bluuebunny/crossref_metadata_2025 huggingface dataset:
Respiratory Syncytial Virus Predisposes Mice to Augmented Allergic Airway Responses Via IL-13-Mediated Mechanisms
Authors: Lukacs Nicholas W. , Tekkanat Kim K. , Berlin Aaron , Hogaboam Cory M. , Miller Allison , Evanoff Holly , Lincoln Pam , Maassab Hussien
Published: April 2014

The development of severe childhood asthma may be influenced by several factors including environmental and infectious stimuli. The causal relationship between infectious viral responses, such as respiratory syncytial virus (RSV), and severe asthma during early childhood is unclear. In these studies, the ability for an initial RSV infection to exacerbate and promote a more severe asthmatic-type response was investigated by combining established murine models of disease. We examined the ability of RSV to induce exacerbation of allergic disease over a relatively long period, leading to development of severe airway responses including airway inflammation and hyperreactivity. The preferential production of IL-13 during a primary RSV infection appears to play a critical role for the exacerbation of cockroach allergen-induced disease. The depletion of IL-13 during RSV infections inhibited the exacerbation and acceleration of severe allergen-induced airway hyperreactivity. This was indicated by decreases in airway hyperreactivity and changes in lung chemokine production. These data suggest that the airway responses during asthma can be greatly affected by a previous RSV infection, even when infection occurs before allergen sensitization. Overall, infection of the airways with RSV can induce an IL-13-dependent change in airway function and promotes an environment that contributes to the development of severe allergic asthmatic responses.
Lymphoid Neogenesis in Rheumatoid Synovitis
Authors: Takemura Seisuke , Braun Andrea , Crowson Cynthia , Kurtin Paul J. , Cofield Robert H. , O’Fallon William M. , Goronzy Jörg J. , Weyand Cornelia M.
Published: April 2014

In rheumatoid arthritis (RA), tissue-infiltrating lymphocytes can be arranged in sophisticated organizations that resemble microstructures usually formed in secondary lymphoid organs. Molecular pathways and host risk factors involved in this process of lymphoid neogenesis remain to be defined. In a series of 64 synovial tissue biopsies, lymphoid follicles with germinal centers (GCs) were found in 23.4% of the patients. Follicular dendritic cells (FDCs) were exclusively present in tissues with GCs, suggesting that the recruitment or in situ maturation of FDCs is a critical factor for GC formation in the synovial membrane. Primary follicles were absent, emphasizing the role of Ag recognition in the generation of inflammation-associated lymphoid organogenesis. Multivariate logistic regression analysis of tissue cytokines and chemokines identified two parameters, in situ transcription of lymphotoxin (LT)-β and of B lymphocyte chemoattractant (BLC; BLC/CXCL13), that were predictors for FDC recruitment and synovial GC formation. LT-β and BLC/CXCL13 were found to be independent variables that could, in part, compensate for each other to facilitate GC formation. Prediction models incorporating in situ transcription of LT-β and BLC/CXCL13 had high negative yet moderate positive predictive values, suggesting that LT-β and BLC/CXCL13 are necessary but not sufficient. LT-β protein was detected on a subset of mantle zone and GC B cells, but also on T cells in follicular structures. BLC/CXCL13 was produced by FDCs in follicular centers, but was predominantly found in endothelial cells and synovial fibroblasts, suggesting heterotypic signaling between cells of the synovial membrane and infiltrating lymphocytes in regulating extranodal lymphoid neogenesis.
Immunofluorescence Detection of δ Opioid Receptors (DOR) on Human Peripheral Blood CD4+ T Cells and DOR-Dependent Suppression of HIV-1 Expression
Authors: Sharp Burt M. , McAllen Kathy , Gekker Genya , Shahabi Nahid A. , Peterson Phillip K.
Published: April 2014

The δ opioid receptors (DORs) modulate T cell proliferation, IL-2 production, chemotaxis, and intracellular signaling. Moreover, in DOR-transfected Jurkat cells, δ opioids have been shown to suppress HIV-1 p24 Ag expression. These observations led us to characterize the expression of DORs by human peripheral blood T cells and to determine whether a specific DOR agonist, benzamide,4-{[2,5-dimethyl-4-(2-propenyl)-1-piperazinyl](3-methoxyphenyl)methyl]-N,−,{2S[1(S*),2α,5β]}-(9Cl) (SNC-80), can suppress p24 Ag expression by HIV-1-infected CD4+ T cells obtained from normal donors. By immunofluorescence flow cytometry, PHA stimulated the expression of DOR from 1.94 ± 0.70 (mean ± SEM) to 20.70 ± 1.88% of the PBMC population by 48 h (p < 0.0001). DOR expression was ∼40% of both the PHA-stimulated CD4+ and CD8+ T cell subsets, and virtually all DORs were found on these subsets. To determine whether activated DORs suppress HIV-1 expression, PBMC were prestimulated with PHA, and then CD4+ T cells were purified, pretreated with SNC-80, and infected with HIV-1. In a concentration-dependent manner, SNC-80 inhibited production of p24 Ag. SNC-80 10−10 M maximally suppressed (∼50%) both lymphocytotropic (HIV-1 MN) and monocytotropic (SF162) strains; higher concentrations were less effective. Naltrindole, a selective DOR antagonist, abolished the inhibitory effects of SNC-80. Kinetic studies indicated that 24-h pre- or postincubation with SNC-80, relative to infection with HIV-1, eliminated its suppressive effects. Thus, stimulating the DORs expressed by activated CD4+ T cells significantly suppressed the expression of HIV-1. These findings suggest that opioid immunomodulation directed at host T cells may be adjunctive to standard antiviral approaches to HIV-1 infection.
Acetylcholine Receptor Peptide Recognition in HLA DR3-Transgenic Mice: In Vivo Responses Correlate with MHC-Peptide Binding
Authors: Raju Raghavanpillai , Spack Edward G. , David Chella S.
Published: April 2014

HLA DR3 is an MHC molecule that reportedly predisposes humans to myasthenia gravis (MG). Though MG is an Ab-mediated autoimmune disease, CD4+ T cells are essential for the generation of high-affinity Abs; hence the specificities of autoreactive CD4+ T cells are important. In this study we report the HLA DR3-restricted T cell determinants on the extracellular region sequence of human acetylcholine receptor α subunit. We find two promiscuous determinants on this region 141–160 and 171–190 as defined by their immunogenicity in HLA DR3-, HLA DQ8-, and HLA DQ6-transgenic mice in the absence of endogenous mouse class II molecules. We also studied the minimal determinants of these two regions by truncation analysis, and the MHC binding affinity of a set of overlapping peptides spanning the complete sequence region of human acetylcholine receptor α subunit. One of the peptide sequences strongly immunogenic in HLA DR3-transgenic mice also had the highest binding affinity to HLA DR3. Identification of T cell determinants restricted to an MHC molecule known to predispose to MG may be an important step toward the development of peptide-based immunomodulation strategies for this autoimmune disease.
Failure to Induce Neonatal Tolerance in Mice That Lack Both IL-4 and IL-13 but Not in Those That Lack IL-4 Alone
Authors: Inoue Yoshihiko , Konieczny Bogumila T. , Wagener Maylene E. , McKenzie Andrew N. J. , Lakkis Fadi G.
Published: April 2014

Current evidence suggests that neonatal tolerance to a foreign Ag is the consequence of IL-4-mediated Th2 immunity rather than the thymic deletion of Ag-specific T cells. Here, we addressed the role of IL-4 in neonatal tolerance by testing whether tolerance to a minor histocompatibility Ag can be induced in newborn mice that lack IL-4 (IL-4−/−). We found that IL-4 does not play a dominant role in the induction of neonatal tolerance as newborn female IL-4−/− mice could be readily tolerized to the H-Y male Ag. In contrast, mice that lack both IL-4 and IL-13 (IL-4−/−/IL-13−/−) were resistant to the induction of neonatal tolerance, and their splenocytes produced exaggerated amounts of IFN-γ on rechallenge with the same Ag encountered during the neonatal period. These findings argue against the view that IL-4 alone is critical for the induction of neonatal tolerance and suggest that the combined actions of both IL-4 and IL-13 are essential for this process.
Cutting Edge: Editing of Recycling Class II:Peptide Complexes by HLA-DM
Authors: Pathak Sulabha S. , Lich John D. , Blum Janice S.
Published: April 2014

HLA-DM catalyzes the exchange and selection of ligands for MHC class II molecules within mature endosomal/lysosomal compartments. Here, evidence is provided that DM edits peptides in early endosomes, thus influencing presentation via recycling class II molecules. Maximal class II-restricted presentation of an albumin-derived peptide, dependent on endocytosis and recycling class II molecules, was observed in cells lacking HLA-DM. DM editing of this epitope was observed in early endocytic compartments as shown using inhibitors of early to late endosomal transport. Editing was tempered by coexpression of HLA-DO, suggesting that DM:DO ratio may be important in guiding epitope editing in early endosomal compartments. Thus, HLA-DM appears to interact with, and edit epitopes displayed by, recycling class II molecules.
Chromatin-Independent Binding of Serum Amyloid P Component to Apoptotic Cells
Authors: Familian Atoosa , Zwart Bas , Huisman Han G. , Rensink Irma , Roem Dorina , Hordijk Peter L. , Aarden Lucien A. , Hack C. Erik
Published: April 2014

Human serum amyloid P component (SAP) is a glycoprotein structurally belonging to the pentraxin family of proteins, which has a characteristic pentameric organization. Mice with a targeted deletion of the SAP gene develop antinuclear Abs, which was interpreted as evidence for a role of SAP in controlling the degradation of chromatin. However, in vitro SAP also can bind to phosphatidylethanolamine, a phospholipid which in normal cells is located mainly in the inner leaflet of the cell membrane, to be translocated to the outer leaflet of the cell membrane during a membrane flip-flop. We hypothesized that SAP, because of its specificity for phosphatidylethanolamine, may bind to apoptotic cells independent of its nuclear binding. Calcium-dependent binding of SAP to early, nonpermeable apoptotic Jurkat, SKW, and Raji cells was indeed observed. Experiments with flip-flopped erythrocytes confirmed that SAP bound to early apoptotic cells via exposed phosphatidylethanolamine. Binding of SAP was stronger to late, permeable apoptotic cells. Experiments with enucleated neutrophils, with DNase/RNase treatment of late apoptotic Jurkat cells, and competition experiments with histones suggested that binding of SAP to late apoptotic cells was largely independent of chromatin. Confocal laser microscopic studies indeed suggested that SAP bound to these apoptotic cells mainly via the blebs. Thus, this study shows that SAP binds to apoptotic cells already at an early stage, which raises the possibility that SAP is involved in dealing with apoptotic cells in vivo.
Expansion of the Antigenic Repertoire of a Single T Cell Receptor upon T Cell Activation
Authors: Amrani Abdelaziz , Serra Pau , Yamanouchi Jun , Trudeau Jacqueline D. , Tan Rusung , Elliott John F. , Santamaria Pere
Published: April 2014

Activated T cells and their naive precursors display different functional avidities for peptide/MHC, but are thought to have identical antigenic repertoires. We show that, following activation with a cognate mimotope (NRP), diabetogenic CD8+ T cells expressing a single TCR (8.3) respond vigorously to numerous peptide analogs of NRP that were unable to elicit any responses from naive 8.3-CD8+ T cells, even at high concentrations. The NRP-reactive, in vivo activated CD8+ cells arising in pancreatic islets of nonobese diabetic mice are similarly promiscuous for peptide/MHC, and paradoxically this promiscuity expands as the aviditiy of the T cell population for NRP/MHC increases with age. Thus, activation and avidity maturation of T lymphocyte populations can lead to dramatic expansions in the range of peptides that elicit functional T cell responses.
Fas Ligand (CD95L) Protects Neurons Against Perforin- Mediated T Lymphocyte Cytotoxicity
Authors: Medana Isabelle , Li Zhaoxia , Flügel Alexander , Tschopp Jürg , Wekerle Hartmut , Neumann Harald
Published: April 2014

Previous work showed that neurons of the CNS are protected against perforin-mediated T cell cytotoxicity, but are susceptible to Fas-mediated apoptosis. In this study, we report that Fas ligand (FasL) expression by neurons is involved in protection against perforin-mediated T cell cytotoxicity. Gene transcripts for FasL were identified in single murine hippocampal neurons by RT-PCR combined with patch clamp electrophysiology, and constitutive expression of FasL protein was confirmed in neurons by immunohistochemistry. Neurons derived from wild-type C57BL/6 (BL6) mice and mutant BL6.gld mice lacking functional FasL were confronted with allogeneic CTLs and continuously monitored in real time for changes in levels of intracellular calcium ([Ca2+]i), an indicator of cytotoxic damage. Perforin-mediated plasma membrane lysis, characterized by rapid, massive [Ca2+]i influx into the target cells within 0.5 h, was not detected in wild-type neurons. In striking contrast, FasL-deficient neurons showed rapid increase in [Ca2+]i within 0.5 h, reflecting perforin-dependent cell lysis. FasL seems to protect neurons by blocking degranulation of CTLs, since CD3-induced release of cytotoxic granules was reduced by coapplication of Fas-specific Abs or rFasL.
IL-6 Inhibits the Tolerogenic Function of CD8α+ Dendritic Cells Expressing Indoleamine 2,3-Dioxygenase
Authors: Grohmann Ursula , Fallarino Francesca , Bianchi Roberta , Belladonna Maria Laura , Vacca Carmine , Orabona Ciriana , Uyttenhove Catherine , Fioretti Maria Cristina , Puccetti Paolo
Published: April 2014

The outcome of dendritic cell (DC) presentation of tumor and/or self peptides, including P815AB (a tumor peptide of murine mastocytoma cells) and NRP-A7 (a synthetic peptide mimotope recognized by diabetogenic T cells), may depend on a balance between the activities of immunogenic (CD8α−) and tolerogenic (CD8α+) DC. By virtue of their respective actions on CD8− and CD8+ DC, IL-12 and IFN-γ have functionally opposing effects on peptide presentation by the CD8− DC subset, and IFN-γ-activated CD8+ DC mediate tolerogenic effects that prevail over the adjuvant activity of IL-12 on CD8− DC. We have previously shown that CD40 ligation abrogates the tolerogenic potential of CD8+ DC, an effect associated with an impaired capacity of the CD40-modulated and IFN-γ-treated DC to degrade tryptophan and initiate T cell apoptosis in vitro. We report here that IL-6 may both replace (upon administration of the recombinant cytokine) and mediate (as assessed by the use of neutralizing Abs) the effect of CD40 ligation in ablating the tolerogenic activity of CD8+ DC. The activity of IL-6 includes down-regulation of IFN-γR expression in the CD8+ DC subset and correlates to a reduced ability of these cells to metabolize tryptophan and initiate T cell apoptosis in vitro.
Enforced Expression of GATA-3 During T Cell Development Inhibits Maturation of CD8 Single-Positive Cells and Induces Thymic Lymphoma in Transgenic Mice
Authors: Nawijn Martijn C. , Ferreira Rita , Dingjan Gemma M. , Kahre Olev , Drabek Dubravka , Karis Alar , Grosveld Frank , Hendriks Rudolf W.
Published: April 2014

The zinc finger transcription factor GATA-3 is of critical importance for early T cell development and commitment of Th2 cells. To study the role of GATA-3 in early T cell development, we analyzed and modified GATA-3 expression in vivo. In mice carrying a targeted insertion of a lacZ reporter on one allele, we found that GATA-3 transcription in CD4+CD8+ double-positive thymocytes correlated with the onset of positive selection events, i.e., TCRαβ up-regulation and CD69 expression. LacZ expression remained high (∼80% of cells) during maturation of CD4 single-positive (SP) cells in the thymus, but in developing CD8 SP cells the fraction of lacZ-expressing cells decreased to <20%. We modified this pattern by enforced GATA-3 expression driven by the CD2 locus control region, which provides transcription of GATA-3 throughout T cell development. In two independent CD2-GATA3-transgenic lines, ∼50% of the mice developed thymic lymphoblastoid tumors that were CD4+CD8+/low and mostly CD3+. In tumor-free CD2-GATA3-transgenic mice, the total numbers of CD8 SP cells in the thymus were within normal ranges, but their maturation was hampered, as indicated by increased apoptosis of CD8 SP cells and a selective deficiency of mature CD69lowHSAlow CD8 SP cells. In the spleen and lymph nodes, the numbers of CD8+ T cells were significantly reduced. These findings indicate that GATA-3 supports development of the CD4 lineage and inhibits maturation of CD8 SP cells in the thymus.
A Pivotal Role for DNase I-Sensitive Regions 3b and/or 4 in the Induction of Somatic Hypermutation of IgH Genes
Authors: Terauchi Akiko , Hayashi Katsuhiko , Kitamura Daisuke , Kozono Yuko , Motoyama Noboru , Azuma Takachika
Published: April 2014

Chimeric mice were prepared from embryonic stem cells transfected with IgH genes as transgenes and RAG-2-deficient blastocysts for the purpose of identifying the cis-acting elements responsible for the induction of somatic hypermutation. Among the three transgene constructs used, the VH promoter, the rearranged VH-D-JH, an intron enhancer/matrix attachment region, and human Cμ were common to all, but the 3′-untranslated region in each construct was different. After immunization of mice with a T cell-dependent Ag, the distribution and frequency of hypermutation in transgenes were analyzed. The transgene lacking the 3′ untranslated region showed a marginal degree of hypermutation. Addition of the 3′ enhancer resulted in a slight increase in the number of mutations. However, the transgene containing DNase I-sensitive regions 3b and 4 in addition to the 3′ enhancer showed more than a 10-fold increase in hypermutation, reaching levels comparable to those observed in endogenous VH186.2 genes of C57BL/6 mice.
IFN-γ Overproduction and High Level Apoptosis Are Associated with High but Not Low VirulenceToxoplasma gondiiInfection
Authors: Gavrilescu L. Cristina , Denkers Eric Y.
Published: April 2014

Toxoplasma gondii is an opportunistic intracellular parasite which induces a highly strong type 1 cytokine response. The present study focuses on defining the factors influencing the outcome of infection with tachyzoites of the type I, highly lethal RH strain, relative to the type II, low virulence strain ME49. Infection with the RH strain led to widespread parasite dissemination and rapid death of mice; in contrast, mice survived low virulence strain ME49 infection, and tachyzoite dissemination was much less extensive. Furthermore, massive apoptosis and disintegration of the splenic architecture was characteristic of RH, but not ME49, infection. In addition, hyperinduction of IFN-γ and lack of NO production were found during RH, in contrast to ME49 infection. These data demonstrate that Toxoplasma strain characteristics exert a profound effect on the host immune response and that the latter itself is a crucial determinant in parasite virulence.
Overexpression of IL-15 In Vivo Enhances Protection AgainstMycobacterium bovisBacillus Calmette-Guérin Infection Via Augmentation of NK and T Cytotoxic 1 Responses
Authors: Umemura Masayuki , Nishimura Hitoshi , Hirose Kenji , Matsuguchi Tetsuya , Yoshikai Yasunobu
Published: April 2014

To investigate the immunomodulating effects of IL-15 in vivo on mycobacterial infection, we used IL-15-transgenic (Tg) mice, which were recently constructed with cDNA-encoding secretable isoform of IL-15 precursor protein under the control of a MHC class I promoter. The IL-15-Tg mice exhibited resistance against infection with Mycobacterium bovis bacillus Calmette-Guérin (BCG), as assessed by bacteria growth. IFN-γ level in serum was significantly higher in IL-15-Tg mice than in non-Tg mice after BCG infection. NK cells were remarkably increased, and Ag-specific T cytotoxic 1 response mediated by CD8+ T cells producing IFN-γ was significantly augmented in the IL-15-Tg mice following BCG infection. Neutralization of endogenous IFN-γ by in vivo administration of anti-IFN-γ mAb deteriorated the clearance of the bacteria. Depletion of of NK cells or CD8+ T cells by invivo administration of anti-asialo-GM1 Ab or anti-CD8 mAb hampered the exclusion of bacteria. Thus, overexpression of IL-15 in vivo enhanced protection against BCG infection via augmentation of NK and T cytotoxic 1 responses.
Unexpected Transcriptional Induction of Monocyte Chemoattractant Protein 1 by Proteasome Inhibition: Involvement of the c-Jun N-Terminal Kinase-Activator Protein 1 Pathway
Authors: Nakayama Kenji , Furusu Akira , Xu Qihe , Konta Tsuneo , Kitamura Masanori
Published: April 2014

Proteasome inhibitors, the well-known inhibitors of NF-κB, are recently considered therapeutic agents for inflammation. However, the anti-inflammatory properties of these agents have not been fully evaluated. In this report we describe a novel effect of proteasome inhibitors on the expression of monocyte chemoattractant protein 1 (MCP-1) in mesangial cells. We found that proteasome inhibitor MG132 dose-dependently induced expression of MCP-1 at the transcriptional level. The stimulatory effect was similarly observed with other proteasome inhibitors (proteasome inhibitor 1 and lactacystin) and in other cell types (NRK fibroblasts). The 5′-flanking region of the MCP-1 gene contains multiple AP-1 sites. To explore the mechanisms involved, we examined the effects of proteasome inhibition on the AP-1 pathway. Northern blot analysis showed that MG132 rapidly induced the expression of c-jun, but not c-fos. Immunoblot analysis showed that MG132 prevented degradation of c-Jun protein. Kinase assay revealed that c-Jun N-terminal kinase (JNK) was rapidly activated by MG132. Consistent with these results, a reporter assay showed that AP-1 activity was up-regulated after treatment with MG132. Curcumin, a pharmacological inhibitor of the JNK-AP-1 pathway, abrogated the induction of MCP-1 by MG132. Similarly, stable transfection with a dominant-negative mutant of c-Jun attenuated both MG132-induced activation of AP-1 and expression of MCP-1. The transcriptional activation by proteasome inhibitors was observed not only in MCP-1, but also in other AP-1-dependent genes, including stromelysin and mitogen-activated protein kinase phosphatase 1. These data revealed that proteasome inhibition triggered the expression of MCP-1 and other genes via the multistep induction of the JNK-c-Jun/AP-1 pathway.
A Novel Autocrine Pathway of Tumor Escape from Immune Recognition: Melanoma Cell Lines Produce a Soluble Protein That Diminishes Expression of the Gene Encoding the Melanocyte Lineage Melan-A/MART-1 Antigen Through Down-Modulation of Its Promoter
Authors: Kurnick James T. , Ramirez-Montagut Teresa , Boyle Lenora A. , Andrews David M. , Pandolfi Franco , Durda Paul J. , Butera David , Dunn Ian S. , Benson Elizabeth M. , Gobin Sam J. P. , van den Elsen Peter J.
Published: April 2014

We have observed that malignant melanoma cells produce a soluble protein factor(s), which down-regulates melanocyte lineage Melan-A/MART-1 Ag expression by melanoma cells with concomitant loss of recognition by Melan-A/MART-1-specific T cells. This down-modulation of Melan-A/MART-1 expression, which we refer to as “Ag silencing,” is mediated via its minimal promoter, whereas the promoter for the restricting Ag-presenting HLA-A2 molecule is not affected. Significantly, this Ag silencing is reversible, as removal of factor-containing supernatants from Melan-A/MART-1-expressing cells results in up-regulation of the promoter for the gene encoding this Ag, and renewed expression of the protein. We have evaluated over 20 known factors, none of which accounts for the Ag-silencing activity of the melanoma cell culture supernatants. The existence of this autocrine pathway provides an additional novel explanation for melanoma tumor progression in vivo in the presence of CTL specific for this melanocyte lineage Ag. These observations may have important implications for Melan-A/MART-1-specific CTL-mediated immunotherapy of melanoma tumors.
A Role of the Mitochondrial Apoptosis-Inducing Factor in Granulysin-Induced Apoptosis
Authors: Pardo Julián , Pérez-Galán Patricia , Gamen Susana , Marzo Isabel , Monleón Inmaculada , Kaspar Allan A. , Susín Santos A. , Kroemer Guido , Krensky Alan M. , Naval Javier , Anel Alberto
Published: April 2014

Granulysin is a cytolytic molecule released by CTL via granule-mediated exocytosis. In a previous study we showed that granulysin induced apoptosis using both caspase- and ceramide-dependent and -independent pathways. In the present study we further characterize the biochemical mechanism for granulysin-induced apoptosis of tumor cells. Granulysin-induced death is significantly inhibited by Bcl-2 overexpression and is associated with a rapid (1–5 h) loss of mitochondrial membrane potential, which is not mediated by ceramide generation and is not inhibited by the general caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone. Ceramide generation induced by granulysin is a slow event, only observable at longer incubation times (12 h). Apoptosis induced by exogenous natural (C18) ceramide is truly associated with mitochondrial membrane potential loss, but contrary to granulysin, this event is inhibited by benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone. Ceramide-induced apoptosis is also completely prevented by Bcl-2 overexpression. The nuclear morphology of cells dying after granulysin treatment in the presence of caspase inhibitors suggested the involvement of mitochondrial apoptosis-inducing factor (AIF) in granulysin-induced cell death. We demonstrate using confocal microscopy that AIF is translocated from mitochondria to the nucleus during granulysin-induced apoptosis. The majority of Bcl-2 transfectants are protected from granulysin-induced cell death, mitochondrial membrane potential loss, and AIF translocation, while a small percentage are not protected. In this small percentage the typical nuclear apoptotic morphology is delayed, being of the AIF type at 5 h time, while at longer times (12 h) the normal apoptotic morphology is predominant. These and previous results support a key role for the mitochondrial pathway of apoptosis, and especially for AIF, during granulysin-induced tumoral cell death.
A VH12 Transgenic Mouse Exhibits Defects in Pre-B Cell Development and Is Unable to Make IgM+ B Cells
Authors: Wang Hongsheng , Ye Jian , Arnold Larry W. , McCray Suzanne K. , Clarke Stephen H.
Published: April 2014

VH12 B cells undergo stringent selection at multiple checkpoints to favor development of B-1 cells that bind phosphatidylcholine. Selection begins with the VH third complementarity-determining region (CDR3) at the pre-B cell stage, in which most VH12 pre-B cells are selectively eliminated, enriching for those with VHCDR3s of 10 aa and a fourth position Gly (designated 10/G4). To understand this selection, we compared B cell differentiation in mice of two VH12 transgenic lines, one with the favored 10/G4 VHCDR3 and one with a non-10/G4 VHCDR3 of 8 aa and no Gly (8/G0). Both H chains drive B cell differentiation to the small pre-BII cell stage, and induce allelic exclusion and L chain gene rearrangement. However, unlike 10/G4 pre-B cells, 8/G0 pre-B cells are deficient in cell division and unable to differentiate to B cells. We suggest that this is due to poor 8/G0 pre-B cell receptor expression and to an inability to form an 8/G0 B cell receptor. Our findings also suggest that VH12 H chains have evolved such that association with surrogate and conventional L chains is most efficient with a 10/G4 CDR3. Thus, selection for phosphatidylcholine-binding B-1 cells is most likely the underlying evolutionary basis for the loss of non-10/G4 pre-B cells.
Positive Signaling Through CD72 Induces Mitogen-Activated Protein Kinase Activation and Synergizes with B Cell Receptor Signals to Induce X-Linked Immunodeficiency B Cell Proliferation
Authors: Wu Hsin-Jung , Venkataraman Chandrasekar , Estus Steven , Dong Chen , Davis Roger J. , Flavell Richard A. , Bondada Subbarao
Published: April 2014

CD72 is a 45-kDa B cell transmembrane glycoprotein that has been shown to be important for B cell activation. However, whether CD72 ligation induces B cell activation by delivering positive signals or sequestering negative signals away from B cell receptor (BCR) signals remains unclear. Here, by comparing the late signaling events associated with the mitogen-activated protein kinase pathway, we identified many similarities and some differenes between CD72 and BCR signaling. Thus, CD72 and BCR activated the extracellular signal-regulated kinase (ERK) and the c-Jun N-terminal kinase (JNK) but not p38 mitogen-activated protein kinase. Both CD72- and BCR-mediated ERK and JNK activation required protein kinase C activity, which was equally important for CD72- and BCR-induced B cell proliferation. However, CD72 induced stronger JNK activation compared with BCR. Surprisingly, the JNK activation induced by both BCR and CD72 is Btk independent. Although both CD72 and BCR induced Btk-dependent ERK activation, CD72-mediated proliferation is more resistent to blocking of ERK activity than that of BCR, as shown by the proliferation response of B cells treated with PD98059 and dibutyryl cAMP, agents that inhibit ERK activity. Most importantly, CD72 signaling compensated for defective BCR signaling in X-linked immunodeficiency B cells and partially restored the proliferation response of X-linked immunodeficiency B cells to anti-IgM ligation. These results suggest that CD72 signals B cells by inducing BCR-independent positive signaling pathways.
Multiple Paths for Activation of Naive CD8+ T Cells: CD4-Independent Help
Authors: Wang Bo , Norbury Christopher C. , Greenwood Roberta , Bennink Jack R. , Yewdell Jonathan W. , Frelinger Jeffrey A.
Published: April 2014

CD8+ CTLs play a pivotal role in immune responses against many viruses and tumors. Two models have been proposed. The “three-cell” model focuses on the role of CD4+ T cells, proposing that help is only provided to CTLs by CD4+ T cells that recognize Ag on the same APC. The sequential “two-cell” model proposes that CD4+ T cells can first interact with APCs, which in turn activate naive CTLs. Although these models provide a general framework for the role of CD4+ T cells in mediating help for CTLs, a number of issues are unresolved. We have investigated the induction of CTL responses using dendritic cells (DCs) to immunize mice against defined peptide Ags. We find that help is required for activation of naive CTLs when DCs are used as APCs, regardless of the origin or MHC class I restriction of the peptides we studied in this system. However, CD8+ T cells can provide self-help if they are present at a sufficiently high precursor frequency. The important variable is the total number of T cells responding, because class II-knockout DCs pulsed with two noncompeting peptides are effective in priming.
Minimal Requirements for IgE-Mediated Regulation of Surface FcεRI
Authors: Borkowski Teresa A. , Jouvin Marie-Hélène , Lin Shih-Yao , Kinet Jean-Pierre
Published: April 2014

The IgE-FcεRI network plays a central role in allergic inflammation. IgE levels control cell surface levels of FcεRI and, in turn, FcεRI levels modulate the intensity of effector responses. Treatment of allergic patients with anti-IgE Abs has been shown to induce a decrease in FcεRI expression on basophils and a decrease in Ag-triggered histamine release. However, the mechanisms underlying IgE-mediated regulation of FcεRI expression remain unclear. Here, we designed an in vitro model system to establish the minimal cellular requirements for regulation of FcεRI by IgE. Using this system, we demonstrate that transcriptional regulation, hemopoietic-specific factors, and signaling are not required for IgE-mediated increases in FcεRI expression. IgE binding to the α-chain is the minimal requirement for the induction of FcεRI up-regulation. The rate of up-regulation is independent of the baseline level of expression. The mechanism of this up-regulation is the result of a combination of three factors: 1) stabilization of the receptor at the cell surface, which prevents receptor internalization and degradation; 2) use of a preformed pool of receptor comprising recycled and recently synthesized receptors; and 3) continued basal level of protein synthesis. It is possible that in vivo additional factors contribute to modulate the basic regulatory mechanism described here.
An Absolute Requirement for STAT4 and a Role for IFN-γ as an Amplifying Factor in IL-12 Induction of the Functional IL-18 Receptor Complex
Authors: Nakahira Masakiyo , Tomura Michio , Iwasaki Masayuki , Ahn Hyun-Jong , Bian Yang , Hamaoka Toshiyuki , Ohta Tsunetaka , Kurimoto Masashi , Fujiwara Hiromi
Published: April 2014

IL-12 and IL-18 are both proinflammatory cytokines that contribute to promoting Th1 development and IFN-γ expression. However, neither IL-12R nor IL-18R is expressed as a functional complex on most resting T cells. This study investigated the molecular mechanisms underlying the induction of an IL-18R complex in T cells. Resting T cells expressed IL-18Rα chains but did not exhibit IL-18 binding sites as detected by incubation with rIL-18 followed by anti-IL-18 Ab, suggesting a lack of IL-18Rβ expression in resting T cells. Although they also failed to express IL-12R, stimulation with anti-CD3 plus anti-CD28 generated IL-12R. Exposure of these cells to IL-12 led not only to up-regulation of IL-18Rα expression but also to induction of IL-18R binding sites on both CD4+ and CD8+ T cells concomitant with IL-18Rβ mRNA expression. The IL-18 binding site represented a functional IL-18R complex capable of exhibiting IL-18 responsiveness. IL-12 induction of an IL-18R complex and IL-18Rβ mRNA expression was not observed in STAT4-deficient (STAT4−/−) T cells and was substantially decreased in IFN-γ−/− T cells. However, the failure of STAT4−/− T cells to induce an IL-18R complex was not corrected by IFN-γ. These results indicate that STAT4 and IFN-γ play an indispensable role and a role as an amplifying factor, respectively, in IL-12 induction of the functional IL-18R complex.
4-1BB Ligand Induces Cell Division, Sustains Survival, and Enhances Effector Function of CD4 and CD8 T Cells with Similar Efficacy
Authors: Cannons Jennifer L. , Lau Peggy , Ghumman Birinder , DeBenedette Mark A. , Yagita Hideo , Okumura Ko , Watts Tania H.
Published: April 2014

A costimulatory member of the TNFR family, 4-1BB, is expressed on activated T cells. Although some reports have suggested that 4-1BB is primarily involved in CD8 T cell activation, in this report we demonstrate that both CD4 and CD8 T cells respond to 4-1BB ligand (4-1BBL) with similar efficacy. CD4 and CD8 TCR transgenic T cells up-regulate 4-1BB, OX40, and CD27 and respond to 4-1BBL-mediated costimulation during a primary response to peptide Ag. 4-1BBL enhanced proliferation, cytokine production, and CTL effector function of TCR transgenic T cells. To compare CD4 vs CD8 responses to 4-1BBL under similar conditions of antigenic stimulation, we performed MLRs with purified CD4 or CD8 responders from CD28+/+ and CD28−/− mice. We found that CD8 T cells produced IL-2 and IFN-γ in a 4-1BBL-dependent manner, whereas under the same conditions the CD4 T cells produced IL-2 and IL-4. 4-1BBL promoted survival of CD4 and CD8 T cells, particularly at late stages of the MLR. CD4 and CD8 T cells both responded to anti-CD3 plus s4-1BBL with a similar cytokine profile as observed in the MLR. CD4 and CD8 T cells exhibited enhanced proliferation and earlier cell division when stimulated with anti-CD3 plus anti-CD28 compared with anti-CD3 plus 4-1BBL, and both subsets responded comparably to anti-CD3 plus 4-1BBL. These data support the idea that CD28 plays a primary role in initial T cell expansion, whereas 4-1BB/4-1BBL sustains both CD4 and CD8 T cell responses, as well as enhances cell division and T cell effector function.
A T Cell Clone’s Avidity Is a Function of Its Activation State
Authors: Hesse Maike D. , Karulin Alexey Y. , Boehm Bernhard O. , Lehmann Paul V. , Tary-Lehmann Magdalena
Published: April 2014

At present it is unclear how Ag dose-dependent T cell functions, such as cytokine production, reflect TCR affinity and how the signal strength afforded by the Ag dose affects the kinetics of cytokine production by the individual T cell. We used a computer-assisted ELISPOT approach to address these issues. IFN-γ release by a clonal population of CD4 T cells was monitored on a clonal population of APC while titrating the nominal peptide. The frequency of cytokine-producing cells, the net per-cell output of cytokine, and the onset of cytokine production were each found to be functions of the signal strength. Sigmoidal dose-response curves were seen at the clonal population level, but the activation thresholds for the individual T cells followed a Gaussian distribution. Moreover, the overall dose-response curve of the T cell clone revealed cyclic changes, becoming increasingly shifted toward lower Ag concentrations with the duration of time that elapsed since the last restimulation with Ag. Therefore, responsiveness to Ag (“functional avidity”) is not a constant parameter of a T cell clone but a function of the T cell’s history of last Ag encounter. The implications of such shifting activation thresholds are discussed for autoimmune disease.
H2-O Inhibits Presentation of Bacterial Superantigens, but Not Endogenous Self Antigens
Authors: Qi Ling , Ostrand-Rosenberg Suzanne
Published: April 2014

H2-O/HLA-DO are MHC class II accessory molecules that modulate exogenous Ag presentation. Most class II accessory molecules are expressed in all professional APC; however, H2-O is only expressed in B cells and medullary thymic epithelial cells. Because B cells present exogenous Ags and superantigens (SAgs), and medullary thymic epithelial cells are specialized APC for self Ags during negative selection in the thymus, we have hypothesized that H2-O might play a role in MHC class II-restricted SAg and self Ag presentation. In this study, we demonstrate that H2-O expression inhibits presentation of the bacterial SAgs staphylococcal enterotoxins A and B to four SAg-reactive T hybridoma cells. In contrast, H2-O has no effect on presentation of endogenous self Ags, as measured by tumorigenicity in vivo and Ag presentation to three self Ag-specific T hybridoma cells. Additional experiments suggest that H2-O inhibits presentation of exogenous Ags by both newly synthesized and recycling MHC class II molecules. These data suggest H2-O may have a physiological role in tolerance induction and SAg-mediated toxic shock.
Sendai Virus Fusion Protein-Mediates Simultaneous Induction of MHC Class I/II-Dependent Mucosal and Systemic Immune Responses Via the Nasopharyngeal-Associated Lymphoreticular Tissue Immune System
Authors: Kunisawa Jun , Nakanishi Tsuyoshi , Takahashi Ichiro , Okudaira Akiko , Tsutsumi Yasuo , Katayama Kazufumi , Nakagawa Shinsaku , Kiyono Hiroshi , Mayumi Tadanori
Published: April 2014

Nasal administration of Ags using a novel hybrid Ag delivery vehicle composed of envelope glycoproteins of Sendai virus on the surface of liposome membranes (fusogenic liposome) efficiently delivered Ags to Ag-sampling M cells in nasopharyngeal-associated lymphoreticular tissue. Additionally, fusogenic liposomes also effectively delivered the Ags into epithelial cells and macrophages in nasopharyngeal-associated lymphoreticular tissue and nasal passages. In vitro Ag presentation assays clearly showed that fusogenic liposomes effectively presented encapsulated Ags via the MHC class II-dependent pathway of epithelial cells as well as macrophages. Fusogenic liposomes also have an adjuvant activity against mucosal epithelial cells to enhance MHC class II expression. According to these high delivery and adjuvant activities of fusogenic liposomes, nasal immunization with OVA-encapsulated fusogenic liposomes induced high levels of OVA-specific CD4+ Th1 and Th2 cell responses. Furthermore, Ag-specific CTL responses and Ab productions were also elicited at both mucosal and systemic sites by nasal immunization with Ag-encapsulated fusogenic liposomes. These results indicate that fusogenic liposome is a versatile and effective system for the stimulation of Ag-specific immune responses at both mucosal and systemic compartments.
Dendritic Cells from Nonobese Diabetic Mice Exhibit a Defect in NF-κB Regulation Due to a Hyperactive IκB Kinase
Authors: Weaver Donald J. , Poligone Brian , Bui Thi , Abdel-Motal Ussama M. , Baldwin Albert S. , Tisch Roland
Published: April 2014

Insulin-dependent diabetes mellitus (IDDM) is characterized by the T cell-mediated destruction of insulin-producing β cells. Accordingly, APCs, such as macrophage, have also been shown to be important in the disease process. However, the role(s) of dendritic cells (DCs) that exhibit potent APC function remains undefined in IDDM. Here we demonstrate that DCs derived from nonobese diabetic (NOD) mice, a model for IDDM, are more sensitive to various forms of stimulation compared with those from C57BL/6 and BALB/c mice, resulting in increased IL-12 secretion. This property is a consequence of hyperactivation of NF-κB, a transcription factor known to regulate IL-12 gene expression. Specifically, NOD DCs exhibit persistent hyperactivation of both IκB kinase and NF-κB in response to stimuli, in addition to selective degradation of IκBε. Transfection of NOD DCs with a modified form of IκBα significantly reduced IL-12 secretion, suggesting that hyperactivation of NF-κB was in part responsible for increased IL-12 production. An enhanced capacity of NOD DCs to secrete IL-12 would be expected to contribute to the development of pathogenic Th1 (Tc1) cells during the diabetogenic response.
C1 Inhibitor: Analysis of the Role of Amino Acid Residues Within the Reactive Center Loop in Target Protease Recognition
Authors: Zahedi Rana , MacFarlane Ryan C. , Wisnieski Jeffrey J. , Davis Alvin E.
Published: April 2014

Previous analysis of a naturally occurring C1 inhibitor P2 mutant (Ala443→Val) indicated a role for P2 in specificity determination. To define this role and that of other reactive center loop residues, a number of different amino acids were introduced at P2, as well as at P6 (Ala439) and P8′/9′ (Gln452Gln453). Ala439→Val is a naturally occurring mutant observed in a patient with hereditary angioedema. Previous data suggested that Gln452Gln453 might be a contact site for C1s. Reactivity of the inhibitors toward target (C1s, C1r, kallikrein, β factor XIIa, and plasmin) and nontarget proteases (α-thrombin and trypsin) were studied. Substitution of P2 with bulky or charged residues resulted in decreased reactivity with all target proteases. Substitution with residues with hydrophobic or polar side chains resulted in decreased reactivity with some proteases, but in unaltered or increased reactivity with others. Second order rate constants for the reaction with C1s were determined for the mutants with activities most similar to the wild-type protein. The three P2 mutants showed reductions in rate from 3.35 × 105 M−1s−1 for the wild type to 1.61, 1.29, and 0.63 × 105 for the Ser, Thr, and Val mutants, respectively. In contrast, the Ala439→Val and the Gln452Gln453→Ala mutants showed little difference in association rates with C1s, in comparison with the wild-type inhibitor. The data confirm the importance of P2 in specificity determination. However, the P6 position appears to be of little, if any, importance. Furthermore, it appears unlikely that Gln452Gln453 comprise a portion of a protease contact site within the inhibitor.
Blocking the Receptor for IL-10 Improves Antimycobacterial Chemotherapy and Vaccination
Authors: Silva Regina A. , Pais Teresa F. , Appelberg Rui
Published: April 2014

Novel approaches are required for the prevention and therapy of mycobacterial infections since the only vaccine in use, bacillus Calmette-Guérin, is poorly effective and chemotherapy is long and often ineffective in sterilizing the infection. We used a mouse model of Mycobacterium avium infection to address the usefulness of a mAb able to block IL-10R both in treatment of primary infections and in conventional multidrug therapy and subunit vaccination. Treatment of infected mice with this mAb during the entire period of experimental infection had little impact on the course of M. avium infection, with a slight improvement in the resistance of infected mice observed in the liver and spleen at day 30 of infection, which was associated with increased macrophage activation and priming of CD4+ T cells for IFN-γ production. Administration of this mAb later in infection had no effect on its course, but improved the effectiveness of chemotherapy when the latter was started in a chronic phase of infection. Also, the anti-IL-10R mAb acted as an adjuvant in the induction of protective immunity upon vaccination with a mycobacterial subunit preparation.
Mycobacterium tuberculosis19-kDa Lipoprotein Promotes Neutrophil Activation
Authors: Neufert Clemens , Pai Rish K. , Noss Erika H. , Berger Melvin , Boom W. Henry , Harding Clifford V.
Published: April 2014

Certain microbial substances, e.g., LPS, can activate neutrophils or prime them to enhance their response to other activating agents, e.g., fMLP. We investigated the role of the Mycobacterium tuberculosis (MTB) 19-kDa lipoprotein in activation of human neutrophils. MTB 19-kDa lipoprotein initiated phenotypic changes characteristic of neutrophil activation, including down-regulation of CD62 ligand (L-selectin) and up-regulation of CD35 (CR1) and CD11b/CD18 (CR3, Mac-1). In addition, exposure of neutrophils to MTB 19-kDa lipoprotein enhanced the subsequent oxidative burst in response to fMLP as assessed by oxidation of dihydrorhodamine 123 (determined by flow cytometry). LPS also produced these effects with similar kinetics, but an oligodeoxynucleotide containing a CpG motif failed to induce any priming or activation response. Although the effects of LPS required the presence of serum, neutrophil activation by MTB 19-kDa lipoprotein occurred independently of serum factors, suggesting the involvement of different receptors and signaling mechanisms for LPS and MTB 19-kDa lipoprotein. Thus, MTB 19-kDa lipoprotein serves as a pathogen-associated molecular pattern that promotes neutrophil priming and activation.