bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonproliferating Bystander CD4+ T Cells Lacking Activation Markers Support HIV Replication During Immune Activation
Authors: Scales David , Ni Houping , Shaheen Farida , Capodici John , Cannon Georgetta , Weissman Drew 
Published: April 2014

AbstractHIV replicates primarily in lymphoid tissue and immune activation is a major stimulus in vivo. To determine the cells responsible for HIV replication during Ag-driven T cell activation, we used a novel in vitro model employing dendritic cell presentation of superantigen to CD4+ T cells. Dendritic cells and CD4+ T cells are the major constituents of the paracortical region of lymphoid organs, the main site of Ag-specific activation and HIV replication. Unexpectedly, replication occurred in nonproliferating bystander CD4+ T cells that lacked activation markers. In contrast, activated Ag-specific cells were relatively protected from infection, which was associated with CCR5 and CXC chemokine receptor 4 down-regulation. The finding that HIV replication is not restricted to highly activated Ag-specific CD4+ T cells has implications for therapy, efforts to eradicate viral reservoirs, immune control of HIV, and Ag-specific immune defects.
Unique Subpopulations of CD56+ NK and NK-T Peripheral Blood Lymphocytes Identified by Chemokine Receptor Expression Repertoire
Authors: Campbell James J. , Qin Shixin , Unutmaz Derya , Soler Dulce , Murphy Kristine E. , Hodge Martin R. , Wu Lijun , Butcher Eugene C. 
Published: April 2014

Abstract
CD56, an adhesion molecule closely related to neual cell adhesion molecule, is an immunophenotypic marker for several unique populations of PBLs. Although CD56+ cells derive from multiple lymphocyte lineages, they share a role in immunosurveillance and antitumor responses. We have studied the chemokine receptor expression patterns and functional migratory responses of three distinct CD56+ populations from human peripheral blood. NK-T cells were found to differ greatly from NK cells, and CD16+ NK cells from CD16− NK cells. CD16+ NK cells were the predominant population responding to IL-8 and fractalkine, whereas NK-T cells were the predominant population responding to the CCR5 ligand macrophage-inflammatory protein-1β. CD16− NK cells were the only CD56+ population that uniformly expressed trafficking molecules necessary for homing into secondary lymphoid organs through high endothelial venule. These findings describe a diverse population of cells that may have trafficking patterns entirely different from each other, and from other lymphocyte types.
The Role of Adoptively Transferred CD8 T Cells and Host Cells in the Control of the Growth of the EG7 Thymoma: Factors That Determine the Relative Effectiveness and Homing Properties of Tc1 and Tc2 Effectors
Authors: Helmich Brian K. , Dutton Richard W. 
Published: April 2014

AbstractWe had previously examined the factors that regulate the response of OVA-specific TCR-transgenic CD8 T cells to the B16 OVA melanoma, growing as lung metastases. We examine here whether the same parameters operate for EG7, growing intradermally. Tc1 or Tc2 CD8 effector cells from OT-1 mice were injected either mixed with the tumor or i.v. at day 0 or 7. Tc2 were one-fifth to one-tenth as effective as Tc1 when injected with the tumor, in controlling tumor growth, but were only 1/20 to 1/100 injected i.v. Tc1 injected i.v. entered the draining lymph nodes faster than Tc2 and caused a faster accumulation of host cells. Both caused an abrupt termination of host cell entry into lymph nodes and spleen after tumor elimination, but this occurred earlier for Tc1 than for Tc2. Host responses were ineffective in the absence of adoptive transfer but were essential after transfer. Perforin expression in the donor cells plays no role in adoptively transferred Tc1 or Tc2 control of the tumor, and neither IL-4 nor IL5 is needed for Tc1 or Tc2 function. Tc1 cells from mice lacking IFN-γ, however, control tumor growth less well, whereas Tc2 effectors lacking IFN-γ are unaffected. Tc1 from IFN-γ-deficient mice attract fewer host cells to the draining lymph node, whereas Tc1 cells from perforin-deficient donors are unimpaired. We conclude that host cell recruitment is a crucial element in adoptive immunotherapy. The differences between the EG7 and the previous B16 melanoma model are discussed.
A Transcriptional Block in the IL-2 Promoter at the −150 AP-1 Site in Effector CD8+ T Cells
Authors: Finch Rosalynde J. , Fields Patrick E. , Greenberg Philip D. 
Published: April 2014

AbstractBoth CD4+ and CD8+ T cells that produce IL-2 in response to Ag recognition have been isolated. However, most effector CD8+ T cells recovered after exposure to Ag do not produce sufficient IL-2 to sustain growth, and depend on CD4+ T helper cells for this obligate growth factor. IL-2 expression in CD4+ T cells is primarily controlled at the level of transcription, but mechanisms restricting IL-2 production in CD8+ T cells have not been elucidated. To evaluate transcriptional regulation of the IL-2 gene in CD8+ T cells, we stably transfected reporter genes into Ag-specific CD8+ T cell clones. CD28+ CD8+ T cells unable to transcribe the IL-2 gene in response to antigenic stimulation had a block in transactivation of the −150 CD28 response element (CD28RE)/AP-1 site of the IL-2 promoter, but did transactivate the composite NFAT/AP-1 and OCT/AP-1 sites, and a consensus AP-1 motif. Mutation of the nonconsensus −150 AP-1 site to a consensus AP-1 site, or insertion of a CD28RE/AP-1 consensus site upstream of the native −150 CD28RE/AP-1 site restored transactivation of the altered promoter. These results suggest that the defect at the −150 site may reflect the absence or inactivity of a required factor rather than repression of the IL-2 promoter.
Molecular Identification of IgE-Dependent Histamine-Releasing Factor as a B Cell Growth Factor
Authors: Kang Hyung Sik , Lee Min Ju , Song Hyunkeun , Han Seung Hyun , Kim Yong Man , Im Joo Young , Choi Inpyo 
Published: April 2014

AbstractThe culture supernatants of LK1 cells, murine erythroleukemia cells, showed B cell-stimulating activity. Purification and NH2-terminal sequence analysis revealed that one of the candidates was murine IgE-dependent histamine-releasing factor (IgE-HRF), which is known to induce histamine from basophils. Recombinant IgE-HRF (rHRF) obtained from Escherichia coli- or 293-transformed embryonal kidney cells was tested for B cell-stimulating activity. Both rHRFs stimulated B cell proliferation in a dose-dependent manner. However, boiling or anti-HRF Ab abolished the B cell stimulatory effects of rHRF. Recombinant HRF showed strong synergistic effects with IL-2, IL-4, and IL-5 for B cell activation, with maximal activity in the presence of anti-CD40 Ab. Recombinant HRF increased MHC class II expression of B cells. It also increased Ig production from B cells. Treatment with polymyxin B, a neutralizing peptide antibiotic of LPS, did not reduce the activity of rHRF. In addition, FACS analysis using PE-conjugated rHRF showed that HRF bound to B cells. Recombinant HRF up-regulated the expression of IL-1 and IL-6 in B cells. In vivo administration of rHRF or the cDNA for rHRF increased total and Ag-specific Ig synthesis. Taken together, these results indicate that HRF stimulates B cell activation and function.
Inhibition of p38 Kinase Reveals a TNF-α-Mediated, Caspase-Dependent, Apoptotic Death Pathway in a Human Myelomonocyte Cell Line
Authors: Varghese Jishy , Chattopadhaya Souvik , Sarin Apurva 
Published: April 2014

AbstractTNF-α transduces signals of survival or death via its two receptors, R1/p55/p60 and RII/p80/p75. The role of caspases as effectors of cell death is universally accepted, although caspase inhibitors may potentiate TNF cytotoxicity in some instances. In conditions when macromolecular synthesis is blocked, caspases are part of the machinery that executes TNF-triggered apoptotic death in U937, a human myelomonocyte cell line, and in the Jurkat T cell line. However, inhibition of p38 mitogen-activated protein kinase (p38 MAPK) triggered TNF cytotoxicity in U937 cells and murine splenic macrophages, but not the Jurkat cell line. TNF induced expression of the antiapoptotic protein c-IAP2 (cytoplasmic inhibitor of apoptosis protein 2), and was blocked in the presence of a p38 MAPK inhibitor, which also induced caspase-dependent, TNF-mediated apoptosis in U937 cells. Thus, inhibition of p38 MAPK resulted in the activation of caspase 9 and cleavage of the adaptor molecule BH3 interacting domain death agonist, and blocked NF-κB-mediated transactivation, without affecting the nuclear translocation of NF-κB. Collectively, these data show that activation of p38 MAPK is critical to cell survival by TNF in U937 cells, and demonstrate lineage-specific regulation of TNF-triggered signals of activation or apoptosis.
Early TCR αβ Expression Promotes Maturation of T Cells Expressing FcεRIγ Containing TCR/CD3 Complexes
Authors: Petersson Karin , Ivars Fredrik 
Published: April 2014

AbstractIn a previous study we presented data indicating that the expanded population of CD4−CD8− (DN) αβ T cells in TCRα-chain-transgenic mice was partially if not entirely derived from γδ T cell lineage cells. The development of both γδ T cells and DN αβ T cells is poorly understood; therefore, we thought it would be important to identify the immediate precursors of the transgene-induced DN αβ T cells. We have in this report studied the early T cell development in these mice and we show that the transgenic TCRα-chain is expressed by precursor thymocytes already at the CD3−CD4−CD8− (triple negative, TN) CD44+CD25− stage of development. Both by using purified precursor populations in reconstitution experiments and by analyzing fetal thymocyte development, we demonstrated that early TN precursors expressing endogenous TCRβ-chains matured into DN αβ T cells at several stages of development. The genes encoding the γ-chain of the high affinity receptor for IgE (FcεRIγ) and the CD3ζ protein were found to be reciprocally expressed in TN thymocytes such that during development the FcεRIγ expression decreased whereas CD3ζ expression increased. Furthermore, in a fraction of the transgene-induced DN αβ T cells the FcεRIγ protein colocalized with the TCR/CD3 complex. These data suggest that similarly to γδ T cells and NKT cells, precursors expressing the TCR early in the common αβγδ developmental pathway may use the FcεRIγ protein as a signaling component of the TCR/CD3 complex.
Rigidity of Circulating Lymphocytes Is Primarily Conferred by Vimentin Intermediate Filaments
Authors: Brown Martin J. , Hallam John A. , Colucci-Guyon Emma , Shaw Stephen 
Published: April 2014

Abstract
Lymphocytes need rigidity while in circulation, but must abruptly become deformable to undergo transmigration into tissue. Previously, the control of leukocyte deformability has been attributed to microfilaments or microtubules, but the present studies demonstrate the greater importance of vimentin intermediate filaments (IFs). In circulating T lymphocytes, IFs form a distinctive spherical cage that undergoes a rapid condensation into a juxtanuclear aggregate during chemokine-induced polarization. Measurements of the resistance of peripheral blood T lymphocytes to global deformation demonstrate that their rigidity is primarily dependent on intact vimentin filaments. Microtubules, in contrast, are not sufficient to maintain rigidity. Thus, vimentin IFs are a primary source of structural support in circulating human lymphocytes, and their regulated collapse is likely to be an essential element in chemokine-induced transendothelial migration.
Induction of Telomerase Activity During Development of Human Mast Cells from Peripheral Blood CD34+ Cells: Comparisons with Tumor Mast-Cell Lines
Authors: Chaves-Dias Cristina , Hundley Thomas R. , Gilfillan Alasdair M. , Kirshenbaum Arnold S. , Cunha-Melo Jose Renan , Metcalfe Dean D. , Beaven Michael A. 
Published: April 2014

AbstractTo further characterize the development of mast cells from human hemopoietic pluripotent cells we have investigated the expression of telomerase activity in cultured human peripheral blood CD34+ cells, and CD34+/CD117+/CD13+ progenitor mast cells selected therefrom, with the idea that induction of telomerase is associated with clonal expansion of CD34+/CD117+/CD13+ cells. A rapid increase in telomerase activity preceded proliferation of both populations of cells in the presence of stem cell factor and either IL-3 or IL-6. The induction was transient, and telomerase activity declined to basal levels well before the appearance of mature mast cells. Studies with pharmacologic inhibitors suggested that this induction was initially dependent on the p38 mitogen-activated protein kinase and phosphatidylinositol 3′-kinase, but once cell replication was underway telomerase activity, but not cell replication, became resistant to the effects of inhibitors. Tumor mast cell lines, in contrast, expressed persistently high telomerase activity throughout the cell cycle, and this expression was unaffected by inhibitors of all known signaling pathways in mast cells even when cell proliferation was blocked for extended periods. These results suggest that the transient induction of telomerase activity in human progenitor mast cells was initially dependent on growth factor-mediated signals, whereas maintenance of high activity in tumor mast cell lines was not dependent on intracellular signals or cell replication.
Prolonged Antigen Persistence Within Nonterminal Late Endocytic Compartments of Antigen-Specific B Lymphocytes
Authors: Gondré-Lewis Timothy A. , Moquin Amy E. , Drake James R. 
Published: April 2014

Abstract
Although Ag-specific B lymphocytes can process Ag and express peptide-class II complexes as little as 1 h after Ag exposure, it requires 3–5 days for the immune system to develop a population of Ag-specific effector CD4 T lymphocytes to interact with these complexes. Presently, it is unclear how B cells maintain the expression of cell surface antigenic peptide-class II complexes until effector CD4 T lymphocytes become available. Therefore, we investigated B cell receptor (BCR)-mediated Ag processing and presentation by normal B lymphocytes to determine whether these cells have a mechanism to prolong the cell surface expression of peptide-class II complexes derived from the processing of cognate Ag. Interestingly, after transit of early endocytic compartments, internalized Ag-BCR complexes are delivered to nonterminal late endosomes where they persist for a prolonged period of time. In contrast, Ags internalized via fluid phase endocytosis are rapidly delivered to terminal lysosomes and degraded. Moreover, persisting Ag-BCR complexes within nonterminal late endosomes exhibit a higher degree of colocalization with the class II chaperone HLA-DM/H2-M than with the HLA-DM/H2-M regulator HLA-DO/H2-O. Finally, B cells harboring persistent Ag-BCR complexes exhibit prolonged cell surface expression of antigenic peptide-class II complexes. These results demonstrate that B lymphocytes possess a mechanism for prolonging the intracellular persistence of Ag-BCR complexes within nonterminal late endosomes and suggest that this intracellular Ag persistence allows for the prolonged cell surface expression of peptide-class II complexes derived from the processing of specific Ag.
Tetramer-Guided Epitope Mapping: Rapid Identification and Characterization of Immunodominant CD4+ T Cell Epitopes from Complex Antigens
Authors: Novak Erik J. , Liu Andrew W. , Gebe John A. , Falk Ben A. , Nepom Gerald T. , Koelle David M. , Kwok William W. 
Published: April 2014

Abstract
T cell responses to Ags involve recognition of selected peptide epitopes contained within the antigenic protein. In this report, we describe a new approach for direct identification of CD4+ T cell epitopes of complex Ags that uses human class II tetramers to identify reactive cells. With a panel of 60 overlapping peptides covering the entire sequence of the VP16 protein, a major Ag for HSV-2, we generated a panel of class II MHC tetramers loaded with peptide pools that were used to stain peripheral lymphocytes of an HSV-2 infected individual. With this approach, we identified four new DRA1*0101/DRB1*0401- and two DRA1*0101/DRB1*0404-restricted, VP16-specific epitopes. By using tetramers to sort individual cells, we easily obtained a large number of clones specific to these epitopes. Although DRA1*0101/DRB1*0401 and DRA1*0101/DRB1*0404 are structurally very similar, nonoverlapping VP16 epitopes were identified, illustrating high selectivity of individual allele polymorphisms within common MHC variants. This rapid approach to detecting CD4+ T cell epitopes from complex Ags can be applied to any known Ag that gives a T cell response.
Peptide Binding to Active Class II MHC Protein on the Cell Surface
Authors: Vacchino Judith F. , McConnell Harden M. 
Published: April 2014

AbstractSolution studies have demonstrated the existence of two functionally distinct isomers of empty class II MHC: an active isomer that binds peptide and an inactive isomer that does not. Empty MHC molecules on the surface of APCs can load antigenic peptides directly from the extracellular medium, facilitating the generation of a diverse peptide repertoire for T cell presentation. In this report, we examine I-Ek on the surface of Chinese hamster ovary cells with respect to the active and inactive isomers. As in the case of purified soluble active I-Ek, active I-Ek on the cell surface is unstable, decaying to the inactive form in ∼14 min. Evidence is presented suggesting that at steady state &lt;1% of the total cell surface I-Ek is active and that a significant fraction of these active molecules originates from intracellular pools as well as reactivation of inactive cell surface I-Ek.
Dissociation of Pax-5 from KI and KII Sites During κ-Chain Gene Rearrangement Correlates with Its Association with the Underphosphorylated Form of Retinoblastoma
Authors: Sato Hiromu , Wang Dan , Kudo Akira 
Published: April 2014

AbstractThe KI and KII sites play a crucial role in κ-chain gene rearrangement, which was investigated in mice deficient for these sites. Previously, we found that Pax-5 can bind to the KI and KII sites; however, the function of Pax-5 in κ-chain gene rearrangement has not been investigated. Here, we have used an in vitro culture system in which differentiation from pre-B cells to immature B cells is induced by removing IL-7. We showed that, after the induction of differentiation, Pax-5 dissociated from the KI and KII revealed by EMSA analyses, and this dissociation occurred specifically at the KI and KII sites, but not at the Pax-5 binding site, in the CD19 promoter because of a lower binding affinity of Pax-5 for the KI and KII sites. During differentiation induced by removing IL-7, the underphosphorylated form of retinoblastoma preferentially associated with Pax-5, which caused dissociation of Pax-5 from KI and KII sites. These results suggest that the dissociation of Pax-5 from the KI and KII sites is important in the induction of κ-chain gene rearrangement.
Naturally Processed HLA Class II Peptides Reveal Highly Conserved Immunogenic Flanking Region Sequence Preferences That Reflect Antigen Processing Rather Than Peptide-MHC Interactions
Authors: Godkin Andrew J. , Smith Kathrine J. , Willis Anthony , Tejada-Simon Maria V. , Zhang Jingwu , Elliott Tim , Hill Adrian V. S. 
Published: April 2014

Abstract
MHC class II heterodimers bind peptides 12–20 aa in length. The peptide flanking residues (PFRs) of these ligands extend from a central binding core consisting of nine amino acids. Increasing evidence suggests that the PFRs can alter the immunogenicity of T cell epitopes. We have previously noted that eluted peptide pool sequence data derived from an MHC class II Ag reflect patterns of enrichment not only in the core binding region but also in the PFRs. We sought to distinguish whether these enrichments reflect cellular processes or direct MHC-peptide interactions. Using the multiple sclerosis-associated allele HLA-DR2, pool sequence data from naturally processed ligands were compared with the patterns of enrichment obtained by binding semicombinatorial peptide libraries to empty HLA-DR2 molecules. Naturally processed ligands revealed patterns of enrichment reflecting both the binding motif of HLA-DR2 (position (P)1, aliphatic; P4, bulky hydrophobic; and P6, polar) as well as the nonbound flanking regions, including acidic residues at the N terminus and basic residues at the C terminus. These PFR enrichments were independent of MHC-peptide interactions. Further studies revealed similar patterns in nine other HLA alleles, with the C-terminal basic residues being as highly conserved as the previously described N-terminal prolines of MHC class II ligands. There is evidence that addition of C-terminal basic PFRs to known peptide epitopes is able to enhance both processing as well as T cell activation. Recognition of these allele-transcending patterns in the PFRs may prove useful in epitope identification and vaccine design.
A Novel Interaction Between Type IV Pili ofNeisseria gonorrhoeaeand the Human Complement Regulator C4b-Binding Protein
Authors: Blom Anna M. , Rytkönen Anne , Vasquez Paola , Lindahl Gunnar , Dahlbäck Björn , Jonsson Ann-Beth 
Published: April 2014

AbstractC4b-binding protein (C4BP) is an important plasma inhibitor of the classical pathway of complement activation. Several bacterial pathogens bind C4BP, which may contribute to their virulence. In the present report we demonstrate that isolated type IV pili from Neisseria gonorrhoeae bind human C4BP in a dose-dependent and saturable manner. C4BP consists of seven identical α-chains and one β-chain linked together with disulfide bridges. We found that pili bind to the α-chain of C4BP, which is composed of eight homologous complement control protein (CCP) domains. From the results of an inhibition assay with C4b and a competition assay in which we tested mutants of C4BP lacking individual CCPs, we concluded that the binding area for pili is localized to CCP1 and CCP2 of the α-chain. The binding between pili and C4BP was abolished at 0.25 M NaCl, implying that it is based mostly on ionic interactions, similarly to what have been observed for C4b-C4BP binding. Furthermore, the N-terminal part of PilC, a structural component of pili, appeared to be responsible for binding of C4BP. Membrane cofactor protein, previously shown to be a receptor for pathogenic N. gonorrhoeae on the surface of epithelial cells, competed with C4BP for binding to pili only at high concentrations, suggesting that different parts of pili are involved in these two interactions. Accordingly, high concentrations of C4BP were required to inhibit binding of N. gonorrhoeae to Chang conjunctiva cells, and no inhibition of binding was observed with cervical epithelial cells.