bluuebunny/crossref_metadata_2025 huggingface dataset:
Dual Role of the Jak1 FERM and Kinase Domains in Cytokine Receptor Binding and in Stimulation-Dependent Jak Activation
Authors: Haan Serge , Margue Christiane , Engrand Arnaud , Rolvering Catherine , Schmitz-Van de Leur Hildegard , Heinrich Peter C. , Behrmann Iris , Haan Claude
Published: April 2014

Jak1 is a tyrosine kinase that noncovalently forms tight complexes with a variety of cytokine receptors and is critically involved in signal transduction via cytokines. Jaks are predicted to have a 4.1, ezrin, radixin, moesin (FERM) domain at their N terminus. FERM domains are composed of three structurally unrelated subdomains (F1, F2, and F3) which are in close contact to one another and form the clover-shaped FERM domain. We generated a model structure of the Jak1 FERM domain, based on solved FERM structures and the alignments with other FERM domains. To destabilize different subdomains and to uncover their exact function, we mutated specific hydrophobic residues conserved in FERM domains and involved in hydrophobic core interactions. In this study, we show that the structural integrity of the F2 subdomain of the FERM domain of Jak1 is necessary to bind the IFN-γRα. By mutagenesis of hydrophobic residues in the hydrophobic core between the three FERM subdomains, we find that the structural context of the FERM domain is necessary for the inhibition of Jak1 phosphorylation. Thus, FERM domain mutations can have repercussions on Jak1 function. Interestingly, a mutation in the kinase domain (Jak1-K907E), known to abolish the catalytic activity, also leads to an impaired binding to the IFN-γRα when this mutant is expressed at endogenous levels in U4C cells. Our data show that the structural integrity of both the FERM domain and of the kinase domain is essential for both receptor binding and catalytic function/autoinhibition.
IFN-α Skews Monocytes into CD56+-Expressing Dendritic Cells with Potent Functional Activities In Vitro and In Vivo
Authors: Papewalis Claudia , Jacobs Benedikt , Wuttke Margret , Ullrich Evelyn , Baehring Thomas , Fenk Roland , Willenberg Holger S. , Schinner Sven , Cohnen Mathias , Seissler Jochen , Zacharowski Kai , Scherbaum Werner A. , Schott Matthias
Published: April 2014

The antitumor effect of IFN-α is mediated by the activation of CTLs, NK cells, and the generation of highly potent Ag-presenting dendritic cells (IFN-DCs). In this study, we show that IFN-DCs generated in vitro from monocytes express CD56 on their surface, a marker which has been thought to be specific for NK cells. FACS analyses of CD56+ and CD56− IFN-DCs showed a nearly identical pattern for most of the classical DC markers. Importantly, however, only CD56+ IFN-DCs exhibited cytolytic activity up to 24% that could almost completely be blocked (−81%) after coincubation with anti-TRAIL. Intracytoplasmatic cytokine staining revealed that the majority of IFN-DCs independently of their CD56 expression were IFN-γ positive as well. In contrast, CD56+ IFN-DCs showed stronger capacity in stimulating allogenic T cells compared with CD56− IFN-DC. Based on these results, five patients with metastasized medullary thyroid carcinoma were treated for the first time with monocyte-derived tumor Ag-pulsed IFN-DCs. After a long term follow-up (in mean 37 mo) all patients are alive. Immunohistochemical analyses of delayed-type hypersensitivity skin reaction showed a strong infiltration with CD8+ cells. In two patients no substantial change in tumor morphology was detected. Importantly, by analyzing PBMCs, these patients also showed an increase of Ag-specific IFN-γ-secreting T cells. In summary, we here describe for the first time that cytotoxic activity of IFN-DCs is mainly mediated by an IFN-DC subset showing partial phenotypic and functional characteristics of NK cells. These cells represent another mechanism of the antitumor effect induced by IFN-α.
A Peptide That Ameliorates Lupus Up-Regulates the Diminished Expression of Early Growth Response Factors 2 and 3
Authors: Sela Uri , Dayan Molly , Hershkoviz Rami , Lider Ofer , Mozes Edna
Published: April 2014

Expansion of autoreactive T cells and their resistance to anergy was demonstrated in systemic lupus erythematosus (SLE). A pair of transcription factors, early growth response 2 (Egr-2) and 3 (Egr-3), are negative regulators of T cell activation that were shown to be important in anergy. A peptide (designated hCDR1 for human CDR1) based on the CDR-1 of an anti-DNA Ab ameliorated SLE in both induced and spontaneous lupus models. Our objectives were to determine the expression levels of Egr-2 and Egr-3 in autoreactive T cells following immunization with the lupus-inducing anti-DNA Ab that bears a common Id designated 16/6Id and also in a full-blown SLE and to determine the effect of hCDR1 on these transcription factors. We demonstrated diminished expression levels of Egr-2 and Egr-3 mRNA both early after immunization with the 16/6Id and in SLE-afflicted (NZB × NZW)F1 (New Zealand Black and New Zealand White) mice. Furthermore, by down-regulating Akt phosphorylation and up-regulating TGFβ secretion, treatment with hCDR1 significantly up-regulated Egr-2 and Egr-3 expression. This was associated with an increased expression of the E3 ligase Cbl-b. Inhibition of Akt in T cells of immunized mice decreased, whereas silencing of the Egr-2 and Egr-3 in T cells of hCDR1-treated mice increased IFN-γ secretion. Thus, hCDR1 down-regulates Akt phosphorylation, which leads to up-regulated expression of T cell Egr-2 and Egr-3, resulting in the inhibition of IFN-γ secretion that is required for the maintenance of SLE.
Human Mesenchymal Stem Cells License Adult CD34+ Hemopoietic Progenitor Cells to Differentiate into Regulatory Dendritic Cells through Activation of the Notch Pathway
Authors: Li Yin-Ping , Paczesny Sophie , Lauret Evelyne , Poirault Sonia , Bordigoni Pierre , Mekhloufi Fatiha , Hequet Olivier , Bertrand Yves , Ou-Yang Jing-Ping , Stoltz Jean-François , Miossec Pierre , Eljaafari Assia
Published: April 2014

The mechanisms underlying the immunomodulatory functions of mesenchymal stem cells (MSC) on dendritic cells (DC) have been shown to involve soluble factors, such as IL-6 or TGF-β, or cell-cell contact, or both depending on the report referenced. In this study, we intend to clarify these mechanisms by examining the immunosuppressive effect of human adult MSC on adult DC differentiated from CD34+ hemopoietic progenitor cells (HPC). MSC have been shown to inhibit interstitial DC differentiation from monocytes and umbilical CD34+ HPC. In this study, we confirm that MSC not only halt interstitial DC but also Langerhans cell differentiation from adult CD34+ HPC, as assessed by the decreased expression of CD1a, CD14, CD86, CD80, and CD83 Ags on their cell surface. Accordingly, the functional capacity of CD34+ HPC-derived DC (CD34-DC) to stimulate alloreactive T cells was impaired. Furthermore, we showed that 1) MSC inhibited commitment of CD34+ HPC into immature DC, but not maturation of CD34-DC, 2) this inhibitory effect was reversible, and 3) DC generated in coculture with MSC (MSC-DC) induced the generation of alloantigen-specific regulatory T cells following secondary allostimulation. Conditioned medium from MSC cultures showed some inhibitory effect independent of IL-6, M-CSF, and TGF-β. In comparison, direct coculture of MSC with CD34+ HPC resulted in much stronger immunosuppressive effect and led to an activation of the Notch pathway as assessed by the overexpression of Hes1 in MSC-DC. Finally, DAPT, a γ-secretase inhibitor that inhibits Notch signaling, was able to overcome MSC-DC defects. In conclusion, our data suggest that MSC license adult CD34+ HPC to differentiate into regulatory DC through activation of the Notch pathway.
The Soluble Leukocyte-Associated Ig-Like Receptor (LAIR)-2 Antagonizes the Collagen/LAIR-1 Inhibitory Immune Interaction
Authors: Lebbink Robert Jan , van den Berg Maaike C. W. , de Ruiter Talitha , Raynal Nicolas , van Roon Joel A. G. , Lenting Peter J. , Jin Boquan , Meyaard Linde
Published: April 2014

Leukocyte-associated Ig-like receptor (LAIR)-1 is a collagen-receptor that inhibits immune cell function upon collagen binding. Next to LAIR-1, the human genome encodes LAIR-2, a putative soluble homolog. In this study we show, for the first time, that the LAIR-2 gene is broadly transcribed in human PBMC, mirroring the expression profile of LAIR-1. LAIR-2 protein is expressed as a soluble receptor exhibiting high affinity for various collagen molecules to which it binds in a hydroxyproline-dependent manner. In vitro stimulation of PBMC induces secretion of LAIR-2. We detect high amounts of LAIR-2 in urine of pregnant women, indicating that the soluble receptor is indeed produced in vivo and can be cleared from the body via urine. Furthermore, LAIR-2 levels are increased in synovial fluid of patients with rheumatoid arthritis as compared with osteoarthritis patients. We hypothesize that soluble LAIR-2 may function as a natural competitor for LAIR-1, thereby regulating its inhibitory potential. Indeed, LAIR-2 prevents binding of human LAIR-1 to collagens and LAIR-1 cross-linking in vitro, suggesting that the protein has an immunoregulatory function in vivo. Hence, we reveal a novel mechanism of immune regulation by a soluble LAIR receptor regulating the inhibitory potential of the membrane-bound LAIR-1 via competition for ligands.
Infection with Trypanosoma cruzi Restricts the Repertoire of Parasite-Specific CD8+ T Cells Leading to Immunodominance
Authors: Tzelepis Fanny , de Alencar Bruna C. G. , Penido Marcus L. O. , Claser Carla , Machado Alexandre V. , Bruna-Romero Oscar , Gazzinelli Ricardo T. , Rodrigues Mauricio M.
Published: April 2014

Interference or competition between CD8+ T cells restricted by distinct MHC-I molecules can be a powerful means to establish an immunodominant response. However, its importance during infections is still questionable. In this study, we describe that following infection of mice with the human pathogen Trypanosoma cruzi, an immunodominant CD8+ T cell immune response is developed directed to an H-2Kb-restricted epitope expressed by members of the trans-sialidase family of surface proteins. To determine whether this immunodominance was exerted over other non-H-2Kb-restricted epitopes, we measured during infection of heterozygote mice, immune responses to three distinct epitopes, all expressed by members of the trans-sialidase family, recognized by H-2Kb-, H-2Kk-, or H-2Kd-restricted CD8+ T cells. Infected heterozygote or homozygote mice displayed comparably strong immune responses to the H-2Kb-restricted immunodominant epitope. In contrast, H-2Kk- or H-2Kd-restricted immune responses were significantly impaired in heterozygote infected mice when compared with homozygote ones. This interference was not dependent on the dose of parasite or the timing of infection. Also, it was not seen in heterozygote mice immunized with recombinant adenoviruses expressing T. cruzi Ags. Finally, we observed that the immunodominance was circumvented by concomitant infection with two T. cruzi strains containing distinct immunodominant epitopes, suggesting that the operating mechanism most likely involves competition of T cells for limiting APCs. This type of interference never described during infection with a human parasite may represent a sophisticated strategy to restrict priming of CD8+ T cells of distinct specificities, avoiding complete pathogen elimination by host effector cells, and thus favoring host parasitism.
Inhibition of HIV-1 Infectivity through an Innate Mechanism Involving Naturally Occurring IgM Anti-Leukocyte Autoantibodies
Authors: Lobo Peter I. , Schlegel Kailo H. , Yuan Wen , Townsend Gregory C. , White Jennifer A.
Published: April 2014

In prior studies, we show that naturally occurring IgM anti-leukocyte autoantibodies (IgM-ALA) bind to CD3, CD4, CCR5, and CXCR4 receptors. These observations prompted us to determine whether IgM-ALA have a role in inhibiting HIV-1 infectivity by inhibiting viral entry into cells. We show that purified IgM, but not IgG, from individual sera of both normal and HIV-1 infected individuals is highly inhibitory (>95%) to HIV-1 viral infectivity both in vitro using PHA plus IL-2 activated PBL and in vivo using the human PBL-SCID mouse. Inhibition was observed with physiological doses of purified serum IgM and even after IgM was added 3 days postinfection in the in vitro assays. Absorbing purified serum IgM either with leukocytes or immobilized recombinant CD4 significantly decreased (>80%) the inhibitory effect on HIV-1 infectivity. IgM inhibited by >90% syncytia formation with the X4-IIIB infected SupT-1 cells indicating therefore that IgM inhibits viral attachment to core-receptors. IgM mediated anti-HIV-1 activity was highly specific as only certain IgM-ALA, obtained from human B cell clones inhibited HIV-1. IgM from certain HIV-1 infected individuals were not inhibitory to some R5-HIV-1 viral strains indicating that certain HIV-IgM may lack Abs reactive to strain specific coreceptor epitopes. These data indicate that an innate immune mechanism which is present from birth i.e., IgM-ALA, has a role in inhibiting HIV-1 viral entry into cells. Validation of this data with other in vivo models will be needed to determine whether in vivo administration or enhancement of IgM-ALA, e.g., through a vaccine, could prolong the asymptomatic state in HIV-1 infected individuals.
Vitamin A Deficiency Decreases and High Dietary Vitamin A Increases Disease Severity in the Mouse Model of Asthma
Authors: Schuster Gertrud U. , Kenyon Nicholas J. , Stephensen Charles B.
Published: April 2014

The Th1/Th2 paradigm has become an important issue in the pathogenesis of asthma, characterized by normal Th1 and elevated Th2 cytokine expression. Vitamin A deficiency (VAD) can produce a Th1 bias, whereas high-level dietary vitamin A can promote a Th2 bias. We used the OVA exposure mouse model to determine the contributions of vitamin A-deficient, control (4IU/g), and high-level vitamin A (250-IU/g) diets to the development of allergic airway inflammation and hyperresponsiveness. VAD reduced serum IgE and IgG1 responses, pulmonary eosinophilia, and the levels of IL-4 and IL-5 in bronchoalveolar lavage specimens, whereas the 250-IU/g diet increased serum IgE. Also, VAD blocked pulmonary hyperresponsiveness following methacholine challenge while the 250-IU/g diet exacerbated pulmonary hyperresponsiveness. In conclusion, VAD diminished and high-level dietary vitamin A enhanced the development of experimental asthma in this model system. These data suggest that excessive intake of vitamin A may increase the risk or severity of asthma in industrialized countries whereas vitamin A deficiency continues to increase mortality from infectious diseases in developing countries.
Activation of Peroxisome Proliferator-Activated Receptor γ (PPARγ) Suppresses Rho GTPases in Human Brain Microvascular Endothelial Cells and Inhibits Adhesion and Transendothelial Migration of HIV-1 Infected Monocytes
Authors: Ramirez Servio H. , Heilman David , Morsey Brenda , Potula Raghava , Haorah James , Persidsky Yuri
Published: April 2014

Under inflammatory conditions (including HIV-1 encephalitis and multiple sclerosis), activated brain endothelium enhances the adhesion and transmigration of monocytes across the blood-brain barrier (BBB). Synthetic ligands that activate the peroxisome proliferator-activated receptors (PPARs) have anti-inflammatory properties, and PPAR stimulation prevents the interaction of leukocytes with cytokine stimulated-endothelium. However, the mechanism underlying these effects of PPAR ligands and their ability to intervene with leukocyte adhesion and migration across brain endothelial cells has yet to be explored. For the first time, using primary human brain endothelial cells (BMVEC), we demonstrated that monocyte adhesion and transendothelial migration across inflamed endothelium were markedly reduced by PPARγ activation. In contrast to non-brain-derived endothelial cells, PPARα activation in the BMVEC had no significant effect on monocyte-endothelial interaction. Previously, our work indicated a critical role of Rho GTPases (like RhoA) in BMVEC to control migration of HIV-1 infected monocytes across BBB. In this study, we show that in the BMVEC PPARγ stimulation prevented activation of two GTPases, Rac1 and RhoA, which correlated with decreased monocyte adhesion to and migration across brain endothelium. Relevant to HIV-1 neuropathogenesis, enhanced adhesion and migration of HIV-1 infected monocytes across the BBB were significantly reduced when BMVEC were treated with PPARγ agonist. These findings indicate that Rac1 and RhoA inhibition by PPARγ agonists could be a new approach for treatment of neuroinflammation by preventing monocyte migration across the BBB.
TNF Receptor-Associated Factor 1 Expressed in Resident Lung Cells Is Required for the Development of Allergic Lung Inflammation
Authors: Oyoshi Michiko K. , Bryce Paul , Goya Sho , Pichavant Muriel , Umetsu Dale T. , Oettgen Hans C. , Tsitsikov Erdyni N.
Published: April 2014

TNF is a major therapeutic target in a range of chronic inflammatory disorders, including asthma. TNFR-associated factor (TRAF)1 is an intracellular adaptor molecule important for signaling by TNFR. In this study, we investigated the role of TRAF1 in an adoptive transfer model of allergic lung inflammation. Mice deficient in TRAF1 (TRAF1−/−) and wild-type (WT) control animals were adoptively transferred with WT OVA-immune CD4+ T cells, exposed to an aerosol of LPS-free OVA, and analyzed for the development of allergic lung inflammation. In contrast to WT mice, TRAF1−/− recipients failed to display goblet cell hyperplasia, eosinophilic inflammation, and airway hyperresponsiveness in this model of asthma. Neither T cell recruitment nor expression of the proinflammatory cytokines IL-4, IL-5, IL-13, or TNF occurred in the lungs of TRAF1−/− mice. Although purified myeloid TRAF1−/− dendritic cells (DCs) exhibited normal Ag-presenting function and transmigratory capacity in vitro and were able to induce OVA-specific immune responses in the lung draining lymph nodes (LNs) following adoptive transfer in vivo, CD11c+CD11b+ DCs from airways of TRAF1−/− recipients were not activated, and purified draining LN cells did not proliferate in vitro. Moreover, transfer of WT or TRAF1−/− DCs failed to restore T cell recruitment and DC activation in the airways of TRAF1−/− mice, suggesting that the expression of TRAF1 in resident lung cells is required for the development of asthma. Finally, we demonstrate that T cell-transfused TRAF1−/− recipient mice demonstrated impaired up-regulation of ICAM-1 expression on lung cells in response to OVA exposure.
Activated Renal Macrophages Are Markers of Disease Onset and Disease Remission in Lupus Nephritis
Authors: Schiffer Lena , Bethunaickan Ramalingam , Ramanujam Meera , Huang Weiqing , Schiffer Mario , Tao Haiou , Madaio Michael M. , Bottinger Erwin P. , Davidson Anne
Published: April 2014

Costimulatory blockade with CTLA4Ig and anti-CD40L along with a single dose of cyclophosphamide induces remission of systemic lupus erythematosus nephritis in NZB/W F1 mice. To understand the mechanisms for remission and for impending relapse, we examined the expression profiles of 61 inflammatory molecules in the perfused kidneys of treated mice and untreated mice at different stages of disease. Further studies using flow cytometry and immunohistochemistry allowed us to determine the cellular origins of several key markers. We show that only a limited set of inflammatory mediators is expressed in the kidney following glomerular immune complex deposition but before the onset of proteinuria. Formation of a lymphoid aggregate in the renal pelvis precedes the invasion of the kidney by inflammatory cells. Regulatory molecules are expressed early in the disease process and during remission but do not prevent the inevitable progression of active inflammation. Onset of proliferative glomerulonephritis and proteinuria is associated with activation of the renal endothelium, expression of chemokines that mediate glomerular cell infiltration, and infiltration by activated dendritic cells and macrophages that migrate to different topographical areas of the kidney but express a similar profile of inflammatory cytokines. Increasing interstitial infiltration by macrophages and progressive tubular damage, manifested by production of lipocalin-2, occur later in the disease process. Studies of treated mice identify a type II (M2b)-activated macrophage as a marker of remission induction and impending relapse and suggest that therapy for systemic lupus erythematosus nephritis should include strategies that prevent both activation of monocytes and their migration to the kidney.
Induction of CD56 and TCR-Independent Activation of T Cells with Aging
Authors: Lemster Bonnie H. , Michel Joshua J. , Montag David T. , Paat John J. , Studenski Stephanie A. , Newman Anne B. , Vallejo Abbe N.
Published: April 2014

Degeneration of the thymus and severe contraction of the T cell repertoire with aging suggest that immune homeostasis in old age could be mediated by distinct effectors. Therefore, receptors expressed on T cells as they undergo senescence in vitro, as well as those displayed by circulating T cells during normal chronologic aging, were examined. Monitoring of T cells driven to senescence showed de novo induction of CD56, the prototypic receptor of NK cells. Analysis of fresh T cells in peripheral blood showed an age-dependent induction of CD56. These unusual T cells expressed high levels of Bcl2, p16, and p53, and had limited, or completely lost, ability to undergo cell division, properties consistent with senescence. CD56 cross-linking without TCR ligation on CD56+ T cells resulted in extensive protein phosphorylation, NF-κB activation, and Bax down-regulation. CD56 cross-linking was also sufficient to drive production of various humoral factors. These data suggest that the immunologic environment in old age is functionally distinct, rather than being a dysfunctional version of that seen at a young age. CD56+ T cells are unique effectors capable of mediating TCR-independent immune cascades that could be harnessed to enhance protective immunity in the elderly.
Tumor Immunotherapy by Epicutaneous Immunization Requires Langerhans Cells
Authors: Stoitzner Patrizia , Green Laura K. , Jung Jae Y. , Price Kylie M. , Tripp Christoph H. , Malissen Bernard , Kissenpfennig Adrien , Hermans Ian F. , Ronchese Franca
Published: April 2014

A role for Langerhans cells (LC) in the induction of immune responses in the skin has yet to be conclusively demonstrated. We used skin immunization with OVA protein to induce immune responses against OVA-expressing melanoma cells. Mice injected with OVA-specific CD8+ T cells and immunized with OVA onto barrier-disrupted skin had increased numbers of CD8+ T cells in the blood that produced IFN-γ and killed target cells. These mice generated accelerated cytotoxic responses after secondary immunization with OVA. Prophylactic or therapeutic immunization with OVA onto barrier-disrupted skin inhibited the growth of B16.OVA tumors. LC played a critical role in the immunization process because depletion of LC at the time of skin immunization dramatically reduced the tumor-protective effect. The topically applied Ag was presented by skin-derived LC in draining lymph nodes to CD8+ T cells. Thus, targeting of tumor Ags to LC in vivo is an effective strategy for tumor immunotherapy.
Cutting Edge: CD4 T Cell-Mast Cell Interactions Alter IgE Receptor Expression and Signaling
Authors: Kashyap Mohit , Thornton Angela M. , Norton Sarah Kennedy , Barnstein Brian , Macey Matthew , Brenzovich Jennifer , Shevach Ethan , Leonard Warren J. , Ryan John J.
Published: April 2014

Mast cell activation is associated with atopic and inflammatory diseases, but the natural controls of mast cell homeostasis are poorly understood. We hypothesized that CD4+CD25+ regulatory T cells (Treg) could function in mast cell homeostasis. In this study, we demonstrate that mast cells can recruit both Treg and conventional CD4+ T cells (Tconv). Furthermore, Treg, but not Tconv, suppress mast cell FcεRI expression. Despite the known inhibitory functions of IL-10 and TGFβ1, FcεRI suppression was independent of IL-10 and TGF-β1 and required cell contact. Surprisingly, coculture with either Treg or Tconv cells suppressed IgE-mediated leukotriene C4 production but enhanced cytokine production by mast cells. This was accompanied by a selective increase in FcεRI-mediated Stat5 phosphorylation, which is a critical mediator of IgE-mediated cytokine secretion. These data are the first direct demonstration that mast cells can recruit Treg and illustrate that T cell interactions can alter the mast cell response.
Antigen Controls IL-7Rα Expression Levels on CD8 T Cells during Full Activation or Tolerance Induction
Authors: Hammerbeck Christopher D. , Mescher Matthew F.
Published: April 2014

The high-affinity chain of the IL-7 receptor, IL-7Rα (CD127), is expressed by effector CD8 T cells that have the capacity to become memory cells. IL-7Rα expression is uniformly high on naive CD8 T cells, and the majority of these cells down-regulate expression upon antigenic challenge. At the peak of expansion, the fraction of effectors expressing high IL-7Rα varies depending on the response examined. The signals that a CD8 T cell receives during a response to Ag that lead to altered expression of IL-7Rα have not been fully defined. In vitro experiments demonstrated that Ag alone is sufficient to down-regulate IL-7Rα on all cells and most of the cells rapidly re-express the receptor upon removal from Ag. Expression was not altered by the B7.1 costimulatory ligand or when IL-12 was present to provide the signal needed for development of effector functions, indicating that TCR engagement is sufficient to regulate IL-7Rα expression. Consistent with this, in vivo priming with peptide Ag resulted in IL-7Rα expression that inversely correlated with Ag levels, and expression levels were not changed when IL-12 or adjuvant were administered with Ag. A large fraction of the cells present at the peak of expansion had re-expressed IL-7Rα, but most of these cells failed to survive; those that did survive expressed high IL-7Rα levels. Thus, Ag-dependent signals regulate IL-7Rα levels on responding CD8 T cells, and this occurs whether the responding cells become fully activated or are rendered tolerant by administration of peptide Ag alone.
TLR7 Is Involved in Sequence-Specific Sensing of Single-Stranded RNAs in Human Macrophages
Authors: Gantier Michael P. , Tong Stephen , Behlke Mark A. , Xu Dakang , Phipps Simon , Foster Paul S. , Williams Bryan R. G.
Published: April 2014

Human TLR7 and 8 (hTLR7/8) have been implicated in the sequence-dependent detection of RNA oligonucleotides in immune cells. Although hTLR7 sequence-specific sensing of short RNAs has been inferred from studies of murine TLR7, this has yet to be established for hTLR7. We found that different short ssRNA sequences selectively induced either TNF-α or IFN-α in human PBMCs. The sequence-specific TNF-α response to ssRNAs observed in PBMCs could be replicated in activated human macrophage-like (THP-1) cells pretreated with IFN-γ. Surprisingly, suppression of hTLR7 expression by RNA interference in this model reduced sensing of all immunostimulatory ssRNAs tested. Modulation of the relative expression ratio of hTLR7 to hTLR8 in THP-1 cells correlated with differential sensing of immunostimulatory sequences. Furthermore, the sequence-specific IFN-α induction profile in human PBMCs was accurately modeled by a sequence-specific activation of murine TLR7 in mouse macrophages. Thus, we demonstrate for the first time that hTLR7 is involved in sequence-specific sensing of ssRNAs. We establish a novel cell model for the prediction of TNF-α induction by short RNAs in human macrophages. Our results suggest that differential sequence-specific sensing of RNA oligonucleotides between human and mouse macrophages is due to the modulation of TLR7 sensing by human TLR8.
Characterization of the In Vivo Dynamics of Medullary CD4+CD8− Thymocyte Development
Authors: Jin Rong , Wang Wei , Yao Jin-Yan , Zhou Yu-Bin , Qian Xiao-Ping , Zhang Jun , Zhang Yu , Chen Wei-Feng
Published: April 2014

Our previous studies have defined a differentiation program followed by the newly generated single-positive (SP) thymocytes before their emigration to the periphery. In the present study, we further characterize the development of CD4SP cells in the thymic medulla using mainly intrathymic adoptive transfer assays. By analyzing the differentiation kinetics of the donor cells, which were shown to home correctly to the medullary region following adoptive transfer, we established the precursor–progeny relationship among the four subsets of CD4SP thymocytes (SP1–SP4) and demonstrated that the progression from SP1 to SP4 was unidirectional and largely synchronized. Notably, while the phenotypic maturation from SP1 to SP4 was achieved in 2–3 days, a small fraction of donor cells could be retained in the thymus for a longer period, during which they further matured in function. BrdU incorporation indicated that cell expansion occurred at multiple stages except SP1. Nevertheless, CFSE labeling revealed that only a limited number of cells actually divided during their stay in the medulla. As to the thymic emigration, there was a clear bias toward cells with increasing maturity, but no distinction was found between dividing and nondividing thymocytes. Collectively, these data not only provide solid evidence for a highly ordered differentiation program for CD4SP thymocytes, but they also illustrate several important features associated with the developmental process.
ICOS, CD40, and Lymphotoxin β Receptors Signal Sequentially and Interdependently to Initiate a Germinal Center Reaction
Authors: Vu Frances , Dianzani Umberto , Ware Carl F. , Mak Tak , Gommerman Jennifer L.
Published: April 2014

Germinal center (GC) responses to T-dependent Ags require effective collaboration between Th cells, activated B cells, and follicular dendritic cells within a highly organized microenvironment. Studies using gene-targeted mice have highlighted nonredundant molecules that are key for initiating and maintaining the GC niche, including the molecules of the ICOS, CD40, and lymphotoxin (LT) pathways. Signaling through ICOS has multiple consequences, including cytokine production, expression of CD40L on Th cells, and differentiation into CXCR5+ follicular Th cells, all of which are important in the GC reaction. We have therefore taken advantage of ICOS−/− mice to dissect which downstream elements are required to initiate the formation of GC. In the context of a T-dependent immune response, we found that GC B cells from ICOS−/− mice express lower levels of LTαβ compared with wild-type GC B cells in vivo, and stimulation of ICOS on T cells induces LTαβ on B cells in vitro. Administration of agonistic anti-LTβ receptor Ab was unable to restore the GC response in ICOS−/− mice, suggesting that additional input from another pathway is required for optimal GC generation. In contrast, treatment with agonistic anti-CD40 Ab in vivo recovered GC networks and restored LTαβ expression on GC B cells in ICOS−/− mice, and this effect was dependent on LTβ receptor signaling. Collectively, these data demonstrate that ICOS activation is a prerequisite for the up-regulation of LTαβ on GC B cells in vivo and provide a model for cooperation between ICOS, CD40, and LT pathways in the context of the GC response.
Porcine Reproductive and Respiratory Syndrome Virus Subverts Repertoire Development by Proliferation of Germline-Encoded B Cells of All Isotypes Bearing Hydrophobic Heavy Chain CDR3
Authors: Butler John E. , Wertz Nancy , Weber Patrick , Lager Kelly M.
Published: April 2014

Isolator piglets infected with porcine reproductive and respiratory syndrome virus (PRRSV), which is related to the lactate dehydrogenase-elevating virus of mice, develop severe hypergammaglobulinemia, lymph node adenopathy, and autoimmune disease. Many of the polyclonally activated B cell clones bear hydrophobic H chain CDR3s (HCDR3s) and are disseminated to most lymphoid tissues. We show in this study that B cells with identical hydrophobic HCDR3s are expressed with all major isotypes in PRRSV-infected piglets (PIPs), explaining why PRRSV-induced hypergammaglobulinemia is seen in all major isotypes. Up to one-third of randomly selected VDJ clones from the respiratory tract of PIPs have hydrophobic HCDR3s exclusively bearing VDJ rearrangements with CDR1, CDR2, and nearly intact DH segments in germline configuration. These HCDR3s are long and DHA and DHB are exclusively used in reading frame 3. A minimal tripeptide motif containing three hydrophobic amino acids (Leu, Val, and Ile) or any two plus alanine is common to this hydrophobic patch. We propose that PRRSV infection causes generalized Ag-independent B cell activation and hypergammaglobulinemia with biased expansion of a subpopulation of the preimmune repertoire with hydrophobic binding sites that normally disappears during Ag-driven repertoire diversification. Elevated Ig levels in PIP cannot be explained as antiviral Abs; some Igs can account for autoantibodies to dsDNA and Golgi, whereas those with hydrophobic binding sites may account for the Ig aggregates seen in PIPs and lactate dehydrogenase-elevating virus-infected mice. This diversion from normal repertoire development may explain the delayed immune response to PRRSV.
Cholesterol-Rich Membrane Rafts and Lyn Are Involved in Phagocytosis during Pseudomonas aeruginosa Infection
Authors: Kannan Shibichakravarthy , Audet Aaron , Huang Huang , Chen Li-juan , Wu Min
Published: April 2014

The mechanism of phagocytosis of pathogens remains to be fully characterized. We report a novel phagocytosis pathway for Pseudomonas aeruginosa, which is initiated by cholesterol-rich membrane rafts and is dependent on Lyn, primarily an immune regulator with both positive and negative roles. Blocking of Lyn or blocking of cholesterol synthesis significantly inhibited phagocytosis by alveolar macrophages. We found that Lyn, via Src homology 2 and 3 domains, bound to and then activated PI3K and Akt to regulate intracellular routing of the engulfed P. aeruginosa. Further analysis indicates that Lyn and raft components entered in phagosomes and late lysosomes. Finally, respiratory burst was dependent on Lyn and membrane rafts, as confirmed by small interfering RNA and dominant-negative strategies. Our investigations demonstrate that Lyn along with membrane rafts plays a fundamental role in phagocytosis by alveolar macrophages during infection.
IL-33, a Potent Inducer of Adaptive Immunity to Intestinal Nematodes
Authors: Humphreys Neil E. , Xu Damo , Hepworth Matthew R. , Liew Foo Y. , Grencis Richard K.
Published: April 2014

IL-33 (IL-1F11) binds ST2 (IL-1R4), both of which are associated with optimal CD4+ Th2 polarization. Exogenous IL-33 drives induction of Th2-associated cytokines and associated pathological changes within the gut mucosa. Th2 polarization is also a prerequisite to expulsion of the intestinal-dwelling nematode Trichuris muris. In this study, we demonstrate that IL-33 mRNA is expressed early during parasite infection and susceptible mice can be induced to expel the parasite by a regime of exogenous IL-33 administration. IL-33 prevents an inappropriate parasite-specific Th1-polarized response and induces IL-4, IL-9, and IL-13. This redirection requires the presence of T cells and must occur at the initiation of the response to the pathogen. Interestingly, exogenous IL-33 also induced thymic stromal lymphopoietin mRNA within the infected caecum, an epithelial cell-restricted cytokine essential for the generation of Th2-driven parasite immunity. IL-33 also acts independently of T cells, altering intestinal pathology in chronically infected SCID mice, leading to an increased crypt length and intestinal epithelial cell proliferation, but reducing goblet cell hyperplasia. Thus, the ability of IL-33 to induce Th2 responses has functional relevance in the context of intestinal helminth infection, particularly during the initiation of the response.
Novel Vaccination Protocol with Two Live Mucosal Vectors Elicits Strong Cell-Mediated Immunity in the Vagina and Protects against Vaginal Virus Challenge
Authors: Li Zhongxia , Zhang Manxin , Zhou Chenghui , Zhao Xinyan , Iijima Norifumi , Frankel Fred R.
Published: April 2014

Most HIV infections result from heterosexual transmission to women. Because cellular immunity plays a key role in the control of the infection, we sought to strengthen cellular immune responses in vaginal tissue. We explored a novel prime-boost protocol that used two live mucosal agents that trigger different pathways of innate immunity and induce strong cellular immunity. Adenovirus serotype 5 (Ad5) has frequently been used as a boost for DNA vaccines. In this study we used attenuated, recombinant L. monocytogenes-gag (rLm-gag) to prime mice by various mucosal routes—oral, intrarectal, and intravaginally (ivag)—followed by a systemic or mucosal boost with replication-defective rAd5-gag. Mice primed with a single administration of rLm-gag by any route and then boosted with rAd5-gag intramuscularly exhibited abundant Gag-specific CD8 T cells in spleen and vaginal lamina propria. Conversely, when boosted with rAd5-gag ivag, the immune response was reoriented toward the vagina with strikingly higher CD8 T cell responses in that tissue, particularly after ivag immunization by both vectors (ivag/ivag). Five weeks to 5 mo later, ivag/ivag-immunized mice continued to show high levels of effector memory CD8 T cells in vagina, while the pool of memory T cells in spleen assumed a progressively more central memory T cell phenotype. The memory mice showed high in vivo CTL activity in vagina, a strong recall response, and robust protection after ivag vaccinia-gag challenge, suggesting that this prime-boost strategy can induce strong cellular immunity, especially in vaginal tissues, and might be able to block the heterosexual transmission of HIV-1 at the vaginal mucosa.
A CD8+/CD103high T Cell Subset Regulates TNF-Mediated Chronic Murine Ileitis
Authors: Ho Johnson , Kurtz Courtney C. , Naganuma Makoto , Ernst Peter B. , Cominelli Fabio , Rivera-Nieves Jesús
Published: April 2014

Recruitment of lymphocytes to sites of inflammation requires the sequential engagement of adhesion molecules and chemokine receptors. Of these, the lectin-like molecule CD44 has been particularly implicated in inflammatory trafficking. Using a TNF-driven model of chronic ileitis (i.e., B6.129P-TnfΔARE mice) that recapitulates many features of Crohn’s disease, we demonstrate dynamic changes in the expression and functional state of CD44 on CD8+ T cells. These cells coexpress CD44 and L-selectin, giving them a surface phenotype similar to that of central memory T cells. Yet functionally they exhibit the phenotype of effector T cells, because they produce IFN-γ. Unexpectedly, depletion of the CD8+ population had no effect on the severity of ileitis. Further analyses showed a second CD8+ population that lacked CD44, but expressed CD103, produced TGF-β, inhibited the proliferation of CD4+ in vitro, and attenuated adoptively transferred ileitis in vivo, most likely counteracting the proinflammatory role of the CD44high subset. Collectively, these data suggest that the presence or absence of CD44 and CD103 on the CD8+ lymphocyte surface defines functionally distinct subsets of CD8+ T cells in vivo. These inflammation-driven populations exert distinct roles during the development of chronic ileitis, and influence the balance of effector and regulatory functions in the chronically inflamed small intestine.
Intestinal Inflammation Increases the Expression of the P2Y6 Receptor on Epithelial Cells and the Release of CXC Chemokine Ligand 8 by UDP
Authors: Grbic Djordje M. , Degagné Émilie , Langlois Christine , Dupuis Andrée-Anne , Gendron Fernand-Pierre
Published: April 2014

Epithelial cells participate in the immune response of the intestinal mucosa. Extracellular nucleotides have been recognized as inflammatory molecules. We investigated the role of extracellular nucleotides and their associated P2Y receptors in the secretion of cytokines by epithelial cells. The effect of intestinal inflammation on P2Y6 receptor expression was determined by PCR in the mouse, rat, and human. Localization of the P2Y6 receptor was determined by immunofluorescence microscopy in the colon of normal and dextran sulfate sodium-treated mice. The effect of P2Y6 activation by UDP on cytokine expression and release by epithelial cells was determined using a combination of Western blots, luciferase assays, RT-PCR, cytokine Ab arrays, and ELISA. Inflammation up-regulates P2Y2 as well as P2Y6 receptor expression in the mucosa of the colon of colitic mice. In vitro, we demonstrated that UDP could be released by Caco-2/15 cells. We have confirmed the increased expression of P2Y6 by challenging intestinal epithelial cell-6 and Caco-2/15 cells with TNF-α and IFN-γ and showing that stimulation of epithelial cells by UDP results in an increased expression and release of CXCL8 by an ERK1/2-dependent mechanism. The increase in CXCL8 expression was associated with a transcriptional activation by the P2Y6 receptor. This study is the first report demonstrating the implication of P2Y receptors in the inflammatory response of intestinal epithelial cells. We show for the first time that P2Y6, as well as P2Y2, expression is increased by the stress associated with intestinal inflammation. These results demonstrate the emergence of extracellular nucleotide signaling in the orchestration of intestinal inflammation.
β-Glucan Activates Microglia without Inducing Cytokine Production in Dectin-1-Dependent Manner
Authors: Shah Vaibhav B. , Huang Yongcheng , Keshwara Rohan , Ozment-Skelton Tammy , Williams David L. , Keshvara Lakhu
Published: April 2014

Microglia are the resident mononuclear phagocytic cells that are critical for innate and adaptive responses within the CNS. Like other immune cells, microglia recognize and are activated by various pathogen-associated molecular patterns. β-glucans are pathogen-associated molecular patterns present within fungal cell walls that are known to trigger protective responses in a number of immune cells. In an effort to better understand microglial responses to β-glucans and the underlying response pathways, we sought to determine whether Dectin-1, a major β-glucan receptor recently identified in leukocytes, plays a similar role in β-glucan-induced activation in microglia. In this study, we report that Dectin-1 is indeed expressed on the surface of murine primary microglia, and engagement of the receptor with particulate β-glucan resulted in an increase in tyrosine phosphorylation of spleen tyrosine kinase, a hallmark feature of the Dectin-1 signaling pathway. Moreover, phagocytosis of β-glucan particles and subsequent intracellular production of reactive oxygen species were also mediated by Dectin-1. However, unlike in macrophages and dendritic cells, β-glucan-mediated microglial activation did not result in significant production of cytokines or chemokines; thus, the interaction of microglial Dectin-1 with glucan elicits a unique response. Our results suggest that the Dectin-1 pathway may play an important role in antifungal immunity in the CNS.
RhoA Is Involved in LFA-1 Extension Triggered by CXCL12 but Not in a Novel Outside-In LFA-1 Activation Facilitated by CXCL9
Authors: Pasvolsky Ronit , Grabovsky Valentin , Giagulli Cinzia , Shulman Ziv , Shamri Revital , Feigelson Sara W. , Laudanna Carlo , Alon Ronen
Published: April 2014

Chemokines presented on endothelial tissues instantaneously trigger LFA-1-mediated arrest on ICAM-1 via rapid inside-out and outside-in (ligand-driven) LFA-1 activation. The GTPase RhoA was previously implicated in CCL21-triggered LFA-1 affinity triggering in murine T lymphocytes and in LFA-1-dependent adhesion strengthening to ICAM-1 on Peyer’s patch high endothelial venules stabilized over periods of at least 10 s. In this study, we show that a specific RhoA 23/40 effector region is vital for the initial LFA-1-dependent adhesions of lymphocytes on high endothelial venules lasting 1–3 s. Blocking the RhoA 23/40 region in human T lymphocytes in vitro also impaired the subsecond CXCL12-triggered LFA-1-mediated T cell arrest on ICAM-1 by eliminating the rapid induction of an extended LFA-1 conformational state. However, the inflammatory chemokine CXCL9 triggered robust LFA-1-mediated T lymphocyte adhesion to ICAM-1 at subsecond contacts independently of the RhoA 23/40 region. CXCL9 did not induce conformational changes in the LFA-1 ectodomain, suggesting that particular chemokines can activate LFA-1 through outside-in post ligand binding stabilization changes. Like CXCL9, the potent diacylglycerol-dependent protein kinase C agonist PMA was found to trigger LFA-1 adhesiveness to ICAM-1 also without inducing integrin extension or an a priori clustering and independently of the RhoA 23/40 region. Our results collectively suggest that the 23/40 region of RhoA regulates chemokine-induced inside-out LFA-1 extension before ligand binding, but is not required for a variety of chemokine and non-chemokine signals that rapidly strengthen LFA-1-ICAM-1 bonds without an a priori induction of high-affinity extended LFA-1 conformations.
STAT3 Is Indispensable to IL-27-Mediated Cell Proliferation but Not to IL-27-Induced Th1 Differentiation and Suppression of Proinflammatory Cytokine Production
Authors: Owaki Toshiyuki , Asakawa Masayuki , Morishima Noriko , Mizoguchi Izuru , Fukai Fumio , Takeda Kiyoshi , Mizuguchi Junichiro , Yoshimoto Takayuki
Published: April 2014

IL-27, a member of the IL-6/IL-12 family, activates both STAT1 and STAT3 through its receptor, which consists of WSX-1 and gp130 subunits, resulting in augmentation of Th1 differentiation and suppression of proinflammatory cytokine production. In the present study, we investigated the role of STAT3 in the IL-27-mediated immune functions. IL-27 induced phosphorylation of STAT1, -2, -3 and -5 in wild-type naive CD4+ T cells, but failed to induce that of STAT3 and STAT5 in STAT3-deficient cohorts. IL-27 induced not only proinflammatory responses including up-regulation of ICAM-1, T-box expressed in T cells, and IL-12Rβ2 and Th1 differentiation, but also anti-inflammatory responses including suppression of proinflammatory cytokine production such as IL-2, IL-4, and IL-13 even in STAT3-deficient naive CD4+ T cells. In contrast, IL-27 augmented c-Myc and Pim-1 expression and induced cell proliferation in wild-type naive CD4+ T cells but not in STAT3-deficient cohorts. Moreover, IL-27 failed to activate STAT3, augment c-Myc and Pim-1 expression, and induce cell proliferation in pro-B BaF/3 transfectants expressing mutant gp130, in which the putative STAT3-binding four Tyr residues in the YXXQ motif of the cytoplasmic region was replaced by Phe. These results suggest that STAT3 is activated through gp130 by IL-27 and is indispensable to IL-27-mediated cell proliferation but not to IL-27-induced Th1 differentiation and suppression of proinflammatory cytokine production. Thus, IL-27 may be a cytokine, which activates both STAT1 and STAT3 through distinct receptor subunits, WSX-1 and gp130, respectively, to mediate its individual immune functions.