bluuebunny/crossref_metadata_2025 huggingface dataset:
Fc- and Complement-Receptor Activation Stimulates Cell Cycle Progression of Macrophage Cells from G1 to S
Authors: Luo Yong , Tucker Stephanie C. , Casadevall Arturo
Published: April 2014

Phagocytosis of microorganisms by macrophages is an important host defense mechanism. While studying the phagocytosis of the human pathogenic fungus Cryptococcus neoformans, we noted that macrophage-like J774 cells with ingested fungal cells had frequent mitotic figures. By analyzing the relative proportion of phagocytic cells as a function of cell cycle phase, we observed an increase in S phase cells after Fc-mediated phagocytosis of polystyrene beads, live or heat-killed C. neoformans. This result was confirmed by increased nuclear BrdU incorporation after Fc-mediated phagocytosis. The induced progression to S phase was observed after both Fc- and complement-mediated phagocytosis of live yeasts. Fc-mediated stimulation of cell division did not require ingestion, because it could be triggered by incubating cells in IgG1-coated plates. Phagocytosis-mediated stimulation of replication was confirmed in vitro using primary bone marrow macrophages and in vivo for peritoneal macrophages. We conclude that phagocytosis of microbes or inert particles can stimulate macrophages to enter S phase and commence cell division. This observation suggests a potential mechanism for increasing the number of effector cells after microbial ingestion, but can also promote the spread of infection.
Astrocyte-Derived ATP Induces Vesicle Shedding and IL-1β Release from Microglia
Authors: Bianco Fabio , Pravettoni Elena , Colombo Alessio , Schenk Ursula , Möller Thomas , Matteoli Michela , Verderio Claudia
Published: April 2014

ATP has been indicated as a primary factor in microglial response to brain injury and inflammation. By acting on different purinergic receptors 2, ATP is known to induce chemotaxis and stimulate the release of several cytokines from these cells. The activation of purinergic receptors 2 in microglia can be triggered either by ATP deriving from dying cells, at sites of brain injury or by ATP released from astrocytes, in the absence of cell damage. By the use of a biochemical approach integrated with video microscopy experiments, we investigated the functional consequences triggered in microglia by ATP released from mechanically stimulated astrocytes, in mixed glial cocultures. Astrocyte-derived ATP induced in nearby microglia the formation and the shedding of membrane vesicles. Vesicle formation was inhibited by the ATP-degrading enzyme apyrase or by P2X7R antagonists. Isolation of shed vesicles, followed by IL-1β evaluation by a specific ELISA revealed the presence of the cytokine inside the vesicular organelles and its subsequent efflux into the extracellular medium. IL-1β efflux from shed vesicles was enhanced by ATP stimulation and inhibited by pretreatment with the P2X7 antagonist oxidized ATP, thus indicating a crucial involvement of the pore-forming P2X7R in the release of the cytokine. Our data identify astrocyte-derived ATP as the endogenous factor responsible for microvesicle shedding in microglia and reveal the mechanisms by which astrocyte-derived ATP triggers IL-1β release from these cells.
Long-Term Exposure of the HT-29 Human Intestinal Epithelial Cell Line to TNF Causes Sustained Up-Regulation of the Polymeric Ig Receptor and Proinflammatory Genes through Transcriptional and Posttranscriptional Mechanisms
Authors: Bruno Maria E. C. , Kaetzel Charlotte S.
Published: April 2014

Transport of IgA Abs across intestinal epithelial cells into gut secretions is mediated by the polymeric Ig receptor (pIgR). The cytokine TNF plays a central role in initiating and amplifying inflammatory reactions, and is implicated in the pathogenesis of inflammatory bowel diseases. Acute exposure of intestinal epithelial cell lines to TNF has been shown to up-regulate transcription of genes encoding pIgR and a number of proinflammatory factors, but the effects of chronic exposure to TNF have not been studied. We found that exposure of HT-29 human colon carcinoma cells to TNF for up to 20 days reduced the rate of cell proliferation, but did not cause gross morphological changes. Expression of mRNA encoding pIgR and several proinflammatory genes increased acutely, and then diminished but remained elevated above control levels throughout the experiment. Changes in gene expression were paralleled by increased expression of the transcription factors IFN regulatory factor-1 and the RelB subunit of NF-κB. HT-29 cells activated the endogenous TNF gene in response to TNF treatment, but the level of TNF production was insufficient to maintain pIgR and proinflammatory gene expression after withdrawal of exogenous TNF. Chronic exposure to TNF caused a marked increase in pIgR mRNA stability and a small but significant decrease in TNF mRNA stability, but no change in the half-lives of IL-8, c-Myc, and GAPDH. In summary, we observed different effects of acute vs chronic exposure to TNF on gene expression, and found evidence for transcriptional and posttranscriptional regulation of expression of the pIgR.
Cell-Based Immunotherapy with Suppressor CD8+ T Cells in Rheumatoid Arthritis
Authors: Davila Eduardo , Kang Young Mo , Park Yong Wook , Sawai Hirokazu , He Xiaowen , Pryshchep Sergey , Goronzy Jörg J. , Weyand Cornelia M.
Published: April 2014

The chronic persistence of rheumatoid synovitis, an inflammation driven by activated T cells, macrophages, and fibroblasts causing irreversible joint damage, suggests a failure in physiologic mechanisms that down-regulate and terminate chronic immune responses. In vitro CD8+CD28−CD56+ T cells tolerize APCs, prevent the priming of naive CD4+ T cells, and suppress memory CD4+ T cell responses. Therefore, we generated CD8+CD28−CD56+ T cell clones from synovial tissues, expanded them in vitro, and adoptively transferred them into NOD-SCID mice engrafted with synovial tissues from patients with rheumatoid arthritis. Adoptively transferred CD8+CD28−CD56+ T cells displayed strong anti-inflammatory activity. They inhibited production of IFN-γ, TNF-α, and chemokines in autologous and HLA class I-matched heterologous synovitis. Down-regulation of costimulatory ligands CD80 and CD86 on synovial fibroblasts was identified as one mechanism of immunosuppression. We propose that rheumatoid synovitis can be suppressed by cell-based immunotherapy with immunoregulatory CD8+ T cells.
Interference with the IL-1-Signaling Pathway Improves the Toxicity Profile of Systemically Applied Adenovirus Vectors
Authors: Shayakhmetov Dmitry M. , Li Zong-Yi , Ni Shaoheng , Lieber André
Published: April 2014

The safety of gene therapy vectors is a major concern when novel viral or nonviral therapeutics are proposed for applications in humans. Adenovirus (Ad) vectors have been extensively used as efficient gene delivery vehicles in vitro over the last two decades. However, upon i.v. application, they elicit robust innate and inflammatory responses that may be fatal for the host. To date, the primary cytokines and chemokines involved in the initiation of these host responses remain illusive. In this study, we demonstrate that IL-1 is a major mediator involved in the initiation of immediate host responses toward i.v. applied Ad vectors. Using mice in which IL-1 signaling was genetically eliminated (IL-1RI-KO), or wild-type animals for which signaling was blocked by anti-IL-1 Abs, we found that i.v. applied Ad vectors elicited dramatically reduced acute inflammatory responses when compared with control animals. Importantly, the efficiency of Ad gene transfer in vivo was not significantly affected by interfering with IL-1 signaling. Using an in situ hybridization technique, we found that hepatocytes and Kupffer cells trigger IL-1 transcription in liver tissue after i.v. Ad vector administration. We also found that expression of the MIP-2 chemokine gene (which is responsible for recruitment of neutrophils to the liver) depends on IL-1 activation. Our data indicate that immediate innate and inflammatory host responses toward i.v. applied Ad vectors can be pharmacologically controlled through interference with IL-1 signaling pathways.
Proteinase-Activated Receptor-2 Induction by Neuroinflammation Prevents Neuronal Death during HIV Infection
Authors: Noorbakhsh Farshid , Vergnolle Nathalie , McArthur Justin C. , Silva Claudia , Vodjgani Mohammed , Andrade-Gordon Patricia , Hollenberg Morley D. , Power Christopher
Published: April 2014

Proteinase-activated receptors (PARs), a newly discovered subgroup of G-protein coupled receptors, are widely expressed by neural cells, but their roles in the nervous system remain uncertain. In this study, we report that PAR-2 was up-regulated on neurons in conjunction with neuroinflammation in brain tissue from patients with HIV-1-associated dementia. The inflammatory cytokines TNF-α and IL-1β were also increased in HIV-1-associated dementia brains compared with patients without dementia (p < 0.05), but these same cytokines induced PAR-2 expression on neurons. Enhanced PAR-2 expression and subsequent activation prevented neuronal cell death and induction of the tumor suppressor, p53, caused by the HIV-encoded protein, Tat (p < 0.01). Intrastriatal implantation of a PAR-2 peptide agonist also inhibited Tat-induced neurotoxicity in a mouse model of HIV neuropathogenesis (p < 0.05). Moreover, PAR-2 null animals showed more severe neuroinflammation and neuronal loss caused by Tat neurotoxicity (p < 0.05). TNF-α protected wild-type neurons from Tat-related neurotoxicity, but in PAR-2-deficient neurons, the same concentrations of TNF-α were cytotoxic (p < 0.001). Thus, neuroinflammation can exert protective effects by which it induces PAR-2 expression with the ensuing abrogation of neuronal death.
Transglutaminase Type II Is a Key Element in the Regulation of the Anti-Inflammatory Response Elicited by Apoptotic Cell Engulfment
Authors: Falasca Laura , Iadevaia Valentina , Ciccosanti Fabiola , Melino Gennaro , Serafino Annalucia , Piacentini Mauro
Published: April 2014

A key feature of the macrophage-dependent clearance of apoptotic cells is the down-regulation of proinflammatory cytokines. Deficiency in the phagocytosis of apoptotic cells is often associated with the development of inflammatory reactions, resulting in chronic inflammatory and autoimmune diseases. The molecular mechanisms that regulate the engulfment process and particularly the immunomodulatory factors involved are still largely unknown in mammals. We have previously reported that the ablation of transglutaminase type II (TG2) in mice results in the defective clearance of apoptotic cells associated with the development of splenomegaly, autoantibodies, and glomerulonephritis. In this study we have investigated the mechanisms at the basis of the development of inflammation/autoimmunity associated with the defective clearance of apoptotic cells characterizing TG2 knockout mice. To this aim we compared the macrophage response to apoptotic cell exposure in wild-type vs TG2-null mice. We demonstrated that the lack of TG2 results in an impaired capacity of macrophages to engulf, but not to bind, apoptotic cells, which is paralleled by an abnormal inflammatory response both in vivo and in vitro. We have identified a differential response in the release of several cytokines in TG2−/− vs wild-type mice. Particularly relevant is the finding that both TGF-β and IL-12 regulations were significantly altered in the absence of TG2. These results help explain the autoimmune phenotype developed by these mice and suggest that TG2 is a key regulatory element of the anti-inflammatory features of apoptosis.
Proteolytic Activation of Alternative CCR1 Ligands in Inflammation
Authors: Berahovich Robert D. , Miao Zhenhua , Wang Yu , Premack Brett , Howard Maureen C. , Schall Thomas J.
Published: April 2014

Although chemokines CCL3/MIP-1α and CCL5/RANTES are considered to be primary CCR1 ligands in inflammatory responses, alternative CCR1 ligands have also been described. Indeed, four such chemokines, CCL6/C10/MIP-related protein-1, CCL9/MIP-1γ/MIP-related protein-2, CCL15/MIP-1δ/hemofiltrate CC chemokine-2/leukotactin-1, and CCL23/CKβ8/myeloid progenitor inhibitory factor-1, are unique in possessing a separately encoded N-terminal domain of 16–20 residues and two additional precisely positioned cysteines that form a third disulfide bridge. In vitro, these four chemokines are weak CCR1 agonists, but potency can be increased up to 1000-fold by engineered or expression-associated N-terminal truncations. We examined the ability of proinflammatory proteases, human cell supernatants, or physiological fluids to perform N-terminal truncations of these chemokines and thereby activate their functions. Remarkably, most of the proteases and fluids removed the N-terminal domains from all four chemokines, but were relatively unable to cleave the truncated forms further. The truncated chemokines exhibited up to 1000-fold increases in CCR1-mediated signaling and chemotaxis assays in vitro. In addition, N-terminally truncated CCL15/MIP-1δ and CCL23/CKβ8, but not CCL3/MIP-1α or CCL5/RANTES, were detected at relatively high levels in synovial fluids from rheumatoid arthritis patients. These data suggest that alternative CCR1 ligands are converted into potent chemoattractants by proteases released during inflammatory responses in vivo.
Effects of Leflunomide on Hyaluronan Synthases (HAS): NF-κB-Independent Suppression of IL-1-Induced HAS1 Transcription by Leflunomide
Authors: Stuhlmeier Karl M.
Published: April 2014

Despite evidence that points to unfettered hyaluronic acid (HA) production as a culprit in the progression of rheumatic disorders, little is known about differences in regulation and biological functions of the three hyaluronan synthase (HAS) genes. Testing the effects of drugs with proven anti-inflammatory effects could help to clarify biological functions of these genes. In this study, we demonstrate that leflunomide suppresses HA release in fibroblast-like synoviocytes (FLS) in a dose-dependent manner. We further demonstrate that leflunomide suppresses HA synthase activity, as determined by 14C-glucuronic acid incorporation assays. Additional experiments revealed that in FLS, leflunomide specifically blocked the induction of HAS1. HAS2 and HAS3, genes that are, in contrast to HAS1, constitutively expressed in FLS, are not significantly affected. Leflunomide can function as a NF-κB inhibitor. However, EMSA experiments demonstrate that at the concentrations used, leflunomide neither interferes with IL-1β- nor with PMA-induced NF-κB translocation. Furthermore, reconstituting the pyrimidine synthase pathway did not lead to the restoration of IL-1β-induced HAS1 activation. More importantly, two tyrosine kinase inhibitors mimicked the effect of leflunomide in that both blocked IL-1β-induced HAS1 activation without affecting HAS2 or HAS3. These data point at HAS1 activation as the possible cause for unfettered HA production in rheumatoid arthritis and might explain, at least in part, the beneficial effects of leflunomide treatment. These findings also support the concept that IL-1β-induced HAS1 activation depends on the activation of tyrosine kinases, and indicate that leflunomide blocks HA release by suppressing tyrosine kinases rather than through inhibition of NF-κB translocation.
Identification of a Novel Blocker of IκBα Kinase That Enhances Cellular Apoptosis and Inhibits Cellular Invasion through Suppression of NF-κB-Regulated Gene Products
Authors: Ichikawa Haruyo , Takada Yasunari , Murakami Akira , Aggarwal Bharat B.
Published: April 2014

1′-Acetoxychavicol acetate (ACA), extracted from rhizomes of the commonly used ethno-medicinal plant Languas galanga, has been found to suppress chemical- and virus-induced tumor initiation and promotion through a poorly understood mechanism. Because several genes that regulate cellular proliferation, carcinogenesis, metastasis, and survival are regulated by activation of the transcription factor NF-κB, we postulated that ACA might mediate its activity through modulation of NF-κB activation. For this report, we investigated the effect of ACA on NF-κB and NF-κB-regulated gene expression activated by various carcinogens. We found that ACA suppressed NF-κB activation induced by a wide variety of inflammatory and carcinogenic agents, including TNF, IL-1β, PMA, LPS, H2O2, doxorubicin, and cigarette smoke condensate. Suppression was not cell type specific, because both inducible and constitutive NF-κB activations were blocked by ACA. ACA did not interfere with the binding of NF-κB to the DNA, but, rather, inhibited IκBα kinase activation, IκBα phosphorylation, IκBα degradation, p65 phosphorylation, and subsequent p65 nuclear translocation. ACA also inhibited NF-κB-dependent reporter gene expression activated by TNF, TNFR1, TNFR-associated death domain protein, TNFR-associated factor-2, and IκBα kinase, but not that activated by p65. Consequently, ACA suppressed the expression of TNF-induced NF-κB-regulated proliferative (e.g., cyclin D1 and c-Myc), antiapoptotic (survivin, inhibitor of apoptosis protein-1 (IAP1), IAP2, X-chromosome-linked IAP, Bcl-2, Bcl-xL, Bfl-1/A1, and FLIP), and metastatic (cyclooxygenase-2, ICAM-1, vascular endothelial growth factor, and matrix metalloprotease-9) gene products. ACA also enhanced the apoptosis induced by TNF and chemotherapeutic agents and suppressed invasion. Overall, our results indicate that ACA inhibits activation of NF-κB and NF-κB-regulated gene expression, which may explain the ability of ACA to enhance apoptosis and inhibit invasion.
Cross Talk between MyD88 and Focal Adhesion Kinase Pathways
Authors: Zeisel Mirjam B. , Druet Vanessa A. , Sibilia Jean , Klein Jean-Paul , Quesniaux Valérie , Wachsmann Dominique
Published: April 2014

Focal adhesion kinase (FAK) is a nonreceptor protein tyrosine kinase involved in signaling downstream of integrins, linking bacterial detection, cell entry, and initiation of proinflammatory response through MAPKs and NF-κB activation. In this study, using protein I/II from Streptococcus mutans as a model activator of FAK, we investigated the potential link between FAK and TLR pathways. Using macrophages from TLR- or MyD88-deficient mice, we report that MyD88 plays a major role in FAK-dependent protein I/II-induced cytokine release. However, response to protein I/II stimulation was independent of TLR4, TLR2, and TLR6. The data suggest that there is a cross talk between FAK and MyD88 signaling pathways. Moreover, MyD88-dependent, LPS-induced IL-6 secretion by human and murine fibroblasts required the presence of FAK, confirming that MyD88 and FAK pathways are interlinked.
Tolerogenic Semimature Dendritic Cells Suppress Experimental Autoimmune Thyroiditis by Activation of Thyroglobulin-Specific CD4+CD25+ T Cells
Authors: Verginis Panayotis , Li Haiyan S. , Carayanniotis George
Published: April 2014

Ex vivo treatment of bone marrow-derived dendritic cells (DCs) with TNF-α has been previously shown to induce partial maturation of DCs that are able to suppress autoimmunity. In this study, we demonstrate that i.v. administration of TNF-α-treated, semimature DCs pulsed with thyrogloblin (Tg), but not with OVA Ag, inhibits the subsequent development of Tg-induced experimental autoimmune thyroiditis (EAT) in CBA/J mice. This protocol activates CD4+CD25+ T cells in vivo, which secrete IL-10 upon specific recognition of Tg in vitro and express regulatory T cell (Treg)-associated markers such as glucocorticoid-induced TNFR, CTLA-4, and Foxp3. These CD4+CD25+ Treg cells suppressed the proliferation and cytokine release of Tg-specific, CD4+CD25− effector cells in vitro, in an IL-10-independent, cell contact-dependent manner. Prior adoptive transfer of the same CD4+CD25+ Treg cells into CBA/J hosts suppressed Tg-induced EAT. These results demonstrate that the tolerogenic potential of Tg-pulsed, semimature DCs in EAT is likely to be mediated through the selective activation of Tg-specific CD4+CD25+ Treg cells and provide new insights for the study of Ag-specific immunoregulation of autoimmune diseases.
Cutting Edge: IL-10-Independent STAT3 Activation byToxoplasma gondiiMediates Suppression of IL-12 and TNF-α in Host Macrophages
Authors: Butcher Barbara A. , Kim Leesun , Panopoulos Athanasia D. , Watowich Stephanie S. , Murray Peter J. , Denkers Eric Y.
Published: April 2014

Infection of mouse macrophages by Toxoplasma gondii renders the cells resistant to proinflammatory effects of LPS triggering. In this study, we show that cell invasion is accompanied by rapid and sustained activation of host STAT3. Activation of STAT3 did not occur with soluble T. gondii extracts or heat-killed tachyzoites, demonstrating a requirement for live parasites. Parasite-induced STAT3 phosphorylation and suppression of LPS-triggered TNF-α and IL-12 was intact in IL-10-deficient macrophages, ruling out a role for this anti-inflammatory cytokine in the suppressive effects of T. gondii. Most importantly, Toxoplasma could not effectively suppress LPS-triggered TNF-α and IL-12 synthesis in STAT3-deficient macrophages. These results demonstrate that T. gondii exploits host STAT3 to prevent LPS-triggered IL-12 and TNF-α production, revealing for the first time a molecular mechanism underlying the parasite’s suppressive effect on macrophage proinflammatory cytokine production.
Cutting Edge: Signaling Lymphocytic Activation Molecule-Associated Protein Controls NKT Cell Functions
Authors: Chung Brian , Aoukaty Ala , Dutz Jan , Terhorst Cox , Tan Rusung
Published: April 2014

X-linked lymphoproliferative disease (XLP) is a fatal immunological disorder that typically manifests following EBV infection. XLP patients exhibit a number of immune defects including abnormal T, B, and NK lymphocyte function. These defects have been attributed to mutations of Src homology 2 domain-containing gene 1A (SH2D1A), the gene encoding signaling lymphocytic activation molecule-associated protein (SAP), an intracellular adaptor molecule expressed in lymphocytes. We have observed that SAP knockout (SAPKO) mice and humans with XLP have a complete lack of CD1d-restricted NKT cells. As expected, SAPKO mice injected with the NKT cell agonist, α-galactosylceramide failed to generate NKT cell IFN-γ or IL-4. Furthermore, in contrast to wild-type littermates, SAPKO mice coinjected with OVA and α-galactosylceramide failed to mount OVA-specific CTL responses. These data suggest that an absence of NKT cells may underlie part of the immune dysregulation seen in SAPKO mice and in XLP patients.
Cutting Edge: Recent Immune Status Determines the Source of Antigens That Drive Homeostatic T Cell Expansion
Authors: Kieper William C. , Troy Amy , Burghardt J. Theodore , Ramsey Chris , Lee Joon Youb , Jiang Han-Qing , Dummer Wolfgang , Shen Hao , Cebra John J. , Surh Charles D.
Published: April 2014

Homeostatic proliferation of naive T cells transferred to T cell-deficient syngeneic mice is driven by low-affinity self-MHC/peptide ligands and the cytokine IL-7. In addition to homeostatic proliferation, a subset of naive T cells undergoes massive proliferation in chronically immunodeficient hosts, but not in irradiated normal hosts. Such rapid T cell proliferation occurs largely independent of homeostatic factors, because it was apparent in the absence of IL-7 and in T cell-sufficient hosts devoid of functional T cell immunity. Strikingly, immunodeficient mice raised under germfree conditions supported only slow homeostatic proliferation, but not the marked T cell proliferation observed in conventionally raised immunodeficient mice. Thus, polyclonal naive T cell expansion in T cell-deficient hosts can be driven predominantly by either self-Ags or foreign Ags depending on the host’s previous state of T cell immunocompetency.
Cutting Edge: Stat5 Mediates the IL-7-Induced Accessibility of a Representative D-Distal VH Gene
Authors: Stanton Michelle L. , Brodeur Peter H.
Published: April 2014

During B cell development, discrete domains within the Igh locus are activated independently for recombination. The D-distal VH genes are uniquely dependent on IL-7R signaling, which is thought to establish local chromatin accessibility through an unknown mechanism. To dissect this mechanism, we used a murine B cell line that responds to IL-7 by specifically inducing accessibility of a representative D-distal gene (A1) but not a D-proximal gene (V11). We demonstrate that IL-7-activated Stat5 is recruited rapidly to the A1 gene, with a concomitant increase in germline transcription and H4 acetylation. Furthermore, retroviral transduction of dominant negative or constitutively active Stat5 demonstrated that Stat5 activation is both necessary and sufficient for the IL-7-induced A1 germline transcription. Lastly, as with all known Stat5 target genes, A1 germline transcription requires a deacetylase activity. These results demonstrate that in response to IL-7 signaling, Stat5 is recruited to the D-distal A1 gene and induces accessibility.
Cutting Edge: Novel Role of Lipoxygenases in the Inflammatory Response: Promotion of TNF mRNA Decay by 15-Hydroperoxyeicosatetraenoic Acid in a Monocytic Cell Line
Authors: Ferrante Judith V. , Ferrante Antonio
Published: April 2014

The metabolism of arachidonic acid via the lipoxygenase and cyclooxygenase pathways generates metabolites that regulate the inflammatory response. Although products of lipoxygenase are classically proinflammatory, recently it has been demonstrated that lipoxins, 15-hydroperoxyeicosatetraenoic acid (15-HPETE) and 15-hydroxyeicosatetraenoic acid exhibit anti-inflammatory activity. We now demonstrate for the first time that 15-HPETE regulates the production of the proinflammatory cytokine TNF posttranscriptionally by promoting degradation of LPS-induced TNFmRNA in a human monocytic cell line, Mono Mac 6. 15-HPETE causes a significant increase in the rate of TNF but not G3PDHmRNA degradation in the presence of the transcription inhibitor, actinomycin D. The decay of TNFmRNA is accelerated 1.7-fold, and its half-life is decreased by 57%. In view of its chemical and physical properties, we propose that 15-HPETE may function by destabilizing TNFmRNA by interaction with a trans-activating protein bound to the AU-rich element of TNFmRNA.
CD4− Plasmacytoid Dendritic Cells (pDCs) Migrate in Lymph Nodes by CpG Inoculation and Represent a Potent Functional Subset of pDCs
Authors: Yang Guo-Xiang , Lian Zhe-Xiong , Kikuchi Kentaro , Liu Yong-Jun , Ansari Aftab A. , Ikehara Susumu , Gershwin M. Eric
Published: April 2014

We have recently identified two groups of plasmacytoid dendritic cells (pDCs) isolated from murine liver based on the expression of CD4 and other cell surface markers uniquely expressed by pDCs. Herein, we describe the identification of both CD4+ and CD4− pDCs that clearly exist in lymph nodes (LNs), spleen, liver, thymus, bone marrow, and lung. Normally, CD4+ pDCs are enriched in LNs. However, after in vivo systemic injection with bacterial CpG, a larger number of CD4− pDCs are recruited to the LNs and local inoculation by CpG drives CD4− pDCs migrating into local sentinel LNs, suggesting that CD4− pDCs are the main subpopulation migrating to the peripheral LNs. Furthermore, although both freshly isolated CD4+ pDCs and CD4− pDCs appear as an immature plasmacytoid cell and develop into a DC morphology following activation, the two subsets have strikingly different immune features, including differences in the production pattern of cytokines stimulated with CpG and in T cell activation.
Mannose-Binding Lectin-Deficient Mice Display Defective Apoptotic Cell Clearance but No Autoimmune Phenotype
Authors: Stuart Lynda M. , Takahashi Kazue , Shi Lei , Savill John , Ezekowitz R. Alan B.
Published: April 2014

Mannose-binding lectin (MBL) is a circulating serum protein that is sequestered to sites of inflammation and infection. MBL is a member of the collectin family with structural similarities to the lung collectins and functional similarities to C1q. Both MBL and C1q activate complement; C1q activates the classical pathway and MBL the lectin pathway. Here we demonstrate that MBL binds apoptotic cells in vitro and confirm a role for MBL in clearance of apoptotic cells in vivo. Despite MBL null mice demonstrating defective apoptotic cell clearance they did not develop spontaneous autoimmunity, lymphoproliferation, or germinal center expansion although increased numbers of peritoneal B1 cells were detected. These data demonstrate an important in vivo role for MBL in clearance of dying cells and adds the MBL null animals to the few animals with demonstrable in vivo apoptotic cell clearance defects. Moreover, it demonstrates that failure of apoptotic cell clearance can be dissociated from autoimmunity.
Very Low-Dose Tolerance with Nucleosomal Peptides Controls Lupus and Induces Potent Regulatory T Cell Subsets
Authors: Kang Hee-Kap , Michaels Marissa A. , Berner Beate R. , Datta Syamal K.
Published: April 2014

We induced very low-dose tolerance by injecting lupus prone (SWR × NZB)F1 (SNF1) mice with 1 μg nucleosomal histone peptide autoepitopes s.c. every 2 wk. The subnanomolar peptide therapy diminished autoantibody levels and prolonged life span by delaying nephritis, especially by reducing inflammatory cell reaction and infiltration in kidneys. H471–94 was the most effective autoepitope. Low-dose tolerance therapy induced CD8+, as well as CD4+CD25+ regulatory T (Treg) cell subsets containing autoantigen-specific cells. These adaptive Treg cells suppressed IFN-γ responses of pathogenic lupus T cells to nucleosomal epitopes at up to a 1:100 ratio and reduced autoantibody production up to 90–100% by inhibiting nucleosome-stimulated T cell help to nuclear autoantigen-specific B cells. Both CD4+CD25+ and CD8+ Treg cells produced and required TGF-β1 for immunosuppression, and were effective in suppressing lupus autoimmunity upon adoptive transfer in vivo. The CD4+CD25+ T cells were partially cell contact dependent, but CD8+ T cells were contact independent. Thus, low-dose tolerance with highly conserved histone autoepitopes repairs a regulatory defect in systemic lupus erythematosus by generating long-lasting, TGF-β-producing Treg cells, without causing allergic/anaphylactic reactions or generalized immunosuppression.
Protein Conformation Significantly Influences Immune Responses to Prion Protein
Authors: Khalili-Shirazi Azadeh , Quaratino Sonia , Londei Marco , Summers Linda , Tayebi Mourad , Clarke Anthony R. , Hawke Simon H. , Jackson Graham S. , Collinge John
Published: April 2014

In prion diseases, such as variant Creutzfeldt-Jakob disease normal cellular prion protein (PrPC), a largely α-helical structure is converted to an abnormal conformational isoform (PrPSc) that shows an increase in β-sheet content. Similarly, the recombinant form of PrPC (rα-PrP) can be converted to a conformation dominated by β-sheet (rβ-PrP) by reduction and mild acidification in vitro, a process that may mimic in vivo conversion following PrPC internalization during recycling. Despite PrPSc accumulation and prion propagation in the lymphoreticular system before detectable neuroinvasion, no Ab response to PrP has been detected, probably due to immune tolerance. To investigate how the immune system may respond to α- and β-PrP, we immunized Prnp0/0 mice that are not tolerant of PrP with rα-PrP and rβ-PrP. In this study, we show that although T cells stimulated by these differently folded conformers PrP recognize similar immunodominant epitopes (residues 111–130 and 191–210) the cytokine profile in response to rα- and rβ-PrP was different. Challenge with rα-PrP elicited a strong response of IL-5 and IL-10, whereas rβ-PrP led to an early increased production of IFN-γ. In addition, immunization with rα-PrP led to production of predominantly IgG1 isotype Ab in the sera, whereas after immunization with rβ-PrP, IgG2b was significantly produced. Thus, both humoral and cellular responses to these differently folded isoforms of the same protein are different, indicating a possible involvement of Th1 and Th2 pathway activation. These differences may be exploitable diagnostically and therapeutically for prion diseases, such as variant Creutzfeldt-Jakob disease.
Coligation of the B Cell Receptor with Complement Receptor Type 2 (CR2/CD21) Using Its Natural Ligand C3dg: Activation without Engagement of an Inhibitory Signaling Pathway
Authors: Lyubchenko Taras , Dal Porto Joe , Cambier John C. , Holers V. Michael
Published: April 2014

C3dg is a cleavage product of the C3 component of complement that can facilitate the coligation of the complement receptor 2 (CR2/CD21) with the BCR via C3dg/Ag complexes. This interaction can greatly amplify BCR-mediated signaling events and acts to lower the threshold for B cell activation. Although previous studies have used anti-CR2 Abs or used chimeric Ags in the context of BCR transgenic mice as surrogate C3d-containing ligands, we have used a physiological form of C3d to study signaling in B cells from wild-type C57BL/6 mice. We find that while CR2-enhanced BCR signaling causes intracellular Ca2+ mobilization and total pTyr phosphorylation of an intensity comparable to optimal BCR ligation using anti-IgM Abs, it does so with limited activation of inhibitory effectors (such as CD22, Src homology region 2 domain containing phosphatase 1, and SHIP-1) and without substantial receptor cross-linking. In summary, we demonstrate that CR2-enhanced BCR signaling may proceed not only through the previously described amplification of positive signaling pathways, but is potentially augmented by a lack of normal inhibitory/feedback signaling.
Exacerbation of Granuloma Formation in IL-1 Receptor Antagonist-Deficient Mice with Impaired Dendritic Cell Maturation Associated with Th2 Cytokine Production
Authors: Iizasa Hisashi , Yoneyama Hiroyuki , Mukaida Naofumi , Katakoka Yuki , Naito Makoto , Yoshida Nobuaki , Nakashima Emi , Matsushima Kouji
Published: April 2014

Dendritic cell (DC) maturation at the site of inflammation and migration into draining lymph nodes is fundamental to initiate Ag-specific immune responses. Although several proinflammatory cytokines, including IL-1, are known to promote DC maturation in vitro, their contributions to DC activation and migration within peripheral inflamed tissue compartments are not yet fully understood. We show here that endogenous IL-1 receptor antagonist (IL-1ra) controls the activation state of liver-recruited DCs and their migration in a Propionibacterium acnes-induced murine granulomatous liver disease model. After P. acnes treatment, formation of portal tract-associated lymphoid tissue was conversely impaired in IL-1ra-deficient mice. IL-1ra-deficient mice developed hepatic granulomas within 3 days after P. acnes administration and showed a more pronounced granuloma formation than wild-type mice. Although sinusoidal granulomas contained numerous CD11c+ DCs at day 7, expressions of CCR7, IL-12p40 by these DCs were dramatically decreased in IL-1ra-deficient mice, suggesting aberrant DC maturation and sinusoid portal migration in the absence of endogenous IL-1ra. This was accompanied with enhanced intrahepatic Th2 cytokine production and severe hepatocellular damage. Thus, hepatocyte-derived IL-1ra may control optimal activation and migration of inflammatory DCs within the liver and thereby determine the local immune responses in granulomatous liver disease.
Δ-9-Tetrahydrocannabinol Enhances Breast Cancer Growth and Metastasis by Suppression of the Antitumor Immune Response
Authors: McKallip Robert J. , Nagarkatti Mitzi , Nagarkatti Prakash S.
Published: April 2014

In the current study, we tested the central hypothesis that exposure to Δ-9-tetrahydrocannabinol (Δ9-THC), the major psychoactive component in marijuana, can lead to enhanced growth of tumors that express low to undetectable levels of cannabinoid receptors by specifically suppressing the antitumor immune response. We demonstrated that the human breast cancer cell lines MCF-7 and MDA-MB-231 and the mouse mammary carcinoma 4T1 express low to undetectable levels of cannabinoid receptors, CB1 and CB2, and that these cells are resistant to Δ9-THC-induced cytotoxicity. Furthermore, exposure of mice to Δ9-THC led to significantly elevated 4T1 tumor growth and metastasis due to inhibition of the specific antitumor immune response in vivo. The suppression of the antitumor immune response was mediated primarily through CB2 as opposed to CB1. Furthermore, exposure to Δ9-THC led to increased production of IL-4 and IL-10, suggesting that Δ9-THC exposure may specifically suppress the cell-mediated Th1 response by enhancing Th2-associated cytokines. This possibility was further supported by microarray data demonstrating the up-regulation of a number of Th2-related genes and the down-regulation of a number of Th1-related genes following exposure to Δ9-THC. Finally, injection of anti-IL-4 and anti-IL-10 mAbs led to a partial reversal of the Δ9-THC-induced suppression of the immune response to 4T1. Such findings suggest that marijuana exposure either recreationally or medicinally may increase the susceptibility to and/or incidence of breast cancer as well as other cancers that do not express cannabinoid receptors and are resistant to Δ9-THC-induced apoptosis.
CD38 Controls ADP-Ribosyltransferase-2-Catalyzed ADP-Ribosylation of T Cell Surface Proteins
Authors: Krebs Christian , Adriouch Sahil , Braasch Fenja , Koestner Wolfgang , Leiter Edward H. , Seman Michel , Lund Frances E. , Oppenheimer Norman , Haag Friedrich , Koch-Nolte Friedrich
Published: April 2014

ADP-ribosyltransferase-2 (ART2), a GPI-anchored, toxin-related ADP-ribosylating ectoenzyme, is prominently expressed by murine T cells but not by B cells. Upon exposure of T cells to NAD, the substrate for ADP-ribosylation, ART2 catalyzes ADP-ribosylation of the P2X7 purinoceptor and other functionally important cell surface proteins. This in turn activates P2X7 and induces exposure of phosphatidylserine and shedding of CD62L. CD38, a potent ecto-NAD-glycohydrolase, is strongly expressed by most B cells but only weakly by T cells. Following incubation with NAD, CD38-deficient splenocytes exhibited lower NAD-glycohydrolase activity and stronger ADP-ribosylation of cell surface proteins than their wild-type counterparts. Depletion of CD38high cells from wild-type splenocytes resulted in stronger ADP-ribosylation on the remaining cells. Similarly, treatment of total splenocytes with the CD38 inhibitor nicotinamide 2′-deoxy-2′-fluoroarabinoside adenine dinucleotide increased the level of cell surface ADP-ribosylation. Furthermore, the majority of T cells isolated from CD38-deficient mice “spontaneously” exposed phosphatidylserine and lacked CD62L, most likely reflecting previous encounter with ecto-NAD. Our findings support the notion that ecto-NAD functions as a signaling molecule following its release from cells by lytic or nonlytic mechanisms. ART2 can sense and translate the local concentration of ecto-NAD into corresponding levels of ADP-ribosylated cell surface proteins, whereas CD38 controls the level of cell surface protein ADP-ribosylation by limiting the substrate availability for ART2.
Identification of Stimulating and Inhibitory Epitopes within the Heat Shock Protein 70 Molecule That Modulate Cytokine Production and Maturation of Dendritic Cells
Authors: Wang Yufei , Whittall Trevor , McGowan Edward , Younson Justine , Kelly Charles , Bergmeier Lesley A. , Singh Mahavir , Lehner Thomas
Published: April 2014

The 70-kDa microbial heat shock protein (mHSP70) has a profound effect on the immune system, interacting with the CD40 receptor on DC and monocytes to produce cytokines and chemokines. The mHSP70 also induces maturation of dendritic cells (DC) and thus acts as an alternative ligand to CD40L on T cells. In this investigation, we have identified a cytokine-stimulating epitope (peptide 407–426), by activating DC with overlapping synthetic peptides (20-mers) derived from the sequence of mHSP70. This peptide also significantly enhances maturation of DC stimulated by mHSP70 or CD40L. The epitope is located at the base of the peptide-binding groove of HSP70 and has five critical residues. Furthermore, an inhibitory epitope (p457–496) was identified downstream from the peptide-binding groove that inhibits cytokine production and maturation of DC stimulated by HSP70 or CD40L. The p38 MAP kinase phosphorylation is critical in the alternative CD40-HSP70 pathway and is inhibited by p457–496 but enhanced by p407–426.
Nucleosome, the Main Autoantigen in Systemic Lupus Erythematosus, Induces Direct Dendritic Cell Activation via a MyD88-Independent Pathway: Consequences on Inflammation
Authors: Decker Patrice , Singh-Jasuja Harpreet , Haager Sabine , Kötter Ina , Rammensee Hans-Georg
Published: April 2014

Nucleosome is the major autoantigen in systemic lupus erythematosus. It is found as a circulating complex in the sera of patients and seems to play a key role in disease development. In this study, we show for the first time that physiologic concentrations of purified nucleosomes directly induce in vitro dendritic cell (DC) maturation of mouse bone marrow-derived DC, human monocyte-derived DC (MDDC), and purified human myeloid DC as observed by stimulation of allogenic cells in MLR, cytokine secretion, and CD86 up-regulation. Importantly, nucleosomes act as free complexes without the need for immune complex formation or for the presence of unmethylated CpG DNA motifs, and we thus identified a new mechanism of DC activation by nucleosomes. We have clearly demonstrated that this activation is nucleosome-specific and endotoxin-independent. Particularly, nucleosomes induce MDDC to secrete cytokines known to be detected in high concentrations in the sera of patients. Moreover, activated MDDC secrete IL-8, a neutrophil chemoattractant also detected in patient sera, and thus might favor the inflammation observed in patients. Both normal and lupus MDDC are sensitive to nucleosome-induced activation. Finally, injection of purified nucleosomes to normal mice induces in vivo DC maturation. Altogether, these results strengthen the key role of nucleosomes in systemic lupus erythematosus and might explain how peripheral tolerance is broken in patients.
Amelioration of Established Experimental Autoimmune Encephalomyelitis by an MHC Anchor-Substituted Variant of Proteolipid Protein 139–151
Authors: Margot Carrie D. , Ford Mandy L. , Evavold Brian D.
Published: April 2014

Murine experimental autoimmune encephalomyelitis (EAE) is a CD4+ T cell-mediated autoimmune disorder directed against myelin proteins within the CNS. We propose that variant peptides containing amino acid substitutions at MHC anchor residues will provide a unique means to controlling the polyclonal autoimmune T cell response. In this study, we have identified an MHC variant of proteolipid protein (PLP) 139–151 (145D) that renders PLP139–151-specific T cell lines anergic in vitro, as defined by a significant reduction in proliferation and IL-2 production following challenge with wild-type peptide. In vivo administration of 145D before challenge with PLP139–151 results in a significant reduction in disease severity and incidence. Importantly, we demonstrate the ability of an MHC variant peptide to ameliorate established EAE. An advantage to this treatment is that the MHC variant peptide does not induce an acute hypersensitivity reaction. This is in contrast to previous work in the PLP139–151 model demonstrating that anaphylactic shock resulting in death occurs upon rechallenge with the encephalitogenic peptide. Taken together, these data demonstrate the effectiveness of MHC anchor-substituted peptides in the treatment of EAE and suggest their utility in the treatment of other autoimmune disorders.
Small Rho GTPases Regulate Antigen Presentation in Dendritic Cells
Authors: Shurin Galina V. , Tourkova Irina L. , Chatta Gurkamal S. , Schmidt Gudula , Wei Sheng , Djeu Julie Y. , Shurin Michael R.
Published: April 2014

Dendritic cells (DC) are involved in the regulation of innate and adaptive immunity. However, the molecular mechanisms maintaining DC function remain to be elucidated. In this study, we report on the role of small Rho GTPases: Cdc42, Rac1, and RhoA in the regulation of DC adherence, Ag presentation, migration, chemotaxis, and endocytosis. Murine DC were transfected with vaccinia virus-based constructs, encoding dominant-negative or constitutively active (ca) mutant forms of Rho GTPases. We demonstrate that Cdc42 plays a major role in the regulation of DC adhesion, because caCdc42-transfected DC had significant up-regulation of adhesion to extracellular matrix, which was blocked by the Rho GTPase inhibitor toxin B (ToxB). In contrast, caRho-transfected DC only modestly elevated DC adhesion, and caRac had no effect. Additionally, caCdc42 and caRho increased the ability of DC to present OVA peptide to specific T cells. This effect was abrogated by ToxB. Activation of Cdc42 in DC significantly inhibited spontaneous and chemokine-induced DC migration. Furthermore, uptake of dextran 40 by DC was significantly enhanced by Rho GTPase activators cytotoxic necrotizing factor 1 and PMA, and reduced by ToxB. caCdc42 also increased endocytotic activity of DC, whereas dominant-negative Cdc42 blocked it. Thus, Rho GTPases Cdc42, RhoA, and Rac1 regulate DC functions that are critical for DC-mediated immune responses in vivo.
The Role of Intercellular Adhesion Molecule-1/LFA-1 Interactions in the Generation of Tumor-Specific CD8+ T Cell Responses
Authors: Jenkinson S. Rhiannon , Williams Neil A. , Morgan David J.
Published: April 2014

The activation of naive CD4+ T cells requires both TCR engagement and a second costimulatory signal mediated by the interaction of CD28 with CD80/CD86 expressed on professional APC. However, the situation for naive CD8+ T cells is less clear. Although evidence indicates that induction of CD8+ T cell responses is also dependent on professional APC, the ability of some tumors, which do not express CD80/CD86, to induce CTL suggests that other pathways of costimulation exist for the activation of CD8+ T cells. We examined the ability of tumor cells expressing different levels of a tumor-specific Ag to directly prime CD8+ T cells. We demonstrate that CD8+ T cells are directly activated by tumor cells in a CD80/CD86-CD28 independent manner. In this system, costimulation requires ICAM-1/LFA-1 interaction. This results in the generation of CTL capable of inhibiting tumor growth in vivo, and maintaining long-term survival.
Quantitating Effector and Regulatory T Lymphocytes in Immune Responses by Limiting Dilution Analysis Modeling
Authors: Bonnefoix Thierry , Bonnefoix Philippe , Perron Pascal , Mi Jian-Qing , Ng Wan Fai , Lechler Robert , Bensa Jean-Claude , Cahn Jean-Yves , Leroux Dominique
Published: April 2014

Although there is currently no doubt that regulatory lymphocytes represent a master player in the immune system, a major unresolved problem is the accurate quantitation of these cells among unfractionated cell populations. This difficulty mainly arises because there are no specific immunophenotypic markers that can reliably discriminate between effector and regulatory lymphocytes. To face this problem, we have developed computational models of limiting dilution analyses addressing the question of the accurate estimation of the frequencies of effector and regulatory cells functionally engaged in an immune response. A set of generic equations were provided to form a framework for modeling limiting dilution data, enabling discrimination between qualitatively different models of suppression. These models include either one or two subpopulations of regulatory cells, featured by either low or potent regulatory activity. The potential of this modeling approach was illustrated by the accurate determination of the frequencies of effector and regulatory T lymphocytes in one real limiting dilution experiment of CD4+CD25+ T lymphocytes performed in the context of an allogeneic response in the human system. The crucial advantage of the limiting dilution method over the “static, phenotype-based” method is the dynamic evaluation of effector and regulatory T cell biology through their actual functional activity.