bluuebunny/crossref_metadata_2025 huggingface dataset:
The T Cell Receptor’s α-Chain Connecting Peptide Motif Promotes Close Approximation of the CD8 Coreceptor Allowing Efficient Signal Initiation
Authors: Mallaun Michel , Naeher Dieter , Daniels Mark A. , Yachi Pia P. , Hausmann Barbara , Luescher Immanuel F. , Gascoigne Nicholas R. J. , Palmer Ed
Published: April 2014

The CD8 coreceptor contributes to the recognition of peptide-MHC (pMHC) ligands by stabilizing the TCR-pMHC interaction and enabling efficient signaling initiation. It is unclear though, which structural elements of the TCR ensure a productive association of the coreceptor. The α-chain connecting peptide motif (α-CPM) is a highly conserved sequence of eight amino acids in the membrane proximal region of the TCR α-chain. TCRs lacking the α-CPM respond poorly to low-affinity pMHC ligands and are unable to induce positive thymic selection. In this study we show that CD8 participation in ligand binding is compromised in T lineage cells expressing mutant α-CPM TCRs, leading to a slight reduction in apparent affinity; however, this by itself does not explain the thymic selection defect. By fluorescence resonance energy transfer microscopy, we found that TCR-CD8 association was compromised for TCRs lacking the α-CPM. Although high-affinity (negative-selecting) pMHC ligands showed reduced TCR-CD8 interaction, low-affinity (positive-selecting) ligands completely failed to induce molecular approximation of the TCR and its coreceptor. Therefore, the α-CPM of a TCR is an important element in mediating CD8 approximation and signal initiation.
Misoprostol Impairs Female Reproductive Tract Innate Immunity against Clostridium sordellii
Authors: Aronoff David M. , Hao Yibai , Chung Jooho , Coleman Nicole , Lewis Casey , Peres Camila M. , Serezani Carlos H. , Chen Gwo-Hsiao , Flamand Nicolas , Brock Thomas G. , Peters-Golden Marc
Published: April 2014

Fatal cases of acute shock complicating Clostridium sordellii endometritis following medical abortion with mifepristone (also known as RU-486) used with misoprostol were reported. The pathogenesis of this unexpected complication remains enigmatic. Misoprostol is a pharmacomimetic of PGE2, an endogenous suppressor of innate immunity. Clinical C. sordellii infections were associated with intravaginal misoprostol administration, suggesting that high misoprostol concentrations within the uterus impair immune responses against C. sordellii. We modeled C. sordellii endometritis in rats to test this hypothesis. The intrauterine but not the intragastric delivery of misoprostol significantly worsened mortality from C. sordellii uterine infection, and impaired bacterial clearance in vivo. Misoprostol also reduced TNF-α production within the uterus during infection. The intrauterine injection of misoprostol did not enhance mortality from infection by the vaginal commensal bacterium Lactobacillus crispatus. In vitro, misoprostol suppressed macrophage TNF-α and chemokine generation following C. sordellii or peptidoglycan challenge, impaired leukocyte phagocytosis of C. sordellii, and inhibited uterine epithelial cell human β-defensin expression. These immunosuppressive effects of misoprostol, which were not shared by mifepristone, correlated with the activation of the Gs protein-coupled E prostanoid (EP) receptors EP2 and EP4 (macrophages) or EP4 alone (uterine epithelial cells). Our data provide a novel explanation for postabortion sepsis leading to death and also suggest that PGE2, in which production is exaggerated within the reproductive tract during pregnancy, might be an important causal determinant in the pathogenesis of more common infections of the gravid uterus.
Transient Local Depletion of Foxp3+ Regulatory T Cells during Recovery from Colitis via Fas/Fas Ligand-Induced Death
Authors: Reardon Colin , Wang Arthur , McKay Derek M.
Published: April 2014

Regulatory T cells (Tregs) play a fundamental role in regulating the immune system in health and disease. Considerable evidence exists demonstrating that transfer of Tregs can cure colitis and a variety of other inflammatory disorders. However, little is known about the effects of inflammation on resident Tregs. Mice (BALB/c or C57BL/6) treated with an intrarectal instillation of the haptenizing agent 2,4-dinitrobenzene sulfonic acid (DNBS) develop an acute inflammatory disease, the histopathology of which peaks at 3 days posttreatment and resolves spontaneously thereafter. In this study we demonstrate that DNBS (or oxazolone)-induced colitis causes a depletion of colonic Foxp3+ Tregs 8 days posttreatment, while the proportion of Foxp3+ cells in the ileum, mesenteric lymph nodes, and spleen remains unchanged. Replenishment of the colonic Treg population was associated with the reappearance of mucosal homing (α4β7+) CD4+Foxp3+ Tregs. Assessing the mechanism of local Treg depletion, we found no evidence to implicate cytokine-induced phenotypic switching in the Foxp3+ population or increased SMAD7 expression despite the essential role that TGF-β has in Foxp3+ Treg biology. Increased Fas ligand (FasL) expression was observed in the colon of colitic mice and in vitro stimulation with a Fas cross-linking Ab resulted in apoptosis of CD4+Foxp3+ but not CD4+Foxp3− cells. Furthermore, DNBS-induced colitis in Fas/FasL-deficient mice did not result in depletion of colonic Tregs. Finally, adoptively transferred synergic Fas−/− but not Fas+/+ Tregs were protected from depletion in the colon 8 days post-DNBS treatment, thus substantiating the hypothesis that inflammation-induced local depletion of Foxp3+ Tregs in the colon of mice occurs via Fas/FasL-mediated death.
The Neuropeptide Substance P Is a Critical Mediator of Burn-Induced Acute Lung Injury
Authors: Sio Selena Wei Shan , Puthia Manoj Kumar , Lu Jia , Moochhala Shabbir , Bhatia Madhav
Published: April 2014

The classical tachykinin substance P (SP) has numerous potent neuroimmunomodulatory effects on all kinds of airway functions. Belonging to a class of neuromediators targeting not only residential cells but also inflammatory cells, studying SP provides important information on the bidirectional linkage between how neural function affects inflammatory events and, in turn, how inflammatory responses alter neural activity. Therefore, this study aimed to investigate the effect of local burn injury on inducing distant organ pulmonary SP release and its relevance to lung injury. Our results show that burn injury in male BALB/c mice subjected to 30% total body surface area full thickness burn augments significant production of SP, preprotachykinin-A gene expression, which encodes for SP, and biological activity of SP-neurokinin-1 receptor (NK1R) signaling. Furthermore, the enhanced SP-NK1R response correlates with exacerbated lung damage after burn as evidenced by increased microvascular permeability, edema, and neutrophil accumulation. The development of heightened inflammation and lung damage was observed along with increased proinflammatory IL-1β, TNF-α, and IL-6 mRNA and protein production after injury in lung. Chemokines MIP-2 and MIP-1α were markedly increased, suggesting the active role of SP-induced chemoattractants production in trafficking inflammatory cells. More importantly, administration of L703606, a specific NK1R antagonist, 1 h before burn injury significantly disrupted the SP-NK1R signaling and reversed pulmonary inflammation and injury. The present findings show for the first time the role of SP in contributing to exaggerated pulmonary inflammatory damage after burn injury via activation of NK1R signaling.
Molecular Mimicry between Neurons and an Intracerebral Pathogen Induces a CD8 T Cell-Mediated Autoimmune Disease
Authors: Sanchez-Ruiz Monica , Wilden Laura , Müller Werner , Stenzel Werner , Brunn Anna , Miletic Hrvoje , Schlüter Dirk , Deckert Martina
Published: April 2014

To identify basic mechanisms of how infections may induce a neuron-specific autoimmune response, we generated mice expressing OVA as neuronal autoantigen under control of the neuron-specific enolase promoter (NSE-OVA mice). Intracerebral, but not systemic, infection with attenuated Listeria monocytogenes-secreting OVA induced an atactic-paretic neurological syndrome in NSE-OVA mice after bacterial clearance from the brain, whereas wild-type mice remained healthy. Immunization with attenuated Listeria monocytogenes-secreting OVA before intracerebral infection strongly increased the number of intracerebral OVA-specific CD8 T cells aggravating neurological disease. T cell depletion and adoptive transfer experiments identified CD8 T cells as decisive mediators of the autoimmune disease. Importantly, NSE-OVA mice having received OVA-specific TCR transgenic CD8 T cells developed an accelerated, more severe, and extended neurological disease. Adoptively transferred pathogenic CD8 T cells specifically homed to OVA-expressing MHC class I+ neurons and, corresponding to the clinical symptoms, ∼30% of neurons in the anterior horn of the spinal cord became apoptotic. Thus, molecular mimicry between a pathogen and neurons can induce a CD8 T cell-mediated neurological disease, with its severity being influenced by the frequency of specific CD8 T cells, and its induction, but not its symptomatic phase, requiring the intracerebral presence of the pathogen.
TNF-α Antagonism Generates a Population of Antigen-Specific CD4+CD25+ T Cells That Inhibit Protective Immunity in Murine Histoplasmosis
Authors: Deepe George S. , Gibbons Reta S.
Published: April 2014

In both humans and mice, treatment with TNF-α antagonists is associated with serious infectious complications including disseminated histoplasmosis. The mechanisms by which inhibition of endogenous TNF-α alter protective immunity remain obscure. Herein, we tested the possibility that neutralization of this cytokine triggered the emergence of T cells that dampen immunity. The lungs of mice given mAb to TNF-α contained a higher proportion and number of CD4+CD25+ cells than controls. This elevation was not observed in IFN-γ- or GM-CSF-deficient mice or in those given a high inoculum. Phenotypic analysis revealed that these cells lacked many of the characteristics of natural regulatory T cells, including Foxp3. CD4+CD25+ cells from TNF-α-neutralized mice suppressed Ag-specific, but not nonspecific, responses in vitro. Elimination of CD25+ cells in vivo restored protective immunity in mice given mAb to TNF-α and adoptive transfer of CD4+CD25+ cells inhibited immunity. In vitro and in vivo, the suppressive effect was reversed by mAb to IL-10. Thus, neutralization of TNF-α is associated with the induction of a population of regulatory T cells that alter protective immunity in an Ag-specific manner to Histoplasma capsulatum.
The Proinflammatory Cytokine Response toChlamydia trachomatisElementary Bodies in Human Macrophages Is Partly Mediated by a Lipoprotein, the Macrophage Infectivity Potentiator, through TLR2/TLR1/TLR6 and CD14
Authors: Bas Sylvette , Neff Laurence , Vuillet Madeleine , Spenato Ursula , Seya Tsukasa , Matsumoto Misako , Gabay Cem
Published: April 2014

Chlamydiae components and signaling pathway(s) responsible for the production of proinflammatory cytokines by human monocytes/macrophages are not clearly identified. To this aim, Chlamydia trachomatis-inactivated elementary bodies (EB) as well as the following seven individual Ags were tested for their ability to induce the production of proinflammatory cytokines by human monocytes/macrophages and THP-1 cells: purified LPS, recombinant heat shock protein (rhsp)70, rhsp60, rhsp10, recombinant polypeptide encoded by open reading frame 3 of the plasmid (rpgp3), recombinant macrophage infectivity potentiator (rMip), and recombinant outer membrane protein 2 (rOmp2). Aside from EB, rMip displayed the highest ability to induce release of IL-1β, TNF-α, IL-6, and IL-8. rMip proinflammatory activity could not be attributed to Escherichia coli LPS contamination as determined by the Limulus Amoebocyte lysate assay, insensitivity to polymyxin B (50 μg/ml), and different serum requirement. We have recently demonstrated that Mip is a “classical” bacterial lipoprotein, exposed at the surface of EB. The proinflammatory activity of EB was significantly attenuated in the presence of polyclonal Ab to rMip. Native Mip was able to induce TNF-α and IL-8 secretion, whereas a nonlipidated C20A rMip variant was not. Proinflammatory activity of rMip was unaffected by heat or proteinase K treatments but was greatly reduced by treatment with lipases, supporting a role of lipid modification in this process. Stimulating pathways appeared to involve TLR2/TLR1/TLR6 with the help of CD14 but not TLR4. These data support a role of Mip lipoprotein in pathogenesis of C. trachomatis-induced inflammatory responses.
Urokinase-Type Plasminogen Activator Plays Essential Roles in Macrophage Chemotaxis and Skeletal Muscle Regeneration
Authors: Bryer Scott C. , Fantuzzi Giamila , Van Rooijen Nico , Koh Timothy J.
Published: April 2014

Although macrophages are thought to play important roles in tissue repair, the molecular mechanisms involved remain to be elucidated. Mice deficient in urokinase-type plasminogen activator (uPA−/−) exhibit decreased accumulation of macrophages following muscle injury and severely impaired muscle regeneration. We tested whether macrophage-derived uPA plays essential roles in macrophage chemotaxis and skeletal muscle regeneration. Macrophage uPA was required for chemotaxis, even when invasion through matrix was not necessary. The mechanism by which macrophage uPA promoted chemotaxis was independent of receptor binding but appeared to depend on proteolytic activity. Exogenous uPA restored chemotaxis to uPA−/− macrophages and rescued muscle regeneration in uPA−/− mice. Macrophage depletion in wild-type (WT) mice using clodronate liposomes resulted in impaired muscle regeneration, confirming that macrophages are required for efficient healing. Furthermore, transfer of WT bone marrow cells to uPA−/− mice restored macrophage accumulation and muscle regeneration. In this rescue, transferred WT cells appeared to contribute to IGF-1 expression but did not fuse to regenerating fibers. These data indicate that WT leukocytes, including macrophages, that express uPA were sufficient to rescue muscle regeneration in uPA−/− mice. Overall, the results indicate that uPA plays a fundamental role in macrophage chemotaxis and that macrophage-derived uPA promotes efficient muscle regeneration.
Cutting Edge: Cooperation of IPS-1- and TRIF-Dependent Pathways in Poly IC-Enhanced Antibody Production and Cytotoxic T Cell Responses
Authors: Kumar Himanshu , Koyama Shohei , Ishii Ken J. , Kawai Taro , Akira Shizuo
Published: April 2014

Double-stranded RNA, polyriboinosinic-polyribocytidylic acid (poly IC), acts as an adjuvant that enhances adaptive immune responses. The recognition of poly IC is mediated by endosomal TLR3 and cytoplasmic RNA helicase melanoma differentiation-associated gene 5 (Mda5), which signal through the adaptors Toll/IL-1R domain-containing adaptor inducing IFN-β (TRIF) and IFN-β promoter stimulator-1 (IPS-1), respectively. However, the contribution of these pathways to the adjuvant effects of poly IC remains unclear. In this study, we found that poly IC-enhanced, Ag-specific Ab production was severely decreased in IPS-1-deficient mice but not in TRIF-deficient mice. However, the double deficiency resulted in a complete loss of Ab production. Furthermore, Ag-specific CD8+ T cell expansion was reduced in both IPS-1-deficient and TRIF-deficient mice and entirely abrogated in the doubly deficient mice. Taken together, these results demonstrate that the adjuvant effects of poly IC require a cooperative activation of TLR and cytoplasmic RNA helicase pathways.
Cutting Edge: Anti-Tumor Necrosis Factor Therapy in Rheumatoid Arthritis Inhibits Memory B Lymphocytes via Effects on Lymphoid Germinal Centers and Follicular Dendritic Cell Networks
Authors: Anolik Jennifer H. , Ravikumar Rajan , Barnard Jennifer , Owen Teresa , Almudevar Anthony , Milner Eric C. B. , Miller Chase H. , Dutcher Paul O. , Hadley James A. , Sanz Iñaki
Published: April 2014

Rheumatoid arthritis (RA) is mediated by a proinflammatory cytokine network with TNF at its apex. Accordingly, drugs that block TNF have demonstrated significant efficacy in the treatment of RA. A great deal of experimental evidence also strongly implicates B cells in the pathogenesis of RA. Yet, it remains unclear whether these two important players and the therapies that target them are mechanistically linked. In this study we demonstrate that RA patients on anti-TNF (etanercept) display a paucity of follicular dendritic cell networks and germinal center (GC) structures accompanied by a reduction in CD38+ GC B cells and peripheral blood memory B cell lymphopenia compared with healthy controls and RA patients on methotrexate. This study provides initial evidence in humans to support the notion that anti-TNF treatment disrupts GC reactions at least in part via effects on follicular dendritic cells.
Plasmodium Infection and Endotoxic Shock Induce the Expansion of Regulatory Dendritic Cells
Authors: Wong Kurt A. , Rodriguez Ana
Published: April 2014

During an acute Plasmodium infection, uncontrolled proinflammatory responses can cause morbidity and mortality. Regulation of this response is required to prevent immunopathology. We therefore decided to investigate a recently characterized subset of regulatory dendritic cells (DCs) that expresses low levels of CD11c and high levels of CD45RB. During a Plasmodium yoelii infection, these regulatory CD11clowCD45RBhigh DCs become the prevalent CD11c-expressing cells in the spleen, overtaking the conventional CD11chigh DCs. Furthermore, the regulatory CD11clowCD45RBhigh DCs induce IL-10-expressing CD4 T cells. A similar change in splenic DC subsets is seen when mice are injected with sublethal doses of LPS, suggesting that shifting the splenic DC subsets in favor of regulatory CD11clowCD45RBhigh DCs can be triggered solely by a high inflammatory stimulus. This is the first time regulatory DCs have been observed in a natural immune response to an infectious disease or endotoxic shock.
Estradiol Acts Directly on Bone Marrow Myeloid Progenitors to Differentially Regulate GM-CSF or Flt3 Ligand-Mediated Dendritic Cell Differentiation
Authors: Carreras Esther , Turner Sean , Paharkova-Vatchkova Vladislava , Mao Allen , Dascher Christopher , Kovats Susan
Published: April 2014

Estrogen receptor (ER) ligands modulate hemopoiesis and immunity in the normal state, during autoimmunity, and after infection or trauma. Dendritic cells (DC) are critical for initiation of innate and adaptive immune responses. We demonstrate, using cytokine-driven culture models of DC differentiation, that 17-β-estradiol exerts opposing effects on differentiation mediated by GM-CSF and Flt3 ligand, the two cytokines that regulate DC differentiation in vivo. We also show that estradiol acts on the same highly purified Flt3+ myeloid progenitors (MP) to differentially regulate the DC differentiation in each model. In GM-CSF-supplemented cultures initiated from MP, physiological amounts of estradiol promoted differentiation of Langerhans-like DC. Conversely, in Flt3 ligand-supplemented cultures initiated from the same MP, estradiol inhibited cell survival in a dose-dependent manner, thereby decreasing the yield of plasmacytoid and conventional myeloid and lymphoid DC. Experiments with bone marrow cells from ER-deficient mice and the ER antagonist ICI182,780 showed that estradiol acted primarily via ERα to regulate DC differentiation. Thus, depending on the cytokine environment, pathways of ER signaling and cytokine receptor signaling can differentially interact in the same Flt3+ MP to regulate DC development. Because the Flt3 ligand-mediated differentiation pathway is important during homeostasis, and GM-CSF-mediated pathways are increased by inflammation, our data suggest that endogenous or pharmacological ER ligands may differentially affect DC development during homeostasis and disease, with consequent effects on DC-mediated immunity.
The Effect of Deleting p110δ on the Phenotype and Function of PTEN-Deficient B Cells
Authors: Janas Michelle L. , Hodson Daniel , Stamataki Zania , Hill Sue , Welch Katie , Gambardella Laure , Trotman Lloyd C. , Pandolfi Pier Paolo , Vigorito Elena , Turner Martin
Published: April 2014

Control of the intracellular levels of phosphatidylinositol-(3, 4, 5)-trisphosphate by PI3K and phosphatase and tensin homolog (PTEN) is essential for B cell development and differentiation. Deletion of the PI3K catalytic subunit p110δ leads to a severe reduction in B1 and marginal zone (MZ) B cells, whereas deletion of PTEN results in their expansion. We have examined the relationship between these two molecules by generating mice with a B cell-specific deletion of PTEN (PTENB) and a concurrent germline deletion of p110δ. The expanded B1 cell population of PTENB mice was reduced to normal levels in PTENB/p110δ mutant mice, indicating a critical role for the p110δ isoform in the expansion of B1 cells. However, numbers of MZ B cells in the PTENB/p110δ mutants was intermediate between wild-type and PTENB-deficient mice, suggesting an additional role for other PI3K catalytic isoforms in MZ differentiation. Furthermore, the defective class switch recombination in PTENB B cells was only partially reversed in PTENB/p110δ double mutant B cells. These results demonstrate an epistatic relationship between p110δ and PTEN. In addition, they also suggest that additional PI3K catalytic subunits contribute to B cell development and function.
Accumulation of Effector CD4 T Cells during Type 2 Immune Responses Is Negatively Regulated by Stat6
Authors: King Susan B. S. , Knorn Anna M. , Ohnmacht Caspar , Voehringer David
Published: April 2014

Th2 cells are important effector cells during allergic disorders and parasite infections. Efficient differentiation of Th2 cells requires signaling via the IL-4R and the transcription factor Stat6. Stat6 is further implicated in Th2 cell recruitment to the lung and might be required for the survival of memory Th2 cells. We analyzed the role of Stat6 in T cell expansion, survival, and recruitment to the lung using competitive adoptive transfer experiments and infection with the helminth parasite Nippostrongylus brasiliensis. Stat6 was not required in T cells or other cell types for recruitment of in vivo-generated Th2 cells to the lung. Functional analysis of Th2 memory cells revealed that Stat6 signaling in CD4 T cells was dispensable for memory cell generation, expansion, and cytokine secretion. However, Stat6-deficient T cells survived better than wild-type T cells, resulting in higher accumulation in the bronchoalveolar lavage, lung, and lymph nodes. This demonstrates that effector T cell expansion is negatively controlled by a novel Stat6-dependent mechanism which probably serves to limit the number of effector T cells during the acute phase of the immune response and thereby lowers the risk of bystander toxicity against healthy tissues.
ICOS Controls the Pool Size of Effector-Memory and Regulatory T Cells
Authors: Burmeister Yvonne , Lischke Timo , Dahler Anja C. , Mages Hans Werner , Lam Kong-Peng , Coyle Anthony J. , Kroczek Richard A. , Hutloff Andreas
Published: April 2014

ICOS is an important regulator of T cell effector function. ICOS-deficient patients as well as knockout mice show severe defects in T cell-dependent B cell responses. Several in vitro and in vivo studies attributed this phenomenon to impaired up-regulation of cell surface communication molecules and cytokine synthesis by ICOS-deficient T cells. However, we now could show with Ag-specific T cells in a murine adoptive transfer system that signaling via ICOS does not significantly affect early T cell activation. Instead, ICOS substantially contributes to the survival and expansion of effector T cells upon local challenge with Ag and adjuvant. Importantly, the observed biological function of ICOS also extends to FoxP3+ regulatory T cells, as can be observed after systemic Ag delivery without adjuvant. In line with these findings, absence of ICOS under homeostatic conditions of nonimmunized mice leads to a reduced number of both effector-memory and FoxP3+ regulatory T cells. Based on these results, we propose a biological role for ICOS as a costimulatory, agonistic molecule for a variety of effector T cells with differing and partly opposing functional roles. This concept may reconcile a number of past in vivo studies with seemingly contradictory results on ICOS function.
Essential Role of CD8+CD122+ Regulatory T Cells in the Recovery from Experimental Autoimmune Encephalomyelitis
Authors: Lee Young-Ho , Ishida Yoshiyuki , Rifa’i Muhaimin , Shi Zhe , Isobe Ken-ichi , Suzuki Haruhiko
Published: April 2014

Experimental autoimmune encephalomyelitis (EAE) is one of the best-documented animal models of autoimmune disease. We examined the role of CD8+CD122+ regulatory T cells, which we previously identified as naturally occurring regulatory T cells that effectively regulate CD8+ T cells, in EAE. Depletion of CD8+CD122+ regulatory T cells by in vivo administration of anti-CD122 mAb resulted in persistent EAE symptoms. Transfer of CD8+CD122+ regulatory T cells into EAE mice at the peak EAE score clearly improved symptoms, indicating an important role of CD8+CD122+ regulatory T cells in the recovery phase of EAE. This was further confirmed by an increase and a decrease in the number of infiltrating T cells in the CNS and T cell cytokine production in mice that were depleted of or complemented with CD8+CD122+ cells. Furthermore, transfer of preactivated CD8+CD122+ regulatory T cells resulted in diminished EAE symptoms, especially in the recovery phase of EAE. These results elucidate the essential role of CD8+CD122+ regulatory T cells in the recovery phase of EAE and suggest the preventive effect of preactivated CD8+CD122+ regulatory T cells for EAE.
CD4+ T Cells Recognizing a Single Self-Peptide Expressed by APCs Induce Spontaneous Autoimmune Arthritis
Authors: Rankin Andrew L. , Reed Amy J. , Oh Soyoung , Cozzo Picca Cristina , Guay Heath M. , Larkin Joseph , Panarey Laura , Aitken Malinda K. , Koeberlein Brigitte , Lipsky Peter E. , Tomaszewski John E. , Naji Ali , Caton Andrew J.
Published: April 2014

We have examined processes leading to the spontaneous development of autoimmune inflammatory arthritis in transgenic mice containing CD4+ T cells targeted to a nominal Ag (hemagglutinin (HA)) and coexpressing HA driven by a MHC class II promoter. Despite being subjected to multiple tolerance mechanisms, autoreactive CD4+ T cells accumulate in the periphery of these mice and promote systemic proinflammatory cytokine production. The majority of mice spontaneously develop inflammatory arthritis, which is accompanied by an enhanced regional immune response in lymph nodes draining major joints. Arthritis development is accompanied by systemic B cell activation; however, neither B cells nor Ab is required for arthritis development, since disease develops in a B cell-deficient background. Moreover, arthritis also develops in a recombinase activating gene-deficient background, indicating that the disease process is driven by CD4+ T cells recognizing the neo-self HA Ag. These findings show that autoreactive CD4+ T cells recognizing a single self-Ag, expressed by systemically distributed APCs, can induce arthritis via a mechanism that is independent of their ability to provide help for autoantibody production.
Alveolar Epithelial Type II Cells Induce T Cell Tolerance to Specific Antigen
Authors: Lo Bernice , Hansen Soren , Evans Kathy , Heath John K. , Wright Jo Rae
Published: April 2014

The lungs face the immunologic challenge of rapidly eliminating inhaled pathogens while maintaining tolerance to innocuous Ags. A break in this immune homeostasis may result in pulmonary inflammatory diseases, such as allergies or asthma. The observation that alveolar epithelial type II cells (Type II) constitutively express the class II MHC led us to hypothesize that Type II cells play a role in the adaptive immune response. Because Type II cells do not express detectable levels of the costimulatory molecules CD80 and CD86, we propose that Type II cells suppress activation of naive T cells. Purified murine Type II cells were unable to activate T cells to specific Ag or in an alloreactive assay. Although IFN-γ treatment up-regulated class II MHC expression, it did not alter the ability of the Type II cells to activate T cells. Rather, the Type II cells were able to suppress T cells from subsequent activation to specific Ag in an Ag-dependent manner. Priming T cells with Type II cells and Ag resulted in T cells that were suppressed to further activation, even after removal from the Type II cells. Thus, Type II cells of the lung help tolerize T cells to nonpathogenic environmental Ags.
Pregnancy Allows the Transfer and Differentiation of Fetal Lymphoid Progenitors into Functional T and B Cells in Mothers
Authors: Khosrotehrani Kiarash , Leduc Michèle , Bachy Véronique , Huu Sau Nguyen , Oster Michèle , Abbas Aicha , Uzan Serge , Aractingi Sélim
Published: April 2014

T lymphocytes of fetal origin found in maternal circulation after gestation have been reported as a possible cause for autoimmune diseases. During gestation, mothers acquire CD34+CD38+ cells of fetal origin that persist decades. In this study, we asked whether fetal T and B cells could develop from these progenitors in the maternal thymus and bone marrow during and after gestation. RAG−/−-deficient female mice (Ly5.2) were mated to congenic wild-type Ly5.1 mice (RAG+/+). Fetal double-positive T cells (CD4+CD8+) with characteristic TCR and IL-7R expression patterns could be recovered in maternal thymus during the resulting pregnancies. We made similar observations in the thymus of immunocompetent mothers. Such phenomenon was observed overall in 12 of 68 tested mice compared with 0 of 51 controls (p = 0.001). T cells could also be found in maternal spleen and produced IFN-γ in the presence of an allogenic or an Ag-specific stimulus. Similarly, CD19+IgM+ fetal B cells as well as plasma Igs could be found in maternal RAG−/− bone marrow and spleen after similar matings. Our results suggest that during gestation mothers acquire fetal lymphoid progenitors that develop into functional T cells. This fetal cell microchimerism may have a direct impact on maternal health.
CD22 Regulates Time Course of Both B Cell Division and Antibody Response
Authors: Onodera Taishi , Poe Jonathan C. , Tedder Thomas F. , Tsubata Takeshi
Published: April 2014

Because pathogens induce infectious symptoms in a time-dependent manner, a rapid immune response is beneficial for defending hosts from pathogens, especially those inducing acute infectious diseases. However, it is largely unknown how the time course of immune responses is regulated. In this study, we demonstrate that B cells deficient in the inhibitory coreceptor CD22 undergo accelerated cell division after Ag stimulation, resulting in rapid generation of plasma cells and Ab production. This finding indicates that CD22 regulates the time course of B cell responses and suggests that CD22 is a good target to shorten the time required for Ab production, thereby augmenting host defense against acute infectious diseases as “universal vaccination.”
Implication of Matrix Metalloproteinase 7 and the Noncanonical Wingless-Type Signaling Pathway in a Model of Kidney Allograft Tolerance Induced by the Administration of Anti-Donor Class II Antibodies
Authors: Jovanovic Vojislav , Dugast Anne-Sophie , Heslan Jean-Marie , Ashton-Chess Joanna , Giral Magali , Degauque Nicolas , Moreau Anne , Pallier Annaick , Chiffoleau Elise , Lair David , Usal Claire , Smit Helga , Vanhove Bernard , Soulillou Jean-Paul , Brouard Sophie
Published: April 2014

In rats, tolerance to MHC-incompatible renal allografts can be induced by the administration of anti-donor class II Abs on the day of transplantation. In this study we explored the mechanisms involved in the maintenance phase of this tolerance by analyzing intragraft gene expression profiles by microarray in long-term accepted kidneys. Comparison of the gene expression patterns of tolerated to syngeneic kidneys revealed 5,954 differentially expressed genes (p < 0.05). Further analysis of this gene set revealed a key role for the wingless-type (WNT) signaling pathway, one of the pivotal pathways involved in cell regulation that has not yet been implicated in transplantation. Several genes within this pathway were significantly up-regulated in the tolerated grafts, particularly matrix metalloproteinase 7 (MMP7; fold change > 40). Analysis of several other pathway-related molecules indicated that MMP7 overexpression was the result of the noncanonical WNT signaling pathway. MMP7 expression was restricted to vascular smooth muscle cells and was specific to anti-class II Ab-induced tolerance, as it was undetectable in other models of renal and heart transplant tolerance and chronic rejection induced across the same strain combination. These results suggest a novel role for noncanonical WNT signaling in maintaining kidney transplant tolerance in this model, with MMP7 being a key target. Determining the mechanisms whereby MMP7 contributes to transplant tolerance may help in the development of new strategies to improve long-term graft outcome.
Suppression of Mature Dendritic Cell Function by Regulatory T Cells In Vivo Is Abrogated by CD40 Licensing
Authors: Hänig Jens , Lutz Manfred B.
Published: April 2014

The priming of CD4+ effector T cells (Teff) in vivo is induced by mature dendritic cells (DC) and controlled by CD4+CD25+Foxp3+ regulatory T cells (Treg). It remains unclear,however, how Teff priming vs Treg suppression are regulated during Ag presentation by DC in secondary lymphoid organs at the simultaneous presence of Teff and Treg. In this study, we used an peptide-specific DO11.10 TCR-transgenic adoptive transfer model to follow the Teff priming kinetics and the mechanisms of suppression by Treg. Treg activation was slower as compared with Teff and could not influence the early Teff expansion but limited the Teff response leading to lower Teff numbers in the memory phase. DC-Treg cell contacts remained unaltered during suppression by Treg and led to a down-regulation of the costimulatory molecules CD80, CD86, PD-L1, and PD-L2 but not MHC II, CD40, ICOS-L, or CD70 from the mature DC surface. This effect was observed only after DC maturation with TNF or LPS but not after additional CD40 licensing. Together, our data indicate that Treg suppression against nonself Ags in vivo occurs delayed due to the slower Treg response, is mediated to a large extent through DC modulation, but is controlled by the type of DC maturation.
TGF-β Inhibits IL-2 Production and Promotes Cell Cycle Arrest in TCR-Activated Effector/Memory T Cells in the Presence of Sustained TCR Signal Transduction
Authors: Das Lopamudra , Levine Alan D.
Published: April 2014

TGF-β signaling is critical for controlling naive T cell homeostasis and differentiation; however, the biological and biochemical changes induced by TGF-β in effector/memory T cells are poorly defined. We show that although TGF-β inhibits effector/memory peripheral blood T lymphoblast proliferation and IL-2 production, the intensity and kinetics for TCR-induced global tyrosine phosphorylation are markedly increased compared with that in untreated cells or naive T cells. After TCR ligation, tyrosine phosphorylation of proximal tyrosine kinases and docking proteins like linker for activation of T cells is maintained for >30 min in TGF-β-primed cells compared with untreated cells where phosphorylation of these targets returned to basal levels by 10 min. Extended phosphorylation of linker for activation of T cells in treated peripheral blood T selectively prolongs ERK 1/2 signaling and phospholipase C-γ1 activation leading to increased Ca2+ flux. A kinase/phosphatase imbalance could not account for extended phosphorylation as CD45R, SHP-1, and SHP-2 expression remains unaltered. The contradiction between prolonged signal transduction and inhibition of proliferation is partially explained by the observation that TGF-β priming results in ERK 1/2-independent p21 induction and decreased cyclin D1 expression leading to accumulation of T cells in G0/G1 phases of the cell cycle and cell cycle arrest. Despite inhibition of T cell function by TGF-β priming, TCR and cytokine signaling pathways are intact and selectively extended, suggesting that suppression in the effector/memory T cell is mediated by reprogramming signal transduction, rather than its inhibition as in the naive T cell.
Homeostasis of the Naive CD4+ T Cell Compartment during Aging
Authors: Kilpatrick Ryan D. , Rickabaugh Tammy , Hultin Lance E. , Hultin Patricia , Hausner Mary Ann , Detels Roger , Phair John , Jamieson Beth D.
Published: April 2014

Despite thymic involution, the number of naive CD4+ T cells diminishes slowly during aging, suggesting considerable peripheral homeostatic expansion of these cells. To investigate the mechanisms behind, and consequences of, naive CD4+ T cell homeostasis, we evaluated the age-dependent dynamics of the naive CD4+ T cell subsets CD45RA+CD31+ and CD45RA+CD31−. Using both a cross-sectional and longitudinal study design, we measured the relative proportion of both subsets in individuals ranging from 22 to 73 years of age and quantified TCR excision circle content within those subsets as an indicator of proliferative history. Our findings demonstrate that waning thymic output results in a decrease in CD45RA+CD31+ naive CD4+ T cells over time, although we noted considerable individual variability in the kinetics of this change. In contrast, there was no significant decline in the CD45RA+CD31− naive CD4+ T cell subset due to extensive peripheral proliferation. Our longitudinal data are the first to demonstrate that the CD45RA+CD31+CD4+ subset also undergoes some in vivo proliferation without immediate loss of CD31, resulting in an accumulation of CD45RA+CD31+ proliferative offspring. Aging was associated with telomere shortening within both subsets, raising the possibility that accumulation of proliferative offspring contributes to senescence of the naive CD4+ T cell compartment in the elderly. In contrast, we observed retention of clonal TCR diversity despite peripheral expansion, although this analysis did not include individuals over 65 years of age. Our results provide insight into naive CD4+ T cell homeostasis during aging that can be used to better understand the mechanisms that may contribute to immunosenescence within this compartment.
Kinetic and Mechanistic Requirements for Helping CD8 T Cells
Authors: Agnellini Paola , Wiesel Melanie , Schwarz Katrin , Wolint Petra , Bachmann Martin F. , Oxenius Annette
Published: April 2014

The requirements for the generation of fully competent long-lived memory CD8 T cells and in particular the role and the mechanisms of help from CD4 T cells remain ill-defined. Memory CD8 T cells generated in the absence of CD4 T cell help often have an impaired recall proliferation and are thus unable to confer protection against certain pathogens. However, the timing and the mechanisms involved in the delivery of help are still unclear and differ between various experimental systems. In this study, we investigated the role of CD4 T help in generating memory CD8 T cells in a defined heterologous prime-boost system, consisting of priming with replication incompetent virus-like particles and challenge with recombinant vaccinia virus, both sharing only a common lymphocytic choriomeningitis virus-derived CD8 T cell epitope. We show in this system that delivery of help is only essential during the challenge phase for recall proliferation of memory CD8 T cells. Furthermore, we show that generation of proliferation-competent memory CD8 T cells is independent of CD40 and CCR5 and that in vivo IL-2 supplementation neither during priming nor during challenge was able to rescue recall proliferation of “unhelped” memory CD8 T cells.
Th2 Lymphoproliferative Disorder of Lat
Y136F Mutant Mice Unfolds Independently of TCR-MHC Engagement and Is Insensitive to the Action of Foxp3+ Regulatory T Cells
Authors: Wang Ying , Kissenpfennig Adrien , Mingueneau Michael , Richelme Sylvie , Perrin Pierre , Chevrier Stéphane , Genton Céline , Lucas Bruno , DiSanto James P. , Acha-Orbea Hans , Malissen Bernard , Malissen Marie
Published: April 2014

Mutant mice where tyrosine 136 of linker for activation of T cells (LAT) was replaced with a phenylalanine (LatY136F mice) develop a fast-onset lymphoproliferative disorder involving polyclonal CD4 T cells that produce massive amounts of Th2 cytokines and trigger severe inflammation and autoantibodies. We analyzed whether the LatY136F pathology constitutes a bona fide autoimmune disorder dependent on TCR specificity. Using adoptive transfer experiments, we demonstrated that the expansion and uncontrolled Th2-effector function of LatY136F CD4 cells are not triggered by an MHC class II-driven, autoreactive process. Using Foxp3EGFP reporter mice, we further showed that nonfunctional Foxp3+ regulatory T cells are present in LatY136F mice and that pathogenic LatY136F CD4 T cells were capable of escaping the control of infused wild-type Foxp3+ regulatory T cells. These results argue against a scenario where the LatY136F pathology is primarily due to a lack of functional Foxp3+ regulatory T cells and suggest that a defect intrinsic to LatY136F CD4 T cells leads to a state of TCR-independent hyperactivity. This abnormal status confers LatY136F CD4 T cells with the ability to trigger the production of Abs and of autoantibodies in a TCR-independent, quasi-mitogenic fashion. Therefore, despite the presence of autoantibodies causative of severe systemic disease, the pathological conditions observed in LatY136F mice unfold in an Ag-independent manner and thus do not qualify as a genuine autoimmune disorder.
Antigen Release Kinetics in the Phagosome Are Critical to Cross-Presentation Efficiency
Authors: Howland Shanshan W. , Wittrup K. Dane
Published: April 2014

Cross-presentation of exogenous Ags in MHC class I molecules by dendritic cells is the underlying basis for many developing immunotherapies and vaccines. In the phagosome-to-cytosol pathway, Ags in phagocytosed particles must become freely soluble before being exported to the cytosol, but the kinetics of this process has yet to be fully appreciated. We demonstrate with a yeast vaccine model that the rate of Ag release in the phagosome directly affects cross-presentation efficiency, with an apparent time limit of ∼25 min postphagocytosis for Ag release to be productive. Ag expressed on the yeast surface is cross-presented much more efficiently than Ag trapped in the yeast cytosol by the cell wall. The cross-presentation efficiency of yeast surface-displayed Ag can be increased by the insertion of linkers susceptible to cleavage in the early phagosome. Ags indirectly attached to yeast through Ab fragments are less efficiently cross-presented when the Ab dissociation rate is extremely slow.
Direct Action of Type I IFN on NK Cells Is Required for Their Activation in Response to Vaccinia Viral Infection In Vivo
Authors: Martinez Jennifer , Huang Xiaopei , Yang Yiping
Published: April 2014

Type I IFN plays an important role in the activation of NK cells. However, the mechanism underlying type I IFN-dependent NK cell activation remains largely unknown. A recent report suggested that type I IFN acted on accessory dendritic cells, leading to IL-15 production, and that subsequent trans-presentation of IL-15 was required for NK cell activation upon stimulation with synthetic TLR ligands. It is not clear how type I IFN regulates NK cell activation in response to live pathogens. Using a murine model of infection with vaccinia virus (VV), we previously demonstrated a critical role for type I IFN in the innate immune control of VV infection. In this study, we first showed that type I IFN did not directly protect L929 cells from VV infection in vitro and that type I IFN-dependent innate immune control of VV infection in vivo was mediated by activated NK cells. We further demonstrated that direct action of type I IFN on NK cells, but not on dendritic cells, is required for the activation of NK cells in response to VV infection both in vitro and in vivo, leading to efficient VV clearance. Our findings may help design effective strategies for the control of poxviral infections in vivo.
Regulation of T Cell Homeostasis by the Transmembrane Adaptor Protein SIT
Authors: Posevitz Vilmos , Arndt Boerge , Krieger Tina , Warnecke Nicole , Schraven Burkhart , Simeoni Luca
Published: April 2014

The transmembrane adaptor protein SIT is a negative regulator of TCR-mediated signaling. However, little is known about the functional role of SIT in mature T cells. In this study, we show that mice deficient for SIT display a decreased number of naive CD8+ T cells and a progressive accumulation of memory-like (CD44high) CD8+ T lymphocytes that resemble cells undergoing homeostatic proliferation. Indeed, when transferred into lymphopenic hosts, SIT−/− naive CD8+ T cells undergo enhanced homeostatic proliferation and express a higher level of CD44 in comparison to wild-type T cells. By using class-I-restricted TCR transgenic models with different ligand affinity/avidity, we show that lymphopenia-induced homeostatic proliferation is more pronounced in cells carrying low-affinity TCRs. Strikingly, the loss of SIT induces homeostatic proliferation of HY TCR transgenic cells, which are normally unable to proliferate in lymphopenic mice. Collectively, these data demonstrate that SIT negatively regulates T cell homeostasis. Finally, we show that SIT-deficient T cells develop a mechanism analogous to sensory adaptation as they up-regulate CD5, down-regulate the coreceptor, and display impaired TCR-mediated ZAP-70 activation.
EBV Latent Membrane Proteins (LMPs) 1 and 2 as Immunotherapeutic Targets: LMP-Specific CD4+ Cytotoxic T Cell Recognition of EBV-Transformed B Cell Lines
Authors: Haigh Tracey A. , Lin Xiaorong , Jia Hui , Hui Edwin P. , Chan Anthony T. C. , Rickinson Alan B. , Taylor Graham S.
Published: April 2014

The EBV-latent membrane proteins (LMPs) 1 and 2 are among only three viral proteins expressed in EBV-associated Hodgkin’s lymphoma and nasopharyngeal carcinoma. Since these tumors are HLA class I and class II-positive, the LMPs could serve as both CD8+ and CD4+ T cell targets. In contrast to CD8 responses, very little is known about CD4 responses to LMPs. In this study, we describe CD4+ T cell clones defining four LMP1- and three LMP2-derived peptide epitopes and their restricting alleles. All clones produced Th1-like cytokines in response to peptide and most killed peptide-loaded target cells by perforin-mediated lysis. Although clones to different epitopes showed different functional avidities in peptide titration assays, avidity per se was a poor predictor of the ability to recognize naturally infected B lymphoblastoid cell lines (LCLs) expressing LMPs at physiologic levels. Some epitopes, particularly within LMP1, consistently mediated strong LCL recognition detectable in cytokine release, cytotoxicity, and outgrowth inhibition assays. Using cyclosporin A to selectively block cytokine release, we found that CD4+ T cell cytotoxicity is the key effector of LCL outgrowth control. We therefore infer that cytotoxic CD4+ T cells to a subset of LMP epitopes could have therapeutic potential against LMP-expressing tumors.