bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transcription-Dependent Somatic Hypermutation Occurs at Similar Levels on Functional and Nonfunctional Rearranged IgH Alleles
Authors: Delpy Laurent , Sirac Christophe , Le Morvan Caroline , Cogné Michel 
Published: April 2014

AbstractAllelic exclusion of IgH chain expression is stringently established before or during early B cell maturation. It likely relies both on cellular mechanisms, selecting those cells in which a single receptor allows the best possible Ag response, and on molecular restrictions of gene accessibility to rearrangement. The extent to which transcriptional control may be involved is unclear. Transcripts arising from nonfunctional alleles would undergo nonsense-mediated degradation and their virtual absence in mature cells cannot ensure that transcription per se is down-regulated. By contrast, somatic hypermutation may provide an estimate of primary transcription in Ag-activated cells since both processes are directly correlated. For coding regions, the rate and nature of mutations also depend upon Ag binding constraints. By sequencing intronic sequence downstream mouse VDJ genes, we could show in the absence of such constraints that somatic hypermutation intrinsically targets nonfunctional rearranged alleles at a frequency approaching that of functional alleles, suggesting that transcription also proceeds on both alleles at a similar rate. By contrast and confirming the strong dependency of somatic hypermutation upon transcription, we show that artificial blockade of transcription on the nonfunctional allele by a knock-in neomycin resistance cassette keeps the VDJ region unmutated even when its promoter is intact and when it is fully rearranged.
Histidines Are Critical for Heparin-Dependent Activation of Mast Cell Tryptase
Authors: Hallgren Jenny , Bäckström Stefan , Estrada Sergio , Thuveson Maria , Pejler Gunnar 
Published: April 2014

Abstract
Mast cell tryptase is a tetrameric serine protease that is stored in complex with negatively charged heparin proteoglycans in the secretory granule. Tryptase has potent proinflammatory properties and has been implicated in diverse pathological conditions such as asthma and fibrosis. Previous studies have shown that tryptase binds tightly to heparin, and that heparin is required in the assembly of the tryptase tetramer as well as for stabilization of the active tetramer. Because the interaction of tryptase with heparin is optimal at acidic pH, we investigated in this study whether His residues are of importance for the heparin binding, tetramerization, and activation of the tryptase mouse mast cell protease 6. Molecular modeling of mouse mast cell protease 6 identified four His residues, H35, H106, H108, and H238, that are conserved among pH-dependent tryptases and are exposed on the molecular surface, and these four His residues were mutated to Ala. In addition, combinations of different mutations were prepared. Generally, the single His-Ala mutations did not cause any major defects in heparin binding, activation, or tetramerization, although some effect of the H106A mutation was observed. However, when several mutations were combined, large defects in all of these parameters were observed. Of the mutants, the triple mutant H106A/H108A/H238A was the most affected with an almost complete inability to bind to heparin and to form active tryptase tetramers. Taken together, this study shows that surface-exposed histidines mediate the interaction of mast cell tryptase with heparin and are of critical importance in the formation of active tryptase tetramers.
B Cell Lipid Rafts Regulate Both Peptide-Dependent and Peptide-Independent APC-T Cell Interaction
Authors: Setterblad Niclas , Bécart Stéphane , Charron Dominique , Mooney Nuala 
Published: April 2014

Abstract
Formation of an immunological synapse (IS) between APCs and T CD4+ lymphocytes is a key event in the initiation and the termination of the cognate immune response. We have analyzed the contribution of the APC to IS formation and report the implication of the actin cytoskeleton, the signaling proteins and the lipid rafts of B lymphocytes. Recruitment of MHC class II molecules to the IS is concomitant with actin cytoskeleton-dependent B cell raft recruitment. B cell actin cytoskeleton disruption abrogates both IS formation and T cell activation, whereas protein kinase C inhibition only impairs T cell activation. Pharmacological B cell lipid raft disruption inhibited peptide-dependent T lymphocyte activation and induced peptide-independent but HLA-DR-restricted APC-T cell conjugate formation. Such peptide-independent conjugates did not retain the ability to activate T cells. Thus, B cell lipid rafts are bifunctional by regulating T cell activation and imposing peptide stringency.
IL-23 Provides a Limited Mechanism of Resistance to Acute Toxoplasmosis in the Absence of IL-12
Authors: Lieberman Linda A. , Cardillo Fabiola , Owyang Alexander M. , Rennick Donna M. , Cua Daniel J. , Kastelein Robert A. , Hunter Christopher A. 
Published: April 2014

Abstract
IL-23 and IL-12 are heterodimeric cytokines which share the p40 subunit, but which have unique second subunits, IL-23p19 and IL-12p35. Since p40 is required for the development of the Th1 type response necessary for resistance to Toxoplasma gondii, studies were performed to assess the role of IL-23 in resistance to this pathogen. Increased levels of IL-23 were detected in mice infected with T. gondii and in vitro stimulation of dendritic cells with this pathogen resulted in increased levels of mRNA for this cytokine. To address the role of IL-23 in resistance to T. gondii, mice lacking the p40 subunit (common to IL-12 and IL-23) and mice that lack IL-12 p35 (specific for IL-12) were infected and their responses were compared. These studies revealed that p40−/− mice rapidly succumbed to toxoplasmosis, while p35−/− mice displayed enhanced resistance though they eventually succumbed to this infection. In addition, the administration of IL-23 to p40−/− mice infected with T. gondii resulted in a decreased parasite burden and enhanced resistance. However, the enhanced resistance of p35−/− mice or p40−/− mice treated with IL-23 was not associated with increased production of IFN-γ. When IL-23p19−/− mice were infected with T. gondii these mice developed normal T cell responses and controlled parasite replication to the same extent as wild-type mice. Together, these studies indicate that IL-12, not IL-23, plays a dominant role in resistance to toxoplasmosis but, in the absence of IL-12, IL-23 can provide a limited mechanism of resistance to this infection.
Innate BALB/c Enteric Epithelial Responses to Trichinella spiralis: Inducible Expression of a Novel Goblet Cell Lectin, Intelectin-2, and Its Natural Deletion in C57BL/10 Mice
Authors: Pemberton Alan D. , Knight Pamela A. , Gamble John , Colledge William H. , Lee Jin-Kyu , Pierce Michael , Miller Hugh R. P. 
Published: April 2014

Abstract
Infection of mice with the nematode parasite Trichinella spiralis induces changes in the proteome of the jejunal epithelium, including substantial up-regulation of a novel variant of interlectin. In this study we sequence this novel lectin, termed intelectin-2, and compare expression levels during T. spiralis infection of resistant (BALB/c) with susceptible (C57BL/10) mouse strains. Intelectin-2 was cloned and sequenced from BALB/c mRNA extracted on day 14 of infection, and was found to have 91% amino acid identity with intelectin (within our study termed intelectin-1). Intelectin-2 transcripts were up-regulated early (day 3) during infection with T. spiralis in BALB/c mice, suggesting an innate response, and levels remained high through to day 14 (time of parasite rejection). Immunohistochemistry of jejunal sections with a rabbit polyclonal Ab to Xenopus laevis 35-kDa cortical granule lectin (XL35; 68% identity with intelectin-2) followed a similar pattern, with intense labeling of goblet and Paneth cells at day 14. However, intelectin-2 transcripts and protein were absent, and immunohistochemistry negative when C57BL/10 mice were infected with T. spiralis. Genomic PCR and Southern blotting confirmed that the intelectin-2 gene is absent from the C57BL/10 genome. The presence of intelectin-2 in resistant BALB/c mice, its absence from the susceptible C57BL/10 strain and the kinetics of its up-regulation during T. spiralis infection suggest that this novel lectin may serve a protective role in the innate immune response to parasite infection.
Bordetella Type III Secretion and Adenylate Cyclase Toxin Synergize to Drive Dendritic Cells into a Semimature State
Authors: Skinner Jason A. , Reissinger Annette , Shen Hao , Yuk Ming H. 
Published: April 2014

Abstract
Bordetella bronchiseptica establishes persistent infection of the murine respiratory tract. We hypothesize that long-term colonization is mediated in part by bacteria-driven modulation of dendritic cells (DCs) leading to altered adaptive immune responses. Bone marrow-derived DCs (BMDCs) from C57BL/6 mice infected with live B. bronchiseptica exhibited high surface expression of MHCII, CD86, and CD80. However, B. bronchiseptica-infected BMDCs did not exhibit significant increases in CD40 surface expression and IL-12 secretion compared with BMDCs treated with heat-killed B. bronchiseptica. The B. bronchiseptica type III secretion system (TTSS) mediated the increase in MHCII, CD86, and CD80 surface expression, while the inhibition of CD40 and IL-12 expression was mediated by adenylate cyclase toxin (ACT). IL-6 secretion was independent of the TTSS and ACT. These phenotypic changes may result from differential regulation of MAPK signaling in DCs. Wild-type B. bronchiseptica activated the ERK 1/2 signaling pathway in a TTSS-dependent manner. Additionally, ACT was found to inhibit p38 signaling. These data suggest that B. bronchiseptica drive DC into a semimature phenotype by altering MAPK signaling. These semimature DCs may induce tolerogenic immune responses that allow the persistent colonization of B. bronchiseptica in the host respiratory tract.
Recognition of Variant HIV-1 Epitopes from Diverse Viral Subtypes by Vaccine-Induced CTL
Authors: McKinney Denise M. , Skvoretz Rhonda , Livingston Brian D. , Wilson Cara C. , Anders Michelle , Chesnut Robert W. , Sette Alessandro , Essex Max , Novitsky Vladimir , Newman Mark J. 
Published: April 2014

Abstract
Recognition by CD8+ T lymphocytes (CTL) of epitopes that are derived from conserved gene products, such as Gag and Pol, is well documented and conceptually supports the development of epitope-based vaccines for use against diverse HIV-1 subtypes. However, many CTL epitopes from highly conserved regions within the HIV-1 genome are highly variable, when assessed by comparison of amino acid sequences. The TCR is somewhat promiscuous with respect to peptide binding, and, as such, CTL can often recognize related epitopes. In these studies, we evaluated CTL recognition of five sets of variant HIV-1 epitopes restricted to HLA-A*0201 and HLA-A*1101 using HLA transgenic mice. We found that numerous different amino acid substitutions can be introduced into epitopes without abrogating their recognition by CTL. Based on our findings, we constructed an algorithm to predict those CTL epitopes capable of inducing responses in the HLA transgenic mice to the greatest numbers of variant epitopes. Similarity of CTL specificity for variant epitopes was demonstrated for humans using PBMC from HIV-1-infected individuals and CTL lines produced in vitro using PBMC from HIV-1-uninfected donors. We believe the ability to predict CTL epitope immunogenicity and recognition patterns of variant epitopes can be useful for designing vaccines against multiple subtypes and circulating recombinant forms of HIV-1.
Th Cell-Independent Immune Responses to Chimeric Hemagglutinin/Simian Human Immunodeficiency Virus-Like Particles Vaccine
Authors: Yao Qizhi , Zhang Rongxin , Guo Lizheng , Li Min , Chen Changyi 
Published: April 2014

Abstract
CD4+ Th cells are believed to be essential for the induction of humoral and cellular immune responses. In this study we tested the effect and possible mechanisms of the major antigenic component in influenza, hemagglutinin (HA), in helping HIV Env to induce immune responses in CD4+ T cell knockout (CD4 KO) mice. Simian HIV virus-like particles (SHIV VLPs) or phenotypically mixed chimeric influenza HA/SHIV VLPs were used as immunogens to immunize CD4 KO mice either i.p. or intranasally (i.n.). We found that chimeric HA/SHIV VLPs significantly induced a greater IgG Ab response in both i.p. and i.n. immunized mice and a greater IgA Ab response in mucosal washes in i.n. immunized mice compared with SHIV VLPs. Importantly, chimeric HA/SHIV VLPs induced ∼3-fold higher neutralizing Ab titers against HIV 89.6 than SHIV VLPs in the absence of CD4+ T cell help. There was also ∼40% more specific lysis of the HIV Env-expressing target cells in chimeric HA/SHIV VLP-immunized than in SHIV VLP-immunized CD4 KO mouse splenocytes. Moreover, we have found that chimeric HA/SHIV VLPs could efficiently bind and activate dendritic cells and stimulate the activated dendritic cells to secret TNF-α and IFN-γ. Therefore, chimeric HA/SHIV VLPs could efficiently prime and activate APCs, which could, in turn, induce immune responses in a CD4+ T cell-independent manner. This study suggests a novel adjuvant role of influenza HA as well as a new strategy to develop more effective therapeutic vaccines for AIDS patients with low CD4+ T cell counts.
Bordetella pertussis Lipopolysaccharide Resists the Bactericidal Effects of Pulmonary Surfactant Protein A
Authors: Schaeffer Lyndsay M. , McCormack Francis X. , Wu Huixing , Weiss Alison A. 
Published: April 2014

Abstract
Surfactant protein A (SP-A) plays an important role in the innate immune defense of the respiratory tract. SP-A binds to lipid A of bacterial LPS, induces aggregation, destabilizes bacterial membranes, and promotes phagocytosis by neutrophils and macrophages. In this study, SP-A interaction with wild-type and mutant LPS of Bordetella pertussis, the causative agent of whooping cough, was examined. B. pertussis LPS has a branched core structure with a nonrepeating trisaccharide, rather than a long-chain repeating O-Ag. SP-A did not bind, aggregate, nor permeabilize wild-type B. pertussis. LPS mutants lacking even one of the sugars in the terminal trisaccharide were bound and aggregated by SP-A. SP-A enhanced phagocytosis by human monocytes of LPS mutants that were able to bind SP-A, but not wild-type bacteria. SP-A enhanced phagocytosis by human neutrophils of LPS-mutant strains, but only in the absence of functional adenylate cyclase toxin, a B. pertussis toxin that has been shown to depress neutrophil activity. We conclude that the LPS of wild-type B. pertussis shields the bacteria from SP-A-mediated clearance, possibly by sterically limiting access to the lipid A region.
Characterization of a Mycobacterium tuberculosis Peptide That Is Recognized by Human CD4+ and CD8+ T Cells in the Context of Multiple HLA Alleles
Authors: Shams Homayoun , Klucar Peter , Weis Steven E. , Lalvani Ajit , Moonan Patrick K. , Safi Hassan , Wizel Benjamin , Ewer Katie , Nepom Gerald T. , Lewinsohn David M. , Andersen Peter , Barnes Peter F. 
Published: April 2014

Abstract
The secreted Mycobacterium tuberculosis 10-kDa culture filtrate protein (CFP)10 is a potent T cell Ag that is recognized by a high percentage of persons infected with M. tuberculosis. We determined the molecular basis for this widespread recognition by identifying and characterizing a 15-mer peptide, CFP1071–85, that elicited IFN-γ production and CTL activity by both CD4+ and CD8+ T cells from persons expressing multiple MHC class II and class I molecules, respectively. CFP1071–85 contained at least two epitopes, one of 10 aa (peptide T1) and another of 9 aa (peptide T6). T1 was recognized by CD4+ cells in the context of DRB1*04, DR5*0101, and DQB1*03, and by CD8+ cells of A2+ donors. T6 elicited responses by CD4+ cells in the context of DRB1*04 and DQB1*03, and by CD8+ cells of B35+ donors. Deleting a single amino acid from the amino or carboxy terminus of either peptide markedly reduced IFN-γ production, suggesting that they are minimal epitopes for both CD4+ and CD8+ cells. As far as we are aware, these are the shortest microbial peptides that have been found to elicit responses by both T cell subpopulations. The capacity of CFP1071–85 to stimulate IFN-γ production and CTL activity by CD4+ and CD8+ cells from persons expressing a spectrum of MHC molecules suggests that this peptide is an excellent candidate for inclusion in a subunit antituberculosis vaccine.
Heat Shock Protein-Mediated Cross-Presentation of Exogenous HIV Antigen on HLA Class I and Class II
Authors: SenGupta Devi , Norris Philip J. , Suscovich Todd J. , Hassan-Zahraee Mina , Moffett Howell F. , Trocha Alicja , Draenert Rika , Goulder Philip J. R. , Binder Robert J. , Levey Daniel L. , Walker Bruce D. , Srivastava Pramod K. , Brander Christian 
Published: April 2014

AbstractStrong CD4+ and CD8+ T cell responses are considered important immune components for controlling HIV infection, and their priming may be central to an effective HIV vaccine. We describe in this study an approach by which multiple CD4+ and CD8+ T cell epitopes are processed and presented from an exogenously added HIV-1 Gag-p24 peptide of 32 aa complexed to heat shock protein (HSP) gp96. CD8+ T cell recognition of the HSP/peptide complex, but not the peptide alone, was inhibited by brefeldin A, suggesting an endoplasmic reticulum-dependent pathway. This is the first report to describe efficient processing and simultaneous presentation of overlapping class I- and class II-restricted epitopes from the same extracellularly added precursor peptide complexed to HSP. Given previous reports of the strong immunogenicity of HSP/peptide complexes, the present data suggest that HSP-complexed peptides containing multiple MHC class I- and class II-restricted epitopes represent potential vaccine candidates for HIV and other viral infections suitable to induce effective CTL memory by simultaneously providing CD4 T cell help.
MyD88 Plays a Unique Role in Host Defense but Not Arthritis Development in Lyme Disease
Authors: Bolz Devin D. , Sundsbak Rhianna S. , Ma Ying , Akira Shizuo , Kirschning Carsten J. , Zachary James F. , Weis John H. , Weis Janis J. 
Published: April 2014

Abstract
To assess the contribution of TLR signaling in the host response to Borrelia burgdorferi, mice deficient in the common TLR adaptor protein, myeloid differentiation factor 88 (MyD88), were infected with B. burgdorferi. MyD88-deficient mice harbored extremely high levels of B. burgdorferi in tissues when compared with wild-type littermates and greater amounts of spirochetes in tissues than TLR2-deficient mice. These findings suggest that, in addition to TLR2, other MyD88-dependent pathways play a significant role in the host defense to B. burgdorferi. MyD88−/− mice maintained the ability to produce Abs directed against B. burgdorferi. Partial clearance of spirochetes was evident in long term infection studies and immune sera from MyD88-deficient mice were able to protect naive mice from infection with B. burgdorferi. Thus, the acquired immune response appeared to be functional in MyD88−/− mice, and the inability to control spirochete numbers was due to a failure of cells involved in innate defenses. Although macrophages from MyD88−/− mice responded poorly to Borrelia sonicate in vitro, MyD88−/− mice still developed an inflammatory arthritis after infection with B. burgdorferi characterized by an influx of neutrophils and mononuclear cells. The findings presented here point to a dichotomy between the recruitment of inflammatory cells to tissue and an inability of these cells to kill localized spirochetes.
Responses of Neutrophils to Anti-Integrin Antibodies Depends on Costimulation through Low Affinity FcγRs: Full Activation Requires Both Integrin and Nonintegrin Signals
Authors: Jakus Zoltán , Berton Giorgio , Ligeti Erzsébet , Lowell Clifford A. , Mócsai Attila 
Published: April 2014

Abstract
The relative contribution of integrin and nonintegrin signals to neutrophil activation is incompletely understood. Immobilized anti-integrin Abs were previously shown to induce robust activation of neutrophils without any additional stimulus, suggesting that cross-linking of integrins is sufficient for full activation of the cells. However, the possible contribution from other receptors has not been tested in this system. In this study, we show that neutrophil responses to anti-integrin Abs requires costimulation through low-affinity FcγRs. Murine neutrophils lacking the FcR γ-chain or FcγRIII failed to respond to immobilized Abs against β1, β2, or β3 integrins and the activation of wild-type cells could be prevented by blocking Abs against FcγRII/III. Plate-bound anti-CD18 Abs initiated a respiratory burst from human neutrophils, but this response was abrogated when the F(ab′)2 of the same Abs were used or the cells were preincubated with FcγRIIA-blocking Abs. Lack of FcγRIII or administration of FcγR-blocking Abs had no effect on responses of TNF-stimulated cells plated on fibrinogen or rICAM-1. TNF restored the respiratory burst of FcγRIII-deficient neutrophils plated on anti-CD18 mAbs. The p38 MAPK inhibitor SB203580 attenuated the responses of neutrophils to anti-CD18 mAbs or TNF stimulation on a fibrinogen surface. Taken together, these results indicate that activation of low-affinity FcγRs is required for neutrophil responses induced by anti-integrin Abs and suggest that a second coactivation signal (e.g., through TNF or FcR ligation) is indispensable for full integrin-mediated activation of neutrophils. These second signals are interchangeable and they may converge on the p38 MAPK.
MIP-1γ Promotes Receptor Activator of NF-κB Ligand-Induced Osteoclast Formation and Survival
Authors: Okamatsu Yoshimasa , Kim David , Battaglino Ricardo , Sasaki Hajime , Späte Ulrike , Stashenko Philip 
Published: April 2014

Abstract
Chemokines play an important role in immune and inflammatory responses by inducing migration and adhesion of leukocytes, and have also been reported to modulate osteoclast differentiation from hemopoietic precursor cells of the monocyte-macrophage lineage. In this study, we examined the effect of MIP-1γ, a C-C chemokine family member, on receptor activator of NF-κB ligand (RANKL)-stimulated osteoclast differentiation, survival, and activation. RANKL induced osteoclasts to dramatically increase production of MIP-1γ and to also express the MIP-1γ receptor CCR1, but had only minor effects on the related C-C chemokines MIP-1α and RANTES. Neutralization of MIP-1γ with specific Ab reduced RANKL-stimulated osteoclast differentiation by 60–70%. Mature osteoclasts underwent apoptosis within 24 h after removal of RANKL, as shown by increased caspase 3 activity and DNA fragmentation. Apoptosis was reduced by the addition of exogenous MIP-1γ or RANKL, both of which increased NF-κB activation in osteoclasts. Neutralization studies showed that the prosurvival effect of RANKL was in part dependent on its ability to induce MIP-1γ. Finally, osteoclast activation for bone resorption was stimulated by MIP-1γ. Taken together, these results demonstrate that MIP-1γ plays an important role in the differentiation and survival of osteoclasts, most likely via an autocrine pathway.