bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lck-Dependent Tyrosine Phosphorylation of Diacylglycerol Kinase α Regulates Its Membrane Association in T Cells
Authors: Merino Ernesto , Ávila-Flores Antonia , Shirai Yasuhito , Moraga Ignacio , Saito Naoaki , Mérida Isabel 
Published: April 2014

Abstract
TCR engagement triggers phospholipase Cγ1 activation through the Lck-ZAP70-linker of activated T cell adaptor protein pathway. This leads to generation of diacylglycerol (DAG) and mobilization of intracellular Ca2+, both essential for TCR-dependent transcriptional responses. TCR ligation also elicits transient recruitment of DAG kinase α (DGKα) to the lymphocyte plasma membrane to phosphorylate DAG, facilitating termination of DAG-regulated signals. The precise mechanisms governing dynamic recruitment of DGKα to the membrane have not been fully elucidated, although Ca2+ influx and tyrosine kinase activation were proposed to be required. We show that DGKα is tyrosine phosphorylated, and identify tyrosine 335 (Y335), at the hinge between the atypical C1 domains and the catalytic region, as essential for membrane localization. Generation of an Ab that recognizes phosphorylated Y335 demonstrates Lck-dependent phosphorylation of endogenous DGKα during TCR activation and shows that pY335DGKα is a minor pool located exclusively at the plasma membrane. Our results identify Y335 as a residue critical for DGKα function and suggest a mechanism by which Lck-dependent phosphorylation and Ca2+ elevation regulate DGKα membrane localization. The concerted action of these two signals results in transient, receptor-regulated DGKα relocalization to the site at which it exerts its function as a negative modulator of DAG-dependent signals.
Systemic Control of Plasmacytoid Dendritic Cells by CD8+ T Cells and Commensal Microbiota
Authors: Fujiwara Daisuke , Wei Bo , Presley Laura L. , Brewer Sarah , McPherson Michael , Lewinski Michael A. , Borneman James , Braun Jonathan 
Published: April 2014

Abstract
The composition of the intestinal microbial community is a distinctive individual trait that may divergently influence host biology. Because dendritic cells (DC) regulate the quality of the host response to microbiota, we evaluated DC in mice bearing distinct enteric microbial communities divergent for colitis susceptibility. Surprisingly, a selective, systemic reduction of plasmacytoid dendritic cells (pDC) was observed in isogenic mice with different microbiota: restricted flora (RF) vs specific pathogen free (SPF). This reduction was not observed in germfree mice, suggesting that the pDC deficiency was not simply due to a lack of intestinal microbial products. The microbial action was linked to cytotoxic CD8+ T cells, since pDC in RF mice were preserved in the CD8−/− and perforin−/− genotypes, partially restored by anti-CD8β Ab, and augmented in SPF mice bearing the TAP−/− genotype. Direct evidence for pDC cytolysis was obtained by rapid and selective pDC depletion in SPF mice transferred with RF CD8+ T cells. These data indicate that commensal microbiota, via CTL activation, functionally shape systemic immune regulation that may modify risk of inflammatory disease.
Pathogen Proliferation Governs the Magnitude but Compromises the Function of CD8 T Cells
Authors: Sad Subash , Dudani Renu , Gurnani Komal , Russell Marsha , van Faassen Henk , Finlay Brett , Krishnan Lakshmi 
Published: April 2014

Abstract
CD8+ T cell memory is critical for protection against many intracellular pathogens. However, it is not clear how pathogen virulence influences the development and function of CD8+ T cells. Salmonella typhimurium (ST) is an intracellular bacterium that causes rapid fatality in susceptible mice and chronic infection in resistant strains. We have constructed recombinant mutants of ST, expressing the same immunodominant Ag OVA, but defective in various key virulence genes. We show that the magnitude of CD8+ T cell response correlates directly to the intracellular proliferation of ST. Wild-type ST displayed efficient intracellular proliferation and induced increased numbers of OVA-specific CD8+ T cells upon infection in mice. In contrast, mutants with defective Salmonella pathogenicity island II genes displayed poor intracellular proliferation and induced reduced numbers of OVA-specific CD8+ T cells. However, when functionality of the CD8+ T cell response was measured, mutants of ST induced a more functional response compared with the wild-type ST. Infection with wild-type ST, in contrast to mutants defective in pathogenicity island II genes, induced the generation of mainly effector-memory CD8+ T cells that expressed little IL-2, failed to mediate efficient cytotoxicity, and proliferated poorly in response to Ag challenge in vivo. Taken together, these results indicate that pathogens that proliferate rapidly and chronically in vivo may evoke functionally inferior memory CD8+ T cells which may promote the survival of the pathogen.
IFN-γ and IL-17 Production in Experimental Autoimmune Encephalomyelitis Depends on Local APC–T Cell Complement Production
Authors: Liu Jinbo , Lin Feng , Strainic Michael G. , An Fengqi , Miller Robert H. , Altuntas Cengiz Z. , Heeger Peter S. , Tuohy Vincent K. , Medof M. Edward 
Published: April 2014

AbstractIFN-γ- and IL-17-producing T cells autoreactive across myelin components are central to the pathogenesis of multiple sclerosis. Using direct in vivo, adoptive transfer, and in vitro systems, we show in this study that the generation of these effectors in myelin oligodendrocyte glycoprotein35–55-induced experimental autoimmune encephalomyelitis depends on interactions of locally produced C3a/C5a with APC and T cell C3aR/C5aR. In the absence of the cell surface C3/C5 convertase inhibitor decay-accelerating factor (DAF), but not the combined absence of DAF and C5aR and/or C3aR on APC and T cells, a heightened local autoimmune response occurs in which myelin destruction is markedly augmented in concert with markedly more IFN-γ+ and IL-17+ T cell generation. The augmented T cell response is due to increased IL-12 and IL-23 elaboration by APCs together with increased T cell expression of the receptors for each cytokine. The results apply to initial generation of the IL-17 phenotype because naive CD62Lhigh Daf1−/− T cells produce 3-fold more IL-17 in response to TGF-β and IL-6, whereas CD62Lhigh Daf1−/−C5aR−/−C3aR−/− T cells produce 4-fold less.
CD83 Expression in CD4+ T Cells Modulates Inflammation and Autoimmunity
Authors: Reinwald Simone , Wiethe Carsten , Westendorf Astrid M. , Breloer Minka , Probst-Kepper Michael , Fleischer Bernhard , Steinkasserer Alexander , Buer Jan , Hansen Wiebke 
Published: April 2014

Abstract
The transmembrane protein CD83 has been initially described as a maturation marker for dendritic cells. Moreover, there is increasing evidence that CD83 also regulates B cell function, thymic T cell maturation, and peripheral T cell activation. Herein, we show that CD83 expression confers immunosuppressive function to CD4+ T cells. CD83 mRNA is differentially expressed in naturally occurring CD4+CD25+ regulatory T cells, and upon activation these cells rapidly express large amounts of surface CD83. Transduction of naive CD4+CD25− T cells with CD83 encoding retroviruses induces a regulatory phenotype in vitro, which is accompanied by the induction of Foxp3. Functional analysis of CD83-transduced T cells in vivo demonstrates that these CD83+Foxp3+ T cells are able to interfere with the effector phase of severe contact hypersensitivity reaction of the skin. Moreover, adoptive transfer of these cells prevents the paralysis associated with experimental autoimmune encephalomyelitis, suppresses proinflammatory cytokines IFN-γ and IL-17, and increases antiinflammatory IL-10 in recipient mice. Taken together, our data provide the first evidence that CD83 expression can contribute to the immunosuppressive function of CD4+ T cells in vivo.
Deacetylase Activity Is Required for STAT5-Dependent GM-CSF Functional Activity in Macrophages and Differentiation to Dendritic Cells
Authors: Sebastián Carlos , Serra Maria , Yeramian Andrée , Serrat Neus , Lloberas Jorge , Celada Antonio 
Published: April 2014

Abstract
After interaction with its receptor, GM-CSF induces phosphorylation of the β-chain in two distinct domains in macrophages. One induces activation of mitogen-activated protein kinases and the PI3K/Akt pathway, and the other induces JAK2-STAT5. In this study we describe how trichostatin A (TSA), which inhibits deacetylase activity, blocks JAK2-STAT5-dependent gene expression but not the expression of genes that depend on the signal transduction induced by the other domain of the receptor. TSA treatment inhibited the GM-CSF-dependent proliferation of macrophages by interfering with c-myc and cyclin D1 expression. However, M-CSF-dependent proliferation, which requires ERK1/2, was unaffected. Protection from apoptosis, which involves Akt phosphorylation and p21waf-1 expression, was not modified by TSA. GM-CSF-dependent expression of MHC class II molecules was inhibited because CIITA was not induced. The generation of dendritic cells was also impaired by TSA treatment because of the inhibition of IRF4, IRF2, and RelB expression. TSA mediates its effects by preventing the recruitment of RNA polymerase II to the promoter of STAT5 target genes and by inhibiting their expression. However, this drug did not affect STAT5A or STAT5B phosphorylation or DNA binding. These results in GM-CSF-treated macrophages reveal a relationship between histone deacetylase complexes and STAT5 in the regulation of gene expression.
Regulatory T Cells Inhibit Dendritic Cells by Lymphocyte Activation Gene-3 Engagement of MHC Class II
Authors: Liang Bitao , Workman Craig , Lee Janine , Chew Claude , Dale Benjamin M. , Colonna Lucrezia , Flores Marcella , Li Nianyu , Schweighoffer Edina , Greenberg Steven , Tybulewicz Victor , Vignali Dario , Clynes Raphael 
Published: April 2014

Abstract
Lymphocyte activation gene-3 (LAG-3) is a CD4-related transmembrane protein expressed by regulatory T cells that binds MHC II on APCs. It is shown in this study that during Treg:DC interactions, LAG-3 engagement with MHC class II inhibits DC activation. MHC II cross-linking by agonistic Abs induces an ITAM-mediated inhibitory signaling pathway, involving FcγRγ and ERK-mediated recruitment of SHP-1 that suppresses dendritic cell maturation and immunostimulatory capacity. These data reveal a novel ITAM-mediated inhibitory signaling pathway in DCs triggered by MHC II engagement of LAG-3, providing a molecular mechanism in which regulatory T cells may suppress via modulating DC function.
Disruption of Mutually Negative Regulatory Feedback Loop between Interferon-Inducible p202 Protein and the E2F Family of Transcription Factors in Lupus-Prone Mice
Authors: Panchanathan Ravichandran , Xin Hong , Choubey Divaker 
Published: April 2014

Abstract
Studies have identified IFN-inducible Ifi202 gene as a lupus susceptibility gene (encoding p202 protein) in mouse models of lupus disease. However, signaling pathways that regulate the Ifi202 expression in cells remain to be elucidated. We found that steady-state levels of Ifi202 mRNA and protein were high in mouse embryonic fibroblasts (MEFs) from E2F1 knockout (E2F1−/−) and E2F1 and E2F2 double knockout (E2F1−/−E2F2−/−) mice than isogenic wild-type MEFs. Moreover, overexpression of E2F1 in mouse fibroblasts decreased expression of p202. Furthermore, expression of E2F1, but not E2F4, transcription factor in mouse fibroblasts repressed the activity of 202-luc-reporter in promoter-reporter assays. Interestingly, the E2F1-mediated transcriptional repression of the 202-luc-reporter was independent of p53 and pRb expression. However, the repression was dependent on the ability of E2F1 to bind DNA. We have identified a potential E2F DNA-binding site in the 5′-regulatory region of the Ifi202 gene, and mutations in this E2F DNA-binding site reduced the E2F1-mediated transcriptional repression of 202-luc-reporter. Because p202 inhibits the E2F1-mediated transcriptional activation of genes, we compared the expression of E2F1 and its target genes in splenic cells from lupus-prone B6.Nba2 congenic mice, which express increased levels of p202, with age-matched C57BL/6 mice. We found that increased expression of Ifi202 in the congenic mice was associated with inhibition of E2F1-mediated transcription and decreased expression of E2F1 and its target genes that encode proapoptotic proteins. Our observations support the idea that increased Ifi202 expression in certain strains of mice contributes to lupus susceptibility in part by inhibiting E2F1-mediated functions.
IL-12 Signaling Drives CD8+ T Cell IFN-γ Production and Differentiation of KLRG1+ Effector Subpopulations during Toxoplasma gondii Infection
Authors: Wilson Douglas C. , Matthews Suzanne , Yap George S. 
Published: April 2014

Abstract
IFN-γ-producing CD8+ T lymphocytes are essential effector cells that mediate protective immunity during murine toxoplasmosis, and yet their effector development remains poorly characterized. Vaccination with the carbamoyl phosphate synthase (CPS) mutant strain of Toxoplasma gondii was used to examine the CD8+ T cell response in the peritoneal effector site. Four CTL subpopulations with varying effector potentials were defined based on the expression of effector molecules and the cell surface activation markers CD62L and killer cell lectin-like receptor G1 (KLRG1). Further phenotypic analysis revealed that the acquisition of KLRG1 among effector subpopulations correlated with the down-regulation of both IL-7R and CD27, suggesting that KLRG1 marks dominant, end-stage effector cells. Using gene-targeted mice, we tested the in vivo requirements of key IL-12 signaling components for effector CTL differentiation. Contrary to established models of viral and bacterial infection, CD8+ T cell-intrinsic IL-12 signaling was required for the generation of IFN-γ-producing CTLs in response to T. gondii. Importantly, the development of the KLRG1+ effector subpopulations, but not the memory precursor-containing KLRG1− effector subset, was critically reliant on IL-12. Furthermore, IL-12 signaling-dependent T-bet expression was also found to be important for differentiation of KLRG1+ effectors. Our results underscore a vital role for IL-12 in not only the induction of IFN-γ expression but also in the development of heterogeneous subpopulations of effector CD8+ T cells generated in response to the intracellular parasite T. gondii.
An Interaction between CD200 and Monoclonal Antibody Agonists to CD200R2 in Development of Dendritic Cells That Preferentially Induce Populations of CD4+CD25+ T Regulatory Cells
Authors: Gorczynski Reg , Khatri Ismat , Lee Lydia , Boudakov Ivo 
Published: April 2014

Abstract
In previous studies we reported that while interaction between the relatively ubiquitously expressed molecule CD200 and one of its receptors, CD200R1, resulted in direct suppression of alloreactivity, engagement of alternate receptors led instead to altered differentiation of dendritic cells (DCs) from marrow precursors, which could in turn foster development of Foxp3+ regulatory T cells. We have explored this effect of engagement of alternate receptors by using a monoclonal agonist Ab to CD200R2 and investigating expression of TLRs on DCs induced in vivo and in vitro after CD200 stimulation in mice in which the gene encoding CD200R1 was deleted. CD200 stimulation was achieved by using either a soluble form of CD200 (CD200Fc) or overexpression of CD200 as a doxycycline-inducible transgene. Although broadly similar effects were seen, consistent with the hypothesis that triggering of CD200R2 does produce DCs with a characteristic TLR repertoire, there are subtle differences in suppression of alloreactivity achieved by CD200 delivered in these two manners, which is consistent with a complexity of CD200:CD200R engagement not previously appreciated.
Conversion of Tyrosine to the Inflammation-Associated Analog 3′-Nitrotyrosine at Either TCR- or MHC-Contact Positions Can Profoundly Affect Recognition of the MHC Class I-Restricted Epitope of Lymphocytic Choriomeningitis Virus Glycoprotein 33 by CD8 T Cells
Authors: Hardy Lani L. , Wick Darin A. , Webb John R. 
Published: April 2014

Abstract
Immunohistochemical detection of increased levels of protein-associated nitrotyrosine has become widely used as a surrogate marker of in situ inflammation. However, the potential consequences of protein-associated nitrotyrosine formation in terms of cellular immune recognition has received surprisingly little attention. Using a well-defined I-EK-restricted epitope of pigeon cytochrome c, we previously demonstrated that conversion of a single tyrosine residue to nitrotyrosine can have a profound effect on recognition by CD4 T cells. In this study, we used the MHC class I-restricted epitope of lymphocytic choriomeningitis virus glycoprotein (gp33) to demonstrate that conversion of tyrosine to nitrotyrosine can also profoundly affect recognition of MHC class I-restricted epitopes. Conversion of the Y4 residue of the gp33 epitope to nitrotyrosine completely abrogated recognition by gp33-specific T cells from P14 TCR-transgenic mice. In contrast, CD8+ T cells specific for “nitrated gp33” (NY-gp33) can be readily elicited in C57BL/6 mice after immunization with NY-gp33 peptide. Interestingly, T-T hybridomas specific for NY-gp33 peptide were found to fall into two distinct subsets, being specific for NY-gp33 presented in the context of either H-2Db or H-2Kb. This latter result is surprising in light of previous structural studies showing that Y4 comprises a critical TCR-contact residue when presented by H-2Db but that the same residue points downward into the peptide-binding groove of the MHC when presented by H-2Kb. Together, these results indicate that nitrotyrosine formation can impact T cell recognition both directly, through alteration of TCR-contact residues, or indirectly, through alterations in MHC-contact positions.
Preferential Development of CD4 and CD8 T Regulatory Cells in RasGRP1-Deficient Mice
Authors: Chen Xiaoxi , Priatel John J. , Chow Michael T. , Teh Hung-Sia 
Published: April 2014

Abstract
RasGRP1 and Sos are two Ras-guanyl-nucleotide exchange factors that link TCR signal transduction to Ras and MAPK activation. Recent studies demonstrate positive selection of developing thymocytes is crucially dependent on RasGRP1, whereas negative selection of autoreactive thymocytes appears to be RasGRP1 independent. However, the role of RasGRP1 in T regulatory (Treg) cell development and function is unknown. In this study, we characterized the development and function of CD4+CD25+Foxp3+ and CD8+CD44highCD122+ Treg lineages in RasGRP1−/− mice. Despite impaired CD4 Treg cell development in the thymus, the periphery of RasGRP1−/− mice contained significantly increased frequencies of CD4+Foxp3+ Treg cells that possessed a more activated cell surface phenotype. Furthermore, on a per cell basis, CD4+Foxp3+ Treg cells from mutant mice are more suppressive than their wild-type counterparts. Our data also suggest that the lymphopenic environment in the mutant mice plays a dominant role of favored peripheral development of CD4 Treg cells. These studies suggest that whereas RasGRP1 is crucial for the intrathymic development of CD4 Treg cells, it is not required for their peripheral expansion and function. By contrast to CD4+CD25+Foxp3+ T cells, intrathymic development of CD8+CD44highCD122+ Treg cells is unaffected by the RasGRP1−/− mutation. Moreover, RasGRP1−/− mice contained greater numbers of CD8+CD44highCD122+ T cells in the spleen, relative to wild-type mice. Activated CD8 Treg cells from RasGRP1−/− mice retained their ability to synthesize IL-10 and suppress the proliferation of wild-type CD8+CD122− T cells, albeit at a much lower efficiency than wild-type CD8 Treg cells.
Prevention of Allograft Tolerance by Bacterial Infection with Listeria monocytogenes
Authors: Wang Tongmin , Chen Luqiu , Ahmed Emily , Ma Lianli , Yin Dengping , Zhou Ping , Shen Jikun , Xu Honglin , Wang Chyung-Ru , Alegre Maria-Luisa , Chong Anita S. 
Published: April 2014

Abstract
Exposure to certain viruses and parasites has been shown to prevent the induction of transplantation tolerance in mice via the generation of cross-reactive memory T cell responses or the induction of bystander activation. Bacterial infections are common in the perioperative period of solid organ allograft recipients in the clinic, and correlations between bacterial infections and acute allograft rejection have been reported. However, whether bacterial infections at the time of transplantation have any effect on the generation of transplantation tolerance remains to be established. We used the Gram-positive intracellular bacterium Listeria monocytogenes (LM) as a model pathogen because its effects on immune responses are well described. Perioperative LM infection prevented cardiac and skin allograft acceptance induced by anti-CD154 and donor-specific transfusion in mice. LM-mediated rejection was not due to the generation of cross-reactive T cells and was largely independent of signaling via MyD88, an adaptor for most TLRs, IL-1, and IL-18. Instead, transplant rejection following LM infection was dependent on the expression of the phagosome-lysing pore former listeriolysin O and on type I IFN receptor signaling. Our results indicate that bacterial exposure at the time of transplantation can antagonize tolerogenic regimens by enhancing alloantigen-specific immune responses independently of the generation of cross-reactive memory T cells.
Fungal Proteases Induce Th2 Polarization through Limited Dendritic Cell Maturation and Reduced Production of IL-12
Authors: Lamhamedi-Cherradi Salah-Eddine , Martin Rachel Elizabeth , Ito Tomoki , Kheradmand Farrah , Corry David Brian , Liu Yong-Jun , Moyle Matthew 
Published: April 2014

Abstract
Allergens are capable of polarizing the T cell immune response toward a Th2 cytokine profile in a process that is mediated by dendritic cells (DCs). Proteases derived from Aspergillus species (Aspergillus proteases; AP) have been shown to induce a Th2-like immune response when administered directly to the airway and without adjuvant or prior priming immunizations at sites remote from the lung in models of allergic airway disease. To explore mechanisms that underlie the Th2 immune response, we have investigated the effect of AP on DC function. We found that human DCs derived from CD14+ monocytes from healthy donors underwent partial maturation when incubated with AP. Naive allogeneic T cells primed with AP-activated DCs proliferated and displayed enhanced production of IL-4 and reduced expression of IFN-γ as compared with naive T cells primed with LPS-activated DCs. Global gene expression analysis of DCs revealed relatively low expression of IL-12p40 in AP-activated DCs as compared with those activated by LPS, and this was confirmed at the protein level by ELISA. Exogenous IL-12p70 added to cocultures of DCs and T cells resulted in reduced IL-4 and increased IFN-γ expression when DCs were activated with AP. When the proteolytic activity of AP was neutralized by chemical inactivation it failed to up-regulate costimulatory molecules on DCs, and these DCs did not prime a Th2 response in naive T cells. These findings provide a mechanism for explaining how proteolytically active allergens could preferentially induce Th2 responses through limited maturation of DCs with reduced production of IL-12.