bluuebunny/crossref_metadata_2025 huggingface dataset:
Fas-Mediated Apoptosome Formation Is Dependent on Reactive Oxygen Species Derived from Mitochondrial Permeability Transition in Jurkat Cells
Authors: Sato Tsutomu , Machida Takuro , Takahashi Sho , Iyama Satoshi , Sato Yasushi , Kuribayashi Kageaki , Takada Kohichi , Oku Takatomi , Kawano Yutaka , Okamoto Tetsuro , Takimoto Rishu , Matsunaga Takuya , Takayama Tetsuji , Takahashi Minoru , Kato Junji , Niitsu Yoshiro
Published: April 2014

Generation of reactive oxygen species (ROS) and activation of caspase cascade are both indispensable in Fas-mediated apoptotic signaling. Although ROS was presumed to affect the activity of the caspase cascade on the basis of findings that antioxidants inhibited the activation of caspases and that the stimulation of ROS by itself activated caspases, the mechanism by which these cellular events are integrated in Fas signaling is presently unclear. In this study, using human T cell leukemia Jurkat cells as well as an in vitro reconstitution system, we demonstrate that ROS are required for the formation of apoptosome. We first showed that ROS derived from mitochondrial permeability transition positively regulated the apoptotic events downstream of mitochondrial permeability transition. Then, we revealed that apoptosome formation in Fas-stimulated Jurkat cells was clearly inhibited by N-acetyl-l-cysteine and manganese superoxide dismutase by using both the immunoprecipitation and size-exclusion chromatography methods. To confirm these in vivo findings, we next used an in vitro reconstitution system in which in vitro-translated apoptotic protease-activating factor 1 (Apaf-1), procaspase-9, and cytochrome c purified from human placenta were activated by dATP to form apoptosome; the formation of apoptosome was markedly inhibited by reducing reagents such as DTT or reduced glutathione (GSH), whereas hydrogen peroxide prevented this inhibition. We also found that apoptosome formation was substantially impaired by GSH-pretreated Apaf-1, but not GSH-pretreated procaspase-9 or GSH-pretreated cytochrome c. Collectively, these results suggest that ROS plays an essential role in apoptosome formation by oxidizing Apaf-1 and the subsequent activation of caspase-9 and -3.
Deficiency of CD11b or CD11d Results in Reduced Staphylococcal Enterotoxin-Induced T Cell Response and T Cell Phenotypic Changes
Authors: Wu Huaizhu , Rodgers John R. , Perrard Xiao-Yuan Dai , Perrard Jerry L. , Prince Joseph E. , Abe Yasunori , Davis Beckley K. , Dietsch Greg , Smith C. Wayne , Ballantyne Christie M.
Published: April 2014

The β2 integrin CD11a is involved in T cell-APC interactions, but the roles of CD11b, CD11c, and CD11d in such interactions have not been examined. To evaluate the roles of each CD11/CD18 integrin in T cell-APC interactions, we tested the ability of splenocytes of CD11-knockout (KO) mice to respond to staphylococcal enterotoxins (SEs), a commonly used superantigen. The defect in T cell proliferation with SEA was more severe in splenocytes from mice deficient in CD18, CD11b, or CD11d than in CD11a-deficient splenocytes, with a normal response in CD11c-deficient splenocytes. Mixing experiments showed that the defect of both CD11b-KO and CD11d-KO splenocytes was, unexpectedly, in T cells rather than in APC. Cytometric analysis failed to detect CD11b or CD11d on resting or activated T cells or on thymocytes of wild-type adult mice, nor did Abs directed to these integrins block responses in culture, suggesting that T cells educated in CD11b-KO or CD11d-KO mice were phenotypically altered. Consistent with this hypothesis, T cells from CD11b-KO and CD11d-KO splenocytes exhibited reduced intensity of CD3 and CD28 expression and decreased ratios of CD4/CD8 cells, and CD4+ T cells were reduced among CD11b-KO and CD11d-KO thymocytes. CD11b and CD11d were coexpressed on a subset of early wild-type fetal thymocytes. We postulate that transient thymocyte expression of both CD11b and CD11d is nonredundantly required for normal thymocyte and T cell development, leading to phenotypic changes in T cells that result in the reduced response to SE stimulation.
CCR5 Regulates High Dose Oral Tolerance by Modulating CC Chemokine Ligand 2 Levels in the GALT
Authors: DePaolo R. William , Lathan Rashida , Karpus William J.
Published: April 2014

Oral tolerance is an immunomodulatory mechanism used by gut tissues to induce systemic tolerance to ingested proteins. In models of disease, such as experimental autoimmune encephalomyelitis, oral tolerance has been used to protect against paralysis induced by immunization with myelin proteins. Previous work in our laboratory has shown a role for the chemokine, CCL2, and its receptor in the induction of high dose oral tolerance. In the present study, we report that two CCR5 ligands, CCL4 and CCL5, are expressed in gut tissues after Ag feeding. CCR5−/− mice were unable to be tolerized by feeding a high dose of Ag and were not protected from developing experimental autoimmune encephalomyelitis. Moreover, CCR5−/− mice did not display cytokine deviation as normally seen after high dose oral Ag. Using a selective CCR5 antagonist, methionine-RANTES, CCL2 expression was inhibited, resulting in enhanced IL-12 production and the inability for mice treated with methionine-RANTES to become orally tolerized. This current study suggests that CCR5 ligands may function to modulate CCL2 levels in the gut after Ag feeding, promoting a cellular environment that favors tolerance rather than immunity.
Epstein-Barr Virus Promotes Human Monocyte Survival and Maturation through a Paracrine Induction of IFN-α
Authors: Salek-Ardakani Shahram , Lyons Stephen A. , Arrand John R.
Published: April 2014

The role of monocytes and macrophages during EBV infection is not clear. The interaction of EBV with human monocytes was investigated in terms of cell survival and morphological and phenotypic changes to gain a better understanding of the role of these cells during EBV infection. We show that EBV infection of PBMCs rescues monocytes from undergoing spontaneous apoptosis and dramatically enhances their survival. Results obtained with heat-inactivated virus, neutralizing anti-EBV mAb 72A1 and recombinant gp350, suggest that enhancement of viability by EBV requires both infectious virus and interaction between gp350 and its receptor. IFN-α either secreted within 24 h from PBMCs upon infection with EBV or exogenously added to unstimulated monocytes inhibited spontaneous apoptosis, indicating that induction of IFN-α is an early important survival signal responsible for the delay in the apoptosis of monocytes. EBV infection also induced acute maturation of monocytes to macrophages with morphological and phenotypic characteristics of potent APCs. Monocytes exposed to EBV became larger in size with increased granularity and expressed considerably higher levels of membrane HLA classes I and II, ICAM-1, CD80, CD86, and CD40 compared with uninfected cultures. These observations provide the first immunoregulatory links among EBV, IFN-α, and monocyte survival and maturation and importantly raise the possibility that these cells may serve as a vehicle for the dissemination of the virus as well as being active participants in eliciting anti-EBV T cell responses during acute infection.
Differences in Signaling Molecule Organization between Naive and Memory CD4+ T Lymphocytes
Authors: Watson Andrew R. O. , Lee William T.
Published: April 2014

The immunological synapse is a highly organized complex formed at the junction between Ag-specific T cells and APCs as a prelude to cell activation. Although its exact role in modulating T cell signaling is unknown, it is commonly believed that the immunological synapse is the site of cross-talk between the T cell and APC (or target). We have examined the synapses formed by naive and memory CD4 cells during Ag-specific cognate interactions with APCs. We show that the mature immunological synapse forms more quickly during memory T cell activation. We further show that the composition of the synapse found in naive or memory cell conjugates with APCs is distinct with the tyrosine phosphatase, CD45, being a more integral component of the mature synapses formed by memory cells. Finally, we show that signaling molecules, including CD45, are preassociated in discrete, lipid-raft microdomains in resting memory cells but not in naive cells. Thus, enhanced memory cell responses may be due to intrinsic properties of signaling molecule organization.
Human Complement Factor I Does Not Require Cofactors for Cleavage of Synthetic Substrates
Authors: Tsiftsoglou Stefanos A. , Sim Robert B.
Published: April 2014

Complement factor I (fI) plays a major role in the regulation of the complement system. It circulates in an active form and has very restricted specificity, cleaving only C3b or C4b in the presence of a cofactor such as factor H (fH), complement receptor type 1, membrane cofactor protein, or C4-binding protein. Using peptide-7-amino-4-methylcoumarin derivatives, we investigated the substrate specificity of fI. There is no previous report of synthetic substrate cleavage by fI, but five substrates were found in this study. A survey of 15 substrates and a range of inhibitors showed that fI has specificity similar to that of thrombin, but with much lower catalytic activity than that of thrombin. fI amidolytic activity has a pH optimum of 8.25, typical of serine proteases and is insensitive to ionic strength. This is in contrast to its proteolytic activity within the fI-C3b-fH reaction, in which the pH optimum for C3b cleavage is <5.5 and the reaction rate is highly dependent on ionic strength. The rate of cleavage of tripeptide 7-amino-4-methylcoumarins by fI is unaffected by the presence of fH or C3(NH3). The amidolytic activity is inhibited by the synthetic thrombin inhibitor Z-d-Phe-Pro-methoxypropylboroglycinepinanediol ester, consistent with previous reports, and by benzenesulfonyl fluorides such as Pefabloc SC. Suramin inhibits fI directly at concentration of 1 mM. Within a range of metal ions tested, only Cr2+ and Fe3+ were found to inhibit both the proteolytic and amidolytic activity of fI.
Opioid Antagonist Naltrexone Disrupts Feedback Interaction between μ and δ Opioid Receptors in Splenocytes to Prevent Alcohol Inhibition of NK Cell Function
Authors: Boyadjieva Nadka I. , Chaturvedi Kirti , Poplawski Michael M. , Sarkar Dipak K.
Published: April 2014

Naltrexone, an opioid antagonist, has been used in clinical trials to treat alcoholism. As the opioid peptides β-endorphin and enkephalin increase splenic NK cell function in laboratory animals, it is anticipated that naltrexone treatment will cause immunosuppression. However, we report in this study that chronic naltrexone administration in laboratory rats increases the cytolytic activity of NK cells. It also prevents alcohol’s suppressive effect on these cells. We identified that, in the splenocytes, δ opioid receptor expression is tightly controlled by negative feedback regulation of μ opioid receptors. Naltrexone disrupts this feedback control by reducing μ opioid receptor function, thereby up-regulating δ opioid receptor binding, which results in an enhanced NK cell cytolytic response to δ opioid receptor ligands. We conclude that naltrexone, which has been shown to be a promising agent for the clinical management of alcoholism, may have potential use in the treatment of immune deficiency in alcoholic and nonalcoholic patients.
Listeria monocytogenes as a Vaccine Vector: Virulence Attenuation or Existing Antivector Immunity Does Not Diminish Therapeutic Efficacy
Authors: Starks Holly , Bruhn Kevin W. , Shen Hao , Barry Ronald A. , Dubensky Thomas W. , Brockstedt Dirk , Hinrichs David J. , Higgins Darren E. , Miller Jeffrey F. , Giedlin Martin , Bouwer H. G. Archie
Published: April 2014

The bacterium L. monocytogenes is a proposed vaccine carrier based upon the observation that this pathogen replicates within the intracytoplasmic environment facilitating delivery of Ag to the endogenous Ag processing and presentation pathway with subsequent stimulation of peptide specific MHC class I-restricted CD8+ effector cells. In this report, we evaluate virulence-attenuated strains of Listeria monocytogenes as vaccine vectors and examine whether existing antivector (antilisterial) immunity limits or alters its efficacy as a therapeutic cancer vaccine. Following immunization with virulence-attenuated mutants, we found that the effectiveness of L. monocytogenes as a recombinant cancer vaccine remains intact. In addition, we found that antibiotic treatment initiated 24 or 36 h following therapeutic immunization with recombinant L. monocytogenes allows full development of the antitumor response. We also demonstrate that the vaccine vector potential of L. monocytogenes is not limited in animals with existing antilisterial immunity. For these latter studies, mice previously immunized with wild-type L. monocytogenes were infused with melanoma cells and then 5 days later challenged with recombinant tumor Ag expressing L. monocytogenes. Collectively, these results add additional support for the use of L. monocytogenes as a vaccine vector and underscore its potential to be used repeatedly for stimulation of recall responses concomitant with primary cell-mediated responses to newly delivered heterologous tumor-associated epitopes.
Identification of Neutrophil Granule Protein Cathepsin G as a Novel Chemotactic Agonist for the G Protein-Coupled Formyl Peptide Receptor
Authors: Sun Ronghua , Iribarren Pablo , Zhang Ning , Zhou Ye , Gong Wanghua , Cho Edward H. , Lockett Stephen , Chertov Oleg , Bednar Filip , Rogers Thomas J. , Oppenheim Joost J. , Wang Ji Ming
Published: April 2014

The antimicrobial and proinflammatory neutrophil granule protein cathepsin G (CaG) has been reported as a chemoattractant for human phagocytic leukocytes by using a putative G protein coupled receptor. In an effort to identify potential CaG receptor(s), we found that CaG-induced phagocyte migration was specifically attenuated by the bacterial chemotactic peptide fMLP, suggesting these two chemoattractants might share a receptor. In fact, CaG chemoattracts rat basophilic leukemia cells (RBL cells) expressing the high affinity human fMLP receptor FPR, but not parental RBL cells or cells transfected with other chemoattractant receptors. In addition, a specific FPR Ab and a defined FPR antagonist, cyclosporin H, abolished the chemotactic response of phagocytes and FPR-transfected cells to CaG. Furthermore, CaG down-regulated the cell surface expression of FPR in association with receptor internalization. Unlike fMLP, CaG did not induce potent Ca2+ flux and was a relatively weaker activator of MAPKs through FPR. Yet CaG activated an atypical protein kinase C isozyme, protein kinase Cζ, which was essential for FPR to mediate the chemotactic activity of CaG. Thus, our studies identify CaG as a novel, host-derived chemotactic agonist for FPR and expand the functional scope of this receptor in inflammatory and immune responses.
The Major Surface Protein of Wolbachia Endosymbionts in Filarial Nematodes Elicits Immune Responses through TLR2 and TLR4
Authors: Brattig Norbert W. , Bazzocchi Chiara , Kirschning Carsten J. , Reiling Norbert , Büttner Dietrich W. , Ceciliani Fabrizio , Geisinger Frank , Hochrein Hubertus , Ernst Martin , Wagner Hermann , Bandi Claudio , Hoerauf Achim
Published: April 2014

More than 150 million humans in tropical countries are infected by filarial nematodes which harbor intracellular bacterial endosymbionts of the genus Wolbachia (Rickettsiales). These bacteria have been implicated in adverse effects of drug treatment in filariasis. The present study provides evidence that purified major Wolbachia surface protein (rWSP) acts as an inducer of the innate immune system through TLR2 and TLR4: 1) recombinant, stringently purified rWSP elicited the release of TNF-α, IL-12, and IL-8 from cultured blood cells of both Onchocerca volvulus-infected and uninfected people; 2) the inflammatory response to rWSP challenge was TLR2- and TLR4-dependent as demonstrated with TLR-transfected fibroblastoid cells, as well as macrophages and dendritic cells from functional TLR-deficient mice; 3) blood cells of onchocerciasis patients exposed to rWSP also generated down-regulating mediators IL-10 and PGE2 after 6 days of culture; 4) furthermore, rWSP-reactive IgG1 Abs were present in sera of O. volvulus-infected people but not in those of uninfected Europeans. The lack of rWSP-reactive IgE and IgG4 in serum indicated a bias toward a Th1-type adaptive immune response. Abs against rWSP stained endobacteria in living and degenerating adult O. volvulus filariae, tissue microfilariae and host tissue macrophages that apparently had engulfed microfilariae. Thus, filarial helminths, through products of their endobacteria such as WSP, acquire characteristics of a typical microbial pathogen inducing immune responses via TLR2 and TLR4.
Incomplete Humoral Immunity against Hepatitis C Virus Is Linked with Distinct Recognition of Putative Multiple Receptors by E2 Envelope Glycoprotein
Authors: Heo Tae-Hwe , Chang Jae-Hoon , Lee Jae-Woo , Foung Steven K. H. , Dubuisson Jean , Kang Chang-Yuil
Published: April 2014

Little is known about the role of the humoral immune response to hepatitis C virus (HCV). This study provides molecular evidence for the mechanism by which neutralizing Abs from the sera of chronic HCV patients have lower inhibitory activities against the binding of HCV E2 envelope protein to human hepatoma cell lines than to a lymphoma cell line. E2 binds to several putative receptors, specifically human CD81; human scavenger receptor, class B, type 1; and heparan sulfate. We have shown that E2 binds to target cells via these receptors in a noncompetitive manner. Thus, incomplete inhibition of one of the receptors leads to only a partial E2 blockade and, possibly, evasion of the host immune response. We demonstrated that the difference in and reduction of inhibition was closely related to impaired blockade of E2 binding to scavenger receptor, class B, type 1, and heparan sulfate. We have also shown that soluble E2 protein binds to multiple soluble receptors via separate binding domains on E2, providing further evidence for the distinct recognition of multiple cellular receptors by E2. This report suggests a novel finding that biased humoral immune responses to HCV E2 might provide an alternative mechanism for viral escape without the involvement of mutation. Additionally, our data give crucial consideration to the development of HCV vaccines that stimulate protective humoral immune responses.
The Rapidity with Which Virus-Specific CD8+ T Cells Initiate IFN-γ Synthesis Increases Markedly over the Course of Infection and Correlates with Immunodominance
Authors: Liu Fei , Whitton J. Lindsay , Slifka Mark K.
Published: April 2014

Primary CD8+ T cell responses play a major role in controlling infection by many viruses, and CD8+ memory T cells can confer immunity to virus challenge. In this study we report that for many epitope-specific CD8+ T cell populations, the regulation of an important effector molecule, IFN-γ, changes dramatically over the course of infection. During the acute phase of infection, many CD8+ T cells exhibit a significant lag before producing IFN-γ in response to Ag contact; in contrast, the onset of IFN-γ production by memory cells of the same epitope specificity is markedly accelerated. The biological consequences of this improved responsiveness are manifold. Moreover, during the acute phase of the CD8+ T cell response when immunodominance is being established, there is a strong correlation (p = 0.0002) between the abundance of each epitope-specific T cell population and the rapidity with which it initiates IFN-γ synthesis. Previous studies have indicated that IFN-γ plays a critical role in determining the immunodominance hierarchy of an on-going T cell response, and in this report we present evidence for an underlying mechanism: we propose that the CD8+ T cells that most rapidly initiate IFN-γ production may be at a selective advantage, permitting them to dominate the developing T cell response.
Origin and Fate of Lymphocytic Choriomeningitis Virus-Specific CD8+ T Cells Coexpressing the Inhibitory NK Cell Receptor Ly49G2
Authors: Peacock Craig D. , Welsh Raymond M.
Published: April 2014

CD8+ T cells that coexpress the inhibitory NK cell receptor, Ly49G2 (G2), are present in immunologically naive C57BL/6 mice but display Ags found on memory T cells. To assess how G2+CD8+ cells relate to bona fide memory cells, we examined the origin and fate of lymphocytic choriomeningitis virus (LCMV)-induced G2+CD8+ cells. During early (day 4) acute LCMV infection, both G2+ and G2−CD8+ T cell subsets underwent an attrition in number and displayed an activation (CD69high1B11highCD62Llow) phenotype. By day 8, both subsets synthesized IFN-γ in response to immunodominant LCMV peptides, though the expansion of G2+ cells was less than that of G2− cells. Adoptive transfer experiments with purified G2− or G2+CD8+ cells from naive mice indicated that the LCMV-specific G2+ subset was derived from a pre-existing G2+ population and not generated from G2− cells responding to LCMV infection. Their participation in the LCMV-specific T cell response increased with age, reflecting an increase in the size of the pre-existing G2+ pool. Following establishment of stable LCMV memory, the proportion of CD8+ cells coexpressing G2 was reduced in comparison to naive controls, presumably due to displacement by G2− LCMV-specific memory cells. LCMV-specific G2+ cells were present in the memory pool, but at low frequencies, and they did not exhibit the typical phenotypic changes of reactivation during secondary challenge. We suggest that G2+CD8+ cells represent a cell lineage distinct from bona fide memory T cells, but that they can participate in an acute virus-specific T cell response.
Differential Gene Expression Identifies Novel Markers of CD4+ and CD8+ T Cell Activation Following Stimulation by Mycobacterium tuberculosis
Authors: Cliff Jacqueline M. , Andrade Iryna N. J. , Mistry Rohit , Clayton Christopher L. , Lennon Mark G. , Lewis Alan P. , Duncan Ken , Lukey Pauline T. , Dockrell Hazel M.
Published: April 2014

T cell activation in response to antigenic stimulation is a complex process, involving changes in the expression level of a large number of genes. We have used cDNA array technology to characterize the differences in gene expression between human CD4+ and CD8+ T cells. PBMC from six healthy donors were stimulated with live Mycobacterium tuberculosis, and the gene expression profiles of each donor’s CD4+ and CD8+ T cells were analyzed separately. ANOVA revealed 518 genes that were consistently differentially expressed between CD4+ and CD8+ T cells. These differentially expressed genes include a combination of well-known, previously characterized genes with a range of biological functions and unknown in silico predicted hypothetical genes. Where possible, the novel genes have been characterized using bioinformatics, and putative transcription factors, signaling molecules, transmembrane, and secreted factors have been identified. A subset of these differentially expressed genes could be exploited as markers of CD4+ and CD8+ T cell activation for use in vaccine trials. These observed differences in the gene expression profile of CD4+ and CD8+ T cells following activation by a human pathogen contribute to an increased understanding of T cell activation and differentiation and the roles these T cell subsets may play in immunity to infection.
Dendritic Cell Trafficking and Antigen Presentation in the Human Immune Response toMycobacterium tuberculosis
Authors: Marino Simeone , Pawar Santosh , Fuller Craig L. , Reinhart Todd A. , Flynn JoAnne L. , Kirschner Denise E.
Published: April 2014

Mycobacterium tuberculosis (Mtb) is an extraordinarily successful human pathogen, one of the major causes of death by infectious disease worldwide. A key issue for the study of tuberculosis is to understand why individuals infected with Mtb experience different clinical outcomes. To better understand the dynamics of Mtb infection and immunity, we coupled nonhuman primate experiments with a mathematical model we previously developed that qualitatively and quantitatively captures important processes of cellular priming and activation. These processes occur between the lung and the nearest draining lymph node where the key cells mediating this process are the dendritic cells (DC). The nonhuman primate experiments consist of bacteria and cell numbers from tissues of 17 adult cynomolgus macaques (Macaca fascicularis) that were infected with Mtb strain Erdman (∼25 CFU/animal via bronchoscope). The main result of this work is that delays in either DC migration to the draining lymph node or T cell trafficking to the site of infection can alter the outcome of Mtb infection, defining progression to primary disease or latent infection and reactivated tuberculosis. Our results also support the idea that the development of a new generation of treatment against Mtb should optimally elicit a fast DC turnover at the site of infection, as well as strong activation of DCs for maximal Ag presentation and production of key cytokines. This will induce the most protective T cell response.
TLR3-, TLR7-, and TLR9-Mediated Production of Proinflammatory Cytokines and Chemokines from Murine Connective Tissue Type Skin-Derived Mast Cells but Not from Bone Marrow-Derived Mast Cells
Authors: Matsushima Hironori , Yamada Nobuo , Matsue Hiroyuki , Shimada Shinji
Published: April 2014

Recent studies have revealed that murine bone marrow-derived cultured mast cells (BMMC), which are phenotypically immature mast cells, express functional TLR2 and TLR4 that recognize distinct pathogen-associated molecules. However, it remains relatively uncertain whether mast cells express other TLR. We recently established a method to obtain large numbers of murine fetal skin-derived cultured mast cells (FSMC); these cells exhibit important features of connective tissue type mast cells. Working with FSMC and BMMC, the TLR mRNA expression profiles were compared between both cell types. Although TLR2 and TLR4 mRNA were detected in both cells at comparable levels, TLR3, TLR7, and TLR9 mRNA were expressed by FSMC at higher levels than by BMMC, suggesting distinct TLR expression profiles among different mast cell populations. With respect to their functional aspects, FSMC, but not BMMC, dose dependently produced proinflammatory cytokines (TNF-α and IL-6) and chemokines (RANTES, MIP-1α, and MIP-2) in response to poly(I:C), R-848, and CpG oligodeoxynucleotide, which are TLR3, TLR7, and TLR9 activators, respectively. Interestingly, these TLR activators failed to induce degranulation and IL-13 production by both mast cells, although peptidoglycan and LPS (TLR2 and TLR4 activators, respectively) induced IL-13 production by both cells. Mast cells, thus, may have potential to recruit other immune cells to the infected sites by responding to various bacterial and viral components through TLR signaling pathways, presumably being involved in initiating innate immunity and subsequently linking innate and acquired immune responses.
Phosphatidylserine Receptor-Mediated Recognition of Archaeosome Adjuvant Promotes Endocytosis and MHC Class I Cross-Presentation of the Entrapped Antigen by Phagosome-to-Cytosol Transport and Classical Processing
Authors: Gurnani Komal , Kennedy Jessica , Sad Subash , Sprott G. Dennis , Krishnan Lakshmi
Published: April 2014

Archaeal isopranoid glycerolipid vesicles (archaeosomes) serve as strong adjuvants for cell-mediated responses to entrapped Ag. We analyzed the processing pathway of OVA entrapped in archaeosomes composed of Methanobrevibacter smithii lipids, high in archaetidylserine (OVA-archaeosomes). In vitro, OVA-archaeosomes stimulated spleen cells from OVA-TCR-transgenic mice, D011.10 (CD4+ cells expressing OVA323–339 TCR) or OT1 (>90% CD8+ OVA257–264 cells), indicating both MHC class I and II presentations. In vivo, when naive (Thy1.2+) CFSE-labeled OT1 cells were transferred into OVA-archaeosome-immunized Thy 1.1+ recipient mice, there was profound accumulation and cycling of donor-specific cells, and differentiation of H-2KbOva257–264 CD8+ T cells into CD44highCD62Llow effectors. Both macrophages and dendritic cells (DCs) efficiently cross-presented OVA-archaeosomes on MHC class I. Blocking phagocytosis by phosphatidylserine-specific receptor agonists strongly inhibited MHC class I presentation of OVA-archaeosomes, whereas blocking mannose receptors or FcRs lacked effect, indicating specific recognition of the archaetidylserine head group of M. smithii lipids by APCs. In addition, inhibitors of endosomal acidification blocked MHC class I processing of OVA-archaeosomes, whereas endosomal protease inhibitors lacked effect, suggesting acidification-dependent phagosome-to-cytosol diversion. Proteasomal inhibitors blocked OVA-archaeosome MHC class I presentation, confirming cytosolic processing. Both in vitro and in vivo, OVA-archaeosome MHC class I presentation required TAP. Ag-free archaeosomes also activated DC costimulation and cytokine production, without overt inflammation. Phosphatidylserine-specific receptor-mediated endocytosis is a mechanism of apoptotic cell clearance and DCs cross-present Ags sampled from apoptotic cells. Our results reveal the novel ability of archaeosomes to exploit this mechanism for cytosolic MHC class I Ag processing, and provide an effective particulate vaccination strategy.
Increase in Hepatic NKT Cells in Leukocyte Cell-Derived Chemotaxin 2-Deficient Mice Contributes to Severe Concanavalin A-Induced Hepatitis
Authors: Saito Takeshi , Okumura Akinori , Watanabe Hisami , Asano Masahide , Ishida-Okawara Akiko , Sakagami Junko , Sudo Katsuko , Hatano-Yokoe Yoshimi , Bezbradica Jelena S. , Joyce Sebastian , Abo Toru , Iwakura Yoichiro , Suzuki Kazuo , Yamagoe Satoshi
Published: April 2014

Leukocyte cell-derived chemotaxin 2 (LECT2) was originally identified for its possible chemotactic activity against human neutrophils in vitro. It is a 16-kDa protein that is preferentially expressed in the liver. Its homologues have been widely identified in many vertebrates. Current evidence suggests that LECT2 may be a multifunctional protein like cytokines. However, the function of LECT2 in vivo remains unclear. To elucidate the role of this protein in vivo, we have generated LECT2-deficient (LECT2−/−) mice. We found that the proportion of NKT cells in the liver increased significantly in LECT2−/− mice, although those of conventional T cells, NK cells, and other cell types were comparable with those in wild-type mice. Consistent with increased hepatic NKT cell number, the production of IL-4 and IFN-γ was augmented in LECT2−/− mice upon stimulation with α-galactosylceramide, which specifically activates Vα14 NKT cells. In addition, NKT cell-mediated cytotoxic activity against syngeneic thymocytes increased in hepatic mononuclear cells obtained from LECT2−/− mice in vitro. Interestingly, the hepatic injury was exacerbated in LECT2−/− mice upon treatment with Con A, possibly because of the significantly higher expression of IL-4 and Fas ligand. These results suggest that LECT2 might regulate the homeostasis of NKT cells in the liver and might be involved in the pathogenesis of hepatitis.
A Structurally Available Encephalitogenic Epitope of Myelin Oligodendrocyte Glycoprotein Specifically Induces a Diversified Pathogenic Autoimmune Response
Authors: Bischof Felix , Bins Adriaan , Dürr Michael , Zevering Yinka , Melms Arthur , Kruisbeek Ada M.
Published: April 2014

Multiple sclerosis is an inflammatory disease of the CNS that involves immune reactivity against myelin oligodendrocyte glycoprotein (MOG), a type I transmembrane protein located at the outer surface of CNS myelin. The epitope MOG92–106 is a DR4-restricted Th cell epitope and a target for demyelinating autoantibodies. In this study, we show that the immune response elicited by immunization with this epitope is qualitatively different from immune responses induced by the well-defined epitopes myelin basic protein (MBP) 84–96 and proteolipid protein (PLP) 139–151. Mice with MOG92–106-, but not with MBP84–96- or PLP139–151-induced experimental autoimmune encephalomyelitis developed extensive B cell reactivity against secondary myelin Ags. These secondary Abs were directed against a set of encephalitogenic peptide Ags derived from MBP and PLP as well as a broad range of epitopes spanning the complete MBP sequence. The observed diversification of the B cell reactivity represents a simultaneous spread toward a broad range of antigenic epitopes and differs markedly from T cell epitope spreading that follows a sequential cascade. The Abs were of the isotypes IgG1 and IgG2b, indicating that endogenously recruited B cells receive help from activated T cells. In sharp contrast, B cell reactivity in MBP84–96- and PLP139–151-induced experimental autoimmune encephalomyelitis was directed against the disease-inducing Ag only. These data provide direct evidence that the nature of the endogenously acquired immune reactivity during organ-specific autoimmunity critically depends on the disease-inducing Ag. They further demonstrate that the epitope MOG92–106 has the specific capacity to induce a widespread autoimmune response.
Regulation of Cockroach Antigen-Induced Allergic Airway Hyperreactivity by the CXCR3 Ligand CXCL9
Authors: Thomas Molly S. , Kunkel Steven L. , Lukacs Nicholas W.
Published: April 2014

Allergic airway disease is characterized by a robust lymphocytic infiltrate, elaboration of Th2-type inflammatory mediators, pulmonary eosinophil accumulation, and airway hyperreactivity. The CXCR3 ligands, CXCL9 (monokine induced by IFN-γ) and CXCL10 (IFN-inducible protein, 10 kDa), are IFN-γ-inducible, Th1-type chemokines. As CXCL10 has been previously shown to participate in the modulation of allergic inflammation, we were interested in investigating the possible role that CXCL9 may play in this inflammatory response. Expression of CXCL9 was primarily identified in airway epithelial cells by immunohistochemical staining. Airway neutralization of CXCL9 at the time of allergen challenge significantly increased airway hyperreactivity, airway eosinophil accumulation, and IL-4 levels in the bronchoalveolar lavage while significantly decreasing airway levels of IL-12. In contrast, introduction of exogenous CXCL9 into the airway at the time of allergen challenge dramatically reduced airway hyper-reactivity and eosinophil accumulation. Moreover, pulmonary levels of IL-4 were significantly reduced, whereas levels of IL-12 were significantly increased, with exogenous CXCL9 treatment. In lymphocytes restimulated with CXCL9 and allergen in vitro, CXCL9 down-regulated IL-4 expression and up-regulated IFN-γ expression, suggesting that CXCL9 is able to direct activated lymphocytes toward a Th1-type phenotype. Additionally, CXCL9 was shown to inhibit CC chemokine ligand 11-induced eosinophil chemotaxis in in vitro assays. Taken together, our results demonstrate that the CXCR3 ligand CXCL9 is involved in regulation of the allergic response in the lung by regulation of lymphocyte activation and eosinophil recruitment.
Requirement for CD28 in the Effector Phase of Allergic Airway Inflammation
Authors: Kimzey Stephanie L. , Liu Pingfan , Green Jonathan M.
Published: April 2014

Central to the pathogenesis of allergic airway inflammation are the activation and differentiation of T lymphocytes. This process requires the participation of the CD28 costimulatory receptor. Blockade of CD28 has been demonstrated to prevent inflammation and airway hyperreactivity in a murine model of asthma. Whether this is due specifically to defects in initial T cell activation or whether effector responses are also impaired has not been determined. Using adoptive transfer studies of Ag-specific lymphocytes, we demonstrate that CD28 has a critical role in both the induction and effector phase of allergic airway inflammation. Transfer of in vitro activated and Th2-differentiated Ag-specific lymphocytes from wild-type hosts restored inflammation, but not tissue eosinophilia in CD28-deficient recipients. Furthermore, similarly activated and differentiated CD28-deficient lymphocytes were ineffective at mediating inflammation in wild-type recipients. Secondary cytokine and proliferative responses of activated Th2 cells were highly dependent on CD28 in vitro. Moreover, eosinophil recruitment to both the lung and peritoneum is impaired by the lack of CD28, suggesting a generalized defect in the ability of eosinophils to accumulate at sites of inflammation in vivo. These data identify a novel role for CD28 in the effector phase of allergic airway inflammation and suggest that inhibition of this pathway may be a useful therapeutic intervention in previously sensitized individuals.
Comparative Analysis of the CD19+ and CD138+ Cell Antibody Repertoires in the Cerebrospinal Fluid of Patients with Multiple Sclerosis
Authors: Ritchie Alanna M. , Gilden Donald H. , Williamson R. Anthony , Burgoon Mark P. , Yu Xiaoli , Helm Karen , Corboy John R. , Owens Gregory P.
Published: April 2014

Increased amounts of intrathecally synthesized IgG and oligoclonal bands have long been recognized as a hallmark of multiple sclerosis (MS). B cells and plasma cells are components of the inflammatory infiltrates in both active and chronic MS lesions, and increased numbers of these cells are present in MS cerebrospinal fluid (CSF). Single-cell RT-PCR was used to analyze both the CD19+ B cell and CD138+ plasma cell populations in CSF of two patients with clinically definite MS and of one MS patient whose CSF was obtained after a clinically isolated syndrome, but before the second episode. Sequence analysis of amplified IgG V region sequences identified the rearranged germline segments, extent of somatic mutation, and clonal relationships within and between the two cell populations in the three MS patients. Expanded B cell and plasma cell clones were detected in each MS CSF and in all three patients the CD138+ IgG repertoire was more restricted. However, little if any significant sequence overlap was observed between the CD19+ and CD138+ repertoires of each donor. Detection of plasma cell clones by single-cell PCR will facilitate the in vitro production of recombinant Abs useful in identifying disease-relevant Ags.
γδ T Cells Enhance the Expression of Experimental Autoimmune Encephalomyelitis by Promoting Antigen Presentation and IL-12 Production
Authors: Odyniec Artur , Szczepanik Marian , Mycko Marcin P. , Stasiolek Mariusz , Raine Cedric S. , Selmaj Krzysztof W.
Published: April 2014

Using an adoptive transfer model of experimental autoimmune encephalomyelitis (EAE) induced by myelin basic protein (MBP)-reactive lymph node cells (LNC), we have shown that depletion of γδ T cells from LNC resulted in diminished severity of EAE in recipient mice, both clinically and histopathologically. The reduced potency of γδ T cell-depleted LNC to induce EAE correlated with decreased cell proliferation in response to MBP. The γδ T cell effect upon the threshold of MBP-induced LNC proliferation and EAE transfer was restored by reconstitution of γδ T cells derived from either MBP-immunized or naive mice, indicating that this effect was not Ag specific. The enhancing effect of γδ T cells on MBP-induced proliferation and EAE transfer required direct cell-to-cell contact with LNC. The γδ T cell effect upon the LNC response to MBP did not involve a change in expression of the costimulatory molecules CD28, CD40L, and CTLA-4 on TCRαβ+ cells, and CD40, CD80, and CD86 on CD19+ and CD11b+ cells. However, depletion of γδ T cells resulted in significant reduction in IL-12 production by LNC. That γδ T cells enhanced the MBP response and severity of adoptive EAE by stimulating IL-12 production was supported by experiments showing that reconstitution of the γδ T cell population restored IL-12 production, and that γδ T cell depletion-induced effects were reversed by the addition of IL-12. These results suggest a role for γδ T cells in the early effector phase of the immune response in EAE.
The Gene Related to Anergy in Lymphocytes, an E3 Ubiquitin Ligase, Is Necessary for Anergy Induction in CD4 T Cells
Authors: Seroogy Christine M. , Soares Luis , Ranheim Erik A. , Su Leon , Holness Claire , Bloom Debra , Fathman C. Garrison
Published: April 2014

Acquisition of the anergy phenotype in T cells is blocked by inhibitors of protein synthesis and calcineurin activity, suggesting that anergic T cells may have a unique genetic program. Retroviral transduction of hemopoietic stem cells from TCR transgenic mice and subsequent reconstitution of syngeneic mice to express the E3 ubiquitin ligase, gene related to anergy in lymphocytes (GRAIL), or an enzymatically inactive form, H2N2 GRAIL, allowed analysis of the role of GRAIL in T cell anergy in vivo. Constitutive expression of GRAIL was sufficient to render naive CD4 T cells anergic, however, when the enzymatically inactive form H2N2 GRAIL was expressed, it functioned as a dominant negative of endogenous GRAIL and blocked the development of anergy. These data provide direct evidence that a biochemical pathway composed of GRAIL and/or GRAIL-interacting proteins is important in the development of the CD4 T cell anergic phenotype in vivo.
Cutting Edge: Cross-Presentation of Cell-Associated Antigens to MHC Class I Molecule Is Regulated by a Major Transcription Factor for Heat Shock Proteins
Authors: Zheng Hong , Li Zihai
Published: April 2014

The ability for the professional APC to cross-present Ag to MHC class I from parenchymal cells is essential for priming as well as tolerance of CD8+ T cells against intracellular Ags. Since cross-presentations of non-cell-associated free Ags are inefficient, the roles of molecular chaperones or heat shock proteins (HSPs) in chaperoning Ags to APCs have been postulated. We herein genetically addressed this hypothesis using mice that were defective of heat shock factor 1 (Hsf1), a major transcription factor for HSPs. Hsf1−/− mice have a decreased expression of several HSPs including HSP90 and HSP70. Using multiple Ag systems, we demonstrated that cross-priming of Ag-specific CD8+ T cells was inefficient when Ag expression was restricted to Hsf1−/− non-APCs. Our study provides the first genetic evidence for the roles of Hsf1 in regulating cross-presentation of MHC class I-associated Ags.
CD63 as an Activation-Linked T Cell Costimulatory Element
Authors: Pfistershammer Katharina , Majdic Otto , Stöckl Johannes , Zlabinger Gerhard , Kirchberger Stefanie , Steinberger Peter , Knapp Walter
Published: April 2014

Dendritic cells (DC) are unique in their capacity to either stimulate or regulate T cells, and receptor/ligand pairs on DC and T cells are critically involved in this process. In this study we present such a molecule, which was discovered by us when analyzing the functional effects of an anti-DC mAb. This mAb, 11C9, reacted strongly with DC, but only minimally with lymphocytes. In MLR it constantly reduced DC-induced T cell activation. Therefore, we assumed that mAb 11C9 primarily exerts its functions by binding to a DC-structure. This does not seem to be the case, however. Preincubation of DC with mAb 11C9 before adding T cells had no inhibitory effect on T cell responses. Retroviral expression cloning identified the 11C9 Ag as CD63. This lysosomal-associated membrane protein (LAMP-3), is only minimally expressed on resting T cells but can, as we show, quickly shift to the surface upon stimulation. Cross-linkage of that structure together with TCR-triggering induces strong T cell activation. CD63 on T cells thus represents an alternative target for mAb 11C9 with its binding to activated T cells rather than DC being responsible for the observed functional effects. This efficient CD63-mediated costimulation of T cells is characterized by pronounced induction of proliferation, strong IL-2 production and compared with CD28 enhanced T cell responsiveness to restimulation. Particularly in this latter quality CD63 clearly surpasses several other CD28-independent costimulatory pathways previously described. CD63 thus represents an activation-induced reinforcing element, whose triggering promotes sustained and efficient T cell activation and expansion.
The Role of B Cell-Mediated T Cell Costimulation in the Efficacy of the T Cell Retargeting Bispecific Antibody BIS20x3
Authors: Stel Alja J. , Kroesen Bart-Jan , Jacobs Susan , Groen Herman , de Leij Lou F. M. H. , Kluin-Nelemans Hanneke C. , Withoff Sebo
Published: April 2014

In this study, we investigated the role of the naturally occurring B cell-mediated T cell costimulation in the antitumor efficacy of the bispecific Ab BIS20x3. BIS20x3 has a dual specificity for both CD20 and CD3 and has previously been shown to effectively direct the lytic potential of cytolytic T cells toward malignant, CD20+ B cells. BIS20x3 instigated T cell-B cell interaction caused a dose-dependent activation of T cells that was 30 times stronger when compared with T cell activation induced by monovalent anti-CD3 Abs. The activation of T cells by BIS20x3 and B cells appeared functional and resulted in the rapid induction of high lytic potential in freshly isolated peripheral T cells. BIS20x3-mediated T cell-B cell interaction resulted in a significant up-regulation of ICAM-1 on B cells and the activation of T cells was found to be dependent on the interaction of ICAM-1 with LFA-1 and trans-activation by the NF-κB pathway. Also, the lytic potential of freshly isolated T cells activated via BIS20x3 appeared to be dependent on NF-κB signaling in the target B cells. Interestingly, the costimulatory signaling effects described in this study appeared specifically related to the targeting against CD20 because targeting against CD19, by a CD3xCD19-directed bispecific Ab, was significantly less effective in inducing T cell activation and T cell-mediated B cell lysis. Together these results demonstrate that the malignant B cells actively contribute to their own demise upon CD20-directed bispecific Ab-mediated T cell targeting.
Mechanisms of Peritoneal B-1a Cells Accumulation Induced by Murine Lupus Susceptibility LocusSle2
Authors: Xu Zhiwei , Butfiloski Edward J. , Sobel Eric S. , Morel Laurence
Published: April 2014

The abundance of B-1a cells found in the peritoneal cavity of mice is under genetic control. The lupus-prone mouse New Zealand Black and New Zealand White (NZB × NZW)F1 and its derivative NZM2410 are among the strains with the highest numbers of peritoneal B1-a cells. We have previously identified an NZM2410 genetic locus, Sle2, which is associated with the production of large numbers of B-1a cells. In this paper, we examined the mechanisms responsible for this phenotype by comparing congenic C57BL/6 mice with or without Sle2. Fetal livers generated more B-1a cells in B6.Sle2 mice, providing them with a greater starting number of B-1a cells early in life. Sle2-expressing B1-a cells proliferated significantly more in vivo than their B6 counterparts, and reciprocal adoptive transfers showed that this phenotype is intrinsic to Sle2 peritoneal B cells. The rate of apoptosis detected was significantly lower in B6.Sle2 peritoneal cavity B-1a cells than in B6, with or without exogenous B cell receptor cross-linking. Increased proliferation and decreased apoptosis did not affect Sle2 peritoneal B-2 cells. In addition, a significant number of peritoneal cavity B-1a cells were recovered in lethally irradiated B6.Sle2 mice reconstituted with B6.Igha bone marrow, showing radiation resistance in Sle2 B-1a cells or its precursors. Finally, B6.Sle2 adult bone marrow and spleen were a significant source of peritoneal B-1a cells when transferred into B6.Rag2−/− mice. This suggests that peritoneal B-1a cells are replenished throughout the animal life span in B6.Sle2 mice. These results show that Sle2 regulates the size of the B-1a cell compartment at multiple developmental checkpoints.