bluuebunny/crossref_metadata_2025_split huggingface dataset:
B Cell Progenitors Are Arrested in Maturation but Have Intact VDJ Recombination in the Absence of Ig-α and Ig-β
Authors: Pelanda Roberta , Braun Uschi , Hobeika Elias , Nussenzweig Michel C. , Reth Michael 
Published: April 2014

AbstractIg-α and Ig-β mediate surface expression and signaling of diverse B cell receptor complexes on precursor, immature, and mature B cells. Their expression begins before that of the Ig chains in early progenitor B cells. In this study, we describe the generation of Ig-α-deficient mice and their comparative analysis to mice deficient for Ig-β, the membrane-IgM, and recombination-activating gene 2 to determine the requirement of Ig-α and Ig-β in survival and differentiation of pro-B cells. We find that in the absence of Ig-α, B cell development does not progress beyond the progenitor stage, similar to what is observed in humans lacking this molecule. However, neither in Ig-α- nor in Ig-β-deficient mice are pro-B cells impaired in V(D)J recombination, in the expression of intracellular Ig μ-chains, or in surviving in the bone marrow microenvironment. Finally, Ig-α and Ig-β are not redundant in their putative function, as pro-B cells from Ig-α and Ig-β double-deficient mice are similar to those from single-deficient animals in every aspect analyzed.
Characterization of Chromatin Structure and Enhancer Elements for Murine Recombination Activating Gene-2
Authors: Wei Xing-Cheng , Kishi Hiroyuki , Jin Zhe-Xiong , Zhao Wen-Pu , Kondo Sachiko , Matsuda Tadashi , Saito Shigeru , Muraguchi Atsushi 
Published: April 2014

AbstractRecombination-activating genes (RAGs) play a critical role in V(D)J recombination machinery and their expression is specifically regulated during lymphocyte ontogeny. To elucidate the molecular mechanisms regulating murine RAG-2 expression, we examined a chromatin structure of 25-kb DNA segment adjacent to murine RAG-2 by analyzing DNase I hypersensitive (HS) sites. In a RAG-2-expressing murine pre-B cell line, three lymphoid cell-specific HS sites (HS1, HS2, and HS3) were identified. Among these HS sites, one HS site (HS3) that locates in the RAG-2 promoter was associated only with RAG-2-expressing cell lines. Using the transient enhanced green fluorescence protein reporter gene assays, we identified two enhancer elements in the 5′-upstream region of RAG-2 that corresponded to HS1 and HS2. One of the enhancer elements (D3) exhibited enhancer activity only in the lymphoid cell lines. Analysis of the transgenic mice carrying the enhanced green fluorescence protein-reporter gene linked with D3 revealed that D3 activated the reporter gene-expression in the primary lymphoid tissues, but not in the secondary lymphoid tissues or nonlymphoid tissues. D3 was active in CD4−CD8−, but not in CD4+CD8+ or CD4+CD8− thymocytes in the thymus, and also active in B220+IgM−, but not in B220+IgM+, cells in the bone marrow. Finally, our data suggested that C/EBP may bind to the D3 enhancer and function as one of the transcription factor(s) responsible for the enhancer activity. These results show that the tissue- and stage-specific expression of murine RAG-2 is regulated by alteration of the chromatin structure as well as cis-regulatory enhancer elements.
Protein Structure Plays a Critical Role in Peanut Allergen Stability and May Determine Immunodominant IgE-Binding Epitopes
Authors: Sen Moon , Kopper Randall , Pons Laurent , Abraham Edathara C. , Burks A. Wesley , Bannon Gary A. 
Published: April 2014

Abstract
Hypersensitivity to peanuts is a reaction mediated by IgE Abs in response to several peanut protein allergens. Among these allergenic proteins, Ara h 2 is one of the most commonly recognized allergens. Ara h 2 is a 17-kDa protein that has eight cysteine residues that could form up to four disulfide bonds. Circular dichroism studies showed substantial changes in the secondary and tertiary structures of the reduced Ara h 2 as compared with the native protein. Upon treatment with trypsin, chymotrypsin, or pepsin, a number of relatively large fragments are produced that are resistant to further enzymatic digestion. These resistant Ara h 2 peptide fragments contain intact IgE-binding epitopes and several potential enzyme cut sites that are protected from the enzymes by the compact structure of the protein. The enzyme-treated allergen remains essentially intact despite the action of proteases until the fragments are dissociated when the disulfide linkages are reduced. Amino acid sequence analysis of the resistant protein fragments indicates that they contain most of the immunodominant IgE-binding eptiopes. These results provide a link between allergen structure and the immunodominant IgE-binding epitopes within a population of food-allergic individuals.
The Primary Antibody Repertoire Represents a Linked Network of Degenerate Antigen Specificities
Authors: Manivel Venkatasamy , Bayiroglu Fahri , Siddiqui Zaved , Salunke Dinakar M. , Rao Kanury V. S. 
Published: April 2014

Abstract
In this study, germline Abs were used to select clones from a random dodecapeptide phage-display library. This revealed a much greater heterogeneity of binders than could be obtained with mutated daughter Abs that presumably had been selected in vivo by nominal Ag during active immune responses. We demonstrate that the pluripotency of germline Abs can subsequently be optimized by binding interactions that correlate with thermodynamic changes indicative of structural adaptations at the interface. This singular feature confers on each Ab a distinct window of Ag specificities, where the entropic space explored constitutes a thermodynamic signature of that particular Ab. Combining site plasticity may facilitate overlaps in such windows, with independent Abs converging onto common determinants with near identical binding affinities. In addition to providing for an amplified recognition potential, this networking of individual spectra of Ag specificities simultaneously facilitates the rapid recognition of Ag. Importantly, it also ensures that the primary response is composed of Abs with a high degree of “evolvability.”
Antigen Presentation by CD1d Contributes to the Amplification of Th2 Responses to Schistosoma mansoni Glycoconjugates in Mice
Authors: Faveeuw Christelle , Angeli Véronique , Fontaine Josette , Maliszewski Charles , Capron André , Van Kaer Luc , Moser Muriel , Capron Monique , Trottein François 
Published: April 2014

Abstract
During murine schistosomiasis, there is a gradual switch from a predominant Th1 cytokine response to a Th2-dominated response after egg laying, an event that favors the formation of granuloma around viable eggs. Egg-derived glycoconjugates, including glycolipids, may play a crucial role in this phenomenon. In this study, we used a model of dendritic cell sensitization to study the role of egg glycoconjugates in the induction of specific immune response to soluble egg Ag (SEA) and to investigate the possibility that CD1d, a molecule implicated in glycolipid presentation, may be involved in such a phenomenon. We show that, when captured, processed, and presented to naive T lymphocytes by dendritic cells, egg, but not larval, Ag skew the immune response toward a Th2 response. Periodate treatment reversed this effect, indicating that the sugar moiety of SEA is important in this phenomenon. Using DC treated ex vivo with a neutralizing anti-CD1d Ab or isolated from CD1d knockout mice, we show that CD1d is crucial in the priming of SEA-specific Th2 lymphocytes. We then evaluated the contribution of CD1d on the development of the SEA-specific immune response and on the formation of the egg-induced liver granuloma during murine schistosomiasis. We find that CD1d knockout mice have a reduced Th2 response after egg laying and develop a less marked fibrotic pathology compared with wild-type mice. Altogether, our results suggest that Ag presentation of parasite glycoconjugates to CD1d-restricted T cells may be important in the early events leading to the induction of Th2 responses and to egg-induced pathology during murine schistosomiasis.
Production of Granulocyte Colony-Stimulating Factor in the Nonspecific Acute Phase Response Enhances Host Resistance to Bacterial Infection
Authors: Noursadeghi Mahdad , Bickerstaff Maria C. M. , Herbert Jeff , Moyes David , Cohen Jonathan , Pepys Mark B. 
Published: April 2014

Abstract
Mice mounting an acute phase response, induced by sterile inflammation after a single s.c. injection of casein 24 h beforehand, were remarkably protected against lethal infection with Gram-positive or Gram-negative bacteria. This was associated with enhanced early clearance of bacteremia, greater phagocytosis and oxidative burst responses by neutrophils, and enhanced recruitment of neutrophils into tissues compared with control, nonacute phase mice. Casein-induced inflammation was also associated with increased concentrations of G-CSF in serum, and administration of neutralizing Ab to this cytokine completely abrogated protection against Escherichia coli infection after casein pretreatment. Injection of recombinant murine G-CSF between 3 and 24 h before infection conferred the same protection as casein injection. In contrast, the casein-induced acute phase response affected neither serum values of TNF-α, IL-1β, or IL-6 after E. coli infection nor susceptibility to LPS toxicity. Furthermore, protection against infection was unaffected in IL-1R knockout mice, which have deficient acute phase plasma protein responses, or after nonspecific inhibition of acute phase protein synthesis by d-galactosamine or specific depletion of complement C3 by cobra venom factor. Increased production of G-CSF in the acute phase response is thus a key physiological component of host defense, and pretreatment with G-CSF to prevent bacterial infection in at-risk patients now merits further study, especially in view of increasing bacterial resistance to antibiotics.
Human Neutrophil-Expressed CD28 Interacts with Macrophage B7 to Induce Phosphatidylinositol 3-Kinase-Dependent IFN-γ Secretion and Restriction of Leishmania Growth
Authors: Venuprasad K. , Banerjee Pinaki P. , Chattopadhyay Subhasis , Sharma Satyan , Pal Subrata , Parab P. B. , Mitra Debashis , Saha Bhaskar 
Published: April 2014

Abstract
We previously showed that CD28 is expressed on human peripheral blood neutrophils and plays an important role in CXCR-1 expression and IL-8-induced neutrophil migration. In this work we demonstrate that Leishmania major infection of macrophages results in parasite dose-dependent IL-8 secretion in vitro and in IL-8-directed neutrophil migration, as blocked by both anti-IL-8 and anti-IL-8R Abs, toward the L. major-infected macrophages. In the neutrophil-macrophage cocultures, both CTLA4-Ig, a fusion protein that blocks CD28-CD80/CD86 interaction, and a neutralizing anti-IFN-γ Ab inhibit the anti-leishmanial function of neutrophils, suggesting that the neutrophil-macrophage interaction via CD28-CD80/CD86 plays an important role in the IFN-γ-dependent restriction of the parasite growth. Cross-linking of neutrophil-expressed CD28 by monoclonal anti-CD28 Ab or B7.1-Ig or B7.2-Ig results in phosphatidylinositol 3-kinase association with CD28 and in wortmannin-sensitive but cyclosporin A-resistant induction and secretion of IFN-γ. Whereas the neutrophils secrete IFN-γ with CD28 signal alone, the T cells do not secrete the cytokine in detectable amounts with the same signal. Thus, neutrophil-expressed CD28 modulates not only the granulocyte migration but also induction and secretion of IFN-γ at the site of infection where it migrates from the circulation.
Cytokine Regulation of Periportal Fibrosis in Humans Infected with Schistosoma mansoni: IFN-γ Is Associated with Protection Against Fibrosis and TNF-α with Aggravation of Disease
Authors: Henri Sandrine , Chevillard Christophe , Mergani Adil , Paris Patricia , Gaudart Jean , Camilla Christophe , Dessein Hélia , Montero Felix , Elwali Nasr-Eldin M. A. , Saeed Osman K. , Magzoub Mubarak , Dessein Alain J. 
Published: April 2014

Abstract
Hepatic periportal fibrosis, which affects 5–10% of subjects infected by Schistosoma mansoni, is caused by the T cell-dependent granuloma that develop around schistosome eggs. Experimental models of infection have shown that granuloma and fibrosis are tightly regulated by cytokines. However, it is unknown why advanced periportal fibrosis occurs only in certain subjects. The goal of the present study was to evaluate the cytokine response of S. mansoni-infected subjects with advanced liver disease in an attempt to relate susceptibility to periportal fibrosis with an abnormal production of cytokines that regulate granuloma and fibrosis. Fibrosis was evaluated by ultrasound on 795 inhabitants of a Sudanese village in which S. mansoni is endemic: advanced periportal fibrosis was observed in 12% of the population; 35% of the affected subjects exhibited signs of portal hypertension. Age (odds ratio (OR), 11.5), gender (OR, 4.2), and infection levels (OR, 2.2) were significantly (p ≤ 0.01) associated with hepatic fibrosis. Cytokines produced by egg-stimulated blood mononuclear cells from 99 subjects were measured (75 with no or mild fibrosis; 24 subjects with advanced fibrosis). Multivariate analysis of cytokine levels showed that high IFN-γ levels were associated with a marked reduction of the risk of fibrosis (p = 0.01; OR, 0.1); in contrast, high TNF-α levels were associated with an increased risk (p = 0.05; OR, 4.6) of periportal fibrosis. Moreover, infection levels were negatively associated with IFN-γ production. These results with observations in experimental models strongly suggest that IFN-γ plays a key role in the protection of S. mansoni-infected patients against periportal fibrosis, whereas TNF-α may aggravate the disease.
In Vitro Correlates ofLd-Restricted Resistance to Toxoplasmic Encephalitis and Their Critical Dependence on Parasite Strain
Authors: Johnson Jennifer J. , Roberts Craig W. , Pope Constance , Roberts Fiona , Kirisits Michael J. , Estes Randee , Mui Ernest , Krieger Tim , Brown Charles R. , Forman Jim , McLeod Rima 
Published: April 2014

AbstractResistance to murine toxoplasmic encephalitis has been precisely and definitively mapped to the Ld class I gene. Consistent with this, CD8+ T cells can adoptively transfer resistance to toxoplasmic encephalitis. However, cytotoxic CD8+ T cells, capable of killing class I-matched, infected target cells, are generated during the course of Toxoplasma gondii infection even in mice lacking the Ld gene. Ld-restricted killing could not be demonstrated, and the functional correlate of the Ld gene has therefore remained elusive. Herein, Ld-restricted killing of T. gondii-infected target cells is demonstrated for the first time. Ld-restricted killing is critically dependent on the strain of T. gondii and is observed with all the derivatives of type II strains tested, but not with a type I strain. These results have important implications for vaccine development.
Cutting Edge: Myeloid Differentiation Factor 88 Deficiency Improves Resistance Against Sepsis Caused by Polymicrobial Infection
Authors: Weighardt Heike , Kaiser-Moore Simone , Vabulas Ramunas M. , Kirschning Carsten J. , Wagner Hermann , Holzmann Bernhard 
Published: April 2014

AbstractToll-like receptors (TLRs) are important for the activation of innate immune cells upon encounter of microbial pathogens. The present study investigated the potential roles of TLR2, TLR4, and the signaling protein myeloid differentiation factor 88 (MyD88) in polymicrobial septic peritonitis. Whereas both TLR2 and TLR4 were dispensable for host defense against septic peritonitis, MyD88-deficient mice were protected in this infection model. Recruitment of neutrophils to the septic focus and bacterial clearance were normal in MyD88-deficient mice. In contrast, the systemic inflammatory response was strongly attenuated in the absence of MyD88. Surprisingly, MyD88 deficiency did not alter cytokine and chemokine production in spleen, but markedly reduced the inflammatory response in liver and lung. Production of monocyte chemoattractant protein-1 and macrophage-inflammatory protein-1α was entirely independent of MyD88. These results imply a central role of MyD88 for the systemic immune pathology of polymicrobial sepsis and show that cytokine production in spleen and induction of certain chemokines are MyD88 independent.
Th2 Activities Induced During Virgin T Cell Priming in the Absence of IL-4, IL-13, and B Cells
Authors: Cunningham Adam F. , Fallon Padraic G. , Khan Mahmood , Vacheron Sonia , Acha-Orbea Hans , MacLennan Ian C. M. , McKenzie Andrew N. , Toellner Kai-Michael 
Published: April 2014

Abstract
Virgin T cells being primed to Th2-inducing or Th1-inducing Ags, respectively, start to synthesize IL-4 or IFN-γ as they begin to proliferate. Parallel respective induction of B cells to produce γ1 or γ2a switch transcripts provides additional evidence of early divergent Th activity. This report concerns the roles of IL-4, IL-13, and B cells in these early events in vivo. Th2 responses were induced in lymph nodes against hapten-protein given s.c. with killed Bordetella pertussis adjuvant. In T cell proliferation in wild-type mice, IL-4 message up-regulation and γ1 and ε switch transcript production were underway 48–72 h after immunization. The absence of IL-4, IL-13, or B cells did not alter the early T cell proliferative response. The γ1 and ε switch transcript production was still induced in the absence of IL-4, IL-13, or both, but at a reduced level, while the dominance of switching to IgG1 in the extrafollicular hapten-specific plasma cell response was retained. The up-regulation of IL-4 message was not reduced or delayed in the absence of B cells and was only marginally reduced by the absence of IL-13. It is concluded that signals delivered by dendritic cells, which are not dependent on the presence of IL-4, IL-13, or B cells, can prime virgin T cells and induce the early Th2 activities studied. These early events that direct virgin T cells toward Th2 differentiation contrast with the critical later role of Th2 cytokines in selectively expanding Th2 clones and driving further IL-4 synthesis.
Superantigen Enhancement of Specific Immunity: Antibody Production and Signaling Pathways
Authors: Torres Barbara A. , Perrin George Q. , Mujtaba Mustafa G. , Subramaniam Prem S. , Anderson Amy K. , Johnson Howard M. 
Published: April 2014

Abstract
Superantigens are microbial proteins that induce massive activation, proliferation, and cytokine production by CD4+ T cells via specific Vβ elements on the TCR. In this study we examine superantigen enhancement of Ag-specific CD4+ T cell activity for humoral B cell responses to T-dependent Ags BSA and HIV gp120 envelope, type I T-independent Ag LPS, and type II T-independent Ag pneumococcal polysaccharides. Injection of BSA followed by a combination of superantigens staphylococcal enterotoxin A and staphylococcal enterotoxin B (SEB) 7 days later enhanced the anti-BSA Ab response in mice ∼4-fold as compared with mice given BSA alone. The anti-gp120 response was enhanced ∼3-fold by superantigens. The type II T-independent Ag pneumococcal polysaccharide response was enhanced ∼2.3-fold by superantigens, whereas no effect was observed on the response to the type I T-independent Ag LPS. The superantigen effect was completely blocked by the CD4+ T cell inhibitory cytokine IL-10. SEB-stimulated human CD4+ T cells were examined to determine the role of the mitogen-activated protein (MAP) kinase signal transduction pathway in superantigen activation of T cells. Inhibitors of the mitogen pathway of MAP kinase blocked SEB-induced proliferation and IFN-γ production, while an inhibitor of the p38 stress pathway had no effect. Consistent with this, SEB activated extracellular signal-regulated kinase/MAP kinase as well as MAP kinase-interacting kinase, a kinase that phosphorylates eIF4E, which is an important component of the eukaryotic protein synthesis initiation complex. Both kinases were inhibited by IL-10. Thus, superantigens enhance humoral immunity via Ag-specific CD4+ T cells involving the stress-independent pathway of MAP kinase.
Structural Elements of a Protein Antigen Determine Immunogenicity of the Embedded MHC Class I-Restricted T Cell Epitope
Authors: Paster Wolfgang , Kalat Milena , Zehetner Margit , Schweighoffer Tamás 
Published: April 2014

AbstractSubstantial effort has been invested into optimization of vector structure, DNA formulation, or delivery methods to increase the effectiveness of DNA vaccines. In contrast, it has been only insufficiently explored how the higher order structure of an antigenic protein influences immunogenicity of embedded epitopes in vivo. Potent CD8+ T cell responses specific for a single immunogenic epitope are induced upon electrovaccination with plasmid DNA encoding the full-length heavy chain of the human HLA-Cw3 molecule. Contrary to expectations, a minimal construct, which provoked a substantial release of IFN-γ from specific CTLs in vitro, did not induce a significant response in vivo. Systematically altered variants of the Cw3 molecule were thus tested both in vivo and in vitro to determine which structural parts are responsible for this discrepancy. In complementation experiments the participation of trans-acting helper epitopes was ruled out. Successive C-terminal truncations, human/mouse domain swap variants, and subdomain modifications defined the α3 region of the HLA heavy chain and membrane anchoring as critical elements. Based on these data, refined minimal constructs were engineered that triggered very high in vivo responses. The most advanced variant consisted only of an adenoviral leader, antigenic epitope, α3 domain, and 16 aa of the transmembrane domain. When a tumor Ag epitope was incorporated into one of these high performer minimal constructs, protection against melanoma metastases was attained upon vaccination. Thus, structural elements of the Ag can dominantly influence immunogenicity in vivo. These elements can also markedly improve the immunogenicity of unrelated Ags and may form the basis of a new generation of DNA vaccines.
Recruitment of CTL Activity by Tumor-Specific Antibody-Mediated Targeting of Single-Chain Class I MHC-Peptide Complexes
Authors: Lev Avital , Novak Hila , Segal Dina , Reiter Yoram 
Published: April 2014

AbstractThe MHC class I-restricted CD8 CTL effector arm of the adaptive immune response is uniquely equipped to recognize tumor cells as foreign and consequently initiates the cascade of events resulting in their destruction. However, tumors have developed sophisticated strategies to escape immune effector mechanisms; their most well-known strategy is down-regulation of MHC class I molecules. To overcome this and develop new approaches for immunotherapy, we have constructed a recombinant molecule in which a single-chain MHC is specifically targeted to tumor cells through its fusion to cancer-specific recombinant Ab fragments. As a model we used a single-chain HLA-A2 molecule genetically fused to the variable domains of an anti-IL-2Rα subunit-specific humanized Ab, anti-Tac. The construct, termed B2M-aTac(dsFv), was expressed in Escherichia coli, and functional molecules were produced by in vitro refolding in the presence of HLA-A2-restricted antigenic peptides. Flow cytometry studies revealed the ability to decorate Ag-positive, HLA-A2-negative human tumor cells with HLA-A2-peptide complexes in a manner that was entirely dependent upon the specificity of the targeting Ab fragment. Most importantly, the B2M-aTac(dsFv)-mediated coating of the target tumor cells made them susceptible for efficient and specific HLA-A2-restricted, melanoma gp100 peptide-specific CTL-mediated lysis. These results demonstrate the concept that Ab-guided, Ag-specific targeting of MHC-peptide complexes on tumor cells can render them susceptible and more receptive and thus potentiate CTL killing. This type of approach may open the way for the development of new immunotherapeutic strategies based on Ab targeting of natural cognate MHC ligands and CTL-based cytotoxic mechanisms.