bluuebunny/crossref_metadata_2025 huggingface dataset:
Activation of Toll-Like Receptor 2 on Human Tracheobronchial Epithelial Cells Induces the Antimicrobial Peptide Human β Defensin-2
Authors: Hertz Cheryl J. , Wu Qi , Porter Edith Martin , Zhang Yan J. , Weismüller Karl-Heinz , Godowski Paul J. , Ganz Tomas , Randell Scott H. , Modlin Robert L.
Published: April 2014

As pattern recognition receptors capable of eliciting responses to a diverse array of microbial products, Toll-like receptors (TLRs) participate in the activation of host defense mechanisms that protect against infectious pathogens. Given that epithelial cells lie at the interface between the host and its environment, we designed experiments to determine whether human airway epithelial cells express TLRs and respond to TLR agonists. Immunohistochemical labeling of TLR2 in normal human airways revealed TLR2 expression throughout the epithelium, with an apparently higher level of expression on noncolumnar basal epithelial cells. Two-color immunofluorescent labeling of TLR2 and cytokeratins 8 and 15 revealed that TLR2 is coexpressed with the epithelial cell markers. In addition, airway epithelial cells grown at air-liquid interface responded to bacterial lipopeptide in a TLR2-dependent manner with induction of mRNA and protein of the antimicrobial peptide human β defensin-2. Stimulation of epithelial cell cultures with lipopeptide resulted in a small and variable reduction of bacteria on the apical surface. Together, these data suggest that TLRs monitor epithelial surfaces to enhance host defense by inducing the production of an antimicrobial peptide.
Reduced Inflammation and Tissue Damage in Transgenic Rabbits Overexpressing 15-Lipoxygenase and Endogenous Anti-inflammatory Lipid Mediators
Authors: Serhan Charles N. , Jain Ashish , Marleau Sylvie , Clish Clary , Kantarci Alpdogan , Behbehani Balsam , Colgan Sean P. , Stahl Gregory L. , Merched Aksam , Petasis Nicos A. , Chan Lawrence , Van Dyke Thomas E.
Published: April 2014

PGs and leukotrienes (LTs) mediate cardinal signs of inflammation; hence, their enzymes are targets of current anti-inflammatory therapies. Products of arachidonate 15-lipoxygenases (LO) types I and II display both beneficial roles, such as lipoxins (LXs) that stereoselectively signal counterregulation, as well as potential deleterious actions (i.e., nonspecific phospholipid degradation). In this study, we examined transgenic (TG) rabbits overexpressing 15-LO type I and their response to inflammatory challenge. Skin challenges with either LTB4 or IL-8 showed that 15-LO TG rabbits give markedly reduced neutrophil (PMN) recruitment and plasma leakage at dermal sites with LTB4. PMN from TG rabbits also exhibited a dramatic reduction in LTB4-stimulated granular mobilization that was not evident with peptide chemoattractants. Leukocytes from 15-LO TG rabbits gave enhanced LX production, underscoring differences in lipid mediator profiles compared with non-TG rabbits. Microbe-associated inflammation and leukocyte-mediated bone destruction were assessed by initiating acute periodontitis. 15-LO TG rabbits exhibited markedly reduced bone loss and local inflammation. Because enhanced LX production was associated with an increased anti-inflammatory status of 15-LO TG rabbits, a stable analog of 5S,6R,15S-trihydroxyeicosa-7E,9E,11Z,13E-tetraenoic acid (LXA4) was applied to the gingival crevice subject to periodontitis. Topical application with the 15-epi-16-phenoxy-para-fluoro-LXA4 stable analog (ATLa) dramatically reduced leukocyte infiltration, ensuing bone loss as well as inflammation. These results indicate that overexpression of 15-LO type I and LXA4 is associated with dampened PMN-mediated tissue degradation and bone loss, suggesting that enhanced anti-inflammation status is an active process. Moreover, they suggest that LXs can be targets for novel approaches to diseases, e.g., periodontitis and arthritis, where inflammation and bone destruction are features.
IL-12 p40 Homodimer-Dependent Macrophage Chemotaxis and Respiratory Viral Inflammation Are Mediated through IL-12 Receptor β1
Authors: Russell Tonya D. , Yan Qingyun , Fan Guangshun , Khalifah Anthony P. , Bishop D. Keith , Brody Steven L. , Walter Michael J.
Published: April 2014

Leukocyte recruitment to the airway lumen is a central feature of inflammatory conditions such as asthma and respiratory viral infection. Characterization of mediators that regulate leukocyte recruitment in these conditions revealed increased IL-12 p40 homodimer (p80) levels were associated with enhanced airway macrophage accumulation. To examine this association, we used in vivo and in vitro assays to demonstrate p80, but not IL-12 or p40, provided a macrophage chemoattractant signal. Macrophages from genetically deficient mice indicated p80-dependent chemotaxis was independent of IL-12 and required IL-12Rβ1 (Rβ1) expression. Furthermore, analysis of murine cell lines and primary culture macrophages revealed Rβ1 expression, with an intact cytoplasmic tail, was necessary and sufficient to mediate p80-dependent chemotaxis. To examine the role for Rβ1 in mediating macrophage accumulation in vivo, we contrasted Sendai virus-driven airway inflammation in wild-type and Rβ1-deficient mice. Despite similar viral burden and production of the macrophage chemoattractant p80, the Rβ1-deficient mice displayed a selective decrease in airway macrophage accumulation and resistance to viral-dependent mortality. Thus, Rβ1 mediates p80-dependent macrophage chemotaxis and inhibition of the p80-Rβ1 interaction may provide a novel anti-inflammatory strategy to manipulate the inflammation associated with asthma and respiratory viral infection.
Blocking the Monocyte Chemoattractant Protein-1/CCR2 Chemokine Pathway Induces Permanent Survival of Islet Allografts through a Programmed Death-1 Ligand-1-Dependent Mechanism
Authors: Lee Iris , Wang Liqing , Wells Andrew D. , Ye Qunrui , Han Rongxiang , Dorf Martin E. , Kuziel William A. , Rollins Barrett J. , Chen Lieping , Hancock Wayne W.
Published: April 2014

Islet allografts are subject to rapid rejection through host cellular immune responses involving mononuclear cell recruitment and tissue injury. Interruption of leukocyte recruitment through chemokine receptor targeting is of therapeutic benefit in various experimental models, but little is known about the contribution of chemokine pathways to islet allograft rejection. We found that murine islets produce monocyte chemoattractant protein-1 (MCP-1; CCL2) in vitro and that islet allograft rejection was associated with intragraft expression of MCP-1 and its receptor, CCR2. We therefore investigated whether MCP-1 and CCR2 are required for the rejection of fully MHC-disparate islet allografts. Wild-type mice treated with blocking anti-MCP-1 mAb plus a brief, subtherapeutic course of rapamycin had long-term islet allograft survival, in contrast to the effect of treatment with either mAb or rapamycin alone. CCR2−/− mice treated with rapamycin also maintained islet allografts long-term. Both MCP/CCR2- and rapamycin-sensitive signals were required for maximal proliferation of alloreactive T cells, suggesting that MCP-1/CCR2 induce rejection by promoting alloreactive T cell clonal expansion and homing and migration. Prolonged islet allograft survival achieved by blockade of the MCP-1/CCR2 pathway plus rapamycin therapy was accompanied by a mononuclear cell infiltrate expressing the inhibitory receptor, programmed death-1 (PD-1), and its ligand (PD-L1, B7-H1), and prolongation of islet allograft survival was abrogated by anti-PD-L1 mAb therapy. These data show that the blockade of MCP-1 binding to CCR2 in conjunction with subtherapeutic immunosuppression can have profound effects on islet allograft survival and implicate the expression of the PD-1/PD-L1 pathway in the regulation of physiologic responses in vivo.
Macrophages of the Splenic Marginal Zone Are Essential for Trapping of Blood-Borne Particulate Antigen but Dispensable for Induction of Specific T Cell Responses
Authors: Aichele Peter , Zinke Jana , Grode Leander , Schwendener Reto A. , Kaufmann Stefan H. E. , Seiler Peter
Published: April 2014

Rapid removal of pathogens from the circulation by secondary lymphoid organs is prerequisite for successful control of infection. Blood-borne Ags are trapped mainly in the splenic marginal zone. To identify the cell populations responsible for Ag trapping in the marginal zone, mice were selectively depleted of marginal zone macrophages and marginal metallophilic macrophages. In the absence of these cells, trapping of microspheres and Listeria monocytogenes organisms was lost, and early control of infection was impaired. Depletion of marginal zone macrophages and marginal metallophilic macrophages, however, did not limit Ag presentation because Listeria-specific protective T cell immunity was induced. Therefore, marginal zone macrophages and marginal metallophilic macrophages are crucial for trapping of particulate Ag but dispensable for Ag presentation.
IL-18 Binding Protein Protects Against Contact Hypersensitivity
Authors: Plitz Thomas , Saint-Mézard Pierre , Satho Masataka , Herren Susanne , Waltzinger Caroline , de Carvalho Bittencourt Marcelo , Kosco-Vilbois Marie H. , Chvatchko Yolande
Published: April 2014

Allergic contact dermatitis, the clinical manifestation of contact hypersensitivity, is one of the most common disorders of the skin. It is elicited upon multiple cutaneous re-exposure of sensitized individuals to the sensitizing agent. In this study, we demonstrate that using IL-18 binding protein (IL-18BP) to neutralize IL-18 significantly reduced clinical symptoms in a murine model of contact hypersensitivity. Furthermore, IL-18BP alleviated the relapses during established disease, as indicated by significant protection during re-exposure of mice that had previously undergone a contact hypersensitivity response without treatment. Although edema was not influenced, IL-18BP reduced the number of T cells homing to sites of inflammation, resulting in diminished local production of IFN-γ. Thus, by preventing the accumulation of effector T cells to the target tissue, IL-18BP appears to be a potent protective mediator to counter skin inflammation during contact hypersensitivity. Taken together with the evidence that IL-18 is present in tissue samples of the human disease, our data reinforces IL-18BP as a candidate for this therapeutic indication.
Constitutive Caspase Activation and Impaired Death-Inducing Signaling Complex Formation in CD95-Resistant, Long-Term Activated, Antigen-Specific T Cells
Authors: Strauss Gudrun , Knape Ingrid , Melzner Ingo , Debatin Klaus-Michael
Published: April 2014

Elimination of T cells during an immune response is mediated by activation-induced cell death (AICD) and CD95-mediated apoptosis. Chronic graft-vs-host disease and T cell-mediated autoimmune diseases are caused by the persistence of activated T cells that escaped tolerance induction by deletion or silencing. To mimic the in vivo situation of long-term activated T cells, we generated an in vitro system using HLA-A1-specific T cells, weekly restimulated by Ag. While short-term activated T cells (two to five rounds of stimulation) were CD95 sensitive and susceptible to AICD, T cells stimulated more than eight times acquired constitutive CD95 resistance and exhibited reduced AICD. Phenotypically, these long-term activated T cells could be identified as effector/memory T cells. The expression of the proforms of the CD95 receptor initiator caspases, caspase-8 and -10, and the effector caspase-3 was strongly decreased in these cells, and only active caspase fragments were detected. In contrast to short-term activated T cells, constitutive CD95 receptor clustering was observed on the cell surface, and caspase-8 was bound to the CD95 receptor in the absence of receptor triggering. After further cross-linking of CD95, additional formation of the death-inducing signaling complex (DISC) was strongly impaired. Reduced DISC formation in long-term activated T cells was associated with the loss of PTEN expression and the increased phosphorylation of protein kinase B. Inhibitors of phosphoinositol 3-kinase restored CD95 sensitivity and DISC formation in long-term activated T cells. These data suggest that defective CD95 signaling in effector/memory T cells may contribute to the apoptosis resistance toward physiological stimuli in T cells mediating tissue destruction in vivo.
Fas Ligand on Tumor Cells Mediates Inactivation of Neutrophils
Authors: Chen Yi-Ling , Chen Shun-Hua , Wang Jiu-Yao , Yang Bei-Chang
Published: April 2014

The expression of Fas ligand (FasL) on tumor cells (tumor FasL) has been implicated in their evasion of immune surveillance. In this study, we investigated the cellular mechanism for FasL-associated immune escape using melanoma B16F10-derived cells as a model. Transfectants carrying FasL-specific ribozymes expressed low levels of FasL (FasLlow tumor cells) as compared with those carrying enhanced green fluorescent protein-N1 plasmids (FasLhigh tumor cells). When injected s.c. into C57BL/6 mice, FasLlow tumor cells grew more slowly than did FasLhigh melanoma cells. FasLhigh tumor cells showed more intensive neutrophilic infiltration accompanied by multiple necrotizing areas than did FasLlow tumor cells. The average size of FasLlow tumors, but not of FasLhigh tumors, was significantly enhanced in mice depleted of neutrophils. Consistently, a local injection of LPS to recruit/activate neutrophils significantly delayed tumor formation by FasLlow tumor cells, and slightly retarded that of FasLhigh tumor cells in both C57BL/6 and nonobese diabetic/SCID mice. Neutrophils killed FasLlow melanoma cells more effectively than FasLhigh melanoma cells in vitro. The resistance of FasLhigh melanoma cells to being killed by neutrophils was correlated with impaired neutrophil activation, as demonstrated by reductions in gelatinase B secretion, reactive oxygen species production, and the surface expression of CD11b and the transcription of FasL. Local transfer of casein-enriched or PMA-treated neutrophils delayed tumor formation by melanoma cells. Taken together, inactivation of neutrophils by tumor FasL is an important mechanism by which tumor cells escape immune attack.
Scurfin (FoxP3) Controls T-Dependent Immune Responses In Vivo Through Regulation of CD4+ T Cell Effector Function
Authors: Kasprowicz Deborah J. , Smallwood P. Scott , Tyznik Aaron J. , Ziegler Steven F.
Published: April 2014

Scurfin, the protein product of the FoxP3 gene, is a forkhead-family transcription factor that negatively regulates T cell function. Mice carrying a loss-of-function mutation in FoxP3 (scurfy mice) present with fatal autoimmune-like disease caused by hyperresponsive CD4+ T cells. Mice that overexpress scurfin (FoxP3 Tg mice) possess fewer mature T cells with reduced functional capabilities compared with normal littermate control mice. We analyzed the ability of CD4+ T cells and B cells from FoxP3 Tg mice to respond to a T-dependent Ag and found that immunized FoxP3 Tg mice displayed reduced total and Ag-specific serum Ig and disorganized splenic architecture. However, when cultured in vitro, FoxP3 Tg B cells responded normally, suggesting that the poor Ab response was a result of defective T cell help in vivo. When challenged, CD4+ T cells from FoxP3 Tg mice display reduced up-regulation of CD40 ligand and fewer IFN-γ-producing cells. Overall, these findings show that overexpression of scurfin reduces T cell responses in vivo such that CD4+ T cells cannot provide help to B cells during a T cell-dependent Ab response.
l-Arginine Consumption by Macrophages Modulates the Expression of CD3ζ Chain in T Lymphocytes
Authors: Rodriguez Paulo C. , Zea Arnold H. , DeSalvo Joanna , Culotta Kirk S. , Zabaleta Jovanny , Quiceno David G. , Ochoa Juan B. , Ochoa Augusto C.
Published: April 2014

l-Arginine plays a central role in the normal function of several organs including the immune system. It is metabolized in macrophages by inducible nitric oxide synthase to produce nitric oxide, important in the cytotoxic mechanisms, and by arginase I (ASE I) and arginase II (ASE II) to synthesize l-ornithine and urea, the first being the precursor for the production of polyamines needed for cell proliferation. l-Arginine availability can modulate T cell function. Human T cells stimulated and cultured in the absence of l-arginine lose the expression of the TCR ζ-chain (CD3ζ) and have an impaired proliferation and a decreased cytokine production. The aim of this work was to test whether activated macrophages could modulate extracellular levels of l-arginine and alter T cell function, and to determine which metabolic pathway was responsible for this event. The results show that macrophages stimulated with IL-4 + IL-13 up-regulate ASE I and cationic amino acid transporter 2B, causing a rapid reduction of extracellular levels of l-arginine and inducing decreased expression of CD3ζ and diminished proliferation in normal T lymphocytes. Competitive inhibitors of ASE I or the addition of excess l-arginine lead to the re-expression of CD3ζ and recovery of T cell proliferation. In contrast, inducible nitric oxide synthase or ASE II failed to significantly reduce the extracellular levels of l-arginine and modulate CD3ζ expression. These results may provide new insights into the mechanisms leading to T cell dysfunction and the down-regulation of CD3ζ in cancer and chronic infectious diseases.
Regulation of Polyclonal T Cell Responses by an MHC Anchor-Substituted Variant of Myelin Oligodendrocyte Glycoprotein 35-55
Authors: Ford Mandy L. , Evavold Brian D.
Published: April 2014

Analogs of immunogenic peptides containing substitutions at TCR contact residues (altered peptide ligands (APLs)) have been used to manipulate Ag-specific T cell responses in models of autoimmunity, including experimental autoimmune encephalomyelitis. However, recent clinical trials with APL of a myelin basic protein epitope revealed limitations of this therapy. In this study, we demonstrate that individual myelin oligodendrocyte glycoprotein (MOG) 35-55-specific T cell clones responded differentially to a MOG 35-55 APL, raising questions about the ability of peptide analogs containing amino acid substitutions at TCR contact residues to control polyclonal populations of T cells. In contrast, we found that a variant peptide containing a substitution at an MHC anchor residue uniformly affected multiple MOG 35-55-specific clones and polyclonal lines. Stimulation of polyclonal MOG 35-55-specific T cells with an MHC variant peptide resulted in the induction of anergy, as defined by a dramatic reduction in proliferation and IL-2 production upon challenge with wild-type peptide. Furthermore, treatment of T cell lines with this peptide in vitro resulted in a significant reduction in their encephalitogenicity upon adoptive transfer. These results indicate that the use of MHC anchor-substituted peptides may be efficacious in the regulation of polyclonal T cell responses such as those found in EAE.
A Giant GTPase, Very Large Inducible GTPase-1, Is Inducible by IFNs
Authors: Klamp Thorsten , Boehm Ulrich , Schenk Daniela , Pfeffer Klaus , Howard Jonathan C.
Published: April 2014

The complex, partially overlapping, cellular responses to IFN type I (IFN-α and -β) and IFN type II (IFN-γ) involve several hundred genes that can be largely classified in terms of specific cellular programs functional in innate and adaptive immunity. Among these programs are previously unconsidered mechanisms of cell-autonomous resistance against various pathogens mediated by dedicated, largely novel families of GTPases. We report here the identification and characterization of a new GTPase family that contributes to the cellular response to both type I and type II IFNs. We name this family the very large inducible GTPases (VLIGs). The prototype VLIG, VLIG-1, is a strongly IFN-inducible, soluble, cytosolic and nuclear protein of 280 kDa. The open reading frame of VLIG-1 is encoded on a single very large exon, and outside the canonical GTP-binding motifs, sequence and structural prediction suggest a unique family without significant relationship to other known protein families. Within the GTPase superfamily the VLIG family is more closely related to IFN-inducible GTPases mediating cell-autonomous resistance than to other GTPase families. In addition, we provide evidence that VLIG-1 is polymorphic in mice of different genetic backgrounds and is a member of a small gene family on mouse chromosome 7 with a conserved homologue located on human chromosome 11.
Blockade of Programmed Death-1 Engagement Accelerates Graft-Versus-Host Disease Lethality by an IFN-γ-Dependent Mechanism
Authors: Blazar Bruce R. , Carreno Beatriz M. , Panoskaltsis-Mortari Angela , Carter Laura , Iwai Yoshiko , Yagita Hideo , Nishimura Hiroyuki , Taylor Patricia A.
Published: April 2014

Acute graft-vs-host disease (GVHD) is influenced by pathways that can enhance or reduce lethality by providing positive or negative signals to donor T cells. To date, the only reported pathway to inhibit GVHD is the CTLA-4:B7 pathway. Because absence of the programmed death-1 (PD-1) pathway has been implicated in a predisposition to autoimmunity and hence a lack of negative signals, the effect of PD-1 pathway blockade on GVHD was explored using several distinct approaches. In each, GVHD lethality was markedly accelerated. Coblockade of CTLA-4 and PD-1 was additive in augmenting GVHD, indicating that these pathways are not fully redundant. Although neither perforin nor Fas ligand expression was required for GVHD enhancement, donor IFN-γ production was required for optimal GVHD acceleration in the absence of PD-1 ligation. These data indicate that PD-1 ligation down-regulates GVHD through modulation of IFN-γ production and suggest a novel therapeutic target for inhibiting GVHD lethality.
Chronic Exposure to Low Levels of Antigen in the Periphery Causes Reversible Functional Impairment Correlating with Changes in CD5 Levels in Monoclonal CD8 T Cells
Authors: Stamou Panagiota , de Jersey James , Carmignac Danielle , Mamalaki Clio , Kioussis Dimitris , Stockinger Brigitta
Published: April 2014

This study describes a double-transgenic model in which monoclonal CD8 F5 T cells are chronically exposed to self Ag (nucleoprotein) in the periphery, but are not affected during thymic development. Chronic exposure of CD8 T cells to their cognate Ag rendered them unable to proliferate or produce cytokines in response to antigenic stimulation in vitro. However, the cells still retained some killer function in vivo and continuously eliminated APC expressing high levels of Ag. In addition, when crossed with mice expressing Ag in the anterior pituitary gland (triple-transgenic mice), F5 T cells migrated to this site and killed growth hormone producing somatotrophs. The anergic state was reversible upon transfer into Ag-free recipients, resulting in full recovery of in vitro responsiveness to Ag. Anergic CD8 T cells express higher levels of CD5, a negative regulator of T cell signaling, whereas after transfer and residence in Ag-free hosts, CD5 levels returned to normal. This suggests that up-regulation of negative T cell regulators in peripheral T cells exposed to chronic stimulation by Ag may prevent full functionality and thus avoid overt autoreactivity.
Constitutively Active Protein Kinase B Enhances Lck and Erk Activities and Influences Thymocyte Selection and Activation
Authors: Na Shin-Young , Patra Amiya , Scheuring Yvonne , Marx Alexander , Tolaini Mauro , Kioussis Dimitris , Hemmings Brian , Hünig Thomas , Bommhardt Ursula
Published: April 2014

Protein kinase B (PKB), a serine threonine kinase is critically involved in cellular proliferation and survival. To characterize its role in T cell development in vivo, we have analyzed transgenic mice that express a membrane-targeted constitutively active version of PKB (myr PKB) in thymocytes and peripheral T cells. We report that myr PKB renders proliferative responses of thymocytes more sensitive to TCR signals by increased and sustained activation of Src kinase Lck and the extracellular signal-regulated kinase/mitogen-activated protein kinase pathway. In addition, the proliferative response of myr PKB T cells is relatively independent of calcium mobilization and calcineurin activity. We also find that myr PKB enhances phosphorylation of glycogen synthase kinase 3, a negative regulator of NFAT and T cell activation, and the recruitment of the adapter protein Cbl-c. Interestingly, we demonstrate that upon TCR/CD3 stimulation of wild-type T cells PKB is translocated into lipid rafts, adding a new role for PKB in TCR-initiated signalosome formation in T cell activation. Localization of transgenic PKB in lipid rafts could contribute to the higher TCR sensitivity of myr PKB thymocytes which is reflected in an increase in positive selection toward the CD4 lineage and variable effects on negative selection depending on the model system analyzed. Thus, our observations clearly indicate a cross-talk between PKB and important signaling molecules downstream of TCR that modulate the thresholds of thymocyte selection and T cell activation.
The Onecut Transcription Factor Hepatocyte Nuclear Factor-6 Controls B Lymphopoiesis in Fetal Liver
Authors: Bouzin Caroline , Clotman Frédéric , Renauld Jean-Christophe , Lemaigre Frédéric P. , Rousseau Guy G.
Published: April 2014

Mouse genetic models have helped to identify transcription factors that are expressed by hemopoietic cells and control their differentiation into lymphoid cells. However, little is known on transcription factors that are involved in this process, but are expressed in nonhemopoietic cells of the microenvironment. We show in this study that inactivation of the gene coding for hepatocyte nuclear factor-6 (HNF-6) in mice led to B lymphopenia in the bone marrow and spleen. This phenotype disappeared shortly after birth when fetal B lymphopoiesis is no longer active, pointing to a defect in fetal liver. Indeed, the number of B cells was decreased in this organ as well. An analysis of B cell developmental markers in fetal liver cells showed that B lymphopoiesis was impaired just beyond the pre-pro B cell stage. Hemopoietic cells from hnf6−/− fetal liver could reconstitute the lymphoid system when injected into scid mice. Because parenchymal cells, but not hemopoietic cells, expressed hnf6 in normal liver, we concluded that HNF-6 controls B lymphopoiesis in fetal liver and that HNF-6 exerts this control indirectly by acting in parenchymal cells. The involvement, in the B cell defect of hnf6−/− fetuses, of genes known to exert such an indirect control was ruled out by expression analysis, including microarrays, and by in vivo rescue experiments. This work identifies HNF-6 as the first noncell-intrinsic transcription factor known to control B lymphopoiesis specifically in fetal liver.
The Porcine Ig δ Gene: Unique Chimeric Splicing of the First Constant Region Domain in its Heavy Chain Transcripts
Authors: Zhao Yaofeng , Pan-Hammarström Qiang , Kacskovics Imre , Hammarström Lennart
Published: April 2014

The pig δ gene is located ∼3.4 kb downstream of the second transmembrane exon of the μ gene and shows a similar genomic structure to its counterpart in cow with three exons encoding the CH1, CH2, and CH3 domains. The porcine genomic δCH1 exon has been replaced by a recent duplication of the μCH1 and its flanking sequences, a genetic event that also led to the formation of a short switch δ region, immediately upstream of the δ gene. The δCH1 exhibits a 98.7% similarity (314 of 318 bp) to the μCH1 at the DNA level, whereas the homologies between the δCH2 and μCH3, and the δCH3 and μCH4 are only 33.3 and 35.8%, respectively. Either of the two CH1 exons (μ and δ) could be observed in the expressed porcine IgD H chain cDNA sequences VDJ-μCH1-H-δCH2-δCH3 or VDJ-δCH1-H-δCH2-δCH3, showing a pattern that has not been observed previously in vertebrates. In addition, transfection of a human B cell line, using artificial constructs resembling the porcine Cμ-Cδ locus, also generated both VDJ-μCH1-δCH1-H1-δCH2 and VDJ -δCH1-H1-δCH2 transcripts. An examination of the pig δ genomic sequence shows a putative, second hinge region-encoding exon. Due to the lack of a normal branchpoint sequence for RNA splicing, this exon is not present in the normal pig δ cDNA. However, the exon could be spliced into most of the expressed transcripts in vitro in cell transfection experiments after introduction of a single T nucleotide to restore the branchpoint sequence upstream of the putative H2 exon.
Complexes of HLA-G Protein on the Cell Surface Are Important for Leukocyte Ig-Like Receptor-1 Function
Authors: Gonen-Gross Tsufit , Achdout Hagit , Gazit Roi , Hanna Jacob , Mizrahi Sa’ar , Markel Gal , Goldman-Wohl Debra , Yagel Simcha , Hořejší Václav , Levy Ofer , Baniyash Michal , Mandelboim Ofer
Published: April 2014

The nonclassical class I MHC molecule HLA-G is selectively expressed on extravillous cytotrophoblast cells at the maternal-fetal interface during pregnancy. HLA-G can inhibit the killing mediated by NK cells via interaction with the inhibitory NK cell receptor, leukocyte Ig-like receptor-1 (LIR-1). Comparison of the sequence of the HLA-G molecule to other class I MHC proteins revealed two unique cysteine residues located in positions 42 and 147. Mutating these cysteine residues resulted in a dramatic decrease in LIR-1 Ig binding. Accordingly, the mutated HLA-G transfectants were less effective in the inhibition of NK killing and RBL/LIR-1 induced serotonin release. Immunoprecipitation experiments demonstrated the involvement of the cysteine residues in the formation of HLA-G protein oligomers on the cell surface. The cysteine residue located at position 42 is shown to be critical for the expression of such complexes. These oligomers, unique among the class I MHC proteins, probably bind to LIR-1 with increased avidity, resulting in an enhanced inhibitory function of LIR-1 and an impaired killing function of NK cells.
Promiscuous CTL Recognition of Viral Epitopes on Multiple Human Leukocyte Antigens: Biological Validation of the Proposed HLA A24 Supertype
Authors: Burrows Scott R. , Elkington Rebecca A. , Miles John J. , Green Katherine J. , Walker Susan , Haryana Sofia M. , Moss Denis J. , Dunckley Heather , Burrows Jacqueline M. , Khanna Rajiv
Published: April 2014

Multiple HLA class I alleles can bind peptides with common sequence motifs due to structural similarities in the peptide binding cleft, and these groups of alleles have been classified into supertypes. Nine major HLA supertypes have been proposed, including an A24 supertype that includes A*2301, A*2402, and A*3001. Evidence for this A24 supertype is limited to HLA sequence homology and/or similarity in peptide binding motifs for the alleles. To investigate the immunological relevance of this proposed supertype, we have examined two viral epitopes (from EBV and CMV) initially defined as HLA-A*2301-binding peptides. The data clearly demonstrate that each peptide could be recognized by CTL clones in the context of A*2301 or A*2402; thus validating the inclusion of these three alleles within an A24 supertype. Furthermore, CTL responses to the EBV epitope were detectable in both A*2301+ and A*2402+ individuals who had been previously exposed to this virus. These data substantiate the biological relevance of the A24 supertype, and the identification of viral epitopes with the capacity to bind promiscuously across this supertype could aid efforts to develop CTL-based vaccines or immunotherapy. The degeneracy in HLA restriction displayed by some T cells in this study also suggests that the dogma of self-MHC restriction needs some refinement to accommodate foreign peptide recognition in the context of multiple supertype alleles.
Clearance ofPneumocystis cariniiin Mice Is Dependent on B Cells But Not onP. carinii-Specific Antibody
Authors: Lund Frances E. , Schuer Kevin , Hollifield Melissa , Randall Troy D. , Garvy Beth A.
Published: April 2014

Both CD4+ T cells and B cells are critical for defense against Pneumocystis carinii infection; however, the mechanism by which B cells mediate protection is unknown. We show that P. carinii-specific IgM is not sufficient to mediate clearance of P. carinii from the lungs since CD40-deficient mice produced normal levels of specific IgM, but were unable to clear the organisms. Using chimeric mice in which the B cells were deficient in CD40 (CD40KO chimeras) we found that clearance of P. carinii infection is delayed compared with wild-type controls. These CD40KO chimeric mice produced normal levels of P. carinii-specific IgM, but did not produce class-switched IgG or IgA. Similarly, clearance of P. carinii was delayed in mice deficient in FcγRI and III (FcγRKO), indicating that P. carinii-specific IgG partially mediates opsonization and clearance of P. carinii. Opsonization of organisms by complement did not compensate for the lack of specific IgG or FcγR, since C3-deficient and C3-depleted FcγRKO mice were still able to clear P. carinii. Finally, μMT and CD40KO chimeric mice had reduced numbers of activated CD4+ T cells in the lungs and lymph nodes compared with wild-type mice, suggesting that B cells are important for activation of T cells in response to P. carinii. Together these data indicate that P. carinii-specific IgG plays an important, but not critical, role in defense against P. carinii. Moreover, these data suggest that B cells also mediate host defense against P. carinii by facilitating CD4+ T cell activation or expansion.
Porcine Pulmonary Collectins Show Distinct Interactions with Influenza A Viruses: Role of theN-Linked Oligosaccharides in the Carbohydrate Recognition Domain
Authors: van Eijk Martin , White Mitchell R. , Crouch Erika C. , Batenburg Joseph J. , Vaandrager Arie B. , van Golde Lambert M. G. , Haagsman Henk P. , Hartshorn Kevan L.
Published: April 2014

Influenza A virus (IAV) infections are a major cause of respiratory disease of humans and animals. Pigs can serve as important intermediate hosts for transmission of avian IAV strains to humans, and for the generation of reassortant strains; this may result in the appearance of new pandemic IAV strains in humans. We have studied the role of the porcine lung collectins surfactant proteins D and A (pSP-D and pSP-A), two important components of the innate immune response against IAV. Hemagglutination inhibition assays revealed that both pSP-D and pSP-A display substantially greater inhibitory activity against IAV strains isolated from human, swine, and horse, than lung collectins from other animal species. The more potent activity of pSP-D results from interactions mediated by the asparagine-linked oligosaccharide located in the carbohydrate recognition domain of pSP-D, which is absent in SP-Ds from other species characterized to date. Presence of this sialylated oligosaccharide moiety enhances the anti-influenza activity of pSP-D, as demonstrated by assays of viral aggregation, inhibition of infectivity, and neutrophil response to IAV. The greater hemagglutination inhibitory activity of pSP-A is due to porcine-specific structural features of the conserved asparagine-linked oligosaccharide in the carbohydrate recognition domain of SP-A. A more efficient lung collectin-mediated immune response against IAV in pigs may play a role in providing conditions by which pigs can act as “mixing vessel” hosts that can lead to the production of reassortant, pandemic strains of IAV.
Heat-KilledBrucella abortusInduces TNF and IL-12p40 by Distinct MyD88-Dependent Pathways: TNF, Unlike IL-12p40 Secretion, Is Toll-Like Receptor 2 Dependent
Authors: Huang Li-Yun , Aliberti Julio , Leifer Cynthia A. , Segal David M. , Sher Alan , Golenbock Douglas T. , Golding Basil
Published: April 2014

Cattle and humans are susceptible to infection with the Gram-negative intracellular bacterium Brucella abortus. Heat-killed B. abortus (HKBA) is a strong Th1 adjuvant and carrier. Previously, we have demonstrated that dendritic cells produce IL-12 in response to HKBA stimulation. In the present study, we use knockout mice and in vitro reconstitution assays to examine the contribution of signaling by Toll-like receptors (TLRs) and their immediate downstream signaling initiator, myeloid differentiation protein MyD88, in the activation following stimulation by HKBA. Our results show that HKBA-mediated induction of IL-12p40 and TNF is dependent on the adapter molecule MyD88. To identify the TLR involved in HKBA recognition, we examined HKBA responses in TLR2- and TLR4-deficient animals. TNF responses to HKBA were TLR4 independent; however, the response in TLR2-deficient mice was significantly delayed and reduced, although not completely abolished. Studies using Chinese hamster ovary/CD14 reporter cell lines stably transfected with either human TLR2 or human TLR4 confirmed the results seen with knockout mice, namely TLR2, but not TLR4, can mediate cellular activation by HKBA. In addition, human embryonic kidney 293 cells, which do not respond to HKBA, were made responsive by transfecting TLR2, but not TLR4 or TLR9. Taken together, our data demonstrate that MyD88-dependent pathways are crucial for activation by HKBA and that TLR2 plays a role in TNF, but not IL-12p40 pathways activated by this microbial product.
Leptospira interrogansActivation of Human Peripheral Blood Mononuclear Cells: Preferential Expansion of TCRγδ+ T Cells vs TCRαβ+ T Cells
Authors: Klimpel Gary R. , Matthias Michael A. , Vinetz Joseph M.
Published: April 2014

Innate and adaptive immune responses induced by leptospirosis have not been well characterized. In this study we show that in vitro exposure of naive human PBMC to Leptospira interrogans results in cell proliferation and the production of IFN-γ, IL-12, and TNF-α. Cell proliferation was highest when using high numbers of Leptospira. Optimal cell proliferation occurred at 6–8 days, and the majority of cells contained in these cultures were γ/δ T cells. These cultures showed a 10- to 50-fold expansion of γ/δ T cells compared with the initial cellular input. Additionally, these cultures contained elevated numbers of NK cells. In contrast, exposure of PBMC to low numbers of Leptospira failed to induce γδ T cell or NK cell expansion, but induced significant αβ T cell expansion. Vγ9/Vδ2 were expressed on all γ/δ T cells expanded by exposure of PBMC to Leptospira. Leptospira stimulation of purified TCRγδ+ T cells, obtained from 8-day cultures of Leptorspira-stimulated PBMC, induced high levels of IFN-γ production, but no cell proliferation, suggesting that such stimulation of γδ T cells did not depend on specialized accessory cells or Ag processing. Finally, in patients with acute leptospirosis, there was a significant (4- to 5-fold) increase in the number of peripheral blood TCRγδ+ T cells. These results indicate that Leptospira can activate γδ T cells and αβ T cells and will guide further investigations into the roles of these T cell populations in host defense and/or the pathology of leptospirosis.
Inhibition of a p38/Stress-Activated Protein Kinase-2-Dependent Phosphatase Restores Function of IL-1 Receptor-Associated Kinase-1 and Reverses Toll-Like Receptor 2- and 4-Dependent Tolerance of Macrophages
Authors: Ropert Catherine , Closel Meire , Chaves Andréa C. L. , Gazzinelli Ricardo T.
Published: April 2014

Pretreatment of macrophages with Toll-like receptor (TLR)2 or TLR4 agonists leads to a stage of cell hyporesponsiveness to a second stimulation with TLR agonists. This tolerance state is accompanied by the repression of IL-1 receptor-associated kinase-1, mitogen-activated protein kinases, and IκB phosphorylation and expression of genes encoding proinflammatory cytokines, like IL-1β and TNF-α. In this report, we demonstrated that mucin-like glycoprotein (tGPI-mucin) of Trypanosoma cruzi trypomastigotes (TLR2 agonist) and LPS (TLR4 agonist) induce cross-tolerance in macrophages and we addressed the role of phosphatase activity in this process. Analysis of the kinetic of phosphatase activity induced by tGPI-mucin or LPS revealed maximum levels between 12 and 24 h, which correlate with the macrophage hyporesponsiveness stage. The addition of okadaic acid, an inhibitor of phosphatase activity, reversed macrophage hyporesponsiveness after exposure to either LPS or tGPI-mucin, allowing phosphorylation of IL-1R-associated kinase-1, mitogen-activated protein kinases, and ΙκB and leading to TNF-α gene transcription and cytokine production. Furthermore, pretreatment with either the specific p38/stress-activated protein kinase-2 inhibitor (SB203580) or the NF-κB translocation inhibitor (SN50) prevented the induction of phosphatase activity and hyporesponsiveness in macrophage, permitting cytokine production after restimulation with LPS. These results indicate a critical role of p38/stress-activated protein kinase-2 and NF-κB-dependent phosphatase in macrophage hyporesponsiveness induced by microbial products that activate TLR2 and TLR4.
Human Mast Cell β-Tryptase Is a Gelatinase
Authors: Fajardo Ignacio , Pejler Gunnar
Published: April 2014

Remodeling of extracellular matrix is an important component in a variety of inflammatory disorders as well as in normal physiological processes such as wound healing and angiogenesis. Previous investigations have identified the various matrix metalloproteases, e.g., gelatinases A and B, as key players in the degradation of extracellular matrix under such conditions. Here we show that an additional enzyme, human mast cell β-tryptase, has potent gelatin-degrading properties, indicating a potential contribution of this protease to matrix degradation. Human β-tryptase was shown to degrade gelatin both in solution and during gelatin zymographic analysis. Further, β-tryptase was shown to degrade partially denatured collagen type I. β-Tryptase bound strongly to gelatin, forming high molecular weight complexes that were stable during SDS-PAGE. Mast cells store large amounts of preformed, active tryptase in their secretory granules. Considering the location of mast cells in connective tissues and the recently recognized role of mast cells in disorders in which connective tissue degradation is a key event, e.g., rheumatoid arthritis, it is thus likely that tryptase may contribute to extracellular matrix-degrading processes in vivo.
Pellino3, a Novel Member of the Pellino Protein Family, Promotes Activation of c-Jun and Elk-1 and May Act as a Scaffolding Protein
Authors: Jensen Liselotte E. , Whitehead Alexander S.
Published: April 2014

Toll-like receptors and the IL-1R are part of the innate immune response aimed at mobilizing defense mechanisms in response to infections or injury. These receptors can initiate common intracellular signaling cascades. One intermediate component in these signaling cascades is Pellino, which was first identified in Drosophila and shown to interact with IL-1R-associated kinase. Two homologues, Pellino1 and Pellino2, have been identified in mammals. A novel member of the Pellino protein family has been identified and named Pellino3. Pellino3 shares 84 and 85% amino acid identity with Pellino1 and Pellino2, respectively. Two alternatively spliced Pellino3 mRNAs, Pellino3a and Pellino3b, are widely expressed. Pellino3 physically interacts with IL-1R-associated kinase-1, TNF receptor-associated factor-6, TGF-β-activated kinase-1, and NF-κB-inducing kinase in an IL-1-dependent manner, suggesting that it plays a role as a scaffolding protein. In reporter assays Pellino3 leads to activation of c-Jun and Elk-1, but not NF-κB. Pellino3 also leads to activation of c-Jun N-terminal kinase. These data suggest that Pellino3 plays an important role in the innate immune response.
The Proteasome as a Lipopolysaccharide-Binding Protein in Macrophages: Differential Effects of Proteasome Inhibition on Lipopolysaccharide-Induced Signaling Events
Authors: Qureshi Nilofer , Perera Pin-Yu , Shen Jing , Zhang Guochi , Lenschat Arnd , Splitter Gary , Morrison David C. , Vogel Stefanie N.
Published: April 2014

We have developed a novel LPS probe using a highly purified and homogenous preparation of [3H] Escherichia coli LPS from the deep rough mutant, which contains a covalently linked, photoactivable 4-p-(azidosalicylamido)-butylamine group. This cross-linker was used to identify the LPS-binding proteins in membranes of the murine-macrophage-like cell line RAW 264.7. The α-subunit (PSMA1 C2, 29.5 kDa) and the β-subunit (PSMB4 N3, 24.36 kDa) of the 20S proteasome complex were identified as LPS-binding proteins. This is the first report demonstrating LPS binding to enzymes such as the proteasome subunits. Functionally, LPS enhanced the chymotrypsin-like activity of the proteasome to degrade synthetic peptides in vitro and, conversely, the proteasome inhibitor lactacystin completely blocked the LPS-induced proteasome’s chymotrypsin activity as well as macrophage TNF-α secretion and the expression of multiple inflammatory mediator genes. Lactacystin also completely blocked the LPS-induced expression of Toll-like receptor 2 mRNA. In addition, lactacystin dysregulated mitogen-activated protein kinase phosphorylation in LPS-stimulated macrophages, but failed to inhibit IL-1 receptor-associated kinase-1 activity. Importantly, lactacystin also prevented LPS-induced shock in mice. These data strongly suggest that the proteasome complex regulates the LPS-induced signal transduction and that it may be an important therapeutic target in Gram-negative sepsis.
TRAIL Induces Apoptosis and Inflammatory Gene Expression in Human Endothelial Cells
Authors: Li Jie Hui , Kirkiles-Smith Nancy C. , McNiff Jennifer M. , Pober Jordan S.
Published: April 2014

Human TRAIL can efficiently kill tumor cells in vitro and kill human tumor xenografts in mice with little effect on normal mouse cells or tissues. The effects of TRAIL on normal human tissues have not been described. In this study, we report that endothelial cells (EC), isolated from human umbilical veins or human dermal microvessels, express death domain-containing TRAIL-R1 and -R2. Incubation with TRAIL for 15 h causes ∼30% of cultured EC to die, as assessed by propidium iodide uptake. Death is apoptotic, as assessed by Annexin V staining, 4′,6′-diamidino-2-phenylindole staining, and DNA fragment ELISA. EC death is increased by cotreatment with cycloheximide but significantly reduced by caspase inhibitors or transduced dominant-negative Fas-associated death domain protein. In surviving cells, TRAIL activates NF-κB, induces expression of E-selectin, ICAM-1, and IL-8, and promotes adhesion of leukocytes. Injection of TRAIL into human skin xenografts promotes focal EC injury accompanied by limited neutrophil infiltration. These data suggest that TRAIL is an inducer of tissue injury in humans, an outcome that may influence antitumor therapy with TRAIL.