bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contrasting Effects of Low-Dose IL-2 on Vaccine-Boosted Simian Immunodeficiency Virus (SIV)-Specific CD4+ and CD8+ T Cells in Macaques Chronically Infected with SIVmac251
Authors: Nacsa Janos , Edghill-Smith Yvette , Tsai Wen-Po , Venzon David , Tryniszewska Elzbieta , Hryniewicz Anna , Moniuszko Marcin , Kinter Audrey , Smith Kendall A. , Franchini Genoveffa 
Published: April 2014

Abstract
IL-2, the first cytokine discovered with T cell growth factor activity, is now known to have pleiotropic effects on T cells. For example, it can promote growth, survival, and differentiation of Ag-selected cells, or facilitate Ag-induced cell death of T cells when Ag persists, and in vivo, it is thought to contribute to the regulation of the size of adaptive T cell response. IL-2 is deficient in HIV-1 infection and has been used in the management of HIV-1-infected individuals undergoing antiretroviral therapy. In this study, we investigated how continuous low-dose IL-2 affected the CD4+ and CD8+ T cell response induced by two inoculations of a canarypox recombinant SIV-based vaccine candidate in healthy macaques chronically infected with SIVmac251. These macaques had normal levels of CD4+ T cells at the beginning of antiretroviral therapy treatment. Vaccination in the presence of IL-2 significantly augmented Gag-specific CD8+ T cell responses, but actually reduced Gag-specific CD4+ T cell responses. Although IL-2 at low doses did not change the overall concentration of circulating CD4+ or CD8+ T cells, it expanded the frequency of CD4+CD25+ T cells. Depletion of the CD4+CD25+ T cells in vitro, however, did not result in a reconstitution of Gag-specific CD4+ responses or augmentation of SIV-specific CD8+ T cell responses. Thus, we conclude that the decrease in virus-specific CD4+ T cell response may be due to IL-2-promoted redistribution of cells from the circulation, or due to Ag-induced cell death, rather than suppression by a T regulatory population.
Engagement of NKG2D by Cognate Ligand or Antibody Alone Is Insufficient to Mediate Costimulation of Human and Mouse CD8+ T Cells
Authors: Ehrlich Lauren I. Richie , Ogasawara Kouetsu , Hamerman Jessica A. , Takaki Rayna , Zingoni Alessandra , Allison James P. , Lanier Lewis L. 
Published: April 2014

Abstract
CD8+ T cells require a signal through a costimulatory receptor in addition to TCR engagement to become activated. The role of CD28 in costimulating T cell activation is well established. NKG2D, a receptor found on NK cells, CD8+ αβ-TCR+ T cells, and γδ-TCR+ T cells, has also been implicated in T cell costimulation. In this study we have evaluated the role of NKG2D in costimulating mouse and human naive and effector CD8+ T cells. Unexpectedly, in contrast to CD28, NKG2D engagement by ligand or mAb is not sufficient to costimulate naive or effector CD8+ T cell responses in conventional T cell populations. While NKG2D did not costimulate CD8+ T cells on its own, it was able to modify CD28-mediated costimulation of human CD8+ T cells under certain contitions. It is, therefore, likely that NKG2D acts as a costimulatory molecule only under restricted conditions or requires additional cofactors.
Vascular Endothelial Cells Have Impaired Capacity to Present Immunodominant, Antigenic Peptides: A Mechanism of Cell Type-Specific Immune Escape
Authors: Kummer Marco , Lev Avital , Reiter Yoram , Biedermann Barbara C. 
Published: April 2014

Abstract
Vascular endothelial cells (EC) are an exposed target tissue in the course of CTL-mediated alloimmune diseases such as graft-vs-host disease (GVHD) or solid organ transplant rejection. The outcome of an interaction between CTL and target cells is determined by the amount of Ag presented and the costimulatory signals delivered by the target cells. We compared human EC with leukocytes and epithelial cells as targets for peptide-specific, MHC class I-restricted CTL clones. EC were poor targets for immunodominant CTL. Both endogenously processed antigenic proteins and exogenously added antigenic peptides are presented at 50- to 5000-fold lower levels on EC compared with any other target cell analyzed. This quantitative difference fully explained the poor CTL-mediated killing of EC. There was no evidence that lack of costimulation would contribute significantly to this cell type-specific difference in CTL activation. An HLA-A2-specific CTL clone that killed a broad selection of HLA A2-positive target cells equally well, killed EC less efficiently. Our data suggest that EC present a different Ag repertoire compared with other cell types. By this mechanism, these cells may escape an attack by effector CTL, which have been educated by professional APCs and are specific for immunodominant antigenic peptides.
CCR8 Is Expressed by Antigen-Elicited, IL-10-Producing CD4+CD25+ T Cells, Which Regulate Th2-Mediated Granuloma Formation in Mice
Authors: Freeman Christine M. , Chiu Bo-Chin , Stolberg Valerie R. , Hu Jerry , Zeibecoglou Kyriaki , Lukacs Nicholas W. , Lira Sergio A. , Kunkel Steven L. , Chensue Stephen W. 
Published: April 2014

AbstractCCR8 was initially described as a Th2 cell-restricted receptor, but this has not been fully tested in vivo. The present study used ex vivo and in vivo approaches to examine the distribution and functional significance of CCR8 among CD4+ T cells. Populations of cytokine-secreting CD4+ T cells were generated in primed mice with Th1 or Th2 cell-mediated pulmonary granulomas, respectively elicited by i.v. challenge with either Mycobacteria bovis purified protein derivative- or Schistosoma mansoni egg Ag (SEA)-coated beads. Cytokine-producing CD4+ T cells were isolated from Ag-stimulated draining lymph node cultures by positive selection. Quantitative analysis of cytokine mRNA indicated enriched populations of IFN-γ-, IL-4-, and IL-10-producing cells. Analysis of chemokine receptor mRNA indicated that IL-10+ cells selectively expressed CCR8 in the SEA bead-elicited type 2 response. The IL-10+CCR8+ populations were CD25+ and CD44+ but lacked enhanced Foxp3 expression. Adoptive transfer to naive recipients indicated that IL-10+ T cells alone could not transfer type 2 inflammation. Analysis of SEA bead-challenged CCR8−/− mice indicated significantly impaired IL-10 production as well as reductions in granuloma eosinophils. Adoptive transfer of CD4+CCR8+/+ T cells corrected cytokine and inflammation defects, but the granuloma eosinophil recruitment defect persisted when donor cells were depleted of IL-10+ cells. Accordingly, local IL-10 production correlated with CCR8 ligand (CCL1) expression and the appearance of CCR8+ cells in granulomatous lungs. Thus, IL-10-producing, CCR8+CD4+CD25+CD44+ T cells are generated during SEA challenge, which augment the Th2-mediated eosinophil-rich response to the parasite Ags.
ICOS-Mediated Costimulation on Th2 Differentiation Is Achieved by the Enhancement of IL-4 Receptor-Mediated Signaling
Authors: Watanabe Masashi , Watanabe Shiho , Hara Yasushi , Harada Yohsuke , Kubo Masato , Tanabe Kazunari , Toma Hiroshi , Abe Ryo 
Published: April 2014

Abstract
ICOS is the third member of the CD28 family molecules and plays a critical role in many T cell-dependent immune responses. Although accumulated data suggest that ICOS costimulatory signals play an important role in Th2-mediated immune responses, the molecular basis for this selective differentiation mechanism is largely unknown. To clarify this mechanism, we used DO11.10 TCR transgenic ICOS−/− mice and evaluated the nature of ICOS costimulatory signals during the process of Ag-specific activation and differentiation of naive CD4+ T cells. Results obtained from these experiments demonstrated that Ag stimulation of naive CD4+ T cells in the absence of an ICOS signal resulted in impaired Th2 development. Unlike previous reports, we found that primary IL-4 production by these T cells was intact and that IL-4R sensitivity of these T cells was reduced as evidenced by a profound defect in IL-4-induced Stat6 phosphorylation and the early induction of GATA-3. The fact that ICOS ligation of wild-type T cells significantly enhanced IL-4-induced Stat6 phosphorylation and primary GATA-3 induction, but not IL-4 transcription, of naive CD4+ T cells was consistent with the results obtained from ICOS−/− T cell experiments. These observations led us to propose that the predominant effect of ICOS-mediated costimulation on Th2 differentiation is achieved by the enhancement of IL-4R-mediated signaling.
Negative Regulation of Phagocytosis in Macrophages by the CD47-SHPS-1 System
Authors: Okazawa Hideki , Motegi Sei-ichiro , Ohyama Naoko , Ohnishi Hiroshi , Tomizawa Takeshi , Kaneko Yoriaki , Oldenborg Per-Arne , Ishikawa Osamu , Matozaki Takashi 
Published: April 2014

Abstract
Src homology 2 domain-containing protein tyrosine phosphatase (SHP) substrate-1 (SHPS-1) is a transmembrane protein that is expressed predominantly in macrophages. Its extracellular region interacts with the transmembrane ligand CD47 expressed on the surface of adjacent cells, and its cytoplasmic region binds the protein tyrosine phosphatases SHP-1 and SHP-2. Phagocytosis of IgG- or complement-opsonized RBCs by peritoneal macrophages derived from mice that express a mutant SHPS-1 protein that lacks most of the cytoplasmic region was markedly enhanced compared with that apparent with wild-type macrophages. This effect was not observed either with CD47-deficient RBCs as the phagocytic target or in the presence of blocking Abs to SHPS-1. Depletion of SHPS-1 from wild-type macrophages by RNA interference also promoted FcγR-mediated phagocytosis of wild-type RBCs. Ligation of SHPS-1 on macrophages by CD47 on RBCs promoted tyrosine phosphorylation of SHPS-1 and its association with SHP-1, whereas tyrosine phosphorylation of SHPS-1 was markedly reduced in response to cross-linking of FcγRs. Treatment with inhibitors of PI3K or of Syk, but not with those of MEK or Src family kinases, abolished the enhancement of FcγR-mediated phagocytosis apparent in macrophages from SHPS-1 mutant mice. In contrast, FcγR-mediated tyrosine phosphorylation of Syk, Cbl, or the γ subunit of FcR was similar in macrophages from wild-type and SHPS-1 mutant mice. These results suggest that ligation of SHPS-1 on macrophages by CD47 promotes the tyrosine phosphorylation of SHPS-1 and thereby prevents the FcγR-mediated disruption of the SHPS-1-SHP-1 complex, resulting in inhibition of phagocytosis. The inhibition of phagocytosis by the SHPS-1-SHP-1 complex may be mediated at the level of Syk or PI3K signaling.
Dual Requirement for the Igα Immunoreceptor Tyrosine-Based Activation Motif (ITAM) and a Conserved Non-Igα ITAM Tyrosine in Supporting Igαβ-Mediated B Cell Development
Authors: Pike Kelly A. , Ratcliffe Michael J. H. 
Published: April 2014

Abstract
Surface Ig (sIg) expression is a critical checkpoint during avian B cell development. Only cells that express sIg colonize bursal follicles, clonally expand, and undergo Ig diversification by gene conversion. Expression of a heterodimer, in which the extracellular and transmembrane domains of murine CD8α or CD8β are fused to the cytoplasmic domains of chicken Igα (chIgα) or Igβ, respectively (murine CD8α (mCD8α):chIgα + mCD8β:chIgβ), or an mCD8α:chIgα homodimer supported bursal B cell development as efficiently as endogenous sIg. In this study we demonstrate that B cell development, in the absence of chIgβ, requires both the Igα ITAM and a conserved non-ITAM Igα tyrosine (Y3) that has been associated with binding to B cell linker protein (BLNK). When associated with the cytoplasmic domain of Igβ, the Igα ITAM is not required for the induction of strong calcium mobilization or BLNK phosphorylation, but is still necessary to support B cell development. In contrast, mutation of the Igα Y3 severely compromised calcium mobilization when expressed as either a homodimer or a heterodimer with the cytoplasmic domain of Igβ. However, coexpression of the cytoplasmic domain of Igβ partially complemented the Igα Y3 mutation, rescuing higher levels of BLNK phosphorylation and, more strikingly, supporting B cell development.
Progressive Differentiation and Commitment of CD8+ T Cells to a Poorly Cytolytic CD8low Phenotype in the Presence of IL-4
Authors: Kienzle Norbert , Olver Stuart , Buttigieg Kathy , Groves Penny , Janas Michelle L. , Baz Adriana , Kelso Anne 
Published: April 2014

Abstract
Exposure to IL-4 during activation of naive murine CD8+ T cells leads to generation of IL-4-producing effector cells with reduced surface CD8, low perforin, granzyme B and granzyme C mRNA, and poor cytolytic function. We show in this study that maximal development of these cells depended on exposure to IL-4 for the first 5 days of activation. Although IL-4 was not required at later times, CD8 T cell clones continued to lose surface CD8 expression with prolonged culture, suggesting commitment to the CD8low phenotype. This state was reversible in early differentiation. When single CD8low cells from 4-day cultures were cultured without IL-4, 65% gave rise to clones that partly or wholly comprised CD8high cells; the proportion of reverted clones was reduced or increased when the cells were cloned in the presence of IL-4 or anti-IL-4 Ab, respectively. CD8 expression positively correlated with perforin and granzyme A, B, and C mRNA, and negatively correlated with IL-4 mRNA levels among these clones. By contrast, most CD8low cells isolated at later time points maintained their phenotype, produced IL-4, and exhibited poor cytolytic function after many weeks in the absence of exogenous IL-4. We conclude that IL-4-dependent down-regulation of CD8 is associated with progressive differentiation and commitment to yield IL-4-producing cells with little cytolytic activity. These data suggest that the CD4−CD8− cells identified in some disease states may be the product of a previously unrecognized pathway of effector differentiation from conventional CD8+ T cells.
Low TLR4 Expression by Liver Dendritic Cells Correlates with Reduced Capacity to Activate Allogeneic T Cells in Response to Endotoxin
Authors: De Creus An , Abe Masanori , Lau Audrey H. , Hackstein Holger , Raimondi Giorgio , Thomson Angus W. 
Published: April 2014

Abstract
Signaling via TLRs results in dendritic cell (DC) activation/maturation and plays a critical role in the outcome of primary immune responses. So far, no data exist concerning TLR expression by liver DC, generally regarded as less immunostimulatory than secondary lymphoid tissue DC. Because the liver lies directly downstream from the gut, it is constantly exposed to bacterial LPS, a TLR4 ligand. We examined TLR4 expression by freshly isolated, flow-sorted C57BL/10 mouse liver DC compared with spleen DC. Real-time PCR revealed that liver CD11c+CD8α− (myeloid) and CD11c+CD8α+ (“lymphoid-related”) DC expressed lower TLR4 mRNA compared with their splenic counterparts. Lower TLR4 expression correlated with reduced capacity of LPS (10 ng/ml) but not anti-CD40-stimulated liver DC to induce naive allogeneic (C3H/HeJ) T cell proliferation. By contrast to LPS-stimulated splenic DC, these LPS-activated hepatic DC induced alloantigen-specific T cell hyporesponsiveness in vitro, correlated with deficient Th1 (IFN-γ) and Th2 (IL-4) responses. When higher LPS concentrations (≥100 ng/ml) were tested, the capacity of liver DC to induce proliferation of T cells and Th1-type responses was enhanced, but remained inferior to that of splenic DC. Hepatic DC activated by LPS in vivo were inferior allogeneic T cell stimulators compared with splenic DC, whereas adoptive transfer of LPS-stimulated (10 ng/ml) liver DC induced skewing toward Th2 responses. These data suggest that comparatively low expression of TLR4 by liver DC may limit their response to specific ligands, resulting in reduced or altered activation of hepatic adaptive immune responses.
TGF-β and Vitamin D3 Utilize Distinct Pathways to Suppress IL-12 Production and Modulate Rapid Differentiation of Human Monocytes into CD83+ Dendritic Cells
Authors: Lyakh Lyudmila A. , Sanford Michael , Chekol Sebel , Young Howard A. , Roberts Anita B. 
Published: April 2014

Abstract
We previously demonstrated that agents known to signal infection or inflammation can rapidly and directly drive differentiation of human CD14+ monocytes into CD83+ dendritic cells (DCs) when introduced to cells under serum-free conditions. In this study, we evaluated the effects of TGF-β and vitamin D3 (VitD3) on the proportion and function of monocytes that adopt DC characteristics. TGF-β significantly decreased the proportion of cells that rapidly adopted stable DC characteristics in response to LPS, but had little or no effect on calcium ionophore-induced differentiation. In contrast, VitD3 showed no such pathway specificity and dramatically suppressed differentiation of monocytes into DCs in response to these agents. Both TGF-β and VitD3 altered cytokine and chemokine production in LPS-treated monocytes, inhibited IL-12 and IL-10 secretion, and decreased the functional capacity of DCs. Despite the similar effects of TGF-β and VitD3, there are significant differences in the signaling pathways used by these agents, as evidenced by their distinct effects on LPS- and calcium ionophore-induced DC differentiation, on LPS-induced secretion of IL-10, and on two members of the NF-κB family of transcription factors, RelB and cRel. These studies identify TGF-β and VitD3 as potent regulatory factors that use distinct pathways to suppress both the differentiation of DCs as well as their capacity to secrete the Th1-polarizing cytokine IL-12. Because these agents are present in serum and negatively affect DC differentiation at physiological concentrations, our findings are likely to have significance regarding the in vivo role of TGF-β and VitD3 in determining the type of immune responses.
Distinct Effects of TGF-β1 on CD4+ and CD8+ T Cell Survival, Division, and IL-2 Production: A Role for T Cell Intrinsic Smad3
Authors: McKarns Susan C. , Schwartz Ronald H. 
Published: April 2014

AbstractTGF-β1 is critical for maintaining T cell homeostasis. Smad3 has been implicated in this regulatory process, yet the cellular targets and molecular details remain poorly understood. In this study, we report that TGF-β1 impairs the entry of CD4+ and CD8+ T cells into the cell cycle as well as their progression through subsequent rounds of division, and show that Smad3 is essential for TGF-β1 to inhibit TCR-induced division of only CD4+ and not CD8+ T cells. Both CD8+ and CD4+ T cells from Smad3−/− mice were refractory to TGF-β1-induced inhibition of IL-2 production, thus demonstrating that not all CD8+ T cell responses to TGF-β1 are Smad3 independent. These TGF-β1 effects were all T cell intrinsic, as they were reproduced in purified CD4+ and CD8+ T cells. Finally, we found that Smad3 was critical for the survival of CD8+, but not CD4+ T cells following activation ex vivo. The TCR-induced death of Smad3−/− CD8+ T cells was not dependent upon TNF-α production. Exogenous TGF-β1 partially rescued the CD8+ T cells by signaling through a Smad3-independent pathway. TGF-β1 also enhanced survival of TCR-stimulated CD4+CD44high T cells in a Smad3-independent manner. Collectively, these findings firmly establish for the first time that TGF-β1 discriminately regulates CD4+ and CD8+ T cell expansion by signaling through distinct intracellular pathways.
The Role of MTJ-1 in Cell Surface Translocation of GRP78, a Receptor for α2-Macroglobulin-Dependent Signaling
Authors: Misra Uma Kant , Gonzalez-Gronow Mario , Gawdi Govind , Pizzo Salvatore Vincent 
Published: April 2014

Abstract
MTJ-1 associates with a glucose-regulated protein of Mr ∼78,000(GRP78) in the endoplasmic reticulum and modulates GRP78 activity as a chaperone. GRP78 also exists on the cell surface membrane, where it is associated with a number of functions. MHC class I Ags on the cell surface are complexed to GRP78. GRP78 also serves as the receptor for α2-macroglobulin-dependent signaling and for uptake of certain pathogenic viruses. The means by which GRP78, lacking a transmembrane domain, can fulfill such functions is unclear. In this study we have examined the question of whether MTJ-1, a transmembrane protein, is involved in the translocation of GRP78 to the cell surface. MTJ-1 and GRP78 coimmunoprecipitated from macrophage plasma membrane lysates. Silencing of MTJ-1 gene expression greatly reduced MTJ-1 mRNA and protein levels, but also abolished cell surface localization of GRP78. Consequently, binding of the activated and receptor-recognized form of α2-macroglobulin to macrophages was greatly reduced, and activated and receptor-recognized form of α2-macroglobulin-induced calcium signaling was abolished in these cells. In conclusion, we show that in addition to assisting the chaperone GRP78 in protein quality control in the endoplasmic reticulum, MTJ-1 is essential for transport of GRP78 to the cell surface, which serves a number of functions in immune regulation and signal transduction.
Membrane-Anchored β2-Microglobulin Stabilizes a Highly Receptive State of MHC Class I Molecules
Authors: Berko Dikla , Carmi Yaron , Cafri Gal , Ben-Zaken Shimrit , Sheikhet Helena Migalovich , Tzehoval Esther , Eisenbach Lea , Margalit Alon , Gross Gideon 
Published: April 2014

AbstractThe magnitude of response elicited by CTL-inducing vaccines correlates with the density of MHC class I (MHC-I)-peptide complexes formed on the APC membrane. The MHC-I L chain, β2-microglobulin (β2m), governs complex stability. We reasoned that genetically converting β2m into an integral membrane protein should exert a marked stabilizing effect on the resulting MHC-I molecules and enhance vaccine efficacy. In the present study, we show that expression of membranal human β2m (hβ2m) in mouse RMA-S cells elevates MHC-I thermal stability. RMA-S transfectants bind an exogenous peptide at concentrations 104- to 106-fold lower than parental RMA-S, as detected by complex-specific Abs and by T cell activation. Moreover, saturation of the transfectants’ MHC-I by exogenous peptide occurs within 1 min, as compared with ∼1 h required for parental cells. At saturation, however, level of peptide bound by modified cells is only 3- to 5-fold higher. Expression of native hβ2m only results in marginal effect on the binding profile. Soluble β2m has no effect on the accelerated kinetics, but the kinetics of transfectants parallel that of parental cells in the presence of Abs to hβ2m. Ab inhibition and coimmunoprecipitation analyses suggest that both prolonged persistence of peptide-receptive H chain/β2m heterodimers and fast heterodimer formation via lateral diffusion may contribute to stabilization. In vivo, peptide-loaded transfectants are considerably superior to parental cells in suppressing tumor growth. Our findings support the role of an allosteric mechanism in determining ternary MHC-I complex stability and propose membranal β2m as a novel scaffold for CTL induction.