bluuebunny/crossref_metadata_2025 huggingface dataset:
Cutting Edge: Egress of Newly Generated Plasma Cells from Peripheral Lymph Nodes Depends on β2 Integrin
Authors: Pabst Oliver , Peters Thorsten , Czeloth Niklas , Bernhardt Günter , Scharffetter-Kochanek Karin , Förster Reinhold
Published: April 2014

During humoral immune responses, naive B cells differentiate into Ab-secreting plasma cells within secondary lymphoid organs. Differentiating plasma cells egress from their sites of generation and redistribute to other tissues, predominantly the bone marrow and mucosal tissues. In this study, we demonstrate that within peripheral lymph nodes newly generated plasma cells localize to medullary cords which express the β2 integrin ligand ICAM-1. In β2 integrin-deficient mice plasma cells accumulate inside the lymph nodes, resulting in severely reduced plasma cell numbers in the bone marrow. Since plasma cells isolated from β2 integrin-deficient animals migrate efficiently into the bone marrow when transferred i.v., our findings provide profound evidence that β2 integrins are required for the egress of plasma cells from peripheral lymph nodes.
A New Dynamic Model of CD8+ T Effector Cell Responses via CD4+ T Helper-Antigen-Presenting Cells
Authors: Xiang Jim , Huang Hui , Liu Yongqing
Published: April 2014

A long-standing paradox in cellular immunology has been the conditional requirement for CD4+ Th cells in priming of CD8+ CTL responses. We propose a new dynamic model of CD4+ Th cells in priming of Th-dependent CD8+ CTL responses. We demonstrate that OT II CD4+ T cells activated by OVA-pulsed dendritic cells (DCOVA) are Th1 phenotype. They acquire the immune synapse-composed MHC II/OVAII peptide complexes and costimulatory molecules (CD54 and CD80) as well as the bystander MHC class I/OVAI peptide complexes from the DCOVA by DCOVA stimulation and thus also the potential to act themselves as APCs. These CD4+ Th-APCs stimulate naive OT I CD8+ T cell proliferation through signal 1 (MHC I/OVAI/TCR) and signal 2 (e.g., CD54/LFA-1 and CD80/CD28) interactions and IL-2 help. In vivo, they stimulate CD8+ T cell proliferation and differentiation into CTLs and induce effective OVA-specific antitumor immunity. Taken together, this study demonstrates that CD4+ Th cells carrying acquired DC Ag-presenting machinery can, by themselves, efficiently stimulate CTL responses. These results have substantial implications for research in antitumor and other aspects of immunity.
Release of High Mobility Group Box 1 by Dendritic Cells Controls T Cell Activation via the Receptor for Advanced Glycation End Products
Authors: Dumitriu Ingrid E. , Baruah Paramita , Valentinis Barbara , Voll Reinhard E. , Herrmann Martin , Nawroth Peter P. , Arnold Bernd , Bianchi Marco E. , Manfredi Angelo A. , Rovere-Querini Patrizia
Published: April 2014

High mobility group box 1 (HMGB1) is an abundant and conserved nuclear protein that is released by necrotic cells and acts in the extracellular environment as a primary proinflammatory signal. In this study we show that human dendritic cells, which are specialized in Ag presentation to T cells, actively release their own HMGB1 into the extracellular milieu upon activation. This secreted HMGB1 is necessary for the up-regulation of CD80, CD83, and CD86 surface markers of human dendritic cells and for IL-12 production. The HMGB1 secreted by dendritic cells is also required for the clonal expansion, survival, and functional polarization of naive T cells. Using neutralizing Abs and receptor for advanced glycation end product-deficient (RAGE−/−) cells, we demonstrate that RAGE is required for the effect of HMGB1 on dendritic cells. HMGB1/RAGE interaction results in downstream activation of MAPKs and NF-κB. The use of an ancient signal of necrosis, HMGB1, by dendritic cells to sustain their own maturation and for activation of T lymphocytes represents a profitable evolutionary mechanism.
Local Radiation Therapy of B16 Melanoma Tumors Increases the Generation of Tumor Antigen-Specific Effector Cells That Traffic to the Tumor
Authors: Lugade Amit A. , Moran James P. , Gerber Scott A. , Rose Robert C. , Frelinger John G. , Lord Edith M.
Published: April 2014

Immunotherapy of cancer is attractive because of its potential for specificity and limited side effects. The efficacy of this approach may be improved by providing adjuvant signals and an inflammatory environment for immune cell activation. We evaluated antitumor immune responses in mice after treatment of OVA-expressing B16-F0 tumors with single (15 Gy) or fractionated (5 × 3 Gy) doses of localized ionizing radiation. Irradiated mice had cells with greater capability to present tumor Ags and specific T cells that secreted IFN-γ upon peptide stimulation within tumor-draining lymph nodes than nonirradiated mice. Immune activation in tumor-draining lymph nodes correlated with an increase in the number of CD45+ cells infiltrating single dose irradiated tumors compared with nonirradiated mice. Similarly, irradiated mice had increased numbers of tumor-infiltrating lymphocytes that secreted IFN-γ and lysed tumor cell targets. Peptide-specific IFN-γ responses were directed against both the class I and class II MHC-restricted OVA peptides OVA257–264 and OVA323–339, respectively, as well as the endogenous class I MHC-restricted B16 tumor peptide tyrosinase-related protein 2180–188. Adoptive transfer studies indicated that the increased numbers of tumor Ag-specific immune cells within irradiated tumors were most likely due to enhanced trafficking of these cells to the tumor site. Together these results suggest that localized radiation can increase both the generation of antitumor immune effector cells and their trafficking to the tumor site.
HIV-1 Viral Escape in Infancy Followed by Emergence of a Variant-Specific CTL Response
Authors: Feeney Margaret E. , Tang Yanhua , Pfafferott Katja , Roosevelt Kathleen A. , Draenert Rika , Trocha Alicja , Yu Xu G. , Verrill Cori , Allen Todd , Moore Corey , Mallal Simon , Burchett Sandra , McIntosh Kenneth , Pelton Stephen I. , St. John M. Anne , Hazra Rohan , Klenerman Paul , Altfeld Marcus , Walker Bruce D. , Goulder Philip J. R.
Published: April 2014

Mutational escape from the CTL response represents a major driving force for viral diversification in HIV-1-infected adults, but escape during infancy has not been described previously. We studied the immune response of perinatally infected children to an epitope (B57-TW10) that is targeted early during acute HIV-1 infection in adults expressing HLA-B57 and rapidly mutates under this selection pressure. Viral sequencing revealed the universal presence of escape mutations within TW10 among B57- and B5801-positive children. Mutations in TW10 and other B57-restricted epitopes arose early following perinatal infection of B57-positive children born to B57-negative mothers. Surprisingly, the majority of B57/5801-positive children exhibited a robust response to the TW10 escape variant while recognizing the wild-type epitope weakly or not at all. These data demonstrate that children, even during the first years of life, are able to mount functional immune responses of sufficient potency to drive immune escape. Moreover, our data suggest that the consequences of immune escape may differ during infancy because most children mount a strong variant-specific immune response following escape, which is rarely seen in adults. Taken together, these findings indicate that the developing immune system of children may exhibit greater plasticity in responding to a continually evolving chronic viral infection.
Macrophage Colony-Stimulating Factor Induces Vascular Endothelial Growth Factor Production in Skeletal Muscle and Promotes Tumor Angiogenesis
Authors: Okazaki Tatsuma , Ebihara Satoru , Takahashi Hidenori , Asada Masanori , Kanda Akio , Sasaki Hidetada
Published: April 2014

Although M-CSF has been used for myelosuppression due to chemotherapy in patients with solid tumors, the effect of exogenous M-CSF on tumor angiogenesis has not been studied. In this study we showed that M-CSF has the ability to accelerate solid tumor growth by enhancing angiogenesis with a novel mechanism. M-CSF accelerated intratumoral vessel density in tumors inoculated into mice, although it did not accelerate the proliferation of malignant cells and cultured endothelial cells in vitro. In both the absence and the presence of tumors, M-CSF significantly increased the circulating cells that displayed phenotypic characteristics of endothelial progenitor cells in mice. Moreover, M-CSF treatment induced the systemic elevation of vascular endothelial growth factor (VEGF). VEGFR-2 kinase inhibitor significantly impaired the effect of M-CSF on tumor growth. In vivo, M-CSF increased VEGF mRNA expression in skeletal muscles. Even after treatment with carageenan and anti-CD11b mAb in mice, M-CSF increased VEGF production in skeletal muscles, suggesting that systemic VEGF elevation was attributed to skeletal muscle VEGF production. In vitro, M-CSF increased VEGF production and activated the Akt signaling pathway in C2C12 myotubes. These results suggest that M-CSF promotes tumor growth by increasing endothelial progenitor cells and activating angiogenesis, and the effects of M-CSF are largely based on the induction of systemic VEGF from skeletal muscles.
Activation of CD8+ Regulatory T Cells by Human Placental Trophoblasts
Authors: Shao Ling , Jacobs Adam R. , Johnson Valrie V. , Mayer Lloyd
Published: April 2014

The immunological basis by which a mother tolerates her semi-allogeneic fetus remains poorly understood. Several mechanisms are likely to contribute to this phenomenon including active immune regulation by regulatory T cells. In this article, we report that human placental trophoblasts activate a clonal population of CD8+ T cells with regulatory function. These cells are not MHC class I restricted, but require costimulation through a member of the carcinoembryonic Ag family present on early gestation trophoblasts. These regulatory T cells express the mucosal markers CD101 and CD103 and display selective usage of the TCR gene Vβ9. CD8+ T cells isolated from the peripheral blood of pregnant mothers (16–28 wk) also demonstrate expansions in the same Vβ family (Vβ9), signaling a possible role for these cells in preventing fetal rejection in vivo. We have previously characterized a subset of CD8+ regulatory T cells activated by the combination of the nonclassical class I molecule CD1d and a costimulatory molecule of the carcinoembryonic Ag family present on the intestinal epithelium. These data support the concept that distinct regulatory T cell populations exist at different sites and may be regulated locally by unique restriction elements, costimulatory signals, and Ags.
A Defective Viral Superantigen-Presenting Phenotype in HLA-DR Transfectants Is Corrected by CIITA
Authors: Azar Georges A. , Sékaly Rafick-Pierre , Thibodeau Jacques
Published: April 2014

Activation of T lymphocytes by mouse mammary tumor virus superantigen (vSAg) requires binding to MHC class II molecules. The subcellular location where functional interactions occur between MHC class II molecules and vSAgs is still a matter of debate. To gain further insight into this issue, we have used human epithelial HeLa cells expressing HLA-DR1. Surprisingly, the human cells were unable to present transfected vSAg7 or vSAg9 to a series of murine T cell hybridomas. The defect is not related to a lack of vSAg processing, because these cells can indirectly activate T cells after coculture in the presence of B lymphocytes. However, after IFN-γ treatment, the HeLa DR1+ cells became apt at directly presenting the vSAg. Furthermore, transfection of CIITA was sufficient to restore presentation. Reconstitution experiments demonstrated the necessity of coexpressing HLA-DM and invariant chain (Ii) for efficient vSAg presentation. Interestingly, inclusion of a dileucine motif in the DRβ cytoplasmic tail bypassed the need for HLA-DM expression and allowed the efficient presentation of vSAg7 in the presence of Ii. A similar trafficking signal was included in vSAg7 by replacing its cytoplasmic tail with the one of Ii. However, sorting of this chimeric Ii/vSAg molecule to the endocytic pathway completely abolished both its indirect and direct presentation. Together, our results suggest that functional vSAgs-DR complexes form after the very late stages of class II maturation, most probably at the cell surface.
TLR2 Agonist Ameliorates Established Allergic Airway Inflammation by Promoting Th1 Response and Not via Regulatory T Cells
Authors: Patel Manish , Xu Damo , Kewin Pete , Choo-Kang Brian , McSharry Charles , Thomson Neil C. , Liew Foo Y.
Published: April 2014

TLRs are primary sensors of both innate and adaptive immune systems, where they play a pivotal role in the response directed against structurally conserved components of pathogens. Synthetic bacterial lipopeptide Pam3CSK4 is a TLR2 agonist capable of modulating Th1 and Th2 responses. This study examines the therapeutic effect of Pam3CSK4 in established airway inflammation in a murine model of asthma. In mice previously sensitized and challenged with OVA, Pam3CSK4 given i.p. markedly reduced the total inflammatory cell infiltrate and eosinophilia in bronchoalveolar lavage fluid. Pam3CSK4 therapy was associated with a reduction in OVA-induced IL-4 and IL-5 secretion from thoracic lymph node culture, airways inflammation, bronchial hyperresponsiveness, and serum levels of IgE. Pam3CSK4 therapy was also associated with an increase in OVA-induced IFN-γ, IL-12, and IL-10 production. However, the anti-inflammatory effect of Pam3CSK4 was independent of IL-10 or TGF-β, but was critically dependent on IL-12, the production of which by dendritic cells was enhanced by Pam3CSK4 in vitro. Our results provide direct evidence that Pam3CSK4 could represent a novel therapeutic agent in allergic airways disease.
A Class I Transgene Reveals Regulatory Events on Chromosome 1 Marking Peripheral T Cell Differentiation and Memory
Authors: Sloma Cari Roark , Hansen Michael J. , MacDougall Audrey A. , Van Keulen Virginia P. , Jenkins Robert B. , Pease Larry R.
Published: April 2014

T cells respond to external signals by altering patterns of gene expression. Our characterization of a transgenic mouse revealed a genetic locus that is specifically regulated in T cells. Elucidation of the factors controlling the expression of the marker transgene may reveal basic regulatory mechanisms used by T cells as they differentiate from naive to primed/memory T cells. Although endogenous MHC class I Kq expression is normal in these animals, expression of the Kb transgene differentiates naive from primed/memory T cells. KbHigh T cells bear the phenotypic and functional properties of primed/memory T cells, while KbLow T cells have naive phenotypes. The transition from KbLow to KbHigh appears to involve signals resulting from engagement of the TCR. We show that transgene integration has occurred on chromosome 1, between D1Mit365 and D1Mit191. The gene regulatory mechanisms directing expression of the locus marked by the transgene are distinct from those controlling other known T cell-related genes within this locus. Stimulation of KbHigh T cells results in the up-regulation of both the endogenous Kq gene and the Kb transgene. However, the same stimuli induce increased expression of only Kq on KbLow T cells. This indicates that even though the transcription factors necessary for class I expression are present in KbLow T cells, the Kb gene appears not to be accessible to these factors. These findings suggest a change in chromatin structure at the transgene integration site as cells progress from a naive to a primed/memory differentiation state.
CD27/CFSE-Based Ex Vivo Selection of Highly Suppressive Alloantigen-Specific Human Regulatory T Cells
Authors: Koenen Hans J. P. M. , Fasse Esther , Joosten Irma
Published: April 2014

Naturally occurring CD4+CD25+ regulatory T cells (Treg) are crucial in immunoregulation and have great therapeutic potential for immunotherapy in the prevention of transplant rejection, allergy, and autoimmune diseases. The efficacy of Treg-based immunotherapy critically depends on the Ag specificity of the regulatory T cells. Moreover, the use of Ag-specific Treg as opposed to polyclonal expanded Treg will reduce the total number of Treg necessary for therapy. Hence, it is crucial to develop ex vivo selection procedures that allow selection and expansion of highly potent, Ag-specific Treg. In this study we describe an ex vivo CFSE cell sorter-based isolation method for human alloantigen-specific Treg. To this end, freshly isolated CD4+CD25+ Treg were labeled with CFSE and stimulated with (target) alloantigen and IL-2 plus IL-15 in short-term cultures. The alloantigen-reactive dividing Treg were characterized by low CFSE content and could be subdivided by virtue of CD27 expression. CD27/CFSE cell sorter-based selection of CD27+ and CD27− cells resulted in two highly suppressive Ag-specific Treg subsets. Each subset suppressed naive and Ag-experienced memory T cells, and importantly, CD27+ Treg also suppressed ongoing T cell responses. Summarizing, the described procedure enables induction, expansion, and especially selection of highly suppressive, Ag-specific Treg subsets, which are crucial in Ag-specific, Treg-based immunotherapy.
Tetrahydro-4-Aminobiopterin Attenuates Dendritic Cell-Induced T Cell Priming Independently from Inducible Nitric Oxide Synthase
Authors: Thoeni Guntram , Stoitzner Patrizia , Brandacher Gerald , Romani Nikolaus , Heufler Christine , Werner-Felmayer Gabriele , Werner Ernst R.
Published: April 2014

Formation of NO by NO synthases (NOSs) strictly depends on tetrahydrobiopterin. Its structural analog, tetrahydro-4-aminobiopterin, is an inhibitor of all NOS isoenzymes, which prolongs allograft survival in acute murine cardiac rejection and prevents septic shock in the rat. In this study, we show that murine bone marrow-derived dendritic cells treated with tetrahydro-4-aminobiopterin had a reduced capacity to prime alloreactive murine T cells in oxidative mitogenesis. Checking for a possible influence on LPS-induced dendritic cell maturation, we found that tetrahydro-4-aminobiopterin down-regulated MHC class II expression and counteracted LPS-induced down-regulation of ICOS ligand, while expression of CD40, CD86, CD80, B7-H1, and B7-DC remained unchanged. Tetrahydro-4-aminobiopterin also reduced activation of CD4+ T cells isolated from mice overexpressing an OVA-specific TCR by OVA-loaded murine bone marrow-derived dendritic cells, thus indicating that its effect on MHC class II expression is involved in attenuating T cell activation. In line with affecting dendritic cell function and T cell activation, tetrahydro-4-aminobiopterin impaired production of proinflammatory cytokines and the Th1 response. With regard to cell survival, tetrahydro-4-aminobiopterin induced efficient apoptosis of murine T cells but not of murine dendritic cells. Experiments with cells from inducible NOS (iNOS) knockout mice and with N6-(1-iminoethyl)-l-lysine, a specific inhibitor of iNOS, ruled out participation of iNOS in any of the observed effects. These findings characterize attenuation of T cell stimulatory capacity of murine bone marrow-derived dendritic cells as an immunosuppressive mechanism of tetrahydro-4-aminobiopterin that is not related to its iNOS-inhibiting properties.
TCR Engagement Increases Hypoxia-Inducible Factor-1α Protein Synthesis via Rapamycin-Sensitive Pathway under Hypoxic Conditions in Human Peripheral T Cells
Authors: Nakamura Hiroshi , Makino Yuichi , Okamoto Kensaku , Poellinger Lorenz , Ohnuma Kei , Morimoto Chikao , Tanaka Hirotoshi
Published: April 2014

Peripheral T cells encounter rapid decrease in oxygen tension because they are activated by Ag recognition and migrate into inflammatory sites or tumors. Activated T cells, therefore, are thought to have such machineries that enable them to adapt to hypoxic conditions and execute immune regulation in situ. We have recently shown that survival of CD3-engaged human peripheral blood T cells is prolonged under hypoxic conditions and hypoxia-inducible factor-1 (HIF-1) and its target gene product adrenomedullin play a critical role for the process. It is also shown that hypoxia alone is not sufficient, but TCR-mediated signal is required for accumulation of HIF-1α in human peripheral T cells. In the present study, we showed that TCR engagement does not influence hypoxia-dependent stabilization but stimulates protein synthesis of HIF-1α, most possibly via PI3K/mammalian target of rapamycin system, and that expression of HIF-1α and its target genes is blocked by treatment with rapamycin. Since some of those gene products, e.g., glucose transporters and phosphoglycerokinase, are considered to be essential for glycolysis and energy production under hypoxic conditions and adequate immune reaction in T cells, this TCR-mediated synthesis of HIF-1α may play a pivotal role in peripheral immune response. Taken together, our results may highlight a novel aspect of downstream signal from Ag recognition by TCR and a unique pharmacological role of rapamycin as well.
The Role of Host CD4 T Cells in the Pathogenesis of the Chronic Graft-versus-Host Model of Systemic Lupus Erythematosus
Authors: Choudhury Arpita , Maldonado Michael A. , Cohen Philip L. , Eisenberg Robert A.
Published: April 2014

Systemic lupus erythematosus is characterized by production of autoantibodies and glomerulonephritis. The murine chronic graft-vs-host (cGVH) model of systemic lupus erythematosus is induced by allorecognition of foreign MHC class II determinants. Previous studies have shown that cGVH could not be induced in CD4 knockout (CD4KO) mice. We have further explored the role of host CD4 T cells in this model. Our studies now show that B cells in CD4KO mice have intrinsic defects that prevent them from responding to allohelp. In addition, B cells in CD4KO mice showed phenotypic differences compared with congeneic C57BL/6 B cells, indicating some degree of in vivo activation and increased numbers of cells bearing a marginal zone B cell phenotype. The transfer of syngeneic CD4 T cells at the time of initiation of cGVH did not correct these B cell abnormalities; however, if CD4 T cells were transferred during the development and maturation of B cells, then the B cells from CD4KO mice acquire the ability to respond in cGVH. These studies clearly indicate that B cells need to coexist with CD4 T cells early in their development to develop full susceptibility to alloactivation signals.
Recombinant p21 Protein Inhibits Lymphocyte Proliferation and Transcription Factors
Authors: Khanna Ashwani K. , Plummer Matthew , Nilakantan Vani , Pieper Galen M.
Published: April 2014

Cellular proliferation determines the events leading to the initiation and development of inflammation, immune activation, cancer, atherogenesis, and other disorders associated with aberrant cell proliferation. Cyclin inhibitor p21 plays a unique role in limiting cell cycle progression. However, its effectiveness can only be demonstrated with direct in vitro and in vivo delivery to control aberrant proliferation. We demonstrate that using a protein-transducing domain p21 protein a) localizes within the nuclear compartments of cells, b) interacts with transcription factors, NF-κB, and NFATs (NFATc and NFATp), and c) inhibits lymphocyte proliferation and expression of proinflammatory cytokines. This study using lymphocyte proliferation as a model suggests that the recombinant p21 protein can directly be delivered as a therapeutic protein to provide a novel, viable, and powerful strategy to limit proliferation, inflammation, alloimmune activation, cancer, and vascular proliferative disorders such as atherosclerosis.
Circadian Oscillations of Clock Genes, Cytolytic Factors, and Cytokines in Rat NK Cells
Authors: Arjona Alvaro , Sarkar Dipak K.
Published: April 2014

A growing body of knowledge is revealing the critical role of circadian physiology in the development of specific pathological entities such as cancer. NK cell function participates in the immune response against infection and malignancy. We have reported previously the existence of a physiological circadian rhythm of NK cell cytolytic activity in rats, suggesting the existence of circadian mechanisms subjacent to NK cell function. At the cellular level, circadian rhythms are originated by the sustained transcriptional-translational oscillation of clock genes that form the cellular clock apparatus. Our aim in this study was to investigate the presence of molecular clock mechanisms in NK cells as well as the circadian expression of critical factors involved in NK cell function. For that purpose, we measured the circadian changes in the expression of clock genes (Per1, Per2, Bmal1, Clock), Dbp (a clock-controlled output gene), CREB (involved in clock signaling), cytolytic factors (granzyme B and perforin), and cytokines (IFN-γ and TNF-α) in NK cells enriched from the rat spleen. The results obtained from this study demonstrate for the first time the existence of functional molecular clock mechanisms in NK cells. Moreover, the circadian expression of cytolytic factors and cytokines in NK cells reported in this study emphasizes the circadian nature of NK cell function.
Peptide-Specific CD8 T Regulatory Cells Use IFN-γ to Elaborate TGF-β-Based Suppression
Authors: Myers Lara , Croft Michael , Kwon Byoung S. , Mittler Robert S. , Vella Anthony T.
Published: April 2014

We identified a murine peptide-specific CD8 T regulatory cell population able to suppress responding CD4 T cells. Immunization with OVA, poly(I:C), and anti-4-1BB generated a population of SIINFEKL-specific CD8 T regulatory cells that profoundly inhibited peptide-responding CD4 T cells from cellular division. The mechanism of suppression required IFN-γ, but IFN-γ alone was not sufficient to suppress the responding CD4 T cells. The data show that CD8 T regulatory cells were unable to suppress unless they engaged IFN-γ. Furthermore, even in the absence of recall with peptide, the CD8 T regulatory cells suppressed CD4 responses as long as IFN-γ was present. To examine the effector mechanism of suppression, we showed that neutralizing TGF-β inhibited suppression because inclusion of anti-TGF-β rescued the proliferative capacity of the responding cells. TGF-β-based suppression was dependent completely upon the CD8 T regulatory cells being capable of binding IFN-γ. This was the case, although peptide recall of primed IFN-γ −/− or IFN-γR−/− CD8 T cells up-regulated pro-TGF-β protein as measured by surface latency-associated peptide expression but yet were unable to suppress. Finally, we asked whether the CD8 T regulatory cells were exposed to active TGF-β in vivo and showed that only wild-type CD8 T regulatory cells expressed the TGF-β-dependent biomarker CD103, suggesting that latency-associated peptide expression is not always congruent with elaboration of active TGF-β. These data define a novel mechanism whereby IFN-γ directly stimulates CD8 T regulatory cells to elaborate TGF-β-based suppression. Ultimately, this mechanism may permit regulation of pathogenic Th1 responses by CD8 T regulatory cells.
Inhibition of NF-κB and Oxidative Pathways in Human Dendritic Cells by Antioxidative Vitamins Generates Regulatory T Cells
Authors: Tan Peng H. , Sagoo Pervinder , Chan Cliburn , Yates John B. , Campbell Jamie , Beutelspacher Sven C. , Foxwell Brian M. J. , Lombardi Giovanna , George Andrew J. T.
Published: April 2014

Dendritic cells (DCs) are central to T cell immunity, and many strategies have been used to manipulate DCs to modify immune responses. We investigated the effects of antioxidants ascorbate (vitamin C) and α-tocopherol (vitamin E) on DC phenotype and function. Vitamins C and E are both antioxidants, and concurrent use results in a nonadditive activity. We have demonstrated that DC treated with these antioxidants are resistant to phenotypic and functional changes following stimulation with proinflammatory cytokines. Following treatment, the levels of intracellular oxygen radical species were reduced, and the protein kinase RNA-regulated, eukaryotic translation initiation factor 2α, NF-κB, protein kinase C, and p38 MAPK pathways could not be activated following inflammatory agent stimulation. We went on to show that allogeneic T cells (including CD4+CD45RO, CD4+CD45RA, and CD4+CD25− subsets) were anergized following exposure to vitamin-treated DCs, and secreted higher levels of Th2 cytokines and IL-10 than cells incubated with control DCs. These anergic T cells act as regulatory T cells in a contact-dependent manner that is not dependent on IL-4, IL-5, IL-10, IL-13, and TGF-β. These data indicate that vitamin C- and E-treated DC might be useful for the induction of tolerance to allo- or autoantigens.
IL-4 Modulation of CD4+CD25+ T Regulatory Cell-Mediated Suppression
Authors: Pace Luigia , Pioli Claudio , Doria Gino
Published: April 2014

Murine CD4+CD25+ T regulatory (Treg) cells were cocultured with CD4+CD25− Th cells and APCs or purified B cells and stimulated by anti-CD3 mAb. Replacement of APCs by B cells did not significantly affect the suppression of CD4+CD25− Th cells. When IL-4 was added to separate cell populations, this cytokine promoted CD4+CD25− Th and CD4+CD25+ Treg cell proliferation, whereas the suppressive competence of CD4+CD25+ Treg cells was preserved. Conversely, IL-4 added to coculture of APCs, CD4+CD25− Th cells, and CD4+CD25+ Treg cells inhibited the suppression of CD4+CD25− Th cells by favoring their survival through the induction of Bcl-2 expression. At variance, suppression was not affected by addition of IL-13, although this cytokine shares with IL-4 a receptor chain. When naive CD4+CD25− Th cells were replaced by Th1 and Th2 cells, cell proliferation of both subsets was equally suppressed, but suppression was less pronounced compared with that of CD4+CD25− Th cells. IL-4 production by Th2 cells was also inhibited. These results indicate that although CD4+CD25+ Treg cells inhibit IL-4 production, the addition of IL-4 counteracts CD4+CD25+ Treg cell-mediated suppression by promoting CD4+CD25− Th cell survival and proliferation.
CD8 Cell Division Maintaining Cytotoxic Memory Occurs Predominantly in the Bone Marrow
Authors: Parretta Elisabetta , Cassese Giuliana , Barba Pasquale , Santoni Angela , Guardiola John , Di Rosa Francesca
Published: April 2014

Long-term persistence of Ag-experienced CD8 cells, a class of T lymphocytes with cytotoxic function, contributes to immunological memory against intracellular pathogens. After Ag clearance, memory CD8 cells are maintained over time by a slow proliferation, primarily cytokine driven. In this article, we show that the bone marrow (BM) is the crucial organ where such basal division of memory CD8 cells occurs. BM memory CD8 cells contain a higher percentage of proliferating cells than their corresponding cells in either spleen or lymph nodes from C57BL/6 mice. This occurs both in the case of memory-phenotype CD44high CD8 cells and in the case of Ag-specific memory CD8 cells. Importantly, the absolute number of Ag-specific memory CD8 cells dividing in the BM largely exceeds that in spleen, lymph nodes, liver, and lung taken together. In the BM, Ag-specific memory CD8 cells express lower levels of CD127, i.e., the α-chain of IL-7R, than in either spleen or lymph nodes. We interpret these results as indirect evidence that Ag-specific memory CD8 cells receive proliferative signals by IL-7 and/or IL-15 in the BM and propose that the BM acts as a saturable “niche” for the Ag-independent proliferation of memory CD8 cells. Taken together, our novel findings indicate that the BM plays a relevant role in the maintenance of cytotoxic T cell memory, in addition to its previously described involvement in long-term Ab responses.
Human Mast Cells Express Corticotropin-Releasing Hormone (CRH) Receptors and CRH Leads to Selective Secretion of Vascular Endothelial Growth Factor
Authors: Cao Jing , Papadopoulou Nikoletta , Kempuraj Duraisamy , Boucher William S. , Sugimoto Koreaki , Cetrulo Curtis L. , Theoharides Theoharis C.
Published: April 2014

Mast cells are critical for allergic reactions, but also for innate or acquired immunity and inflammatory conditions that worsen by stress. Corticotropin-releasing hormone (CRH), which activates the hypothalamic-pituitary-adrenal axis under stress, also has proinflammatory peripheral effects possibly through mast cells. We investigated the expression of CRH receptors and the effects of CRH in the human leukemic mast cell (HMC-1) line and human umbilical cord blood-derived mast cells. We detected mRNA for CRH-R1α, 1β, 1c, 1e, 1f isoforms, as well as CRH-R1 protein in both cell types. CRH-R2α (but not R2β or R2γ) mRNA and protein were present only in human cord blood-derived mast cells. CRH increased cAMP and induced secretion of vascular endothelial growth factor (VEGF) without tryptase, histamine, IL-6, IL-8, or TNF-α release. The effects were blocked by the CRH-R1 antagonist antalarmin, but not the CRH-R2 antagonist astressin 2B. CRH-stimulated VEGF production was mediated through activation of adenylate cyclase and increased cAMP, as evidenced by the fact that the effect of CRH was mimicked by the direct adenylate cyclase activator forskolin and the cell-permeable cAMP analog 8-bromo-cAMP, whereas it was abolished by the adenylate cyclase inhibitor SQ22536. This is the first evidence that mast cells express functional CRH receptors and that CRH can induce VEGF secretion selectively. CRH-induced mast cell-derived VEGF could, therefore, be involved in chronic inflammatory conditions associated with increased VEGF, such as arthritis or psoriasis, both of which worsen by stress.
Immunization with HIV-1 Gag Protein Conjugated to a TLR7/8 Agonist Results in the Generation of HIV-1 Gag-Specific Th1 and CD8+ T Cell Responses
Authors: Wille-Reece Ulrike , Wu Chang-you , Flynn Barbara J. , Kedl Ross M. , Seder Robert A.
Published: April 2014

One strategy to induce optimal cellular and humoral immune responses following immunization is to use vaccines or adjuvants that target dendritic cells and B cells. Activation of both cell types can be achieved using specific TLR ligands or agonists directed against their cognate receptor. In this study, we compared the ability of the TLR7/8 agonist R-848, which signals only via TLR7 in mice, with CpG oligodeoxynucleotides for their capacity to induce HIV-1 Gag-specific T cell and Ab responses when used as vaccine adjuvants with HIV-1 Gag protein in mice. Injection of R-848 and CpG oligodeoxynucleotides alone enhanced the innate immune responses in vivo as demonstrated by high serum levels of inflammatory cytokines, including IL-12p70 and IFN-α, and increased expression of CD80, CD86, and CD40 on CD11c+ dendritic cells. By contrast, R-848 was a relatively poor adjuvant for inducing primary Th1 or CD8+ T cell responses when administered with HIV-1 Gag protein. However, when a TLR7/8 agonist structurally and functionally similar to R-848 was conjugated to HIV-1 Gag protein both Th1 and CD8+ T cells responses were elicited as determined by intracellular cytokine and tetramer staining. Moreover, within the population of HIV-1 Gag-specific CD8+ CD62low cells, ∼50% of cells expressed CD127, a marker shown to correlate with the capacity to develop into long-term memory cells. Overall, these data provide evidence that TLR7/8 agonists can be effective vaccine adjuvants for eliciting strong primary immune responses with a viral protein in vivo, provided vaccine delivery is optimized.
Positive and Negative Regulation of the IL-27 Receptor during Lymphoid Cell Activation
Authors: Villarino Alejandro V. , Larkin Joseph , Saris Christiaan J. M. , Caton Andrew J. , Lucas Sophie , Wong Terence , de Sauvage Frederic J. , Hunter Christopher A.
Published: April 2014

Previous reports have focused on the ability of IL-27 to promote naive T cell responses but the present study reveals that surface expression of WSX-1, the ligand-specific component of the IL-27R, is low on these cells and that highest levels are found on effector and memory CD4+ and CD8+ T cells. Accordingly, during infection with Toxoplasma gondii, in vivo T cell activation is associated with enhanced expression of WSX-1, and, in vitro, TCR ligation can induce expression of WSX-1 regardless of the polarizing (Th1/Th2) environment present at the time of priming. However, while these data establish that mitogenic stimulation promotes expression of WSX-1 by T cells, activation of NK cells and NKT cells prompts a reduction in WSX-1 levels during acute toxoplasmosis. Together, with the finding that IL-2 can suppress expression of WSX-1 by activated CD4+ T cells, these studies indicate that surface levels of the IL-27R can be regulated by positive and negative signals associated with lymphoid cell activation. Additionally, since high levels of WSX-1 are evident on resting NK cells, resting NKT cells, effector T cells, regulatory T cells, and memory T cells, the current work demonstrates that IL-27 can influence multiple effector cells of innate and adaptive immunity.
Genetic Determination of T Cell Help in Loss of Tolerance to Nuclear Antigens
Authors: Chen Yifang , Cuda Carla , Morel Laurence
Published: April 2014

Sle1 is a major lupus susceptibility locus in NZM2410 lupus model that is associated with a loss of tolerance to nuclear Ags. At least three genes, Sle1a, Sle1b, and Sle1c contribute to Sle1, and their relative role in lupus pathogenesis is unknown. We show here that Sle1-expressing CD4+ T cells present an activated phenotype associated with increased proliferation and cytokine production. In addition, Sle1 CD4+ T cells provide help to anti-chromatin B cells to produce anti-nuclear antibodies, whether or not these B cells express Sle1. The Sle1a locus alone accounts for all these Sle1 phenotypes, implying that a specific genetic defect in Sle1a is necessary and sufficient to produce autoreactive T cells. However, Sle1c induces intermediate T cell activation and only provides help to Sle1-expressing anti-chromatin-producing B cells, demonstrating the synergic interactions between Sle1c T and Sle1 B cells. Moreover, Sle1a and Sle1c were associated with a significantly reduced level of CD4+CD25+ regulatory T cells that precedes autoantibody production, suggesting a causal relationship with the generation of autoreactive T cells. Our study identifies for the first time that a specific genetic defect is responsible for lupus pathogenesis by inducing autoreactive T cells to break self-tolerance and that this genetic defect is also associated with a decreased number of regulatory T cells.
A Role for c-fos/Activator Protein 1 in B Lymphocyte Terminal Differentiation
Authors: Ohkubo Yusuke , Arima Masafumi , Arguni Eggi , Okada Seiji , Yamashita Kimihiro , Asari Sadaki , Obata Shintaro , Sakamoto Akemi , Hatano Masahiko , O-Wang Jiyang , Ebara Masaaki , Saisho Hiromitsu , Tokuhisa Takeshi
Published: April 2014

Expression of B lymphocyte-induced maturation protein 1 (Blimp-1) transcription factor is essential for promoting B cell differentiation into plasma cells. However, a critical transcription factor for Blimp-1 expression in activated B cells is unclear. When splenic B cells were stimulated with CD40 ligand (CD40L) and IL-4, terminal differentiation was induced in the B cells from c-fos transgenic (H2-c-fos) mice but barely in those from control littermates and from c-fos-deficient mice. AP-1 family and Blimp-1 mRNAs were transiently induced in the control B cells, and overexpression of c-Fos induced a sufficient amount of Blimp-1 for terminal differentiation in the H2-c-fos B cells. When normal and c-fos-deficient B cells were stimulated with LPS, a sufficient amount of Blimp-1 for terminal differentiation was induced in those B cells. However, expression of c-fos/AP-1 family mRNAs in LPS-stimulated normal B cells was similar to that of normal B cells stimulated with CD40L and IL-4. EMSA and chromatin immunoprecipitation assays using the AP-1-binding DNA sequence in the murine Blimp-1 promoter region demonstrated that AP-1-binding activity in nuclear protein of LPS-stimulated normal B cells was prolonged more than that in normal B cells stimulated with CD40L and IL-4. Furthermore, the percentage of CD138+ B cells within germinal center B cells in the spleen and the number of Ab-forming cells in the bone marrow of H2-c-fos mice was larger than that of control mice 12 days after immunization. Thus, although c-Fos is not essential for Blimp-1 expression, c-Fos/AP-1 positively regulates Blimp-1 expression and terminal differentiation of activated B cells.
Mouse Endothelial Cells Cross-Present Lymphocyte-Derived Antigen on Class I MHC via a TAP1- and Proteasome-Dependent Pathway
Authors: Bagai Rakesh , Valujskikh Anna , Canaday David H. , Bailey Erin , Lalli Peter N. , Harding Clifford V. , Heeger Peter S.
Published: April 2014

In vivo studies suggest that vascular endothelial cells (ECs) can acquire and cross-present exogenous Ag on MHC-I but the cellular mechanisms underlying this observation remain unknown. We tested whether primary female mouse aortic ECs could cross-present exogenous male Ag to the T cell hybridoma, MHH, specific for HYUty plus Db. MHC-I-deficient male spleen cells provided a source of male Ag that could not directly stimulate the MHH cells. Addition of male but not female MHC-I-deficient spleen cells to wild-type syngeneic female EC induced MHH stimulation, demonstrating EC cross-presentation. Lactacystin treatment of the donor male MHC-I-deficient spleen cells, to inhibit proteasome function, markedly enhanced EC cross-presentation showing that the process is most efficient for intact proteins rather than degraded peptide fragments. Additional experiments revealed that this EC Ag-processing pathway is both proteasome and TAP1 dependent. These studies demonstrate that cultured murine aortic ECs can process and present MHC-I-restricted Ag derived from a separate, live cell, and they offer insight into the molecular requirements involved in this EC Ag presentation process. Through this pathway, ECs expressing cross-presented peptides can participate in the effector phase of T cell-mediated inflammatory responses such as autoimmunity, anti-tumor immunity, and transplant rejection.
IgE Generation and Mast Cell Effector Function in Mice Deficient in IL-4 and IL-13
Authors: Fish Susan C. , Donaldson Debra D. , Goldman Samuel J. , Williams Cara M. M. , Kasaian Marion T.
Published: April 2014

IL-4 and IL-13 are potent cytokines that drive production of IgE, which is critical to the development of atopic disease. In this study, we directly compared IgE generation and IgE-dependent mast cell effector function in mouse strains lacking IL-4, IL-13, IL-4 + IL-13, or their common receptor component, IL-4Rα. Although serum IgE was undetectable under resting conditions in most animals deficient in one or both cytokines, peritoneal mast cells from mice lacking IL-4 or IL-13 had only partial reductions in surface IgE level. In contrast, peritoneal mast cells from IL-4/13−/− and IL-4Rα−/− animals were severely deficient in surface IgE, and showed no detectable degranulation following treatment with anti-IgE in vitro. Surprisingly, however, intradermal challenge with high concentrations of anti-IgE Ab induced an ear-swelling response in these strains, implying some capacity for IgE-mediated effector function in tissue mast cells. Furthermore, upon specific immunization with OVA, both IL-4/IL-13−/− and IL-4Rα−/− mice produced detectable levels of serum IgE and Ag-specific IgG1, and generated strong ear-swelling responses to intradermal administration of anti-IgE. These findings suggest that a mechanism for IgE production exists in vivo that is independent of IL-4 or IL-13.
Augmentation of Cutaneous Immune Responses by ATPγS: Purinergic Agonists Define a Novel Class of Immunologic Adjuvants
Authors: Granstein Richard D. , Ding Wanhong , Huang Jing , Holzer Aton , Gallo Richard L. , Di Nardo Anna , Wagner John A.
Published: April 2014

Extracellular nucleotides activate ligand-gated P2XR ion channels and G protein-coupled P2YRs. In this study we report that intradermal administration of ATPγS, a hydrolysis-resistant P2 agonist, results in an enhanced contact hypersensitivity response in mice. Furthermore, ATPγS enhanced the induction of delayed-type hypersensitivity to a model tumor vaccine in mice and enhanced the Ag-presenting function of Langerhans cells (LCs) in vitro. Exposure of a LC-like cell line to ATPγS in the presence of LPS and GM-CSF augmented the induction of I-A, CD80, CD86, IL-1β, and IL-12 p40 while inhibiting the expression of IL-10, suggesting that the immunostimulatory activities of purinergic agonists in the skin are mediated at least in part by P2Rs on APCs. In this regard, an LC-like cell line was found to express mRNA for P2X1, P2X7, P2Y1, P2Y2, P2Y4, P2Y9, and P2Y11 receptors. We suggest that ATP, when released after trauma or infection, may act as an endogenous adjuvant to enhance the immune response, and that P2 agonists may augment the efficacy of vaccines.
The Functional Heterogeneity of Type 1 Effector T Cells in Response to Infection Is Related to the Potential for IFN-γ Production
Authors: Mayer Katrin D. , Mohrs Katja , Crowe Sherry R. , Johnson Lawrence L. , Rhyne Paul , Woodland David L. , Mohrs Markus
Published: April 2014

The expression of IFN-γ is a hallmark of Th1 cells and CD8+ effector T cells and is the signature cytokine of type 1 responses. However, it is not known whether T cells are homogeneous in their capacity to produce IFN-γ, whether this potential varies between tissues, and how it relates to the production of other effector molecules. In the present study we used bicistronic IFN-γ-enhanced yellow fluorescent protein (IFN-γ-eYFP) reporter mice (Yeti) and MHC class I tetramers to directly quantify IFN-γ expression at the single cell level. The eYFP fluorescence of Th1 cells and CD8+ effector T cells was broadly heterogeneous even before cell division and correlated with both the abundance of IFN-γ transcripts and the secretion of IFN-γ upon stimulation. CD4+ and CD8+ T cells of influenza-infected mice revealed a similarly heterogeneous IFN-γ expression, and eYFPhigh cells were only found in the infected lung. Ag-specific T cells were in all examined tissues eYFP+, but also heterogeneous in their reporter fluorescence, and eYFPhigh cells were also restricted to the infected lung. A similar heterogeneity was observed in Toxoplasma gondii-infected animals, but eYFPhigh cells were restricted to different tissues. Highly eYFP fluorescent cells produced elevated levels of proinflammatory cytokines and chemokines in addition to IFN-γ, suggesting their coregulated expression as a functional unit in highly differentiated effector T cells.