bluuebunny/crossref_metadata_2025_split huggingface dataset:
ATM Is Not Required in Somatic Hypermutation of VH, but Is Involved in the Introduction of Mutations in the Switch μ Region
Authors: Pan-Hammarström Qiang , Dai Shujing , Zhao Yaofeng , van Dijk-Härd Iris F. , Gatti Richard A. , Børresen-Dale Anne-Lise , Hammarström Lennart 
Published: April 2014

AbstractClass switch recombination (CSR) and somatic hypermutation (SHM) are mechanistically related processes that share common key factors such as activation-induced cytidine deaminase. We have previously shown a role for ATM (mutated in ataxia-telangiectasia) in CSR. In this paper we show that the frequency, distribution, and nature of base pair substitutions in the Ig variable (V) heavy chain genes in ataxia-telangiectasia patients are largely similar to those in normal donors, suggesting a normal SHM process. Characterization of the third complementarity-determining region in B cells from ataxia-telangiectasia patients also shows a normal V(D)J recombination process. SHM-like mutations could be identified in the switch (S) μ region (up to several hundred base pairs upstream of the Sμ-Sα breakpoints) in normal in vivo switched human B cells. In the absence of ATM, mutations can still be found in this region, but at less than half the frequency of that in normal donors. The latter mutations are mainly due to transitions (86% compared with 58% in controls) and are biased to A or T nucleotides. An ATM-dependent mechanism, different from that generating SHM in V genes, is therefore likely to be involved in introducing SHM-like mutations in the S region. ATM may thus be one of the factors that is not shared by the CSR and SHM processes.
Transactivation of gp130 in Myeloma Cells
Authors: French Jena D. , Walters Denise K. , Jelinek Diane F. 
Published: April 2014

Abstract
Receptor transactivation, i.e., interaction between unrelated receptor systems, is a growing theme in cytokine and growth factor signaling. In this study we reveal for the first time the ability of IFN-α to transactivate gp130 in myeloma cells. An epidermal growth factor receptor/gp130 chimeric receptor previously shown by us to transactivate endogenous gp130, provided a complementary tool to study the underlying mechanisms of receptor cross-talk. Further analysis revealed that transactivation of gp130 by IFN-α did not require the extracellular or trans-membrane domain of gp130. Moreover, transactivation of gp130 was critically dependent upon Janus kinase activation by the initiating receptor and correlated with rapid and sustained Janus kinase 1 and tyrosine kinase (Tyk) 2 tyrosine phosphorylation. Finally, transactivation of gp130 may be a common theme in myeloma cells, perhaps providing a mechanism for enhanced or qualitatively distinct cellular responses to specific stimuli.
c-Rel Is Required for Chromatin Remodeling Across the IL-2 Gene Promoter
Authors: Rao Sudha , Gerondakis Steve , Woltring Donna , Shannon M. Frances 
Published: April 2014

Abstract
IL-2 gene transcription occurs in an activation-dependent manner in T cells responding to TCR and CD28 activation. One of the critical events leading to increased IL-2 transcription is an alteration in chromatin structure across the 300-bp promoter region of the gene. We initially showed that IL-2 gene transcription in CD4+ primary T cells is dependent on the NF-κB family member, c-Rel, but not RelA. We found that c-Rel is essential for global changes in chromatin structure across the 300-bp IL-2 promoter in response to CD3/CD28 in primary CD4+ T cells, but not in response to pharmacological signals, paralleling the requirement for c-Rel in IL-2 mRNA and protein accumulation. Interestingly, measurement of activation-induced localized accessibility changes using restriction enzyme digestion revealed that accessibility close to the c-Rel binding site in the CD28RR region of the promoter is specifically dependent on c-Rel. In contrast, restriction enzyme sites located at a distance from the CD28RR behave independently of c-Rel. These results suggest a nonredundant role for c-Rel in generating a correctly remodeled chromatin state across the IL-2 promoter and imply that the strength of the signal determines the requirement for c-Rel.
Regulation of the Human FcεRI α-Chain Distal Promoter
Authors: Hasegawa Masanari , Nishiyama Chiharu , Nishiyama Makoto , Akizawa Yushiro , Takahashi Kyoko , Ito Tomonobu , Furukawa Susumu , Ra Chisei , Okumura Ko , Ogawa Hideoki 
Published: April 2014

Abstract
The α-chain of the high affinity receptor for IgE (FcεRI) is essential for cell surface expression of FcεRI and binding of the IgE Ab. The human α-chain gene possesses two promoters: the proximal promoter, which is highly conserved with that of rodent; and the distal promoter, the structure and role of which are largely unknown. Transcriptional regulation of the α-chain distal promoter was investigated in this study. Transient reporter assay revealed critical region for transcription activity located within −27/−17. EMSA identified Elf-1, YY1, and PU.1 as transcription factors binding to this region. In contrast to the proximal promoter, which was trans-activated by YY1 and PU.1, these transcription factors exhibited repressive function on this promoter. Addition of IL-4 caused a marked increase in transcription from the distal promoter and subsequently increased the intracellular production of the α-chain. These results indicate that IL-4-dependent up-regulation of the human α-chain was due to enhancement of distal promoter activity and suggests that the two promoters have different regulatory mechanisms for α-chain expression.
A New Model of Sheep Ig Diversification: Shifting the Emphasis Toward Combinatorial Mechanisms and Away from Hypermutation
Authors: Jenne Craig N. , Kennedy Laurie J. , McCullagh Peter , Reynolds John D. 
Published: April 2014

AbstractThe current model of Ig repertoire development in sheep focuses on the rearrangement of a small number (∼20) of Vλ gene segments. It is believed that this limited combinatorial repertoire is then further diversified through postrearrangement somatic hypermutation. This process has been reported to introduce as many as 110 mutations/1000 nucleotides. In contrast, our data have that indicated somatic hypermutation may diversify the preimmune repertoire to a much lesser extent. We have identified 64 new Vλ gene segments within the rearranged Ig repertoire. As a result, many of the unique nucleotide patterns thought to be the product of somatic hypermutation are actually hard-coded within the germline. We suggest that combinatorial rearrangement makes a much larger contribution, and somatic hypermutation makes a much smaller contribution to the generation of diversity within the sheep Ig repertoire than is currently acknowledged.
DM Loss in k Haplotype Mice Reveals Isotype-Specific Chaperone Requirements
Authors: Koonce Chad H. , Wutz Gordana , Robertson Elizabeth J. , Vogt Anne B. , Kropshofer Harald , Bikoff Elizabeth K. 
Published: April 2014

Abstract
DM actions as a class II chaperone promote capture of diverse peptides inside the endocytic compartment(s). DM mutant cells studied to date express class II bound by class II-associated invariant chain-derived peptide (CLIP), a short proteolytic fragment of the invariant chain, and exhibit defective peptide-loading abilities. To evaluate DM functional contributions in k haplotype mice, we engineered a novel mutation at the DMa locus via embryonic stem cell technology. The present experiments demonstrate short-lived Ak/CLIP complexes, decreased Ak surface expression, and enhanced Ak peptide binding activities. Thus, we conclude that DM loss in k haplotype mice creates a substantial pool of empty or loosely occupied Ak conformers. On the other hand, the mutation hardly affects Ek activities. The appearance of mature compact Ek dimers, near normal surface expression, and efficient Ag presentation capabilities strengthen the evidence for isotype-specific DM requirements. In contrast to DM mutants described previously, partial occupancy by wild-type ligands is sufficient to eliminate antiself reactivity. Mass spectrometry profiles reveal Ak/CLIP and a heterogeneous collection of relatively short peptides bound to Ek molecules. These experiments demonstrate that DM has distinct roles depending on its specific class II partners.
Actin Tyrosine Dephosphorylation by the Src Homology 1-Containing Protein Tyrosine Phosphatase Is Essential for Actin Depolymerization After Membrane IgM Cross-Linking
Authors: Baba Takeshi , Fusaki Noemi , Shinya Nobuko , Iwamatsu Akihiro , Hozumi Nobumichi 
Published: April 2014

Abstract
Src homology protein 1 (SHP-1) plays an important role in B cell Ag receptor (BCR) differentiation, proliferation, survival, and apoptosis. After BCR stimulation in apoptotic cells, SHP-1 has been shown to be recruited to phosphorylated immunoreceptor tyrosine-based inhibitory motifs present in receptors such as CD22 and CD72. However, the substrates of SHP-1 in the chicken B cell line, DT40, have remained undefined. To identify SHP-1 substrates in DT40, we used a trapping mutant, SHP-1 C/S (a catalytically inactive form). Cross-linking of BCR induced hyperphosphorylation of ∼44-kDa protein in C/S transfectants. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis revealed that this was actin (cytoplasmic type 5) carrying three immunoreceptor tyrosine-based inhibitory motif-like sequences. SHP-1 was shown to bind to one of these sequences in synthetic peptide binding experiment. Thus, actin is a direct SHP-1 substrate. Furthermore, more SHP-1 molecules translocate into lipid rafts, and their association with actin was increased after BCR stimulation. In C/S transfectants, actin polymerization induced by membrane IgM ligation was sustained to a greater extent for a longer time compared with wild-type transfectants. Therefore, actin dephosphorylation by SHP-1 is essential for actin depolymerization after BCR stimulation. Our data suggest that SHP-1 plays a pivotal role in reorganization of cytoskeletal architecture inducing actin dephosphorylation. These results clearly demonstrate the direct interaction of SHP-1 with actin.
Investigation of Early Events in FcεRI-Mediated Signaling Using a Detailed Mathematical Model
Authors: Faeder James R. , Hlavacek William S. , Reischl Ilona , Blinov Michael L. , Metzger Henry , Redondo Antonio , Wofsy Carla , Goldstein Byron 
Published: April 2014

Abstract
Aggregation of FcεRI on mast cells and basophils leads to autophosphorylation and increased activity of the cytosolic protein tyrosine kinase Syk. We investigated the roles of the Src kinase Lyn, the immunoreceptor tyrosine-based activation motifs (ITAMs) on the β and γ subunits of FcεRI, and Syk itself in the activation of Syk. Our approach was to build a detailed mathematical model of reactions involving FcεRI, Lyn, Syk, and a bivalent ligand that aggregates FcεRI. We applied the model to experiments in which covalently cross-linked IgE dimers stimulate rat basophilic leukemia cells. The model makes it possible to test the consistency of mechanistic assumptions with data that alone provide limited mechanistic insight. For example, the model helps sort out mechanisms that jointly control dephosphorylation of receptor subunits. In addition, interpreted in the context of the model, experimentally observed differences between the β- and γ-chains with respect to levels of phosphorylation and rates of dephosphorylation indicate that most cellular Syk, but only a small fraction of Lyn, is available to interact with receptors. We also show that although the β ITAM acts to amplify signaling in experimental systems where its role has been investigated, there are conditions under which the β ITAM will act as an inhibitor.
Depletion of Neutrophils in IL-10−/− Mice Delays Clearance of Gastric Helicobacter Infection and Decreases the Th1 Immune Response to Helicobacter
Authors: Ismail Hanan F. , Fick Pamela , Zhang Juan , Lynch Richard G. , Berg Daniel J. 
Published: April 2014

Abstract
Gastric infection with Helicobacter induces a lymphocyte-rich mucosal inflammation that contains a minor population of neutrophilic granulocytes. The function of neutrophils in the local immune response to gastric Helicobacter infection remains unknown. To investigate this issue, we conducted experiments in neutrophil-depleted control wild-type (wt) and IL-10−/− mice infected with Helicobacter felis by gastric lavage. Infection of wt mice elicited a mild, focal gastritis and a Helicobacter-specific Th1 immune response. In wt mice Helicobacter colonization of the stomach was persistent and progressively increased during the 29 days of observation. Infection of IL-10−/− mice with H. felis elicited a severe chronic gastritis and a greatly enhanced Helicobacter-specific Th1 immune response, as compared with wt mice. After initial colonization, the IL-0−/− mice completely cleared Helicobacter from the stomach by day 8. The gastric inflammation in wt and IL-10−/− mice contained modest numbers of neutrophils. The intensity of gastric inflammation and the extent of Helicobacter colonization were similar in control and in neutrophil-depleted wt mice. In contrast, neutrophil depletion of Helicobacter-infected IL-10−/− mice decreased the severity of gastritis, modulated the Helicobacter-specific Th1 immune response, and delayed the clearance of bacteria from the stomach. These studies identify a role for neutrophils in the local and systemic immune response to gastric Helicobacter in IL-10−/− mice.
The Hypervariable Region of Anaplasma marginale Major Surface Protein 2 (MSP2) Contains Multiple Immunodominant CD4+ T Lymphocyte Epitopes That Elicit Variant-Specific Proliferative and IFN-γ Responses in MSP2 Vaccinates
Authors: Brown Wendy C. , Brayton Kelly A. , Styer Cathryn M. , Palmer Guy H. 
Published: April 2014

Abstract
Major surface protein 2 (MSP2) is an immunodominant outer membrane protein of Anaplasma marginale and Anaplasma phagocytophilum pathogens that cause bovine anaplasmosis and human granulocytic ehrlichiosis, respectively. MSP2 has a central hypervariable region (HVR) flanked by highly conserved amino and carboxyl termini. During A. marginale infection, dynamic and extensive amino acid sequence variation in MSP2 occurs through recombination of msp2 pseudogenes into the msp2 expression site, followed by sequential segmental gene conversions to generate additional variants. We hypothesized that MSP2 variation leads to significant changes in Th cell recognition of epitopes in the HVR. T cell epitopes were mapped using T cells from native MSP2-immunized cattle and overlapping peptides spanning the most abundant of five different MSP2 HVRs in the immunogen. Several epitopes elicited potent effector/memory Th cell proliferative and IFN-γ responses, including those in three discreet blocks of sequence that undergo segmental gene conversion. Th cell clones specific for an epitope in the block 1 region of the predominant MSP2 variant type failed to respond to naturally occurring variants. However, some of these variants were recognized by oligoclonal T cell lines from MSP2 vaccinates, indicating that the variant sequences contain immunogenic CD4+ T cell epitopes. In competition/antagonism assays, the nonstimulatory variants were not inhibitory for CD4+ T cells specific for the agonist peptide. Dynamic amino acid sequence variation in MSP2 results in escape from recognition by some effector/memory MSP2-specific Th cells. Antigenic variation in MSP2 Th cell and B cell epitopes may contribute to immune evasion that allows long-term persistence of A. marginale in the mammalian reservoir.
A Common Mucosal Chemokine (Mucosae-Associated Epithelial Chemokine/CCL28) Selectively Attracts IgA Plasmablasts
Authors: Lazarus Nicole H. , Kunkel Eric J. , Johnston Brent , Wilson Eric , Youngman Kenneth R. , Butcher Eugene C. 
Published: April 2014

AbstractIgA immunoblasts can seed both intestinal and nonintestinal mucosal sites following localized mucosal immunization, an observation that has led to the concept of a common mucosal immune system. In this study, we demonstrate that the mucosae-associated epithelial chemokine, MEC (CCL28), which is expressed by epithelia in diverse mucosal tissues, is selectively chemotactic for IgA Ab-secreting cells (ASC): MEC attracts IgA- but not IgG- or IgM-producing ASC from both intestinal and nonintestinal lymphoid and effector tissues, including the intestines, lungs, and lymph nodes draining the bronchopulmonary tree and oral cavity. In contrast, the small intestinal chemokine, TECK (CCL25), attracts an overlapping subpopulation of IgA ASC concentrated in the small intestines and its draining lymphoid tissues. Surprisingly, T cells from mucosal sites fail to respond to MEC. These findings suggest a broad and unifying role for MEC in the physiology of the mucosal IgA immune system.
Tumor-Derived TGF-β Reduces the Efficacy of Dendritic Cell/Tumor Fusion Vaccine
Authors: Kao John Y. , Gong Yusong , Chen Chuan-Min , Zheng Qiong-Duan , Chen Jian-Jun 
Published: April 2014

Abstract
Dendritic cell (DC)-based antitumor vaccine is a novel cancer immunotherapy that is promising for reducing cancer-related mortality. However, results from early clinical trials were suboptimal. A possible explanation is that many tumors secrete immunosuppressive factors such as TGF-β, which may hamper host immune response to DC vaccine. In this study, we demonstrated that TGF-β produced by tumors significantly reduced the potency of DC/tumor fusion vaccines. TGF-β-secreting (CT26-TGF-β) stable mouse colon cancer cell lines were generated using a retroviral vector expressing TGF-β. A non-TGF-β-secreting (CT26-neo) cell line was generated using an empty retroviral vector. The efficacies of DC/tumor fusion vaccines were assessed in vitro and in vivo. DC/CT26-TGF-β fusion cells failed to induce a strong T cell proliferative response in vitro, mainly due to the effect of TGF-β on T cell responsiveness rather than DC stimulatory capability. Animals vaccinated with DC/CT26-TGF-β fusion vaccine had lower tumor-specific CTL activity and had significantly lower survival after tumor challenge as compared with animals immunized with DC/CT26-neo hybrids (45 vs 77%, p &lt; 0.05). Ex vivo exposure of DCs to TGF-β did not appear to lessen the efficacy of DC vaccine. These data suggest that tumor-derived TGF-β reduces the efficacy of DC/tumor fusion vaccine via an in vivo mechanism. Neutralization of TGF-β produced by the fusion cells may enhance the effectiveness of DC-based immunotherapy.
A Role for Triggering Receptor Expressed on Myeloid Cells-1 in Host Defense During the Early-Induced and Adaptive Phases of the Immune Response
Authors: Bleharski Joshua R. , Kiessler Viviane , Buonsanti Cecilia , Sieling Peter A. , Stenger Steffen , Colonna Marco , Modlin Robert L. 
Published: April 2014

Abstract
Triggering receptor expressed on myeloid cells (TREM)-1 is a cell surface molecule expressed on neutrophils and monocytes implicated in the propagation of the inflammatory response. To further characterize the function of this molecule in different phases of the immune response, we examined TREM-1 in the context of host defense against microbial pathogens. In primary human monocytes TREM-1 activation did not trigger innate antimicrobial pathways directed against intracellular Mycobacterium tuberculosis, and only minimally improved phagocytosis. However, activation of TREM-1 on monocytes did drive robust production of proinflammatory chemokines such as macrophage inflammatory protein-1α and IL-8. Engagement of TREM-1 in combination with microbial ligands that activate Toll-like receptors also synergistically increased production of the proinflammatory cytokines TNF-α and GM-CSF, while inhibiting production of IL-10, an anti-inflammatory cytokine. Expression of TREM-1 was up-regulated in response to TLR activation, an effect further enhanced by GM-CSF and TNF-α but inhibited by IL-10. Functionally, primary monocytes differentiated into immature dendritic cells following activation through TREM-1, evidenced by higher expression of CD1a, CD86, and MHC class II molecules. These cells had an improved ability to elicit T cell proliferation and production of IFN-γ. Our data suggest that activation of TREM-1 on monocytes participates during the early-induced and adaptive immune responses involved in host defense against microbial challenges.
The Resolution of Relapsing Fever Borreliosis Requires IgM and Is Concurrent with Expansion of B1b Lymphocytes
Authors: Alugupalli Kishore R. , Gerstein Rachel M. , Chen Jianzhu , Szomolanyi-Tsuda Eva , Woodland Robert T. , Leong John M. 
Published: April 2014

Abstract
The rate of pathogen clearance is a critical determinant of morbidity and mortality. We sought to characterize the immune response responsible for the remarkably rapid clearance of individual episodes of bacteremia caused by the relapsing fever bacterium, Borrelia hermsii. SCID or Rag−/− mice were incapable of resolving B. hermsii infection, indicating a critical role for T and/or B cells. TCR−/− mice, which lack T cells, and IL-7−/− mice, which are deficient in both T cells and follicular B cells, but not in B1 cells and splenic marginal zone (MZ) B cells, efficiently cleared B. hermsii. These findings suggested that B1 cells and/or MZ B cells, two B cell subsets that are known to participate in rapid, T-independent responses, might be involved. The efficient resolution of the episodes of moderate level bacteremia by splenectomized mice suggested that MZ B cells do not play the primary role in clearance of this bacterium. In contrast, xid mice, which are deficient in B1 cells, suffered more severe episodes of bacteremia than wild-type mice. The hypothesis that B1 cells are critical for clearance of B. hermsii was further supported by a selective expansion of the B1b (i.e., IgMhigh, IgD−/low, Mac1+ CD23−, and CD5−) cell subset in infected xid mice, which coincided with the eventual resolution of infection. Finally, mice selectively incapable of secreting IgM, the dominant isotype produced by B1 cells, were completely unable to clear B. hermsii. Together these results support the model that B1b cells generate the T-independent IgM required for the control and resolution of relapsing fever borreliosis.
Differential γ-Herpesvirus Distribution in Distinct Anatomical Locations and Cell Subsets During Persistent Infection in Mice
Authors: Flaño Emilio , Kim In-Jeong , Moore John , Woodland David L. , Blackman Marcia A. 
Published: April 2014

Abstract
Murine γ-herpesvirus 68 (MHV-68) provides an important experimental model for analyzing γ-herpesvirus latent infection. After intranasal infection with MHV-68, we analyzed the distribution of the virus in different anatomical locations and purified populations of cells. Our data show that long-term latency is maintained in a variety of anatomical locations and cell populations with different frequencies. Importantly, we demonstrate that although latency in the lung is established in a variety of cell subsets, long-term latency in the lung is only maintained in B cells. In contrast, splenic latency is maintained in macrophages and dendritic cells, as well as in B cells. In blood, isotype-switched B cells constitute the major viral reservoir. These results show that the cell subsets in which latency is established vary within different anatomical sites. Finally, we demonstrate that long-term latency is accompanied by a low level of infectious virus in lung and spleen. These data have important implications for understanding the establishment and maintenance of latency by γ2-herpesviruses.