bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of the CTL Response by Macrophage Migration Inhibitory Factor
Authors: Abe Riichiro , Peng Tina , Sailors Joseph , Bucala Richard , Metz Christine N. 
Published: April 2014

AbstractMacrophage migration inhibitory factor (MIF) has been shown to be a pivotal cytokine that mediates host inflammatory and immune responses. Recently, immunoneutralization of MIF has been found to inhibit tumor growth in mice; however, the contributing mechanisms underlying this effect have not been well defined. We investigated whether MIF plays a regulatory role in the expression of CTL activity. In a mouse model of the CTL response using the OVA-transfected tumor cell line EL4 (EG.7), we found that cultures of splenocytes obtained from EG.7-primed mice secrete high levels of MIF following Ag stimulation in vitro. Notably, parallel splenocyte cultures treated with neutralizing anti-MIF mAb showed a significant increase in the CTL response directed against EG.7 cells compared with control mAb-treated cultures. This effect was accompanied by elevated expression of IFN-γ. Histological examination of the EG.7 tumors from anti-MIF-treated animals showed a prominent increase in both CD4+ and CD8+ T cells as well as apoptotic tumor cells, consistent with the observed augmentation of CTL activity in vivo by anti-MIF. This increased CTL activity was associated with enhanced expression of the common γc-chain of the IL-2R that mediates CD8+ T cell survival. Finally, CD8+ T lymphocytes obtained from the spleens of anti-MIF-treated EG.7 tumor-bearing mice, when transferred into recipient tumor-bearing mice, showed increased accumulation in the tumor tissue. These data provide the first evidence of an important role for MIF in the regulation and trafficking of anti-tumor T lymphocytes in vivo.
A Molecular Framework for Two-Step T Cell Signaling: Lck Src Homology 3 Mutations Discriminate Distinctly Regulated Lipid Raft Reorganization Events
Authors: Patel Viresh P. , Moran Miriana , Low Teresa A. , Miceli M. Carrie 
Published: April 2014

AbstractCostimulation by CD28 or lipid-raft-associated CD48 potentiate TCR-induced signals, cytoskeletal reorganization, and IL-2 production. We and others have proposed that costimulators function to construct a raft-based platform(s) especially suited for TCR engagement and sustained and processive signal transduction. Here, we characterize TCR/CD48 and TCR/CD28 costimulation in T cells expressing Lck Src homology 3 (SH3) mutants. We demonstrate that Lck SH3 functions after initiation of TCR-induced tyrosine phosphorylation and concentration of transducers within rafts, to regulate the costimulation-dependent migration of rafts to the TCR contact site. Expression of kinase-active/SH3-impaired Lck mutants disrupts costimulation-dependent raft recruitment, sustained TCR protein tyrosine phosphorylation, and IL-2 production. However, TCR-induced apoptosis, shown only to require “partial” TCR signals, is unaffected by expression of kinase-active/SH3-impaired Lck mutants. Therefore, two distinctly regulated raft reorganization events are required for processive and sustained “complete” TCR signal transduction and T cell activation. Together with recent characterization of CD28 and CD48 costimulatory activities, these findings provide a molecular framework for two signal models of T cell activation.
Mutation of the Hematopoietic Cell Phosphatase (Hcph) Gene Is Associated with Resistance to γ-Irradiation-Induced Apoptosis in Src Homology Protein Tyrosine Phosphatase (SHP)-1-Deficient “Motheaten” Mutant Mice
Authors: Hsu Hui-Chen , Shultz Leonard D. , Su Xiao , Shi Jian , Yang Ping-Ar , Relyea Melissa J. , Zhang Huang-Ge , Mountz John D. 
Published: April 2014

Abstract
To determine the role of Src homology protein tyrosine phosphatase (SHP-1) in the ionizing radiation-induced stress response, we analyzed the apoptotic response and cell cycle function in irradiated spleen cells of motheaten (me/me) mice. The defect in me/me mice has been attributed to mutations of the Hcph gene, which encodes SHP-1. Homozygotes develop severe systemic autoimmune and inflammatory disease, whereas heterozygotes live longer and develop hematopoietic and lymphoid malignance. Spleen cells from C57BL/6 (B6)-me/me and B6-+/+ controls were analyzed after γ-irradiation from a 137Cs source. B6-me/me cells were significantly more resistant than B6-+/+ cells to γ-irradiation-induced apoptosis exhibiting a higher LD50. The defective apoptosis response of the B6-me/me cells was exhibited by T and B cells and macrophages. Of the Bcl-2 family members analyzed, a significant difference was observed in the transcription of Bax mRNA, which was up-regulated early after irradiation in B6-+/+ cells, but not B6-me/me cells. Analysis of 3,3′-dihexyloxacarbocyanine iodide revealed resistance to the γ-irradiation-induced mitochondrial transmembrane permeability transition in the B6-me/me cells. The blocking of the cell cycle in the G0/G1 phase characteristic of the irradiated B6-+/+ cells was not observed in the B6-me/me cells. There was decreased phosphorylation of p38 mitogen-activated protein kinase and increased phosphorylation of p53 from spleen cell lysates of irradiated B6-me/me mice compared with wild-type mice. These data suggest that SHP-1 plays an important role in regulation of apoptosis and cell cycle arrest after a γ-irradiation-induced stress response.
Uterine Macrophages Express the gp49B Inhibitory Receptor in Midgestation
Authors: Matsumoto Yukie , Wang Lawrence L. , Yokoyama Wayne M. , Aso Takeshi 
Published: April 2014

Abstract
Mouse gp49B is an immunoreceptor tyrosine-based inhibitory motif-bearing receptor identified on mast cells and NK cells. In this report, however, we show that this receptor is expressed on macrophages accumulating in the uterine metrial gland in midgestation, along with gp49A that has a very homologous extracellular domain with gp49B but has a short cytoplasmic domain without ITIM. Culture of bone marrow cells in the conditioned medium of the metrial gland resulted in the selective proliferation of macrophages expressing both Fcγ-activating receptors and gp49B inhibitory receptor. Stimulation of macrophages with immobilized IgG, but not with anti-FcγRII/III, induced a considerable amount of TNF-α and IL-10 production, suggesting that the high-affinity receptor for IgG (FcγRI) can transmit activating signals in cytokine production of macrophages. Furthermore, coligation of gp49B with FcγRI resulted in the inhibition of TNF-α production. Thus, our data provide evidence that gp49B is an endogenous negative regulator of macrophage activation and may regulate the function of macrophages during pregnancy.
Amino Acid Substitutions in the Putative MHC Class II “Dimer of Dimers” Interface Inhibit CD4+ T Cell Activation
Authors: Lindstedt Ragnar , Monk Nicola , Lombardi Giovanna , Lechler Robert 
Published: April 2014

Abstract
Activation of T lymphocytes is dependent on multiple ligand-receptor interactions. The possibility that TCR dimerization contributes to T cell triggering was raised by the crystallographic analysis of MHC class II molecules. The MHC class II molecules associated as double dimers, and in such a way that two TCR (and two CD4 molecules) could bind simultaneously. Several subsequent studies have lent support to this concept, although the role of TCR cross-linking in T cell activation remains unclear. Using DRA cDNAs modified to encode two different C-terminal tags, no evidence of constitutive double dimer formation was obtained following immunoprecipitation and Western blotting from cells transiently transfected with wild-type DRB and tagged DRA constructs, together with invariant chain and HLA-DM. To determine whether MHC class II molecules contribute actively to TCR-dependent dimerization and consequent T cell activation, panels of HLA-DR1β and H2-Ek cDNAs were generated with mutations in the sequences encoding the interface regions of the MHC class II double dimer. Stable DAP.3 transfectants expressing these cDNAs were generated and characterized biochemically and functionally. Substitutions in either interface region I or III did not affect T cell activation, whereas combinations of amino acid substitutions in both regions led to substantial inhibition of proliferation or IL-2 secretion by human and murine T cells. Because the amino acid-substituted molecules were serologically indistinguishable from wild type, bound antigenic peptide with equal efficiency, and induced Ag-dependent CD25 expression indicating TCR recognition, the reduced ability of the mutants to induce full T cell activation is most likely the result of impaired double dimer formation. These data suggest that MHC class II molecules, due to their structural properties, actively contribute to TCR cross-linking.
Positive and Negative Selection of Thymocytes Depends on Lck Interaction with the CD4 and CD8 Coreceptors
Authors: Trobridge Patty A. , Forbush Katherine A. , Levin Steven D. 
Published: April 2014

Abstract
Considerable evidence supports a role for the Src family protein tyrosine kinase Lck in regulating multiple aspects of thymocyte development. In this report, we establish that early events in T lymphopoiesis are restored to Lck-deficient mice by provision of a transgene encoding a version of Lck that cannot interact with the coreceptors CD4 and CD8. In addition, we demonstrate that later events in thymocyte development, specifically, the processes of positive and negative selection, are compromised in mice where the only Lck available cannot associate with either CD4 or CD8. We conclude that not only is Lck activity required for positive and negative selection, but that that activity must be coupled to the CD4 and CD8 coreceptors.
Salicylates Inhibit T Cell Adhesion on Endothelium Under Nonstatic Conditions: Induction of L-Selectin Shedding by a Tyrosine Kinase-Dependent Mechanism
Authors: Gerli Roberto , Gresele Paolo , Bistoni Onelia , Paolucci Cristina , Lanfrancone Luisa , Fiorucci Stefano , Muscat Christopher , Costantini Vincenzo 
Published: April 2014

Abstract
Salicylates inhibit T cell adhesion to and transmigration through endothelium by preventing integrin activation induced by contact with endothelial cells. In the present study the effects of aspirin and sodium salicylate on the first steps of T cell adhesion have been analyzed in a nonstatic in vitro system. Salicylates partially reduced adhesion to activated endothelium and, in parallel, L-selectin expression on resting T cells by inducing shedding of the molecule without affecting its mRNA transcript. The role of L-selectin down-regulation in reducing T cell adhesion in this system was supported by the fact that aspirin inhibited T cell adhesion also on plastic-immobilized L-selectin ligand or when α4 integrin-mediated adhesion to endothelium was blocked by specific mAbs. In addition, preincubation of T cells with inhibitors of L-selectin shedding prevented both functional and phenotypic inhibitory effects of salicylates. The decrease in T cell adhesion and L-selectin expression seems to be dependent on intracellular calcium increase and tyrosine kinase activation, because these effects could be reversed by preincubating salicylate-treated T cells with EGTA, genistein, or tyrphostin. Finally, the infusion of aspirin into healthy volunteers induced down-regulation of L-selectin on circulating T cells. These results suggest that salicylates interfere not only with integrin activation, but also with the L-selectin-mediated first steps of T cell binding to endothelium.
Role of CD40 in a T Cell-Mediated Negative Regulation of Ig Production
Authors: Majlessi Laleh , Bordenave Guy 
Published: April 2014

Abstract
To investigate the possible role of CD40 in a negative regulation of Ig production, we used the mouse Ig allotype suppression model. T splenocytes from Igha/a mice are able in vivo to totally and chronically inhibit the production of IgG2ab (IgG2a from the Ighb haplotype). Accordingly, postnatal transfer of Igha/a T splenocytes into histocompatible Igha/b F1 or congenic Ighb/b mice leads to a characteristic IgG2ab suppression. The helper action of anti-IgG2ab CD4+ T cells is required for the recruitment of anti-IgG2ab CD8+ T suppression effectors. The latter use perforin (pore-forming protein, Pfp)- and/or Fas-dependent cytotoxic pathways to continuously eliminate B cells recently committed to IgG2ab production. In the present study we first showed that in vivo agonistic anti-CD40 mAb treatment of Igha/a mice, deprived of their CD4+ T cell compartment, could bypass the help of Ig allotype-specific CD4+ T cells and generate CD8+ T effector cells able to strongly inhibit IgG2ab production. This result demonstrates the usefulness of CD40 triggering in setting up an immune regulatory mechanism. Furthermore, with regard to the suppression-effector mechanism, we demonstrated that B cell CD40 expression was required for full suppression establishment via the Fas-dependent pathway. Indeed, Igha/a Pfp°/° T cells (using exclusively the Fas pathway) induced full IgG2ab suppression against Ighb/b CD40+/+ B cells, but only partial inhibition of IgG2ab production against Ighb/b CD40°/° B cells. This finding provides the first demonstration of direct involvement of B cell CD40 expression in in vivo negative control of an Ig production.
VH Gene Replacement in Thymocytes
Authors: Golub Rachel , Martin Denise , Bertrand Fred E. , Cascalho Marilia , Wabl Matthias , Wu Gillian E. 
Published: April 2014

Abstract
The quasi-monoclonal (QM) mouse has a functionally rearranged H chain gene inserted into its natural position in the IgH locus. In this position, the H chain gene is subject to many of the same activities as normally arranged H chain genes, including somatic hypermutation, VH gene replacement, and class switch recombination. Here, we have used this mouse strain to determine some of the rules that govern the V(D)J recombination activity of the IgH locus in thymus. We focused on the requirements for VH gene replacement. In normal mice, thymic DJH rearrangements are common, but VDJH rearrangements are not. We found intermediate products of VH replacement in double-positive CD4+CD8+ cells of the QM thymus, demonstrating that the inserted VH gene was accessible and ruling out the possibility that a VH gene per se cannot be rearranged in the thymus. We found transcripts from the knocked-in H chain gene of QM, but no μ H chain protein was detectable in thymocytes. Cloning and sequencing of these transcripts revealed that some had been generated by VH gene replacement. Corresponding signal joints could also be identified. These results suggest that neither a B cell-specific signal nor an Ig protein are necessary to activate VH-to-VDJH joining in thymocytes. Possible mechanisms remaining to account for overcoming the barrier to VH joining in thymocytes include the insertion of a transcriptionally active gene segment and/or the inactivation of a silencer.
Attenuation of Very Late Antigen-5-Mediated Adhesion of Bone Marrow-Derived Mast Cells to Fibronectin by Peptides with Inverted Hydropathy to EF-Hands
Authors: Houtman René , Ten Broeke Robert , Blalock J. Edwin , Villain Matteo , Koster Andries S. , Nijkamp Frans P. 
Published: April 2014

Abstract
Release of allergic mediators from mast cells is enhanced by very late Ag (VLA)-5-mediated interaction of these cells with fibronectin. In this report, we show that VLA-5-mediated adhesion of bone marrow-derived mast cells to fibronectin can be induced by two different pathways: first, FcεRI clustering, which depends on calmodulin activation and extracellular Ca2+, and, second, by Mn2+ stimulation, which is independent of calmodulin activation and antagonized by Ca2+. Previous studies have shown the presence of several cation-binding domains in VLA-5 that are homologous to the calcium-binding EF-hands of calmodulin. To show a role for EF-hands of different proteins in VLA-5-mediated adhesion, we used calcium-like peptides (CALP), CALP1 and CALP2, designed to bind to EF-hands based on inverted hydropathy. CALP1 and, more potently, CALP2 inhibited FcεRI-induced adhesion to fibronectin via different mechanisms. The target for the effects of CALP1 and 2 on FcεRI-induced adhesion and degranulation was intracellular and likely involved calmodulin. Interestingly only CALP2 was able to inhibit Mn2+-induced calmodulin-independent adhesion by interfering with an extracellular target, which is probably VLA-5. We conclude that CALP1 and 2 can inhibit VLA-5-mediated adhesion of mast cells to fibronectin through binding to EF-hands of multiple proteins, and that these peptides can be used as lead compounds for the development of future therapy against allergy.
Mast Cell-Dependent B and T Lymphocyte Activation Is Mediated by the Secretion of Immunologically Active Exosomes
Authors: Skokos Dimitris , Le Panse Sophie , Villa Irène , Rousselle Jean-Claude , Peronet Roger , David Bernard , Namane Abdelkader , Mécheri Salaheddine 
Published: April 2014

Abstract
Mitogenic activity of bone marrow-derived mouse mast cells and mast cell lines P815 and MC/9 on B and T lymphocytes is present in their culture supernatants. To identify this activity, mast cells were incubated in serum-free medium and the supernatant was subjected to differential centrifugation, which resulted in two fractions, the hypodense and dense fraction (pellet). When analyzed for their mitogenic activity on spleen cells, all activity was found to be associated with the dense fraction. Electron microscopy studies revealed the presence in this fraction of small vesicles called exosomes with a heterogeneous size from 60 to 100 nm of diameter. When cocultured with spleen cells, purified exosomes induced blast formation, proliferation, as well as IL-2 and IFN-γ production, but no detectable IL-4. Similar data were obtained by injecting exosomes into naive mice. In contrast to mast cell lines, a pretreatment with IL-4 is required for bone marrow-derived mast cells to secrete active exosomes. Structurally, exosomes were found to harbor immunologically relevant molecules such as MHC class II, CD86, LFA-1, and ICAM-1. These findings indicate that mast cells can represent a critical component of the immunoregulatory network through secreted exosomes that display mitogenic activity on B and T lymphocytes both in vitro and in vivo.
CCR7 Expression and Memory T Cell Diversity in Humans
Authors: Campbell James J. , Murphy Kristine E. , Kunkel Eric J. , Brightling Christopher E. , Soler Dulce , Shen Zhimin , Boisvert Judie , Greenberg Harry B. , Vierra Mark A. , Goodman Stuart B. , Genovese Mark C. , Wardlaw Andrew J. , Butcher Eugene C. , Wu Lijun 
Published: April 2014

Abstract
CCR7, along with L-selectin and LFA-1, mediates homing of T cells to secondary lymphoid organs via high endothelial venules (HEV). CCR7 has also been implicated in microenvironmental positioning of lymphocytes within secondary lymphoid organs and in return of lymphocytes and dendritic cells to the lymph after passage through nonlymphoid tissues. We have generated mAbs to human CCR7, whose specificities correlate with functional migration of lymphocyte subsets to known CCR7 ligands. We find that CCR7 is expressed on the vast majority of peripheral blood T cells, including most cells that express adhesion molecules (cutaneous lymphocyte Ag α4β7 integrin) required for homing to nonlymphoid tissues. A subset of CD27(neg) memory CD4 T cells from human peripheral blood is greatly enriched in the CCR7(neg) population, as well as L-selectin(neg) cells, suggesting that these cells are incapable of homing to secondary lymphoid organs. Accordingly, CD27(neg) T cells are rare within tonsil, a representative secondary lymphoid organ. All resting T cells within secondary lymphoid organs express high levels of CCR7, but many activated cells lack CCR7. CCR7 loss in activated CD4 cells accompanies CXC chemokine receptor (CXCR)5 gain, suggesting that the reciprocal expression of these two receptors may contribute to differential positioning of resting vs activated cells within the organ. Lymphocytes isolated from nonlymphoid tissues (such as skin, lung, or intestine) contain many CD27(neg) cells lacking CCR7. The ratio of CD27(neg)/CCR7(neg) cells to CD27(pos)/CCR7(pos) cells varies from tissue to tissue, and may correlate with the number of cells actively engaged in Ag recognition within a given tissue.
Prostaglandin E2 Suppressed IL-15-Mediated Human NK Cell Function Through Down-Regulation of Common γ-Chain
Authors: Joshi Pratibha C. , Zhou Xinchun , Cuchens Marvin , Jones Quintus 
Published: April 2014

Abstract
NK cell function is regulated by cytokines and certain biochemical mediators in a positive or negative manner. This study was performed to investigate the suppressive effects of PGE2 on IL-15-activated human NK cell function. Purified NK cells were cultured with 200 ng/ml IL-15 for 2 days in the presence or absence of 10–200 ng/ml PGE2. PGE2 significantly suppressed NK cell-mediated cytotoxicity and IFN-γ production at the secretional and the transcriptional levels. We also evaluated the effect of PGE2 on the IL-15R complex that consists of IL-2Rβ, common γ-chain (γc-chain), and a specific chain IL-15Rα. Percentage of positive cells and number of binding sites for γc-chain were significantly increased after IL-15 treatment; however, a substantial decrease was observed with PGE2 cotreatment. In contrast, constitutive expression of IL-2Rβ was significantly decreased after IL-15 treatment, with no change detected in the presence of PGE2. At the transcriptional level, neither IL-15 nor PGE2 had significant effects on the expression of β- or γc-chains. There was a 3-fold increase in the expression of IL-15Rα at the transcriptional level that peaked at 8 h after IL-15 treatment; however, PGE2 had no significant effect. Suppression of NK function by PGE2 was not due to the endogenous production of IL-4, IL-10, or TGF-β1 by NK cells. These results suggest that down-regulation of surface expression of γc-chain on NK cells may be one mechanism through which PGE2 mediates suppression of IL-15-activated NK cell function.
The Targeting of Somatic Hypermutation Closely Resembles That of Meiotic Mutation
Authors: Oprea Mihaela , Cowell Lindsay G. , Kepler Thomas B. 
Published: April 2014

AbstractWe have compared the microsequence specificity of mutations introduced during somatic hypermutation (SH) and those introduced meiotically during neutral evolution. We have minimized the effects of selection by studying nonproductive (hence unselected) Ig V region genes for somatic mutations and processed pseudogenes for meiotic mutations. We find that the two sets of patterns are very similar: the mutabilities of nucleotide triplets are positively correlated between the somatic and meiotic sets. The major differences that do exist fall into three distinct categories: 1) The mutability is sharply higher at CG dinucleotides under meiotic but not somatic mutation. 2) The complementary triplets AGC and GCT are much more mutable under somatic than under meiotic mutation. 3) Triplets of the form WAN (W = T or A) are uniformly more mutable under somatic than under meiotic mutation. Nevertheless, the relative mutabilities both within this set and within the SAN (S = G or C) triplets are highly correlated with those under meiotic mutation. We also find that the somatic triplet specificity is strongly symmetric under strand exchange for A/T triplets as well as for G/C triplets in spite of the strong predominance of A over T mutations. Thus, we suggest that somatic mutation has at least two distinct components: one that specifically targets AGC/GCT triplets and another that acts as true catalysis of meiotic mutation.