bluuebunny/crossref_metadata_2025 huggingface dataset:
The Low Molecular Weight GTPase RhoA and Atypical Protein Kinase Cζ Are Required for TLR2-Mediated Gene Transcription
Authors: Teusch Nicole , Lombardo Eleuterio , Eddleston Jane , Knaus Ulla G.
Published: April 2014

The Rho GTPases are molecular switches that regulate many essential cellular processes, including actin dynamics, gene transcription, cell cycle progression, cell adhesion, and motility. In this study, we report that stimulation of TLR2 in human epithelial and monocytic cells leads to rapid and transient activation of RhoA. RhoA cooperated with the canonical I-κB kinase-mediated pathway that induces the release of NF-κB, in regulating the trans activation of the NF-κB subunit p65/RelA by affecting Ser311 phosphorylation, and subsequent cytokine production. Another consequence of TLR2 stimulation by bacterial derived products was the activation of atypical protein kinase C (PKC) ζ and association of this protein kinase with RhoA. Inhibition of PKCζ decreased NF-κB activation and p65/RelA trans activation without affecting I-κBα degradation. The observation of a transient, stimulus-dependent association of RhoA with PKCζ suggests that RhoA mediates at least partially its effect on gene transcription through atypical PKC. In contrast to previous studies, identifying Rac1-PI3K as an upstream element in TLR2-initiated response to NF-κB, PI3K signaling was not required for RhoA or PKCζ activity. These results indicate that multiple GTPase-regulated pathways emerge from stimulated Toll receptors, controlling different aspects of NF-κB-mediated gene transcription.
Activity of α- and θ-Defensins against Primary Isolates of HIV-1
Authors: Wang Wei , Owen Sherry M. , Rudolph Donna L. , Cole Alexander M. , Hong Teresa , Waring Alan J. , Lal Renu B. , Lehrer Robert I.
Published: April 2014

θ-Defensins are lectin-like, cyclic octadecapeptides found in the leukocytes of nonhuman primates. They are also homologues of the more familiar α-defensins expressed by humans and certain other mammals. This study compares the ability of six θ-defensins (hominid retrocyclins 1–3 and rhesus θ-defensins 1–3) and four human α-defensins (human neutrophil peptides (HNPs) 1–4) to bind gp120 and CD4. In addition, we compared the ability of these θ-defensins and HNP-1 to protect J53-BL cells (an indicator cell line) from primary HIV-1 isolates that varied in subtype and coreceptor usage. The most potent θ-defensin, retrocyclin-2, bound with exceptionally high affinity to gp120 (KD, 9.4 nM) and CD4 (KD, 6.87 nM), and its effectiveness against subtype B isolates (IC50, 1.05 ± 0.28 μg/ml; 520 ± 139 nM) was approximately twice as great as that of HNP-1 on a molar basis. We also show, for the first time, that human α-defensins, HNPs 1–3, are lectins that bind with relatively high affinity to gp120 (KD range, 15.8–52.8 nM) and CD4 (KD range, 8.0–34.9 nM). Proteins found in human and FBS bound exogenous HNP-2 and retrocyclin-1, and competed with their ability to bind gp120. However, even the low concentrations of α-defensins found in normal human serum suffice to bind over half of the gp120 spikes on HIV-1 and a higher percentage of cell surface CD4 molecules. Although this report principally concerns the relationship between carbohydrate-binding and the antiviral properties of α- and θ-defensins, the lectin-like behavior of defensins may contribute to many other activities of these multifunctional peptides.
High Bactericidal Efficiency of Type IIA Phospholipase A2 against Bacillus anthracis and Inhibition of Its Secretion by the Lethal Toxin
Authors: Gimenez Alejandro Piris , Wu Yong-Zheng , Paya Miguel , Delclaux Christophe , Touqui Lhousseine , Goossens Pierre L.
Published: April 2014

There is a considerable body of evidence supporting the role of secretory type II-A phospholipase A2 (sPLA2-IIA) as an effector of the innate immune response. This enzyme also exhibits bactericidal activity especially toward Gram-positive bacteria. In this study we examined the ability of sPLA2-IIA to kill Bacillus anthracis, the etiological agent of anthrax. Our results show that both germinated B. anthracis spores and encapsulated bacilli were sensitive to the bactericidal activity of recombinant sPLA2-IIA in vitro. In contrast, nongerminated spores were resistant. This bactericidal effect was correlated to the ability of sPLA2-IIA to hydrolyze bacterial membrane phospholipids. Guinea pig alveolar macrophages, the major source of sPLA2-IIA in an experimental model of acute lung injury, released enough sPLA2-IIA to kill extracellular B. anthracis. The production of sPLA2-IIA was significantly inhibited by B. anthracis lethal toxin. Human bronchoalveolar lavage fluids from acute respiratory distress syndrome patients are known to contain sPLA2-IIA; bactericidal activity against B. anthracis was detected in a high percentage of these samples. This anthracidal activity was correlated to the levels of sPLA2-IIA and was abolished by an sPLA2-IIA inhibitor. These results suggest that sPLA2-IIA may play a role in innate host defense against B. anthracis infection and that lethal toxin may help the bacteria to escape from the bactericidal action of sPLA2-IIA by inhibiting the production of this enzyme.
Double Mechanism for Apical Tryptophan Depletion in Polarized Human Bronchial Epithelium
Authors: Zegarra-Moran Olga , Folli Chiara , Manzari Benedetta , Ravazzolo Roberto , Varesio Luigi , Galietta Luis J. V.
Published: April 2014

Indoleamine 2,3-dioxygenase is an enzyme that catabolizes tryptophan to kynurenine. We investigated the consequences of IDO induction by IFN-γ in polarized human bronchial epithelium. IDO mRNA expression was undetectable in resting conditions, but strongly induced by IFN-γ. We determined the concentration of tryptophan and kynurenine in the extracellular medium, and we found that apical tryptophan concentration was lower than the basolateral in resting cells. IFN-γ caused a decrease in tryptophan concentration on both sides of the epithelium. Kynurenine was absent in control conditions, but increased in the basolateral medium after IFN-γ treatment. The asymmetric distribution of tryptophan and kynurenine suggested the presence of a transepithelial amino acid transport. Uptake experiments with radiolabeled amino acids demonstrated the presence of a Na+-dependent amino acid transporter with broad specificity that was responsible for the tryptophan/kynurenine transport. We confirmed these data by measuring the short-circuit currents elicited by direct application of tryptophan or kynurenine to the apical surface. The rate of amino acid transport was dependent on the transepithelial potential, and we established that in cystic fibrosis epithelia, in which the transepithelial potential is significantly more negative than in noncystic fibrosis epithelia, amino acid uptake was reduced. This work suggests that human airway epithelial cells maintain low apical tryptophan concentrations by two mechanisms, a removal through a Na+-dependent amino acid transporter and an IFN-γ-inducible degradation by IDO.
Prostaglandin E2 Inhibits Alveolar Macrophage Phagocytosis through an E-Prostanoid 2 Receptor-Mediated Increase in Intracellular Cyclic AMP
Authors: Aronoff David M. , Canetti Claudio , Peters-Golden Marc
Published: April 2014

Prostaglandin E2 is a potent lipid mediator of inflammation that effects changes in cell functions through ligation of four distinct G protein-coupled receptors (E-prostanoid (EP)1, EP2, EP3, and EP4). During pneumonia, PGE2 production is enhanced. In the present study, we sought to assess the effect of endogenously produced and exogenously added PGE2 on FcRγ-mediated phagocytosis of bacterial pathogens by alveolar macrophages (AMs), which are critical participants in lung innate immunity. We also sought to characterize the EP receptor signaling pathways responsible for these effects. PGE2 (1–1000 nM) dose-dependently suppressed the phagocytosis by rat AMs of IgG-opsonized erythrocytes, immune serum-opsonized Klebsiella pneumoniae, and IgG-opsonized Escherichia coli. Conversely, phagocytosis was stimulated by pretreatment with the cyclooxygenase inhibitor indomethacin. PGE2 suppression of phagocytosis was associated with enhanced intracellular cAMP production. Experiments using both forskolin (adenylate cyclase activator) and rolipram (phosphodiesterase IV inhibitor) confirmed the inhibitory effect of cAMP stimulation. Immunoblot analysis of rat AMs identified expression of only EP2 and EP3 receptors. The selective EP2 agonist butaprost, but neither the EP1/EP3 agonist sulprostone nor the EP4-selective agonist ONO-AE1-329, mimicked the effects of PGE2 on phagocytosis and cAMP stimulation. Additionally, the EP2 antagonist AH-6809 abrogated the inhibitory effects of both PGE2 and butaprost. We confirmed the specificity of our results by showing that AMs from EP2-deficient mice were resistant to the inhibitory effects of PGE2. Our data support a negative regulatory role for PGE2 on the antimicrobial activity of AMs, which has important implications for future efforts to prevent and treat bacterial pneumonia.
Helicobacter pylori Arginase Inhibits T Cell Proliferation and Reduces the Expression of the TCR ζ-Chain (CD3ζ)
Authors: Zabaleta Jovanny , McGee David J. , Zea Arnold H. , Hernández Claudia P. , Rodriguez Paulo C. , Sierra Rosa A. , Correa Pelayo , Ochoa Augusto C.
Published: April 2014

Helicobacter pylori infects approximately half the human population. The outcomes of the infection range from gastritis to gastric cancer and appear to be associated with the immunity to H. pylori. Patients developing nonatrophic gastritis present a Th1 response without developing protective immunity, suggesting that this bacterium may have mechanisms to evade the immune response of the host. Several H. pylori proteins can impair macrophage and T cell function in vitro through mechanisms that are poorly understood. We tested the effect of H. pylori extracts and live H. pylori on Jurkat cells and freshly isolated human normal T lymphocytes to identify possible mechanisms by which the bacteria might impair T cell function. Jurkat cells or activated T lymphocytes cultured with an H. pylori sonicate had a reduced proliferation that was not caused by T cell apoptosis or impairment in the early T cell signaling events. Instead, both the H. pylori sonicate and live H. pylori induced a decreased expression of the CD3ζ-chain of the TCR. Coculture of live H. pylori with T cells demonstrated that the wild-type strain, but not the arginase mutant rocF(−), depleted l-arginine and caused a decrease in CD3ζ expression. Furthermore, arginase inhibitors reversed these events. These results suggest that H. pylori arginase is not only important for urea production, but may also impair T cell function during infection.
Identification of Peptides That Antagonize Formyl Peptide Receptor-Like 1-Mediated Signaling
Authors: Bae Yoe-Sik , Lee Ha Young , Jo Eun Jin , Kim Jung Im , Kang Hyun-Kyu , Ye Richard D. , Kwak Jong-Young , Ryu Sung Ho
Published: April 2014

Formyl peptide receptor-like 1 (FPRL1) is an important classical chemoattractant receptor that is expressed in phagocytic cells in the peripheral blood and brain. Recently, various novel agonists have been identified from several origins, such as host-derived molecules. Activation of FPRL1 is closely related to inflammatory responses in the host defense mechanism and neurodegenerative disorders. In the present study we identified several novel peptides by screening hexapeptide libraries that inhibit the binding of one of FPRL1’s agonists (Trp-Lys-Tyr-Met-Val-d-Met-CONH2 (WKYMVm)) to its specific receptor, FPRL1, in RBL-2H3 cells. Among the novel peptides, Trp-Arg-Trp-Trp-Trp-Trp-CONH2 (WRWWWW (WRW4)) showed the most potent activity in terms of inhibiting WKYMVm binding to FPRL1. We also found that WRW4 inhibited the activation of FPRL1 by WKYMVm, resulting in the complete inhibition of the intracellular calcium increase, extracellular signal-regulated kinase activation, and chemotactic migration of cells toward WKYMVm. For the receptor specificity of WRW4 to the FPR family, we observed that WRW4 specifically inhibit the increase in intracellular calcium by the FPRL1 agonists MMK-1, amyloid β42 (Aβ42) peptide, and F peptide, but not by the FPR agonist, fMLF. To investigate the effect of WRW4 on endogenous FPRL1 ligand-induced cellular responses, we examined its effect on Aβ42 peptide in human neutrophils. Aβ42 peptide-induced superoxide generation and chemotactic migration of neutrophils were inhibited by WRW4, which also completely inhibited the internalization of Aβ42 peptide in human macrophages. WRW4 is the first specific FPRL1 antagonist and is expected to be useful in the study of FPRL1 signaling and in the development of drugs against FPRL1-related diseases.
Rac and Protein Kinase C-δ Regulate ERKs and Cytosolic Phospholipase A2 in FcεRI Signaling to Cysteinyl Leukotriene Synthesis in Mast Cells
Authors: Cho Sung-Hoon , You Hye-Jin , Woo Chang-Hoon , Yoo Yung-Joon , Kim Jae-Hong
Published: April 2014

Although cysteinyl leukotrienes (cysLTs) are known to be principal inflammatory lipid mediators released from IgE-stimulated mast cells, the signaling mechanisms involved in the synthesis of cysLTs remain largely unknown. In the present study, therefore, we investigated the signaling pathway by which IgE induces cysLTs synthesis after binding to its high affinity receptor (FcεRI) in RBL-2H3 mast cells. We found that IgE-induced cysLT synthesis is completely abolished in RBL-2H3Rac-N17 cells, a stable cell line expressing RacN17, a dominant negative Rac1 mutant; conversely, synthesis was enhanced in cells expressing RacV12, a constitutively active Rac1 mutant, suggesting that Rac1 is a key mediator of IgE signaling to cysLT synthesis. Further analysis aimed at identifying mediators downstream of Rac1 revealed that pretreating cells with a protein kinase C-δ (PKC-δ) inhibitor or infection with an adenoviral vector harboring a dominant negative PKC-δ mutant significantly attenuates IgE-induced ERKs phosphorylation, cytosolic phospholipase A2 phosphorylation/translocation, and cysLT synthesis. In addition, the expression of RacN17 blocked PKC-δ translocation and impaired the phosphorylation of ERKs and cytosolic phospholipase A2 otherwise elicited by IgE stimulation. Taken together these results suggest that PKC-δ also plays a critical mediatory role in the IgE signaling pathway leading to cysLT synthesis, acting downstream of Rac1. Finally, the physiological significance of PKC-δ in the IgE signaling pathway was demonstrated in an Ag (OVA)-challenged in vivo mouse model, in which induced levels of cysLTs and airway responsiveness in lung airways were significantly diminished by prior i.p. injection of a PKC-δ inhibitor.
Distinct Activation Signals Determine whether IL-21 Induces B Cell Costimulation, Growth Arrest, or Bim-Dependent Apoptosis
Authors: Jin Haoli , Carrio Roberto , Yu Aixin , Malek Thomas R.
Published: April 2014

IL-21 costimulates B cell proliferation and cooperatively with IL-4 promotes T cell-dependent Ab responses. Somewhat paradoxically, IL-21 also induces apoptosis of B cells. The present study was undertaken to more precisely define the expression of the IL-21R, using a novel mAb, and the circumstances by which IL-21 promotes B cell growth vs death. The IL-21R was first detected during T and B cell development, such that this receptor is expressed by all mature lymphocytes. The IL-21R was further up-regulated after B and T activation, with the highest expression by activated B cells. Functional studies demonstrated that IL-21 substantially inhibited proliferation and induced Bim-dependent apoptosis for LPS or CpG DNA-activated B cells. In contrast, IL-21 induced both costimulation and apoptosis for anti-CD40-stimulated B cells, whereas IL-21 primarily costimulated B cells activated by anti-IgM or anti-IgM plus anti-CD40. Upon blocking apoptosis using C57BL/6 Bim-deficient or Bcl-2 transgenic B cells, IL-21 readily costimulated responses to anti-CD40 while proliferation to LPS was still inhibited. Engagement of CD40 or the BCR plus CD40 prevented the inhibitory effect by IL-21 for LPS-activated B cells. Collectively, these data indicate that there are three separable outcomes for IL-21-stimulated B cells: apoptosis, growth arrest, or costimulation. We favor a model in which IL-21 promotes B cell maturation during a productive T cell-dependent B cell response, while favoring growth arrest and apoptosis for nonspecifically or inappropriately activated B cells.
Age-Associated Change in the Frequency of Memory CD4+ T Cells Impairs Long Term CD4+ T Cell Responses to Influenza Vaccine
Authors: Kang Insoo , Hong Myung Sun , Nolasco Helena , Park Sung Hwan , Dan Jin Myung , Choi Jin-Young , Craft Joe
Published: April 2014

We investigated the relationship of memory CD4+ T cells with the evolution of influenza virus-specific CD4+ T cell responses in healthy young and elderly people. Elderly individuals had a similar frequency of CD69+CD4+ T cells producing IFN-γ and TNF-α at 1 wk, but a lower frequency of these CD4+ T cells at 3 mo after influenza vaccination. Although the elderly had a higher frequency of central memory (CM; CCR7+CD45RA−) CD4+ T cells, they had a significantly lower frequency of effector memory (EM; CCR7−CD45RA−) CD4+ T cells, and the frequency of the latter memory CD4+ T cells positively correlated with the frequency of influenza virus-specific CD69+CD4+ T cells producing IFN-γ at 3 mo. These findings indicate that the elderly have an altered balance of memory CD4+ T cells, which potentially affects long term CD4+ T cell responses to the influenza vaccine. Compared with the young, the elderly had decreased serum IL-7 levels that positively correlated with the frequency of EM cells, which suggests a relation between IL-7 and decreased EM cells. Thus, although the healthy elderly mount a level of CD4+ T cell responses after vaccination comparable to that observed in younger individuals, they fail to maintain or expand these responses. This failure probably stems from the alteration in the frequency of CM and EM CD4+ T cells in the elderly that is related to alteration in IL-7 levels. These findings raise an important clinical question about whether the vaccination strategy in the elderly should be modified to improve cellular immune responses.
T Follicular Helper Cells Express a Distinctive Transcriptional Profile, Reflecting Their Role as Non-Th1/Th2 Effector Cells That Provide Help for B Cells
Authors: Chtanova Tatyana , Tangye Stuart G. , Newton Rebecca , Frank Nita , Hodge Martin R. , Rolph Michael S. , Mackay Charles R.
Published: April 2014

Effector T cell responses have long been viewed in the context of the Th1/Th2 paradigm. Recently, a third major subset of nonpolarized effector T cells that provides help to B cells has been identified. These T cells, termed T follicular helper (TFH) cells, home to the B cell areas of secondary lymphoid tissue, through interactions mediated via the chemokine receptor CXCR5 and its ligand CXCL13. Affymetrix microarrays were used to identify transcription factors, cytokines, and cell surface molecules that underlie the differentiation pathways and functional properties of the TFH subset. The transcriptional profile of human CXCR5+ TFH cells was compared with that of Th1 and Th2 cells, which enabled the identification of numerous genes expressed preferentially by TFH cells, over the other effector subsets. Certain TFH genes were also expressed by B cells and thus appear to be particularly relevant for humoral immunity. Abs were used to confirm the expression of several factors. In particular, CD84 and CD200, the cytokine IL-21, and the transcription factor BCL6 were all strongly associated with TFH cells. Gene microarrays reveal a highly distinctive transcriptional profile for a third subset of effector T cells that differs markedly from Th1 and Th2 cells.
Lymphotoxin and TNF Produced by B Cells Are Dispensable for Maintenance of the Follicle-Associated Epithelium but Are Required for Development of Lymphoid Follicles in the Peyer’s Patches
Authors: Tumanov Alexei V. , Kuprash Dmitry V. , Mach Julie A. , Nedospasov Sergei A. , Chervonsky Alexander V.
Published: April 2014

Organogenesis of Peyer‘s patches (PP), follicle-associated epithelium, and M cells is impaired in mice lacking B cells. At the same time, lymphotoxin (LT) and TNF are known to be critical for the development of PP. To directly address the function of LT and TNF expressed by B cells in the maintenance of PP structure, we studied the de novo formation of PP in B cell-deficient mice after the transfer of bone marrow from mice with targeted mutations in LT, TNF, or their combinations. We found that although the compartmentalization of T and B cell zones and development of follicular dendritic cells were affected by the lack of B cell-derived LT and TNF, the development of follicle-associated epithelium and M cells in PP was completely independent of LT/TNF production by B cells.
The Third Signal in T Cell-Mediated Autoimmune Disease?
Authors: Darabi Kamruz , Karulin Alexey Y. , Boehm Bernhard O. , Hofstetter Harald H. , Fabry Zsuzsa , LaManna Joseph C. , Chavez Juan C. , Tary-Lehmann Magdalena , Lehmann Paul V.
Published: April 2014

The initial event in the pathogenesis of autoimmune disease is thought to be the priming of naive autoreactive T cells by an infection with a cross-reactive microorganism. Although such cross-reactive priming should be a common event, autoimmune disease does not frequently develop. This situation is reflected after the immunization of C57BL/6 mice with the neuroantigen myelin oligodendrocyte glycoprotein (MOG) with CFA, which primes a type 1 T cell response but does not lead to clinical or histological manifestation of experimental allergic encephalomyelitis unless pertussis toxin is injected in addition. We show in this study that, in MOG:CFA-primed mice, the autoimmune CNS pathology develops after intracerebral deposition of TLR9-activating CpG oligonucleotides, but not following non-CpG oligonucleotide injection or after aseptic cryoinjury of the brain. Thus, access of primed MOG-specific Th1 cells to the uninflamed CNS or to CNS undergoing sterile inflammation did not suffice to elicit autoimmune pathology; only if the APC in the target organ were activated in addition by the TLR9-stimulating microbial product did they exert local effector functions. The data suggest that such licensing of APC in the target organ by microbial stimuli represents a checkpoint for functional self-tolerance. Therefore, microorganisms unrelated to the cross-reactive agent that primes the autoreactive T cells could dictate the onset and exacerbation of autoimmune diseases.
TLR Signaling: An Emerging Bridge from Innate Immunity to Atherogenesis
Authors: Michelsen Kathrin S. , Doherty Terence M. , Shah Prediman K. , Arditi Moshe
Published: April 2014

Chronic inflammation and disordered lipid metabolism represent hallmarks of atherosclerosis. Considerable evidence suggests that innate immune defense mechanisms might interact with proinflammatory pathways and contribute to development of arterial plaques. The preponderance of such evidence has been indirect clinical and epidemiologic studies, with some support from experimental animal models of atherosclerosis. However, recent data now directly implicate signaling by TLR4 in the pathogenesis of atherosclerosis, establishing a key link between atherosclerosis and defense against both foreign pathogens and endogenously generated inflammatory ligands. In this study, we briefly review these and closely related studies, highlighting areas that should provide fertile ground for future studies aimed at a more comprehensive understanding of the interplay between innate immune defense mechanisms, atherosclerosis, and related vascular disorders.
Cutting Edge: Human Eosinophils Regulate T Cell Subset Selection through Indoleamine 2,3-Dioxygenase
Authors: Odemuyiwa Solomon O. , Ghahary Ahmad , Li Yunyuan , Puttagunta Lakshmi , Lee Joo Eun , Musat-Marcu Sorin , Ghahary Aziz , Moqbel Redwan
Published: April 2014

Allergy involves eosinophilia and Th2 polarization. Indoleamine 2,3-dioxygenase (IDO)-catalyzed conversion of tryptophan to kynurenines (KYN) regulates T cell function. We show that human eosinophils constitutively express IDO. Eosinophils treated with IFN-γ showed an 8-fold increase in IDO mRNA within 4 h; IL-3, IL-5, and GM-CSF had no effect on baseline IDO expression. IL-3 pretreatment of eosinophils reduced IFN-γ-induced IDO mRNA expression below baseline. Conversely, GM-CSF, but not IL-5, resulted in a 2-fold increase in IFN-γ-induced IDO. Treatment with IL-3, IL-5, GM-CSF, or IFN-γ alone expressed IDO enzymatic activity (the presence of KYN in supernatants 48 h postculture). CD28 cross-linking resulted in measurable KYN in culture supernatants, inhibitable by a neutralizing anti-IFN-γ. Coculture of eosinophils with an IFN-γ-producing T cell line, but not IL-4-producing T cell clone, led to apoptosis and inhibition of CD3 or CD3/CD28-induced proliferation. Eosinophils infiltrating asthmatic lung and associated lymphoid tissue exhibited intracellular IDO immunoreactivity. Eosinophils may, therefore, maintain Th2 bias through IDO.
Cutting Edge: Bone Morphogenetic Protein Antagonists Drm/Gremlin and Dan Interact with Slits and Act as Negative Regulators of Monocyte Chemotaxis
Authors: Chen Bo , Blair Donald G. , Plisov Sergei , Vasiliev Gennady , Perantoni Alan O. , Chen Qian , Athanasiou Meropi , Wu Jane Y. , Oppenheim Joost J. , Yang De
Published: April 2014

Drm/Gremlin and Dan, two homologous secreted antagonists of bone morphogenic proteins, have been shown to regulate early development, tumorigenesis, and renal pathophysiology. In this study, we report that Drm and Dan physically and functionally interact with Slit1 and Slit2 proteins. Drm binding to Slits depends on its glycosylation and is not interfered with by bone morphogenic proteins. Importantly, Drm and Dan function as inhibitors for monocyte migration induced by stromal cell-derived factor 1α (SDF-1α) or fMLP. The inhibition of SDF-1α-induced monocyte chemotaxis by Dan is not due to blocking the binding of SDF-1α to its receptor. Thus, the results identify that Drm and Dan can interact with Slit proteins and act as inhibitors of monocyte chemotaxis, demonstrating a previously unidentified biological role for these proteins.
Cutting Edge: Immunity and IFN-γ Production during Listeria monocytogenes Infection in the Absence of T-bet
Authors: Way Sing Sing , Wilson Christopher B.
Published: April 2014

The T-box transcription factor T-bet is an important regulator of IFN-γ production in all cell types and is considered to be essential for the generation of CD4 Th1 T cells. IFN-γ in turn plays a critical role in immunity to many infectious agents. In this study, we demonstrate that T-bet is not required for host resistance to primary Listeria monocytogenes (LM) infection. In the innate immune phase, control of LM replication, serum IFN-γ, and numbers of IFN-γ-producing NK cells were similar in T-bet-deficient and control mice. In the adaptive immune phase, there was no defect in bacterial clearance or in the numbers of LM-specific IFN-γ-producing CD8 T cells in T-bet-deficient mice and only a modest, although significant, reduction in the numbers of Th1 CD4 T cells and IFN-γ secretion by CD4 T cells. Thus, host resistance and the generation of IFN-γ-producing cells in response to LM infection are not substantially compromised in the absence of T-bet.
Cutting Edge: Tumor-Specific CTL Are Constitutively Cross-Armed in Draining Lymph Nodes and Transiently Disseminate to Mediate Tumor Regression following Systemic CD40 Activation
Authors: Stumbles Philip A. , Himbeck Robyn , Frelinger Jeffrey A. , Collins Edward J. , Lake Richard A. , Robinson Bruce W. S.
Published: April 2014

The cross-arming of effector CTL in response to cross-presented tumor Ags is predicted to fail in the absence of CD40 stimulation. However, questions remain regarding the role of CD40 signaling and additional CD4+ T cell-derived signals in this process. To address this, we have analyzed the cross-arming of tumor-specific CTL effectors in vivo in a mouse model of established tumor and tumor regression following CD40 activation. We found that tumor-specific CTL were constitutively cross-armed in tumor-draining lymph nodes during tumor growth and that systemic CD40 activation did not alter CTL cross-arming in the tumor-draining lymph nodes. Rather, CD40 activation induced peripheral dissemination of tumor-specific CTL effectors that required continual CD40 stimulation to maintain peripheral CTL and tumor regression. These data indicate that CD40 activation enhances the peripheral survival of constitutively cross-armed CTL and that persistent CD4+ T cell signals are required for their long-term activity.
Eosinophil Adhesion to Cholinergic IMR-32 Cells Protects against Induced Neuronal Apoptosis
Authors: Morgan Ross K. , Kingham Paul J. , Walsh Marie Therese , Curran David C. , Durcan Niamh , McLean W. Graham , Costello Richard W.
Published: April 2014

Eosinophils release a number of mediators that are potentially toxic to nerve cells. However, in a number of inflammatory conditions, such as asthma and inflammatory bowel disease, it has been shown that eosinophils localize to nerves, and this is associated with enhanced nerve activity. In in vitro studies, we have shown that eosinophil adhesion via neuronal ICAM-1 leads to activation of neuronal NF-κB via an ERK1/2-dependent pathway. In this study, we tested the hypothesis that eosinophil adhesion to nerves promotes neural survival by protection from inflammation-associated apoptosis. Exposure of differentiated IMR-32 cholinergic nerve cells to IL-1β, TNF-α, and IFN-γ, or culture in serum-deprived medium, induced neuronal apoptosis, as detected by annexin V staining, caspase-3 activation, and DNA laddering. Addition of human eosinophils to IMR-32 nerve cells completely prevented all these features of apoptosis. The mechanism of protection by eosinophils was by an adhesion-dependent activation of ERK1/2, which led to the induced expression of the antiapoptotic gene bfl-1. Adhesion to nerve cells did not influence the expression of the related genes bax and bad. Thus, prevention of apoptosis by eosinophils may be a mechanism by which these cells regulate neural plasticity in the peripheral nervous system.
Impaired Receptor Editing in the Primary B Cell Repertoire of BASH-Deficient Mice
Authors: Hayashi Katsuhiko , Nojima Takuya , Goitsuka Ryo , Kitamura Daisuke
Published: April 2014

The editing of B cell Ag receptor (BCR) through successive rearrangements of Ig genes has been considered to be a major mechanism for the central B cell tolerance, which precludes appearance of self-reactive B cells, through studies using anti-self-Ig transgenic/knock-in mouse systems. However, contribution of the receptor editing in the development of the normal B cell repertoire remains unclear. In addition, the signaling pathway directing this event is unknown. In this study, we demonstrate that receptor editing in anti-DNA Ig knock-in mice is impaired in the absence of an adaptor protein BASH (BLNK/SLP-65) that is involved in BCR signaling. Remarkably, the supposed hallmarks of receptor editing such as Igλ chain expression, recombination sequence rearrangements at Igκ loci, and presence of in-frame VκJκ joins in the Igκ loci inactivated by the recombination sequence rearrangements, were all diminished in BASH-deficient mice with unmanipulated Ig loci. BCR ligation-induced Igλ gene recombination in vitro was also impaired in BASH-deficient B cells. Furthermore, the BASH-deficient mice showed an excessive Ab response to a DNA carrier immunization, suggesting the presence of unedited DNA-reactive B cells in the periphery. These results not only define a signaling pathway required for receptor editing but indicate that the BCR-signaled receptor editing indeed operates in the development of normal B cell repertoire and contributes to establishing the B cell tolerance.
Rescuing Melanoma Epitope-Specific Cytolytic T Lymphocytes from Activation-Induced Cell Death, by SP600125, an Inhibitor of JNK: Implications in Cancer Immunotherapy
Authors: Mehrotra Shikhar , Chhabra Arvind , Chattopadhyay Subhasis , Dorsky David I. , Chakraborty Nitya G. , Mukherji Bijay
Published: April 2014

Activation-induced cell death (AICD) as well as programmed cell death (PCD) serve to control the expansion of activated T cells to limit untoward side effects of continued effector responses by T cells and to maintain homeostasis. AICD of T cells in tumor immunotherapy can be counterproductive particularly if the activated T cells undergo apoptotic death after the very first secondary encounter of the specific epitope. We examined the extent to which tumor epitope-specific CTLs that are activated and expanded in an in vitro-matured dendritic cell-based primary stimulation protocol undergo AICD following their first secondary encounter of the cognate epitope. Using the MART-127–35 epitope as a prototype vaccine epitope, we also examined whether these CTLs could be rescued from AICD. Our results demonstrate that a substantial fraction of MART-127–35 epitope-specific primary CTLs undergo AICD upon the very first secondary encounter of the cognate epitope. The AICD in these CTLs is neither caspase dependent nor is it triggered by the extrinsic death signaling pathways (Fas, TNFR, etc.). These CTLs, interestingly, could be rescued from AICD by the JNK inhibitor, SP600125. We also found that SP600125 interferes with their IFN-γ response but does not block their cytolytic function. The rescued CTLs, however, regain their capacity to synthesize IFN-γ if continued in culture without the inhibitor. These observations have implications in tumor immunotherapy and in further studies for regulation of AICD in CTLs.
The Immunization Site of Cytokine-Secreting Tumor Cell Vaccines Influences the Trafficking of Tumor-Specific T Lymphocytes and Antitumor Efficacy against Regional Tumors
Authors: Chang Chun-Jung , Tai Kuo-Feng , Roffler Steve , Hwang Lih-Hwa
Published: April 2014

Tumor cells engineered to secrete cytokines, referred to as tumor cell vaccines, can often generate systemic antitumor immunity and, in many cases, cause tumor regression. We compared the efficacy of s.c. immunization or intrahepatic immunization of GM-CSF-expressing tumor cell vaccines on the growth of s.c. or orthotopic liver tumors. A chemically transformed hepatic epithelial cell line, GP7TB, derived from Fischer 344 rats, was used to generate tumor models and tumor cell vaccines. Our results demonstrated that two s.c. injections of an irradiated tumor cell vaccine significantly controlled the growth of s.c. tumors, but was completely ineffective against orthotopic liver tumors. Effector cell infiltration in liver tumors was markedly reduced compared with s.c. tumors. Enhanced apoptosis of some effector cells was observed in the liver tumors compared with the s.c. tumors. Furthermore, the T cells induced by s.c. immunization preferentially migrated to s.c. tumor sites, as demonstrated by adoptive transfer experiments. In contrast, intrahepatic immunization, using parental tumor cells admixed with adenoviruses carrying the GM-CSF gene, yielded significantly better therapeutic effects on the liver tumors than on the s.c. tumors. Adoptive transfer experiments further confirmed that the T cells induced by liver immunization preferentially migrated to the liver tumor sites. Our results demonstrate that distinct T cell populations are induced by different immunization routes. Thus, the homing behavior of T cells depends on the route of immunization and is an important factor determining the efficacy of immunotherapy for regional tumors.
Final Antigenic Melan-A Peptides Produced Directly by the Proteasomes Are Preferentially Selected for Presentation by HLA-A*0201 in Melanoma Cells
Authors: Chapatte Laurence , Servis Catherine , Valmori Danila , Burlet-Schiltz Odile , Dayer Johanna , Monsarrat Bernard , Romero Pedro , Lévy Frédéric
Published: April 2014

The melanoma-associated protein Melan-A contains the immunodominant CTL epitope Melan-A26/27–35/HLA-A*0201 against which a high frequency of T lymphocytes has been detected in many melanoma patients. In this study we show that the in vitro degradation of a polypeptide encompassing Melan-A26/27–35 by proteasomes produces both the final antigenic peptide and N-terminally extended intermediates. When human melanoma cells expressing the corresponding fragments were exposed to specific CTL, those expressing the minimal antigenic sequence were recognized more efficiently than those expressing the N-terminally extended intermediates. Using a tumor-reactive CTL clone, we confirmed that the recognition of melanoma cells expressing an N-terminally extended intermediate of Melan-A is inefficient. We demonstrated that the inefficient cytosolic trimming of N-terminally extended intermediates could offer a selective advantage for the preferred presentation of Melan-A peptides directly produced by the proteasomes. These results imply that both the proteasomes and postproteasomal peptidases limit the availability of antigenic peptides and that the efficiency of presentation may be affected by conditions that alter the ratio between fully and partially processed proteasomal products.
Antigen Targeting to CD11b Allows Efficient Presentation of CD4+ and CD8+ T Cell Epitopes and In Vivo Th1-Polarized T Cell Priming
Authors: Schlecht Géraldine , Loucka Jirina , Najar Hossain , Sebo Peter , Leclerc Claude
Published: April 2014

Bordetella pertussis adenylate cyclase (CyaA) is an invasive bacterial toxin that delivers its N-terminal catalytic domain into the cytosol of eukaryotic cells bearing the αMβ2 integrin (CD11b/CD18), such as myeloid dendritic cells. This allows use of engineered CyaA for targeted delivery of CD8+ T cell epitopes into the MHC class I pathway of APC and induction of robust and protective cytotoxic responses. In this study, we demonstrate that CyaA can efficiently codeliver both a CD8+ T cell epitope (OVA257–264) and a CD4+ T cell epitope (MalE100–114) into, respectively, the conventional cytosolic or endocytic routes of processing of murine bone marrow-derived dendritic cells. Upon CyaA delivery, a strong potentiation of the MalE100–114 CD4+ T cell epitope presentation is observed as compared with the MalE protein, which depends on CyaA interaction with its CD11b receptor and its subsequent clathrin-mediated endocytosis. In vivo, CyaA induces strong and specific Th1 CD4+ and CD8+ T cell responses against, respectively, the MalE100–114 and OVA257–264 epitopes. These results underscore the potency of CyaA for design of new vaccines.
Augmentation of T Cell Levels and Responses Induced by Androgen Deprivation
Authors: Roden Anja C. , Moser Michael T. , Tri Samuel D. , Mercader Maria , Kuntz Susan M. , Dong Haidong , Hurwitz Arthur A. , McKean David J. , Celis Esteban , Leibovich Bradley C. , Allison James P. , Kwon Eugene D.
Published: April 2014

Androgen has been implicated as a negative regulator of host immune function and a factor contributing to the gender dimorphism of autoimmunity. Conversely, androgen deprivation has been suggested to potentiate male host immunity. Studies have shown that removal of androgen in postpubertal male mice produces an increase in size and cellularity of primary and peripheral lymphoid organs, and enhances a variety of immune responses. Yet, few details are known about the effect of androgen removal on T cell-mediated immunity. In this study, we demonstrate two pronounced and independent alterations in T cell immunity that occur in response to androgen deprivation, provided by castration, in postpubertal male mice. First, we show that levels of T cells in peripheral lymphoid tissues of mice are increased by androgen deprivation. Second, T cells from these mice transiently proliferate more vigorously to TCR- and CD28-mediated costimulation as well as to Ag-specific activation. In addition, androgen deprivation accelerates normalization of host T and B cell levels following chemotherapy-induced lymphocyte depletion. Such alterations induced by androgen deprivation may have implications for enhancing immune responses to immunotherapy and for accelerating the recovery of the immune system following chemotherapy.
A General Survey of Thymocyte Differentiation by Transcriptional Analysis of Knockout Mouse Models
Authors: Puthier Denis , Joly Florence , Irla Magali , Saade Murielle , Victorero Geneviève , Loriod Béatrice , Nguyen Catherine
Published: April 2014

The thymus is the primary site of T cell lymphopoiesis. To undergo proper differentiation, developing T cells follow a well-ordered genetic program that strictly depends on the heterogeneous and highly specialized thymic microenvironment. In this study, we used microarray technology to extensively describe transcriptional events regulating αβ T cell fate. To get an integrated view of these processes, both whole thymi from genetically engineered mice together with purified thymocytes were analyzed. Using mice exhibiting various transcriptional perturbations and developmental blockades, we performed a transcriptional microdissection of the organ. Multiple signatures covering both cortical and medullary stroma as well as various thymocyte maturation intermediates were clearly defined. Beyond the definition of histological and functional signatures (proliferation, rearrangement), we provide the first evidence that such an approach may also highlight the complex cross-talk events that occur between maturing T cells and stroma. Our data constitute a useful integrated resource describing the main gene networks set up during thymocyte development and a first step toward a more systematic transcriptional analysis of genetically modified mice.
B Cells Expressing Bcl-2 and a Signaling-Impaired BAFF-Specific Receptor Fail to Mature and Are Deficient in the Formation of Lymphoid Follicles and Germinal Centers
Authors: Rahman Ziaur S. M. , Manser Tim
Published: April 2014

The TNF family cytokine B cell-activating factor belonging to the TNF family (BAFF) (BLyS) plays a fundamental role in regulating peripheral B cell survival and homeostasis. A BAFF-specific receptor (BAFF-R; BR3) appears to mediate these functions via activation of the NF-κB2 pathway. Signaling by the BAFF-R is also required to sustain the germinal center (GC) reaction. Engagement of this receptor results in the induction of Bcl-2, suggesting that this antiapoptotic factor acts downstream of the BAFF-R and NF-κB2 pathway to promote peripheral B cell survival during primary and Ag-driven development. To test this idea, we created lines of mice coexpressing a Bcl-2 transgene and a signaling-deficient form of the BAFF-R derived from the B lymphopenic A/WySnJ strain. Surprisingly, although dramatically elevated numbers of B cells accumulate in the periphery of these mice, these B cells exhibit extremely perturbed primary development, formation of lymphoid microenvironments, and GC and IgG responses. Moreover, mice expressing the bcl-2 transgene alone display a loss of marginal zone B cells, an expansion of follicular B cells that appear immature, and alterations of the GC reaction. These results suggest that the BAFF-R and Bcl-2 regulate key and nonoverlapping aspects of peripheral B cell survival and development.
Long Distance Control of MHC Class II Expression by Multiple Distal Enhancers Regulated by Regulatory Factor X Complex and CIITA
Authors: Krawczyk Michal , Peyraud Nicolas , Rybtsova Natalia , Masternak Krzysztof , Bucher Philipp , Barras Emmanuèle , Reith Walter
Published: April 2014

MHC class II (MHC-II) genes are regulated by an enhanceosome complex containing two gene-specific transcription factors, regulatory factor X complex (RFX) and CIITA. These factors assemble on a strictly conserved regulatory module (S-X-X2-Y) found immediately upstream of the promoters of all classical and nonclassical MHC-II genes as well as the invariant chain (Ii) gene. To identify new targets of RFX and CIITA, we developed a computational approach based on the unique and highly constrained architecture of the composite S-Y motif. We identified six novel S′-Y′ modules situated far away from the promoters of known human RFX- and CIITA-controlled genes. Four are situated at strategic positions within the MHC-II locus, and two are found within the Ii gene. These S′-Y′ modules function as transcriptional enhancers, are bona fide targets of RFX and CIITA in B cells and IFN-γ-induced cells, and induce broad domains of histone hyperacetylation. These results reveal a hitherto unexpected level of complexity involving long distance control of MHC-II expression by multiple distal regulatory elements.
HIV-1 Tat-Mediated Effects on Focal Adhesion Assembly and Permeability in Brain Microvascular Endothelial Cells
Authors: Avraham Hava Karsenty , Jiang Shuxian , Lee Tae-Hee , Prakash Om , Avraham Shalom
Published: April 2014

The blood-brain barrier (BBB) is a network formed mainly by brain microvascular endothelial cells (BMECs). The integrity of the BBB is critical for brain function. Breakdown of the BBB is commonly seen in AIDS patients with HIV-1-associated dementia despite the lack of productive HIV infection of the brain endothelium. The processes by which HIV causes these pathological conditions are not well understood. In this study we characterized the molecular mechanisms by which Tat mediates its pathogenic effects in vitro on primary human BMECs (HBMECs). Tat treatment of HBMECs stimulated cytoskeletal organization and increased focal adhesion sites compared with control cells or cells treated with heat-inactivated Tat. Pretreatment with Tat Abs or with the specific inhibitor SU-1498, which interferes with vascular endothelial growth factor receptor type 2 (Flk-1/KDR) phosphorylation, blocked the ability of Tat to stimulate focal adhesion assembly and the migration of HBMECs. Focal adhesion kinase (FAK) was tyrosine-phosphorylated by Tat and was found to be an important component of focal adhesion sites. Inhibition of FAK by the dominant interfering mutant form, FAK-related nonkinase, significantly blocked HBMEC migration and disrupted focal adhesions upon Tat activation. Furthermore, HIV-Tat induced permeability changes in HBMECs in a time-dependent manner. Tat also impaired BBB permeability, as observed in HIV-1 Tat transgenic mice. These studies define a mechanism for HIV-1 Tat in focal adhesion complex assembly in HBMECs via activation of FAK, leading to cytoskeletal reorganization and permeability changes.
Enhancer Role of STAT5 in CD2 Activation of IFN-γ Gene Expression
Authors: Gonsky Rivkah , Deem Richard L. , Bream Jay , Young Howard A. , Targan Stephan R.
Published: April 2014

IFN-γ is an important immunoregulatory protein with tightly controlled expression in activated T and NK cells. Three potential STAT binding regions have been recognized within the IFN-γ promoter: 1) an IL-12-mediated STAT4 binding site at −236 bp; 2) a newly identified IL-2-induced STAT5 binding element at −3.6 kb; and 3) CD2-mediated STAT1 and STAT4 binding to an intronic element in mucosal T cells. However, functional activation of these sites remains unclear. In this study we demonstrate CD2-mediated activation of the newly characterized −3.6-kb IFN-γ STAT5 binding region. CD2 signaling of human PBMC results in activation of the −3.6-kb IFN-γ promoter, whereas mutation of the −3.6-kb STAT5 site attenuates promoter activity. Functional activation is accompanied by STAT5A but little STAT5B nucleoprotein binding to the IFN-γ STAT5 site, as determined by competition and supershift assays. STAT5 activation via CD2 occurs independent of IL-2. Western and FACS analysis shows increased phospho-STAT5 following CD2 signaling. AG490, a tyrosine kinase inhibitor affecting Jak proteins, inhibits CD2-mediated IFN-γ mRNA expression, secretion, and nucleoprotein binding to the IFN-γ STAT5 site in a dose-dependent fashion. This report is the first to describe CD2-mediated activation of STAT5 and supports STAT5 involvement in regulation of IFN-γ expression.