bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selective Activation of Human Intestinal Mast Cells by Escherichia coli Hemolysin
Authors: Krämer Sigrid , Sellge Gernot , Lorentz Axel , Krueger Dagmar , Schemann Michael , Feilhauer Katharina , Gunzer Florian , Bischoff Stephan C. 
Published: April 2014

Abstract
Mast cells (MCs) are recognized to play an important role in bacterial host defense in the murine system. In this study, we studied the interaction of human MCs, isolated from the intestine and purified to homogeneity, with different Escherichia coli and Shigella flexneri strains. We show that α-hemolysin (Hly)-producing E. coli strains induce the release of histamine, leukotrienes, and proinflammatory cytokines in intestinal MCs. In contrast, MCs were virtually unresponsive to S. flexneri and several Hly-negative E. coli strains, including the isogenic Hly-deficient mutants of Hly+ strains. Hly+ E. coli but not Hly− E. coli caused an increase in intracellular Ca2+ levels. Blocking of extracellular Ca2+ and of the calmodulin/calcineurin pathway by cyclosporin A inhibited the response to Hly+ E. coli. Furthermore, inhibition of MAPKs p38 and ERK reduces activation of MCs by Hly+ E. coli. In addition, using an ex vivo system, we directly record the histamine release by MCs located in the lamina propria after infection with Hly+ E. coli. Our data indicate that human intestinal mast cells interact with selected Gram-negative bacteria, establish E. coli Hly as a factor regulating MC effector functions, and argue further for a role of human MCs in innate immunity.
Mechanisms Underlying Blockade of Allograft Acceptance by TLR Ligands
Authors: Porrett Paige M. , Yuan Xueli , LaRosa David F. , Walsh Patrick T. , Yang Jaeseok , Gao Wenda , Li Peiying , Zhang Jidong , Ansari Javeed M. , Hancock Wayne W. , Sayegh Mohamed H. , Koulmanda Maria , Strom Terry B. , Turka Laurence A. 
Published: April 2014

Abstract
Immune activation via TLRs is known to prevent transplantation tolerance in multiple animal models. To investigate the mechanisms underlying this barrier to tolerance induction, we used complementary murine models of skin and cardiac transplantation in which prolonged allograft acceptance is either spontaneous or pharmacologically induced with anti-CD154 mAb and rapamycin. In each model, we found that prolonged allograft survival requires the presence of natural CD4+Foxp3+ T regulatory cells (Tregs), and that the TLR9 ligand CpG prevents graft acceptance both by interfering with natural Treg function and by promoting the differentiation of Th1 effector T cells in vivo. We further demonstrate that although Th17 cells differentiate from naive alloreactive T cells, these cells do not arise from natural Tregs in either CpG-treated or untreated graft recipients. Finally, we show that CpG impairs natural Treg suppressor capability and prevents Treg-dependent allograft acceptance in an IL-6-independent fashion. Our data therefore suggest that TLR signals do not prevent prolonged graft acceptance by directing natural Tregs into the Th17 lineage or by using other IL-6-dependent mechanisms. Instead, graft destruction results from the ability of CpG to drive Th1 differentiation and interfere with immunoregulation established by alloreactive natural CD4+Foxp3+ Tregs.
Macrophages Pulsed withStreptococcus pneumoniaeElicit a T Cell-Dependent Antibody Response upon Transfer into Naive Mice
Authors: Vasilevsky Sam , Colino Jesus , Puliaev Roman , Canaday David H. , Snapper Clifford M. 
Published: April 2014

AbstractMacrophages are less effective than DC at priming naive CD4+ T cells, suggesting that DC are unique in initiating T cell-dependent Ab responses. We compared the ability of DC and macrophages, pulsed in vitro with Streptococcus pneumoniae, to elicit protein- and polysaccharide-specific Ig isotype production upon adoptive transfer into naive mice. S. pneumoniae-activated DC secreted more proinflammatory and anti-inflammatory cytokines, expressed higher levels of surface MHC class II and CD40, and presented S. pneumoniae or recombinant pneumococcal surface protein A (PspA) to a PspA-specific T hybridoma more efficiently than macrophages. However, upon adoptive transfer into naive mice, S. pneumoniae-pulsed macrophages elicited an IgM or IgG anti-PspA and anti-polysaccharide response comparable in serum titers and IgG isotype distribution to that induced by DC. The IgG anti-PspA response, in contrast to the IgG anti-polysaccharide, to S. pneumoniae-pulsed macrophages was T cell-dependent. S. pneumoniae-pulsed macrophages that were paraformaldehyde-fixed before transfer or lacking expression of MHC class II or CD40 were highly defective in eliciting an anti-PspA response, although the anti-polysaccharide response was largely unaffected. To our knowledge, these data are the first to indicate that macrophages can play an active role in the induction of a T cell-dependent humoral immune response in a naive host.
Polyclonal Adaptive Regulatory CD4 Cells That Can Reverse Type I Diabetes Become Oligoclonal Long-Term Protective Memory Cells
Authors: Godebu Elana , Summers-Torres Daphne , Lin Melissa M. , Baaten Bas J. G. , Bradley Linda M. 
Published: April 2014

Abstract
Type 1 diabetes is a CD4 cell-dependent disease that results from destruction of insulin-producing β cells in pancreatic islets. An ideal therapy would reverse diabetes shortly after onset when islet function in not yet fully ablated, and also prevent re-emergence of disease through the generation of memory cells that control the autoimmune response. In this study, we show that adaptive/induced polyclonal regulatory (TR) cells, which contain islet-reactive cells, fulfill these criteria in the NOD mouse model. CD4 cells induced to express FoxP3, IL-10, and TGF-β1 in response to TCR signaling and TGF-β1 can reverse diabetes with clinical restoration of prediabetic serum levels of IL-10. Unlike naturally occurring TR cells, these adaptive TR cells persist indefinitely (&gt;1 year) as FoxP3+, CD25− memory cells that self-renew. Establishment of memory is accompanied by narrowing of the T cell repertoire to usage of a single TCR β-chain, Vβ11, implying selection by Ag. With islet-specific adaptive TR cells, we show that memory is functionally stable and transferable. Therefore, adaptive TR cells, which can be readily generated from normal CD4 populations and become focused by Ag with induction of memory, may provide a treatment and a vaccine for the long-term cure of diabetes making them attractive as immunotherapeutic agents.
Dual Signaling of MyD88 and TRIF Is Critical for Maximal TLR4-Induced Dendritic Cell Maturation
Authors: Shen Hua , Tesar Bethany M. , Walker Wendy E. , Goldstein Daniel R. 
Published: April 2014

Abstract
TLR4 is a unique TLR because downstream signaling occurs via two separate pathways, as follows: MyD88 and Toll IL-1 receptor (TIR) domain-containing adaptor-inducing IFN-β (TRIF). In this study, we compared and contrasted the interplay of these pathways between murine dendritic cells (DCs) and macrophages during LPS stimulation. During TLR4 activation, neither pathway on its own was critical for up-regulation of costimulatory molecules in DCs, whereas the up-regulation of costimulatory molecules was largely TRIF dependent in macrophages. LPS-induced secreted factors, of which type I IFNs were one of the active components, played a larger role in promoting the up-regulation of costimulatory molecules in macrophages than DCs. In both cell types, MyD88 and TRIF pathways together accounted for the inflammatory response to LPS activation. Furthermore, signaling of both adaptors allowed maximal T cell priming by LPS-matured DCs, with MyD88 playing a larger role than TRIF. In sum, in our experimental systems, TRIF signaling plays a more important role in LPS-induced macrophage activation than in DC activation.
Identification of an Evolutionarily Conserved Transcriptional Signature of CD8 Memory Differentiation That Is Shared by T and B Cells
Authors: Haining W. Nicholas , Ebert Benjamin L. , Subrmanian Aravind , Wherry E. John , Eichbaum Quentin , Evans John W. , Mak Raymond , Rivoli Stephen , Pretz Jennifer , Angelosanto Jill , Smutko John S. , Walker Bruce D. , Kaech Susan M. , Ahmed Rafi , Nadler Lee M. , Golub Todd R. 
Published: April 2014

Abstract
After Ag encounter, naive lymphocytes differentiate into populations of memory cells that share a common set of functions including faster response to Ag re-exposure and the ability to self-renew. However, memory lymphocytes in different lymphocyte lineages are functionally and phenotypically diverse. It is not known whether discrete populations of T and B cells use similar transcriptional programs during differentiation into the memory state. We used cross-species genomic analysis to examine the pattern of genes up-regulated during the differentiation of naive lymphocytes into memory cells in multiple populations of human CD4, CD8, and B cell lymphocytes as well as two mouse models of memory development. We identified and validated a signature of genes that was up-regulated in memory cells compared with naive cells in both human and mouse CD8 memory differentiation, suggesting marked evolutionary conservation of this transcriptional program. Surprisingly, this conserved CD8 differentiation signature was also up-regulated during memory differentiation in CD4 and B cell lineages. To validate the biologic significance of this signature, we showed that alterations in this signature of genes could distinguish between functional and exhausted CD8 T cells from a mouse model of chronic viral infection. Finally, we generated genome-wide microarray data from tetramer-sorted human T cells and showed profound differences in this differentiation signature between T cells specific for HIV and those specific for influenza. Thus, our data suggest that in addition to lineage-specific differentiation programs, T and B lymphocytes use a common transcriptional program during memory development that is disrupted in chronic viral infection.
Modulation of T Cell Activation by Stomatin-Like Protein 2
Authors: Kirchhof Mark G. , Chau Luan A. , Lemke Caitlin D. , Vardhana Santosh , Darlington Peter J. , Márquez Maria E. , Taylor Roy , Rizkalla Kamilia , Blanca Isaac , Dustin Michael L. , Madrenas Joaquín 
Published: April 2014

Abstract
T cell activation through the Ag receptor (TCR) requires sustained signaling from signalosomes within lipid raft microdomains in the plasma membrane. In a proteomic analysis of lipid rafts from human T cells, we identified stomatin-like protein (SLP)-2 as a candidate molecule involved in T cell activation through the Ag receptor. In this study, we show that SLP-2 expression in human primary lymphocytes is up-regulated following in vivo and ex vivo activation. In activated T cells, SLP-2 interacts with components of TCR signalosomes and with polymerized actin. More importantly, up-regulation of SLP-2 expression in human T cell lines and primary peripheral blood T cells increases effector responses, whereas down-regulation of SLP-2 expression correlates with loss of sustained TCR signaling and decreased T cell activation. Our data suggest that SLP-2 is an important player in T cell activation by ensuring sustained TCR signaling, which is required for full effector T cell differentiation, and point to SLP-2 as a potential target for immunomodulation.
Identification of Residues in the Cμ4 Domain of Polymeric IgM Essential for Interaction withPlasmodium falciparumErythrocyte Membrane Protein 1 (PfEMP1)
Authors: Ghumra Ashfaq , Semblat Jean-Philippe , McIntosh Richard S. , Raza Ahmed , Rasmussen Ingunn B. , Braathen Ranveig , Johansen Finn-Eirik , Sandlie Inger , Mongini Patricia K. , Rowe J. Alexandra , Pleass Richard J. 
Published: April 2014

AbstractThe binding of nonspecific human IgM to the surface of infected erythrocytes is important in rosetting, a major virulence factor in the pathogenesis of severe malaria due to Plasmodium falciparum, and IgM binding has also been implicated in placental malaria. Herein we have identified the IgM-binding parasite ligand from a virulent P. falciparum strain as PfEMP1 (TM284var1 variant), and localized the region within this PfEMP1 variant that binds IgM (DBL4β domain). We have used this parasite IgM-binding protein to investigate the interaction with human IgM. Interaction studies with domain-swapped Abs, IgM mutants, and anti-IgM mAbs showed that PfEMP1 binds to the Fc portion of the human IgM H chain and requires the IgM Cμ4 domain. Polymerization of IgM was shown to be crucial for the interaction because PfEMP1 binding did not occur with mutant monomeric IgM molecules. These results with PfEMP1 protein have physiological relevance because infected erythrocytes from strain TM284 and four other IgM-binding P. falciparum strains showed analogous results to those seen with the DBL4β domain. Detailed investigation of the PfEMP1 binding site on IgM showed that some of the critical amino acids in the IgM Cμ4 domain are equivalent to those regions of IgG and IgA recognized by Fc-binding proteins from bacteria, suggesting that this region of Ig molecules may be of major functional significance in host-microbe interactions. We have therefore shown that PfEMP1 is an Fc-binding protein of malaria parasites specific for polymeric human IgM, and that it shows functional similarities with Fc-binding proteins from pathogenic bacteria.
Tetrameric and Homodimeric Camelid IgGs Originate from the Same IgH Locus
Authors: Achour Ikbel , Cavelier Patricia , Tichit Magali , Bouchier Christiane , Lafaye Pierre , Rougeon François 
Published: April 2014

Abstract
In addition to producing conventional tetrameric IgGs, camelids have the particularity of producing a functional homodimeric IgG type lacking L (light) chains and only made up of two H (heavy) chains. This nonconventional IgG type is characterized by variable and constant regions referred to as VHH and CHH, respectively, and which differ from conventional VH and CH counterparts. Although the structural properties of homodimeric IgGs have been well investigated, the genetic bases involved in their generation are still largely unknown. In this study, we characterized the organization of genes coding for the H chains of tetrameric and homodimeric IgGs by constructing an alpaca (Lama pacos) genomic cosmid library. We showed that a single IgH locus in alpaca chromosome 4 contains all of the genetic elements required for the generation of the two types of Igs. The alpaca IgH locus is composed of a V region that contains both VHH and VH genes followed by a unique DH-JH cluster and C region genes, which include both CHH and CH genes. Although this general gene organization greatly resembles that of other typical mammalian Vn-Dn-Jn-Cn translocon IgH loci, the intermixed gene organization within the alpaca V and C regions reveals a new type of translocon IgH locus. Furthermore, analyses of cDNA coding for the membrane forms of IgG and IgM present in alpaca peripheral blood B cells are most consistent with the notion that the development of a B cell bearing homodimeric IgG passes through an IgM+ stage, similar to the case for conventional IgG.
Genetic Analysis of SH2D4A, a Novel Adapter Protein Related to T Cell-Specific Adapter and Adapter Protein in Lymphocytes of Unknown Function, Reveals a Redundant Function in T Cells
Authors: Lapinski Philip E. , Oliver Jennifer A. , Kamen Lynn A. , Hughes Elizabeth D. , Saunders Thomas L. , King Philip D. 
Published: April 2014

Abstract
T cell-specific adapter (TSAd) protein and adapter protein in lymphocytes of unknown function (ALX) are two related Src homology 2 (SH2) domain-containing signaling adapter molecules that have both been shown to regulate TCR signal transduction in T cells. TSAd is required for normal TCR-induced synthesis of IL-2 and other cytokines in T cells and acts at least in part by promoting activation of the LCK protein tyrosine kinase at the outset of the TCR signaling cascade. By contrast, ALX functions as a negative-regulator of TCR-induced IL-2 synthesis through as yet undetermined mechanisms. In this study, we report a novel T cell-expressed adapter protein named SH2D4A that contains an SH2 domain that is highly homologous to the TSAd protein and ALX SH2 domains and that shares other structural features with these adapters. To examine the function of SH2D4A in T cells we produced SH2D4A-deficient mice by homologous recombination in embryonic stem cells. T cell development, homeostasis, proliferation, and function were all found to be normal in these mice. Furthermore, knockdown of SH2D4A expression in human T cells did not impact upon their function. We conclude that in contrast to TSAd and ALX proteins, SH2D4A is dispensable for TCR signal transduction in T cells.
Lipoproteins of Listeria monocytogenes Are Critical for Virulence and TLR2-Mediated Immune Activation
Authors: Machata Silke , Tchatalbachev Svetlin , Mohamed Walid , Jänsch Lothar , Hain Torsten , Chakraborty Trinad 
Published: April 2014

Abstract
Numerous cell surface components of Listeria influence and regulate innate immune recognition and virulence. Here, we demonstrate that lipidation of prelipoproteins in Listeria monocytogenes is required to promote NF-κB activation via TLR2. In HeLa cells transiently expressing TLR2, L. monocytogenes and Listeria innocua mutants lacking the prolipoprotein diacylglyceryl transferase (lgt) gene are unable to induce TLR2-dependent activation of NF-κB, a property intrinsic to their isogenic parental strains. TLR2-dependent immune recognition is directed to secreted, soluble lipoproteins as evidenced by the sensitivity of the response to lipoprotein lipase. Studies of bone marrow-derived macrophages of C57BL/6 wild-type and TLR2-deficient mice infected with wild-type and lgt mutant strains indicate that the absence of host TLR2 receptor signaling has consequences similar to those of the absence of the bacterial TLR2 ligand, i.e., a delay in cellular immune responses directed toward the bacterium. Infection studies with the wild-type and TLR2−/− mice indicated attenuation of the lgt deletion mutant in both mouse strains, implying multiple roles of lipoproteins during infection. Further characterization of the Δlgt mutant indicated that it is impaired for both invasion and intracellular survival and exhibits increased susceptibility to cationic peptides. Our studies identify lipoproteins as the immunologically active ligand of TLR2 and assign a critical role for this receptor in the recognition of these bacteria during infection, but they also reveal the overall importance of the lipoproteins for the pathogenicity of Listeria.
Type I IFNs Enhance Susceptibility toChlamydia muridarumLung Infection by Enhancing Apoptosis of Local Macrophages
Authors: Qiu Hongyu , Fan Yijun , Joyee Antony George , Wang Shuhe , Han Xiaobing , Bai Hong , Jiao Lei , Van Rooijen Nico , Yang Xi 
Published: April 2014

AbstractType I IFNs (IFNIs) have pleiotropic functions in regulating host innate and adaptive immune responses to pathogens. To elucidate the role of IFNIs in host resistance to chlamydial infection in vivo, we compared IFN-α/β receptor knockout (IFNAR−/−) and wild-type control mice in susceptibility to Chlamydia trachomatis mouse pneumonitis (Chlamydia muridarum) lung infection. We found that the IFNAR−/− mice were significantly more resistant to C. muridarum infection showing less bacterial burden and bodyweight loss, and milder pathological changes. However, IFN-γ response, which is believed to be critical in host defense against chlamydial infection, was similar between the wild-type and IFNAR−/− mice. More importantly, TUNEL analysis showed less macrophage apoptosis in IFNAR−/− mice, which was consistent with lower expressions of IFNI-induced apoptotic factors, TRAIL, Daxx, and PKR. Furthermore, depletion of lung macrophages with dichloromethylene diphosphonate-liposome significantly increased the susceptibility of the IFNAR−/− mice to C. muridarum, confirming the importance of macrophages. Overall, the data indicate that IFNIs play a promoting role in C. muridarum lung infection, largely through increase of local macrophage apoptosis.
CD8+ T Lymphocytes Control Murine Cytomegalovirus Replication in the Central Nervous System of Newborn Animals
Authors: Bantug Glenn R. B. , Cekinovic Djurdijca , Bradford Russell , Koontz Thad , Jonjic Stipan , Britt William J. 
Published: April 2014

Abstract
Human CMV infection of the neonatal CNS results in long-term neurologic sequelae. To define the pathogenesis of fetal human CMV CNS infections, we investigated mechanisms of virus clearance from the CNS of neonatal BALB/c mice infected with murine CMV (MCMV). Virus titers peaked in the CNS between postnatal days 10–14 and infectious virus was undetectable by postnatal day 21. Congruent with virus clearance was the recruitment of CD8+ T cells into the CNS. Depletion of CD8+ T cells resulted in death by postnatal day 15 in MCMV-infected animals and increased viral loads in the liver, spleen, and the CNS, suggesting an important role for these cells in the control of MCMV replication in the newborn brain. Examination of brain mononuclear cells revealed that CD8+ T cell infiltrates expressed high levels of CD69, CD44, and CD49d. IE1168-specific CD8+ T cells accumulated in the CNS and produced IFN-γ and TNF-α but not IL-2 following peptide stimulation. Moreover, adoptive transfer of brain mononuclear cells resulted in decreased virus burden in immunodepleted MCMV-infected syngeneic mice. Depletion of the CD8+ cell population following transfer eliminated control of virus replication. In summary, these results show that functionally mature virus-specific CD8+ T cells are recruited to the CNS in mice infected with MCMV as neonates.
Blimp-1 Attenuates Th1 Differentiation by Repression of ifng, tbx21, and bcl6 Gene Expression
Authors: Cimmino Luisa , Martins Gislaine A. , Liao Jerry , Magnusdottir Erna , Grunig Gabriele , Perez Rocio K. , Calame Kathryn L. 
Published: April 2014

Abstract
T cell-specific deletion of Blimp-1 causes abnormal T cell homeostasis and function, leading to spontaneous, fatal colitis in mice. Herein we explore the role of Blimp-1 in Th1/Th2 differentiation. Blimp-1 mRNA and protein are more highly expressed in Th2 cells compared with Th1 cells, and Blimp-1 attenuates IFN-γ production in CD4 cells activated under nonpolarizing conditions. Although Blimp-1-deficient T cells differentiate normally to Th2 cytokines in vitro, Blimp-1 is required in vivo for normal Th2 humoral responses to NP-KLH (4-hydroxy-3-nitrophenylacetyl/keyhole lymphocyte hemocyanin) immunization. Lack of Blimp-1 in CD4 T cells causes increased IFN-γ, T-bet, and Bcl-6 mRNA. By chromatin immunoprecipitation we show that Blimp-1 binds directly to a distal regulatory region in the ifng gene and at multiple sites in tbx21 and bcl6 genes. Our data provide evidence that Blimp-1 functions in Th2 cells to reinforce Th2 differentiation by repressing critical Th1 genes.