bluuebunny/crossref_metadata_2025 huggingface dataset:
Native HIV-1 Tat Protein Targets Monocyte-Derived Dendritic Cells and Enhances Their Maturation, Function, and Antigen-Specific T Cell Responses
Authors: Fanales-Belasio Emanuele , Moretti Sonia , Nappi Filomena , Barillari Giovanni , Micheletti Fabiola , Cafaro Aurelio , Ensoli Barbara
Published: April 2014

Vaccination of cynomolgus monkeys with the biologically active HIV-1 Tat protein induces specific Th1 responses, including CTLs. Similar responses are also induced by vaccination with tat DNA, but not by vaccination with inactivated Tat or Tat peptides. This suggested that the native Tat protein may act differently on APC as compared with inactivated Tat or peptide Ag. In this study, we show that biologically active Tat is very efficiently taken up by monocyte-derived dendritic cells (MDDC) in a time (within minutes)- and dose-dependent (starting from 0.1 ng/ml) fashion, whereas uptake is very poor or absent with other APC, including T cell blasts and B lymphoblastoid cell lines. Although maturation of MDDC reduces their pino/phagocytic activity, mature MDDC take up Tat much more efficiently than immature cells. In addition, Tat uptake is abolished or greatly hampered by oxidation/inactivation of the protein or by performing the experiments at 4°C, suggesting that MDDC take up native Tat by a receptor-mediated endocytosis. After uptake, active Tat protein induces up-regulation of MHC and costimulatory molecules and production of IL-12, TNF-α, and β chemokines, which drive Th1-type immune response. In contrast, these effects are lost by oxidation and inactivation of the protein. Finally, native Tat enhances Ag presentation by MDDC, increasing Ag-specific T cell responses. These data indicate that native Tat selectively targets MDDC, is taken up by these cells via specialized pathways, and promotes their maturation and Ag-presenting functions, driving Th1-type immune responses. Thus, Tat can act as both Ag and adjuvant, capable of driving T cell-mediated immune responses.
Dual Effect of CD85/Leukocyte Ig-Like Receptor-1/Ig-Like Transcript 2 and CD152 (CTLA-4) on Cytokine Production by Antigen-Stimulated Human T Cells
Authors: Saverino Daniele , Merlo Andrea , Bruno Silvia , Pistoia Vito , Grossi Carlo E. , Ciccone Ermanno
Published: April 2014

The functional outcome of a T cell response to Ag is the result of a balance between coactivation and inhibitory signals. In this study we have investigated the effects of the CD85/leukocyte Ig-like receptor (LIR)-1/Ig-like transcript (ILT) 2 and of CD152 (CTLA-4) inhibitory receptors on the modulation of cell-mediated immune responses to specific Ags, both at the effector and at the resting/memory cell level. Proliferation and cytokine production of CD4+ T lymphocytes stimulated by recall Ags have been evaluated. Cross-linking of CD85/LIR-1/ILT2 or CD152 molecules on cultured T cells using specific mAb and goat anti-mouse antiserum inhibits Ag-specific T cell proliferation. This inhibition is always paralleled by increased production of cytokines that down-regulate immune responses, e.g., IL-10 and TGF-β. In contrast, the production of cytokines that support T cell expansion and function (e.g., IL-2, IFN-γ, and IL-13) is significantly decreased. A long-term effect of CD85/LIR-1/ILT2 and of CD152 occurs during Ag-specific T cell activation and expansion. T cells, primed in the presence of anti-CD85/LIR-1/ILT2 and anti-CD152 blocking mAb (but in the absence of cross-linking), proliferate at higher rates and produce higher amounts of IL-2, IFN-γ, and IL-13, in comparison with T cells stimulated with the Ag alone. We also show that the inhibitory receptors exert a similar effect during Ag activation of specific CD4+ effector T cells. Ag-specific polyclonal CD4+ T cell lines exhibit increased proliferation and IL-2, IFN-γ, and IL-13 production when the CD85/LIR-1/ILT2 receptor is blocked by specific mAb. In contrast, cross-linking of this receptor down-regulates Ag-specific CD4+ T cell proliferation and increases IL-10 and TGF-β production.
CD8 T Cells Inhibit IgE Via Dendritic Cell IL-12 Induction That Promotes Th1 T Cell Counter-Regulation
Authors: Thomas Matthew J. , Noble Alistair , Sawicka Ela , Askenase Philip W. , Kemeny David M.
Published: April 2014

Th1 and Th2 cells are counterinhibitory; their balance determines allergic sensitization. We show here that CD8 T cell subsets break these rules as both T cytotoxic (Tc)1 and Tc2 cells promote Th1 over Th2 immunity. Using IL-12−/−, IFN-γ−/−, and OVA257–264-specific Vα2Vβ5 TCR-transgenic mice, we have identified the key steps involved. OVA-specific IFN-γ−/− CD8 T cells inhibited IgE responses equivalent to wild-type CD8 T cells (up to 98% suppression), indicating that CD8 T cell-derived IFN-γ was not required. However, OVA-specific CD8 T cells could not inhibit IgE in IFN-γ−/− recipients unless reconstituted with naive, wild-type CD4 T cells, suggesting that CD4 T cell-derived IFN-γ did play a role. Transfer of either Tc1 or Tc2 Vα2Vβ5 TCR-transgenic CD8 T cells inhibited IgE and OVA-specific Th2 cells while promoting OVA-specific Th1 cell responses, suggesting a potential role for a type 1 inducing cytokine such as IL-12. CD8 T cells were shown to induce IL-12 in OVA257–264-pulsed dendritic cells (DC) in vitro. Furthermore, CD8 T cells were unable to inhibit IgE responses in IL-12−/− recipients without the addition of naive, wild-type DC, thus demonstrating a pivotal role for IL-12 in this mechanism. These data reveal a mechanism of IgE regulation in which CD8 T cells induce DC IL-12 by an IFN-γ-independent process that subsequently induces Th1 and inhibits Th2 cells. Th1 cell IFN-γ is the final step that inhibits B cell IgE class switching. This demonstrates a novel regulatory network through which CD8 T cells inhibit allergic sensitization.
CD5-Negative Regulation of B Cell Receptor Signaling Pathways Originates from Tyrosine Residue Y429 Outside an Immunoreceptor Tyrosine-Based Inhibitory Motif
Authors: Gary-Gouy Hélène , Harriague Julie , Dalloul Ali , Donnadieu Emmanuel , Bismuth Georges
Published: April 2014

CD5 is a cell surface receptor that negatively regulates B cell function, but whose relationship to the immunoreceptor tyrosine-based inhibitory motif (ITIM) family of B cell inhibitory receptors is unclear. Using Fcγ type IIB receptor-CD5 chimeras encompassing the cytoplasmic domain of CD5, we previously showed that a particular region of the molecule containing two tyrosine residues, Y429 and Y441, in an amino acid stretch similar to the Src autophosphorylation motif and a putative ITIM, respectively, antagonized early signaling events triggered through the B cell receptor (BCR). In this study, we provide evidences that only Y429 is mandatory for the inhibition by CD5 of the calcium response activated via the BCR. This residue also efficiently controls inhibition of the Ras/extracellular signal-related kinase-2 pathway. Analyzing the membrane translocation of the AKT protooncogene using its 3′-phosphoinositide-specific pleckstrin homology domain fused to the green fluorescent protein as a probe, we also show that CD5 strongly impairs its cellular redistribution and demonstrate the role played by Y429 in this process. We finally report that Y429 controls almost exclusively CD5 phosphorylation as well as inhibition of BCR-triggered IL-2 production upon coaggregation of the two receptors. Thus, CD5 uses an ITIM-independent strategy, centered on Y429, the major tyrosine-phosphorylated residue in its cytoplasmic domain, to inhibit BCR activation.
Complementary Adhesion Molecules Promote Neutrophil- Kupffer Cell Interaction and the Elimination of Bacteria Taken Up by the Liver
Authors: Gregory Stephen H. , Cousens Leslie P. , van Rooijen Nico , Döpp Ed A. , Carlos Timothy M. , Wing Edward J.
Published: April 2014

Most bacteria that enter the bloodstream are taken up by the liver. Previously, we reported that such organisms are initially bound extracellularly and subsequently killed by immigrating neutrophils, not Kupffer cells as widely presumed in the literature. Rather, the principal functions of Kupffer cells demonstrated herein are to clear bacteria from the peripheral blood and to promote accumulation of bactericidal neutrophils at the principal site of microbial deposition in the liver, i.e., the Kupffer cell surface. In a mouse model of listeriosis, uptake of bacteria by the liver at 10 min postinfection i.v. was reduced from approximately 60% of the inoculum in normal mice to ∼15% in mice rendered Kupffer cell deficient. Immunocytochemical analysis of liver sections derived from normal animals at 2 h postinfection revealed the massive immigration of neutrophils and their colocalization with Kupffer cells. Photomicrographs of the purified nonparenchymal liver cell population derived from these infected mice demonstrated listeriae inside neutrophils and neutrophils within Kupffer cells. Complementary adhesion molecules promoted the interaction between these two cell populations. Pretreatment of mice with mAbs specific for CD11b/CD18 (type 3 complement receptor) or its counter-receptor, CD54, inhibited the accumulation of neutrophils in the liver and the elimination of listeriae. Complement was not a factor; complement depletion affected neither the clearance of listeriae by Kupffer cells nor the antimicrobial activity expressed by infiltrating neutrophils.
Natural Killer T Cells Restricted by the Monomorphic MHC Class 1b CD1d1 Molecules Behave Like Inflammatory Cells
Authors: Mempel Martin , Ronet Catherine , Suarez Felipe , Gilleron Martine , Puzo Germain , Van Kaer Luc , Lehuen Agnès , Kourilsky Philippe , Gachelin Gabriel
Published: April 2014

Murine Vα14invT cells (NKT cells), restricted by the CD1d1 MHC 1b molecules, are a distinctive subset of T cells endowed with pleiotropic functions. CD1d1-restricted NKT cells infiltrate the granulomas induced by the s.c. injection of mycobacterial phosphatidylinositoldimannoside (PIM2) but not of its deacylated derivative. NKT cells are detectable as early as 6 hours following the injection. Although the molecular structure of PIM2 meets the requirements for presentation by CD1d1, Ab blocking and adoptive transfer experiments of wild-type NKT cells into CD1d1−/− mice show that CD1d1 expression is not required for the early recruitment of NKT cells to the injection site. This conclusion was confirmed by the finding that IL-12Rβ−/− and CD40−/− mice were able to recruit NKT cells after PIM2 challenge. Moreover, the injection of α-galactosylceramide, an NKT cell ligand that is recognized in the context of CD1d1, promoted only a minor recruitment of NKT cells. By contrast, injection of β-galactosylceramide, a synthetic glycolipid that binds to CD1d1 but does not activate the CD1d/TCR pathway, resulted in the development of large granulomas rich in NKT cells. Finally, local injection of TNF-α mimics the effect of glycolipids. It is concluded that NKT cells migrate to and accumulate at inflammatory sites in the same way as other cells of the innate immune system and that migration to and accumulation at inflammatory sites are processes independent of the CD1d1 molecule.
Colony-Stimulating Factor-1 Suppresses Responses to CpG DNA and Expression of Toll-Like Receptor 9 but Enhances Responses to Lipopolysaccharide in Murine Macrophages
Authors: Sweet Matthew J. , Campbell Carol C. , Sester David P. , Xu Damo , McDonald Rebecca C. , Stacey Katryn J. , Hume David A. , Liew Foo Y.
Published: April 2014

During bacterial infections, the balance between resolution of infection and development of sepsis is dependent upon the macrophage response to bacterial products. We show that priming of murine bone marrow-derived macrophages (BMMs) with CSF-1 differentially regulates the response to two such stimuli, LPS and immunostimulatory (CpG) DNA. CSF-1 pretreatment enhanced IL-6, IL-12, and TNF-α production in response to LPS but suppressed the same response to CpG DNA. CSF-1 also regulated cytokine gene expression in response to CpG DNA and LPS; CpG DNA-induced IL-12 p40, IL-12 p35, and TNF-α mRNAs were all suppressed by CSF-1 pretreatment. CSF-1 pretreatment enhanced LPS-induced IL-12 p40 mRNA but not TNF-α and IL-12 p35 mRNAs, suggesting that part of the priming effect is posttranscriptional. CSF-1 pretreatment also suppressed CpG DNA-induced nuclear translocation of NF-κB and phosphorylation of the mitogen-activated protein kinases p38 and extracellular signal-related kinases-1/2 in BMMs, indicating that early events in CpG DNA signaling were regulated by CSF-1. Expression of Toll-like receptor (TLR)9, which is necessary for responses to CpG DNA, was markedly suppressed by CSF-1 in both BMMs and thioglycolate-elicited peritoneal macrophages. CSF-1 also down-regulated expression of TLR1, TLR2, and TLR6, but not the LPS receptor, TLR4, or TLR5. Hence, CSF-1 may regulate host responses to pathogens through modulation of TLR expression. Furthermore, these results suggest that CSF-1 and CSF-1R antagonists may enhance the efficacy of CpG DNA in vivo.
A Role for the Rho-p160 Rho Coiled-Coil Kinase Axis in the Chemokine Stromal Cell-Derived Factor-1α-Induced Lymphocyte Actomyosin and Microtubular Organization and Chemotaxis
Authors: Vicente-Manzanares Miguel , Cabrero José Román , Rey Mercedes , Pérez-Martínez Manuel , Ursa Angeles , Itoh Kazuyuki , Sánchez-Madrid Francisco
Published: April 2014

The possible involvement of the Rho-p160ROCK (Rho coiled-coil kinase) pathway in the signaling induced by the chemokine Stromal cell-derived factor (SDF)-1α has been studied in human PBL. SDF-1α induced activation of RhoA, but not that of Rac. RhoA activation was followed by p160ROCK activation mediated by RhoA, which led to myosin light chain (MLC) phosphorylation, which was dependent on RhoA and p160ROCK activities. The kinetics of MLC activation was similar to that of RhoA and p160ROCK. The role of this cascade in overall cell morphology and functional responses to the chemokine was examined employing different chemical inhibitors. Inhibition of either RhoA or p160ROCK did not block SDF-1α-induced short-term actin polymerization, but induced the formation of long spikes arising from the cell body, which were found to be microtubule based. This morphological change was associated with an increase in microtubule instability, which argues for an active microtubule polymerization in the formation of these spikes. Inhibition of the Rho-p160ROCK-MLC kinase signaling cascade at different steps blocked lymphocyte migration and the chemotaxis induced by SDF-1α. Our results indicate that the Rho-p160ROCK axis plays a pivotal role in the control of the cell shape as a step before lymphocyte migration toward a chemotactic gradient.
Bacterial Lipopolysaccharide Selectively Up-Regulates the Function of the Chemotactic Peptide Receptor Formyl Peptide Receptor 2 in Murine Microglial Cells
Authors: Cui You-Hong , Le Yingying , Gong Wanghua , Proost Paul , Van Damme Jo , Murphy William J. , Wang Ji Ming
Published: April 2014

Receptors for the bacterial chemotactic peptide fMLP are implicated in inflammation and host defense against microbial infection. We investigated the expression and function of fMLPR in microglial cells, which share characteristics of mononuclear phagocytes and play an important role in proinflammatory responses in the CNS. The expression of the genes encoding formyl peptide receptor (FPR)1 and FPR2, the high- and low-affinity fMLPR, was detected in a murine microglial cell line N9, but these cells did not respond to chemotactic agonists known for these receptors. N9 cells incubated with bacterial LPS increased the expression of fMLPR genes and developed a species of specific, but low-affinity, binding sites for fMLP, in association with marked calcium mobilization and chemotaxis responses to fMLP in a concentration range that typically activated the low-affinity receptor FPR2. In addition, LPS-treated N9 cells were chemoattracted by two FPR2-specific agonists, the HIV-1 envelope-derived V3 peptide, and the 42 aa form of the amyloid β peptide which is a pathogenic agent in Alzheimer’s disease. Primary murine microglial cells also expressed FPR1 and FPR2 genes, but similar to N9 cells, exhibited FPR2-mediated activation only after LPS treatment. In contrast to its effect on the function of FPR2, LPS reduced N9 cell binding and biological responses to the chemokine stromal cell-derived factor-1α. Thus, LPS selectively modulates the function of chemoattractant receptors in microglia and may promote host response in inflammatory diseases in the CNS.
Pronounced Eosinophilic Lung Inflammation and Th2 Cytokine Release in Human Lipocalin-Type Prostaglandin D Synthase Transgenic Mice
Authors: Fujitani Yasushi , Kanaoka Yoshihide , Aritake Kosuke , Uodome Nobuko , Okazaki-Hatake Kazue , Urade Yoshihiro
Published: April 2014

PGD2 is a major lipid mediator released from mast cells, but little is known about its role in the development of allergic reactions. We used transgenic (TG) mice overexpressing human lipocalin-type PGD synthase to examine the effect of overproduction of PGD2 in an OVA-induced murine asthma model. The sensitization of wild-type (WT) and TG mice was similar as judged by the content of OVA-specific IgE. After OVA challenge, PGD2, but not PGE2, substantially increased in the lungs of WT and TG mice with greater PGD2 increment in TG mice compared with WT mice. The numbers of eosinophils and lymphocytes in the bronchoalveolar lavage (BAL) fluid were significantly greater in TG mice than in WT mice on days 1 and 3 post-OVA challenge, whereas the numbers of macrophages and neutrophils were the same in both WT and TG mice. The levels of IL-4, IL-5, and eotaxin in BAL fluid were also significantly higher in TG mice than in WT mice, although the level of IFN-γ in the BAL fluid of TG mice was decreased compared with that in WT mice. Furthermore, lymphocytes isolated from the lungs of TG mice secreted less IFN-γ than those from WT mice, whereas IL-4 production was unchanged between WT and TG mice. Thus, overproduction of PGD2 caused an increase in the levels of Th2 cytokines and a chemokine, accompanied by the enhanced accumulation of eosinophils and lymphocytes in the lung. These results indicate that PGD2 plays an important role in late phase allergic reactions in the pathophysiology of bronchial asthma.
Fibroblast Growth Factor-2 Determines Severity of Joint Disease in Adjuvant-Induced Arthritis in Rats
Authors: Yamashita Akihisa , Yonemitsu Yoshikazu , Okano Shinji , Nakagawa Kazunori , Nakashima Yutaka , Irisa Takahiko , Iwamoto Yukihide , Nagai Yoshiyuki , Hasegawa Mamoru , Sueishi Katsuo
Published: April 2014

Rheumatoid arthritis (RA), a systemic inflammatory disease of unknown etiology, mainly affects synovial joints. Although angiogenic growth factors, including fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor (VEGF), may play a critical role in the development and progression of RA joint disease, little information is now available regarding their exact role in initiation and/or progression of RA. In this study, we show that both polypeptides were up-regulated in the rat joint synovial tissue of an adjuvant-induced model of arthritis (AIA), as well as human subjects with RA. FGF-2 overexpression via Sendai virus-mediated gene transfer significantly worsened clinical symptoms and signs of rat AIA, including hind paw swelling and radiological bone destruction, as well as histological findings based on inflammatory reaction, synovial angiogenesis, pannus formation, and osteocartilaginous destruction, associated with up-regulation of endogenous VEGF. FGF-2 gene transfer to non-AIA joints was without effect. These findings suggested that FGF-2 modulated disease progression, but did not affect initiation. Reverse experiments using anti-FGF-2-neutralizing rabbit IgG attenuated clinical symptoms and histopathological abnormalities of AIA joints. To our knowledge, this is the first report indicating direct in vivo evidence of disease-modulatory effects of FGF-2 in AIA, as probably associated with endogenous VEGF function. FGF-2 may prove to be a possible therapeutic target to treat subjects with RA.
Detection of Early Changes in Autoimmune T Cell Phenotype and Function Following Intravenous Administration of Type II Collagen in a TCR-Transgenic Model
Authors: Brand David D. , Myers Linda K. , Whittington Karen B. , Latham Kary A. , Stuart John M. , Kang Andrew H. , Rosloniec Edward F.
Published: April 2014

To study the phenotypic and functional changes in naive type II collagen (CII)-specific autoimmune T cells following a tolerogenic signal, a TCR-transgenic (Tg) mouse model of collagen-induced arthritis was developed. These Tg mice express an I-Aq-restricted CII (260–267)-specific TCR that confers severe accelerated autoimmune arthritis following immunization with CII. Despite the fact that >90% of the αβ T cells express the Tg, these mice can be rendered completely tolerant to the induction of arthritis by i.v. administration of 200 μg of CII. As early as 24 h after CII administration, CII-specific T cells demonstrated a decreased ability to proliferate in response to the CII immunodominant peptide and phenotypically altered the expression of L-selectin to CD62Llow and of phagocytic glycoprotein-1 to CD44high, expression levels consistent with the phenotype of memory T cells. In addition, they up-regulated the expression of the activation markers CD71 and CD69. Functionally, following tolerogenic stimulation, the CII-specific T cells produced similar levels of IL-2 in comparison to controls when challenged with CII peptide, however, by 48 h after exposure to tolerogen, IL-2 production dropped and was replaced by high levels of IL-10 and IL-4. Based on their production of Th2 cytokines, these data suggest that T regulatory cells expressing activation and memory markers are induced by the tolerogen and may exert their influence via cytokines to protect the animals from the induction of arthritis.
Immunostimulatory DNA Sequences Influence the Course of Adjuvant Arthritis
Authors: Ronaghy Arash , Prakken Berent J. , Takabayashi Kenji , Firestein Gary S. , Boyle David , Zvailfler Nathan J. , Roord Sarah T. A. , Albani Salvatore , Carson Dennis A. , Raz Eyal
Published: April 2014

Bacterial DNA is enriched in unmethylated CpG motifs that have been shown to activate the innate immune system. These immunostimulatory DNA sequences (ISS) induce inflammation when injected directly into joints. However, the role of bacterial DNA in systemic arthritis is not known. The purpose of the present experiments was to determine whether ISS contributes to the development of adjuvant arthritis in Lewis rats after intradermal injection of heat-killed Mycobacterium tuberculosis (Mtb). The results showed that Mtb DNA was necessary for maximal joint inflammation in adjuvant arthritis but could be replaced by synthetic ISS oligodeoxynucleotides. The arthritis-promoting effect of the Mtb DNA or of the ISS oligodeoxynucleotides correlated with an increased Th1 response to Mtb Ags, as measured by the production of IFN-γ and increased production of the osteoclast differentiation factor, receptor activator of NF-κB ligand (RANKL). The Mtb DNA did not enter the joints but dispersed to the bone marrow and spleen before the onset of systemic joint inflammation. Thus, adjuvant arthritis is a microbial DNA-dependent disease. In this model, we postulate that massive and prolonged activation of macrophages, dendritic cells, and osteoclast precursors in the bone marrow may prime the joints for the induction of inflammatory Th1 immune responses to Mtb Ags.
The Generation of Mature, Single-Positive Thymocytes In Vivo Is Dysregulated by CD69 Blockade or Overexpression
Authors: Nakayama Toshinori , Kasprowicz Deborah J. , Yamashita Masakatsu , Schubert Lisa A. , Gillard Geoffery , Kimura Motoko , Didierlaurent Arnaud , Koseki Haruhiko , Ziegler Steven F.
Published: April 2014

During development in the thymus, mature CD4+ or CD8+ cells are derived from immature CD4+CD8+ cells through a series of selection events. One of the hallmarks of this maturation process is the expression of CD69, which first appears on thymocytes as they begin positive selection. We have used blockade and overexpression of CD69 to determine the role of CD69 in thymocyte development. Blockade of CD69 led to a reduction in single-positive cells and a concomitant increase in double-positive cells in the thymus. Overexpression of a CD69 transgene in the thymus resulted in a dramatic increase in both CD8SP and CD4SP cells. Coexpression with a TCR transgene demonstrated that both positive and negative selection were enhanced by the increased levels of CD69 on thymocytes. Finally, mice overexpressing CD69 displayed a sharp reduction in the number of T cells in the spleen and lymph node. Taken as a whole, these data suggest the involvement of CD69 in the process of selection and maturation during the trafficking of thymocytes to the medulla.
NK Cell Activation by Dendritic Cells Is Dependent on LFA-1-Mediated Induction of Calcium-Calmodulin Kinase II: Inhibition by HIV-1 Tat C-Terminal Domain
Authors: Poggi Alessandro , Carosio Roberta , Spaggiari Grazia Maria , Fortis Claudio , Tambussi Giuseppe , Dell’Antonio Giacomo , Dal Cin Elena , Rubartelli Anna , Zocchi M. Raffaella
Published: April 2014

In this study, we show that binding to autologous dendritic cells (DC) induces a calcium influx in NK cells, followed by activation of the calcium-calmodulin kinase II (CAMKII), release of perforin and granzymes, and IFN-γ secretion. CAMKII is induced via LFA-1: indeed, oligomerization of LFA-1 leads to CAMKII induction in NK cells. Moreover, release of lytic enzymes and cytotoxic activity is strongly reduced by masking LFA-1 or by adding CAMKII inhibitors such as KN62 and KN93, at variance with the inactive compound KN92. NK cell-mediated lysis of DC and IFN-γ release by NK cells upon NK/DC contact are inhibited by exogenous HIV-1 Tat: the protein blocks calcium influx and impairs CAMKII activation elicited via LFA-1 in NK cells, eventually inhibiting degranulation. Experiments performed with synthetic, overlapping Tat-derived peptides showed that the C-terminal domain of the protein is responsible for inhibition. Finally, both KN62 and Tat reduced the extension of NK/DC contacts, possibly affecting NK cell granule polarization toward the target. These data provide evidence that exogenous Tat inhibits NK cell activation occurring upon contact with DC: this mechanism might contribute to the impairment of natural immunity in HIV-1 infection.
Ectopic Expression of the Murine Chemokines CCL21a and CCL21b Induces the Formation of Lymph Node-Like Structures in Pancreas, But Not Skin, of Transgenic Mice
Authors: Chen Shu-Cheng , Vassileva Galya , Kinsley David , Holzmann Sandra , Manfra Denise , Wiekowski Maria T. , Romani Nikolaus , Lira Sergio A.
Published: April 2014

The CC chemokine CCL21 is a potent chemoattractant for lymphocytes and dendritic cells in vitro. In the murine genome there are multiple copies of CCL21 encoding two CCL21 proteins that differ from each other by one amino acid at position 65 (either a serine or leucine residue). In this report, we examine the expression pattern and biological activities of both forms of CCL21. We found that although both serine and leucine forms are expressed in most tissues examined, the former was the predominant form in lymphoid organs while the latter was predominantly expressed in nonlymphoid organs. When expressed in transgenic pancreas, both forms of CCL21 were capable of inducing the formation of lymph node-like structures composed primarily of T and B cells and a few dendritic cells. Induction of lymph node-like structures by these CCL21 proteins, however, could not be reproduced in every tissue. For instance, no lymphocyte recruitment or accumulation was observed when CCL21 was overexpressed in the skin. We conclude that both forms of CCL21 protein are biologically equivalent in promoting lymphocyte recruitment to the pancreas, and that their ability to induce the formation of lymph node-like structures is dependent on the tissues in which they are expressed.
Central Nervous System Inflammation and Neurological Disease in Transgenic Mice Expressing the CC Chemokine CCL21 in Oligodendrocytes
Authors: Chen Shu-Cheng , Leach Michael W. , Chen Yuetian , Cai Xiao-Yan , Sullivan Lee , Wiekowski Maria , Dovey-Hartman B. J. , Zlotnik Albert , Lira Sergio A.
Published: April 2014

To study the biological role of the chemokine ligands CCL19 and CCL21, we generated transgenic mice expressing either gene in oligodendrocytes of the CNS. While all transgenic mice expressing CCL19 in the CNS developed normally, most (18 of 26) of the CCL21 founder mice developed a neurological disease that was characterized by loss of landing reflex, tremor, and ataxia. These neurological signs were observed as early as postnatal day 9 and were associated with weight loss and death during the first 4 wk of life. Microscopic examination of the brain and spinal cord of CCL21 transgenic mice revealed scattered leukocytic infiltrates that consisted primarily of neutrophils and eosinophils. Additional findings included hypomyelination, spongiform myelinopathy with evidence of myelin breakdown, and reactive gliosis. Thus, ectopic expression of the CC chemokine CCL21, but not CCL19, induced a significant inflammatory response in the CNS. However, neither chemokine was sufficient to recruit lymphocytes into the CNS. These observations are in striking contrast to the reported activities of these molecules in vitro and may indicate specific requirements for their biological activity in vivo.
CD4 T Cells Selected by Antigen Under Th2 Polarizing Conditions Favor an Elongated TCRα Chain Complementarity-Determining Region 3
Authors: Boyton Rosemary J. , Zaccai Nathan , Jones E. Yvonne , Altmann Daniel M.
Published: April 2014

The affinity of the MHC/peptide/TCR interaction is thought to be one factor determining the differentiation of CD4+ T cells into Th1 or Th2 phenotypes. To study whether CD4+ cells generated under conditions favoring Th1 or Th2 responses select structurally different TCRs, Th1 and Th2 clones and lines were generated from nonobese diabetic and nonobese diabetic H2-E transgenic mice against the peptides proteolipoprotein 56–70, glutamic acid decarboxylase65 524–543, and heat shock protein-60 peptides 168–186 and 248–264. Th1/Th2 polarization allowed the generation of clones and lines with fixed peptide specificity and class II restriction but differing in Th1/Th2 phenotype in which the impact on TCR selection and structure could be studied. The Th2 clones tended to use longer TCR complementarity-determining region (CDR)3α loops than their Th1 counterparts. This trend was confirmed by analyzing TCRα transcripts from Th1 and Th2 polarized, bulk populations. Molecular modeling of Th1- and Th2-derived TCRs demonstrated that Th2 CDR3α comprised larger side chain residues than Th1 TCRs. The elongated, bulky Th2 CDR3α loops may be accommodated at the expense of less optimal interactions between the MHC class II/peptide and other CDR loops of the TCR. We propose that CD4+ T cells selected from the available repertoire under Th2 polarizing conditions tend to have elongated TCR CDR3α loops predicted to alter TCR binding, reducing contact at other interfaces and potentially leading to impeded TCR triggering.
Complement C4 Is Protective for Lupus Disease Independent of C3
Authors: Einav Shirit , Pozdnyakova Olga O. , Ma Minghe , Carroll Michael C.
Published: April 2014

The role of complement C3 in mediating systemic lupus erythematosus (SLE) was examined using a double-knockout C3nullC4null Fas (CD95)-deficient mouse model. Results from this study reveal significant lymphadenopathy, splenomegaly, elevated titers of anti-nuclear Abs and anti-dsDNA Abs, an increased number of anti-dsDNA-producing cells in ELISPOT assay, as well as severe glomerulonephritis in the double-deficient mice. Based on these clinical, serological, and histological parameters, we find that autoimmune disease in the double-knockout group is similar in severity to that in C4null lpr mice, but not to that in C3null lpr mice. The development of severe SLE in the absence of both classical and alternative complement pathways suggests that it is the absence of C4, and not the presence of C3, that is critical in SLE pathogenesis. Thus, complement C4 provides an important protective role against the development of SLE.
Regulatory T Cells Overexpress a Subset of Th2 Gene Transcripts
Authors: Zelenika Diana , Adams Elizabeth , Humm Sue , Graca Luis , Thompson Sara , Cobbold Stephen P. , Waldmann Herman
Published: April 2014

There is now compelling evidence for subpopulations of CD4+ T cells whose role is to prevent immune pathology in both autoimmunity and transplantation. We have cloned CD4+ T cells against a male transplantation Ag that, unlike Th1 or Th2 clones, suppresses the rejection of male skin grafts and are therefore considered examples of regulatory T cells. We have identified, using serial analysis of gene expression, transcripts that are overexpressed in regulatory T cells compared with Th1 and Th2 clones. Some of these transcripts are increased in tolerated rather than rejecting skin grafts and in addition are expressed by the natural regulatory CD4+CD25+ subpopulation of naive mice. These genes include prepro-enkephalin, GM2 ganglioside activator protein, glucocorticoid-induced TNFR superfamily member 18, and integrin αEβ7. They seem to represent a subset of transcripts shared with Th2 cells, suggesting that transplantation tolerance and normal immunoregulation may represent a unique form of Th2-like differentiation.
CD25+CD4+ Regulatory T Cells Prevent Graft Rejection: CTLA-4- and IL-10-Dependent Immunoregulation of Alloresponses
Authors: Kingsley Cherry I. , Karim Mahzuz , Bushell Andrew R. , Wood Kathryn J.
Published: April 2014

Specific and selective immunological unresponsiveness to donor alloantigens can be induced in vivo. We have shown previously that CD25+CD4+ T cells from mice exhibiting long-term operational tolerance to donor alloantigens can regulate rejection of allogeneic skin grafts mediated by CD45RBhighCD4+ T cells. In this study, we wished to determine whether donor-specific regulatory cells can be generated during the induction phase of unresponsiveness, i.e., before transplantation. We provide evidence that pretreatment with anti-CD4 Ab plus a donor-specific transfusion generates donor-specific regulatory CD25+CD4+ T cells that can suppress rejection of skin grafts mediated by naive CD45RBhighCD4+ T cells. Regulatory cells were contained only in the CD25+ fraction, as equivalent numbers of CD25−CD4+ T cells were unable to regulate rejection. This pretreatment strategy led to increased expression of CD122 by the CD25+CD4+ T cells. Blockade of both the IL-10 and CTLA-4 pathways abrogated immunoregulation mediated by CD25+ T cells, suggesting that IL-10 and CTLA-4 are required for the functional activity of this population of immunoregulatory T cells. In clinical transplantation, the generation of regulatory T cells that could provide dynamic control of rejection responses is a possible route to permanent graft survival without the need for long-term immunosuppression.
Direct and Indirect Inhibition of Th1 Development by Progesterone and Glucocorticoids
Authors: Miyaura Hideki , Iwata Makoto
Published: April 2014

Progesterone may contribute to the maternal suppression of immunity to the fetus by modulating the Th1/Th2 balance. To clarify whether progesterone directly or indirectly affects T cell differentiation, we used two experimental systems with isolated T cells in vitro. In one system, isolated CD4+CD8+ thymocytes differentiated into Th1 and Th2 by two pulse stimulations with defined combinations of ionomycin and PMA followed by the treatment with IL-12, IL-4, and IL-2. In the second system, functional differentiation was induced in purified naive CD4 T cells with cytokines and Abs to CD3 and CD28. In both systems, progesterone added with cytokines suppressed Th1 development at concentrations associated with pregnancy, but enhanced the development of IL-10-producing Th2 cells. Because IL-10 is known to inhibit APC production of IL-12, Th1 development may be also suppressed indirectly by progesterone. However, progesterone failed to enhance IL-10 production in the absence of IL-12. The p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 inhibited Th1 development and enhanced Th2 development, as did progesterone, indicating that p38 MAPK and extracellular signal-regulated kinase pathways are involved in Th1 development. However, the progesterone effects may not be simply due to a modulation of MAPK activities, because the inhibitor did not significantly affect the development of IL-10-producing cells in the presence or absence of progesterone. Glucocorticoids exerted effects similar to those of progesterone on Th1/Th2 development even at lower concentrations. These results suggest that progesterone as well as glucocorticoids directly inhibit Th1 development and enhance Th2 development.
Peripheral Tolerance to a Nuclear Autoantigen: Dendritic Cells Expressing a Nuclear Autoantigen Lead to Persistent Anergic State of CD4+ Autoreactive T Cells After Proliferation
Authors: Kawahata Kimito , Misaki Yoshikata , Yamauchi Michiko , Tsunekawa Shinji , Setoguchi Keigo , Miyazaki Jun-ichi , Yamamoto Kazuhiko
Published: April 2014

It remains unknown why the T cell tolerance to nuclear autoantigens is impaired in systemic autoimmune diseases. To clarify this, we generated transgenic mice expressing OVA mainly in the nuclei (Ld-nOVA mice). When CD4+ T cells from DO11.10 mice expressing a TCR specific for OVA323–339 were transferred into Ld-nOVA mice, they were rendered anergic, but persisted in vivo for at least 3 mo. These cells expressed CD44high, CD45RBlow, and were generated after multiple cell divisions, suggesting that anergy is not the result of insufficient proliferative stimuli. Whereas dendritic cells (DCs) from Ld-nOVA (DCs derived from transgenic mice (TgDCs)), which present rather low amount of the self-peptide, efficiently induced proliferation of DO11.10 T cells, divided T cells stimulated in vivo by TgDCs exhibited a lower memory response than T cells stimulated in vitro by peptide-pulsed DCs. Furthermore, we found that repeated transfer of either TgDCs or DCs derived from wild-type mice pulsed with a lower concentration of OVA323–339 induced a lower response of DO11.10 T cells in Ag-free wild-type recipients than DCs derived from wild-type mice. These results suggest that peripheral tolerance to a nuclear autoantigen is achieved by continuous presentation of the self-peptide by DCs, and that the low expression level of the peptide might also be involved in the induction of hyporesponsiveness.
The Role of the IL-2 Pathway in Costimulation Blockade-Resistant Rejection of Allografts
Authors: Jones Thomas R. , Ha Jongwon , Williams Matthew A. , Adams Andrew B. , Durham Megan M. , Rees Phyllis A. , Cowan Shannon R. , Pearson Thomas C. , Larsen Christian P.
Published: April 2014

Blockade of the CD40 and CD28 costimulatory pathways significantly prolongs allograft survival; however, certain strains of mice (i.e., C57BL/6) are relatively resistant to the effects of combined CD40/CD28 blockade. We have previously shown that the costimulation blockade-resistant phenotype can be attributed to a subset of CD8+ T cells and is independent of CD4+ T cell-mediated help. Here we explore the role of the IL-2 pathway in this process using mAbs against the high affinity IL-2R, CD25, and IL-2 in prolonging skin allograft survival in mice receiving combined CD40/CD28 blockade. We have also investigated the effects of treatment on effector function by assessment of cytotoxicity and the generation of IFN-γ-producing cells in response to allogeneic stimulators as well as proliferation in an in vivo graft-vs-host disease model. We find that additional blockade of either CD25 or IL-2 significantly extends allograft survival beyond that in mice receiving costimulation blockade alone. This correlates with diminished frequencies of IFN-γ-producing allospecific T cells and reduced CTL activity. Anti-CD25 therapy also synergizes with CD40/CD28 blockade in suppressing proliferative responses. Interestingly, depletion of CD4+ T cells, but not CD8+ cells, prevents prolongation in allograft survival, suggesting an IL-2-independent role for regulation in extended survival.
Synergy Between CD40 Ligation and IL-4 on Fibroblast Proliferation Involves IL-4 Receptor Signaling
Authors: Atamas Sergei P. , Luzina Irina G. , Dai Heqiao , Wilt Susan G. , White Barbara
Published: April 2014

Fibrosis can be an undesired consequence of activated cellular immune responses. The purpose of this work was to determine whether CD40 ligation and the pro-fibrotic cytokine IL-4 interact in regulating fibroblast proliferation and collagen production, and, if so, the mechanisms used. This study found that the combination of IL-4 and ligation of CD40 on the fibroblast cell surface had synergistic effects in stimulating fibroblast proliferation. In contrast, CD40 ligation negated the inhibitory effects of IFN-γ on fibroblast proliferation. Western blotting analyses of fibroblast crude lysates revealed that a potential mechanism of the synergy between CD40 ligation and IL-4 was the phosphorylation of proteins at 130 kDa and, to a lesser degree, at 95, 85, and 75 kDa. Immunoprecipitation-Western blotting experiments showed that phosphorylation levels of IL-4Rα, Janus kinase 1, insulin receptor substrate 1, and insulin receptor substrate 2, factors with molecular mass close to the observed 130 kDa major phosphorylation band, increased in response to the combined CD40 ligation and IL-4 action. In contrast, there was no evidence that synergy was mediated by an increased expression of IL-4Rα chain, CD40, or the autocrine profibrotic cytokines IL-6 and TGF-β. These findings suggest that CD40-CD40 ligand contacts between fibroblasts and cells secreting IL-4 may promote the profibrotic effects of IL-4 by affecting signal transduction and reducing the anti-fibrotic effects of IFN-γ.
Functional Avidity of Tumor Antigen-Specific CTL Recognition Directly Correlates with the Stability of MHC/Peptide Multimer Binding to TCR
Authors: Dutoit Valérie , Rubio-Godoy Verena , Doucey Marie-Agnès , Batard Pascal , Liénard Danielle , Rimoldi Donata , Speiser Daniel , Guillaume Philippe , Cerottini Jean-Charles , Romero Pedro , Valmori Danila
Published: April 2014

Avidity of Ag recognition by tumor-specific T cells is one of the main parameters that determines the potency of a tumor rejection Ag. In this study we show that the relative efficiency of staining of tumor Ag-specific T lymphocytes with the corresponding fluorescent MHC class I/peptide multimeric complexes can considerably vary with staining conditions and does not necessarily correlate with avidity of Ag recognition. Instead, we found a clear correlation between avidity of Ag recognition and the stability of MHC class I/peptide multimeric complexes interaction with TCR as measured in dissociation kinetic experiments. These findings are relevant for both identification and isolation of tumor-reactive CTL.
Induction of MHC Class I Presentation of Exogenous Antigen by Dendritic Cells Is Controlled by CD4+ T Cells Engaging Class II Molecules in Cholesterol-Rich Domains
Authors: Machy Patrick , Serre Karine , Baillet Marjorie , Leserman Lee
Published: April 2014

We investigated interactions between CD4+ T cells and dendritic cells (DC) necessary for presentation of exogenous Ag by DC to CD8+ T cells. CD4+ T cells responding to their cognate Ag presented by MHC class II molecules of DC were necessary for induction of CD8+ T cell responses to MHC class I-associated Ag, but their ability to do so depended on the manner in which class II-peptide complexes were formed. DC derived from short-term mouse bone marrow culture efficiently took up Ag encapsulated in IgG FcR-targeted liposomes and stimulated CD4+ T cell responses to Ag-derived peptides associated with class II molecules. This CD4+ T cell-DC interaction resulted in expression by the DC of complexes of class I molecules and peptides from the Ag delivered in liposomes and permitted expression of the activation marker CD69 and cytotoxic responses by naive CD8+ T cells. However, while free peptides in solution loaded onto DC class II molecules could stimulate IL-2 production by CD4+ T cells as efficiently as peptides derived from endocytosed Ag, they could not stimulate induction of cytotoxic responses by CD8+ T cells to Ag delivered in liposomes into the same DC. Signals requiring class II molecules loaded with endocytosed Ag, but not free peptide, were inhibited by methyl-β-cyclodextrin, which depletes cell membrane cholesterol. CD4+ T cell signals thus require class II molecules in cholesterol-rich domains of DC for induction of CD8+ T cell responses to exogenous Ag by inducing DC to process this Ag for class I presentation.
1,25-Dihydroxyvitamin D3 Inhibits IFN-γ and IL-4 Levels During In Vitro Polarization of Primary Murine CD4+ T Cells
Authors: Staeva-Vieira Teodora P. , Freedman Leonard P.
Published: April 2014

Following their activation, naive CD4+ T cells can differentiate into one of two effector cell subsets, Th1 and Th2. These two subsets have different cytokine secretion patterns and thus mediate separate arms of the immune response. It has been established that the fat-soluble vitamin D3 metabolite 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and its nuclear receptor, the vitamin D receptor, play an important role in the immune system primarily through the transcriptional inhibition of cytokine genes that either are required for Th1 differentiation or are products of differentiated Th1 cells. Therefore, we wanted to test directly the ability of 1,25(OH)2D3 to alter the Th differentiation process. Our results indicate that 1,25(OH)2D3 inhibits not only the Th1 cytokine IFN-γ but also the Th2 cytokine IL-4 in naive CD62 ligand+CD4+ T cells during their in vitro polarization. This effect is most dramatic when the ligand is present from the onset of the differentiation process. If the ligand is added after the polarization has ensued, the inhibition is significantly diminished. In activated (CD62 ligand−CD4+) T cells, 1,25(OH)2D3 is still able to inhibit IFN-γ but has no effect on IL-4 production. Our results also indicate that inhibition of these two cytokines in naive cells by vitamin D receptor and its ligand is neither a result of a cell cycle block nor an inhibition of Th1 or Th2 transcription factor expression but, rather, at least in the case of Th2 differentiation, an attenuation of IL-4 transcription by the receptor.
Activation-Induced Nonresponsiveness: A Th-Dependent Regulatory Checkpoint in the CTL Response
Authors: Tham Ee Loon , Shrikant Protul , Mescher Matthew F.
Published: April 2014

CD8 T cells undergo autocrine IL-2-dependent proliferation upon TCR engagement and costimulation, but within 3–4 days, they become activation-induced nonresponsive (AINR) and display a split anergy. They can lyse targets and secrete IFN-γ but they cannot produce IL-2 in response to TCR ligation and costimulation, due at least in part to an inability to up-regulate mitogen-activated protein kinases and IL-2 mRNA. Exogenous IL-2 can drive continued proliferation of AINR cells and nonresponsiveness is reversed within 1–2 days so that Ag-driven proliferation can resume. Mitogen-activated protein kinases and IL-2 mRNA can again be up-regulated, but “rewiring” has occurred so that these events no longer depend upon costimulation; TCR engagement is sufficient. Development of AINR appears to be a normal part of the differentiation program of CD8 T cells, providing a regulatory checkpoint to convert the initial helper-independent response to one that depends upon CD4 T cell help for continued expansion of the effector CTL. Once permission is given, in the form of IL-2, to pass this checkpoint, the CTL can make a prolonged response to persisting Ag in the absence of further CD4 T cell help.