bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of CD8+ Effector T Cell Responses in Volunteers Immunized with Salmonella enterica Serovar Typhi Strain Ty21a Typhoid Vaccine
Authors: Salerno-Goncalves Rosângela , Pasetti Marcela F. , Sztein Marcelo B.
Published: April 2014

Salmonella enterica serovar Typhi (S. typhi) strain Ty21a remains the only licensed attenuated typhoid vaccine. Despite years of research, the identity of the protective immunological mechanisms elicited by immunization with the Ty21a typhoid vaccine remains elusive. The present study was designed to characterize effector T cell responses in volunteers immunized with S. typhi strain Ty21a typhoid vaccine. We determined whether immunization with Ty21a induced specific CTL able to lyse S. typhi-infected cells and secrete IFN-γ, a key effector molecule against intracellular pathogens. We measured the functional activity of these CTL by a 51Cr-release assay using 8-day restimulated PBMC from Ty21a vaccinees as effector cells and S. Typhi-infected autologous PHA-activated PBMC as target cells. Most vaccinees exhibited consistently increased CD8-mediated lysis of targets by postimmunization PBMC when compared with preimmunization levels. We also developed an IFN-γ ELISPOT assay to quantify the frequency of IFN-γ spot-forming cells (SFC) in PBMC from Ty21a vaccinees using an ex vivo system. Significant increases in the frequency of IFN-γ SFC following immunization (mean ± SD, 393 ± 172; range 185–548 SFC/106 PBMC; p = 0.010), as compared with preimmunization levels, were observed. IFN-γ was secreted predominantly by CD8+ T cells. A strong correlation was recorded between the cytolytic activity of CTL lines and the frequency of IFN-γ SFC (r2 = 0.910, p < 0.001). In conclusion, this work constitutes the first evidence that immunization of volunteers with Ty21a elicits specific CD8+ CTL and provides an estimate of the frequency of CD8+ IFN-γ-secreting cells induced by vaccination.
Role of IL-10 for Induction of Anemia During Inflammation
Authors: Tilg Herbert , Ulmer Hanno , Kaser Arthur , Weiss Günter
Published: April 2014

Anemia is frequently observed in patients suffering from chronic inflammatory disorders. Recent in vitro data suggest that Th2 cytokines, such as IL-10, could be involved in its pathogenesis. We analyzed 1) changes in hemoglobin values in 329 patients with chronic active Crohn’s disease receiving the anti-inflammatory cytokine IL-10 as part of a randomized, double-blind, placebo-controlled study, 2) serum iron parameters in a subgroup of these patients (n = 54), and 3) the in vitro effects of IL-10 on ferritin transcription and translation in human monocytic cells (THP-1) by means of Northern blot and immunoprecipitation after metabolic labeling. Patients receiving higher doses of IL-10 developed anemia and presented with a dose-dependent increase of ferritin and soluble transferrin receptor levels, an indicator of iron restriction to erythroid progenitor cells. According to our in vitro data, hyperferritinemia may result from direct stimulation of ferritin translation by IL-10 in activated monocytic cells, most likely by cytokine-mediated reduction of the binding affinity of translational repressors, iron-regulatory proteins, to the 5′-untranslated region of ferritin mRNA. In patients, all observed changes were most pronounced at the end of therapy (day +29), and thereafter hemoglobin levels and serum iron parameters returned to baseline levels within 4 wk of follow-up. Our data demonstrate that IL-10 causes anemia in patients with inflammatory bowel disease which may be referred to the induction of imbalances in iron homeostasis by the cytokine, leading to hyperferritinemia and limited iron availability to erythroid progenitor cells, a condition typically seen in the anemia of chronic inflammation.
Evolution of Epitope-Specific Memory CD4+ T Cells After Clearance of Hepatitis C Virus
Authors: Godkin Andrew J. , Thomas Howard C. , Openshaw Peter J.
Published: April 2014

The generation of memory lymphocytes is one of the hallmarks of the specific immune response. The CD4+ T cell response is of critical importance in maintaining long-term protective immunity after clearing many infections. However, accurate characterization of these memory CD4+ T cells has relied mainly on mouse studies and is poorly understood in humans. We have detected and counted epitope-specific populations of CD4+ memory cells in patients who have cleared hepatitis C virus. The kinetics of the recall response and the expression of the chemokine receptor CCR7 suggested the presence of distinct populations. A population of memory cells measured in an ex vivo IFN-γ ELISPOT assay steadily declined after viral clearance. However, memory CD4+ T cells only characterized after short-term culture with Ag and IL-2, and, recognizing the same epitopes, developed into a long-term stable population. Depletion of CCR7+ cells from PBMCs markedly reduced the responses in the culture-positive population while having little effect on the ex vivo responses. The demonstration of these key memory subsets in man opens the way to defining their role in protective immune responses.
In Situ Analysis Reveals Physical Interactions Between CD11b+ Dendritic Cells and Antigen-Specific CD4 T Cells After Subcutaneous Injection of Antigen
Authors: Ingulli Elizabeth , Ulman Deborah R. , Lucido Michelle M. , Jenkins Marc K.
Published: April 2014

In situ staining techniques were used to visualize physical interactions between dendritic cell subsets and naive Ag-specific CD4 T cells in the lymph node. Before injection of Ag, CD8+ dendritic cells and naive OVA-specific CD4 T cells were uniformly distributed throughout the T cell-rich paracortex, whereas CD11b+ dendritic cells were located mainly in the outer edges of the paracortex near the B cell-rich follicles. Many OVA-specific CD4 T cells were in contact with CD8+ dendritic cells in the absence of OVA. Within 24 h after s.c. injection of soluble OVA, the OVA-specific CD4 T cells redistributed to the outer paracortex and interacted with CD11b+, but not CD8+ dendritic cells. This behavior correlated with the uptake of OVA and the presence of peptide-MHC complexes on the surface of CD11b+ dendritic cells, and subsequent IL-2 production by the Ag-specific CD4 T cells. These results are consistent with the possibility that CD11b+ dendritic cells play a central role in the activation of CD4 T cells in response to s.c. Ag.
Intracellular Single-Chain Variable Fragments Directed to the Src Homology 2 Domains of Syk Partially Inhibit FcεRI Signaling in the RBL-2H3 Cell Line
Authors: Dauvillier Stéphanie , Mérida Peggy , Visintin Michela , Cattaneo Antonino , Bonnerot Christian , Dariavach Piona
Published: April 2014

Intracellular expression of Ab fragments has been efficiently used to inactivate therapeutic targets, oncogene products, and to induce viral resistance in plants. Ab fragments expressed in the appropriate cell compartment may also help to elucidate the functions of a protein of interest. We report in this study the successful targeting of the protein tyrosine kinase Syk in the RBL-2H3 rat basophilic leukemia cell line. We isolated from a phage display library human single-chain variable fragments (scFv) directed against the portion of Syk containing the Src homology 2 domains and the linker region that separates them. Among them, two scFv named G4G11 and G4E4 exhibited the best binding to Syk in vivo in a yeast two-hybrid selection system. Stable transfectants of RBL-2H3 cells expressing cytosolic G4G11 and G4E4 were established. Immunoprecipitation experiments showed that intracellular G4G11 and G4E4 bind to Syk, but do not inhibit the activation of Syk following FcεRI aggregation, suggesting that the scFv do not affect the recruitment of Syk to the receptor. Nevertheless, FcεRI-mediated calcium mobilization and the release of inflammatory mediators are inhibited, and are consistent with a defect in Bruton’s tyrosine kinase and phospholipase C-γ2 tyrosine phosphorylation and activation. Interestingly, FcεRI-induced mitogen-activated protein kinase phosphorylation is not altered, suggesting that intracellular G4G11 and G4E4 do not prevent the coupling of Syk to the Ras pathway, but they selectively inhibit the pathway involving phospholipase C-γ2 activation.
Expression of CD28 by Bone Marrow Stromal Cells and Its Involvement in B Lymphopoiesis
Authors: Gray Parkin Kirstin , Stephan Robert P. , Apilado Ron-Gran , Lill-Elghanian Deborah A. , Lee Kelvin P. , Saha Bhaskar , Witte Pamela L.
Published: April 2014

Young mice lacking CD28 have normal numbers of peripheral B cells; however, abnormalities exist in the humoral immune response that may result from an intrinsic defect in the B cells. The goal of this study was to assess whether CD28 could be involved in the development of B cells. CD28 mRNA was detected preferentially in the fraction of bone marrow enriched for stromal cells. Flow cytometry and RT-PCR analysis demonstrated that CD28 was also expressed by primary-cultured stromal cells that supported B lymphopoiesis. Confocal microscopy revealed that in the presence of B-lineage cells, CD28 was localized at the contact interface between B cell precursors and stromal cells. In addition, CD80 was detected on 2–6% of freshly isolated pro- and pre-B cells, and IL-7 stimulation led to induction of CD86 on 15–20% of pro- and pre-B cells. We also observed that stromal cell-dependent production of B-lineage cells in vitro was greater on stromal cells that lacked CD28. Finally, the frequencies of B-lineage precursors in the marrow from young (4- to 8-wk-old) CD28−/− mice were similar to those in wild-type mice; however, older CD28−/− mice (15–19 mo old) exhibited a 30% decrease in pro-B cells and a 50% decrease in pre-B cells vs age-matched controls. Our results suggest that CD28 on bone marrow stromal cells participates in stromal-dependent regulation of B-lineage cells in the bone marrow. The localization of CD28 at the stromal cell:B cell precursor interface suggests that molecules important for T cell:B cell interactions in the periphery may also participate in stromal cell:B cell precursor interactions in the bone marrow.
Suppressor of Cytokine Signaling 1 Inhibits Cytokine Induction of CD40 Expression in Macrophages
Authors: Wesemann Duane R. , Dong Yuanshu , O’Keefe George M. , Nguyen Vince T. , Benveniste Etty N.
Published: April 2014

CD40 is a type I membrane-bound molecule belonging to the TNFR superfamily that is expressed on various immune cells including macrophages and microglia. The aberrant expression of CD40 is involved in the initiation and maintenance of various human diseases including multiple sclerosis, arthritis, atherosclerosis, and Alzheimer’s disease. Inhibition of CD40 signaling has been shown to provide a significant beneficial effect in a number of animal models of human diseases including the aforementioned examples. We have previously shown that IFN-γ induces CD40 expression in macrophages and microglia. IFN-γ leads to STAT-1α activation directly and up-regulation of NF-κB activity due to the secretion and subsequent autocrine signaling of TNF-α. However, TNF-α alone is not capable of inducing CD40 expression in these cells. Suppressor of cytokine signaling 1 protein (SOCS-1) is a cytokine-inducible Src homology 2-containing protein that regulates cytokine receptor signaling by inhibiting STAT-1α activation via a specific interaction with activated Janus kinase 2. Given the important role of CD40 in inflammatory events in the CNS as well as other organ systems, it is imperative to understand the molecular mechanisms contributing to both CD40 induction and repression. We show that ectopic expression of SOCS-1 abrogates IFN-γ-induced CD40 protein expression, mRNA levels, and promoter activity. Additionally, IFN-γ-induced TNF-α secretion, as well as STAT-1α and NF-κB activation, are inhibited in the presence of SOCS-1. We conclude that SOCS-1 inhibits cytokine-induced CD40 expression by blocking IFN-γ-mediated STAT-1α activation, which also then results in suppression of IFN-γ-induced TNF-α secretion and subsequent NF-κB activation.
NK T Cell Precursors Exhibit Differential Cytokine Regulation and Require Itk for Efficient Maturation
Authors: Gadue Paul , Stein Paul L.
Published: April 2014

NK T cells are a lymphocyte lineage that is selected by CD1d and is characterized by the ability to rapidly secrete large amounts of both IFN-γ and IL-4 after TCR stimulation. Using reactivity to CD1d tetramers to define presumptive NK T cells, several NK T cell progenitor populations were characterized based upon NK marker expression and CD4 vs CD8 expression. The earliest populations were found to be negative for NK markers and could proliferate to IL-7, while mature NK T cells did not. The NK1.1− NK T cell progenitors were capable of up-regulating NK1.1 when transferred in vivo. Upon stimulation, the NK1.1− populations secrete IL-4, but little IFN-γ. As the cells mature and up-regulate NK1.1, they acquire the ability to secrete IFN-γ. Finally, the Tec family tyrosine kinase Itk is necessary for optimal NK1.1 up-regulation and hence final maturation of NK T cells. The itk−/− mice also display a progressive decrease in NK T cells in older animals, suggesting a further role in peripheral maintenance.
MultipleChlamydia pneumoniaeAntigens Prime CD8+ Tc1 Responses That Inhibit Intracellular Growth of This Vacuolar Pathogen
Authors: Wizel Benjamin , Starcher Barry C. , Samten Buka , Chroneos Zissis , Barnes Peter F. , Dzuris John , Higashimoto Yuichiro , Appella Ettore , Sette Alessandro
Published: April 2014

CD8+ T cells play an essential role in immunity to Chlamydia pneumoniae (Cpn). However, the target Ags recognized by Cpn-specific CD8+ T cells have not been identified, and the mechanisms by which this T cell subset contributes to protection remain unknown. In this work we demonstrate that Cpn infection primes a pathogen-specific CD8+ T cell response in mice. Eighteen H-2b binding peptides representing sequences from 12 Cpn Ags sensitized target cells for MHC class I-restricted lysis by CD8+ CTL generated from the spleens and lungs of infected mice. Peptide-specific IFN-γ-secreting CD8+ T cells were present in local and systemic compartments after primary infection, and these cells expanded after pathogen re-exposure. CD8+ T cell lines to the 18 Cpn epitope-bearing peptides were cytotoxic, displayed a memory phenotype, and secreted IFN-γ and TNF-α, but not IL-4. These CTL lines lysed Cpn-infected macrophages, and the lytic activity was inhibited by brefeldin A, indicating endogenous processing of CTL Ags. Finally, Cpn peptide-specific CD8+ CTL suppressed chlamydial growth in vitro by direct lysis of infected cells and by secretion of IFN-γ and other soluble factors. These studies provide information on the mechanisms by which CD8+ CTL protect against Cpn, furnish the tools to investigate their possible role in immunopathology, and lay the foundation for future work to develop vaccines against acute and chronic Cpn infections.
Role of IL-12-Independent and IL-12-Dependent Pathways in Regulating Generation of the IFN-γ Component of T Cell Responses toSalmonella typhimurium
Authors: John Beena , Rajagopal Deepa , Pashine Achal , Rath Satyajit , George Anna , Bal Vineeta
Published: April 2014

Clearance of facultative intracellular pathogens such as Salmonella requires IFN-γ from CD4 T cells. Mechanisms linking intracellular pathogen recognition with induction of IFN-γ-producing T cells are still poorly understood. We show in this study that IL-12 is not required for commitment to the IFN-γ-producing T cell response in infection with Salmonella typhimurium, but is needed for its maintenance. The IL-12-independent signals required for commitment depend on events during the first hour of infection and are related to Ag presentation. Even transient attenuation of Ag presentation early during infection specifically abrogates the IFN-γ component of the resulting CD4 T cell response. The IL-12 needed for maintenance is also better induced by live rather than dead bacteria in vivo, and this difference is due to specific suppression of IL-12 induction by dead bacteria. Presence of exogenous IL-4 down-modulates IL-12 production by macrophages activated in vitro. Furthermore, macrophages from IL-4-null mice secrete high levels of both IL-12 and IL-18 in response to stimulation in vivo even with dead bacteria, but this does not lead to induction of IFN-γ-secreting T cells in response to immunization with dead S. typhimurium. Early IL-4 is contributed by triggering of CD4 NK T cells by dead, but not live, bacteria. Thus, Ag presentation-related IL-12-independent events and IL-4-sensitive IL-12-dependent events play crucial complementary roles in the generation of the IFN-γ-committed CD4 T cell component of the immune response in Salmonella infection.
Activation of Peroxisome Proliferator-Activated Receptor γ by Nitric Oxide in Monocytes/Macrophages Down-Regulates p47phox and Attenuates the Respiratory Burst
Authors: von Knethen Andreas , Brüne Bernhard
Published: April 2014

NO appears as an important determinant in auto and paracrine macrophage function. We hypothesized that NO switches monocyte/macrophage function from a pro- to an anti-inflammatory phenotype by activating anti-inflammatory properties of the peroxisome proliferator-activated receptor (PPAR)γ. NO-releasing compounds (100 μM S-nitrosoglutathione or 50 μM spermine-NONOate) as well as inducible NO synthase induction provoked activation of PPARγ. This was proven by EMSAs, with the notion that supershift analysis pointed to the involvement of PPARγ. PCR analysis ruled out induction of PPARγ mRNA as a result of NO supplementation. Reporter assays, with a construct containing a triple PPAR response element in front of a thymidine kinase minimal promoter driving the luciferase gene, were positive in response to NO delivery. DNA binding capacity as well as the transactivating capability of PPARγ were attenuated by addition of the antioxidant N-acetyl-cysteine or in the presence of the NO scavenger 2-phenyl-4,4,5,6-tetramethyl-imidazoline-1-oxyl 3-oxide. Having established that NO but not lipophilic cyclic GMP analogs activated PPARγ, we verified potential anti-inflammatory consequences. The oxidative burst of macrophages, evoked by phorbol ester, was attenuated in association with NO-elicited PPARγ activation. A cause-effect relationship was demonstrated when PPAR response element decoy oligonucleotides, supplied in front of NO delivery, allowed to regain an oxidative response. PPARγ-mediated down-regulation of p47 phagocyte oxidase, a component of the NAD(P)H oxidase system, was identified as one molecular mechanism causing inhibition of superoxide radical formation. We conclude that NO participates in controlling the pro- vs anti-inflammatory phenotype of macrophages by modulating PPARγ.
Targeting the Function of IFN-γ-Inducible Protein 10 Suppresses Ongoing Adjuvant Arthritis
Authors: Salomon Izhar , Netzer Nir , Wildbaum Gizi , Schif-Zuck Sagie , Maor Gila , Karin Nathan
Published: April 2014

IFN-γ-inducible protein 10 (IP-10) is a CXC chemokine that is thought to manifest a proinflammatory role because it stimulates the directional migration of activated T cells, particularly Th1 cells. It is an open question whether this chemokine is also directly involved in T cell polarization. We show here that during the course of adjuvant-induced arthritis the immune system mounts a notable Ab titer against self-IP-10. Upon the administration of naked DNA encoding IP-10, this titer rapidly accelerates to provide protective immunity. Self-specific Ab to IP-10 developed in protected animals, as well as neutralizing Ab to IP-10 that we have generated in rabbits, could inhibit leukocyte migration, alter the in vivo and in vitro Th1/Th2 balance toward low IFN-γ, low TNF-α, high IL-4-producing T cells, and adoptively transfer disease suppression. This not only demonstrates the pivotal role of this chemokine in T cell polarization during experimentally induced arthritis but also suggests a practical way to interfere in the regulation of disease to provide protective immunity. From the basic science perspective, this study challenges the paradigm of in vivo redundancy. After all, we did not neutralize the activity of other chemokines that bind CXCR3 (i.e., macrophage-induced gene and IFN-inducible T cell α chemoattractant) and yet significantly blocked not only adjuvant-induced arthritis but also the in vivo competence to mount delayed-type hypersensitivity.
The Major Murine Systemic Lupus Erythematosus Susceptibility LocusSle1Results in Abnormal Functions of Both B and T Cells
Authors: Sobel Eric S. , Satoh Minoru , Chen Yifang , Wakeland Edward K. , Morel Laurence
Published: April 2014

Sle1 is a major susceptibility locus in the NZM2410 murine model of systemic lupus erythematosus. When isolated on a C57BL/6 background in the B6.Sle1 congenic strain, Sle1 results in the production of high levels of anti-chromatin IgG Abs, histone-specific T cells, and increased B and T cell activation. We have shown by mixed bone marrow chimeras with allotypic markers that Sle1 is expressed in B cells. Using the same technique, we now show that it is also expressed in T cells. To assess whether Sle1 results in intrinsic defects in B or T cells, we have bred the μMT and Tcrα−/− mutations onto B6.Sle1 resulting in the absence of circulating B cells and αβ T cells in B6.Sle1.μMT and B6.Sle1.Tcrα−/−, respectively. The immune phenotypes in these two strains were compared with that of B6.Sle1 and B6.μMT or B6.Tcrα−/−. Sle1-expressing B cells broke tolerance to chromatin in the absence of T cells, as shown by high levels of anti-ssDNA IgM Abs in B6.Sle1.Tcrα−/− mice, and had an increased expression of activation markers. Conversely, increased expression of activation markers and increased cytokine production were observed in Sle1-expressing T cells in the absence of B cells in B6.Sle1.μMT mice. However, the production of IgG antinuclear Abs required the presence of both T and B cells. These experiments showed that Sle1 expression results in both B and T cells intrinsic defects and demonstrate that the documented involvement of each cell compartment in the production of anti-chromatin Abs corresponds to genetic defects rather than bystander effects.
Prevalence of Regulatory T Cells Is Increased in Peripheral Blood and Tumor Microenvironment of Patients with Pancreas or Breast Adenocarcinoma
Authors: Liyanage Udaya K. , Moore Todd T. , Joo Hong-Gu , Tanaka Yoshiyuki , Herrmann Virginia , Doherty Gerard , Drebin Jeffrey A. , Strasberg Steven M. , Eberlein Timothy J. , Goedegebuure Peter S. , Linehan David C.
Published: April 2014

Regulatory T cells (Treg) that prevent autoimmune diseases by suppression of self-reactive T cells may also suppress the immune response against cancer. In mice, depletion of Treg by Ab therapy leads to more efficient tumor rejection. Treg-mediated suppression of antitumor immune responses may partly explain the poor clinical response to vaccine-based immunotherapy for human cancer. In this study, we measured the prevalence of Treg that coexpress CD4 and CD25 in the PBLs, tumor-infiltrating lymphocytes, and regional lymph node lymphocytes from 65 patients with either pancreas or breast cancer. In breast cancer patients (n = 35), pancreas cancer patients (n = 30), and normal donors (n = 35), the prevalence of Treg were 16.6% (SE 1.22), 13.2% (SE 1.13), and 8.6% (SE 0.71) of the total CD4+ cells, respectively. The prevalence of Treg were significantly higher in breast cancer patients (p < 0.01) and pancreas cancer patients (p < 0.01) when compared with normal donors. In tumor-infiltrating lymphocytes and lymph node lymphocytes, the Treg prevalence were 20.2% (SE 3.93) and 20.1% (SE 4.3), respectively. Treg constitutively coexpressed CTLA-4 and CD45RO markers, and secreted TGF-β and IL-10 but did not secrete IFN-γ. When cocultured with activated CD8+ cells or CD4+25− cells, Treg potently suppressed their proliferation and secretion of IFN-γ. We conclude that the prevalence of Treg is increased in the peripheral blood as well as in the tumor microenvironment of patients with invasive breast or pancreas cancers. These Treg may mitigate the immune response against cancer, and may partly explain the poor immune response against tumor Ags.
High Avidity CD8+ T Cells Are the Initial Population Elicited Following Viral Infection of the Respiratory Tract
Authors: Gray Peter M. , Parks Griffith D. , Alexander-Miller Martha A.
Published: April 2014

Following intranasal administration, the model paramyxovirus simian virus 5 (SV5) establishes an infection in the respiratory tract of mice, which is subsequently cleared by CD8+ T cells. In this study, we sought to understand the maturation of the antiviral immune response over time by assessing the functional avidity of the responding T cells and the expansion of immunodominant populations. Surprisingly, we determined that the initial response to Ag at day 3 (d3) in the mediastinal lymph node was exclusively high avidity. However, by d5 postinfection, low avidity cells were ∼50% of the responding T cell population. Following secondary exposure to SV5, high avidity CD8+ T cells again are the exclusive cell type present at early times postinfection (d2). Similarly, high avidity cells were preferentially elicited at d3 following infection with the unrelated vaccinia virus. We also made the observation that the immunodominance profile has not been established at d3 postinfection with SV5. However, by d5 a clear immunodominance pattern arises and is permanently maintained. These data indicate that high avidity cells are the predominant population responding at early times postinfection following respiratory infection with SV5 or vaccinia virus. However, as the response progresses, low avidity cells are activated/expanded to a greater extent compared with high avidity cells.
IL-4-Induced Arginase 1 Suppresses Alloreactive T Cells in Tumor-Bearing Mice
Authors: Bronte Vincenzo , Serafini Paolo , De Santo Carmela , Marigo Ilaria , Tosello Valeria , Mazzoni Alessandra , Segal David M. , Staib Caroline , Lowel Marianne , Sutter Gerd , Colombo Mario P. , Zanovello Paola
Published: April 2014

We previously demonstrated that a specialized subset of immature myeloid cells migrate to lymphoid organs as a result of tumor growth or immune stress, where they suppress B and T cell responses to Ags. Although NO was required for suppression of mitogen activation of T cells by myeloid suppressor cells (MSC), it was not required for suppression of allogenic responses. In this study, we describe a novel mechanism used by MSC to block T cell proliferation and CTL generation in response to alloantigen, which is mediated by the enzyme arginase 1 (Arg1). We show that Arg1 increases superoxide production in myeloid cells through a pathway that likely utilizes the reductase domain of inducible NO synthase (iNOS), and that superoxide is required for Arg1-dependent suppression of T cell function. Arg1 is induced by IL-4 in freshly isolated MSC or cloned MSC lines, and is therefore up-regulated by activated Th2, but not Th1, cells. In contrast, iNOS is induced by IFN-γ and Th1 cells. Because Arg1 and iNOS share l-arginine as a common substrate, our results indicate that l-arginine metabolism in myeloid cells is a potential target for selective intervention in reversing myeloid-induced dysfunction in tumor-bearing hosts.
Inhibition of Calpain Is a Component of Nitric Oxide-Induced Down-Regulation of Human Mast Cell Adhesion
Authors: Forsythe Paul , Befus A. Dean
Published: April 2014

Nitric oxide is an important messenger that regulates mast cell activity by modifications to gene expression and intracellular pathways associated with exocytosis and adhesion. Integrin interactions with extracellular matrix components modulate an array of cell activities, including mediator production and secretion. To investigate the molecular mechanisms underlying NO regulation of mast cell function, we studied its effects on adhesion of a human mast cell line (HMC-1) to fibronectin (FN). The NO donors S-nitrosoglutathione and S-nitroso-N-acetylpenicillamine strongly down-regulated the adhesion of HMC-1 to FN. Inhibitors of soluble guanylate cyclase and protein kinase G did not alter the response of cells to NO. A peroxynitrite scavenger did not affect modulation of adhesion by NO, nor could the effect of NO be mimicked by the peroxynitrite-producing compound 3-morpholinosydnonimine. NO donors inhibited the cysteine protease, calpain, while calpain inhibitors mimicked the effect of NO and led to a decrease in the ability of HMC-1 cells to adhere to FN. Thus, NO is an effective down-regulator of human mast cell adhesion. The mechanism for this action does not involve peroxynitrite or activation of soluble guanylate cyclase. Instead, a portion of NO-induced down-regulation of adhesion may be attributed to inhibition of the cysteine protease, calpain, an enzyme that has been associated with control of integrin activation in other cell types. The inhibition of calpain is most likely mediated via nitrosylation of its active site thiol group. Calpain may represent a novel therapeutic target for the regulation of mast cell activity in inflammatory disorders.
Expression of the Grb2-Related Protein of the Lymphoid System in B Cell Subsets Enhances B Cell Antigen Receptor Signaling Through Mitogen-Activated Protein Kinase Pathways
Authors: Yankee Thomas M. , Solow Sasha A. , Draves Kevin D. , Clark Edward A.
Published: April 2014

Adapter proteins play a critical role in regulating signals triggered by Ag receptor cross-linking. These small molecules link receptor proximal events with downstream signaling pathways. In this study, we explore the expression and function of the Grb2-related protein of the lymphoid system (GrpL)/Grb2-related adaptor downstream of Shc adapter protein in human B cells. GrpL is expressed in naive B cells and is down-regulated following B cell Ag receptor ligation. By contrast, germinal center and memory B cells express little or no GrpL. Using human B cell lines, we detected constitutive interactions between GrpL and B cell linker protein, Src homology (SH)2 domain-containing leukocyte protein of 76 kDa, hemopoietic progenitor kinase 1, and c-Cbl. The N-terminal SH3 domain of GrpL binds c-Cbl while the C-terminal SH3 domain binds B cell linker protein and SH2 domain-containing leukocyte protein of 76 kDa. Exogenous expression of GrpL in a GrpL-negative B cell line leads to enhanced Ag receptor-induced extracellular signal-related kinase and p38 mitogen-activated protein kinase phosphorylation. Thus, GrpL expression in human B cell subsets appears to regulate Ag receptor-mediated signaling events.
CD4+CD25+ Regulatory T Cells Suppress Differentiation and Functions of Th1 and Th2 Cells, Leishmania major Infection, and Colitis in Mice
Authors: Xu Damo , Liu Haiying , Komai-Koma Mousa , Campbell Carol , McSharry Charlie , Alexander James , Liew Foo Y.
Published: April 2014

Regulatory T cells play a major role in modulating the immune response. However, most information on these cells centers on autoimmunity, and there is also considerable controversy on the functional characteristics of these cells. Here we provide direct in vitro and in vivo evidence that CD4+CD25+ regulatory T cells inhibit the differentiation and functions of both Th1 and Th2 cells. Importantly, CD4+CD25+ T cells suppressed the disease development of Leishmania major infection in SCID mice reconstituted with naive CD4+CD25− T cells. Furthermore, CD4+CD25+ T cells inhibited the development of colitis induced by both Th1 and Th2 cells in SCID mice. Our results therefore document that CD4+CD25+ regulatory T cells suppress both Th1 and Th2 cells and that these regulatory T cells have a profound therapeutic potential against diseases induced by both Th1 and Th2 cells in vivo.
Identification of Mouse MD-2 Residues Important for Forming the Cell Surface TLR4-MD-2 Complex Recognized by Anti-TLR4-MD-2 Antibodies, and for Conferring LPS and Taxol Responsiveness on Mouse TLR4 by Alanine-Scanning Mutagenesis
Authors: Kawasaki Kiyoshi , Nogawa Hisashi , Nishijima Masahiro
Published: April 2014

The expression of MD-2, which associates with Toll-like receptor (TLR) 4 on the cell surface, confers LPS and LPS-mimetic Taxol responsiveness on TLR4. Alanine-scanning mutagenesis was performed to identify the mouse MD-2 residues important for conferring LPS and Taxol responsiveness on mouse TLR4, and for forming the cell surface TLR4-MD-2 complex recognized by anti-TLR4-MD-2 Ab MTS510. Single alanine mutations were introduced into mouse MD-2 (residues 17–160), and the mutants were expressed in a human cell line expressing mouse TLR4. Mouse MD-2 mutants, in which a single alanine mutation was introduced at Cys37, Leu71, Leu78, Cys95, Tyr102, Cys105, Glu111, Val113, Ile117, Pro118, Phe119, Glu136, Ile138, Leu146, Cys148, or Thr152, showed dramatically reduced ability to form the cell surface mouse TLR4-mouse MD-2 complex recognized by MTS510, and the mutants also showed reduced ability to confer LPS and Taxol responsiveness. In contrast, mouse MD-2 mutants, in which a single alanine mutation was introduced at Tyr34, Tyr36, Gly59, Val82, Ile85, Phe126, Pro127, Gly129, Ile153, Ile154, and His155 showed normal ability to form the cell surface mouse TLR4-mouse MD-2 complex recognized by MTS510, but their ability to confer LPS and Taxol responsiveness was apparently reduced. These results suggest that the ability of MD-2 to form the cell surface mouse TLR4-mouse MD-2 complex recognized by MTS510 is essential for conferring LPS and Taxol responsiveness on TLR4, but not sufficient. In addition, the required residues at codon numbers 34, 85, 101, 122, and 153 for the ability of mouse MD-2 to confer LPS responsiveness are partly different from those for Taxol responsiveness.
Toll-Like Receptor 2 Participates in Mediation of Immune Response in Experimental Pneumococcal Meningitis
Authors: Koedel Uwe , Angele Barbara , Rupprecht Tobias , Wagner Hermann , Roggenkamp Andreas , Pfister Hans-Walter , Kirschning Carsten J.
Published: April 2014

Heterologous expression of Toll-like receptor (TLR)2 and CD14 in Chinese hamster ovary fibroblasts was reported to confer responsiveness to pneumococcal peptidoglycan. The present study characterized the role of TLR2 in the host immune response and clinical course of pneumococcal meningitis. Pneumococcal infection of mice caused a significant increase in brain TLR2 mRNA expression at both 4 and 24 h postchallenge. Mice with a targeted disruption of the TLR2 gene (TLR2−/−) showed a moderate increase in disease severity, as evidenced by an aggravation of meningitis-induced intracranial complications, a more pronounced reduction in body weight and temperature, and a deterioration of motor impairment. These symptoms were associated with significantly higher cerebellar and blood bacterial titers. Brain expression of the complement inhibitor complement receptor-related protein y was significantly higher in infected TLR2−/− than in wild-type mice, while the expression of the meningitis-relevant inflammatory mediators IL-1β, TNF-α, IL-6, macrophage-inflammatory protein (MIP)-2, inducible NO synthase, and C3 was similar in both genotypes. We first ectopically expressed single candidate receptors in HEK293 cells and then applied peritoneal macrophages from mice lacking TLR2 and/or functional TLR4 for further analysis. Overexpression of TLR2 and TLR4/MD-2 conferred activation of NF-κB in response to pneumococcal exposure. However, pneumococci-induced TNF-α release from peritoneal macrophages of wild-type and TLR2/functional TLR4/double-deficient mice did not differ. Thus, while TLR2 plays a significant role in vivo, yet undefined pattern recognition receptors contribute to the recognition of and initiation of the host immune defense toward Streptococcus pneumoniae infection.
Recognition of a Specific Self-Peptide: Self-MHC Class II Complex Is Critical for Positive Selection of Thymocytes Expressing the D10 TCR
Authors: Dao Tao , Blander J. Magarian , Sant’Angelo Derek B.
Published: April 2014

We examined the specificity of positive and negative selection by using transgenic mice carrying a variant of the D10 TCR. We demonstrate that a point mutation at position 51 within the CDR2α segment significantly reduces the avidity of this TCR for its cognate ligand, but does not impact recognition of nonself MHC class II molecules. Although structural studies have suggested that this TCR site interacts with the MHC class II β-chain, the avidity of this TCR for its ligand and the function of the T cell can be reconstituted by a point mutation in the bound antigenic peptide. These data demonstrate that the bound peptide can indirectly alter TCR interactions by influencing MHC structure. Remarkably, reducing the avidity of this TCR for a specific antigenic peptide-MHC ligand has a dramatic impact on thymic selection. Positive selection of thymocytes expressing this TCR is nearly completely blocked, whereas negative selection on allogenic MHC class II molecules remains intact. Therefore, the recognition of self that promotes positive selection of the D10 TCR is highly peptide-specific.
Cutting Edge: Targeting of Vβ to Dβ Rearrangement by RSSs Can Be Mediated by the V(D)J Recombinase in the Absence of Additional Lymphoid-Specific Factors
Authors: Tillman Robert E. , Wooley Andrea L. , Khor Bernard , Wehrly Tara D. , Little Carrie A. , Sleckman Barry P.
Published: April 2014

Assembly of TCRβ variable region genes is ordered during thymocyte development with Dβ to Jβ rearrangement preceding Vβ to DJβ rearrangement. The 5′Dβ 12-RSS is required to precisely and efficiently target Vβ rearrangement beyond simply enforcing the 12/23 rule. By prohibiting direct Vβ to Jβ rearrangement, this restriction ensures Dβ gene segment use in the assembly of essentially all TCRβ variable region genes. In this study, we show that rearrangement of Vβ 23-RSSs is significantly biased to the Dβ 12-RSS over Jβ 12-RSSs on extrachromosomal recombination substrates in nonlymphoid cells that express the recombinase-activating gene-1/2 proteins. These findings demonstrate that targeting of Vβ to Dβ rearrangement can be enforced by the V(D)J recombinase in the absence of lymphoid-specific factors other than the recombinase-activating gene-1/2 proteins.
Protective Effects of IL-6 Blockade in Sepsis Are Linked to Reduced C5a Receptor Expression
Authors: Riedemann Niels C. , Neff Thomas A. , Guo Ren-Feng , Bernacki Kurt D. , Laudes Ines J. , Sarma J. Vidya , Lambris John D. , Ward Peter A.
Published: April 2014

IL-6 is known to be an important pro- and anti-inflammatory cytokine, which is up-regulated during sepsis. Our previous work has suggested a role for IL-6 in the up-regulation of C5aR in sepsis. We reported earlier that interception of C5a or C5aR results in improved outcomes in experimental sepsis. Using the cecal ligation/puncture (CLP) model in mice, we now demonstrate that treatment with anti-IL-6 Ab (anti-IL-6) results in significantly improved survival, dependent on the amount of Ab infused. CLP animals showed significantly increased binding of 125I-labeled anti-C5aR to organs when compared to either control mice at 0 h or CLP animals infused with normal rabbit 125I-labeled IgG. Binding of 125I-labeled anti-C5aR to lung, liver, kidney, and heart was significantly decreased in anti-IL-6-treated animals 6 h after CLP. RT-PCR experiments with mRNA isolated from various organs obtained 3, 6, and 12 h after CLP demonstrated increased C5aR mRNA expression during the onset of sepsis, which was greatly suppressed in CLP mice treated with anti-IL-6. These data suggest that IL-6 plays an important role in the increased expression of C5aR in lung, liver, kidney, and heart during the development of sepsis in mice and that interception of IL-6 leads to reduced expression of C5aR and improved survival.
Critical Role of the α4 Integrin/VCAM-1 Pathway in Cerebral Leukocyte Trafficking in Lupus-Prone MRL/faslprMice
Authors: James Will G. , Bullard Daniel C. , Hickey Michael J.
Published: April 2014

MRL/faslpr mice are affected by a systemic autoimmune disease that results in leukocyte recruitment to a wide range of vascular beds, including the cerebral microvasculature. The mechanisms responsible for the leukocyte trafficking to the brain in these animals are not known. Therefore, the aim of this study was to directly examine the cerebral microvasculature in MRL/faslpr mice and determine the molecular mechanisms responsible for this leukocyte recruitment. Intravital microscopy was used to assess leukocyte-endothelial cell interactions (rolling, adhesion) in the pial microcirculation of MRL+/+ (control) and MRL/faslpr mice at 8, 12, and 16 wk of age. Leukocyte rolling and adhesion were rarely observed in MRL+/+ mice of any age. MRL/faslpr mice displayed similar results at 8 and 12 wk. However, at 16 wk, significant increases in leukocyte rolling and adhesion were observed in these mice. Histological analysis revealed that the interacting cells were exclusively mononuclear. Leukocyte rolling was reduced, but not eliminated in P-selectin−/−-MRL/faslpr mice. However, leukocyte adhesion was not reduced in these mice, indicating that P-selectin-dependent rolling was not required for leukocyte recruitment to the cerebral vasculature in this model of systemic inflammation. E-selectin blockade also had no effect on leukocyte rolling. In contrast, blockade of either the α4 integrin or VCAM-1 eliminated P-selectin-independent leukocyte rolling. α4 Integrin blockade also significantly inhibited leukocyte adhesion. These studies demonstrate that the systemic inflammatory response that affects MRL/faslpr mice results in leukocyte rolling and adhesion in the cerebral microcirculation, and that the α4 integrin/VCAM-1 pathway plays a central role in mediating these interactions.
Oncostatin M Regulates Eotaxin Expression in Fibroblasts and Eosinophilic Inflammation in C57BL/6 Mice
Authors: Langdon Carrie , Kerr Christine , Tong Li , Richards Carl D.
Published: April 2014

Oncostatin M (OSM) is a member of the IL-6/LIF (or gp130) cytokine family, and its potential role in inflammation is supported by a number of activities identified in vitro. In this study, we investigate the action of murine OSM on expression of the CC chemokine eotaxin by fibroblasts in vitro and on mouse lung tissue in vivo. Recombinant murine OSM stimulated eotaxin protein production and mRNA levels in the NIH 3T3 fibroblast cell line. IL-6 could regulate a small induction of eotaxin in NIH 3T3 cells, but other IL-6/LIF cytokines (LIF, cardiotrophin-1 (CT-1)) had no effect. Cell signaling studies showed that murine OSM, LIF, IL-6, and CT-1 stimulated the tyrosine phosphorylation of STAT-3, suggesting STAT-3 activation is not sufficient for eotaxin induction in NIH 3T3 cells. OSM induced ERK-1,2 and p38 mitogen-activated protein kinase phosphorylation in NIH 3T3 cells, and inhibitors of ERK (PD98059) or p38 (SB203580) could partially reduce OSM-induced eotaxin production, suggesting partial dependence on mitogen-activated protein kinase signaling. OSM (but not LIF, IL-6, or CT-1) also induced eotaxin release by mouse lung fibroblast cultures derived from C57BL/6 mice. Overexpression of murine OSM in lungs of C57BL/6 mice using an adenovirus vector encoding murine OSM resulted in a vigorous inflammatory response by day 7 after intranasal administration, including marked extracellular matrix accumulation and eosinophil infiltration. Elevated levels of eotaxin mRNA in whole lung were detected at days 4 and 5. These data strongly support a role of OSM in lung inflammatory responses that involve eosinophil infiltration.
Strong Differential Regulation of Serum and Mucosal IgA Responses as Revealed in CD28-Deficient Mice Using Cholera Toxin Adjuvant
Authors: Gärdby Eva , Wrammert Jens , Schön Karin , Ekman Lena , Leanderson Tomas , Lycke Nils
Published: April 2014

In this study, we show that costimulation required for mucosal IgA responses is strikingly different from that needed for systemic responses, including serum IgA. Following oral immunization with cholera toxin (CT) adjuvant we found that whereas CTLA4-Hγ1 transgenic mice largely failed to respond, CD28−/− mice developed near normal gut mucosal IgA responses but poor serum Ab responses. The local IgA response was functional in that strong antitoxic protection developed in CT-immunized CD28−/− mice. This was in spite of the fact that no germinal centers (GC) were observed in the Peyer’s patches, spleen, or other peripheral lymph nodes. Moreover, significant somatic hypermutation was found in isolated IgA plasma cells from gut lamina propria of CD28−/− mice. Thus, differentiation to functional gut mucosal IgA responses against T cell-dependent Ags does not require signaling through CD28 and can be independent of GC formations and isotype-switching in Peyer’s patches. By contrast, serum IgA responses, similar to IgG-responses, are dependent on GC and CD28. However, both local and systemic responses are impaired in CTLA4-Hγ1 transgenic mice, indicating that mucosal IgA responses are dependent on the B7-family ligands, but require signaling via CTLA4 or more likely a third related receptor. Therefore, T-B cell interactions leading to mucosal as opposed to serum IgA responses are uniquely regulated and appear to represent separate events. Although CT is known to strongly up-regulate B7-molecules, we have demonstrated that it acts as a potent mucosal adjuvant in the absence of CD28, suggesting that alternative costimulatory pathways are involved.
Repression of Bleomycin-Induced Pneumopathy by TNF
Authors: Kuroki Misuzu , Noguchi Yuji , Shimono Michihide , Tomono Kazunori , Tashiro Takayoshi , Obata Yuichi , Nakayama Eiichi , Kohno Shigeru
Published: April 2014

Idiopathic pulmonary fibrosis is a chronic inflammatory lung disease with interstitial fibrosis. As a potent proinflammatory cytokine, TNF has been suggested to play critical roles in the pathogenesis of the human disease and its animal model, bleomycin-induced pneumopathy. However, studies using TNF-deficient mice have demonstrated that TNF also has an anti-inflammatory function. To determine the role of TNF in pulmonary inflammation induced by bleomycin, we injected bleomycin intratracheally into TNF-deficient mice. In this study, we demonstrated persistent and intense inflammation in TNF-deficient mice due to reduced apoptosis of inflammatory cells. We also showed that in TNF-deficient mice, challenge via airways with murine, but not human rTNF, efficiently eliminated inflammatory cells from the bronchoalveolar space by apoptosis, and thus promoted tissue repair of damaged lungs. Contrary to previous reports that showed that TNF was a central mediator of pulmonary inflammation, we have demonstrated that TNF is essential for repressing pulmonary inflammation in bleomycin-induced pneumopathy.
By IL-1 Signaling, Monocyte-Derived Cells Dramatically Enhance the Epidermal Antimicrobial Response to Lipopolysaccharide
Authors: Liu Lide , Roberts Alice A. , Ganz Tomas
Published: April 2014

Epithelia react to microbial pathogens by mounting a defensive response that includes the production of antimicrobial peptides. In this study, we show that, in human epidermal cultures, Escherichia coli LPS was a very weak direct inducer of human β-defensin (HBD)-2 mRNA and peptide, but the induction was greatly amplified when monocyte-derived cells (MoDeC) acted as intermediaries between LPS and the epidermis. IL-1R antagonist largely reversed the effect of MoDeC on epidermal HBD-2, indicating that, from among the many products of MoDeC, IL-1 was the dominant inducer of HBD-2 synthesis. In normal fresh human skin, which contains Langerhans cells and other myeloid cell types, in addition to keratinocytes, LPS also induced HBD-2 in an IL-1-dependent manner. In DNA microarray expression studies, HBD-2 was one of the most abundant mRNAs induced in epidermis by LPS-treated MoDeC, and its induction was reversed by IL-1Ra. Thus, epidermal response to LPS is potently amplified by MoDeC through IL-1-mediated signaling, leading to a selective increase in the synthesis of the antimicrobial peptide HBD-2. This pattern of responses establishes a key role for both IL-1 and HBD-2 in the host defense reaction of the epidermis.