bluuebunny/crossref_metadata_2025 huggingface dataset:
Cutting Edge: Human β Defensin 3—A Novel Antagonist of the HIV-1 Coreceptor CXCR4
Authors: Feng Zhimin , Dubyak George R. , Lederman Michael M. , Weinberg Aaron
Published: April 2014

Previously, we showed that human epithelial cell-derived β-defensins (hBD)-2 and -3 block HIV-1 replication via a direct interaction with virions and through modulation of the CXCR4 coreceptor on immunocompetent cells. In the present study, we show that hBD-3 promotes directly the internalization of CXCR4 yet does not induce calcium flux, ERK (ERK-1/2) phosphorylation, or chemotaxis. hBD-3 competes with stromal-derived factor 1 (SDF-1), the natural ligand for CXCR4, for cellular binding and blocks SDF-1-induced calcium flux, ERK-1/2 phosphorylation, and chemotaxis, without effects on other G protein-coupled receptors. The novel activity of this endogenous CXCR4 antagonist may provide a new strategy for HIV therapies or immunomodulation. Moreover, since the SDF-1/CXCR4 axis plays an important role in hemopoiesis, neurogenesis, cardiogenesis, and angiogenesis, endogenous agents such as hBD-3 or its derivatives offer a new paradigm in immunoregulatory therapeutics and provide the opportunity to enhance future drug design.
Disruption of Cyclin D3 Blocks Proliferation of Normal B-1a Cells, but Loss of Cyclin D3 Is Compensated by Cyclin D2 in Cyclin D3-Deficient Mice
Authors: Mataraza Jennifer M. , Tumang Joseph R. , Gumina Maria R. , Gurdak Sean M. , Rothstein Thomas L. , Chiles Thomas C.
Published: April 2014

Peritoneal B-1a cells differ from splenic B-2 cells in the molecular mechanisms that control G0-S progression. In contrast to B-2 cells, cyclin D2 is up-regulated in a rapid and transient manner in phorbol ester (PMA)-stimulated B-1a cells, whereas cyclin D3 does not accumulate until late G1 phase. This nonoverlapping expression of cyclins D2 and D3 suggests distinct functions for these proteins in B-1a cells. To investigate the contribution of cyclin D3 in the proliferation of B-1a cells, we transduced p16INK4a peptidyl mimetics (TAT-p16) into B-1a cells before cyclin D3 induction to specifically block cyclin D3-cyclin-dependent kinase 4/6 assembly. TAT-p16 inhibited DNA synthesis in B-1a cells stimulated by PMA, CD40L, or LPS as well as endogenous pRb phosphorylation by cyclin D-cyclin-dependent kinase 4/6. Unexpectedly, however, cyclin D3-deficient B-1a cells proliferated in a manner similar to wild-type B-1a cells following PMA or LPS stimulation. This was due, at least in part, to the compensatory sustained accumulation of cyclin D2 throughout G0-S progression. Taken together, experiments in which cyclin D3 was inhibited in real time demonstrate the key role this cyclin plays in normal B-1a cell mitogenesis, whereas experiments with cyclin D3-deficient B-1a cells show that cyclin D2 can compensate for cyclin D3 loss in mutant mice.
Thymic Alterations in EphA4-Deficient Mice
Authors: Muñoz Juan J. , Alfaro David , García-Ceca Javier , Alonso-C Luis M. , Jiménez Eva , Zapata Agustín
Published: April 2014

In the present work, we have demonstrated in vivo an altered maturation of the thymic epithelium that results in defective T cell development which increases with age, in the thymus of Eph A4-deficient mice. The deficient thymi are hypocellular and show decreased proportions of double-positive (CD4+CD8+) cells which reach minimal numbers in 4-wk-old thymi. The EphA4 −/− phenotype correlates with an early block of T cell precursor differentiation that results in accumulation of CD44−CD25+ triple-negative cells and, sometimes, of CD44+CD25− triple-negative thymocytes as well as with increased numbers of apoptotic cells and an important reduction in the numbers of cycling thymocytes. Various approaches support a key role of the thymic epithelial cells in the observed phenotype. Thymic cytoarchitecture undergoes profound changes earlier than those found in the thymocyte maturation. Thymic cortex is extremely reduced and consists of densely packed thymic epithelial cells. Presumably the lack of forward Eph A4 signaling in the Eph A4 −/− epithelial cells affects their development and finally results in altered T cell development.
Inhibition of Th2-Mediated Allergic Airway Inflammatory Disease by CD137 Costimulation
Authors: Sun Yonglian , Blink Sarah E. , Liu Wenhua , Lee Youjin , Chen Bohao , Solway Julian , Weinstock Joel , Chen Lieping , Fu Yang-Xin
Published: April 2014

The engagement of CD137 (4-1BB), an inducible T cell costimulatory receptor and member of the TNF receptor superfamily, by agonistic Abs can promote strong tumor and viral immunity mediated by CD8+ T cells and stimulate IFN-γ production. However, its role in Th2-mediated immune responses has not been well defined. To address this issue, we studied the function of CD137 engagement using an allergic airway disease model in which the mice were sensitized with inactivated Schistosoma mansoni eggs followed by S. mansoni egg Ag challenge directly in the airways and Th1/2 cytokine production was monitored. Interestingly, treatment of C57BL/6 mice with agonistic anti-CD137 (2A) during sensitization completely prevents allergic airway inflammation, as shown by a clear inhibition of T cell and eosinophil infiltration into the lung tissue and airways, accompanied by diminished Th2 cytokine production and reduced serum IgE levels, as well as a reduction of airway hyperresponsiveness. At various time points after immunization, restimulated splenocytes from 2A-treated mice displayed reduced proliferation and Th2 cytokine production. In accordance with this, agonistic Ab to CD137 can directly coinhibit Th2 responses in vitro although it costimulates Th1 responses. CD137-mediated suppression of Th2 response is independent of IFN-γ and T regulatory cells. Our study has identified a novel pathway to inhibit Th2 responses in a CD137-dependent fashion.
Mechanism of IFN-β-Mediated Inhibition of IL-8 Gene Expression in Astroglioma Cells
Authors: Nozell Susan , Laver Travis , Patel Kiran , Benveniste Etty N.
Published: April 2014

IL-8 is a chemokine that recruits migrating neutrophils and leukocytes to areas of inflammation. In noninflamed tissue, IL-8 expression is low but can be rapidly induced by proinflammatory cytokines. Typically, inflammation and transient IL-8 expression are beneficial. However, some diseases are characterized by excessive inflammation and high levels of IL-8. Previous studies have shown that IFN-β can inhibit the expression of IL-8, although the mechanism is unknown. Using chromatin immunoprecipitation assays, we define the IL-8 transcriptional program in the absence or presence of inducing stimuli and/or inhibition by IFN-β. In the absence of stimuli, the IL-8 promoter is acetylated but negatively regulated by corepressor proteins. Upon PMA stimulation, the levels of these corepressors are reduced and the promoter is rapidly bound and activated by transcription factors, including NF-κB p65, C/EBPβ, and c-Fos. In addition, RNA polymerase II is recruited to the IL-8 promoter to initiate transcription. However, in the presence of both PMA and IFN-β, there are diminished levels of histone acetylation, reduced levels of transcription factors such as NF-κB p65 and RNA polymerase II, and an increased presence of corepressor proteins such as histone deacetylases 1 and 3 and silencing mediator of retinoic acid and thyroid hormone receptors. IFN-γ-inducible protein-10 and MCP-1 genes, also regulated by NF-κB, are unaffected by IFN-β, and IFN-β does not prevent the activation, nuclear migration, or binding of NF-κB p65 to the κB element of the IFN-γ-inducible protein-10 promoter. As such, these data show that the inhibitory effects of IFN-β are specific to the IL-8 promoter.
Stimulation History Dictates Memory CD8 T Cell Phenotype: Implications for Prime-Boost Vaccination
Authors: Masopust David , Ha Sang-Jun , Vezys Vaiva , Ahmed Rafi
Published: April 2014

Heterologous prime-boost vaccination results in increased frequencies of memory T cells. Although these quantitative effects of reexposure to Ag are well documented, little is known about the impact of boosting on the functional qualities of memory T cells. To address this critical issue, we have used three different types of immunization regimens and examined how boosting effects the function and anatomic location of memory CD8 T cells. We found that memory T cell phenotype differed substantially depending on the number of immunizations and that secondary and tertiary responses resulted in the generation of memory CD8 T cells that retained effector-like properties and showed preferential accumulation in nonlymphoid tissues. These results show that memory differentiation is coupled to the history of Ag experience and that prime-boost vaccination strategies have important consequences on memory CD8 T cell quality and surveillance within mucosal tissues.
Targeted Lymphoid Homing of Dendritic Cells Is Required for Prolongation of Allograft Survival
Authors: Garrod Kym R. , Chang Catherine K. , Liu Feng-Chun , Brennan Todd V. , Foster Robert D. , Kang Sang-Mo
Published: April 2014

Accumulating evidence that dendritic cells (DC) are important regulators of peripheral immune tolerance has led to the concept that donor-derived DC may be useful for inducing donor-specific transplantation tolerance. Although in vitro studies in this field have been encouraging, in vivo results have been inconsistent. Recent evidence has suggested a critical role of lymphoid organs in tolerance induction. In this study, we use a novel gene transduction technique to show that engineered expression of CCR7 on immature DC can markedly increase DC homing to lymphoid organs, leading to increased interaction with Ag-specific T cells. Moreover, we show that a single infusion of DC coexpressing CCR7 and the immunomodulatory molecule viral IL-10 (vIL-10) markedly prolongs cardiac allograft survival (mean survival time >100 days); importantly, DC expressing either vIL-10 alone or CCR7 alone was not effective. These results demonstrate an important paradigm for immune modulation using DC.
Small Interfering RNA-Mediated Knockdown of Notch Ligands in Primary CD4+ T Cells and Dendritic Cells Enhances Cytokine Production
Authors: Stallwood Yvette , Briend Emmanuel , Ray Katrina M. , Ward George A. , Smith Beverley J. , Nye Emma , Champion Brian R. , McKenzie Grahame J.
Published: April 2014

The key interaction in the adaptive immune system’s response to pathogenic challenge occurs at the interface between APCs and T cells. Families of costimulatory and coinhibitory molecules function in association with the cytokine microenvironment to orchestrate appropriate T cell activation programs. Recent data have demonstrated that the Notch receptor and its ligands also function at the APC:T interface. In this study, we describe synthetic small interfering RNA (siRNA) sequences targeting the human Notch ligands Delta1, Jagged1 and Jagged2. Transfection of these siRNAs into human primary CD4+ T cells and monocyte-derived dendritic cells leads to knockdown of endogenous Notch ligand message. Knockdown of any one of these three Notch ligands in dendritic cells enhanced IFN-γ production from allogeneic CD4+ T cells in MLR. In contrast, Delta1 knockdown in CD4+ T cells selectively enhanced production of IFN-γ, IL-2, and IL-5 in response to polyclonal stimulation, while Jagged1 or Jagged2 knockdown had no effect. Strikingly, blockade of Notch cleavage with a γ secretase inhibitor failed to affect cytokine production in this system, implying that Delta1 can influence cytokine production via a Notch cleavage-independent mechanism. These data show for the first time that the Notch pathway can be targeted by siRNA, and that its antagonism may be a unique therapeutic opportunity for immune enhancement.
Antigen-Experienced T Cells Limit the Priming of Naive T Cells during Infection withLeishmania major
Authors: Gray Peter M. , Reiner Steven L. , Smith Deborah F. , Kaye Paul M. , Scott Phillip
Published: April 2014

One mechanism to control immune responses following infection is to rapidly down-regulate Ag presentation, which has been observed in acute viral and bacterial infections. In this study, we describe experiments designed to address whether Ag presentation is decreased after an initial response to Leishmania major. Naive αβ-Leishmania-specific (ABLE) TCR transgenic T cells were adoptively transferred into mice at various times after L. major infection to determine the duration of presentation of parasite-derived Ags. ABLE T cells responded vigorously at the initiation of infection, but the ability to prime these cells quickly diminished, independent of IL-10, regulatory T cells, or Ag load. However, Ag-experienced clonal and polyclonal T cell populations could respond, indicating that the diminution in naive ABLE cell responses was not due to lack of Ag presentation. Because naive T cell priming could be restored by removal of the endogenous T cell population, or adoptive transfer of Ag-pulsed dendritic cells, it appears that T cells that have previously encountered Ag during infection compete with naive Ag-specific T cells. These results suggest that during L. major infection Ag-experienced T cells, rather than naive T cells, may be primarily responsible for sustaining the immune response.
Novel Function of IFN-γ: Negative Regulation of Dendritic Cell Migration and T Cell Priming
Authors: Wu Xiaodong , Hou Wanqiu , Sun Shuhui , Bi Enguang , Wang Yuan , Shi Mude , Zang Jingwu , Dong Chen , Sun Bing
Published: April 2014

IFN-γ is considered to be a Th1 cytokine with immunomodulatory effects on a variety of immune cells. In this study, we determined whether dendritic cell (DC) function was aberrant in IFN-γ knockout (GKO) mice. The results demonstrated that IFN-γ deficiency did not interfere with bone marrow-derived DC development and maturation in vitro. However, functional analysis showed that bone marrow-derived DC from GKO mice had altered cytokine secretion, allostimulatory and Ag presentation capacity, chemokine receptor expression, and in vitro chemotaxis. LPS induced the recruitment of DC from different organs into the spleen; epicutaneously sensitized DC with hapten (FITC) accumulated in the draining lymph nodes and CD11c+ DC levels in the draining lymph nodes from autoantigen (interphotoreceptor retinoid-binding protein) immunized mice were enhanced in GKO mice as compared with wild-type mice. After treatment of GKO mice with i.p. IFN-γ injection restored IFN-γ levels in vivo, DC migration decreased in response to LPS or FITC. IFN-γ altered the adaptive immune responses in vivo, since T cell priming and IL-2 production were increased in interphotoreceptor retinoid-binding protein-immunized GKO mice. Furthermore, in IFN-γ-treated GKO mice, experimental autoimmune uveitis score enhancement and T cell activation were eliminated. Taken together, IFN-γ appears to play a negative regulatory role on in vivo DC function, resulting in suppression of Ag-specific T cell priming.
Rapamycin-Mediated Enrichment of T Cells with Regulatory Activity in Stimulated CD4+ T Cell Cultures Is Not Due to the Selective Expansion of Naturally Occurring Regulatory T Cells but to the Induction of Regulatory Functions in Conventional CD4+ T Cells
Authors: Valmori Danila , Tosello Valeria , Souleimanian Naira E. , Godefroy Emmanuelle , Scotto Luigi , Wang Yu , Ayyoub Maha
Published: April 2014

Rapamycin is an immunosuppressive drug currently used in different clinical settings. Although the capacity of rapamycin to inhibit the mammalian target of rapamycin serine/threonine protein kinase and therefore T cell cycle progression is well known, its effects are complex and not completely understood. It has been reported recently that TCR-mediated stimulation of murine CD4+ T cells in the presence of rapamycin results in increased proportions of CD4+ T cells with suppressive functions, suggesting that the drug may also exert its immunosuppressive activity by promoting the selective expansion of naturally occurring CD4+ regulatory T cells (Treg). In this study, we show that stimulation of human circulating CD4+ T cells in the presence of rapamycin results indeed in highly increased suppressor activity. By assessing the effect of rapamycin on the growth of nonregulatory and Treg populations of defined differentiation stages purified ex vivo from circulating CD4+ T cells, we could demonstrate that this phenomenon is not due to a selective expansion of naturally occurring Tregs, but to the capacity of rapamycin to induce, upon TCR-mediated stimulation, suppressor functions in conventional CD4+ T cells. This condition, however, is temporary and reversible as it is dependent upon the continuous presence of rapamycin.
Protein Kinase Cδ Is Essential to Maintain CIITA Gene Expression in B Cells
Authors: Kwon Myung-Ja , Soh Jae-Won , Chang Cheong-Hee
Published: April 2014

Expression of MHC class II genes requires CIITA. Although the transactivation function of CIITA is well characterized, the signaling events that regulate CIITA expression are less understood. In this study, we report that CIITA expression in B cells depends on protein kinase Cδ (PKCδ). PKCδ controls CIITA gene transcription mainly via modulating CREB recruitment to the CIITA promoter without affecting CIITA mRNA stability. Inhibition of PKCδ by a pharmacological inhibitor or knocking down of endogenous PKCδ expression by small interfering RNA reduced CREB binding to the CIITA promoter. The decrease of CIITA gene expression in the presence of the PKCδ inhibitor was prevented by ectopically expressing a constitutively active form of CREB. In addition, histone acetylation of the CIITA promoter is regulated by PKCδ since the PKCδ inhibitor treatment or PKCδ small interfering RNA resulted in decreased histone acetylation. Taken together, our study reveals that PKCδ is an important signaling molecule necessary to maintain CIITA and MHC class II expression in B cells.
Functional Specialization of Memory Th Cells Revealed by Expression of Integrin CD49b
Authors: Kassiotis George , Gray David , Kiafard Ziba , Zwirner Jörg , Stockinger Brigitta
Published: April 2014

Infection or immunization induces heterogeneous memory T cell subsets, but their origin and protective value against infection are unclear. In this study, we report the functional characterization of two memory Th subsets, defined by expression of integrin CD49b. Stable CD49b expression is induced in up to one-half of all memory Th cells. More importantly, the CD49b− and CD49b+ subsets display distinct helper activities, typified by the production of IL-10 and TNF-α, respectively. Although the inflammatory properties of the CD49b+ subset are protective against intracellular bacterial infection, they are associated with immunopathology in acute viral infection. Modulation of the CD49b-defined memory Th subsets may provide infection type-specific interventions, where either enhancement of the inflammatory response or reduction of immunopathology is essential.
Generation of T Cell Help through a MHC Class I-Restricted TCR
Authors: Kessels Helmut W. H. G. , Schepers Koen , van den Boom Marly D. , Topham David J. , Schumacher Ton N. M.
Published: April 2014

CD4+ T cells that are activated by a MHC class II/peptide encounter can induce maturation of APCs and promote cytotoxic CD8+ T cell responses. Unfortunately, the number of well-defined tumor-specific CD4+ T cell epitopes that can be exploited for adoptive immunotherapy is limited. To determine whether Th cell responses can be generated by redirecting CD4+ T cells to MHC class I ligands, we have introduced MHC class I-restricted TCRs into postthymic murine CD4+ T cells and examined CD4+ T cell activation and helper function in vitro and in vivo. These experiments indicate that Ag-specific CD4+ T cell help can be induced by the engagement of MHC class I-restricted TCRs in peripheral CD4+ T cells but that it is highly dependent on the coreceptor function of the CD8β-chain. The ability to generate Th cell immunity by infusion of MHC class I-restricted Th cells may prove useful for the induction of tumor-specific T cell immunity in cases where MHC class II-associated epitopes are lacking.
CD8α Coreceptor to Improve TCR Gene Transfer to Treat Melanoma: Down-Regulation of Tumor-Specific Production of IL-4, IL-5, and IL-10
Authors: Willemsen Ralph A. , Sebestyén Zsolt , Ronteltap Cees , Berrevoets Cor , Drexhage Joost , Debets Reno
Published: April 2014

Therapeutic success of TCR gene transfer to treat tumors depends on the ability of redirected T cells to become activated upon tumor recognition in vivo. Help provided by tumor-specific Th1 cells is reported to relieve T cells from an anergized state and to induce tumor regression. We recently demonstrated the ability to generate melanoma-specific Th1 cells by genetic introduction of both a CD8-dependent TCR and the CD8α coreceptor into CD4+ T cells. In this study, we analyzed a TCR that binds Ag independently of CD8, a property generally preferred to induce tumor-specific T cell responses, and addressed the contribution of CD8α following introduction into TCR-transduced CD4+ T cells. To this end, primary human CD4+ T cells were gene transferred with a high-avidity TCR, and were shown not only to bind peptide/MHC class I, but also to effectively kill Ag-positive tumor cells in the absence of CD8α. The introduction of CD8α up-regulates the tumor-specific production of TNF-α and IL-2 to some extent, but significantly down-regulates production of IL-4, IL-5, and IL-10 in CD4+ T cells. The introduction of a mutated cysteine motif in CD8α, which prevents its binding to LCK and linker for activation of T cells, did not adversely affect expression and T cell cytotoxicity, but counteracted the CD8α-mediated down-regulation of IL-4 and IL-5, but not IL-10. In conclusion, CD8α down-regulates the production of major Th2-type cytokines, in part mediated by LCK and/or linker for activation of T cells, and may induce differentiation of tumor-specific Th1 cells, which makes this coreceptor an interesting candidate to improve the clinical potential of TCR gene transfer to treat cancer.
TRAIL Deficiency Delays, but Does Not Prevent, Erosion in the Quality of “Helpless” Memory CD8 T Cells
Authors: Badovinac Vladimir P. , Messingham Kelly A. Nordyke , Griffith Thomas S. , Harty John T.
Published: April 2014

In this study, we investigated the role of TRAIL in Ag-specific CD8 T cell homeostasis after viral infection. TRAIL deficiency does not influence the kinetics of the Ag-specific CD8 T cell responses, and CD8 T cells in TRAIL-deficient mice were able to expand, contract, and generate functional memory cell numbers that were indistinguishable from TRAIL-sufficient wild-type CD8 T cells after acute lymphocytic choriomeningitis virus infection. Interestingly, the ability of “helpless” CD8 T cells to retain their memory phenotypic and functional (i.e., secondary expansion) characteristics was prolonged in TRAIL-deficient mice compared with wild-type CD4-depleted controls. However, TRAIL deficiency only delayed, but did not prevent, the eventual erosion in the quality of helpless memory CD8 T cells, and that correlated with their inability to respond to a second round of Ag-driven proliferation. These data, which suggest that CD4 help consists of both TRAIL-dependent and -independent components, may help to resolve the current controversy between the early programming and maintenance models that were put forward to explain the role of CD4 T cell help in Ag-specific CD8 T cell homeostasis.
Cutting Edge: Dexamethasone Negatively Regulates Syk in Mast Cells by Up-Regulating Src-Like Adaptor Protein
Authors: Hiragun Takaaki , Peng Ze , Beaven Michael A.
Published: April 2014

We have identified Src-like adaptor protein (SLAP) as one of several dexamethasone-inducible inhibitory regulators in mast cells. SLAP is a known inhibitor of T cell signaling and interacts with the tyrosine kinase, Zap70. Exposure of RBL-2H3 mast cells to dexamethasone markedly increased expression of SLAP. Cells so exposed or made to overexpress SLAP exhibited reduced Ag-stimulated phosphorylation of Syk (a cognate of Zap70), linker for activation of T cells, phospholipase Cγ, and ERK. Ca2+ mobilization, Ca2+-dependent degranulation, and ERK-dependent release of arachidonic acid were suppressed as well. Small interfering RNA directed against SLAP blocked the induction of SLAP and reversed the inhibitory effects of dexamethasone on phosphorylation of Syk, linker for activation of T cells, and phospholipase Cγ, but not downstream events, which are likely suppressed by up-regulation of downstream of tyrosine kinase-1 and MAPK phosphatase-1. The induction of these inhibitory regulators may contribute to the immunosuppressive activity of dexamethasone in mast cells.
Mesenchymal Stem Cells Inhibit Generation and Function of Both CD34+-Derived and Monocyte-Derived Dendritic Cells
Authors: Nauta Alma J. , Kruisselbrink Alwine B. , Lurvink Ellie , Willemze Roel , Fibbe Willem E.
Published: April 2014

Mesenchymal stem cells (MSCs) are not only able to evade the immune system, but they have also been demonstrated to exert profound immunosuppressive properties on T cell proliferation. However, their effect on the initiators of the immune response, the dendritic cells (DCs), are relatively unknown. In the present study, the effects of human MSCs on the differentiation and function of both CD34+-derived DCs and monocyte-derived DCs were investigated. The presence of MSCs during differentiation blocked the differentiation of CD14+CD1a− precursors into dermal/interstitial DCs, without affecting the generation of CD1a+ Langerhans cells. In line with these observations, MSCs also completely prevented the generation of immature DCs from monocytes. The inhibitory effect of MSCs on DC differentiation was dose dependent and resulted in both phenotypical and functional modifications, as demonstrated by a reduced expression of costimulatory molecules and hampered capacity to stimulate naive T cell proliferation. The inhibitory effect of MSCs was mediated via soluble factors. Taken together, these data demonstrate that MSCs, next to the antiproliferative effect on T cells, have a profound inhibitory effect on the generation and function of both CD34+-derived and monocyte-derived DCs, indicating that MSCs are able to modulate immune responses at multiple levels.
RUNX3 Negatively Regulates CD36 Expression in Myeloid Cell Lines
Authors: Puig-Kröger Amaya , Domínguez-Soto Angeles , Martínez-Muñoz Laura , Serrano-Gómez Diego , Lopez-Bravo María , Sierra-Filardi Elena , Fernández-Ruiz Elena , Ruiz-Velasco Natividad , Ardavín Carlos , Groner Yoram , Tandon Narendra , Corbí Angel L. , Vega Miguel A.
Published: April 2014

CD36 is a member of the scavenger receptor type B family implicated in the binding of lipoproteins, phosphatidylserine, thrombospondin-1, and the uptake of long-chain fatty acids. On mononuclear phagocytes, recognition of apoptotic cells by CD36 contributes to peripheral tolerance and prevention of autoimmunity by impairing dendritic cell (DC) maturation. Besides, CD36 acts as a coreceptor with TLR2/6 for sensing microbial diacylglycerides, and its deficiency leads to increased susceptibility to Staphylococcus aureus infections. The RUNX3 transcription factor participates in reprogramming DC transcription after pathogen recognition, and its defective expression leads to abnormally accelerated DC maturation. We present evidence that CD36 expression is negatively regulated by the RUNX3 transcription factor during myeloid cell differentiation and activation. In molecular terms, RUNX3 impairs the activity of the proximal regulatory region of the CD36 gene in myeloid cells through in vitro recognition of two functional RUNX-binding elements. Moreover, RUNX3 occupies the CD36 gene proximal regulatory region in vivo, and its overexpression in myeloid cells results in drastically diminished CD36 expression. The down-regulation of CD36 expression by RUNX3 implies that this transcription factor could impair harmful autoimmune responses by contributing to the loss of pathogen- and apoptotic cell-recognition capabilities by mature DCs.
The Role of Structurally Conserved Class I MHC in Tumor Rejection: Contribution of the Q8 Locus
Authors: Chiang Eugene Y. , Stroynowski Iwona
Published: April 2014

The mouse multimember family of Qa-2 oligomorphic class I MHC genes is continuously undergoing duplications and deletions that alter the number of the two “prototype” Qa-2 sequences, Q8 and Q9. The frequent recombination events within the Q region lead to strain-specific modulation of the cumulative Qa-2 expression levels. Q9 protects C57BL/6 hosts from multiple disparate tumors and functions as a major CTL restriction element for shared tumor-associated Ags. We have now analyzed functional and structural properties of Q8, a class I MHC that differs significantly from Q9 in the peptide-binding, CTL-interacting α1 and α2 regions. Unexpectedly, we find that the extracellular domains of Q8 and Q9 act similarly during primary and secondary rejection of tumors, are recognized by cross-reactive antitumor CTL, have overlapping peptide-binding motifs, and are both assembled via the transporter associated with the Ag processing pathway. These findings suggest that shared Ag-presenting functions of the “odd” and “even” Qa-2 loci may contribute to the selective pressures shaping the haplotype-dependent quantitative variation of Qa-2 protein expression.
Defective Activation of Protein Kinase C and Ras-ERK Pathways Limits IL-2 Production and Proliferation by CD4+CD25+ Regulatory T Cells
Authors: Hickman Somia P. , Yang Jaeseok , Thomas Rajan M. , Wells Andrew D. , Turka Laurence A.
Published: April 2014

Naturally occurring CD4+CD25+ regulatory T cells (Tregs), which play an important role in the maintenance of self-tolerance, proliferate poorly and fail to produce IL-2 following stimulation in vitro with peptide-pulsed or anti-CD3-treated APCs. When TCR proximal and distal signaling events were examined in Tregs, we observed impairments in the amplitude and duration of tyrosine phosphorylation when compared with the response of CD4+CD25− T cells. Defects were also seen in the activity of phospholipase C-γ and in signals downstream of this enzyme including calcium mobilization, NFAT, NF-κB, and Ras-ERK-AP-1 activation. Enhanced stimulation of diacylglycerol-dependent pathways by inhibition of diacylglycerol metabolism could overcome the “anergic state” and support the ability of Tregs to up-regulate CD69, produce IL-2, and proliferate. Our results demonstrate that Tregs maintain their hyporesponsive state by suppressing the induction and propagation of TCR-initiated signals to control the accumulation of second messengers necessary for IL-2 production and proliferation.
Intradermal Delivery of Adenoviral Type-35 Vectors Leads to High Efficiency Transduction of Mature, CD8+ T Cell-Stimulating Skin-Emigrated Dendritic Cells
Authors: de Gruijl Tanja D. , Ophorst Olga J. A. E. , Goudsmit Jaap , Verhaagh Sandra , Lougheed Sinéad M. , Radosevic Katarina , Havenga Menzo J. E. , Scheper Rik J.
Published: April 2014

Recombinant adenovirus (Ad) type 35 (rAd35) shows great promise as vaccine carrier with the advantage of low pre-existing immunity in human populations, in contrast to the more commonly used rAd5 vector. The rAd35 vector uses CD46 as a high-affinity receptor, which, unlike the rAd5 receptor, is expressed on human dendritic cells (DC), the most powerful APCs identified to date. In this study, we show that in contrast to rAd5, rAd35 infects migrated and mature CD83+ cutaneous DC with high efficiency (up to 80%), when delivered intradermally in an established human skin explant model. The high transduction efficiency is in line with high expression levels of CD46 detected on migratory cutaneous DC, which proved to be further increased upon intradermal administration of GM-CSF and IL-4. As compared with Ad5, these Ad35 infection characteristics translate into higher absolute numbers of skin-emigrated DC per explant that both express the transgene and are phenotypically mature. Finally, we demonstrate that upon intracutaneous delivery of a rAd35 vaccine encoding the circumsporozoite (CS) protein of Plasmodium falciparum, emigrated DC functionally express and process CS-derived epitopes and are capable of activating specific CD8+ effector T cells, as evidenced by activation of an HLA-A2-restricted CS-specific CD8+ T cell clone. Collectively, these data demonstrate the utility of rAd35 vectors for efficient in vivo human DC transduction.
Constitutive Activation of STAT5 Supersedes the Requirement for Cytokine and TCR Engagement of CD4+ T Cells in Steady-State Homeostasis
Authors: Taylor Devon K. , Walsh Patrick T. , LaRosa David F. , Zhang Jidong , Burchill Matthew A. , Farrar Michael A. , Turka Laurence A.
Published: April 2014

The transcription factor STAT5 is one of several signaling mediators activated via common γ-chain cytokine receptors. As such, it plays an important role in lymphocyte survival and proliferation during normal homeostasis as well as under lymphopenic conditions. Transgenic mice expressing a constitutively activated form of STAT5b have been shown previously to contain increased numbers of peripheral CD4+CD25− T cells. To define the mechanism(s) for this occurrence, we have used adoptive transfer studies to examine the effects of STAT5 activity on steady-state CD4+ T cell homeostasis. We observed that constitutive STAT5 signaling induced 4- to 7-fold increased levels of basal steady-state proliferation, which was accompanied by a comparable increase in T cell recovery. Most strikingly, steady-state CD4 T cell proliferation occurred independently of both MHC class II and IL-15. These observations demonstrate that the STAT5-driven pathway is important to lymphocyte homeostasis and can supersede the need for both TCR engagement and cytokine stimulation. This suggests that the need for TCR stimulation to induce common γ-chain cytokine receptor expression, and thus STAT5 activation, is a key factor in maintaining normal CD4+ T cell homeostasis.
Impaired Intracellular Calcium Mobilization and NFATc1 Availability in Tolerant Anti-Insulin B Cells
Authors: Acevedo-Suárez Carlos A. , Kilkenny Dawn M. , Reich Martha B. , Thomas James W.
Published: April 2014

B lymphocytes that recognize soluble self-Ags are routinely found in normal individuals in a functionally inactive or anergic state. Current models indicate that this tolerant state is maintained by interactions with self-Ags that uncouple the BCR from downstream signaling pathways and increase levels of free calcium. Contrary to this expectation, B cells that harbor anti-insulin Ig transgenes (125Tg) are maintained in a tolerant state even though free calcium levels remain normal and tyrosine kinase substrate phosphorylation is preserved following BCR stimulation. Under basal conditions, intracellular levels of inositol 1,4,5-trisphosphate are increased and NFATc1 levels are reduced in 125Tg B cells. The 125Tg B cells are markedly impaired in their ability to mobilize calcium upon stimulation with ionomycin, and BCR-induced calcium mobilization from internal stores is decreased. In contrast, poisoning intracellular calcium pumps with thapsigargin increases calcium mobilization in 125Tg B cells. Changes in calcium signaling are accompanied by a failure of 125Tg B cells to translocate NFATc1 into the nucleus following stimulation with either anti-IgM or ionomycin. Thus, disassociation of BCR from multiple signaling pathways is not essential for maintaining tolerance in anti-insulin 125Tg B cells. Rather, BCRs that are occupied by autologous insulin deliver signals that induce changes in intracellular calcium mobilization and maintain tolerance by preventing activation of key transcription factors such as NFAT.
Opposite Fate of Endocytosed CCR7 and Its Ligands: Recycling versus Degradation
Authors: Otero Carolina , Groettrup Marcus , Legler Daniel F.
Published: April 2014

The chemokine receptor CCR7 and its ligands CCL19 and CCL21 play a crucial role for the homing of lymphocytes and dendritic cells to secondary lymphoid tissues. Nevertheless, how CCR7 senses the gradient of chemokines and how migration is terminated are poorly understood. In this study, we demonstrate that CCR7(-GFP) is endocytosed into early endosomes containing transferrin receptor upon CCL19 binding, but less upon CCL21 triggering. Internalization of CCR7 was independent of lipid rafts but relied on dynamin and Eps15 and was inhibited by hypertonic sucrose, suggesting clathrin-dependent endocytosis. After chemokine removal, internalized CCR7 recycled back to the plasma membrane and was able to mediate migration again. In contrast, internalized CCL19 was sorted to lysosomes for degradation, showing opposite fate for endocytosed CCR7 and its ligand.
TGF-β-Mediated Suppression by CD4+CD25+ T Cells Is Facilitated by CTLA-4 Signaling
Authors: Oida Takatoku , Xu LiLi , Weiner Howard L. , Kitani Atsushi , Strober Warren
Published: April 2014

CD4+CD25+ T cells play a pivotal role in immunological homeostasis by their capacity to exert immunosuppressive activity. However, the mechanism by which these cells function is still a subject for debate. We previously reported that surface (membrane) TGF-β produced by CD4+CD25+ T cells was an effector molecule mediating suppressor function. We now support this finding by imaging surface TGF-β on Foxp3+CD4+CD25+ T cells in confocal fluorescence microscopy. Then, using a TGF-β-sensitive mink lung epithelial cell (luciferase) reporter system, we show that surface TGF-β can be activated to signal upon cell-cell contact. Moreover, if such TGF-β signaling is blocked in an in vitro assay of CD4+CD25+ T cell suppression by a specific inhibitor of TGF-βRI, suppressor function is also blocked. Finally, we address the role of CTLA-4 in CD4+CD25+ T cell suppression, showing first that whereas anti-CTLA-4 does not block in vitro suppressor function, it does complement the blocking activity of anti-TGF-β. We then show with confocal fluorescence microscopy that incubation of CD4+CD25+ T cells with anti-CTLA-4- and rB7-1/Fc-coated beads results in accumulation of TGF-β at the cell-bead contact site. This suggests that CTLA-4 signaling facilitates TGF-β-mediated suppression by intensifying the TGF-β signal at the point of suppressor cell-target cell interaction.
Distinct Responses of Lung and Spleen Dendritic Cells to the TLR9 Agonist CpG Oligodeoxynucleotide
Authors: Chen Li , Arora Meenakshi , Yarlagadda Manohar , Oriss Timothy B. , Krishnamoorthy Nandini , Ray Anuradha , Ray Prabir
Published: April 2014

Dendritic cells (DCs) sense various components of invading pathogens via pattern recognition receptors such as TLRs. CpG oligodeoxynucleotides (ODNs), which mimic bacterial DNA, inhibit allergic airways disease and promote responses in the spleen to bacterial components. Because many TLR agonists are currently being tested for potential therapeutic effects, it is important to characterize the expression and function of TLRs in different tissues. We show that both myeloid and plasmacytoid DCs in the spleen express TLR9, the receptor for CpG ODNs, but lung DCs show no detectable expression in either subset. TLR4 expression in contrast was detected on both lung and spleen DCs. LPS was superior to CpG ODN in increasing the allostimulatory potential of lung DCs and their expression of CD40. However, both agonists efficiently stimulated spleen DCs. CpG ODNs administered to mice efficiently inhibited Th2 cytokine production both in the lung draining lymph node and in the spleen. Surprisingly, inhibition of Th2 cytokine production was evident despite high levels of expression of GATA-3 and additional transcription factors that regulate Th2 responses. Although in the spleen CpG ODNs induced IL-6, a key cytokine induced via TLR9-MyD88 signaling, no IL-6 was detectable in lung LN cells. These studies show for the first time that lung DCs lack TLR9 expression, but, despite this deficiency, CpG ODNs induce potent inhibitory effects on Th2 cytokine production in the lung without inducing expression of the proinflammatory cytokine, IL-6, which has been linked to chronic diseases in the lung and the gut.
Cyclooxygenase-2 Inhibitor Enhances the Efficacy of a Breast Cancer Vaccine: Role of IDO
Authors: Basu Gargi D. , Tinder Teresa L. , Bradley Judy M. , Tu Tony , Hattrup Christine L. , Pockaj Barbara A. , Mukherjee Pinku
Published: April 2014

We report that administration of celecoxib, a specific cyclooxygenase-2 (COX-2) inhibitor, in combination with a dendritic cell-based cancer vaccine significantly augments vaccine efficacy in reducing primary tumor burden, preventing metastasis, and increasing survival. This combination treatment was tested in MMTV-PyV MT mice that develop spontaneous mammary gland tumors with metastasis to the lungs and bone marrow. Improved vaccine potency was associated with an increase in tumor-specific CTLs. Enhanced CTL activity was attributed to a significant decrease in levels of tumor-associated IDO, a negative regulator of T cell activity. We present data suggesting that inhibiting COX-2 activity in vivo regulates IDO expression within the tumor microenvironment; this is further corroborated in the MDA-MB-231 human breast cancer cell line. Thus, a novel mechanism of COX-2-induced immunosuppression via regulation of IDO has emerged that may have implications in designing future cancer vaccines.
Activation of Murine CD4+ and CD8+ T Lymphocytes Leads to Dramatic Remodeling ofN-Linked Glycans
Authors: Comelli Elena M. , Sutton-Smith Mark , Yan Qi , Amado Margarida , Panico Maria , Gilmartin Tim , Whisenant Thomas , Lanigan Caroline M. , Head Steven R. , Goldberg David , Morris Howard R. , Dell Anne , Paulson James C.
Published: April 2014

Differentiation and activation of lymphocytes are documented to result in changes in glycosylation associated with biologically important consequences. In this report, we have systematically examined global changes in N-linked glycosylation following activation of murine CD4 T cells, CD8 T cells, and B cells by MALDI-TOF mass spectrometry profiling, and investigated the molecular basis for those changes by assessing alterations in the expression of glycan transferase genes. Surprisingly, the major change observed in activated CD4 and CD8 T cells was a dramatic reduction of sialylated biantennary N-glycans carrying the terminal NeuGcα2-6Gal sequence, and a corresponding increase in glycans carrying the Galα1-3Gal sequence. This change was accounted for by a decrease in the expression of the sialyltransferase ST6Gal I, and an increase in the expression of the galactosyltransferase, α1-3GalT. Conversely, in B cells no change in terminal sialylation of N-linked glycans was evident, and the expression of the same two glycosyltransferases was increased and decreased, respectively. The results have implications for differential recognition of activated and unactivated T cells by dendritic cells and B cells expressing glycan-binding proteins that recognize terminal sequences of N-linked glycans.
E2A Promotes the Survival of Precursor and Mature B Lymphocytes
Authors: Lazorchak Adam S. , Wojciechowski Jason , Dai Meifang , Zhuang Yuan
Published: April 2014

The basic helix-loop-helix transcription factor E2A is an essential regulator of B lymphocyte lineage commitment and is required to activate the expression of numerous B lineage-specific genes. Studies involving ectopic expression of Id proteins, which inhibit E2A as well as other basic helix-loop-helix proteins such as HEB, suggest additional roles of E2A at later stages of B cell development. We use E2A-deficient and E2A and HEB double-deficient pre-B cell lines to directly assess the function of E2A and HEB in B cell development after lineage commitment. We show that, in contrast to the established role of E2A in lineage commitment, elimination of E2A and HEB in pre-B cell lines has only a modest negative impact on B lineage gene expression. However, E2A single and E2A and HEB double-deficient but not HEB single-deficient cell lines show dramatically enhanced apoptosis upon growth arrest. To address the possible role of E2A in the regulation of B cell survival in vivo, we crossed IFN-inducible Cre-transgenic mice to E2A conditional mice. Cre-mediated E2A deletion resulted in a block in bone marrow B cell development and a significant reduction in the proportion and total number of splenic B cells in these mice. We show that Cre-mediated deletion of E2A in adoptively transferred mature B cells results in the rapid depletion of the transferred population within 24 h of Cre induction. These results reveal that E2A is not required to maintain B cell fate but is essential in promoting pre-B and B cell survival.
CD8+ T Lymphocyte-Mediated Loss of Marginal Metallophilic Macrophages following Infection withPlasmodium chabaudi chabaudi AS
Authors: Beattie Lynette , Engwerda Christian R. , Wykes Michelle , Good Michael F.
Published: April 2014

The splenic architecture is essential for the quick resolution of a primary infection with Plasmodium. A critical component of this architecture is the marginal zone (MZ), an area of the spleen that separates the reticuloendothelial red pulp of the spleen from the lymphoid white pulp compartment. There are two unique macrophage populations found in the MZ: MZ macrophages (MZM) found on the outer border of the MZ, and marginal metallophilic macrophages (MMM) found on the inner border, adjacent to the white pulp. We investigated the homeostasis of MMM and MZM following infection with Plasmodium chabaudi and demonstrated that a complete loss of both MMM and MZM occurred by the time of peak parasitemia, 8 days after infection. The loss was not induced by up-regulation of the inflammatory cytokines TNF or IFN-γ. In contrast, following only CD8+ T cell depletion (not dendritic cell), MMM but not MZM were retained, implicating CD8+ T cells in the P. chabaudi-induced loss of MMM. Retention of MMM occurred in mice deficient in CD95, CD95-ligand, and perforin, indicating that these signals are involved in the death pathway of MMM. These data have significant implications for the understanding of the immune-mediated pathology of the spleen as a result of infection with Plasmodium.
Nuclear Accumulation of cRel following C-Terminal phosphorylation by TBK1/IKKε
Authors: Harris Jennifer , Olière Stéphanie , Sharma Sonia , Sun Qiang , Lin Rongtuan , Hiscott John , Grandvaux Nathalie
Published: April 2014

The NF-κB transcription factors are key regulators of immunomodulatory, cell cycle, and developmental gene regulation. NF-κB activity is mainly regulated through the phosphorylation of IκB by the IκB kinase (IKK) complex IKKαβγ, leading to proteasome-mediated degradation of IκB, nuclear translocation of NF-κB dimers, DNA binding, and gene induction. Additionally, direct posttranslational modifications of NF-κB p65 and cRel subunits involving C-terminal phosphorylation has been demonstrated. The noncanonical IKK-related homologs, TNFR-associated factor family member-associated NF-κB activator (TANK)-binding kinase (TBK)1 and IKKε, are also thought to play a role in NF-κB regulation, but their functions remain unclear. TBK1 and IKKε were recently described as essential regulators of IFN gene activation through direct phosphorylation of the IFN regulatory factor-3 and -7 transcription factors. In the present study, we sought to determine whether IKKε and TBK1 could modulate cRel activity via phosphorylation. TBK1 and IKKε directly phosphorylate the C-terminal domain of cRel in vitro and in vivo and regulate nuclear accumulation of cRel, independently of the classical IκB/IKK pathway. IκBα degradation is not affected, but rather IKKε-mediated phosphorylation of cRel leads to dissociation of the IκBα-cRel complex. These results illustrate a previously unrecognized aspect of cRel regulation, controlled by direct IKKε/TBK1 phosphorylation.