bluuebunny/crossref_metadata_2025 huggingface dataset:
NF-κB p65 Antagonizes IL-4 Induction by c-maf in Minimal Change Nephrotic Syndrome
Authors: Valanciuté Asta , le Gouvello Sabine , Solhonne Brigitte , Pawlak André , Grimbert Philippe , Lyonnet Luc , Hue Sophie , Lang Philippe , Remy Philippe , Salomon Rémy , Bensman Albert , Guellaën Georges , Sahali Djillali
Published: April 2014

Mechanisms underlying the pathophysiology of minimal change nephrotic syndrome (MCNS), the most frequent of glomerular diseases in children, remain elusive, although recent arguments suggest that T cell dysfunction may be involved in the pathogenesis of this disease. Recently, we reported that activated T cells of these patients display a down-regulation of IL-12R β2 chain, suggesting an early commitment toward Th2 phenotype. In this study, we show that the short form of the proto-oncogene c-maf, a known activator of the IL-4 gene, is highly induced in MCNS T cells during relapse, where it translocates to the nuclear compartment and binds to the DNA responsive element. Unexpectedly, the nuclear localization of c-maf did not promote the IL-4 gene transcription in relapse. Using several approaches, we show in this study that RelA blunts IL-4 induction in T cells during the relapse in these patients. We demonstrate that the ex vivo inhibition of proteasome activity in T cells from relapse, which blocks NF-κB activity, strongly increases the IL-4 mRNA levels. Overexpression of c-maf in T cells induces a high level of IL-4 promoter-driven luciferase activity. In contrast, coexpression of c-maf with NF-κB RelA/p50, or RelA, but not p50, inhibits the c-maf-dependent IL-4 promoter activity. Finally, we demonstrated that, in T cell overexpressing RelA and c-maf, RelA expelled c-maf from its DNA binding site on IL-4 gene promoter, which results in active inhibition of IL-4 gene transcription. Altogether, these results suggest that the involvement of c-maf in Th2 commitment in MCNS operates through IL-4-independent mechanisms.
Thymic Selection and Peripheral Activation of CD8 T Cells by the Same Class I MHC/Peptide Complex
Authors: Mintern Justine D. , Maurice Madelon M. , Ploegh Hidde L. , Schott Eckart
Published: April 2014

Thymic selection is controlled by the interaction between TCR and MHC/peptide. Strength and quality of the signal determine whether thymocytes are selected or deleted. The factors that contribute to this signal remain poorly defined. Here we show that fetal thymic organ cultures (FTOCs) derived from OT-I transgenic mice (the OT-I TCR is restricted by Kb-SIINFEKL) on a KbDb−/− background support positive selection, but only when provided with soluble H-2Kb-SIINFEKL complexes. Selection of CD8 T cells is independent of the valency of the ligand or its capability to coengage CD8 molecules. Both CD8αα and CD8αβ T cells are selected by H-2Kb-SIINFEKL, but only CD8αβ cells are capable of releasing IFN-γ in response to the same ligand. The α4β7 integrin is up-regulated on postselection thymocytes from FTOCs. After adoptive transfer, FTOC-derived OT-I CD8 T cells divide in response to the agonist peptide SIINFEKL. These results establish that CD8 T cells responsive to their nominal peptide-Ag can be generated in FTOC supplemented with soluble MHC class I molecules equipped with the same peptide.
Rosmarinic Acid Induces p56lck-Dependent Apoptosis in Jurkat and Peripheral T Cells via Mitochondrial Pathway Independent from Fas/Fas Ligand Interaction
Authors: Hur Yun-Gyoung , Yun Yungdae , Won Jonghwa
Published: April 2014

Apoptosis is one way of controlling immune responses, and a variety of immunosuppressive drugs suppress harmful immune responses by inducing apoptosis of lymphocytes. In this study we observed that rosmarinic acid, a secondary metabolite of herbal plants, induced apoptosis in an p56lck (Lck)-dependent manner; Lck+ Jurkat T cells undergo apoptosis in response to rosmarinic acid (RosA) treatment, whereas Lck− Jurkat subclone J.CaM1.6 cells do not. J.CaM1.6 cells with various Lck mutants indicated that Lck SH2 domain, but not Lck kinase activity, was required for RosA-induced apoptosis. RosA induced apoptosis in the absence of a TCR stimulus, and this was not prevented by interruption of the Fas/Fas ligand interaction. Instead, RosA-mediated apoptosis involved a mitochondrial pathway as indicated by cytochrome c release and the complete blockage of apoptosis by an inhibitor of mitochondrial membrane depolarization. Both caspase-3 and -8 were indispensable in RosA-induced apoptosis and work downstream of mitochondria and caspase-9 in the order of caspase-9/caspase-3/caspase-8. In freshly isolated human PBMC, RosA specifically induced apoptosis of Lck+ subsets such as T and NK cells, but not Lck-deficient cells, including B cells and monocytes. Moreover, RosA’s ability to kill T and NK cells was restricted to actively proliferating cells, but not to resting cells. In conclusion, Lck-dependent apoptotic activity may make RosA an attractive therapeutic tool for the treatment of diseases in which T cell apoptosis is beneficial.
The Susceptibility to Experimental Myasthenia Gravis of STAT6−/− and STAT4−/− BALB/c Mice Suggests a Pathogenic Role of Th1 Cells
Authors: Wang Wei , Ostlie Norma S. , Conti-Fine Bianca M. , Milani Monica
Published: April 2014

Autoantibodies to the muscle acetylcholine receptor (AChR) cause the symptoms of human and experimental myasthenia gravis (EMG). AChR-specific CD4+ T cells permit development of these diseases, but the role(s) of the Th1 and Th2 subsets is unclear. The STAT4 and STAT6 proteins, which mediate intracellular cytokine signaling, are important for differentiation of Th1 and Th2 cells, respectively. Wild-type (WT) BALB/c mice, which are prone to develop Th2 rather than Th1 responses to Ag, are resistant to EMG. We have examined the role of Th1 and Th2 cells in EMG using STAT4 (STAT4−/−)- or STAT6 (STAT6−/−)-deficient BALB/c mice. After AChR immunization, STAT6−/− mice were susceptible to EMG: they developed more serum anti-AChR Ab, and had more complement-fixing anti-AChR IgG2a and 2b and less IgG1 than WT or STAT4−/− mice. The susceptibility to EMG of STAT6−/− mice is most likely related to the Th1 cell-induced synthesis of anti-AChR Ab, which trigger complement-mediated destruction of the neuromuscular junction. CD4+ T cells of the STAT6−/− mice had proliferative responses to the AChR comparable to those of WT and STAT4−/− mice, and recognized similar AChR epitopes. STAT6−/− mice had abundant AChR-specific Th1 cells, which were nearly absent in WT and STAT4−/− mice. Spleen and lymph nodes from STAT6−/− mice contained cells that secreted IL-4 when cultured with AChR: these are most likely STAT6-independent cells, stimulated in a non-Ag-specific manner by the cytokines secreted by AChR-specific Th1 cells.
CD28 Signals in the Immature Immunological Synapse
Authors: Andres Pietro G. , Howland Kimberly C. , Dresnek Douglas , Edmondson Samuel , Abbas Abul K. , Krummel Matthew F.
Published: April 2014

T cell recognition of peptide-MHC complexes on APCs results in the aggregation of TCRs at a central supramolecular activation complex (c-SMAC) within a mature immunological synapse. T cells require a second “costimulatory” signal for activation, the most important of which, for naive T cells, is from CD28. However the time at which CD28-derived signals are induced relative to c-SMAC formation is not well understood. In this study, we have assessed the kinetics of CD28 localization and function relative to well-established aspects of c-SMAC formation. CD28 accumulates at the immature synapse alongside the TCR and is likewise enriched at the synapse at the onset of the calcium signal. In addition, using CD28 deficient or reconstituted murine cells in a single-cell recording approach shows that CD28 regulates this signal within seconds of a TCR-mediated rise in intracellular calcium levels. Finally, CD28 exerts effects on both the initiation and stabilization of the synapse in parallel with its effects on the downstream proliferation of T cells. Together, the data show that CD28 functions in the immunological synapse before the formation of the c-SMAC.
Up-Regulation of CD1d Expression Restores the Immunoregulatory Function of NKT Cells and Prevents Autoimmune Diabetes in Nonobese Diabetic Mice
Authors: Falcone Marika , Facciotti Federica , Ghidoli Nadia , Monti Paolo , Olivieri Stefano , Zaccagnino Luca , Bonifacio Ezio , Casorati Giulia , Sanvito Francesca , Sarvetnick Nora
Published: April 2014

The immunoregulatory function of NKT cells is crucial for prevention of autoimmunity. The prototypical NKT cell Ag α-galactosylceramide is not present in mammalian cells, and little is known about the mechanism responsible for NKT cell recruitment and activation. Up-regulation of CD1d, the NKT cell restriction molecule, expressed on mononuclear cells infiltrating the target organ, could represent the physiological trigger for NKT cells to self-contain T cell immunity and to prevent autoimmune disease. Recognition of CD1d, either by itself or bound to self-ligands (selfCD1d), could drive NKT cells toward an immunoregulatory phenotype. Hence, ineffective NKT cell-mediated immunoregulation in autoimmune-prone individuals including nonobese diabetic (NOD) mice could be related to defective signals that regulate CD1d expression at time and site of autoimmunity. To test this hypothesis, we transgenically overexpressed CD1d molecules under the control of the insulin promoter within the pancreatic islets of NOD mice (insCD1d). Recognition of overexpressed CD1d molecules rescued NKT cell immunoregulatory function and prevented autoimmune diabetes in insCD1d transgenic NOD mice. Protection from diabetes was associated with a biased IL-4-secreting cytokine phenotype of NKT cells and alteration of the cytokine microenvironment in the pancreatic lymph nodes of transgenic mice. The net effect was a reduced development of the autoimmune T cell repertoire. Our findings suggest that up-regulation of CD1d expression during inflammation is critical to maintain T cell homeostasis and to prevent autoimmunity.
Visualizing the Viral Burden: Phenotypic and Functional Alterations of T Cells and APCs during Persistent Infection
Authors: Homann Dirk , McGavern Dorian B. , Oldstone Michael B. A.
Published: April 2014

Persistent viral infections continue to present major public health problems. Failure to achieve virus control confronts the immune system with a chronic viral burden that may involve immune cells themselves and directly compromise the functionality of effector lymphocytes and APCs. In this study we use the lymphocytic choriomeningitis virus system for persistent viral infection of its natural murine host and use analytical techniques for direct ex vivo visualization of virus-infected immune cells. We report that virtually all cells of the immune system can be infected, but the distribution of the viral burden is differentially allocated to lymphocyte and APC subsets of defined phenotypes. Importantly, the profile of immune cell infection found in the blood is broadly representative for the pattern of cellular infection in most organs and is independent of the presence of Abs or complement. By direct comparison of virus-infected and uninfected cell subsets, we demonstrate that lymphocytic choriomeningitis virus-infected T cells show preferential activation, skewed cytokine profiles, and increased apoptosis. In contrast, increased activation of APCs is generalized and independent of the presence of viral Ag. Our data indicate that specific patterns of immune cell infection are associated with distinct forms of immunostimulatory and immunosuppressive alterations that may provide insights into autoimmune processes associated with infectious disease and offer clues for therapeutic interventions aimed at restoration of complete immunity.
Mast Cells, FcεRI, and IL-13 Are Required for Development of Airway Hyperresponsiveness after Aerosolized Allergen Exposure in the Absence of Adjuvant
Authors: Taube Christian , Wei Xudong , Swasey Christina H. , Joetham Anthony , Zarini Simona , Lively Tricia , Takeda Katsuyuki , Loader Joan , Miyahara Nobuaki , Kodama Taku , Shultz Lenny D. , Donaldson Debra D. , Hamelmann Eckard H. , Dakhama Azzeddine , Gelfand Erwin W.
Published: April 2014

In certain models of allergic airway disease, mast cells facilitate the development of inflammation and airway hyper-responsiveness (AHR). To define the role of the high affinity IgE receptor (FcεRI) in the development of AHR, mice with a disruption of the α subunit of the high affinity IgE receptor (FcεRI−/−) were exposed on 10 consecutive days to nebulized OVA. Forty-eight hours after the last nebulization, airway responsiveness was monitored by the contractile response of tracheal smooth muscle to electrical field stimulation (EFS). After the 10-day OVA challenge protocol, wild-type mice demonstrated increased responsiveness to EFS, whereas similarly challenged FcεRI−/− mice showed a low response to EFS, similar to nonexposed animals. Further, allergen-challenged FcεRI−/− mice showed less airway inflammation, goblet cell hyperplasia, and lower levels of IL-13 in lung homogenates compared with the controls. IL-13-deficient mice failed to develop an increased response to EFS or goblet cell hyperplasia after the 10-day OVA challenge. We transferred bone marrow-derived mast cells from wild-type mice to FcεRI−/− mice 1 day before initiating the challenge protocol. After the 10-day OVA challenge, recipient FcεRI−/− mice demonstrated EFS-induced responses similar to those of challenged wild-type mice. Transferred mast cells could be detected in tracheal preparations. These results show that FcεRI is important for the development of AHR after an aerosolized allergen sensitization protocol and that this effect is mediated through FcεRI on mast cells and production of IL-13 in the lung.
Generation and Regulation of Human Th1-Biased Immune Responses In Vivo: A Critical Role for IL-4 and IL-10
Authors: Skapenko Alla , Niedobitek Gerald U. , Kalden Joachim R. , Lipsky Peter E. , Schulze-Koops Hendrik
Published: April 2014

Tissue damage in many human autoimmune diseases is mediated by activated autoantigen-specific Th1 cells. Delineation of the regulatory mechanisms controlling a Th1-biased human immune reaction and its pathologic potential is, therefore, a critical step in the understanding of autoimmune diseases. In this study, we introduce a novel means to investigate human Th1-biased immune responses in vivo. Intraperitoneal injection of human mononuclear cells into immunodeficient mice generates a xenogeneic Th1-biased human immune response characterized by systemic inflammation and leukocytic infiltrates with a granuloma-like architecture in the liver, and the perigastrointestinal and perirenal fatty tissue. Th1 cell activation was dependent on the presence of APCs and could be blocked by cyclosporine. Importantly, neutralization of endogenously produced IL-4 and IL-10 markedly exaggerated the immune response, whereas exogenous IL-4 and IL-10 inhibited systemic Th1 immunity. Thus, the model described in this paper presents a useful means to analyze the regulation of human immune reactions in an in vivo situation. The results suggest that both IL-4 and IL-10 contribute to controlling the development of a human Th1-biased immune reaction.
Xenobiotic-Induced Loss of Tolerance in Rabbits to the Mitochondrial Autoantigen of Primary Biliary Cirrhosis Is Reversible
Authors: Amano Katsushi , Leung Patrick S. C. , Xu Qingchai , Marik Jan , Quan Chao , Kurth Mark J. , Nantz Michael H. , Ansari Aftab A. , Lam Kit S. , Zeniya Mikio , Coppel Ross L. , Gershwin M. Eric
Published: April 2014

Previous work has demonstrated that immunization of rabbits with the xenobiotic 6-bromohexanoate coupled to BSA breaks tolerance and induces autoantibodies to mitochondria in rabbits. Such immunized rabbits develop high-titer Abs to pyruvate dehydrogenase complex (PDC)-E2, the major autoantigen of primary biliary cirrhosis. In efforts to map the fine specificity of these autoantibodies, rabbits were immunized biweekly with 6-bromohexanoate-BSA and screened for reactivity using a unique xenobiotic-peptide-agarose microarray platform with an emphasis on identifying potential structures that mimic the molecular image formed by the association of lipoic acid with the immunodominant PDC-E2 peptide. Essentially, a total of 23 xenobiotics and lipoic acid were coupled to the 12-mer peptide backbones, PDC, a mutant PDC, and albumin. As expected, we succeeded in breaking tolerance using this small organic molecule coupled to BSA. However, unlike multiple experimental methods of breaking tolerance, we report in this study that, following continued immunization, the rabbits recover tolerance. With repeated immunization, the response to the rPDC-E2 protein increased with a gradual reduction in autoantibodies against the lipoic acid-peptide, i.e., the primary tolerance-breaking autoantigen. Detailed analysis of this system may provide strategies on how to restore tolerance in patients with autoimmune disease.
Requirement for Donor and Recipient CD40 Expression in Cardiac Allograft Rejection: Induction of Th1 Responses and Influence of Donor-Derived Dendritic Cells
Authors: Nathan Meera J. , Mold Jeffrey E. , Wood Sherri C. , Csencsits Keri , Lu Guanyi , Eichwald Ernst J. , Bishop D. Keith
Published: April 2014

Costimulation through the CD40-CD40 ligand (CD40L) pathway is critical to allograft rejection, in that anti-CD40L mAb therapy prolongs allograft survival. However, the majority of studies exploring CD40-CD40L interactions have targeted CD40L. Less is known about the requirement for donor- and/or host-derived CD40 during rejection. This study assessed the relative contributions of donor and recipient CD40 expression to the rejection process. As the effectiveness of costimulatory blockade may be mouse strain dependent, this study explored the requirement for donor and recipient CD40 expression in BALB/c and C57BL/6 mice. Wild-type (WT) and CD40−/− BALB/c recipients readily rejected WT and CD40−/− C57BL/6 allografts, and rejection was associated with a prominent Th1 response. In contrast, CD40−/− C57BL/6 recipients failed to reject WT or CD40−/− BALB/c allografts and did not mount Th1 or Th2 responses. However, injection of donor CD40−/− dendritic cells induced both Th1 and Th2 responses and allograft rejection in CD40−/− C57BL/6 recipients. Finally, WT C57BL/6 mice rejected CD40−/− allografts, but this rejection response was associated with muted Th1 responses. These findings demonstrate that 1) CD40 expression by the recipient or the graft may impact on the immune response following transplantation; 2) the requirement for CD40 is influenced by the mouse strain; and 3) the requirement for CD40 in rejection may be bypassed by donor DC. Further, as CD40 is not required for rejection in BALB/c recipients, but anti-CD40L mAb prolongs graft survival in these mice, these results suggest that anti-CD40L therapy functions at a level beyond disruption of CD40-CD40L interactions.
Nucleosomes Are Exposed at the Cell Surface in Apoptosis
Authors: Radic Marko , Marion Tony , Monestier Marc
Published: April 2014

Apoptotic cells are considered the source of DNA, histones, and nucleoprotein complexes that drive the production of autoantibodies in systemic lupus erythematosus. However, the role of apoptotic cells in the activation of the immune system is not clear. To explore interactions that may initiate or sustain the production of anti-nuclear autoantibodies, we characterized the binding of a large panel of monoclonal autoantibodies to apoptotic cells. Autoantibodies to DNA, individual core histones, histone-DNA complexes, or the native nucleosome core particle revealed a consistent and specific binding pattern in confocal microscopy. Immunoreactive epitopes were detected in the cytoplasm and accumulated along the surface of the fragmenting nucleus in a caspase-dependent manner. Ag-Ab complexes on nuclear fragments that had emerged from the plasma membrane were accessible to anti-isotype-reactive microparticles. Moreover, autoantibodies specific for the nucleosome core or its molecular components selectively precipitated a complex of core histones and DNA from the cytosol at 4 h after induction of apoptosis. These observations identify distinct steps in the release of nucleosomes from the nucleus and their exposure at the cell surface. Furthermore, the results indicate a direct role for nucleosomes in the execution of apoptosis, clearance of apoptotic cells, and regulation of anti-nuclear autoantibody production.
Expression of L-Selectin, but Not CD44, Is Required for Early Neutrophil Extravasation in Antigen-Induced Arthritis
Authors: Szántó Sándor , Gál István , Gonda Andrea , Glant Tibor T. , Mikecz Katalin
Published: April 2014

L (leukocyte)-selectin (CD62L) and CD44 are major adhesion receptors that support the rolling of leukocytes on endothelium, the first step of leukocyte entry into inflamed tissue. The specific contribution of L-selectin or CD44 to the regulation of cell traffic to joints in arthritis has not been investigated. We used CD44-deficient, L-selectin-deficient, and CD44/L-selectin double knockout mice to determine the requirement for these receptors for inflammatory cell recruitment during Ag-induced arthritis. Intraperitoneal immunization resulted in similar activation status and Ag-specific responses in wild-type and gene-targeted mice. However, extravasation of neutrophil granulocytes, but not the emigration of T cells, into the knee joints after intra-articular Ag injection was significantly delayed in L-selectin-deficient and double knockout mice. Intravital videomicroscopy on the synovial microcirculation revealed enhanced leukocyte rolling and diminished adherence in mice lacking either CD44 or L-selectin, but CD44 deficiency had no significant effect on the recruitment of L-selectin-null cells. Compared with wild-type leukocytes, expression of L-selectin was down-regulated in CD44-deficient cells in the spleen, peripheral blood, and inflamed joints, suggesting that reduced expression of L-selectin, rather than the lack of CD44, could be responsible for the delayed influx of granulocytes into the joints of CD44-deficient mice. In conclusion, there is a greater requirement for L-selectin than for CD44 for neutrophil extravasation during the early phase of Ag-induced arthritis.
Evidence That the Long Murine Terminal Deoxynucleotidyltransferase Isoform Plays No Role in the Control of V(D)J Junctional Diversity
Authors: Doyen Noëlle , Boulé Jean-Baptiste , Rougeon François , Papanicolaou Catherine
Published: April 2014

Two TdT isoforms have been found in the mouse. The short isoform is known to add N regions to gene segment junctions during V(D)J recombination, but the role of the long (TdTL) isoform is controversial. We have shown that TdTL, although endowed with terminal transferase activity, is thermally unstable and unable to add N regions in vivo. In this study, we demonstrate that TdTL is devoid of 3′-5′ exonuclease activity, and provide an analysis of nucleotide deletion and addition patterns in large series of V(D)J coding joins, arguing against a role of TdTL in the control of junctional diversity in Igs and TCRs.
Characterization of the Human Ig Heavy Chain Antigen Binding Complementarity Determining Region 3 Using a Newly Developed Software Algorithm, JOINSOLVER
Authors: Souto-Carneiro M. Margarida , Longo Nancy S. , Russ Daniel E. , Sun Hong-wei , Lipsky Peter E.
Published: April 2014

We analyzed 77 nonproductive and 574 productive human VHDJH rearrangements with a newly developed program, JOINSOLVER. In the productive repertoire, the H chain complementarity determining region 3 (CDR3H) was significantly shorter (46.7 ± 0.5 nucleotides) than in the nonproductive repertoire (53.8 ± 1.9 nucleotides) because of the tendency to select rearrangements with less TdT activity and shorter D segments. Using criteria established by Monte Carlo simulations, D segments could be identified in 71.4% of nonproductive and 64.4% of productive rearrangements, with a mean of 17.6 ± 0.7 and 14.6 ± 0.2 retained germline nucleotides, respectively. Eight of 27 D segments were used more frequently than expected in the nonproductive repertoire, whereas 3 D segments were positively selected and 3 were negatively selected, indicating that both molecular mechanisms and selection biased the D segment usage. There was no bias for D segment reading frame (RF) use in the nonproductive repertoire, whereas negative selection of the RFs encoding stop codons and positive selection of RF2 that frequently encodes hydrophilic amino acids were noted in the productive repertoire. Except for serine, there was no consistent selection or expression of hydrophilic amino acids. A bias toward the pairing of 5′ D segments with 3′ JH segments was observed in the nonproductive but not the productive repertoire, whereas VH usage was random. Rearrangements using inverted D segments, DIR family segments, chromosome 15 D segments and multiple D segments were found infrequently. Analysis of the human CDR3H with JOINSOLVER has provided comprehensive information on the influences that shape this important Ag binding region of VH chains.
Massive Number of Antigen-Specific CD4 T Cells during Vaccination with Live Attenuated Salmonella Causes Interclonal Competition
Authors: Srinivasan Aparna , Foley Joseph , McSorley Stephen J.
Published: April 2014

The clonal burst size of CD4 T cells is predicted to be less than that of CD8 T cells. In this study, we demonstrate that massive numbers of Ag-specific CD4 T cells respond during vaccination of mice with live attenuated Salmonella, reaching a peak frequency of ∼50% of CD4 T cells. Salmonella-specific T cells persisted at high frequency for several weeks and could be detected in the memory population for months after infection. Surprisingly, the expansion of endogenous Salmonella-specific CD4 T cells prevented the persistence of adoptively transferred Salmonella-specific T cells in vivo, demonstrating interclonal competition for access to the memory compartment.
Flagellin Promotes Myeloid Differentiation Factor 88-Dependent Development of Th2-Type Response
Authors: Didierlaurent Arnaud , Ferrero Isabel , Otten Luc A. , Dubois Bertrand , Reinhardt Monique , Carlsen Harald , Blomhoff Rune , Akira Shikuo , Kraehenbuhl Jean-Pierre , Sirard Jean-Claude
Published: April 2014

Activation of dendritic cells (DC) by microbial products via Toll-like receptors (TLR) is instrumental in the induction of immunity. In particular, TLR signaling plays a major role in the instruction of Th1 responses. The development of Th2 responses has been proposed to be independent of the adapter molecule myeloid differentiation factor 88 (MyD88) involved in signal transduction by TLRs. In this study we show that flagellin, the bacterial stimulus for TLR5, drives MyD88-dependent Th2-type immunity in mice. Flagellin promotes the secretion of IL-4 and IL-13 by Ag-specific CD4+ T cells as well as IgG1 responses. The Th2-biased responses are associated with the maturation of DCs, which are shown to express TLR5. Flagellin-mediated DC activation requires MyD88 and induces NF-κB-dependent transcription and the production of low levels of proinflammatory cytokines. In addition, the flagellin-specific response is characterized by the lack of secretion of the Th1-promoting cytokine IL-12 p70. In conclusion, this study suggests that flagellin and, more generally, TLR ligands can control Th2 responses in a MyD88-dependent manner.
Altered EBV Viral Load Setpoint after HIV Seroconversion Is in Accordance with Lack of Predictive Value of EBV Load for the Occurrence of AIDS-Related Non-Hodgkin Lymphoma
Authors: Piriou Erwan R. , van Dort Karel , Nanlohy Nening M. , Miedema Frank , van Oers Marinus H. , van Baarle Debbie
Published: April 2014

In contrast to the situation in the post-transplant setting, in HIV-infected individuals an elevated EBV load is not predictive of EBV-related malignancies. To study whether a high EBV load is already a normal situation early in HIV infection and is not related to a decrease in immune function over time, we investigated EBV load and EBV-specific CD8+ T cells ∼1 year before and 1 year after HIV seroconversion. EBV load significantly increased after HIV seroconversion from 205 to 1002 copies/106 PBMC (p < 0.001), whereas no further increase in EBV load was observed between 1 and 5 years after HIV seroconversion (median, 1827–2478 copies/106 PBMC; p = 0.530). Interestingly, the absolute number of EBV lytic epitope, RAKFKQLL-specific CD8+ T cells increased over HIV seroconversion (4.78 to 9.54/μl; p = 0.011). Furthermore, the fraction of CD27-negative effector, RAK-specific CD8+ T cells tended to increase (from 12.2 to 17.31% CD27−; p = 0.051), in accordance with Ag-driven differentiation. In conclusion, both virological and immunological data support the idea that a new EBV viral setpoint is reached early in HIV infection, probably by EBV reactivation, as suggested by the preferential increase in EBV lytic epitope-specific CD8+ T cells. These data may thus help to explain the lack of predictive value of EBV load for the occurrence of AIDS-related lymphoma.
Toxoplasma gondiiTriggers Myeloid Differentiation Factor 88-Dependent IL-12 and Chemokine Ligand 2 (Monocyte Chemoattractant Protein 1) Responses Using Distinct Parasite Molecules and Host Receptors
Authors: Del Rio Laura , Butcher Barbara A. , Bennouna Soumaya , Hieny Sara , Sher Alan , Denkers Eric Y.
Published: April 2014

Toll-like receptors (TLR) that signal through the common adaptor molecule myeloid differentiation factor 88 (MyD88) are essential in proinflammatory cytokine responses to many microbial pathogens. In this study we report that Toxoplasma gondii triggers neutrophil IL-12 and chemokine ligand 2 (CCL2; monocyte chemoattractant protein 1) production in strict dependence upon functional MyD88. Nevertheless, the responses are distinct. Although we identify TLR2 as the receptor triggering CCL2 production, parasite-induced IL-12 release did not involve this TLR. The production of both IL-12 and CCL2 was increased after neutrophil activation with IFN-γ. However, the synergistic effect of IFN-γ on IL-12, but not CCL2, was dependent upon Stat1 signal transduction. Although IL-10 was a potent down-regulator of Toxoplasma-triggered neutrophil IL-12 release, the cytokine had no effect on parasite-induced CCL2 production. Soluble tachyzoite Ag fractionation demonstrated that CCL2- and IL-12 inducing activities are biochemically distinct. Importantly, Toxoplasma cyclophilin-18, a molecule previously shown to induce dendritic cell IL-12, was not involved in neutrophil IL-12 production. Our results show for the first time that T. gondii possesses multiple molecules triggering distinct MyD88-dependent signaling cascades, that these pathways are independently regulated, and that they lead to distinct profiles of cytokine production.
Toll-Like Receptor 4 Signaling by Intestinal Microbes Influences Susceptibility to Food Allergy
Authors: Bashir Mohamed Elfatih H. , Louie Steve , Shi Hai Ning , Nagler-Anderson Cathryn
Published: April 2014

The mechanisms by which signaling by the innate immune system controls susceptibility to allergy are poorly understood. In this report, we show that intragastric administration of a food allergen with a mucosal adjuvant induces allergen-specific IgE, elevated plasma histamine levels, and anaphylactic symptoms in three different strains of mice lacking a functional receptor for bacterial LPS (Toll-like receptor 4 (TLR4)), but not in MHC-matched or congenic controls. Susceptibility to allergy correlates with a Th2-biased cytokine response in both the mucosal (mesenteric lymph node and Peyer’s patch) and systemic (spleen) tissues of TLR4-mutant or -deficient mice. TLR4-mutant mice are not inherently impaired in their ability to regulate Th1 cytokine production because they respond to stimulation via TLR9. Coadministration of CpG oligodeoxynucleotides during sensitization of TLR4-mutant mice with allergen plus CT abrogates anaphylactic symptoms and Ag-specific IgE, and results in a Th1-polarized cytokine response. When the composition of the bacterial flora is reduced and altered by antibiotic administration (beginning at 2 wk of age), TLR4 wild-type mice become as susceptible to the induction of allergy as their TLR4-mutant counterparts. Both allergen-specific IgE and Th2 cytokine responses are reduced in antibiotic-treated mice in which the flora has been allowed to repopulate. Taken together, our results suggest that TLR4-dependent signals provided by the intestinal commensal flora inhibit the development of allergic responses to food Ags.
Chemotaxis Inhibitory Protein of Staphylococcus aureus Binds Specifically to the C5a and Formylated Peptide Receptor
Authors: Postma Bent , Poppelier Miriam J. , van Galen Joost C. , Prossnitz Eric R. , van Strijp Jos A. G. , de Haas Carla J. C. , van Kessel Kok P. M.
Published: April 2014

Chemotaxis inhibitory protein of Staphylococcus aureus (CHIPS) is an exoprotein produced by several strains of S. aureus, and a potent inhibitor of neutrophil and monocyte chemotaxis toward C5a and formylated peptides like fMLP. These chemoattractants act on their target cells by binding and activating the C5aR and formylated peptide receptor (FPR), respectively. In the present report, we examined the mechanism by which CHIPS affects both of these receptors. We showed that CHIPS blocked binding of anti-C5aR mAb and formylated peptide to human neutrophils as efficiently at temperatures of 0 and 37°C, implying that it is independent of signal transducing systems. This was confirmed by showing that CHIPS acts completely independently of ATP. Additionally, CHIPS was not internalized upon binding to neutrophils. Furthermore, we showed that CHIPS binds specifically to the C5aR and FPR expressed on U937 cells. This binding was functional in blocking C5a- and fMLP-induced calcium mobilization in these cell lines. These results suggest that CHIPS binds directly to the C5aR and FPR, thereby preventing the natural ligands from activating these receptors. The apparent Kd values of CHIPS for the C5aR and FPR were 1.1 ± 0.2 nM and 35.4 ± 7.7 nM, respectively. Moreover, after screening a wide variety of other G protein-coupled receptors, CHIPS was found to affect exclusively the C5aR and FPR. This selectivity and high-affinity binding with potent antagonistic effects makes CHIPS a promising lead for the development of new anti-inflammatory compounds for diseases in which damage by neutrophils plays a key role.
TL1A Synergizes with IL-12 and IL-18 to Enhance IFN-γ Production in Human T Cells and NK Cells
Authors: Papadakis Konstantinos A. , Prehn John L. , Landers Carol , Han Qiwei , Luo Xia , Cha Stephanie C. , Wei Ping , Targan Stephan R.
Published: April 2014

TL1A, a recently described TNF-like cytokine that interacts with DR3, costimulates T cells and augments anti-CD3 plus anti-CD28 IFN-γ production. In the current study we show that TL1A or an agonistic anti-DR3 mAb synergize with IL-12/IL-18 to augment IFN-γ production in human peripheral blood T cells and NK cells. TL1A also enhanced IFN-γ production by IL-12/IL-18 stimulated CD56+ T cells. When expressed as fold change, the synergistic effect of TL1A on cytokine-induced IFN-γ production was more pronounced on CD4+ and CD8+ T cells than on CD56+ T cells or NK cells. Intracellular cytokine staining showed that TL1A significantly enhanced both the percentage and the mean fluorescence intensity of IFN-γ-producing T cells in response to IL-12/IL-18. The combination of IL-12 and IL-18 markedly up-regulated DR3 expression in NK cells, whereas it had minimal effect in T cells. Our data suggest that TL1A/DR3 pathway plays an important role in the augmentation of cytokine-induced IFN-γ production in T cells and that DR3 expression is differentially regulated by IL-12/IL-18 in T cells and NK cells.
TGF-β1 Represses Activation and Resultant Death of Microglia via Inhibition of Phosphatidylinositol 3-Kinase Activity
Authors: Kim Won-Ki , Hwang So-Young , Oh Eok-Soo , Piao Hua Zi , Kim Ki-Wan , Han Inn-Oc
Published: April 2014

Overactivation of microglial cells may cause severe brain tissue damage in various neurodegenerative diseases. Therefore, the overactivation of microglia should be repressed by any means. The present study investigated the potential mechanism and signaling pathway for the repressive effect of TGF-β1, a major anti-inflammatory cytokine, on overactivation and resultant death of microglial cells. A bacterial endotoxin LPS stimulated expression of inducible NO synthase (iNOS) and caused death in cultured microglial cells. TGF-β1 markedly blocked these LPS effects. However, the LPS-evoked death of microglial cells was not solely attributed to excess production of NO. Because phosphatidylinositol 3-kinase (PI3K) was previously shown to play a crucial role in iNOS expression and cell survival signals, we further studied whether PI3K signaling was associated with the suppressive effect of TGF-β1. Like TGF-β1, the PI3K inhibitor LY294002 blocked iNOS expression and death in cultured microglial cells. Both TGF-β1 and LY294002 decreased the activation of caspases 3 and 11 and the mRNA expression of various kinds of inflammatory molecules caused by LPS. TGF-β1 was further found to decrease LPS-induced activation of PI3K and Akt. TGF-β1 and LY294002 suppressed LPS-induced p38 mitogen-activated kinase and c-Jun N-terminal kinase activity. In contrast, TGF-β1 and LY294002 enhanced LPS-induced NF-κB activity. Our data indicate that TGF-β1 protect normal or damaged brain tissue by repressing overactivation of microglial cells via inhibition of PI3K and its downstream signaling molecules.
Bid Truncation, Bid/Bax Targeting to the Mitochondria, and Caspase Activation Associated with Neutrophil Apoptosis Are Inhibited by Granulocyte Colony-Stimulating Factor
Authors: Maianski Nikolai A. , Roos Dirk , Kuijpers Taco W.
Published: April 2014

Neutrophil apoptosis constitutes a way of managing neutrophil-mediated reactions. It allows coping with infections, but avoiding overt bystander tissue damage. Using digitonin-based subcellular fractionation and Western blotting, we found that spontaneous apoptosis of human neutrophils (after ∼20 h of culture) was associated with translocation of two proapoptotic Bcl-2 homologues, Bid and Bax, to the mitochondria and truncation of Bid, with subsequent release of Omi/HtrA2 and Smac/DIABLO into the cytosol. These events were accompanied by processing and increased enzymatic activity of caspase-8, -9, and -3. A G-CSF-mediated reduction in apoptosis coincided with inhibition of all these reactions. The G-CSF-induced effects were differentially dependent on newly synthesized mediators. Whereas inhibition of Bax targeting to the mitochondria and inhibition of caspase activation by G-CSF were dependent on protein synthesis, Bid truncation and redistribution were prevented by G-CSF regardless of the presence of the protein synthesis inhibitor cycloheximide. Apparently, the observed Bid changes were dispensable for neutrophil apoptosis. Although the regulators of the inhibitor of apoptosis proteins (IAPs), Omi/HtrA2 and Smac/DIABLO, were released into the cytosol during apoptosis, we did not observe cleavage of X-linked IAP, which suggests that another mechanism of IAP deactivation is involved. Together our results support an integrative role of the mitochondria in induction and/or amplification of caspase activity and show that G-CSF may act by blocking Bid/Bax redistribution and inhibiting caspase activation.
Effects of TNF-α and IFN-γ on Nitric Oxide-Induced Neurotoxicity in the Mouse Brain
Authors: Blais Véronique , Rivest Serge
Published: April 2014

The present study investigated the interaction between highly reactive gaseous-free radical NO and cytokines that are produced by activated Th-1 cells on the cerebral immune response and neuronal integrity. CD-1 mice received an intrastriatal infusion of different solutions containing the NO synthase inhibitor N(G)-nitro-l-arginine methylester, NO-releasing substance sodium nitroprusside (SNP), IFN-γ, and/or TNF-α. The solution containing both cytokines caused a profound and transient transcriptional activation of numerous genes encoding proinflammatory proteins in microglial/monocytic cells ipsilateral to infusion site. This increase in gene expression peaked 1 day after the cerebral bolus of cytokines and returned to basal levels from 3 to 7 days post administration. N(G)-nitro-l-arginine methylester further stimulated this immune reaction to IFN-γ and TNF-α, but the brain of these mice failed to exhibit signs of neurodegeneration and demyelination. In contrast, a single bolus of SNP in the striatal region caused neuronal death and demyelination as early as 1 to 3 days following the infusion with the NO donor. This phenomenon was greatly exacerbated by the coadministration of both cytokines, although TNF-α remained the most critical cytokine to enhance the damage of cerebral elements. These data provide evidence that NO has the ability to modulate the immune response, which is not by itself detrimental for the brain. However, SNP-induced NO production together with TNF-α in the cerebral environment are critical events leading to intense neurodegeneration and demyelination in vivo.
Genomic and Proteomic Determinants of Outcome in Patients Undergoing Thoracoabdominal Aortic Aneurysm Repair
Authors: Feezor Robert J. , Baker Henry V. , Xiao Wenzhong , Lee W. Anthony , Huber Thomas S. , Mindrinos Michael , Kim Raymond A. , Ruiz-Taylor Laurence , Moldawer Lyle L. , Davis Ronald W. , Seeger James M.
Published: April 2014

Thoracoabdominal aortic aneurysm repair, with its requisite intraoperative mesenteric ischemia-reperfusion, often results in the development of systemic inflammatory response syndrome, multiorgan dysfunction syndrome (MODS), and death. In the present study, an adverse clinical outcome following thoracoabdominal aortic aneurysm repair was identified by blood leukocyte genomic and plasma proteomic responses. Time-dependent changes in the expression of 146 genes from blood leukocytes were observed (p < 0.001). Expression of 138 genes (p < 0.001) and the concentration of seven plasma proteins discriminated between patients who developed MODS and those who did not, and many of these differences were evident even before surgery. These findings suggest that changes in blood leukocyte gene expression and plasma protein concentrations can illuminate pathophysiological processes that are subsequently associated with the clinical sequelae of systemic inflammatory response syndrome and MODS. These changes in gene expression and plasma protein concentrations are often observed before surgery, consistent with either a genetic predisposition or pre-existing inflammatory state.
A Promoter Haplotype of the Immunoreceptor Tyrosine-Based Inhibitory Motif-Bearing FcγRIIb Alters Receptor Expression and Associates with Autoimmunity. I. Regulatory FCGR2B Polymorphisms and Their Association with Systemic Lupus Erythematosus
Authors: Su Kaihong , Wu Jianming , Edberg Jeffrey C. , Li Xiaoli , Ferguson Polly , Cooper Glinda S. , Langefeld Carl D. , Kimberly Robert P.
Published: April 2014

FcγRIIb, the immunoreceptor tyrosine-based inhibitory motif-containing receptor for IgG (Mendelian Inheritance in Man no. 604590), plays an important role in maintaining the homeostasis of immune responses. We have identified 10 novel single-nucleotide polymorphisms in the promoter region of human FCGR2B gene and characterized two functionally distinct haplotypes in its proximal promoter. In luciferase reporter assays, the less frequent promoter haplotype leads to increased expression of the reporter gene in both B lymphoid and myeloid cell lines under constitutive and stimulated conditions. Four independent genome-wide scans support linkage of the human FcγR region to the systemic lupus erythematosus (SLE; Online Mendelian Inheritance in Man no. 152700) phenotype. Our case-control study in 600 Caucasians indicates a significant association of the less frequent FCGR2B promoter haplotype with the SLE phenotype (odds ratio = 1.65; p = 0.0054). The FCGR2B haplotype has no linkage disequilibrium with previously identified FCGR2A and FCGR3A polymorphisms, and after adjustment for FCGR2A and FCGR3A, FCGR2B showed a persistent association with SLE (odds ratio = 1.72; p = 0.0083). These results suggest that an expression variant of FCGR2B is a risk factor for human lupus and implicate FCGR2B in disease pathogenesis.
Development of the Dendritic Cell System during Mouse Ontogeny
Authors: Dakic Aleksandar , Shao Qi-xiang , D’Amico Angela , O’Keeffe Meredith , Chen Wei-feng , Shortman Ken , Wu Li
Published: April 2014

Based on the view that the efficacy of the immune system is associated with the maturation state of the immune cells, including dendritic cells (DC), we investigated the development and functional potential of conventional DC and plasmacytoid pre-DC (p-preDC) in spleen, thymus, and lymph nodes during mouse development. Both CD11c+ DC and CD45RA+ p-preDC were detected in small numbers in the thymus as early as embryonic day 17. The ratio of DC to thymocytes reached adult levels by 1 wk, although the normal CD8α+ phenotype was not acquired until later. Significant, but low, numbers of DC and p-preDC were present in the spleen of day 1 newborn mice. The full complement of DC and p-preDC was not acquired until 5 wk of age. The composition of DC populations in the spleen of young mice differed significantly from that found in adult mice, with a much higher percentage (50–60% compared with 20–25%) of the CD4−CD8α+ DC population and a much lower percentage (10–20% compared with 50–60%) of the CD4+CD8α− DC population. Although the p-preDC of young mice showed a capacity to produce IFN-α comparable with that of adult mice, the conventional DC of young mice were less efficient than those of their adult counterparts in IL-12p70 and IFN-γ production and in Ag presentation. These results suggest that the neonatal DC system is not fully developed, and innate immunity is the dominant form of response. The complete DC system required for adaptive immunity in the mouse is not fully developed until 5 wk of age.
Ultraviolet Radiation-Induced Regulatory T Cells Not Only Inhibit the Induction but Can Suppress the Effector Phase of Contact Hypersensitivity
Authors: Schwarz Agatha , Maeda Akira , Wild Martin K. , Kernebeck Kerstin , Gross Nicole , Aragane Yoshinori , Beissert Stefan , Vestweber Dietmar , Schwarz Thomas
Published: April 2014

Epicutaneous application of haptens to UV-exposed skin induces hapten-specific tolerance. This is mediated via regulatory T cells (Tr), as i.v. injection of T cells from UV-tolerized mice into naive animals renders the recipients unresponsive to the respective hapten. However, when UV-induced Tr are injected i.v. into sensitized mice, contact hypersensitivity (CHS) is not suppressed, suggesting that Tr inhibit the induction, but not the elicitation, of CHS and are inferior to T effector cells. As sensitization takes place in the lymph nodes, but elicitation occurs in the area of challenge, we postulated that Tr injected i.v. locate to the lymph nodes and not to the periphery and therefore only suppress the induction, not the elicitation, of CHS. Indeed, i.v. injection of Tr into sensitized mice did not inhibit CHS, although injection of Tr into the ears of sensitized mice suppressed the challenge. Inhibition was hapten specific, as injection of dinitrofluorobenzene (DNFB)-specific Tr into the ears of oxazolone (OXA)-sensitized mice did not affect challenge with OXA. However, when ears of OXA-sensitized mice were injected with DNFB-specific Tr and painted with DNFB before OXA challenge, CHS was suppressed. Inhibition correlated with the local expression of IL-10. Depletion studies and FACS analysis revealed that Tr express the lymph node-homing receptor L-selectin, but not the ligands for the skin-homing receptors E- and P-selectin, suggesting that UV-induced Tr, although able to inhibit T effector cells, do not suppress the elicitation of CHS upon i.v. injection, because they obviously do not migrate into the skin.