migration. In this study, we have investigated the role of the C-C chemokine, macrophage inflammatory protein (MIP)-3α/CC chemokine ligand 20, in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), a model of T cell-dependent inflammation. Expression in the CNS of MIP-3α, as determined by RT-PCR, increased in a time-dependent manner such that peak expression correlated with peak clinical disease. Similarly, levels of immunoreactive MIP-3α in the draining lymph nodes increased up to 10-fold 9 days postimmunization and remained elevated for up to 21 days postimmunization. The increased production of MIP-3α coincided with onset of clinical disease. Treatment of mice with specific neutralizing anti-MIP-3α Abs significantly reduced the severity of both clinical EAE and neuroinflammation by inhibiting the sensitization of lymphocytes to the specific Ag and release of lymphocytes from the draining lymph nodes. In contrast, adoptive transfer experiments indicated that MIP-3α was not essential for the effector phase of EAE. Together, these data demonstrate that MIP-3α plays a critical role in the sensitization phase of EAE.
Coordinate Regulation of IFN Consensus Sequence-Binding Protein and Caspase-1 in the Sensitization of Human Colon Carcinoma Cells to Fas-Mediated Apoptosis by IFN-γ
Authors: Liu Kebin , Abrams Scott I. 
Published: April 2014

Abstract
Interferon-γ is thought to be essential for the regulation of antitumor reactions. However, the degree of responsiveness of malignant cells to IFN-γ may have a profound influence on the overall efficacy of an antitumor response. In this study, we examined the molecular basis by which IFN-γ differentially sensitized human primary and metastatic colon carcinoma cells to Fas-mediated apoptosis. To that end, we analyzed IFN-γ-induced gene expression at the genome scale, followed by an analysis of the expression and function of specific genes associated with IFN-γ- and Fas-mediated signaling. We found that although both cell populations exhibited a similar gene expression profile at the genome scale in response to IFN-γ, the expression intensities of the IFN-γ-regulated genes were much greater in the primary tumor. Noteworthily, two genes, one involved in IFN-γ-mediated signaling, IFN consensus sequence-binding protein (ICSBP), and one involved in Fas-mediated signaling, caspase-1, were clearly shown to be differentially induced between the two cell lines. In the primary tumor cells, the expression of ICSBP and caspase-1 was strongly induced in response to IFN-γ, whereas they were weakly to nondetectable in the metastatic tumor cells. Functional studies demonstrated that both caspase-1 and ICSBP were involved in Fas-mediated apoptosis following IFN-γ sensitization, but proceeded via two distinct pathways. This study also reports for the first time the expression of ICSBP in a nonhemopoietic tumor exhibiting proapoptotic properties. Overall, in a human colon carcinoma cell model, we identified important functional contributions of two IFN-γ-regulated genes, ICSBP and caspase-1, in the mechanism of Fas-mediated death.
Intrinsic Differences in the Proliferation of Naive and Memory Human B Cells as a Mechanism for Enhanced Secondary Immune Responses
Authors: Tangye Stuart G. , Avery Danielle T. , Deenick Elissa K. , Hodgkin Philip D. 
Published: April 2014

AbstractHumoral immune responses elicited after secondary exposure to immunizing Ag are characterized by robust and elevated reactivity of memory B cells that exceed those of naive B cells during the primary response. The mechanism underlying this difference in responsiveness of naive vs memory B cells remains unclear. We have quantitated the response of naive and memory human B cells after in vitro stimulation with T cell-derived stimuli. In response to stimulation with CD40 ligand alone or with IL-10, both IgM-expressing and Ig isotype-switched memory B cells entered their first division 20–30 h earlier than did naive B cells. In contrast, the time spent traversing subsequent divisions was similar. Consistent with previous studies, only memory cells differentiated to CD38+ blasts in a manner that increased with consecutive division number. These differentiated CD38+ B cells divided faster than did CD38− memory B cell blasts. Proliferation of CD40 ligand-stimulated naive B cells as well as both CD38+ and CD38− cells present in cultures of memory B cells was increased by IL-10. In contrast, IL-2 enhanced proliferation of CD38− and CD38+ memory B cell blasts, but not naive cells. Thus, memory B cells possess an intrinsic advantage over naive B cells in both the time to initiate a response and in the division-based rate of effector cell development. These differences help explain the accelerated Ab response exhibited by memory B cells after secondary challenge by an invading pathogen, a hallmark of immunological memory.
The Intracellular Granzyme B Inhibitor, Proteinase Inhibitor 9, Is Up-Regulated During Accessory Cell Maturation and Effector Cell Degranulation, and Its Overexpression Enhances CTL Potency
Authors: Hirst Claire E. , Buzza Marguerite S. , Bird Catherina H. , Warren Hilary S. , Cameron Paul U. , Zhang Manling , Ashton-Rickardt Philip G. , Bird Phillip I. 
Published: April 2014

AbstractGranzyme B (grB) is a serine proteinase released by cytotoxic lymphocytes (CLs) to kill abnormal cells. GrB-mediated apoptotic pathways are conserved in nucleated cells; hence, CLs require mechanisms to protect against ectopic or misdirected grB. The nucleocytoplasmic serpin, proteinase inhibitor 9 (PI-9), is a potent inhibitor of grB that protects cells from grB-mediated apoptosis in model systems. Here we show that PI-9 is present in CD4+ cells, CD8+ T cells, NK cells, and at lower levels in B cells and myeloid cells. PI-9 is up-regulated in response to grB production and degranulation, and associates with grB-containing granules in activated CTLs and NK cells. Intracellular complexes of PI-9 and grB are evident in NK cells, and overexpression of PI-9 enhances CTL potency, suggesting that cytoplasmic grB, which may threaten CL viability, is rapidly inactivated by PI-9. Because dendritic cells (DCs) acquire characteristics similar to those of target cells to activate naive CD8+ T cells and therefore may also require protection against grB, we investigated the expression of PI-9 in DCs. PI-9 is evident in thymic DCs (CD3−, CD4+, CD8−, CD45+), tonsillar DCs, and DC subsets purified from peripheral blood (CD16+ monocytes and CD123+ plasmacytoid DCs). Furthermore, PI-9 is expressed in monocyte-derived DCs and is up-regulated upon TNF-α-induced maturation of monocyte-derived DCs. In conclusion, the presence and subcellular localization of PI-9 in leukocytes and DCs are consistent with a protective role against ectopic or misdirected grB during an immune response.
IFN-γ Production Is Specifically Regulated by IL-10 in Mice Made Tolerant with Anti-CD40 Ligand Antibody and Intact Active Bone
Authors: Yin Dengping , Dujovny Nadav , Ma Lianli , Varghese Anncy , Shen JiKun , Bishop D. Keith , Chong Anita S. 
Published: April 2014

AbstractWe have developed a strategy to induce tolerance to allografts, involving cotransplantation of allogeneic intact active bone and transient anti-CD40 ligand mAb therapy. Tolerance induced by this approach in C57BL/6 mice receiving BALB/c hearts is not mediated by deletional mechanisms, but by peripheral regulatory mechanisms. Tolerance is associated with diminished ex vivo IFN-γ production that is donor specific, and a reduction in the frequency of IFN-γ-producing cells. Splenocytes from mice tolerant to BALB/c grafts, but sensitized to third-party C3H skin grafts, demonstrated normally primed ex vivo IFN-γ responses to C3H stimulators. Neutralizing anti-IL-10 and anti-IL-10R, but not anti-TGF-β, anti-IL-4, or anti-CTLA-4, Abs restored the ex vivo IFN-γ response to BALB/c stimulators. There was no significant difference in IL-2 or IL-4 production between tolerant and rejecting mice, and anti-IL-10 mAbs had no effect on IL-2 or IL-4 production. The Cincinnati cytokine capture assay was used to test whether suppression of IFN-γ production in vivo was also a marker of tolerance. In naive mice, we observed a dramatic increase in serum IFN-γ levels following challenge with allogeneic BALB/c splenocytes or hearts. Tolerant mice challenged with allogeneic BALB/c splenocytes or hearts made significantly less or undetectable amounts of IFN-γ. No IL-4 or IL-10 production was detected in tolerant or rejecting mice. Collectively, our studies suggest that active suppression of IFN-γ production by IL-10 is correlated with, and may contribute to, tolerance induced with intact active bone and anti-CD40 ligand mAbs.