bluuebunny/crossref_metadata_2025 huggingface dataset:
Subversion of Pulmonary Dendritic Cell Function by Paramyxovirus Infections
Authors: Guerrero-Plata Antonieta , Kolli Deepthi , Hong Chao , Casola Antonella , Garofalo Roberto P.
Published: February 2009

Lower respiratory tract infections caused by the paramyxoviruses human metapneumovirus (hMPV) and respiratory syncytial virus (RSV) are characterized by short-lasting virus-specific immunity and often long-term airway morbidity, both of which may be the result of alterations in the Ag-presenting function of the lung which follow these infections. In this study, we investigated whether hMPV and RSV experimental infections alter the phenotype and function of dendritic cell (DC) subsets that are recruited to the lung. Characterization of lung DC trafficking demonstrated a differential recruitment of plasmacytoid DC (pDC), conventional DC (cDC), and IFN-producing killer DC to the lung and draining lymph nodes after hMPV and RSV infection. In vitro infection of lung DC indicated that in pDC, production of IFN-α, TNF-α, and CCL5 was induced only by hMPV, whereas CCL3 and CCL4 were induced by both viruses. In cDC, a similar repertoire of cytokines was induced by hMPV and RSV, except for IFN-β, which was not induced by RSV. The function of lung pDC was altered following hMPV or RSV infection in vivo, as we demonstrated a reduced capacity of lung pDC to produce IFN-α as well as other cytokines including IL-6, TNF-α, CCL2, CCL3, and CCL4 in response to TLR9 stimulation. Moreover, we observed an impaired capacity of cDC from infected mice to present Ag to CD4+ T cells, an effect that lasted beyond the acute phase of infection. Our findings suggest that acute paramyxovirus infections can alter the long-term immune function of pulmonary DC.
Activation of Inflammasomes Requires Intracellular Redistribution of the Apoptotic Speck-Like Protein Containing a Caspase Recruitment Domain
Authors: Bryan Nicole B. , Dorfleutner Andrea , Rojanasakul Yon , Stehlik Christian
Published: February 2009

Activation of caspase 1 is essential for the maturation and release of IL-1β and IL-18 and occurs in multiprotein complexes, referred to as inflammasomes. The apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) is the essential adaptor protein for recruiting pro-caspase 1 into inflammasomes, and consistently gene ablation of ASC abolishes caspase 1 activation and secretion of IL-1β and IL-18. However, distribution of endogenous ASC has not yet been examined in detail. In the present study, we demonstrated that ASC localized primarily to the nucleus in resting human monocytes/macrophages. Upon pathogen infection, ASC rapidly redistributed to the cytosol, followed by assembly of perinuclear aggregates, containing several inflammasome components, including caspase 1 and Nod-like receptors. Prevention of ASC cytosolic redistribution completely abolished pathogen-induced inflammasome activity, which affirmed that cytosolic localization of ASC is essential for inflammasome function. Thus, our study characterized a novel mechanism of inflammasome regulation in host defense.
Transitional B Cells Exhibit a B Cell Receptor-Specific Nuclear Defect in Gene Transcription
Authors: Andrews Sarah F. , Rawlings David J.
Published: February 2009

The signaling programs that enforce negative selection in early transitional (T1) B cells in response to BCR engagement remain poorly defined. We conducted a comprehensive comparison of BCR signaling in T1 vs follicular mature splenic B cells. T1, in contrast to follicular mature B cells, failed to express key NF-κB target genes in response to BCR engagement and exhibited a striking defect in assembly of an active transcriptional complex at the promoter of the survival and proliferative genes A1 and c-Myc. Surprisingly, and contrary to previous models, classical protein kinase C and IκB kinase activation, NF-κB nuclear translocation and DNA binding were intact in T1 B cells. Furthermore, despite a marked reduction in NFAT1 expression, differential NFAT or AP-1 activation cannot explain this transcriptional defect. Our combined findings demonstrate that T1 B cells are programmed for signal- and stage-specific “nuclear nonresponsiveness” upon encounter with self-Ags.
Bone Marrow Monocyte PECAM-1 Deficiency Elicits Increased Osteoclastogenesis Resulting in Trabecular Bone Loss
Authors: Wu Yue , Tworkoski Kathryn , Michaud Michael , Madri Joseph A.
Published: February 2009

In our investigations of the bone marrow (BM) of PECAM-1 null (knockout, KO) mice, we observed that the trabecular bone volume and number of trabeculae were significantly reduced in femural and tibial long bones. Further studies in vitro revealed increased numbers and size of osteoclasts, enhanced bone resorption on dentin substrates, and hypersensitivity to macrophage CSF and receptor activator of NF-κB ligand in BM-derived osteoclast precursor cultures from KO mice. Associations among PECAM-1, Syk, and SHP-1 were found in wild-type BM monocyte derived osteoclast-like cells. The absence of PECAM-1 and SHP-1 interactions in the KO cells leads to the dysregulation of Syk kinases and/or phosphatases, possibly SHP-1. Indeed, KO derived osteoclast-like cells exhibited increased Syk tyrosine phosphorylation levels compared with WT cells. Lastly, WT mice engrafted with marrow from KO kindred showed loss of trabecular bone analogous to KO mice, consistent with increased osteoclastogenesis.
Anti-Inflammatory Role of IL-17 in Experimental Autoimmune Uveitis
Authors: Ke Yan , Liu Ke , Huang Guo-Qiang , Cui Yan , Kaplan Henry J. , Shao Hui , Sun Deming
Published: February 2009

Previous studies have shown that IL-17 is a strong proinflammatory cytokine and that IL-17-producing autoreactive T cells play a major role in the pathogenesis of autoimmune diseases. In a previous study, we showed that injection of experimental autoimmune uveitis-susceptible mice with anti-IL-17 Abs blocked subsequent disease development. To determine whether administration of IL-17 to experimental autoimmune uveitis-susceptible Lewis rats and B10RIII mice injected with disease-inducing peptides enhanced disease susceptibility, we injected the recipient animals with various doses of human rIL-17 (hIL-17). Unexpectedly, the treated animals showed significant amelioration of disease; in addition, both the intensity of the autoreactive response and cytokine production by the autoreactive T cells induced by immunization with uveitogenic peptides were significantly decreased. Our results show that IL-17 has anti-inflammatory activity and that this cytokine can suppress the development of autoimmune disease.
c-Abl Kinase Is Required for β2 Integrin-Mediated Neutrophil Adhesion
Authors: Cui Lingling , Chen Cuixia , Xu Ting , Zhang Juechao , Shang Xin , Luo Jixian , Chen Liang , Ba Xueqing , Zeng Xianlu
Published: February 2009

Integrin regulation in neutrophil adhesion is essential for innate immune response. c-Abl kinase is a nonreceptor tyrosine kinase and is critical for signaling transduction from various receptors in leukocytes. Using neutrophils and dHL-60 (neutrophil-like differentiation of HL-60) cells, we show that c-Abl kinase is activated by β2 integrin engagement and is required for β2 integrin-dependent neutrophil sustained adhesion and spreading. The expression of β2 integrin on neutrophils induced by TNF-α is not affected by c-Abl kinase inhibitor STI571, suggesting that c-Abl kinase is not involved in TNF-α-induced integrin activation. The recruitment of c-Abl kinase to β2 integrin is dependent on talin head domain, which constitutively interacts with β2 integrin cytoplasmic domain. After activated, c-Abl kinase increases the tyrosine phosphorylation of Vav. The SH3 domain of c-Abl kinase is involved in its interaction with talin and Vav. Thus, c-Abl kinase plays an essential role in the activation of Vav induced by β2 integrin ligation and in regulating neutrophil-sustained adhesion and spreading.
Reciprocal Interactions between Commensal Bacteria and γδ Intraepithelial Lymphocytes during Mucosal Injury
Authors: Ismail Anisa S. , Behrendt Cassie L. , Hooper Lora V.
Published: February 2009

The intestinal mucosal surface is in direct contact with a vast beneficial microbiota. The symbiotic nature of this relationship is threatened when the surface epithelium is injured, yet little is known about how mucosal surfaces maintain homeostasis with commensal microbes following damage. γδ Intraepithelial lymphocytes (γδ IEL) reside at the gut epithelial surface, where they stimulate mucosal healing following acute injury. A genome-wide analysis of the γδ IEL response to dextran sulfate sodium-induced colonic damage revealed induction of a complex transcriptional program, including coordinate regulation of cytoprotective, immunomodulatory, and antibacterial factors. Studies in germfree mice demonstrated that commensal microbiota regulate key components of this transcriptional program, thus revealing a dialogue between commensal bacteria and γδ IEL in injured epithelia. Analysis of TCRδ-deficient mice indicated that γδ T cells are essential for controlling mucosal penetration of commensal bacteria immediately following dextran sulfate sodium-induced damage, suggesting that a key function of γδ IEL is to maintain host-microbial homeostasis following acute mucosal injury. Taken together, these findings disclose a reciprocal relationship between γδ T cells and intestinal microbiota that promotes beneficial host-microbial relationships in the intestine.
Induction of IDO by Bacille Calmette-Guérin Is Responsible for Development of Murine Depressive-Like Behavior
Authors: O'Connor Jason C. , Lawson Marcus A. , André Caroline , Briley Eileen M. , Szegedi Sandra S. , Lestage Jacques , Castanon Nathalie , Herkenham Miles , Dantzer Robert , Kelley Keith W.
Published: February 2009

Chronic inflammation activates the tryptophan-degrading enzyme IDO, which is well known to impair T cell proliferation. We have previously established that bacille Calmette-Guérin (BCG), an attenuated form of Mycobacterium bovis, is associated with persistent activation of IDO in the brain and chronic depressive-like behavior, but a causative role has not been established. In these experiments we used both pharmacologic and genetic approaches to test the hypothesis that IDO activation is responsible for the development of chronic depression that follows BCG infection. BCG induced TNF-α, IFN-γ, and IDO mRNA steady-state transcripts in the brain as well as the enzyme 3-hydroxyanthranilic acid oxygenase (3-HAO) that lies downstream of IDO and generates the neuroactive metabolite, quinolinic acid. Behaviors characteristic of depression were apparent 1 wk after BCG infection. Pretreatment with the competitive IDO inhibitor 1-methyltryptophan fully blocked BCG-induced depressive-like behaviors. Importantly, IDO-deficient mice were completely resistant to BCG-induced depressive-like behavior but responded normally to BCG induction of proinflammatory cytokines. These results are the first to prove that the BCG-induced persistent activation of IDO is accompanied by the induction of 3-hydroxyanthranilic acid oxygenase and that IDO is required as an initial step for the subsequent development of chronic depressive-like behavior.
The Essential Role of Single Ig IL-1 Receptor-Related Molecule/Toll IL-1R8 in Regulation of Th2 Immune Response
Authors: Bulek Katarzyna , Swaidani Shadi , Qin Jinzhong , Lu Yi , Gulen Muhammet F. , Herjan Tomasz , Min Booki , Kastelein Robert A. , Aronica Mark , Kosz-Vnenchak Magdalena , Li Xiaoxia
Published: February 2009

A novel cytokine IL-33, an IL-1 family member, signals via ST2 receptor and promotes Th2 responses, through the activation of NF-κB and MAP kinases. Previous studies reported that single Ig IL-1R-related molecule (SIGIRR)/Toll IL-1R8 acts as negative regulator for TLR-IL-1R-mediated signaling. We now found that SIGIRR formed a complex with ST2 upon IL-33 stimulation and specifically inhibited IL-33/ST2-mediated signaling in cell culture model. Furthermore, IL-33-induced Th2 response was enhanced in SIGIRR-deficient mice compared with that in wild-type control mice, suggesting a negative regulatory role of SIGIRR in IL-33/ST2 signaling in vivo. Similar to ST2, SIGIRR was highly expressed in in vitro polarized Th2 cells, but not Th1 cells. SIGIRR-deficient Th2 cells produce higher levels of Th2 cytokines, including IL-5, IL-4, and IL-13, than that in wild-type cells. Moreover, SIGIRR-deficient mice developed stronger Th2 immune response in OVA-challenged asthma model. Taken together, our results suggest that SIGIRR plays an important role in the regulation of Th2 response in vivo, possibly through its impact on IL-33-ST2-mediated signaling.
Rapid Dendritic Cell Mobilization to the Large Intestinal Epithelium Is Associated with Resistance to Trichuris muris Infection
Authors: Cruickshank Sheena M. , Deschoolmeester Matthew L. , Svensson Marcus , Howell Gareth , Bazakou Aikaterini , Logunova Larisa , Little Matthew C. , English Nicholas , Mack Matthias , Grencis Richard K. , Else Kathryn J. , Carding Simon R.
Published: February 2009

The large intestine is a major site of infection and disease, yet little is known about how immunity is initiated within this site and the role of dendritic cells (DCs) in this process. We used the well-established model of Trichuris muris infection to investigate the innate response of colonic DCs in mice that are inherently resistant or susceptible to infection. One day postinfection, there was a significant increase in the number of immature colonic DCs in resistant but not susceptible mice. This increase was sustained at day 7 postinfection in resistant mice when the majority of the DCs were mature. There was no increase in DC numbers in susceptible mice until day 13 postinfection. In resistant mice, most colonic DCs were located in or adjacent to the epithelium postinfection. There were also marked differences in the expression of colonic epithelial chemokines in resistant mice and susceptible mice. Resistant mice had significantly increased levels of epithelium-derived CCL2, CCL3, CCL5, and CCL20 compared with susceptible mice. Furthermore, administering neutralizing CCL5 and CCL20 Abs to resistant mice prevented DC recruitment. This study provides clear evidence of differences in the kinetics of DC responses in hosts inherently resistant and susceptible to infection. DC responses in the colon correlate with resistance to infection. Differences in the production of DC chemotactic chemokines by colonic epithelial cells in response to infection in resistant vs susceptible mice may explain the different kinetics of the DC response.
Acute, but Not Resolved, Influenza A Infection Enhances Susceptibility to House Dust Mite-Induced Allergic Disease
Authors: Al-Garawi Amal A. , Fattouh Ramzi , Walker Tina D. , Jamula Erin B. , Botelho Fernando , Goncharova Susanna , Reed Jennifer , Stampfli Martin R. , O'Byrne Paul M. , Coyle Anthony J. , Jordana Manel
Published: February 2009

The impact of respiratory viral infections on the emergence of the asthmatic phenotype is a subject of intense investigation. Most experimental studies addressing this issue have used the inert Ag OVA with controversial results. We examined the consequences of exposure to a low dose of the common aeroallergen house dust mite (HDM) during the course of an influenza A infection. First, we delineated the kinetics of the immune-inflammatory response in the lung of mice following intranasal infection with influenza A/PR8/34. Our data demonstrate a peak response during the first 10 days, with considerable albeit not complete resolution at day 39 postinfection (p.i.). At day 7 p.i., mice were exposed, intranasally, to HDM for 10 consecutive days. We observed significantly enhanced eosinophilic inflammation, an expansion in Th2 cells, enhanced HDM-specific IgE and IgG1 responses and increased mucous production. Furthermore, lung mononuclear cells produced enhanced IFN-γ and IL-5, unchanged IL-13, and reduced IL-4. These immunologic and structural changes lead to marked lung dysfunction. This allergic phenotype occurs at a time when there is a preferential increase in plasmacytoid dendritic cells over myeloid dendritic cells, activated CD8+ T cells, and increased IFN-γ production, all of which have been proposed to inhibit allergic responses. In contrast, the inflammatory response elicited by HDM was reduced when exposure occurred during the resolution phase (day 40 p.i.). Interestingly, this was not associated with a reduction in sensitization. Thus, the proinflammatory environment established during an acute influenza A infection enhances Th2-polarized immunity to a low dose of HDM and precipitates marked lung dysfunction.
IL-3 Induces Basophil Expansion In Vivo by Directing Granulocyte-Monocyte Progenitors to Differentiate into Basophil Lineage-Restricted Progenitors in the Bone Marrow and by Increasing the Number of Basophil/Mast Cell Progenitors in the Spleen
Authors: Ohmori Keitaro , Luo Yuchun , Jia Yi , Nishida Jun , Wang Zhengqi , Bunting Kevin D. , Wang Demin , Huang Hua
Published: February 2009

Recent work has established important roles for basophils in regulating immune responses. To exert their biological functions, basophils need to be expanded to critical numbers. However, the mechanisms underlying basophil expansion remain unclear. In this study, we established that IL-3 played an important role in the rapid and specific expansion of basophils. We found that the IL-3 complex (IL-3 plus anti-IL-3 Ab) greatly facilitated the differentiation of GMPs into basophil lineage-restricted progenitors (BaPs) but not into eosinophil lineage-restricted progenitors or mast cells in the bone marrow. We also found that the IL-3 complex treatment resulted in ∼4-fold increase in the number of basophil/mast cell progenitors (BMCPs) in the spleen. IL-3-driven basophil expansion depended on STAT5 signaling. We showed that GMPs but not common myeloid progenitors expressed low levels of IL-3 receptor. IL-3 receptor expression was dramatically up-regulated in BaPs but not eosinophil lineage-restricted progenitors. Approximately 38% of BMCPs expressed the IL-3Rα-chain. The up-regulated IL-3 receptor expression was not affected by IL-3 or STAT5. Our findings demonstrate that IL-3 induced specific expansion of basophils by directing GMPs to differentiate into BaPs in the bone marrow and by increasing the number of BMCPs in the spleen.
The Levels of Retinoic Acid-Inducible Gene I Are Regulated by Heat Shock Protein 90-α
Authors: Matsumiya Tomoh , Imaizumi Tadaatsu , Yoshida Hidemi , Satoh Kei , Topham Matthew K. , Stafforini Diana M.
Published: February 2009

Retinoic acid-inducible gene I (RIG-I) is an intracellular pattern recognition receptor that plays important roles during innate immune responses to viral dsRNAs. The mechanisms and signaling molecules that participate in the downstream events that follow activation of RIG-I are incompletely characterized. In addition, the factors that define intracellular availability of RIG-I and determine its steady-state levels are only partially understood but are likely to play a major role during innate immune responses. It was recently reported that the antiviral activity of RIG-I is negatively regulated by specific E3 ubiquitin ligases, suggesting participation of the proteasome in the regulation of RIG-I levels. In this study, we used immunoprecipitation combined with mass spectrometry to identify RIG-I-interacting proteins and found that RIG-I forms part of a protein complex that includes heat shock protein 90-α (HSP90-α), a molecular chaperone. Biochemical studies using purified systems demonstrated that the association between RIG-I and HSP90-α is direct but does not involve participation of the CARD domain. Inhibition of HSP90 activity leads to the dissociation of the RIG-I-HSP90 complex, followed by ubiquitination and proteasomal degradation of RIG-I. In contrast, the levels of RIG-I mRNA are unaffected. Our studies also show that the ability of RIG-I to respond to stimulation with polyinosinic:polycytidylic acid is abolished when its interaction with HSP90 is inhibited. These novel findings point to HSP90-α as a chaperone that shields RIG-I from proteasomal degradation and modulates its activity. These studies identify a new mechanism whose dysregulation may seriously compromise innate antiviral responses in mammals.
Differential Migration of Epidermal and Dermal Dendritic Cells during Skin Infection
Authors: Eidsmo Liv , Allan Rhys , Caminschi Irina , van Rooijen Nico , Heath William R. , Carbone Francis R.
Published: February 2009

Dendritic cells (DCs) are extremely heterogeneous, most evident in the skin where a variety of different subsets have been identified in recent years. DCs of healthy skin include a number of distinct populations in the dermal layer as well as the well-characterized Langerhans cells (LCs) of the epidermis. These steady-state populations are augmented during bouts of local inflammation by additional monocyte-derived DCs. In an effort to better understand the distinction between the different subsets, we examined their behavior following skin infection with HSV. LC emigration rapidly followed appearance of virus in the skin and resulted in depopulation of regions in areas surrounding infected nerve endings. A separate DC population was found to accumulate within the dermis under patches of active epidermal infection with at least some derived from blood monocyte precursors. Ag-positive DCs could occasionally be found in these dermal accumulations, although they represented a minority of DCs in these areas. In addition, infected DCs appeared compromised in their trafficking capabilities and were largely absent from the migrating population. On resolution of skin disease, LCs repopulated the reformed epidermis and these were of mixed origin, with around half entering from the circulation and the remainder derived from local progenitors. Overall, our results show a range of migrational complexities between distinct skin DC populations as a consequence of localized infection.
Transgenic Inhibition of Astroglial NF-κB Improves Functional Outcome in Experimental Autoimmune Encephalomyelitis by Suppressing Chronic Central Nervous System Inflammation
Authors: Brambilla Roberta , Persaud Trikaldarshi , Hu Xianchen , Karmally Shaffiat , Shestopalov Valery I. , Dvoriantchikova Galina , Ivanov Dmitry , Nathanson Lubov , Barnum Scott R. , Bethea John R.
Published: February 2009

In the CNS, the transcription factor NF-κB is a key regulator of inflammation and secondary injury processes. Following trauma or disease, the expression of NF-κB-dependent genes is activated, leading to both protective and detrimental effects. In this study, we show that transgenic inactivation of astroglial NF-κB (glial fibrillary acidic protein-IκBα-dominant-negative mice) resulted in reduced disease severity and improved functional recovery following experimental autoimmune encephalomyelitis. At the chronic stage of the disease, transgenic mice exhibited an overall higher presence of leukocytes in spinal cord and brain, and a markedly higher percentage of CD8+CD122+ T regulatory cells compared with wild type, which correlated with the timing of clinical recovery. We also observed that expression of proinflammatory genes in both spinal cord and cerebellum was delayed and reduced, whereas the loss of neuronal-specific molecules essential for synaptic transmission was limited compared with wild-type mice. Furthermore, death of retinal ganglion cells in affected retinas was almost abolished, suggesting the activation of neuroprotective mechanisms. Our data indicate that inhibiting NF-κB in astrocytes results in neuroprotective effects following experimental autoimmune encephalomyelitis, directly implicating astrocytes in the pathophysiology of this disease.
Temporal Changes in Myeloid Cells in the Cervix during Pregnancy and Parturition
Authors: Timmons Brenda C. , Fairhurst Anna-Marie , Mahendroo Mala S.
Published: February 2009

Preterm birth occurs at a rate of 12.7% in the U.S. and is the primary cause of fetal morbidity in the first year of life as well as the cause of later health problems. Elucidation of mechanisms controlling cervical remodeling is critical for development of therapies to reduce the incidence of prematurity. The cervical extracellular matrix must be disorganized during labor to allow birth, followed by a rapid repair postpartum. Leukocytes infiltrate the cervix before and after birth and are proposed to regulate matrix remodeling during cervical ripening via release of proteolytic enzymes. In the current study, flow cytometry and cell sorting were used to determine the role of immune cells in cervical matrix remodeling before, during, and after parturition. Markers of myeloid cell differentiation and activation were assessed to define phenotype and function. Tissue monocytes and eosinophils increased in the cervix before birth in a progesterone-regulated fashion, whereas macrophage numbers were unchanged. Neutrophils increased in the postpartum period. Increased mRNA expression of Csfr1 and markers of alternatively activated M2 macrophages during labor or shortly postpartum suggest a function of M2 macrophages in postpartum tissue repair. Changes in cervical myeloid cell numbers are not reflected in the peripheral blood. These data along with our previous studies suggest that myeloid-derived cells do not orchestrate processes required for initiation of cervical ripening before birth. Additionally, macrophages with diverse phenotypes (M1 and M2) are present in the cervix and are most likely involved in the postpartum repair of tissue.
Engagement of CD83 on B Cells Modulates B Cell Function In Vivo
Authors: Kretschmer Birte , Lüthje Katja , Schneider Stefanie , Fleischer Bernhard , Breloer Minka
Published: February 2009

The transmembrane glycoprotein CD83 is an important regulator of both thymic T cell maturation and peripheral T cell response. Recent studies suggested that CD83 is also involved in the regulation of B cell maturation, activation, and homeostasis. In this study, we show that in vivo overexpression of CD83 dose dependently interfered with the Ig response to thymus-dependent and thymus-independent model Ag immunization. CD83 deficiency, in contrast, which was restricted to B cells in mixed bone marrow chimeras, led to unchanged or even slightly increased Ig responses. Strikingly, the engagement of CD83 that is naturally up-regulated on wild-type B cells by injection of anti-CD83 mAb in vivo induced a 100-fold increase in the IgG1 response to immunization. Kinetic analysis revealed that CD83 had to be engaged simultaneously or shortly after the B cell activation through injection of Ag, to modulate the IgG1 secretion. Furthermore, using mixed bone marrow chimeras in which either selectively the B cells or the dendritic cells were CD83 deficient, we demonstrate that anti-CD83 mAb mediated its biologic effect by engaging CD83 on B cells and not on CD11c+ dendritic cells. Taken together, we provide strong evidence that CD83 transduces regulatory signals into the very B cell on which it is expressed.
Cutting Edge: The Foxp3 Target miR-155 Contributes to the Development of Regulatory T Cells
Authors: Kohlhaas Susan , Garden Oliver A. , Scudamore Cheryl , Turner Martin , Okkenhaug Klaus , Vigorito Elena
Published: February 2009

Foxp3 is a transcription factor that is essential for the normal development of regulatory T cells (Tregs). In the absence of microRNAs (miRNAs), Foxp3+ Tregs develop but fail to maintain immune homeostasis, leading to a scurfy-like disease. Global analysis of the network of genes regulated by Foxp3 has identified the miRNA miR-155, which is highly expressed in Tregs, as a direct target of Foxp3. In this study we report that miR-155-deficient mice have reduced numbers of Tregs, both in the thymus and periphery, due to impaired development. However, we found no evidence for defective suppressor activity of miR-155-deficient Tregs, either in vitro or in vivo. Our results indicate that miR-155 contributes to Treg development, but that additional miRNAs control Treg function.
Ly6Clow Monocytes Differentiate into Dendritic Cells and Cross-Tolerize T Cells through PDL-1
Authors: Peng YuFeng , Latchman Yvette , Elkon Keith B.
Published: February 2009

Monocyte-derived dendritic cells are active participants during the immune response against infection, but whether they play a role in maintaining self-tolerance under steady-state conditions is not known. Here we investigated the differentiation of monocytes, their ability to ingest apoptotic cells, and their potential functionality in vivo. We observed that Ly6C (Gr-1)low mature monocytes up-regulate their MHC II level in the spleen, express high levels of PDL-1 (programmed death ligand 1), and are more efficient than Ly6Chigh immature monocytes in the ingestion of apoptotic cells in vivo. Sorted circulating Ly6Clow monocytes were able to cross-present both apoptotic cell-associated OVA and soluble OVA protein. Monocytes containing apoptotic cells can further differentiate into CD11c+CD8α−MHC II+ splenic dendritic cells that maintained high expression of PDL-1. Since wild-type but not PDL-1-deficient peripheral blood monocytes containing apoptotic cell-associated OVA suppressed the response to OVA immunization, PDL-1 expression was required for monocyte-mediated T cell tolerance. These observations demonstrate that Ly6Clow mature monocytes can promote tolerance to self Ag contained in apoptotic cells through a PDL-1-dependent mechanism.
Membrane Estrogen Receptor Regulates Experimental Autoimmune Encephalomyelitis through Up-regulation of Programmed Death 1
Authors: Wang Chunhe , Dehghani Babak , Li Yuexin , Kaler Laurie J. , Proctor Thomas , Vandenbark Arthur A. , Offner Halina
Published: February 2009

Although estrogens exert a pronounced protective effect on multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE), their therapeutic application has been limited by undesirable side effects thought to be mediated primarily through estradiol binding to intracellular estrogen receptor α. In this study, we found that signaling through the putative membrane estrogen receptor, G protein-coupled receptor 30 (GPR30), was sufficient to mediate protection against EAE, which was significantly impaired in GPR30 gene-deficient mice. Treatment with G-1, an agonist that selectively activates GPR30 without engagement of the intracellular estrogen receptors, retained the ability of estradiol to protect against clinical and histological EAE without estradiol-associated side effects, deviated cytokine profiles, and enhanced suppressive activity of CD4+Foxp3+ T regulatory cells through a GPR30- and programmed death 1-dependent mechanism. This study is the first to evaluate the protective effect of GPR30 activation on EAE, and provides a strong foundation for the clinical application of GPR30 agonists such as G-1 in multiple sclerosis.
NK Cell Enhancement of Antigen Presentation by B Lymphocytes
Authors: Jennings Paula , Yuan Dorothy
Published: February 2009

Ag presentation to CD4 T cells can be mediated by a number of cell types depending on the anatomical site in which Ag is first encountered. For blood borne Ags, cells localized in situ in the spleen should be major players. There is now much evidence that B cell Ag presentation may be particularly important in the priming of memory T cells. The majority of NK cells are also localized the spleen. Inasmuch as we have previously shown that NK cells can modulate various aspects of B cell differentiation, we entertained the possibility that NK cells can also influence Ag presentation by B cells. By specific depletion of NK cells before immunization, we show herein that NK cells play an important role in modulating the ability of B cells to process and present Ag to T cells. These effects are particularly important in the generation of memory T cells. The findings are further substantiated by in vitro experiments showing that the enhancement does not require IFN-γ but is mediated by direct cell-cell interaction. These results show, for the first time, that the rapid activation of a component of the innate response can even exert effects on the Ag-specific memory response.
STAT6 Deletion Converts the Th2 Inflammatory Pathology Afflicting LatY136F
Mice into a Lymphoproliferative Disorder Involving Th1 and CD8 Effector T Cells
Authors: Archambaud Cristel , Sansoni Amandine , Mingueneau Michael , Devilard Elisabeth , Delsol Georges , Malissen Bernard , Malissen Marie
Published: February 2009

Mutant mice in which tyrosine 136 of linker for activation of T cells (LAT) was replaced with a phenylalanine (LatY136F mice) develop a lymphoproliferative disorder involving polyclonal CD4 effector T cells that produce massive amounts of IL-4 and trigger severe Th2 inflammation. Naive CD4 T cells can themselves produce IL-4 and thereby initiate a self-reinforcing positive regulatory loop that involves the STAT6 transcription factor and leads to Th2 polarization. We determined the functional outcome that results when LatY136F T cells differentiate in the absence of such STAT6-dependent regulatory loop. The lack of STAT6 had no effect on the timing and magnitude of the lymphoproliferative disorder. However, in LatY136F mice deprived of STAT6, the expanding CD4 T cell population was dominated by Th1 effector cells that triggered B cell proliferation, elevated IgG2a and IgG2b levels as well as the production of autoantibodies. In contrast to LatY136F mice that showed no CD8 T cell expansion, the CD8 T cells present in LatY136F mice deprived of STAT6 massively expanded and acquired effector potential. Therefore, the lack of STAT6 is sufficient to convert the Th2 lymphoproliferative disorder that characterizes LatY136F mice into a lymphoproliferative disorder that is dominated by Th1 and CD8 effector T cells. The possibility to dispose of a pair of mice that differs by a single gene and develops in the absence of deliberate immunization large numbers of Th cells with almost reciprocal polarization should facilitate the identification of genes involved in the control of normal and pathological Th cell differentiation.
End-Organ Damage in a Mouse Model of Fulminant Liver Inflammation Requires CD4+ T Cell Production of IFN-γ but Is Independent of Fas
Authors: Robinson Richard T. , Wang Jing , Cripps James G. , Milks Michael W. , English Kathryn A. , Pearson Todd A. , Gorham James D.
Published: February 2009

Fulminant inflammation in the liver is often accompanied by the accumulation of IFN-γ-producing T cells. The BALB/c-Tgfb1−/− mouse exhibits extensive, spontaneously developing necroinflammation in the liver, accompanied by the accumulation of IFN-γ-producing CD4+ and CD8+ T cells. Liver damage depends on the presence of an intact Ifng gene. We determined the relevant cellular source(s) of IFN-γ. In Tgfb1−/− liver, CD4+ T cells were more numerous than CD8+ T cells and NK cells, and produced more IFN-γ. Depletion of CD4+ T cells eliminated both the elevation in plasma IFN-γ and aspartate aminotransferase, whereas depletion of CD8+ T cells did not. Rag1−/−Tgfb1−/− mice exhibited neither IFN-γ elevation nor tissue damage, indicating that NK cells are not sufficient. IFN-γ was required for strong overexpression of class II genes but not for CD4+ T cell activation, oligoclonal expansion, or accumulation in the liver. The T cell inhibitory molecule PD-L1 was strongly expressed in Tgfb1−/− livers, ruling out a lack of PD-L1 expression as an explanation for aberrant liver T cell activation. Finally, whereas Tgfb1−/− CD4+ T cells overexpressed Fas ligand, hepatocellular damage was observed in Faslpr/lprTgfb1−/− mice, indicating that liver pathology is Fas independent. We conclude that liver damage in this model of fulminant autoimmune hepatitis is driven by CD4+ T cell production of IFN-γ, is independent of both CD8+ T cells and the Fas ligand/Fas pathway, and is not explained by a lack of PD-L1 expression.
Alternatively Activated Macrophages Elicited by Helminth Infection Can Be Reprogrammed to Enable Microbial Killing
Authors: Mylonas Katie J. , Nair Meera G. , Prieto-Lafuente Lidia , Paape Daniel , Allen Judith E.
Published: February 2009

The prime function of classically activated macrophages (activated by Th1-type signals, such as IFN-γ) is microbial destruction. Alternatively activated macrophages (activated by Th2 cytokines, such as IL-4 and IL-13) play important roles in allergy and responses to helminth infection. We utilize a murine model of filarial infection, in which adult nematodes are surgically implanted into the peritoneal cavity of mice, as an in vivo source of alternatively activated macrophages. At 3 wk postinfection, the peritoneal exudate cell population is dominated by macrophages, termed nematode-elicited macrophages (NeMφ), that display IL-4-dependent features such as the expression of arginase 1, RELM-α (resistin-like molecule α), and Ym1. Since increasing evidence suggests that macrophages show functional adaptivity, the response of NeMφ to proinflammatory Th1-activating signals was investigated to determine whether a switch between alternative and classical activation could occur in macrophages differentiated in an in vivo infection setting. Despite the long-term exposure to Th2 cytokines and antiinflammatory signals in vivo, we found that NeMφ were not terminally differentiated but could develop a more classically activated phenotype in response to LPS and IFN-γ. This was reflected by a switch in the enzymatic pathway for arginine metabolism from arginase to inducible NO synthase and the reduced expression of RELM-α and Ym1. Furthermore, this enabled NeMφ to become antimicrobial, as LPS/IFN-γ-treated NeMφ produced NO that mediated killing of Leishmania mexicana. However, the adaptation to antimicrobial function did not extend to key regulatory pathways, such as IL-12 production, which remained unaltered.
Involvement of Proton-Sensing TDAG8 in Extracellular Acidification-Induced Inhibition of Proinflammatory Cytokine Production in Peritoneal Macrophages
Authors: Mogi Chihiro , Tobo Masayuki , Tomura Hideaki , Murata Naoya , He Xiao-dong , Sato Koichi , Kimura Takao , Ishizuka Tamotsu , Sasaki Takehiko , Sato Takashi , Kihara Yasuyuki , Ishii Satoshi , Harada Akihiro , Okajima Fumikazu
Published: February 2009

Extracellular acidification inhibited LPS-induced TNF-α protein production, which was associated with an inhibition of TNF-α mRNA expression, in mouse peritoneal macrophages. The LPS-induced cytokine production was also inhibited by Gs protein-coupled receptor agonists prostaglandin E1 and isoproterenol. Among OGR1 family proton-sensing GTP-binding regulatory protein-coupled receptors, TDAG8, OGR1, and G2A are expressed in the cells. The inhibitory action by acidic pH on TNF-α production was significantly attenuated in macrophages from TDAG8Tp/Tp mice but not in those from OGR1geo/geo mice. Moreover, small interfering RNA specific to TDAG8, but not to G2A, clearly attenuated the acidification-induced inhibition of TNF-α production. On the other hand, the down-regulation or deficiency of TDAG8 hardly affected prostaglandin E1- or isoproterenol-induced actions. LPS-induced IL-6 production was also inhibited by extracellular acidification in a manner that was sensitive to TDAG8 expression. The acidic pH-induced inhibitory action on the cytokine production was significantly reversed either by a small interfering RNA specific to Gs proteins or by a protein kinase A (PKA)-specific inhibitor H89. Indeed, a PKA-specific cAMP derivative inhibited LPS-induced cytokine production. Moreover, acidification induced cAMP accumulation in a TDAG8-specific way. We conclude that TDAG8, at least partly, mediates the extracellular acidification-induced inhibition of proinflammatory cytokine production through the Gs protein/cAMP/PKA signaling pathway in mouse macrophages.
Vaccinia Virus-Based Multivalent H5N1 Avian Influenza Vaccines Adjuvanted with IL-15 Confer Sterile Cross-Clade Protection in Mice
Authors: Poon Leo L. M. , Leung Y. H. Connie , Nicholls John M. , Perera Pin-Yu , Lichy Jack H. , Yamamoto Masafumi , Waldmann Thomas A. , Peiris J. S. Malik , Perera Liyanage P.
Published: February 2009

The potential for a global influenza pandemic remains significant with epidemiologic and ecologic indicators revealing the entrenchment of the highly pathogenic avian influenza A H5N1 in both wild bird populations and domestic poultry flocks in Asia and in many African and European countries. Indisputably, the single most effective public health intervention in mitigating the devastation such a pandemic could unleash is the availability of a safe and effective vaccine that can be rapidly deployed for pre-exposure vaccination of millions of people. We have developed two vaccinia-based influenza vaccines that are molecularly adjuvanted with the immune stimulatory cytokine IL-15. The pentavalent Wyeth/IL-15/5Flu vaccine expresses the hemagglutinin, neuraminidase, and nucleoprotein derived from the H5N1 influenza virus A/Vietnam/1203/2004 and the matrix proteins M1 and M2 from the H5N1 A/CK/Indonesia/PA/2003 virus on the backbone of a currently licensed smallpox vaccine. The bivalent MVA/IL-15/HA/NA vaccine expresses only the H5 hemagglutinin and N1 neuraminidase on the modified vaccinia virus Ankara (MVA) backbone. Both vaccines induced cross-neutralizing Abs and robust cellular immune responses in vaccinated mice and conferred sterile cross-clade protection when challenged with the H5N1 virus of a different clade. In addition to having potential as a universal influenza vaccine, in the event of an impending pandemic the Wyeth/IL-15/5Flu is also readily amenable to bulk production to cover the global population. For those individuals for whom the use of the Wyeth vaccine is contraindicated, our MVA/IL-15/HA/NA offers a substitute or a prevaccine to be used in a mass vaccination campaign similar to the smallpox eradication campaigns of few decades ago.
Amplification of Autoimmune Response through Induction of Dendritic Cell Maturation in Inflamed Tissues
Authors: Melli Kristin , Friedman Rachel S. , Martin Ashley E. , Finger Erik B. , Miao Gang , Szot Gregory L. , Krummel Matthew F. , Tang Qizhi
Published: February 2009

Dendritic cells (DCs) are essential in T cell-mediated destruction of insulin-producing β cells in the islets of Langerhans in type 1 diabetes. In this study, we investigated T cell induction of intra-islet DC maturation during the progression of the disease in both autoimmune-prone NOD and resistant C57BL/6 mice. We demonstrated steady-state capture and retention of unprocessed β cell-derived proteins by semimature intra-islet DCs in both mouse strains. T cell-mediated intra-islet inflammation induced an increase in CD40 and CD80 expression and processing of captured Ag by resident DCs without inducing the expression of the p40 subunit of IL-12/23. Some of the CD40high intra-islet DCs up-regulated CCR7, and a small number of CD40high DCs bearing unprocessed islet Ags were detected in the pancreatic lymph nodes in mice with acute intra-islet inflammation, demonstrating that T cell-mediated tissue inflammation augments migration of mature resident DCs to draining lymph nodes. Our results identify an amplification loop during the progression of autoimmune diabetes, in which initial T cell infiltration leads to rapid maturation of intra-islet DCs, their migration to lymph nodes, and expanded priming of more autoreactive T cells. Therapeutic interventions that intercept this process may be effective at halting the progression of type 1 diabetes.
Promoter Knock-In Mutations Reveal a Role of Mcl-1 in Thymocyte-Positive Selection and Tissue or Cell Lineage-Specific Regulation of Mcl-1 Expression
Authors: Yang Chia-Yu , Lin Nai-Hui , Lee Jan-Mou , Huang Ching-Yu , Min Hsiang-Ju , Yen Jeffrey Jong-Young , Liao Nan-Shih , Yang-Yen Hsin-Fang
Published: February 2009

We previously demonstrated that IL-3 stimulates transcription of the antiapoptotic gene mcl-1 via two promoter elements designated as the SIE and CRE-2 sites. To further study the functional role of these two DNA elements, mutant mice with targeted mutations of both SIE and CRE-2 sites (SC mutants) were generated. Homozygous SC mutants manifested a markedly reduced level of Mcl-1 in thymus but not in other major organs such as spleen, liver, lung, or heart. Reduced expression of Mcl-1 in SC mutant thymus resulted in attenuated positive selection of double-positive thymocytes into both CD4 and CD8 lineages, a result likely due to reduced survival of SC mutant double-positive thymocytes that were supposed to be positively selected. In contrast, in the peripheral lymphoid organs, only CD8+ but not CD4+ T cells were significantly reduced in homozygous SC mutant mice, a result consistent with a more dramatic decrease both of Mcl-1 expression and cell viability in mutant CD8+ compared with mutant CD4+ T cells. Impaired T cell development and peripheral CD8+ lymphopenia in homozygous SC mutant mice were both cell autonomous and could be rescued by enforced expression of human Mcl-1. Together, the promoter-knock-in mouse model generated in this study not only revealed a role of Mcl-1 in thymocyte-positive selection, but also uncovered that Mcl-1 expression is regulated in a tissue or cell lineage-specific manner.
Fas Ligand Is Required for the Development of Respiratory Syncytial Virus Vaccine-Enhanced Disease
Authors: Olson Matthew R. , Varga Steven M.
Published: February 2009

Children immunized with a formalin-inactivated respiratory syncytial virus (RSV) vaccine experienced enhanced disease and exhibited pulmonary eosinophilia upon natural RSV infection. BALB/c mice immunized with either formalin-inactivated RSV or a recombinant vaccinia virus (vacv) expressing the RSV attachment (G) protein develop extensive pulmonary eosinophilia after RSV challenge that mimics the eosinophilic response observed in the children during the 1960s vaccine trials. Fas ligand (FasL) is a major immune effector molecule that can contribute to the clearance of respiratory viruses. However, the role of FasL in the development of RSV vaccine-enhanced disease has not been elucidated. RSV challenge of vacvG-immunized gld mice, that lack functional FasL, results in diminished systemic disease as well as pulmonary eosinophilia. The magnitude of the secondary RSV G-specific CD4 T cell response was diminished in gld mice as compared with wild-type controls. Furthermore, we show that CD4 T cells isolated after RSV challenge of vacvG-immunized gld mice exhibit enhanced expression of Annexin V and caspase 3/7 indicating that FasL is important for either the survival or the expansion of virus-specific secondary effector CD4 T cells. Taken together, these data identify a previously undefined role for FasL in the accumulation of secondary effector CD4 T cells and the development of RSV vaccine-enhanced disease.