bluuebunny/crossref_metadata_2025 huggingface dataset:
The Tec Kinases Itk and Rlk Regulate NKT Cell Maturation, Cytokine Production, and Survival
Authors: Felices Martin , Berg Leslie J.
Published: April 2014

The Tec kinases Itk and Rlk are required for efficient positive selection of conventional CD4+ and CD8+ T cells in the thymus. In contrast, recent studies have shown that these Tec kinases are dispensable for the development of CD8+ T cells with characteristics of innate T cells. These findings raise questions about the potential role of Itk and Rlk in NKT cell development, because NKT cells represent a subset of innate T cells. To address this issue, we examined invariant NKT cells in Itk−/− and Itk/Rlk−/− mice. We find, as has been reported previously, that Itk−/− mice have reduced numbers of NKT cells with a predominantly immature phenotype. We further show that this defect is greatly exacerbated in the absence of both Itk and Rlk, leading to a 7-fold reduction in invariant NKT cell numbers in the thymus of Itk/Rlk−/− mice and a more severe block in NKT cell maturation. Splenic Itk−/− and Itk/Rlk−/− NKT cells are also functionally defective, because they produce little to no cytokine following in vivo activation. Tec kinase-deficient NKT cells also show enhanced cell death in the spleen. These defects correlate with greatly diminished expression of CD122, the IL-2R/IL-15R β-chain, and impaired expression of the T-box transcription factor, T-bet. These data indicate that the Tec kinases Itk and Rlk provide important signals for terminal maturation, efficient cytokine production, and peripheral survival of NKT cells.
CCR5-Dependent Regulatory T Cell Migration Mediates Fungal Survival and Severe Immunosuppression
Authors: Moreira Ana Paula , Cavassani Karen Angelica , Tristão Fabrine Sales Massafera , Campanelli Ana Paula , Martinez Roberto , Rossi Marcos Antonio , Silva João S.
Published: April 2014

Paracoccidioidomycosis, a debilitating pulmonary mycosis, is caused by the dimorphic fungus Paracoccidioides brasiliensis. The infection results in the formation of granulomas containing viable yeast cells that are the fungal sources for disease reactivation. Because CD4+CD25+ regulatory T cells (Tregs) are in the lesions of patients with paracoccidioidomycosis, the migration of Treg cells is dependent on the axis chemokine-chemokine receptors, and CCR5 ligands are produced in P. brasiliensis-induced lesions, we investigated the role of CCR5 in the control of the infection. The results showed that CCR5−/− mice are more efficient in controlling fungal growth and dissemination and exhibited smaller granulomas than wild-type (WT) mice. In the absence of CCR5, the percentage of CD4+CD25+ T cells expressing Foxp3, glucocorticoid-induced TNFR (GITR), CD103, CD45low, and CTLA-4 in the granulomas was significantly decreased. Interestingly, P. brasiliensis infection resulted in an absence of T cell proliferation in response to Con A in WT but not CCR5−/− mice that was abrogated by anti-CTLA-4 mAb and anti-GITR mAb. Moreover, the adoptive transfer of CD4+CD25+ but not CD4+CD25− T cells from infected WT to infected CCR5−/− mice resulted in a significant increase in fungal load. Overall, CCR5 is a key receptor for the migration of Treg cells to the site of P. brasiliensis infection, leading to down-modulation of effector immune response and the long-term presence of the fungus in the granulomas. Thus, a tight control of Treg cell migration to the granulomatous lesions could be an important mechanism for avoiding exacerbation and reactivation of the disease.
Phenotypic and Functional Characterization of Ultraviolet Radiation-Induced Regulatory T Cells
Authors: Maeda Akira , Beissert Stefan , Schwarz Thomas , Schwarz Agatha
Published: April 2014

Sensitization through UV-exposed skin induces regulatory T cells (Treg). In contrast to the classical CD4+CD25+ Treg that act contact dependent, UV-induced Treg (UV-Treg) suppress via IL-10, indicating a distinct subtype that requires further characterization. Depletion studies revealed that UV-Treg express the glucocorticoid-induced TNF family-related receptor (GITR) and the surface molecule neuropilin-1. The injection of T cells from UV-tolerized mice after depletion of UV-Treg into naive recipients enabled a contact hypersensitivity response, indicating that tolerization also induces T effector cells. Adoptive transfer experiments using IL-10-deficient mice indicated that the IL-10 required for suppression is derived from UV-Treg and not from host-derived cells. Activation of UV-Treg is Ag specific, however, once activated suppression is nonspecific (bystander suppression). Hence, speculations exist about the therapeutic potential of Treg generated in response to Ag that are not necessarily the precise Ag driving the pathogenic process. Thus, we studied the consequences of multiple injections of 2,4-dintrofluorobenzene (DNFB)-specific Treg into ears of naive mice followed by multiple DNFB challenges. DNFB-specific Treg were injected once weekly into the left ears of naive mice and DNFB challenge was performed always 24 h later. After three injections, a challenging dose of DNFB was applied on the right ear. This resulted in pronounced ear swelling, indicating that the subsequent boosting of DNFB-specific Treg had caused sensitization of the naive mice against DNFB. These data demonstrate that UV-Treg express GITR and neuropilin-1 and act via bystander suppression. However, constant boosting of Treg with Ag doses in the challenging range results in final sensitization that might limit their therapeutic potential.
Differential Roles of Galectin-1 and Galectin-3 in Regulating Leukocyte Viability and Cytokine Secretion
Authors: Stowell Sean R. , Qian Yuning , Karmakar Sougata , Koyama Natalia S. , Dias-Baruffi Marcelo , Leffler Hakon , McEver Rodger P. , Cummings Richard D.
Published: April 2014

Galectin-1 (Gal-1) and galectin-3 (Gal-3) exhibit profound but unique immunomodulatory activities in animals but their molecular mechanisms are incompletely understood. Early studies suggested that Gal-1 inhibits leukocyte function by inducing apoptotic cell death and removal, but recent studies show that some galectins induce exposure of the common death signal phosphatidylserine (PS) independently of apoptosis. In this study, we report that Gal-3, but not Gal-1, induces both PS exposure and apoptosis in primary activated human T cells, whereas both Gal-1 and Gal-3 induce PS exposure in neutrophils in the absence of cell death. Gal-1 and Gal-3 bind differently to the surfaces of T cells and only Gal-3 mobilizes intracellular Ca2+ in these cells, although Gal-1 and Gal-3 bind their respective T cell ligands with similar affinities. Although Gal-1 does not alter T cell viability, it induces IL-10 production and attenuates IFN-γ production in activated T cells, suggesting a mechanism for Gal-1-mediated immunosuppression in vivo. These studies demonstrate that Gal-1 and Gal-3 induce differential responses in T cells and neutrophils, and identify the first factor, Gal-3, capable of inducing PS exposure with or without accompanying apoptosis in different leukocytes, thus providing a possible mechanism for galectin-mediated immunomodulation in vivo.
Tumor-Specific CD4+ T Cells Render the Tumor Environment Permissive for Infiltration by Low-Avidity CD8+ T Cells
Authors: Wong S. B. Justin , Bos Rinke , Sherman Linda A.
Published: April 2014

CD4+ T cells enhance tumor destruction by CD8+ T cells. One benefit that underlies CD4+ T cell help is enhanced clonal expansion of newly activated CD8+ cells. In addition, tumor-specific CD4+ help is also associated with the accumulation of greater numbers of CD8+ T cells within the tumor. Whether this too is attributable to the effects of help delivered to the CD8+ cells during priming within secondary lymphoid tissues, or alternatively is due to the action of CD4+ cells within the tumor environment has not been examined. In this study, we have evaluated separately the benefits of CD4+ T cell help accrued during priming of tumor-specific CD8+ T cells with a vaccine, as opposed to the benefits delivered by the presence of cognate CD4+ cells within the tumor. The presence of CD4+ T cell help during priming increased clonal expansion of tumor-specific CD8+ T cells in secondary lymphoid tissue; however, CD8+ T cells that have low avidity for tumor Ag were inefficient in tumor invasion. CD4+ T cells that recognized tumor Ag were required to facilitate accumulation of CD8+ T cells within the tumor and enhance tumor lysis during the acute phase of the response. These experiments highlight the ability of tumor-specific CD4+ T cells to render the tumor microenvironment receptive for CD8+ T cell immunotherapy, by facilitating the accumulation of all activated CD8+ T cells, including low-avidity tumor-specific and noncognate cells.
Radiation-Induced IFN-γ Production within the Tumor Microenvironment Influences Antitumor Immunity
Authors: Lugade Amit A. , Sorensen Elizabeth W. , Gerber Scott A. , Moran James P. , Frelinger John G. , Lord Edith M.
Published: April 2014

Alterations to the tumor microenvironment following localized irradiation may influence the effectiveness of subsequent immunotherapy. The objective of this study was to determine how IFN-γ influences the inflammatory response within this dynamic environment following radiotherapy. B16/OVA melanoma cells were implanted into C57BL/6 (wild-type (WT)) and IFN-γ-deficient (IFN-γ−/−) mice. Seven days after implantation, mice received 15 Gy of localized tumor irradiation and were assessed 7 days later. Irradiation up-regulated the expression of VCAM-1 on the vasculature of tumors grown in WT but not in IFN-γ−/− mice. Levels of the IFN-γ-inducible chemokines MIG and IFN-γ-inducible protein 10 were decreased in irradiated tumors from IFN-γ−/− mice compared with WT. In addition to inducing molecular cues necessary for T cell infiltration, surface MHC class I expression is also up-regulated in response to IFN-γ produced after irradiation. The role of IFN-γ signaling in tumor cells on class I expression was tested using B16/OVA cells engineered to overexpress a dominant negative mutant IFN-γ receptor (B16/OVA/DNM). Following implantation and treatment, expression of surface class I on tumor cells in vivo was increased in B16/OVA, but not in B16/OVA/DNM tumors, suggesting IFN-γ acts directly on tumor cells to induce class I up-regulation. These increases in MHC class I expression correlated with greater levels of activated STAT1. Thus, IFN-γ is instrumental in creating a tumor microenvironment conducive for T cell infiltration and tumor cell target recognition.
ICOS Mediates the Development of Insulin-Dependent Diabetes Mellitus in Nonobese Diabetic Mice
Authors: Hawiger Daniel , Tran Elise , Du Wei , Booth Carmen J. , Wen Li , Dong Chen , Flavell Richard A.
Published: April 2014

Initiation of diabetes in NOD mice can be mediated by the costimulatory signals received by T cells. The ICOS is found on Ag-experienced T cells where it acts as a potent regulator of T cell responses. To determine the function of ICOS in diabetes, we followed the course of autoimmune disease and examined T cells in ICOS-deficient NOD mice. The presence of ICOS was indispensable for the development of insulitis and hyperglycemia in NOD mice. In T cells, the deletion of ICOS resulted in a decreased production of the Th1 cytokine IFN-γ, whereas the numbers of regulatory T cells remained unchanged. We conclude that ICOS is critically important for the induction of the autoimmune process that leads to diabetes.
Modifications in Small Interfering RNA That Separate Immunostimulation from RNA Interference
Authors: Eberle Florian , Gießler Kerstin , Deck Christopher , Heeg Klaus , Peter Mirjam , Richert Clemens , Dalpke Alexander H.
Published: April 2014

Synthetic small interfering RNA (siRNA) can suppress the expression of endogenous mRNA through RNA interference. It has been reported that siRNA can induce type I IFN production from plasmacytoid dendritic cells, leading to off-target effects. To separate immunostimulation from the desired gene-specific inhibitory activity, we designed RNA strands with chemical modifications at strategic positions of the ribose or nucleobase residues. Substitution of uridine residues by 2′-deoxyuridine or thymidine residues was found to decrease type I IFN production upon in vitro stimulation of human PBMC. Thymidine residues in both strands of a siRNA duplex further decreased immunostimulation. Fortunately, the thymidine residues did not affect gene-silencing activity. In contrast, 2′-O-methyl groups at adenosine and uridine residues reduced both IFN-α secretion and gene-silencing activity. Oligoribonucleotides with 2′-O-methyladenosine residues actively inhibited IFN-α secretion induced by other immunostimulatory RNAs, an effect not observed for strands with 2′-deoxynucleosides. Furthermore, neither 5-methylcytidine nor 7-deazaguanosine residues in the stimulatory strands affected IFN-α secretion, suggesting that recognition does not involve sites in the major groove of duplex regions. The activity data, together with structure prediction and exploratory UV-melting analyses, suggest that immunostimulatory sequences adopt folded structures. The results show that immunostimulation can be suppressed by suitable chemical modifications without losing siRNA potency by introducing seemingly minor structural changes.
Regulation of the NK Cell Alloreactivity to Bone Marrow Cells by the Combination of the Host NK Gene Complex and MHC Haplotypes
Authors: Iizuka Koho , Scalzo Anthony A. , Xian Hong , Yokoyama Wayne M.
Published: April 2014

Host NK cells can reject MHC-incompatible (allogeneic) bone marrow cells (BMCs), suggesting their effective role for graft-vs leukemia effects in the clinical setting of bone marrow transplantation. NK cell-mediated rejection of allogeneic BMCs is dependent on donor and recipient MHC alleles and other factors that are not yet fully characterized. Whereas the molecular mechanisms of allogeneic MHC recognition by NK receptors have been well studied in vitro, guidelines to understand NK cell allogeneic reactivity under the control of multiple genetic components in vivo remain less well understood. In this study, we use congenic mice to show that BMC rejection is regulated by haplotypes of the NK gene complex (NKC) that encodes multiple NK cell receptors. Most importantly, host MHC differences modulated the NKC effect. Moreover, the NKC allelic differences also affected the outcome of hybrid resistance whereby F1 hybrid mice reject parental BMCs. Therefore, these data indicate that NK cell alloreactivity in vivo is dependent on the combination of the host NKC and MHC haplotypes. These data suggest that the NK cell self-tolerance process dynamically modulates the NK cell alloreactivity in vivo.
Large-Scale Characterization of Natural Ligands Explains the Unique Gluten-Binding Properties of HLA-DQ2
Authors: Stepniak Dariusz , Wiesner Martina , de Ru Arnoud H. , Moustakas Antonis K. , Drijfhout Jan Wouter , Papadopoulos George K. , van Veelen Peter A. , Koning Frits
Published: April 2014

Celiac disease is an enteropathy caused by intolerance to dietary gluten. The disorder is strongly associated with DQA1*0501/DQB1*0201 (HLA-DQ2) as ∼95% of celiac patients express this molecule. HLA-DQ2 has unique Ag-binding properties that allow it to present a diverse set of gluten peptides to gluten-reactive CD4+ T cells so instigating an inflammatory reaction. Previous work has indicated that the presence of negatively charged amino acids within gluten peptides is required for specific binding. This, however, only partly explains the scale of the interaction. We have now characterized 432 natural ligands of HLA-DQ2 representing length variants of 155 distinct sequences. The sequences were aligned and the binding cores were inferred. Analysis of the amino acid distribution of these cores demonstrated that negatively charged residues in HLA-DQ2-bound peptides are favored at virtually all positions. This contrasts with a more restricted presence of such amino acids in T cell epitopes from gluten. Yet, HLA-DQ2 was also found to display a strong preference for proline at several anchor and nonanchor positions that largely match the position of proline in gluten T cell epitopes. Consequently, the bias for proline at p6 and p8 facilitates the enzymatic conversion of glutamine into glutamic acid in gluten peptides at p4 and p6, two important anchor sites. These observations provide new insights in the unique ability of HLA-DQ2 to bind a large repertoire of glutamine- and proline-rich gluten peptides. This knowledge may be an important asset in the development of future treatment strategies.
Properdin Plays a Protective Role in Polymicrobial Septic Peritonitis
Authors: Stover Cordula M. , Luckett Jeni C. , Echtenacher Bernd , Dupont Aline , Figgitt Sue E. , Brown Jane , Männel Daniela N. , Schwaeble Wilhelm J.
Published: April 2014

Properdin is a positive regulator of complement activation so far known to be instrumental in the survival of infections with certain serotypes of Neisseria meningitidis. We have generated a fully backcrossed properdin-deficient mouse line by conventional gene-specific targeting. In vitro, properdin-deficient serum is impaired in alternative pathway-dependent generation of complement fragment C3b when activated by Escherichia coli DH5α. Properdin-deficient mice and wild-type littermates compare in their levels of C3 and IgM. In an in vivo model of polymicrobial septic peritonitis induced by sublethal cecal ligation and puncture, properdin-deficient mice appear immunocompromised, because they are significantly impaired in their survival compared with wild-type littermates. We further show that properdin localizes to mast cells and that properdin has the ability to directly associate with E. coli DH5α. We conclude that properdin plays a significant role in the outcome of polymicrobial sepsis.
Fcγ Receptors Regulate Immune Activation and Susceptibility during Mycobacterium tuberculosis Infection
Authors: Maglione Paul J. , Xu Jiayong , Casadevall Arturo , Chan John
Published: April 2014

The critical role of cellular immunity during tuberculosis (TB) has been extensively studied, but the impact of Abs upon this infection remains poorly defined. Previously, we demonstrated that B cells are required for optimal protection in Mycobacterium tuberculosis-infected mice. FcγR modulate immunity by engaging Igs produced by B cells. We report that C57BL/6 mice deficient in inhibitory FcγRIIB (RIIB−/−) manifested enhanced mycobacterial containment and diminished immunopathology compared with wild-type controls. These findings corresponded with enhanced pulmonary Th1 responses, evidenced by increased IFN-γ-producing CD4+ T cells, and elevated expression of MHC class II and costimulatory molecules B7-1 and B7-2 in the lungs. Upon M. tuberculosis infection and immune complex engagement, RIIB−/− macrophages produced more of the p40 component of the Th1-promoting cytokine IL-12. These data strongly suggest that FcγRIIB engagement can dampen the TB Th1 response by attenuating IL-12p40 production or activation of APCs. Conversely, C57BL/6 mice lacking the γ-chain shared by activating FcγR had enhanced susceptibility and exacerbated immunopathology upon M. tuberculosis challenge, associated with increased production of the immunosuppressive cytokine IL-10. Thus, engagement of distinct FcγR can divergently affect cytokine production and susceptibility during M. tuberculosis infection.
Platelet-Activating Factor Receptor Contributes to Host Defense against Pseudomonas aeruginosa Pneumonia but Is Not Essential for the Accompanying Inflammatory and Procoagulant Response
Authors: van Zoelen Marieke A. D. , Florquin Sandrine , Meijers Joost C. M. , de Beer Regina , de Vos Alex F. , de Boer Onno J. , van der Poll Tom
Published: April 2014

Pseudomonas aeruginosa is a major cause of nosocomial pneumonia, which is associated with high morbidity and mortality. Because of its ubiquitous nature and its ability to develop resistance to antibiotics, it is a problematic pathogen from a treatment perspective. Platelet-activating factor receptor (PAFR) is involved in phagocytosis of several pathogens. To determine the role of PAFR in the innate immune response to P. aeruginosa pneumonia, pafr gene-deficient (PAFR−/−) mice and normal wild-type (Wt) mice were intranasally inoculated with P. aeruginosa. PAFR deficiency impaired host defense as reflected by increased bacterial outgrowth and dissemination in mice with a targeted deletion of the PAFR gene. PAFR−/− neutrophils showed a diminished phagocytosing capacity of P. aeruginosa in vitro. Relative to Wt mice, PAFR−/− mice demonstrated increased lung inflammation and injury as reflected by histopathology, relative lung weights and total protein concentrations in bronchoalveolar lavage fluid, which was accompanied by higher levels of proinflammatory cytokines in lung homogenates and plasma. In addition, PAFR deficiency was associated with exaggerated local and systemic activation of coagulation as determined by fibrin staining of lung tissue and pulmonary and plasma concentrations of thrombin-antithrombin complexes and D-dimer. These data suggest that PAFR is an essential component of an effective host response to P. aeruginosa pneumonia, at least partly via its contribution to the phagocytic properties of professional granulocytes. Additionally, our results indicate that PAFR signaling is not essential for the induction of a local and systemic inflammatory and procoagulant response to Pseudomonas pneumonia.
γδ+ T Cells Involvement in Viral Immune Control of Chronic Human Herpesvirus 8 Infection
Authors: Barcy Serge , De Rosa Stephen C. , Vieira Jeffrey , Diem Kurt , Ikoma Minako , Casper Corey , Corey Lawrence
Published: April 2014

Little is known about what effector populations are associated with the control of human herpesvirus 8 (HHV-8) infection in vivo. We compared T lymphocyte subsets among HIV−HHV-8+ and HIV−HHV-8− infected human individuals. αβ+ T cells from HHV-8-infected individuals displayed a significantly higher percentage of differentiated effector cells among both CD4+ and CD8+ T cell subsets. HHV-8 infection was associated with significant expansion of γδ+ Vδ1 T cells expressing a differentiated effector cell phenotype in peripheral blood. In vitro stimulation of PBMC from HHV-8-infected individuals with either infectious viral particles or different HHV-8 viral proteins resulted in γδ Vδ1 T cell activation. In addition, γδ Vδ1 T cells displayed a strong reactivity against HHV-8-infected cell lines and prevented the release of infectious viral particles following the induction of lyric replication. These data indicate that γδ T cells play a role in both innate and adaptive T cell responses against HHV-8 in immunocompetent individuals.
Mast Cell-Fibroblast Interactions Induce Matrix Metalloproteinase-9 Release from Fibroblasts: Role for IgE-Mediated Mast Cell Activation
Authors: Abel Melanie , Vliagoftis Harissios
Published: April 2014

Mast cells adhere to fibroblasts, but the biological effects of adhesion are not well understood. We hypothesized that these adhesive interactions are important for tissue remodeling through the release of matrix metalloproteinases (MMP). Murine bone marrow cultured mast cells (BMCMC) were cocultured with NIH-3T3 fibroblasts or murine lung fibroblasts (CCL-206) and supernatants analyzed for MMP-9 release by gelatin zymography. Coculture of BMCMC for 24 h with NIH-3T3 or CCL-206 fibroblasts increased the release of MMP-9 from fibroblasts by 1.7 ± 0.2 and 2.0 ± 0.7-fold, respectively. Coculture of BMCMC and fibroblasts in the presence of IgE increased further MMP-9 release, which was released by fibroblasts. MMP-9 release was dependent on TNF released from IgE activated BMCMC and on adhesive interactions between BMCMC and fibroblasts. Increased MMP-9 release was also p44/42-dependent, as was MMP-9 up-regulation during coculture of fibroblasts with resting BMCMC. Finally, IgE injection into the mouse ear increased MMP-9 content of the ear tissue in the absence of Ag, indicating that IgE-mediated remodeling may play a pathogenic role in allergic conditions even in the absence of exposure to allergens. In conclusion, mast cell-fibroblast interactions induce the release of proteases important for tissue remodeling, such as MMP-9. MMP-9 release was further increased in the presence of IgE during coculture, suggesting a role for mast cell-fibroblast interactions in atopic conditions.
IL-4 Is a Critical Determinant in the Generation of Allergic Inflammation Initiated by a Constitutively Active Stat6
Authors: Sehra Sarita , Bruns Heather A. , Ahyi Ayele-Nati N. , Nguyen Evelyn T. , Schmidt Nathan W. , Michels E. Grace , von Bülow Götz-Ulrich , Kaplan Mark H.
Published: April 2014

IL-4 is required for the pathogenesis of atopic diseases and immune regulation. Stat6 is critical for IL-4-induced gene expression and Th cell differentiation. Recently, we have generated mice expressing a mutant Stat6 (Stat6VT) under control of the CD2 locus control region that is transcriptionally active independent of IL-4 stimulation. To determine whether active Stat6 in T cells is sufficient to alter immune regulation in vivo, we mated Stat6VT transgenic mice to IL-4-deficient mice. Stat6VT expression in IL-4-deficient lymphocytes was sufficient to alter lymphocyte homeostasis and promote Th2 differentiation in vitro. HyperTh2 levels in Stat6 transgenic mice correlated with an atopic phenotype that manifested as blepharitis and pulmonary inflammation with a high level of eosinophilic infiltration. In the absence of endogenous IL-4, Stat6VT transgenic mice were protected from allergic inflammation. Thus, in mice with hyperTh2 immune responses in vivo, IL-4 is a critical effector cytokine.
Loss of ABCG1 Results in Chronic Pulmonary Inflammation
Authors: Baldán Ángel , Gomes Aldrin V. , Ping Peipei , Edwards Peter A.
Published: April 2014

ABCG1, a member of the ATP-binding cassette transporter superfamily, is highly expressed in multiple cells of the lung. Loss of ABCG1 results in severe pulmonary lipidosis in mice, with massive deposition of cholesterol in both alveolar macrophages and type 2 cells and the accumulation of excessive surfactant phospholipids. These observations are consistent with ABCG1 controlling cellular sterol metabolism. Herein, we report on the progressive and chronic inflammatory process that accompanies the lipidosis in the lungs of Abcg1−/− mice. Compared with wild-type animals, the lungs of aged chow-fed mice deficient in ABCG1 show distinctive signs of inflammation that include macrophage accumulation, lymphocytic infiltration, hemorrhage, eosinophilic crystals, and elevated levels of numerous cytokines and cytokine receptors. Analysis of bronchoalveolar lavages obtained from Abcg1−/− mice revealed elevated numbers of foamy macrophages and leukocytes and the presence of multiple markers of inflammation including crystals of chitinase-3-like proteins. These data suggest that cholesterol and/or cholesterol metabolites that accumulate in Abcg1−/− lungs can trigger inflammatory signaling pathways. Consistent with this hypothesis, the expression of a number of cytokines was found to be significantly increased following increased cholesterol delivery to either primary peritoneal macrophages or Raw264.7 cells. Finally, cholesterol loading of primary mouse macrophages induced cytokine mRNAs to higher levels in Abcg1−/−, as compared with wild-type cells. These results demonstrate that ABCG1 plays critical roles in pulmonary homeostasis, balancing both lipid/cholesterol metabolism and inflammatory responses.
Cutting Edge: A Naturally Occurring Mutation in CD1e Impairs Lipid Antigen Presentation
Authors: Tourne Sylvie , Maitre Blandine , Collmann Anthony , Layre Emilie , Mariotti Sabrina , Signorino-Gelo François , Loch Caroline , Salamero Jean , Gilleron Martine , Angénieux Catherine , Cazenave Jean-Pierre , Mori Lucia , Hanau Daniel , Puzo Germain , De Libero Gennaro , de la Salle Henri
Published: April 2014

The human CD1a–d proteins are plasma membrane molecules involved in the presentation of lipid Ags to T cells. In contrast, CD1e is an intracellular protein present in a soluble form in late endosomes or lysosomes and is essential for the processing of complex glycolipid Ags such as hexamannosylated phosphatidyl-myo-inositol, PIM6. CD1e is formed by the association of β2-microglobulin with an α-chain encoded by a polymorphic gene. We report here that one variant of CD1e with a proline at position 194, encoded by allele 4, does not assist PIM6 presentation to CD1b-restricted specific T cells. The immunological incompetence of this CD1e variant is mainly due to inefficient assembly and poor transport of this molecule to late endosomal compartments. Although the allele 4 of CD1E is not frequent in the population, our findings suggest that homozygous individuals might display an altered immune response to complex glycolipid Ags.
Non-T Cell Activation Linker Promotes Mast Cell Survival by Dampening the Recruitment of SHIP1 by Linker for Activation of T Cells
Authors: Roget Karine , Malissen Marie , Malbec Odile , Malissen Bernard , Daëron Marc
Published: April 2014

The linker for activation of T cells (LAT) and the non-T cell activation linker (NTAL) are two transmembrane adapters which organize IgE receptor (FcεRI) signaling complexes in mast cells. LAT positively regulates, whereas NTAL negatively regulates mast cell activation. We previously found that the four distal tyrosines of LAT can generate negative signals. We show here that two of these tyrosines provide two binding sites for SHIP1, that LAT recruits SHIP1 in vivo, and that SHIP1 recruitment is enhanced in NTAL-deficient cells. We show that NTAL negatively regulates mast cell activation by decreasing the recruitment, by LAT, of molecules involved in FcεRI-dependent positive signaling. We show that NTAL also decreases the recruitment of SHIP1 by LAT, leading to an increased phosphorylation of the antiapoptotic molecule Akt, and positively regulates mast cell survival. We finally show that the positive effect of NTAL on Akt phosphorylation and mast cell survival requires LAT. Our data thus document the mechanisms by which LAT and NTAL can generate both positive and negative signals which differentially regulate mast cell activation and survival. They also provide molecular bases for the recruitment of SHIP1 in FcεRI signaling complexes. SHIP1 is a major negative regulator of mast cell activation and, hence, of allergic reactions.
E2F4 Modulates Differentiation and Gene Expression in Hematopoietic Progenitor Cells during Commitment to the Lymphoid Lineage
Authors: Enos Megan E. , Bancos Simona A. , Bushnell Timothy , Crispe Ian N.
Published: April 2014

The E2F4 protein is involved in gene repression and cell cycle exit, and also has poorly understood effects in differentiation. We analyzed the impact of E2F4 deficiency on early steps in mouse hematopoietic development, and found defects in early hematopoietic progenitor cells that were propagated through common lymphoid precursors to the B and T lineages. In contrast, the defects in erythromyeloid precursor cells were self-correcting over time. This suggests that E2F4 is important in early stages of commitment to the lymphoid lineage. The E2F4-deficient progenitor cells showed reduced expression of several key lymphoid-lineage genes, and overexpression of two erythromyeloid lineage genes. However, we did not detect effects on cell proliferation. These findings emphasize the significance of E2F4 in controlling gene expression and cell fate.
Allelic and Isotypic Light Chain Inclusion in Peripheral B Cells from Anti-DNA Antibody Transgenic C57BL/6 and BALB/c Mice
Authors: Witsch Esther J. , Bettelheim Eldad
Published: April 2014

Most mature B lymphocytes express one BCR L chain, κ or λ, but recent work has shown that there are exceptions in that some B lymphocytes express both κ and λ and some even bear two different κ L chains. Using the anti-DNA H chain-transgenic mouse, 56R, we find that B cells with pre-existing autoreactivity are especially subject to L chain inclusion. Specifically, we show that isotypic and allelic inclusion enables autoreactive B cells to bypass central tolerance giving rise to B cells that retain dangerous features. One receptor in dual receptor B cells is an editor L chain, i.e., neutralizes or alters self-reactivity of the 56R H chain transgene. We compare the 56R mouse when on the C57/BL/6 background, a strain prone to autoimmunity, with that of 56R when on the BALB/c background, a strain that resists autoimmunity. In the B6.56R mouse, polyreactive B cells with dual L chain move to the follicular B cell compartment. Their localization in the follicular compartment may explain the ease with which B cells in the B6.56R differentiate into autoantibody-producing plasma cells. Likewise, in the BALB/c.56R mouse, dual L chain B cells are found in the follicular B cell compartment. Yet, the lack of autoantibody-producing plasma cells in the BALB/c.56R suggests that postfollicular tolerance checkpoints are intact. The Jκ usage in dual κ L chain B cells suggests increased receptor editing activity and is consistent with the expected distribution of Jκ genes in our computational model for random selection of Jκ.
Identification of RNA Sequence Motifs Stimulating Sequence-Specific TLR8-Dependent Immune Responses
Authors: Forsbach Alexandra , Nemorin Jean-Guy , Montino Carmen , Müller Christian , Samulowitz Ulrike , Vicari Alain P. , Jurk Marion , Mutwiri George K. , Krieg Arthur M. , Lipford Grayson B. , Vollmer Jörg
Published: April 2014

The TLRs 7, 8, and 9 stimulate innate immune responses upon recognizing pathogen nucleic acids. U-rich RNA sequences were recently discovered that stimulate human TLR7/8-mediated or murine TLR7-mediated immune effects. In this study we identified single-stranded RNA sequences containing defined sequence motifs that either preferentially activate human TLR8-mediated as opposed to TLR7- or TLR7/8-mediated immune responses. The identified TLR8 RNA motifs signal via TLR8 and fail to induce IFN-α from TLR7-expressing plasmacytoid dendritic cells but induce the secretion of Th1-like and proinflammatory cytokines from TLR8-expressing immune cells such as monocytes or myeloid dendritic cells. In contrast, RNA sequences containing the TLR7/8 motif signal via TLR7 and TLR8 and stimulate cytokine secretion from both TLR7- and TLR8-positive immunocytes. The TLR8-specific RNA sequences are able to trigger cytokine responses from human and bovine but not from mouse, rat, and porcine immune cells, suggesting that these species lack the capability to respond properly to TLR8 RNA ligands. In summary, we describe two classes of single-stranded TLR7/8 and TLR8 RNA agonists with diverse target cell and species specificities and immune response profiles.
A Lupus-Suppressor BALB/c Locus Restricts IgG2 Autoantibodies without Altering Intrinsic B Cell-Tolerance Mechanisms
Authors: Tarasenko Tatyana , Kole Hemanta K. , Bolland Silvia
Published: April 2014

FcγR2B-deficient mice develop autoantibodies and glomerulonephritis with a pathology closely resembling human lupus when on the C57BL/6 (B6) background. The same mutation on the BALB/c background does not lead to spontaneous disease, suggesting differences in lupus susceptibility between the BALB/c and B6 strains. An F2 genetic analysis from a B6/BALB cross identified regions from the B6 chromosomes 12 and 17 with positive linkage for IgG autoantibodies. We have generated a congenic strain that contains the suppressor allele from the BALB/c chromosome 12 centromeric region (sbb2a) in an otherwise B6.FcγR2B−/− background. None of the B6.FcγR2B−/−sbb2a/a mice tested have developed IgG autoantibodies in the serum or autoimmune pathology. Mixed bone marrow reconstitution experiments indicate that sbb2a is expressed in non-B bone marrow-derived cells and acts in trans. sbb2a does not alter L chain editing frequencies of DNA Abs in the 3H9H/56R H chain transgenic mice, but the level of IgG2a anti-DNA Abs in the serum is reduced. Thus, sbb2a provides an example of a non-MHC lupus-suppressor locus that protects from disease by restricting the production of pathogenic IgG isotypes even in backgrounds with inefficient Ab editing checkpoints.
Intestinal Epithelial Cell Up-Regulation of LY6 Molecules during Colitis Results in Enhanced Chemokine Secretion
Authors: Flanagan Ken , Modrusan Zora , Cornelius Jennine , Chavali Arvind , Kasman Ian , Komuves Laszlo , Mo Lian , Diehl Lauri
Published: April 2014

In the healthy colon, intestinal epithelial cells (IEC) form a physical barrier separating the myriad of gut Ags from the cells of the immune system. Simultaneously, IEC use several mechanisms to actively maintain immunologic tolerance to nonpathogenic Ags, including commensal bacteria. However, during inflammatory bowel disease (IBD), the line of defense provided by IEC is breached, resulting in uncontrolled immune responses. As IEC are a principal mediator of immune responses in the gut, we were interested in discerning the gene expression pattern of IEC during development and progression of IBD. Laser capture microdissection and microarray analysis were combined to identify the LY6 superfamily as strongly up-regulated genes in inflamed IEC of the colon in two models of murine colitis. Surface expression of LY6A and LY6C on IEC is induced by several cytokines present within the colitic gut, including IL-22 and IFN-γ. Furthermore, cross-linking of LY6C results in production of a number of chemokines which are known to be involved in the immunopathogenesis of IBD. Increased chemokine production was cholesterol dependent, suggesting a role for lipid raft structures in the mechanism. As such, LY6 molecules represent novel targets to down-regulate chemokine expression in the colon and limit subsequent inflammation associated with IBD.
Lipopolysaccharide-Activated IL-10-Secreting Dendritic Cells Suppress Experimental Autoimmune Uveoretinitis by MHCII-Dependent Activation of CD62L-Expressing Regulatory T Cells
Authors: Lau Annie W. T. , Biester Sabine , Cornall Richard J. , Forrester John V.
Published: April 2014

Dendritic cells (DC) are key regulators of immune responses. Mature DC are traditionally considered to be immunogenic, although there is accumulating evidence that they can also be tolerogenic and induce Ag-specific regulatory T cells (Tregs). However, the mechanism of this Treg induction and the site of Treg action in vivo are yet to be defined. In this study, using the experimental model of interphotoreceptor retinoid-binding protein peptide (1–20)-induced experimental autoimmune uveoretinitis, we show that s.c. inoculation of IRBP-peptide-pulsed IL-10-producing LPS-activated mature DC (IL-10-DC) at one site (the cervical region) suppresses autoimmunity induced at a separate site (the inguinal region). Our data show that s.c. IL-10-DC correlates with an increase in the number of CD4+CD25+Foxp3+ Tregs at the DC-draining lymph nodes (DC-dLN). However, although MHCII−/− IL-10-DC also induces Treg expansion at this DC-dLN, they failed to suppress experimental autoimmune uveoretinitis. Furthermore, unlike wild-type IL-10-DC, MHCII−/− IL-10-DC did not correlate with an increase in the percentage of Tregs expressing CD62L at the DC-dLN, nor did they associate with an increase in Treg number at a distal site. Similar effects were also observed after s.c. hen egg lysozyme-pulsed IL-10-DC, which produced a strong reduction in the number and activation of proliferating Ag-specific CD4+ 3A9 T effector cells. We therefore propose that IL-10-DC require MHCII-dependent Ag presentation, and hence TCR ligation, to promote CD62L-mediated trafficking of Tregs to the site of T effector cell priming, where they suppress autoimmunity.
Potent Antimycobacterial Activity of Mouse Secretory Leukocyte Protease Inhibitor
Authors: Nishimura Junichi , Saiga Hiroyuki , Sato Shintaro , Okuyama Megumi , Kayama Hisako , Kuwata Hirotaka , Matsumoto Sohkichi , Nishida Toshirou , Sawa Yoshiki , Akira Shizuo , Yoshikai Yasunobu , Yamamoto Masahiro , Takeda Kiyoshi
Published: April 2014

Secretory leukocyte protease inhibitor (SLPI) has multiple functions, including inhibition of protease activity, microbial growth, and inflammatory responses. In this study, we demonstrate that mouse SLPI is critically involved in innate host defense against pulmonary mycobacterial infection. During the early phase of respiratory infection with Mycobacterium bovis bacillus Calmette-Guérin, SLPI was produced by bronchial and alveolar epithelial cells, as well as alveolar macrophages, and secreted into the alveolar space. Recombinant mouse SLPI effectively inhibited in vitro growth of bacillus Calmette-Guérin and Mycobacterium tuberculosis through disruption of the mycobacterial cell wall structure. Each of the two whey acidic protein domains in SLPI was sufficient for inhibiting mycobacterial growth. Cationic residues within the whey acidic protein domains of SLPI were essential for disruption of mycobacterial cell walls. Mice lacking SLPI were highly susceptible to pulmonary infection with M. tuberculosis. Thus, mouse SLPI is an essential component of innate host defense against mycobacteria at the respiratory mucosal surface.
Pannexin-1-Mediated Intracellular Delivery of Muramyl Dipeptide Induces Caspase-1 Activation via Cryopyrin/NLRP3 Independently of Nod2
Authors: Marina-García Noemí , Franchi Luigi , Kim Yun-Gi , Miller Douglas , McDonald Christine , Boons Geert-Jan , Núñez Gabriel
Published: April 2014

Muramyl dipeptide (MDP), the microbial activator of nucleotide-binding oligomerization domain 2 (Nod2), induces NF-κB and MAPK activation, leading to the production of multiple anti-bacterial and proinflammatory molecules. In addition, MDP has been implicated in IL-1β secretion through the regulation of caspase-1. However, the mechanisms that mediate caspase-1 activation and IL-1β secretion in response to MDP stimulation remain poorly understood. We show here that fluorescent MDP molecules are internalized in primary macrophages and accumulate in granular structures that colocalize with markers of acidified endosomal compartments. The uptake of MDP was Nod2-independent. Upon ATP stimulation, labeled MDP was rapidly released from acidified vesicles into the cytosol, a process that required functional pannexin-1. Caspase-1 activation induced by MDP and ATP required pannexin-1 and Cryopyrin but was independent of Nod2. Conversely, induction of pro-IL-1β mRNA by MDP stimulation was abolished in Nod2-deficient macrophages but unimpaired in macrophages lacking Cryopyrin. These studies demonstrate a Nod2-independent mechanism mediated through pore-forming pannexin-1 that is required for intracellular delivery of MDP to the cytosol and caspase-1 activation. Furthermore, the work provides evidence for distinct roles of Nod2 and Cryopyrin in the regulation of MDP-induced caspase-1 activation and IL-1β secretion.
IL-10 and TGF-β Control the Establishment of Persistent and Transmissible Infections Produced by Leishmania tropica in C57BL/6 Mice
Authors: Anderson Charles F. , Lira Rosalia , Kamhawi Shaden , Belkaid Yasmine , Wynn Thomas A. , Sacks David
Published: April 2014

Leishmania tropica is the causative agent of Old World anthroponotic cutaneous leishmaniasis, which is characterized by lesions that take an extended period of time to heal, often resulting in disfiguring scars, and are more refractory to treatment than leishmaniasis caused by Leishmania major. Immunologic studies involving experimental animal models of L. tropica infection are virtually nonexistent. In the current study, infectious-stage L. tropica were used to establish dermal infections in C57BL/6 and BALB/c mice. In both strains, the lesions were slow to develop and showed minimal pathology. They nonetheless contained a stable number of between 104 and 105 parasites for over 1 year, which were efficiently picked up by a natural sand fly vector, Phlebotomus sergenti. Control of parasite growth depended on the development of a Th1 response, as C57BL/6 mice genetically deficient in Th1 cytokines and BALB/c mice treated with Abs to IFN-γ harbored significantly more parasites. By contrast, IL-10-deficient mice harbored significantly fewer parasites throughout the infection. To further study the immunologic mechanisms that may prevent efficient clearance of the parasites, IL-10 and TGF-β signaling were abrogated during the chronic phase of infection in wild-type C57BL/6 mice. Distinct from chronic L. major infection, IL-10 blockade alone had no effect on L. tropica, but required simultaneous treatment with anti-TGF-β Abs to promote efficient parasite clearance from the infection site. Thus, chronic infection with L. tropica appears to be established via multiple suppressive factors, which together maintain the host as a long-term reservoir of infection for vector sand flies.
Role of Polymorphonuclear Neutrophils on Infectious Complications Stemming from Enterococcus faecalis Oral Infection in Thermally Injured Mice
Authors: Tsuda Yasuhiro , Shigematsu Kenji , Kobayashi Makiko , Herndon David N. , Suzuki Fujio
Published: April 2014

Thermally injured mice are susceptible to Enterococcus faecalis translocation. In this study, the role of polymorphonuclear neutrophils (PMN) on the development of sepsis stemming from E. faecalis translocation was studied in SCID-beige (SCIDbg) mice depleted of PMN (SCIDbgN mice) or macrophages (Mφ) and PMN (SCIDbgMN mice). Sepsis was not developed in SCIDbgN mice orally infected with E. faecalis, while the orally infected pathogen spread systemically in the same mice inoculated with PMN from thermally injured mice (TI-PMN). SCIDbgMN mice were shown to be greatly susceptible to sepsis caused by E. faecalis translocation, while orally infected E. faecalis did not spread into sepsis in the same mice that were previously inoculated with Mφ from unburned SCIDbg mice (resident Mφ). In contrast, orally infected E. faecalis spread systemically in SCIDbgMN mice inoculated with resident Mφ and TI-PMN, while all SCIDbgMN mice inoculated in combination with resident Mφ and PMN from unburned SCIDbg mice survived after the infection. After cultivation with TI-PMN in a dual-chamber transwell, resident Mφ converted to alternatively activated Mφ, which are inhibitory on the generation of classically activated Mφ (typical effector cells in host antibacterial innate immunities). TI-PMN were characterized as immunosuppressive PMN (PMN-II) with abilities to produce cc-chemokine ligand-2 and IL-10. These results indicate that PMN-II appearing in response to burn injury impair host antibacterial resistance against sepsis stemming from E. faecalis translocation through the conversion of resident Mφ to alternatively activated Mφ.