bluuebunny/crossref_metadata_2025 huggingface dataset:
Thy-1 Signaling in the Context of Costimulation Provided by Dendritic Cells Provides Signal 1 for T Cell Proliferation and Cytotoxic Effector Molecule Expression, but Fails to Trigger Delivery of the Lethal Hit
Authors: Haeryfar S. M. Mansour , Al-alwan Monther M. , Mader Jamie S. , Rowden Geoffry , West Kenneth A. , Hoskin David W.
Published: April 2014

Cross-linking of the GPI-anchored protein Thy-1 results in T cell proliferation and IL-2 synthesis. However, the exact function of Thy-1 in the process of T cell activation remains unknown, as does the effect of costimulation on Thy-1-driven T cell responses. In this study, we have investigated the ability of Thy-1 to substitute for traditional signal 1 in the context of costimulation provided by dendritic cells. Dendritic cells dramatically enhanced T cell proliferation and IL-2 synthesis in response to Thy-1 triggering by anti-Thy-1 mAb. This effect was not dependent on dendritic cell Fcγ receptors, but was a result of B7-mediated costimulation (signal 2). T cells were also activated when microbeads coated with a combination of anti-Thy-1 and anti-CD28 mAbs were used to supply signals 1 and 2, respectively. Thy-1-stimulated T cells adhere to target cells and express perforin, granzyme B, and Fas ligand, but fail to kill target cells due to an inability to reorganize their secretion machinery. Moreover, in contrast to TCR signaling, Thy-1 triggering failed to induce cytotoxicity in redirected lysis assays. We conclude that Thy-1 triggering can partially substitute for signal 1, which, in combination with a strong signal 2, leads to robust T cell proliferation, IL-2 synthesis, and cytotoxic effector molecule expression, but does not induce cytolytic function. The block at the level of cytotoxic effector function that results when T cells are activated in the absence of a classical, Ag-specific signal 1 may constitute a mechanism to ensure the specificity of CTL responses and prevent potentially harmful promiscuous cytotoxicity.
T Cell Glycolipid-Enriched Membrane Domains Are Constitutively Assembled as Membrane Patches That Translocate to Immune Synapses
Authors: Jordan Stephen , Rodgers William
Published: April 2014

In T cells, glycolipid-enriched membrane (GEM) domains, or lipid rafts, are assembled into immune synapses in response to Ag presentation. However, the properties of T cell GEM domains in the absence of stimulatory signals, such as their size and distribution in the plasma membrane, are less clear. To address this question, we used confocal microscopy to measure GEM domains in unstimulated T cells expressing a GEM-targeted green fluorescent protein molecule. Our experiments showed that the GEM domains were assembled into membrane patches that were micrometers in size, as evidenced by a specific enrichment of GEM-associated molecules and resistance of the patches to extraction by Triton X-100. However, treatment of cells with latrunculin B disrupted the patching of the GEM domains and their resistance to Triton X-100. Similarly, the patches were coenriched with F-actin, and actin occurred in the detergent-resistant GEM fraction of T cells. Live-cell imaging showed that the patches were mobile and underwent translocation in the plasma membrane to immune synapses in stimulated T cells. Targeting of GEM domains to immune synapses was found to be actin-dependent, and required phosphatidylinositol 3-kinase activity and myosin motor proteins. We conclude from our results that T cell GEM domains are constitutively assembled by the actin cytoskeleton into micrometer-sized membrane patches, and that GEM domains and the GEM-enriched patches can function as a vehicle for targeting molecules to immune synapses.
Inhibition of Constitutive NF-κB Activation in Mantle Cell Lymphoma B Cells Leads to Induction of Cell Cycle Arrest and Apoptosis
Authors: Pham Lan V. , Tamayo Archito T. , Yoshimura Linda C. , Lo Piao , Ford Richard J.
Published: April 2014

Constitutive activation of the NF-κB has been documented to be involved in the pathogenesis of many human malignancies, including hemopoietic neoplasms. In this study, we examined the status of NF-κB in two non-Hodgkin’s lymphoma cell lines derived from mantle cell lymphoma (MCL) samples and in patient MCL biopsy specimens by EMSA and confocal microscopic analysis. We observed that NF-κB is constitutively activated in both the MCL cell lines and in the MCL patient biopsy cells. Since NF-κB has been shown to play an important role in a variety of cellular processes, including cell cycle regulation and apoptosis, targeting the NF-κB pathways for therapy may represent a rational approach in this malignancy. In the MCL cell lines, inhibition of constitutive NF-κB by the proteasome inhibitor PS-341 or a specific pIκBα inhibitor, BAY 11-7082, led to cell cycle arrest in G1 and rapid induction of apoptosis. Apoptosis was associated with the down-regulation of bcl-2 family members bcl-xL and bfl/A1, and the activation of caspase 3, that mediates bcl-2 cleavage, resulting in the release of cytochrome c from the mitochondria. PS-341or BAY 11-induced G1 cell cycle arrest was associated with the inhibition of cyclin D1 expression, a molecular genetic marker of MCL. These studies suggest that constitutive NF-κB expression plays a key role in the growth and survival of MCL cells, and that PS-341 and BAY 11 may be useful therapeutic agents for MCL, a lymphoma that is refractory to most current chemotherapy regimens.
Rho Kinase Promotes Alloimmune Responses by Regulating the Proliferation and Structure of T Cells
Authors: Tharaux Pierre-Louis , Bukoski Richard C. , Rocha Paulo N. , Crowley Steven D. , Ruiz Phillip , Nataraj Chandra , Howell David N. , Kaibuchi Kozo , Spurney Robert F. , Coffman Thomas M.
Published: April 2014

Coordinated rearrangements of the actin-myosin cytoskeleton facilitate early and late events in T cell activation and signal transduction. As many important features of cell shape rearrangement involve small GTP-binding proteins, we examined the contribution of Rho kinase to the functions of mature T cells. Inhibitors of the Rho kinase pathway all had similar actions to inhibit the proliferation of primary lymphocyte cultures. Likewise, transfection of the human Jurkat T cell line with a dominant negative, kinase-defective mutant of Rho kinase diminished Jurkat cell proliferation. Furthermore, inhibition of Rho kinase substantially attenuated the program of cytokine gene expression that characterizes T cell activation, blocked actomyosin polymerization, and prevented aggregation of the TCR/CD3 complex colocalized with lipid rafts. These actions are relevant to immune responses in vivo, as treatment with a Rho kinase inhibitor considerably prolonged the survival of fully allogeneic heart transplants in mice and diminished intragraft expression of cytokine mRNAs. Thus, Rho GTPases acting through Rho kinase play a unique role in T cell activation during cellular immune responses by promoting structural rearrangements that are critical for T cell signaling.
Cutting Edge: IL-16/CD4 Preferentially Induces Th1 Cell Migration: Requirement of CCR5
Authors: Lynch Elizabeth A. , Heijens Claudia A. W. , Horst Noah F. , Center David M. , Cruikshank William W.
Published: April 2014

IL-16 binds to CD4 and induces a migratory response in CD4+ T cells. Although it has been assumed that CD4 is the sole receptor and that IL-16 induces a comparable migratory response in all CD4+ T cells, this has not been investigated. In this study, we determined that IL-16 preferentially induces a migratory response in Th1 cells. Because chemokine receptor CCR5 is expressed predominantly in Th1 cells and is physically associated with CD4, we investigated whether IL-16/CD4 stimulation was enhanced in the presence of CCR5. Using T cells from CCR5null mice, we determined that IL-16-induced migration was significantly greater in the presence of CCR5. The presence of CCR5 significantly increased IL-16 binding vs CD4 alone; however, IL-16 could not bind to CCR5 alone. Because CD4+CCR5+ cells are prevalent at sites of inflammation, this intimate functional relationship likely plays a pivotal role for the recruitment and activation of Th1 cells.
Cutting Edge: Long-Term B Cell Memory in Humans after Smallpox Vaccination
Authors: Crotty Shane , Felgner Phil , Davies Huw , Glidewell John , Villarreal Luis , Ahmed Rafi
Published: April 2014

Memory B cells are a central component of humoral immunity, and yet little is known about their longevity in humans. Immune memory after smallpox vaccination (DryVax) is a valuable benchmark for understanding the longevity of B cell memory in the absence of re-exposure to Ag. In this study, we demonstrate that smallpox vaccine-specific memory B cells last for >50 years in immunized individuals. Virus-specific memory B cells initially declined postimmunization, but then reached a plateau ∼10-fold lower than peak and were stably maintained for >50 years after vaccination at a frequency of ∼0.1% of total circulating IgG+ B cells. These persisting memory B cells were functional and able to mount a robust anamnestic Ab response upon revaccination. Additionally, virus-specific CD4+ T cells were detected decades after vaccination. These data show that immunological memory to DryVax vaccine is long-lived and may contribute to protection against smallpox.
Cutting Edge: Predetermined Avidity of Human CD8 T Cells Expanded on Calibrated MHC/Anti-CD28-Coated Microspheres
Authors: Walter Steffen , Herrgen Leah , Schoor Oliver , Jung Gundram , Wernet Dorothee , Bühring Hans-Jörg , Rammensee Hans-Georg , Stevanović Stefan
Published: April 2014

Cytotoxic CD8 T cells are key effectors in the immunotherapy of malignant and viral diseases. However, the lack of efficient methods for their in vitro priming and expansion has become a bottleneck to the development of vaccines and adoptive transfer strategies. Synthetic artificial APCs (aAPCs) are now emerging as an attractive tool for eliciting and expanding CTL responses. We show that, by controlling the MHC density on aAPCs, high- or low-avidity tumor-directed human CTL lines can be raised effectively in vitro if costimulation via CD28 and IL-12 is provided. Compared with low-avidity CTL lines, high-avidity CTLs need 100- to 1000-fold less peptide for activation, bind more MHC tetramers, and, as expected, are superior in recognizing tumor cell lines expressing Ag. We believe that the possibility to raise Ag-specific T cells with predetermined avidity will be crucial for the future use of aAPCs in immunotherapeutical settings.
Cutting Edge: γδ T Cells Provide Help to B Cells with Altered Clonotypes and Are Capable of Inducing Ig Gene Hypermutation
Authors: Zheng Biao , Marinova Ekaterina , Han Jin , Tan Tse-Hua , Han Shuhua
Published: April 2014

It has not been resolved whether γδ T cells can collaborate with germinal center B cells and support Ig hypermutation during an Ab response to a truly defined T-dependent Ag. In this study, we show that in the absence of αβ T cells, immunization with the well-defined T-dependent Ag, (4-hydroxy-3-nitrophenyl) acetyl (NP) conjugate, was able to induce Ig hypermutation. However, the clonotypes of B cells responding to NP were dramatically altered in TCR β−/− mice. Unlike B cells in wild-type mice that use canonical VDJ rearrangements, most NP-responding B cells in mutant mice use analog genes of the J558 gene family. In addition, the majority of anti-NP Abs produced in mutant mice use κL chain instead of λ1L chain, which dominates in mice of Ighb background. Thus, the B cell population that collaborates with γδ T cells is distinct from B cells interacting with conventional αβ Th cells.
Cutting Edge: Different Toll-Like Receptor Agonists Instruct Dendritic Cells to Induce Distinct Th Responses via Differential Modulation of Extracellular Signal-Regulated Kinase-Mitogen-Activated Protein Kinase and c-Fos
Authors: Agrawal Sudhanshu , Agrawal Anshu , Doughty Barbara , Gerwitz Andrew , Blenis John , Van Dyke Thomas , Pulendran Bali
Published: April 2014

Dendritic cells (DCs) are pivotal in determining the class of an adaptive immune response. However, the molecular mechanisms within DCs that determine this decision-making process are unknown. Here, we demonstrate that distinct Toll-like receptor (TLR) ligands instruct human DCs to induce distinct Th cell responses by differentially modulating mitogen-activated protein kinase signaling. Thus, Escherichia coli LPS and flagellin, which trigger TLR4 and TLR5, respectively, instruct DCs to stimulate Th1 responses via IL-12p70 production, which depends on the phosphorylation of p38 and c-Jun N-terminal kinase 1/2. In contrast, the TLR2 agonist, Pam3cys, and the Th2 stimulus, schistosome egg Ags: 1) barely induce IL-12p70; 2) stimulate sustained duration and magnitude of extracellular signal-regulated kinase 1/2 phosphorylation, which results in stabilization of the transcription factor c-Fos, a suppressor of IL-12; and 3) yield a Th2 bias. Thus, distinct TLR agonists differentially modulate extracellular signal-regulated kinase signaling, c-Fos activity, and cytokine responses in DCs to stimulate different Th responses.
Cutting Edge: Vasoactive Intestinal Peptide Acts as a Potent Suppressor of Inflammation In Vivo byTrans-Deactivating Chemokine Receptors
Authors: Grimm Michael C. , Newman Rosie , Hassim Zeenath , Cuan Natalia , Connor Susan J. , Le Yingying , Wang Ji Ming , Oppenheim Joost J. , Lloyd Andrew R.
Published: April 2014

Chemokines mediate trafficking of leukocytes to sites of inflammation and immune responses through activation of G protein-coupled receptors, which thereby provide appealing targets for novel anti-inflammatory agents. Vasoactive intestinal peptide (VIP) is an immunosuppressive neurotransmitter. We show that VIP inhibited the function of chemokine receptors on monocytes and CD4+ T lymphocytes, with impaired chemotaxis and calcium flux in response to the cognate chemokine ligands CXCL12, CCL3, CCL4, and CCL5. This was mediated by VIP receptor type 1 and was not caused by chemokine receptor internalization. However, VIP caused dose-dependent phosphorylation of the chemokine receptor CCR5. This trans-deactivation process was studied in a murine model of delayed-type hypersensitivity: continuous infusion of VIP resulted in significant abrogation of monocyte and lymphocyte infiltration. Circulating mononuclear cells from VIP-infused mice were unable to respond to chemokines. VIP may provide a novel approach to treatment of inflammatory diseases through inhibition of chemokine-dependent leukocyte recruitment.
Recipient T Cells Mediate Reperfusion Injury after Lung Transplantation in the Rat
Authors: de Perrot Marc , Young Kevin , Imai Yumiko , Liu Mingyao , Waddell Thomas K. , Fischer Stefan , Zhang Li , Keshavjee Shaf
Published: April 2014

Leukocytes have been implicated in ischemia-reperfusion (IR) injury of the lung, but the individual role of T cells has not been explored. Recent evidence in mice suggests that T cells may play a role in IR injury. Using a syngeneic (Lewis to Lewis) rat lung transplant model, we observed that recipient CD4+ T cells infiltrated lung grafts within 1 h of reperfusion and up-regulated the expression of CD25 over the ensuing 12 h. Nude rats (rnu/rnu) and heterozygous rats (rnu/+) were used to determine the role of T cells in IR injury. No significant difference in lung function was observed between nude and heterozygous recipient rats after 2 h of reperfusion. However, after 12 h of reperfusion, recipient nude rats had significantly higher oxygenation and lower peak airway pressure than recipient heterozygous rats. This was associated with significantly lower levels of IFN-γ in transplanted lung tissue of recipient nude rats. Reconstitution of recipient nude rats with T cells from heterozygous rats restored IR injury after 12 h of reperfusion. The effect of T cells was independent of neutrophil recruitment and activation in the transplanted lung. These results demonstrate that recipient T cells are activated and mediate IR injury during lung transplantation in rats.
The Protease Inhibitor Cystatin C Is Differentially Expressed among Dendritic Cell Populations, but Does Not Control Antigen Presentation
Authors: El-Sukkari Dima , Wilson Nicholas S. , Hakansson Katarina , Steptoe Raymond J. , Grubb Anders , Shortman Ken , Villadangos José A.
Published: April 2014

Dendritic cells (DC) undergo complex developmental changes during maturation. The MHC class II (MHC II) molecules of immature DC accumulate in intracellular compartments, but are expressed at high levels on the plasma membrane upon DC maturation. It has been proposed that the cysteine protease inhibitor cystatin C (CyC) plays a pivotal role in the control of this process by regulating the activity of cathepsin S, a protease involved in removal of the MHC II chaperone Ii, and hence in the formation of MHC II-peptide complexes. We show that CyC is differentially expressed by mouse DC populations. CD8+ DC, but not CD4+ or CD4−CD8− DC, synthesize CyC, which accumulates in MHC II+Lamp+ compartments. However, Ii processing and MHC II peptide loading proceeded similarly in all three DC populations. We then analyzed MHC II localization and Ag presentation in CD8+ DC, bone marrow-derived DC, and spleen-derived DC lines, from CyC-deficient mice. The absence of CyC did not affect the expression, the subcellular distribution, or the formation of peptide-loaded MHC II complexes in any of these DC types, nor the efficiency of presentation of exogenous Ags. Therefore, CyC is neither necessary nor sufficient to control MHC II expression and Ag presentation in DC. Our results also show that CyC expression can differ markedly between closely related cell types, suggesting the existence of hitherto unrecognized mechanisms of control of CyC expression.
CD4+CD25+ Regulatory T Cells Cure Murine Colitis: The Role of IL-10, TGF-β, and CTLA4
Authors: Liu Haiying , Hu Bin , Xu Damo , Liew Foo Y.
Published: April 2014

Regulatory T cells are critical in regulating the immune response, and therefore play an important role in the defense against infection and control of autoimmune diseases. However, a therapeutic role of regulatory T cells in an established disease has not been fully established. In this study, we provide direct evidence that CD4+CD25+ regulatory T cells can cure an established, severe, and progressive colitis. SCID mice developed severe colitis when adoptively transferred with naive CD4+CD25− T cells and infected with the protozoan parasite Leishmania major. The disease development can be completely halted and symptoms reversed, with a healthy outcome, by transferring freshly isolated or activated CD4+CD25+ T cells from syngeneic donors. The therapeutic effect of the regulatory T cells was completely blocked by treatment of the recipients with anti-IL-10R, anti-CTLA4, or anti-TGF-β Ab. However, the resurgence of colitis under these treatments was not accompanied by the reactivation of Th1 or Th2 response nor was it correlated to the parasite load. These results therefore demonstrate that CD4+CD25+ T cells are therapeutic and that the effect is mediated by both IL-10/TGF-β-dependent and independent mechanisms. Furthermore, colitis can manifest independent of Th1 and Th2 responses.
A Comparative Study between T Regulatory Type 1 and CD4+CD25+ T Cells in the Control of Inflammation
Authors: Foussat Arnaud , Cottrez Françoise , Brun Valérie , Fournier Nathalie , Breittmayer Jean-Philippe , Groux Hervé
Published: April 2014

There is now compelling evidence that CD4+CD25+ T cells play a major role in the maintenance of tolerance. Besides CD4+CD25+ T cells, different populations of regulatory CD4+ T cells secreting high amounts of IL-10 (T regulatory type 1 (Tr1)) or TGF-β (Th3) have also been described in in vivo models. In the lymphocyte transfer model of inflammatory bowel disease, we show here that the control of inflammation during the first weeks is not due to a complete inhibition of differentiation of aggressive proinflammatory T cells, but is the result of a balance between proinflammatory and Tr cells. We also show that in the first weeks continuous IL-10 secretion was required to actively control inflammation. Indeed, treatment with anti-IL-10R Abs 3 wk after the start of the experiment completely reversed the protective effect of Tr cells. IL-10 secretion and control of inflammation could be provided by late injection of Tr1 cells that efficiently cure ongoing inflammatory responses in two different models of inflammation. In contrast, inflammation was not controlled when high numbers of CD4+CD45RBlow or CD4+CD25+ T cells were injected as early as 1 wk after the start of the experiment. These results confirm in vitro studies showing that CD4+CD45RBlow do not contain high IL-10-producing cells and suggest that CD4+CD45RBlow Tr cells maintain tolerance in vivo, in part indirectly, through the differentiation of IL-10-secreting Tr1 cells.
Uncoupling between Immunological Synapse Formation and Functional Outcome in Human γδ T Lymphocytes
Authors: Favier Benoit , Espinosa Eric , Tabiasco Julie , Dos Santos Cédric , Bonneville Marc , Valitutti Salvatore , Fournié Jean-Jacques
Published: April 2014

Human T lymphocytes expressing the Vγ9Vδ2 TCR recognize non-peptidic Ags, referred to as phosphoantigens, produced by microbial pathogens and by human tumor cells. Here we show that γδ T cells establish a mature immunological synapse (IS) with the myelomonocytic THP-1 tumoral cell line. This synapse is characterized by an enrichment for phosphotyrosine, CD2, and γδ TCR together with the exclusion of CD45. The CD94 and NKG2D receptors are also recruited to the signaling area, while the C-lectin-like activation marker CD69 segregates out of the synapse. γδ T cell conjugation to THP-1 increases upon stimulation by soluble phosphoantigen, is paralleled by the metabolic activation of γδ T cells and leads to cytokine production. Molecular segregation of the above molecules also occurs at the γδ T cell/THP-1 interface in the absence of exogenously added phosphoantigen, although it does not result in intracellular signaling and cytokine production under these conditions. Hence the molecular interactions at the γδ T cell-THP-1 target cell interface are sufficient to induce the formation of an IS, but cytokine production requires the full engagement of γδ TCR by a strong agonist. Thus in γδ T cells, formation of the IS is uncoupled from its functional outcome.
Reprogramming of IL-10 Activity and Signaling by IFN-γ
Authors: Herrero Carmen , Hu Xiaoyu , Li Wai Ping , Samuels Stuart , Sharif M. Nusrat , Kotenko Sergei , Ivashkiv Lionel B.
Published: April 2014

One important mechanism of cross-regulation by opposing cytokines is inhibition of signal transduction, including inhibition of Janus kinase-STAT signaling by suppressors of cytokine signaling. We investigated whether IFN-γ, a major activator of macrophages, inhibited the activity of IL-10, an important deactivator. Preactivation of macrophages with IFN-γ inhibited two key anti-inflammatory functions of IL-10, the suppression of cytokine production and of MHC class II expression. Gene expression profiling showed that IFN-γ broadly suppressed the ability of IL-10 to induce or repress gene expression. Although IFN-γ induced expression of suppressor of cytokine signaling proteins, IL-10 signal transduction was not suppressed and IL-10 activation of Janus kinases and Stat3 was preserved. Instead, IFN-γ switched the balance of IL-10 STAT activation from Stat3 to Stat1, with concomitant activation of inflammatory gene expression. IL-10 activation of Stat1 required the simultaneous presence of IFN-γ. These results demonstrate that IFN-γ operates a switch that rapidly regulates STAT activation by IL-10 and alters macrophage responses to IL-10. Dynamic regulation of the activation of different STATs by the same cytokine provides a mechanism by which cells can integrate and balance signals delivered by opposing cytokines, and extends our understanding of cross-regulation by opposing cytokines to include reprogramming of signaling and alteration of function.
Loss of Tolerance and Autoimmunity Affecting Multiple Organs inSTAT5A/5B-Deficient Mice
Authors: Snow Jonathan W. , Abraham Ninan , Ma Melissa C. , Herndier Brian G. , Pastuszak Alexander W. , Goldsmith Mark A.
Published: April 2014

STAT5 has previously been reported to be dispensable for the maintenance of tolerance in vivo. However, in examining hemopoiesis in mice lacking both isoforms of STAT5, STAT5A, and STAT5B, we noted that a subset of these mice demonstrated dramatic alterations in several bone marrow progenitor populations concomitant with lymphocytic infiltration of the bone marrow. In addition, cellular infiltration affecting the colon, liver, and kidney was observed in these mice. Survival analysis revealed that STAT5A/5B−/− mice exhibited early death. The increased mortality and the pathology affecting multiple organs observed in these mice were abrogated on the recombination-activating gene 1−/− background. In light of the similarities between STAT5A/5B-deficient mice and mice unable to signal through the IL-2R, we hypothesized that the tolerizing role of STAT5A/5B was triggered via activation of the IL-2R. In agreement with this, we found that IL-2Rβ chain-deficient mice exhibited similar hemopoietic abnormalities. Because IL-2 signaling is thought to contribute to tolerance through maintenance of a CD4+CD25+ regulatory T cell population, we examined these cells and observed a numerical reduction in STAT5A/5B−/− mice along with a higher rate of apoptosis. These data provide strong evidence for a requirement for STAT5 in the maintenance of tolerance in vivo.
IL-2 Intratumoral Immunotherapy Enhances CD8+ T Cells That Mediate Destruction of Tumor Cells and Tumor-Associated Vasculature: A Novel Mechanism for IL-2
Authors: Jackaman Connie , Bundell Christine S. , Kinnear Beverley F. , Smith Alison M. , Filion Pierre , van Hagen Deborah , Robinson Bruce W. S. , Nelson Delia J.
Published: April 2014

Therapeutic use of IL-2 can generate antitumor immunity; however, a variety of different mechanisms have been reported. We injected IL-2 intratumorally (i.t.) at different stages of growth, using our unique murine model of mesothelioma (AE17; and AE17 transfected with secretory OVA (AE17-sOVA)), and systematically analyzed real-time events as they occurred in vivo. The majority of mice with small tumors when treatment commenced displayed complete tumor regression, remained tumor free for >2 mo, and survived rechallenge with AE17 tumor cells. However, mice with large tumors at the start of treatment failed to respond. Timing experiments showed that IL-2-mediated responses were dependent upon tumor size, not on the duration of disease. Although i.t. IL-2 did not alter tumor Ag presentation in draining lymph nodes, it did enhance a previously primed, endogenous, tumor-specific in vivo CTL response that coincided with regressing tumors. Both CD4+ and CD8+ cells were required for IL-2-mediated tumor eradication, because IL-2 therapy failed in CD4+-depleted, CD8+-depleted, and both CD4+- and CD8+-depleted C57BL/6J animals. Tumor-infiltrating CD8+ T cells, but not CD4+ T cells, increased in association with a marked reduction in tumor-associated vascularity. Destruction of blood vessels required CD8+ T cells, because this did not occur in nude mice or in CD8+-depleted C57BL/6J mice. These results show that repeated doses of i.t. (but not systemic) IL-2 mediates tumor regression via an enhanced endogenous tumor-specific CTL response concomitant with reduced vasculature, thereby demonstrating a novel mechanism for IL-2 activity.
DQ 65–79, A Peptide Derived from HLA Class II, Mimics p21 to Block T Cell Proliferation
Authors: Dong Chen , Lyu Shu-Chen , Krensky Alan M. , Clayberger Carol
Published: April 2014

DQ 65–79, a peptide derived from residues 65–79 of the α-chain HLA class II molecule DQA03011, blocks T cell proliferation and induces T cell apoptosis. Using a yeast two-hybrid assay, we previously identified proliferating cell nuclear Ag (PCNA) as an intracellular ligand for DQ 65–79. In this study, we show that three regions of PCNA, residues 81–100, 121–140, and 241–261, interact with DQ 65–79. Residues 241–261 of PCNA also interact with the C terminus (residues 139–160) of the cell cycle regulator, p21, suggesting that DQ 65–79 and p21 might function similarly. We show here that DQ 65–79 competitively inhibits binding of p21 to PCNA and that both DQ 65–79 and p21 139–160 induce T cell apoptosis, suggesting that DQ 65–79 and p21 act similarly to inhibit cell growth.
CD8+ T Lymphocytes Regulating Th2 Pathology Escape Neonatal Tolerization
Authors: Adams Brigitte , Nagy Nathalie , Paulart Frédéric , Vanderhaeghen Marie-Line , Goldman Michel , Flamand Véronique
Published: April 2014

Transplantation tolerance induced by neonatal injection of semiallogeneic spleen cells is associated in several strain combinations with a pathological syndrome caused by Th2 differentiation of donor-specific CD4+ T lymphocytes. We investigated the role of host CD8+ T cells in the regulation of this Th2 pathology. IgE serum levels and eosinophilia significantly increased in BALB/c mice neonatally injected with (A/J × BALB/c)F1 spleen cells when CD8+ T cells were depleted by administration of anti-CD8 mAb or when β2-microglobulin-deficient mice were used as recipients. In parallel, increased serum levels of IL-5 and IL-13 were measured in blood of tolerant CD8+ T cell-deficient mice. Whereas neonatally injected mice were unable to generate anti-donor cytotoxic effectors, their CD8+ T cells were as efficient as control CD8+ T cells in reducing the severity of Th2 pathology and in restoring donor-specific cytotoxicity in vitro after in vivo transfer in β2-microglobulin-deficient mice. Likewise, CD8+ T cells from control and tolerant mice equally down-regulated the production of Th2 cytokines by donor-specific CD4+ T cells in vitro. The regulatory activity of CD8+ T cells depended on their secretion of IFN-γ for the control of IL-5 production but not for IL-4 or IL-13. Finally, we found that CD8+ T cells from 3-day-old mice were already able to down-regulate IL-4, IL-5, and IL-13 production by CD4+ T cells. We conclude that regulatory CD8+ T cells controlling Th2 responses are functional in early life and escape neonatal tolerization.
CD8α+ and CD11b+ Dendritic Cell-Restricted MHC Class II Controls Th1 CD4+ T Cell Immunity
Authors: Lemos Maria P. , Fan Lian , Lo David , Laufer Terri M.
Published: April 2014

The activation, proliferation, differentiation, and trafficking of CD4 T cells is central to the development of type I immune responses. MHC class II (MHCII)-bearing dendritic cells (DCs) initiate CD4+ T cell priming, but the relative contributions of other MHCII+ APCs to the complete Th1 immune response is less clear. To address this question, we examined Th1 immunity in a mouse model in which I-Aβb expression was targeted specifically to the DCs of I-Aβb−/− mice. MHCII expression is reconstituted in CD11b+ and CD8α+ DCs, but other DC subtypes, macrophages, B cells, and parenchymal cells lack of expression of the I-Aβb chain. Presentation of both peptide and protein Ags by these DC subsets is sufficient for Th1 differentiation of Ag-specific CD4+ T cells in vivo. Thus, Ag-specific CD4+ T cells are primed to produce Th1 cytokines IL-2 and IFN-γ. Additionally, proliferation, migration out of lymphoid organs, and the number of effector CD4+ T cells are appropriately regulated. However, class II-negative B cells cannot receive help and Ag-specific IgG is not produced, confirming the critical MHCII requirement at this stage. These findings indicate that DCs are not only key initiators of the primary response, but provide all of the necessary cognate interactions to control CD4+ T cell fate during the primary immune response.
Differential Roles for IL-15R α-Chain in NK Cell Development and Ly-49 Induction
Authors: Kawamura Toshihiko , Koka Rima , Ma Averil , Kumar Vinay
Published: April 2014

IL-15Rα-deficient (IL-15Rα−/−) mice lack NK cells. However, when bone marrow (BM) progenitors from IL-15Rα−/− mice were cultured with IL-7, stem cell factor and flt3 ligand, followed by IL-15, they were able to differentiate into functional NK cells, indicating that IL-15Rα is not critical for NK cell development. Whereas NK cells generated in vitro from IL-15Rα−/− BM progenitors expressed CD94/NKG2, they failed to express Ly-49 receptors. In keeping with this, when IL-15Rα−/− BM cells were transferred into wild type recipients, they gave rise to NK cells in vivo, but with greatly reduced expression of Ly-49 receptors. Furthermore, the small numbers of NK cells found in IL-15−/− as well as IL-15Rα−/− but not flt3 ligand−/− mice expressed much lower levels of Ly-49 receptors than those from wild type mice. These results indicate a novel role for IL-15Rα-chain in Ly-49 induction on developing NK cells.
Adiponectin, a Fat Cell Product, Influences the Earliest Lymphocyte Precursors in Bone Marrow Cultures by Activation of the Cyclooxygenase-Prostaglandin Pathway in Stromal Cells
Authors: Yokota Takafumi , Meka C. S. Reddy , Kouro Taku , Medina Kay L. , Igarashi Hideya , Takahashi Masahiko , Oritani Kenji , Funahashi Tohru , Tomiyama Yoshiaki , Matsuzawa Yuji , Kincade Paul W.
Published: April 2014

Adiponectin, an adipocyte-derived hormone, is attracting considerable interest as a potential drug for diabetes and obesity. Originally cloned from human s.c. fat, the protein is also found in bone marrow fat cells and has an inhibitory effect on adipocyte differentiation. The aim of the present study is to explore possible influences on lymphohematopoiesis. Recombinant adiponectin strongly inhibited B lymphopoiesis in long-term bone marrow cultures, but only when stromal cells were present and only when cultures were initiated with the earliest category of lymphocyte precursors. Cyclooxygenase inhibitors abrogated the response of early lymphoid progenitors to adiponectin in stromal cell-containing cultures. Furthermore, PGE2, a major product of cyclooxygenase-2 activity, had a direct inhibitory influence on purified hematopoietic cells, suggesting a possible mechanism of adiponectin action in culture. In contrast to lymphopoiesis, myelopoiesis was slightly enhanced in adiponectin-treated bone marrow cultures, and even when cultures were initiated with single lymphomyeloid progenitors. Finally, human B lymphopoiesis was also sensitive to adiponectin in stromal cell cocultures. These results suggest that adiponectin can negatively and selectively influence lymphopoiesis through induction of PG synthesis. They also indicate ways that adipocytes in bone marrow can contribute to regulation of blood cell formation.
Modulation ofO-Glycans andN-Glycans on Murine CD8 T Cells Fails to Alter Annexin V Ligand Induction by Galectin 1
Authors: Carlow Douglas A. , Williams Michael J. , Ziltener Hermann J.
Published: April 2014

Thymic negative selection and contraction of responding T cell oligoclones after infection represent important cell ablation processes required for maintaining T cell homeostasis. It has been proposed that galectin 1 contributes to these processes through interaction with lactosyl sequences principally on cell surface glycoproteins bearing core 2 (C2GnT1)-branched O-glycans. According to this model, specific T cell surface proteins cross-linked by galectin 1 induce signaling, ligand redistribution, and apoptosis in both immature thymocytes and activated T cells. The influence of lactosyl residues contained in branched O-glycans or complex N-glycans on galectin 1 binding and induction of annexin V ligand in murine CD8 T cells was assessed. Neither galectin binding nor galectin-induced expression of annexin V ligand was perturbed under conditions in which: 1) C2GnT1 activity was differentially induced by CD8 T cell activation/culture with IL-2 vs IL-4; 2) activated CD8+ T cells lacked C2GnT1 expression; or 3) complex N-glycan formation was blocked by swainsonine. The maintenance of galectin 1 binding and induced annexin V expression under conditions that alter lactosamine abundance on O- or complex N-glycans suggest that galectin 1-mediated apoptosis is neither a simple function of fluctuating C2GnT1 activity nor a general C2GnT1-dependent mechanism underlying contraction of CD8 T cells subsequent to activation.
Intracellular Thiols Contribute to Th2 Function via a Positive Role in IL-4 Production
Authors: Monick Martha M. , Samavati Lobelia , Butler Noah S. , Mohning Michael , Powers Linda S. , Yarovinsky Timur , Spitz Douglas R. , Hunninghake Gary W.
Published: April 2014

A number of lung diseases, including many interstitial lung diseases and HIV infection, are associated with decreases in intracellular thiols. Altered Th1/Th2 T cell balance has also been associated with disease progression in many of the same diseases. IFN-γ and IL-4 are critical effector cytokines of Th1 and Th2 cells, respectively. To determine the effect of thiols on the production of IFN-γ and IL-4 by splenocytes, cells were incubated in the presence and the absence of N-acetylcysteine (NAC) and stimulated with αCD3 or αCD3 and IL-12. Augmenting intracellular soluble thiol pools (∼2-fold) with 15 mM NAC blocked induction of IFN-γ and increased production of IL-4 without causing significant changes in intracellular glutathione levels. The effect of NAC on IL-4 production was not linked to an increase in STAT6 phosphorylation, as STAT6 levels were decreased, nor did the increase in IL-4 occur with purified CD4 cells. We found that NAC increased splenocyte IL-4 production via an effect on APCs. We also found that NAC increased two IL-4 relevant transcription factors (AP-1) and NFATc. These studies suggest that increasing intracellular reduced thiol pools decreases IL-12 signaling and IFN-γ production, while increasing IL-4 production. The sum of these effects may contribute to alterations in the balance between Th1 and Th2 responses in lung diseases associated alterations in intracellular thiol pools.
High Avidity Antigen-Specific CTL Identified by CD8-Independent Tetramer Staining
Authors: Choi Ed Man-Lik , Chen Ji-Li , Wooldridge Linda , Salio Mariolina , Lissina Anna , Lissin Nikolai , Hermans Ian F. , Silk Jonathan D. , Mirza Fareed , Palmowski Michael J. , Dunbar P. Rod , Jakobsen Bent K. , Sewell Andy K. , Cerundolo Vincenzo
Published: April 2014

Tetrameric MHC/peptide complexes are important tools for enumerating, phenotyping, and rapidly cloning Ag-specific T cells. It remains however unclear whether they can reliably distinguish between high and low avidity T cell clones. In this report, tetramers with mutated CD8 binding site selectively stain higher avidity human and murine CTL capable of recognizing physiological levels of Ag. Furthermore, we demonstrate that CD8 binding significantly enhances the avidity as well as the stability of interactions between CTL and cognate tetramers. The use of CD8-null tetramers to identify high avidity CTL provides a tool to compare vaccination strategies for their ability to enhance the frequency of high avidity CTL. Using this technique, we show that DNA priming and vaccinia boosting of HHD A2 transgenic mice fail to selectively expand large numbers of high avidity NY-ESO-1157–165-specific CTL, possibly due to the large amounts of antigenic peptide delivered by the vaccinia virus. Furthermore, development of a protocol for rapid identification of high avidity human and murine T cells using tetramers with impaired CD8 binding provides an opportunity not only to monitor expansion of high avidity T cell responses ex vivo, but also to sort high avidity CTL clones for adoptive T cell transfer therapy.
Polymorphonuclear Granulocytes Induce Antibody-Dependent Apoptosis in Human Breast Cancer Cells
Authors: Stockmeyer Bernhard , Beyer Thomas , Neuhuber Winfried , Repp Roland , Kalden Joachim R. , Valerius Thomas , Herrmann Martin
Published: April 2014

Recent studies in HER-2/neu-targeted immunotherapy demonstrated that polymorphonuclear neutrophils (PMN) mediated Ab-dependent cellular cytotoxicity against HER-2/neu-positive breast cancer cell lines. However, the mechanism of cell death remained unclear. We used several assays to analyze the induction of apoptosis in the breast cancer cell line SK-BR-3 via PMN-dependent Ab-dependent cellular cytotoxicity. In the presence of the HER-2/neu Ab 520C9 and PMN from healthy donors, apoptosis occurred as detected by annexin V binding and disappearance of euploid SK-BR-3 nuclei, which can be differentiated from PMN nuclei by their increased DNA contents. Apoptosis induction was observed with E:T cell ratios as low as 10:1. Laser scanning fluorescence microscopy of TUNEL tumor cells or staining for cleaved cytokeratin-18 further confirmed apoptosis of the SK-BR-3 breast cancer cells. Killing via 520C9 was dependent on the interaction with FcR on PMN, because 1) F(ab′)2 fragments of 520C9 mediated no cytotoxicity, 2) target cell death was influenced by a biallelic polymorphism of FcγRIIa on the effector cells, and 3) a bispecific Ab against HER-2/neu and the IgA receptor (FcαRI) expressed on effector cells significantly induced apoptosis. Thus, PMN induce Ab-dependent apoptosis against human breast cancer cells targeted with HER-2/neu-directed mAbs or FcR directed bispecific Abs.
Distinct Osteoclast Precursors in the Bone Marrow and Extramedullary Organs Characterized by Responsiveness to Toll-Like Receptor Ligands and TNF-α
Authors: Hayashi Shin-Ichi , Yamada Takayuki , Tsuneto Motokazu , Yamane Toshiyuki , Takahashi Masayuki , Shultz Leonard D. , Yamazaki Hidetoshi
Published: April 2014

Osteoclasts are derived from hemopoietic stem cells and play critical roles in bone resorption and remodeling. Multinucleated osteoclasts are attached tightly to bone matrix, whereas precursor cells with the potential to differentiate into osteoclasts in culture are widely distributed. In this study, we assessed the characteristics of osteoclast precursors in bone marrow (BM) and in extramedullary organs as indicated by their responsiveness to ligands for Toll-like receptors (TLRs) and to TNF-α. Development of osteoclasts from precursor cells in the BM was inhibited by CpG oligonucleotides, a ligand for TLR9, but not by LPS, a ligand for TLR4. BM osteoclasts were induced by TNF-α as well as receptor activator of NF-κB ligand in the presence of M-CSF. Splenic osteoclast precursors, even in osteoclast-deficient osteopetrotic mice, differentiated into mature osteoclasts following exposure to TNF-α or receptor activator of NF-κB ligand. However, splenic osteoclastogenesis was inhibited by both LPS and CpG. Osteoclastogenesis from peritoneal precursors was inhibited by not only these TLR ligands but also TNF-α. The effects of peptidoglycan, a ligand for TLR2, were similar to those of LPS. BM cells precultured with M-CSF were characterized with intermediate characteristics between those of splenic and peritoneal cavity precursors. Taken together, these findings demonstrate that osteoclast precursors are not identical in the tissues examined. To address the question of why mature osteoclasts occur only in association with bone, we may characterize not only the microenvironment for osteoclastogenesis, but also the osteoclast precursor itself in intramedullary and extramedullary tissues.
NKT Cells Enhance CD4+ and CD8+ T Cell Responses to Soluble Antigen In Vivo through Direct Interaction with Dendritic Cells
Authors: Hermans Ian F. , Silk Jonathan D. , Gileadi Uzi , Salio Mariolina , Mathew Bini , Ritter Gerd , Schmidt Richard , Harris Adrian L. , Old Lloyd , Cerundolo Vincenzo
Published: April 2014

Modification in the function of dendritic cells (DC), such as that achieved by microbial stimuli or T cell help, plays a critical role in determining the quality and size of adaptive responses to Ag. NKT cells bearing an invariant TCR (iNKT cells) restricted by nonpolymorphic CD1d molecules may constitute a readily available source of help for DC. We therefore examined T cell responses to i.v. injection of soluble Ag in the presence or the absence of iNKT cell stimulation with the CD1d-binding glycolipid α-galactosylceramide (α-GalCer). Considerably enhanced CD4+ and CD8+ T cell responses were observed when α-GalCer was administered at the same time as or close to OVA injection. This enhancement was dependent on the involvement of iNKT cells and CD1d molecules and required CD40 signaling. Studies in IFN-γR−/− mice indicated that IFN-γ was not required for the adjuvant effect of α-GalCer. Consistent with this result, enhanced T cell responses were observed using OCH, an analog of α-GalCer with a truncated sphingosine chain and a reduced capacity to induce IFN-γ. Splenic DC from α-GalCer-treated animals expressed high levels of costimulatory molecules, suggesting maturation in response to iNKT cell activation. Furthermore, studies with cultured DC indicated that potentiation of T cell responses required presentation of specific peptide and α-GalCer by the same DC, implying conditioning of DC by iNKT cells. The iNKT-enhanced T cell responses resisted challenge with OVA-expressing tumors, whereas responses induced in the absence of iNKT stimulation did not. Thus, iNKT cells exert a significant influence on the efficacy of immune responses to soluble Ag by modulating DC function.
Cyclopentenone Prostaglandins Induce Lymphocyte Apoptosis by Activating the Mitochondrial Apoptosis Pathway Independent of External Death Receptor Signaling
Authors: Nencioni Alessio , Lauber Kirsten , Grünebach Frank , Van Parijs Luk , Denzlinger Claudio , Wesselborg Sebastian , Brossart Peter
Published: April 2014

15-Deoxy-Δ12,14-PGJ2 (15d-PGJ2) is a naturally occurring cyclopentenone metabolite of PGD2 that possesses both peroxisome proliferator-activated receptor γ (PPAR-γ)-dependent and PPAR-γ-independent anti-inflammatory properties. Recent studies suggest that cyclopentenone PGs may play a role in the down-regulation of inflammation-induced immune responses. In this study, we report that 15d-PGJ2 as well as synthetic PPAR-γ agonists inhibit lymphocyte proliferation. However, only 15d-PGJ2, but not the specific PPAR-γ activators, induce lymphocyte apoptosis. We found that blocking of the death receptor pathway in Fas-associated death domain−/− or caspase-8−/− Jurkat T cells has no effect on apoptosis induction by 15d-PGJ2. Conversely, overexpression of Bcl-2 or Bcl-xL completely inhibits the initiation of apoptosis, indicating that 15d-PGJ2-mediated apoptosis involves activation of the mitochondrial pathway. In line with these results, 15d-PGJ2 induces mitochondria disassemblage as demonstrated by dissipation of mitochondrial transmembrane potential (Δψm) and cytochrome c release. Both of these events are partially inhibited by the broad spectrum caspase inhibitor benzyloxycarbonil-Val-Ala-Asp-fluoromethylketone, suggesting that caspase activation may amplify the mitochondrial alterations initiated by 15d-PGJ2. We also demonstrate that 15d-PGJ2 potently stimulates reactive oxygen species production in Jurkat T cells, and Δψm loss induced by 15d-PGJ2 is prevented by the reactive oxygen species scavenger N-acetyl-l-cysteine. In conclusion, our data indicate that cyclopentenone PGs like 15d-PGJ2 may modulate immune responses even independent of PPAR-γ by activating the mitochondrial apoptosis pathway in lymphocytes in the absence of external death receptor signaling.