bluuebunny/crossref_metadata_2025 huggingface dataset:
Local CD11c+ MHC Class II− Precursors Generate Lung Dendritic Cells during Respiratory Viral Infection, but Are Depleted in the Process
Authors: Wang Hongwei , Peters Nina , Laza-Stanca Vasile , Nawroly Niga , Johnston Sebastian L. , Schwarze Jürgen
Published: April 2014

Increases in numbers of lung dendritic cells (DC) observed during respiratory viral infections are assumed to be due to recruitment from bone marrow precursors. No local production has been demonstrated. In this study, we isolated defined populations of murine lung cells based on CD11c and MHC class II (MHC II) expression. After culture for 12 days with GM-CSF, we analyzed cell numbers, DC surface markers, and Ag-presenting capacity. Only CD11c+ MHC II− cells from naive mice proliferated, yielding myeloid DC, which induced Ag-specific proliferation of naive T cells. After respiratory syncytial virus (RSV) infection, numbers of pulmonary CD11c+ MHC II− precursor cells were significantly reduced and DC could not be generated. Moreover, RSV infection prevented subsequent in vivo expansion of pulmonary DC in response to influenza infection or LPS treatment. These results provide direct evidence of local generation of fully functional myeloid DC in the lung from CD11c+ MHC II− precursor cells that are depleted by RSV infection, leading to an inability to expand lung DC numbers in response to subsequent viral infection or exposure to bacterial products. This depletion of local DC precursors in respiratory viral infections may be important in explaining complex interactions between multiple and intercurrent pulmonary infections.
Subunit Recombinant Vaccine Protects against Monkeypox
Authors: Heraud Jean-Michel , Edghill-Smith Yvette , Ayala Victor , Kalisz Irene , Parrino Janie , Kalyanaraman Vaniambadi S. , Manischewitz Jody , King Lisa R. , Hryniewicz Anna , Trindade Christopher J. , Hassett Meredith , Tsai Wen-Po , Venzon David , Nalca Aysegul , Vaccari Monica , Silvera Peter , Bray Mike , Graham Barney S. , Golding Hana , Hooper Jay W. , Franchini Genoveffa
Published: April 2014

The smallpox vaccine Dryvax, a live vaccinia virus (VACV), protects against smallpox and monkeypox, but is contraindicated in immunocompromised individuals. Because Abs to VACV mediate protection, a live virus vaccine could be substituted by a safe subunit protein-based vaccine able to induce a protective Ab response. We immunized rhesus macaques with plasmid DNA encoding the monkeypox orthologs of the VACV L1R, A27L, A33R, and B5R proteins by the intradermal and i.m. routes, either alone or in combination with the equivalent recombinant proteins produced in Escherichia coli. Animals that received only DNA failed to produce high titer Abs, developed innumerable skin lesions after challenge, and died in a manner similar to placebo controls. By contrast, the animals vaccinated with proteins developed moderate to severe disease (20–155 skin lesions) but survived. Importantly, those immunized with DNA and boosted with proteins had mild disease with 15 or fewer lesions that resolved within days. DNA/protein immunization elicited Th responses and binding Ab titers to all four proteins that correlated negatively with the total lesion number. The sera of the immunized macaques recognized a limited number of linear B cell epitopes that are highly conserved among orthopoxviruses. Their identification may guide future efforts to develop simpler, safer, and more effective vaccines for monkeypox and smallpox.
IL-10 Is Required for Optimal CD8 T Cell Memory followingListeria monocytogenesInfection
Authors: Foulds Kathryn E. , Rotte Masashi J. , Seder Robert A.
Published: April 2014

IL-10 is an important immunoregulatory cytokine that plays a central role in maintaining a balance between protective immunity against infection and limiting proinflammatory responses to self or cross-reactive Ags. We examined the full effects of IL-10 deficiency on the establishment and quality of T cell memory using murine listeriosis as a model system. IL-10−/− mice had reduced bacterial loads and a shorter duration of primary infection than did wild-type mice. However, the number of Ag-specific T cells in secondary lymphoid and nonlymphoid organs was diminished in IL-10−/− mice, compared with wild-type mice, at the peak of the effector response. Moreover, the frequency and protective capacity of memory T cells also were reduced in IL-10−/− mice when assessed up to 100 days postinfection. Remarkably, this effect was more pronounced for CD8 T cells than CD4 T cells. To address whether differences in the number of bacteria and duration of primary infection could explain these findings, both strains of mice were treated with ampicillin 24 hours after primary infection. Despite there being more comparable bacterial loads during primary infection, IL-10−/− mice still generated fewer memory CD8 T cells and were less protected against secondary infection than were wild-type mice. Finally, the adoptive transfer of purified CD8 T cells from previously infected wild-type mice into naive recipients conferred better protection than the transfer of CD8 T cells from immune IL-10−/− mice. Overall, these data show that IL-10 plays an unexpected role in promoting and/or sustaining CD8 T cell memory following Listeria monocytogenes infection.
TWEAK Is a Novel Arthritogenic Mediator
Authors: Perper Stuart J. , Browning Beth , Burkly Linda C. , Weng Shawn , Gao Cindy , Giza Keith , Su Lihe , Tarilonte Leticia , Crowell Thomas , Rajman Luis , Runkel Laura , Scott Martin , Atkins Gerald J. , Findlay David M. , Zheng Timothy S. , Hess Henry
Published: April 2014

TNF-like weak inducer of apoptosis (TWEAK) is a TNF family member with pleiotropic effects on a variety of cell types, one of which is the induction of proinflammatory cytokines by synovial fibroblasts derived from rheumatoid arthritis (RA) patients. In this study, we report that the serum TWEAK level was dramatically elevated during mouse collagen-induced arthritis (CIA) and blocking TWEAK by a neutralizing mAb significantly reduced the clinical severity of CIA. Histological analyses also revealed that TWEAK inhibition diminished joint inflammation, synovial angiogenesis, as well as cartilage and bone erosion. Anti-TWEAK treatment proved efficacious when administered just before the disease onset but not during the priming phase of CIA. Consistent with this, TWEAK inhibition did not affect either cellular or humoral responses to collagen. In contrast, TWEAK inhibition significantly reduced serum levels of a panel of arthritogenic mediators, including chemokines such as MIP-1β (CCL-4), lymphotactin (XCL-1), IFN-γ-inducible protein 10 (IP-10) (CXCL-10), MCP-1 (CCL-2), and RANTES (CCL-5), as well as the matrix metalloprotease-9. Exploring the possible role of the TWEAK/Fn14 pathway in human RA pathogenesis, we showed that TWEAK can target human primary chondrocytes and osteoblast-like cells, in addition to synovial fibroblasts. We further demonstrated that TWEAK induced the production of matrix metalloproteases in human chondrocytes and potently inhibited chondrogenesis and osteogenesis using in vitro models. These results provide evidence for a novel cytokine pathway that contributes to joint tissue inflammation, angiogenesis, and damage, as well as may inhibit endogenous repair, suggesting that TWEAK may be a new therapeutic target for human RA.
CCL2 Regulates Angiogenesis via Activation of Ets-1 Transcription Factor
Authors: Stamatovic Svetlana M. , Keep Richard F. , Mostarica-Stojkovic Marija , Andjelkovic Anuska V.
Published: April 2014

Although recent studies have suggested that CC chemokine CCL2 may directly affect the angiogenesis, the signaling events involved in such regulation remain to be determined. This study investigated a potential signal mechanism involved in CCL2-induced angiogenesis. Our in vitro and in vivo (hemangioma model of angiogenesis) experiments confirmed earlier findings that CCL2 can induce angiogenesis directly. Using a gene array analysis, CCL2 was found to induce expression of several angiogenic factors in brain endothelial cells. Among the most prominent was an up-regulation in Ets-1 transcription factor. CCL2 induced a significant increase in Ets-1 mRNA and protein expression as well as Ets-1 DNA-binding activity. Importantly, Ets-1 antisense oligonucleotide markedly abrogated in vitro CCL2-induced angiogenesis, suggesting that Ets-1 is critically involved in this process. Activation of Ets-1 by CCL2 further regulated some of Ets-1 target molecules including β3 integrins. CCL2 induced significant up-regulation of β3 mRNA and protein expression, and this effect of CCL2 was prevented by the Ets-1 antisense oligonucleotide. The functional regulation of Ets-1 activity by CCL2 was dependent on ERK-1/2 cascade. Inhibition of ERK1/2 activity by PD98509 prevented CCL2-induced increases in Ets-1 DNA-binding activity and Ets-1 mRNA expression. Based on these findings, we suggest that Ets-1 transcription factor plays a critical role in CCL2 actions on brain endothelial cells and CCL2-induced angiogenesis.
Papillomavirus-Like Particles Are an Effective Platform for Amyloid-β Immunization in Rabbits and Transgenic Mice
Authors: Zamora Eduardo , Handisurya Alessandra , Shafti-Keramat Saeed , Borchelt David , Rudow Gay , Conant Katherine , Cox Christopher , Troncoso Juan C. , Kirnbauer Reinhard
Published: April 2014

Immunization with amyloid-β (Aβ) prevents the deposition of Aβ in the brain and memory deficits in transgenic mouse models of Alzheimer’s disease (AD), opening the possibility for immunotherapy of AD in humans. Unfortunately, the first human trial of Aβ vaccination was complicated, in a small number of vaccinees, by cell-mediated meningoencephalitis. To develop an Aβ vaccine that lacks the potential to induce autoimmune encephalitis, we have generated papillomavirus-like particles (VLP) that display 1–9 aa of Aβ protein repetitively on the viral capsid surface (Aβ-VLP). This Aβ peptide was chosen because it contains a functional B cell epitope, but lacks known T cell epitopes. Rabbit and mouse vaccinations with Aβ-VLP were well tolerated and induced high-titer autoAb against Aβ, that inhibited effectively assembly of Aβ1–42 peptides into neurotoxic fibrils in vitro. Following Aβ-VLP immunizations of APP/presenilin 1 transgenic mice, a model for human AD, we observed trends for reduced Aβ deposits in the brain and increased numbers of activated microglia. Furthermore, Aβ-VLP vaccinated mice also showed increased levels of Aβ in plasma, suggesting efflux from the brain into the vascular compartment. These results indicate that the Aβ-VLP vaccine induces an effective humoral immune response to Aβ and may thus form a basis to develop a safe and efficient immunotherapy for human AD.
Paucity of Clinical Disease despite Serological Autoimmunity and Kidney Pathology in Lupus-Prone New Zealand Mixed 2328 Mice Deficient in BAFF
Authors: Jacob Chaim O. , Pricop Luminita , Putterman Chaim , Koss Michael N. , Liu Yi , Kollaros Maria , Bixler Sarah A. , Ambrose Christine M. , Scott Martin L. , Stohl William
Published: April 2014

Constitutive overexpression of B cell-activating factor belonging to the TNF family (BAFF) promotes development of systemic lupus erythematosus (SLE), and treatment of SLE mice with BAFF antagonists ameliorates disease. To determine whether SLE can develop de novo in BAFF-deficient hosts, BAFF-deficient New Zealand Mixed (NZM) 2328 (NZM.Baff−/−) mice were generated. In NZM.Baff−/− mice, spleen B cells (including CD5+ B1a and CD5− B1b B cells), germinal centers, Ig-secreting cells, and T cells were reduced in comparison to NZM.Baff+/+ mice. Serum total Ig and autoantibody levels were reduced at 4–6 mo but approached wild-type levels with increasing age, indicating that autoreactive B cells can survive and secrete autoantibodies despite the complete absence of BAFF. At least some of these autoantibodies are nephrophilic in that glomerular deposition of total IgG and IgG1 (but not of IgG2a, IgG2b, or C3) was substantial in NZM.Baff−/− mice by 12–13 mo of age. Despite proliferative glomerulonephritis, highlighted by widespread glomerular hyaline thrombi, being common among NZM.Baff−/− mice by 6–7 mo of age, severe proteinuria and mortality were greatly attenuated. These results demonstrate that the lifelong absence of BAFF does not protect NZM 2328 mice from serological autoimmunity and renal pathology. Nevertheless, the character of the renal pathology is altered, and the mice are largely spared from clinically overt disease (severe proteinuria and premature death). These observations may have profound ramifications for the use of BAFF antagonists in human SLE and related diseases.
Calcineurin Is Expressed and Plays a Critical Role in Inflammatory Arthritis
Authors: Yoo Seung-Ah , Park Bo-Hyoung , Park Gyeong-Sin , Koh Hae-Seok , Lee Mi-Sook , Ryu Sung Ho , Miyazawa Keiji , Park Sung-Hwan , Cho Chul-Soo , Kim Wan-Uk
Published: April 2014

Calcineurin is a calcium-activated phosphatase to mediate lymphocyte activation and neuron signaling, but its role in inflammatory arthritis remains largely unknown. In this study, we demonstrate that calcineurin was highly expressed in the lining layer, infiltrating leukocytes, and endothelial cells of rheumatoid synovium. The basal expression levels of calcineurin were higher in the cultured synoviocytes of rheumatoid arthritis patients than those of osteoarthritis patients. The calcineurin activity in the synoviocytes was increased by the stimulation with proinflammatory cytokines such as IL-1β and TNF-α. Moreover, rheumatoid arthritis synoviocytes had an enlarged intracellular Ca2+ store and showed a higher degree of [Ca2+]i release for calcineurin activity than osteoarthritis synoviocytes when stimulated with either TNF-α or phorbol myristate acetate. IL-10, an anti-inflammatory cytokine, failed to increase the Ca2+ and calcineurin activity. The targeted inhibition of calcineurin by the overexpression of calcineurin-binding protein 1, a natural calcineurin antagonist, inhibited the production of IL-6 and matrix metalloproteinase-2 by rheumatoid synoviocytes in a similar manner to the calcineurin inhibitor, cyclosporin A. Moreover, the abundant calcineurin expression was found in the invading pannus in the joints of mice with collagen-induced arthritis. In these mice, calcineurin activity in the cultured synovial and lymph node cells correlated well with the severity of arthritis, but which was suppressed by cyclosporin A treatment. Taken together, our data suggest that the abnormal activation of Ca2+ and calcineurin in the synoviocytes may contribute to the pathogenesis of chronic arthritis and thus provide a potential target for controlling inflammatory arthritis.
Spontaneous CD4+ T Cell Responses against TRAG-3 in Patients with Melanoma and Breast Cancers
Authors: Janjic Bratislav , Andrade Pedro , Wang Xiao-Fei , Fourcade Julien , Almunia Christine , Kudela Pavol , Brufsky Adam , Jacobs Samuel , Friedland David , Stoller Ronald , Gillet Daniel , Herberman Ronald B. , Kirkwood John M. , Maillere Bernard , Zarour Hassane M.
Published: April 2014

The taxol resistance gene TRAG-3 was initially isolated from cancer cell lines that became resistant to taxol in vitro. TRAG-3 is a cancer germline Ag expressed by tumors of different histological types including the majority of melanoma, breast, and lung cancers. In the present study, we report that patients with stage IV melanoma and breast cancers developed spontaneous IFN-γ-producing CD4+ T cell responses against a single immunodominant and promiscuous peptide epitope from TRAG-3 presented in the context of multiple HLA-DR molecules. The TRAG-3-specific CD4+ T cells and clones were expanded in vitro and recognized not only peptide pulsed APCs but also autologous dendritic cells (DCs) loaded with the TRAG-3 protein. All stage IV melanoma patients with TRAG-3-expressing tumors developed spontaneous CD4+ T cell responses against TRAG-3, demonstrating its strong immunogenicity. None of these patients had detectable IgG Ab responses against TRAG-3. TCRβ gene usage studies of TRAG-3-specific CD4+ T cell clones from a melanoma patient and a normal donor suggested a restricted TCR repertoire in patients with TRAG-3-expressing tumors. Altogether, our data define a novel profile of spontaneous immune responses to cancer germline Ag-expressing tumors, showing that spontaneous TRAG-3-specific CD4+ T cells are directed against a single immunodominant epitope and exist independently of Ab responses. Because of its immunodominance, peptide TRAG-334–48 is of particular interest for the monitoring of spontaneous immune responses in patients with TRAG-3-expressing tumors and for the development of cancer vaccines.
B-1 B Cell Development
Authors: Hardy Richard R.
Published: April 2014

CD5+ B cells have attracted considerable interest because of their association with self-reactivity, autoimmunity, and leukemia. In mice, CD5+ B cells are readily generated from fetal/neonatal precursors, but inefficiently from precursors in adult. One model proposed to explain this difference is that their production occurs through a distinctive developmental process, termed B-1, that enriches pre-B cells with novel germline VDJs and that requires positive selection of newly formed B cells by self-Ag. In contrast, follicular B cells are generated throughout adult life in a developmental process termed B-2, selecting VDJs that pair well with surrogate L chain, and whose maturation appears relatively independent of antigenic selection. In the present study, I focus on processes that shape the repertoire of mouse CD5+ B cells, describing the differences between B-1 and B-2 development, and propose a model encompassing both in the generation of functional B cell subpopulations.
Cutting Edge: Interleukin 4-Dependent Mast Cell Proliferation Requires Autocrine/Intracrine Cysteinyl Leukotriene-Induced Signaling
Authors: Jiang Yongfeng , Kanaoka Yoshihide , Feng Chunl , Nocka Karl , Rao Sudhir , Boyce Joshua A.
Published: April 2014

Reactive mastocytosis (RM) in epithelial surfaces is a consistent Th2-associated feature of allergic disease. RM fails to develop in mice lacking leukotriene (LT) C4 synthase (LTC4S), which is required for cysteinyl leukotriene (cys-LT) production. We now report that IL-4, which induces LTC4S expression by mast cells (MCs), requires cys-LTs, the cys-LT type 1 receptor (CysLT1), and Gi proteins to promote MC proliferation. LTD4 (10–1000 nM) enhanced proliferation of human MCs in a CysLT1-dependent, pertussis toxin-sensitive manner. LTD4-induced phosphorylation of ERK required transactivation of c-kit. IL-4-driven comitogenesis was likewise sensitive to pertussis toxin or a CysLT1-selective antagonist and was attenuated by treatment with leukotriene synthesis inhibitors. Mouse MCs lacking LTC4S or CysLT1 showed substantially diminished IL-4-induced comitogenesis. Thus, IL-4 induces proliferation in part by inducing LTC4S and cys-LT generation, which causes CysLT1 to transactivate c-kit in RM.
Cutting Edge: IL-23 Cross-Regulates IL-12 Production in T Cell-Dependent Experimental Colitis
Authors: Becker Christoph , Dornhoff Heike , Neufert Clemens , Fantini Massimo C. , Wirtz Stefan , Huebner Sabine , Nikolaev Alexei , Lehr Hans-Anton , Murphy Andrew J. , Valenzuela David M. , Yancopoulos George D. , Galle Peter R. , Karow Margaret , Neurath Markus F.
Published: April 2014

Although IL-12 and IL-23 share the common p40 subunit, IL-23, rather than IL-12, seems to drive the pathogenesis of experimental autoimmune encephalomyelitis and arthritis, because IL-23/p19 knockout mice are protected from disease. In contrast, we describe in this study that newly created LacZ knockin mice deficient for IL-23 p19 were highly susceptible for the development of experimental T cell-mediated TNBS colitis and showed even more severe colitis than wild-type mice by endoscopic and histologic criteria. Subsequent studies revealed that dendritic cells from p19-deficient mice produce elevated levels of IL-12, and that IL-23 down-regulates IL-12 expression upon TLR ligation. Finally, in vivo blockade of IL-12 p40 in IL-23-deficient mice rescued mice from lethal colitis. Taken together, our data identify cross-regulation of IL-12 expression by IL-23 as novel key regulatory pathway during initiation of T cell dependent colitis.
Cutting Edge: Critical Role for A2A Adenosine Receptors in the T Cell-Mediated Regulation of Colitis
Authors: Naganuma Makoto , Wiznerowicz Elizabeth B. , Lappas Courtney M. , Linden Joel , Worthington Mark T. , Ernst Peter B.
Published: April 2014

A2A adenosine receptors (A2AAR) inhibit inflammation, although the mechanisms through which adenosine exerts its effects remain unclear. Although the transfer of regulatory Th cells blocks colitis induced by pathogenic CD45RBhigh Th cells, we show that CD45RBlow or CD25+ Th cells from A2AAR-deficient mice do not prevent disease. Moreover, CD45RBhigh Th cells from A2AAR-deficient mice were not suppressed by control CD45RBlow Th cells. A2AAR agonists suppressed the production of proinflammatory cytokines by CD45RBhigh and CD45RBlow T cells in association with a loss of mRNA stability. In contrast, anti-inflammatory cytokines, including IL-10 and TGF-β, were minimally affected. Oral administration of the A2AAR agonist ATL313 attenuated disease in mice receiving CD45RBhigh Th cells. These data suggest that A2AAR play a novel role in the control of T cell-mediated colitis by suppressing the expression of proinflammatory cytokines while sparing anti-inflammatory activity mediated by IL-10 and TGF-β.
CD103 Is a Marker for Alloantigen-Induced Regulatory CD8+ T Cells
Authors: Uss Elena , Rowshani Ajda T. , Hooibrink Berend , Lardy Neubury M. , van Lier René A. W. , ten Berge Ineke J. M.
Published: April 2014

The αEβ7 integrin CD103 may direct lymphocytes to its ligand E-cadherin. CD103 is expressed on T cells in lung and gut and on allograft-infiltrating T cells. Moreover, recent studies have documented expression of CD103 on CD4+ regulatory T cells. Approximately 4% of circulating CD8+ T cells bear the CD103 molecule. In this study, we show that the absence or presence of CD103 was a stable trait when purified CD103− and CD103+CD8+ T cell subsets were stimulated with a combination of CD3 and CD28 mAbs. In contrast, allostimulation induced CD103 expression on ∼25% of purified CD103−CD8+ T cells. Expression of CD103 on alloreactive cells was found to be augmented by IL-4, IL-10, or TGF-β and decreased by addition of IL-12 to MLCs. The alloantigen-induced CD103+CD8+ T cell population appeared to be polyclonal and retained CD103 expression after restimulation. Markedly, in vitro-expanded CD103+CD8+ T cells had low proliferative and cytotoxic capacity, yet produced considerable amounts of IL-10. Strikingly, they potently suppressed T cell proliferation in MLC via a cell-cell contact-dependent mechanism. Thus, human alloantigen-induced CD103+CD8+ T cells possess functional features of regulatory T cells.
Age-Related CD8+ T Cell Clonal Expansions Express Elevated Levels of CD122 and CD127 and Display Defects in Perceiving Homeostatic Signals
Authors: Messaoudi Ilhem , Warner Jessica , Nikolich-Žugich Janko
Published: April 2014

Aging is accompanied by numerous changes in T cell biology. Among the most dramatic changes at the population level are the appearance and persistence of CD8+ T cell clonal expansions (TCE), whose frequency increases steadily with age, and whose biology is incompletely understood. In this study, we examined trafficking, phenotypic makeup, and homeostatic responsiveness of TCE, which arise spontaneously in specific pathogen-free mice. We show that these cells make up a specialized subset of central memory T cells with distinguishable phenotypic characteristics, most notably the higher expression of CD122 and CD127, molecules that make up IL-15R and IL-7R, respectively, than other memory T cells. We confirm that these cells proliferate at a continuous pace upon adoptive transfer into the eulymphoid recipient, unlike their non-TCE memory-phenotype counterparts, which remain undivided and die. However, upon transfer into lymphopenic recipients, TCE fail to rapidly expand, but rather resume their slow, continuous proliferation. The above results are discussed in light of possible mechanisms that afford selective survival advantage to TCE over other T cells in an aged T lymphocyte pool.
EBV Latent Membrane Protein 2A Induces Autoreactive B Cell Activation and TLR Hypersensitivity
Authors: Wang Hongsheng , Nicholas Matilda W. , Conway Kara L. , Sen Pradip , Diz Ramiro , Tisch Roland M. , Clarke Stephen H.
Published: April 2014

EBV is associated with systemic lupus erythematosus (SLE), but how it might contribute to the etiology is not clear. Since EBV-encoded latent membrane protein 2A (LMP2A) interferes with normal B cell differentiation and function, we sought to determine its effect on B cell tolerance. Mice transgenic for both LMP2A and the Ig transgene 2-12H specific for the ribonucleoprotein Smith (Sm), a target of the immune system in SLE, develop a spontaneous anti-Sm response. LMP2A allows anti-Sm B cells to overcome the regulatory checkpoint at the early preplasma cell stage by a self-Ag-dependent mechanism. LMP2A induces a heightened sensitivity to TLR ligand stimulation, resulting in increased proliferation or Ab-secreting cell differentiation or both. Thus, we propose a model whereby LMP2A induces hypersensitivity to TLR stimulation, leading to activation of anti-Sm B cells through the BCR/TLR pathway. These data further implicate TLRs in the etiology of SLE and suggest a mechanistic link between EBV infection and SLE.
Humoral Immune Response to Flagellin Requires T Cells and Activation of Innate Immunity
Authors: Sanders Catherine J. , Yu Yimin , Moore Daniel A. , Williams Ifor R. , Gewirtz Andrew T.
Published: April 2014

Bacterial flagellin, the primary structural component of flagella, is a dominant target of humoral immunity upon infection by enteric pathogens and in Crohn’s disease. To better understand how such responses may be regulated, we sought to define, in mice, basic mechanisms that regulate generation of flagellin-specific Igs. We observed that, in response to i.p. injection with flagellin, generation of flagellin-specific Ig required activation of innate immunity in that these responses were ablated in MyD88-deficient mice and that flagellin from Helicobacter pylori, which is known not to activate TLR5, also did not elicit Abs. Mice lacking αβ T cells (TCRβnull) were completely deficient in their ability to make flagellin Abs in various contexts indicating that, in contrast to common belief, generation of flagellin-specific Ig is absolutely T cell dependent. In contrast to Ab responses to whole flagella (H serotyping), responses to flagellin monomers displayed only moderate serospecificity. Whereas neither oral nor rectal administration of flagellin elicited a strong serum Ab response, induction of colitis with dextran sodium sulfate resulted in a MyD88-dependent serum Ab response to endogenous flagellin, suggesting that, in an inflammatory milieu, TLR signaling promotes acquisition of Abs to intestinal flagellin. Thus, acquisition of a humoral immune response to flagellin requires activation of innate immunity, is T cell dependent, and can originate from flagellin in the intestinal tract in inflammatory conditions in the intestine.
All-transRetinoic Acid Stimulates IL-2-Mediated Proliferation of Human T Lymphocytes: Early Induction of Cyclin D3
Authors: Engedal Nikolai , Gjevik Tone , Blomhoff Rune , Blomhoff Heidi Kiil
Published: April 2014

Vitamin A is established as an important immune regulator, but the mechanisms whereby vitamin A regulates T cell biology are poorly defined. In this study, we show that an active metabolite of vitamin A, all-trans retinoic acid (RA), potently stimulates T cell proliferation by modulating IL-2-mediated signaling downstream of IL-2R and independent of the induction of IL-2. Thus, at concentrations as low as 0.1 nM, RA enhanced the division of normal human T lymphocytes that were simultaneously stimulated with anti-CD3 mAbs and saturating concentrations of IL-2. At the optimal concentration of RA (50 nM), a 3-fold increase in T cell proliferation was observed. The induced proliferation was preceded by increased phosphorylation of the retinoblastoma protein and enhanced G1- to S-phase progression. Interestingly, the promitogenic effect of RA was found to be particularly directed toward increased expression of cyclin D3 at both the mRNA and protein level. Furthermore, the stimulatory effect of RA on cyclin D3 expression as well as on cell proliferation was completely abolished in the presence of the JAK inhibitor AG-490 or blocking IL-2Rα mAbs, and RA also enhanced cyclin D3 expression and T cell proliferation in the presence of IL-2 alone. Finally, we showed that the proliferative effect of RA was mimicked by agonists of the retinoic acid receptor (RAR) and completely inhibited by a RAR-selective antagonist. In conclusion, our results indicate that RA, via RAR, stimulates IL-2-induced signaling in a JAK-dependent manner to enhance cyclin D3 expression and thereby promote T cell proliferation.
Overcoming Original Antigenic Sin to Generate New CD8 T Cell IFN-γ Responses in an Antigen-Experienced Host
Authors: Liu Xiao Song , Dyer Joanne , Leggatt Graham R. , Fernando Germain J. P. , Zhong Jie , Thomas Ranjeny , Frazer Ian H.
Published: April 2014

The failure to mount effective immunity to virus variants in a previously virus-infected host is known as original antigenic sin. We have previously shown that prior immunity to a virus capsid protein inhibits induction by immunization of an IFN-γ CD8+ T cell response to an epitope linked to the capsid protein. We now demonstrate that capsid protein-primed CD4+ T cells secrete IL-10 in response to capsid protein presented by dendritic cells, and deviate CD8+ T cells responding to a linked MHC class I-restricted epitope to reduce IFN-γ production. Neutralizing IL-10 while delivering further linked epitope, either in vitro or in vivo, restores induction by immunization of an Ag-specific IFN-γ response to the epitope. This finding demonstrates a strategy for overcoming inhibition of MHC class I epitopes upon immunization of a host already primed to Ag, which may facilitate immunotherapy for chronic viral infection or cancer.
CD4 T Cell-Mediated Protection from Lethal Influenza: Perforin and Antibody-Mediated Mechanisms Give a One-Two Punch
Authors: Brown Deborah M. , Dilzer Allison M. , Meents Dana L. , Swain Susan L.
Published: April 2014

The mechanisms whereby CD4 T cells contribute to the protective response against lethal influenza infection remain poorly characterized. To define the role of CD4 cells in protection against a highly pathogenic strain of influenza, virus-specific TCR transgenic CD4 effectors were generated in vitro and transferred into mice given lethal influenza infection. Primed CD4 effectors conferred protection against lethal infection over a broad range of viral dose. The protection mediated by CD4 effectors did not require IFN-γ or host T cells, but did result in increased anti-influenza Ab titers compared with untreated controls. Further studies indicated that CD4-mediated protection at high doses of influenza required B cells, and that passive transfer of anti-influenza immune serum was therapeutic in B cell-deficient mice, but only when CD4 effectors were present. Primed CD4 cells also acquired perforin (Pfn)-mediated cytolytic activity during effector generation, suggesting a second mechanism used by CD4 cells to confer protection. Pfn-deficient CD4 effectors were less able to promote survival in intact BALB/c mice and were unable to provide protection in B cell-deficient mice, indicating that Ab-independent protection by CD4 effectors requires Pfn. Therefore, CD4 effectors mediate protection to lethal influenza through at least two mechanisms: Pfn-mediated cytotoxicity early in the response promoted survival independently of Ab production, whereas CD4-driven B cell responses resulted in high titer Abs that neutralized remaining virus.
Indirect Effects of Leptin Receptor Deficiency on Lymphocyte Populations and Immune Response in db/db Mice
Authors: Palmer Gaby , Aurrand-Lions Michel , Contassot Emmanuel , Talabot-Ayer Dominique , Ducrest-Gay Dominique , Vesin Christian , Chobaz-Péclat Véronique , Busso Nathalie , Gabay Cem
Published: April 2014

Leptin-deficient ob/ob and leptin receptor (Ob-rb)-deficient db/db mice display a marked thymic atrophy and exhibit defective immune responses. Lymphocytes express leptin receptors and leptin exerts direct effects on T cells in vitro. In addition, ob/ob and db/db mice display multiple neuroendocrine and metabolic defects, through which leptin deficiency may indirectly affect the immune system in vivo. To study the relative contributions of direct and indirect effects of leptin on the immune system in a normal environment, we generated bone marrow chimeras (BMCs) by transplantation of leptin receptor-deficient db/db, or control db/+, bone marrow cells into wild-type (WT) recipients. The size and cellularity of the thymus, as well as cellular and humoral immune responses, were similar in db/db to WT and db/+ to WT BMCs. The immune phenotype of db/db mice is thus not explained by a cell autonomous defect of db/db lymphocytes. Conversely, thymus weight and cell number were decreased in the reverse graft setting in WT to db/db BMCs, indicating that expression of the leptin receptor in the environment is important for T cell development. Finally, normal thymocyte development occurred in fetal db/db thymi transplanted into WT hosts, indicating that direct effects of leptin are not required locally in the thymic microenvironment. In conclusion, direct effects of leptin on bone marrow-derived cells and on thymic stromal cells are not necessary for T lymphocyte maturation in normal mice. In contrast, leptin receptor deficiency affects the immune system indirectly via changes in the systemic environment.
DAP12 Signaling Regulates Plasmacytoid Dendritic Cell Homeostasis and Down-Modulates Their Function during Viral Infection
Authors: Sjölin Hanna , Robbins Scott H. , Bessou Gilles , Hidmark Åsa , Tomasello Elena , Johansson Maria , Hall Håkan , Charifi Férose , Hedestam Gunilla B. Karlsson , Biron Christine A. , Kärre Klas , Höglund Petter , Vivier Eric , Dalod Marc
Published: April 2014

DAP12 is an ITAM-containing adaptor molecule conveying activating properties to surface receptors on many cell types. We show here that DAP12 paradoxically down-modulates plasmacytoid dendritic cell (pDC) cytokine production in vivo during murine CMV (MCMV) infection. Higher levels of IFN-αβ and IL-12 were detected upon MCMV infection or CpG treatment in DAP12-deficient (DAP12°) mice as compared with wild-type (WT) mice. This resulted from altered homeostasis and enhanced responsiveness of pDCs in DAP12° animals. Increased numbers of pDCs were observed in the periphery of both naive and MCMV-infected DAP12° mice. A higher proportion of pDCs was activated in infected DAP12° mice, as demonstrated by intracellular staining using an optimized protocol for simultaneous detection of IFN-α and IFN-β. The homeostasis of WT and DAP12° pDCs did not differ in mixed bone marrow chimeric mice. In addition, a similar efficiency of pDC differentiation was observed in vitro in Fms-like tyrosine kinase receptor 3 ligand cultures of WT and DAP12° bone marrow cells. This suggests that DAP12 signaling effects on pDC homeostasis are indirect. In contrast, in response to CpG, DAP12-mediated effects on both IL-12 and IFN-αβ production were intrinsic to the pDCs. However, in response to MCMV, only IL-12 but not IFN-αβ production was affected by pDC-intrinsic DAP12 signaling. Thus, DAP12 signaling in pDCs can mediate different regulatory effects on their functions, depending on the mechanisms of pDC activation. The potential implications of the regulation of pDC functions by DAP12 for promoting health over disease are discussed.
The Level of IgE Produced by a B Cell Is Regulated by Norepinephrine in a p38 MAPK- and CD23-Dependent Manner
Authors: Pongratz Georg , McAlees Jaclyn W. , Conrad Daniel H. , Erbe Robert S. , Haas Karen M. , Sanders Virginia M.
Published: April 2014

Although the causes of asthma vary, the severity of the disease correlates with the level of IgE produced. In this study we show that mice produced less IgE when they were depleted of the neurotransmitter norepinephrine (NE) before the administration of Ag. The suppression was prevented when a β2-adrenergic receptor (β2AR)-selective agonist was administered, suggesting that NE stimulated the β2AR to regulate the level of an IgE response in vivo. Although the cell targeted by NE to produce this effect in vivo is unknown, we show in vitro that the level of IgE increased on a per cell basis without an effect on class switch recombination when NE stimulated the β2AR on a B cell directly. The β2AR-induced increase in IgE depended on p38 MAPK but not protein kinase A activation, was due to an increased rate of mature IgE mRNA transcription, and was lost when β2AR-deficient B cells were used. Also, CD23 transcription was increased in a p38 MAPK-dependent manner and resulted in an increased level of soluble CD23 (sCD23). The β2AR-induced increase in sCD23 was associated with IgE up-regulation and possibly interacted with CD21/CD19. Using B cells from respective knockout mice, data showed that the β2AR-induced increase in IgE depended on B cell expression of CD23, CD21, and CD19. These findings suggest that at least one mechanism by which endogenous B cell activity in vivo is regulated by NE involves stimulation of the β2AR on the B cell alone to increase the level of IgE produced in a p38 MAPK- and sCD23-dependent manner.
CD4+ T Cell Expressed CD80 Regulates Central Nervous System Effector Function and Survival during Experimental Autoimmune Encephalomyelitis
Authors: Podojil Joseph R. , Kohm Adam P. , Miller Stephen D.
Published: April 2014

CD80 expressed on the surface of APCs provides a positive costimulatory signal to naive CD4+ T cells during activation. Therefore, it was hypothesized that treatment of SJL mice with various forms of anti-CD80 mAb during remission from the acute phase of relapsing experimental autoimmune encephalomyelitis (R-EAE) would ameliorate disease progression. We previously reported that treatment of SJL mice with anti-CD80 Fab during R-EAE remission blocked activation of T cells specific for endogenous myelin epitopes, inhibiting epitope spreading and clinical disease progression; however, treatment with the native form of the same anti-CD80 mAb exacerbated disease progression. The current data show that intact anti-CD80 mAb binds both CNS-infiltrating CD4+ T cells and CD11c+ dendritic cells and that exacerbation of R-EAE directly correlates with increased survival and activity of myelin-specific CD4+ T cells, while the percentage of CD11c+ dendritic cells in the CNS and their APC activity was not altered. In vitro data show that cross-linking CD80 on the surface of CD4+ T cells activated in the presence of Th1-promoting cytokines increases the level of T cell activation, effector function, and survival by directly up-regulating the expression levels of transcripts for T-bet, IFN-γ, and Bcl-xL. These findings indicate a novel regulatory role for CD80-mediated intracellular signals in CD4+ T cells and have important implications for using anti-costimulatory molecule mAb therapy in established autoimmune disease.
Requirement for CD70 in CD4+ Th Cell-Dependent and Innate Receptor-Mediated CD8+ T Cell Priming
Authors: Taraban Vadim Y. , Rowley Tania F. , Tough David F. , Al-Shamkhani Aymen
Published: April 2014

Dendritic cell (DC) conditioning by CD4+ T cells, or via engagement of innate receptors, is thought to be essential for CD8+ T cell priming. However, the molecular features that distinguish a conditioned DC from an unconditioned DC are poorly defined. In this study, we investigate the role of CD70, a member of the TNF superfamily that is expressed on activated DC, in CD4+ Th-dependent and -independent CD8+ T cell responses. We demonstrate that CD70 is required for CD4+ T cell-dependent priming of CD8+ T cells as well as priming mediated by the viral signature, dsRNA. Accordingly, mice that were subjected to CD70 blockade during the primary response fail to generate a memory CD8+ T cell response. Furthermore, we find that CD70 is dispensable for CD4+ T cell expansion and help for B cells, thus suggesting a direct role for CD70 in CD8+ T cell priming. Our results show that the innate and adaptive (CD4+ T cells) arms of the immune system use a common signaling pathway in driving CD8+ T cell responses and suggest that expression of CD70 on DC represents the hallmark of conditioned DC.
IFN-γ Regulates Donor CD8 T Cell Expansion, Migration, and Leads to Apoptosis of Cells of a Solid Tumor
Authors: Hollenbaugh Joseph A. , Dutton Richard W.
Published: April 2014

We previously reported that IFN-γ secreted by donor cytotoxic T cell 1 (Tc1) cells was the most important factor in promoting EG7 (an OVA transfection the EL4 thymoma) rejection in mice. In this study, we show that the ability of the host to respond to Tc1-secreted IFN-γ is critical for promoting acute tumor rejection, while host production of IFN-γ is not important. CFSE-labeled wild-type and IFN-γ-deficient Tc1 cells divide rapidly in secondary lymphoid organs, indicating no defect in rate of cell division. However, wild-type Tc1 cells accumulate to significantly greater numbers in the tumor than deficient Tc1 cells. Hosts injected with wild-type Tc1 effectors had more T cells within the tumor at day 4, had higher levels of MCP-1, IFN-γ-inducible protein-10, MIP-1α, and MIP-1β mRNA transcripts, had greater numbers of CD11b+ and Gr-1+ cells within the tumor, and had massive regions of tumor cell apoptosis as compared with IFN-γ knockout Tc1 cell-treated hosts. NO has a cytostatic effect on EG7 growth in vitro, and NO is important for tumor eradication by day 22. These observations are compatible with a model in which the donor CD8 Tc1 effectors expand rapidly in the host, migrate to the tumor site, and induce the secretion of a number of chemokines that in turn recruit host cells that then attack the tumor.
T Cell Conditioning Explains Early Disappearance of the Memory CD8 T Cell Response to Infection
Authors: Jabbari Ali , Legge Kevin L. , Harty John T.
Published: April 2014

Memory CD8 T cells respond more rapidly to acute intracellular infections than naive CD8 T cells. An understanding of the biological processes involved in memory CD8 T cell recognition of Ag and up-regulation of effector mechanism necessitates analyzing memory CD8 T cells at early time points after infection. In the current study, we show that memory CD8 T cells ostensibly disappear from the spleens, blood, and peripheral organs of mice early after infection with Listeria monocytogenes. This disappearance is critically dependent on Ag, and cell-associated Ag alone can mediate this phenomenon. Further investigations, however, suggest that this disappearance is secondary to T cell-APC interactions, also known as T cell conditioning, and disruption of these putative interactions during splenic processing improves recovery of Ag-specific memory CD8 T cell populations after immunization. Conventional analyses of memory CD8 T cell populations early after infection and possibly in the presence of low levels of Ag (as during chronic infections) may exclude significant numbers of the responding CD8 T cell population.
Human Macrophages Constitute Targets for Immunotoxic Inorganic Arsenic
Authors: Lemarie Anthony , Morzadec Claudie , Bourdonnay Emilie , Fardel Olivier , Vernhet Laurent
Published: April 2014

Chronic exposure to inorganic arsenic, a widely distributed environmental contaminant, can lead to toxic effects, including immunosuppression. Owing to the established roles of human macrophages in immune defense, we determined, in the present study, whether inorganic arsenic can affect these major immune cells. Our results demonstrate that noncytotoxic concentrations of arsenic trioxide (As2O3), an inorganic trivalent form, markedly impair differentiated features of human blood monocyte-derived macrophages. First, treatment of macrophages with 1 μM As2O3 induced a rapid cell rounding and a subsequent loss of adhesion. These morphologic alterations were associated with a marked reorganization of actin cytoskeleton, which includes retraction of peripheral actin extensions and formation of a cortical actin ring. In addition, As2O3 reduced expression of various macrophagic surface markers, enhanced that of the monocytic marker CD14, and altered both endocytosis and phagocytosis; unexpectedly, exposure of macrophages to the metalloid also strongly potentiated expression of TNFα and IL-8 induced by LPS. Finally, like monocytes, As2O3-treated macrophages can be differentiated into dendritic-like cells. Impairment of macrophage function by As2O3 mainly resulted from activation of a RhoA/Rho-associated kinase pathway; indeed, pretreatment of macrophages with the Rho-associated kinase inhibitor Y-27632 prevented metalloid effects on cytoskeleton and phagocytosis. Moreover, As2O3 was found to increase level of the active GTP-bound form of RhoA and that of phosphorylated-Moesin, a major cytoskeleton adaptor protein involved in RhoA regulation. Taken together, our results demonstrated that human macrophages constitute sensitive targets of inorganic arsenic, which may contribute to immunotoxicity of this environmental contaminant.
Increased B Cell Survival and Preferential Activation of the Memory Compartment by a Malaria Polyclonal B Cell Activator
Authors: Donati Daria , Mok Bobo , Chêne Arnaud , Xu Hong , Thangarajh Mathula , Glas Rickard , Chen Qijun , Wahlgren Mats , Bejarano Maria Teresa
Published: April 2014

Chronic malaria infection is characterized by polyclonal B cell activation, hyperglobulinemia, and elevated titers of autoantibodies. We have recently identified the cysteine-rich interdomain region 1α (CIDR1α) of the Plasmodium falciparum erythrocyte membrane protein 1 as a T cell-independent polyclonal B cell activator and Ig binding protein. Here, we show that, although the binding affinity of CIDR1α to human IgM and IgG is relatively low, B cell activation still proceeds. CIDR1α rescues tonsillar B cells from apoptosis, and increases the proportion of cycling cells. Comparison of the impact on naive and memory B cell compartment indicated that CIDR1α preferentially activates memory B lymphocytes. Analysis of the gene expression profiles induced by CIDR1α and anti-Ig activation using a cDNA microarray demonstrated a low degree of homology in the signatures imposed by both stimuli. The microarray data correlate with the functional analysis demonstrating that CIDR1α activates various immunological pathways and protects B cells from apoptosis. Together, the results provide evidence for a role of malaria in preferentially activating the memory B cell compartment. The polyclonal B cell activation and augmented survival induced by CIDR1α is of relevance for understanding the mechanisms behind the increased risk of Burkitt’s lymphoma in malaria endemic areas.