bluuebunny/crossref_metadata_2025 huggingface dataset:
Down-Regulation of ICOS Ligand by Interaction with ICOS Functions as a Regulatory Mechanism for Immune Responses
Authors: Watanabe Masashi , Takagi Yuri , Kotani Motoko , Hara Yasushi , Inamine Ayako , Hayashi Katsuhiko , Ogawa Shuhei , Takeda Kei , Tanabe Kazunari , Abe Ryo
Published: April 2014

Although it is well-known that the ICOS-ICOS ligand (ICOSL) costimulatory pathway is important for many immune responses, recent accumulated evidence suggests that dysregulation of this pathway may lead to and/or exaggerate autoimmune responses. ICOS is induced on the cell surface after T cell activation. Similarly, ICOSL is up-regulated on APCs by several mitogenic stimuli. However, the mechanism regulating expression of the ICOS-ICOSL pair, and the significance of controlling their expression for an appropriate immune response, is largely unknown. To gain a better understanding of the importance of fine control of the ICOS-ICOSL costimulatory pathway, we generated ICOS-transgenic (Tg) mice that have high constitutive expression of ICOS in all T cells. Using ICOS-Tg mice, we studied whether in vivo immune responses were affected. Unexpectedly, we first found that ICOS-Tg mice exhibited a phenotype resembling ICOS-deficient mice in their Ag-specific Ab response, such as a defect in class switch recombination. Further examination revealed that ICOSL expression of APCs was significantly suppressed in ICOS-Tg mice. Interestingly, suppression of ICOSL was induced by interaction of ICOSL with ICOS, and it seemed to be regulated at the posttranscriptional level. The suppressive effect of the ICOS-ICOSL interaction overcame the positive effect of CD40 or B cell activation factor of the TNF family (BAFF) stimulation on ICOSL expression. Together, our studies demonstrate a novel mechanism for the regulation of ICOSL expression in vivo and suggest that the ICOS costimulatory pathway is subject to negative feedback regulation by ICOSL down-regulation in response to ICOS expression.
CD137 Costimulation of CD8+ T Cells Confers Resistance to Suppression by Virus-Induced Regulatory T Cells
Authors: Robertson Shelly J. , Messer Ronald J. , Carmody Aaron B. , Mittler Robert S. , Burlak Christopher , Hasenkrug Kim J.
Published: April 2014

Chronic viral infections cause high levels of morbidity and mortality worldwide, making the development of effective therapies a high priority for improving human health. We have used mice infected with Friend virus as a model to study immunotherapeutic approaches to the cure of chronic retroviral infections. In chronic Friend virus infections CD4+ T regulatory (Treg) cells suppress CD8+ T cell effector functions critical for virus clearance. In this study, we demonstrate that immunotherapy with a combination of agonistic anti-CD137 Ab and virus-specific, TCR-transgenic CD8+ T cells produced greater than 99% reductions of virus levels within 2 wk. In vitro studies indicated that the CD137-specific Ab rendered the CD8+ T cells resistant to Treg cell-mediated suppression with no direct effect on the suppressive function of the Treg cells. By 2 weeks after transfer, the adoptively transferred CD8+ T cells were lost, likely due to activation-induced cell death. The highly focused immunological pressure placed on the virus by the single specificity CD8+ T cells led to the appearance of escape variants, indicating that broader epitope specificity will be required for long-term virus control. However, the results demonstrate a potent strategy to potentiate the function of CD8+ T cells in the context of immunosuppressive Treg cells.
Aging Down-Regulates the Transcription Factor E2A, Activation-Induced Cytidine Deaminase, and Ig Class Switch in Human B Cells
Authors: Frasca Daniela , Landin Ana Marie , Lechner Suzanne C. , Ryan John G. , Schwartz Robert , Riley Richard L. , Blomberg Bonnie B.
Published: April 2014

Elderly humans have compromised humoral and cellular immune responses, which lead to reduced protection to infectious agents and to vaccines. Currently, available vaccines suboptimally protect the elderly population. The capacity to class switch the Ig H chain is critical to the effectiveness of humoral immune responses in mice and humans. We have previously shown in mice that the E2A-encoded transcription factor E47, which regulates many B cell functions, is down-regulated in old splenic B cells. This leads to a reduction in the activation-induced cytidine deaminase (AID), which is known to induce class switch recombination and Ig somatic hypermutation. The old activated murine B cells also have less AID and less switched Abs. We have extended our study here to investigate whether aging also affects Ab production and E47 and AID expression in B cells isolated from the peripheral blood of human subjects (18–86 years). Our results obtained with activated CD19+ B cells show that the expression of E47, AID, and Igγ1 circle transcripts progressively decrease with age. We also show an age-related decline in the percentage of switch memory B cells (IgG+/IgA+), an increase in that of naive B cells (IgG−/IgA−/CD27−) for most individuals, and no decrease in that of IgM memory cells in peripheral blood, consistent with our data on the decrease seen in class switch recombination in vitro. Our results provide a possible molecular mechanism for a B cell intrinsic defect in the humoral immune response with aging and suggest avenues for improvement of vaccine response in elderly humans.
Derivation and Fluidity of Acutely Induced Dysfunctional CD8+ T Cells
Authors: Plesa Gabriela , Snook Adam E. , Waldman Scott A. , Eisenlohr Laurence C.
Published: April 2014

Dysfunctional CD8+ T (TCD8+) cells lacking cytokine production have been identified in many viral infections, but their genesis is not well understood. Established results indicate that such cells could be either high avidity that enter a refractory state due to overstimulation or low avidity that are only partially stimulated. Using an acute, resolving infection model that results in rapid production of dysfunctional cells, we show that this IL2 unresponsive phenotype emerges from the low end of the avidity spectrum and is characterized by broad TCR usage and a reduced proliferation rate. Furthermore, the dysfunctional population is extremely fluid, being sustained by high Ag dose but virtually eliminated following low dose boosting. Together, these results suggest that persistence of dysfunctional cells generated in this manner depends upon continual exposure to high Ag levels and that such cells may ultimately predominate if functional cells become exhausted.
The Lymphopenic Environment of CD132 (Common γ-Chain)-Deficient Hosts Elicits Rapid Homeostatic Proliferation of Naive T Cells via IL-15
Authors: Ramsey Chris , Rubinstein Mark P. , Kim David M. , Cho Jae-Ho , Sprent Jonathan , Surh Charles D.
Published: April 2014

Homeostatic proliferation for naive T cells is observed readily only under lymphopenic conditions in response to elevated levels of IL-7 and contact with self-MHC/peptide ligands. Homeostatic proliferation occurs at a slow pace and gradually induces the dividing cells to acquire characteristics of memory cells. We describe a novel type of homeostatic proliferation whereby naive T cells proliferate at a significantly faster rate, resembling the proliferation speed induced by foreign Ags, and the expanding cells rapidly differentiate into central memory cells. Remarkably, such rapid homeostatic proliferation is driven by a combination of IL-2 and IL-15, with IL-15 playing a bigger role, and applies for a wide repertoire of CD8+ naive T cells, including many TCR-transgenic lines, even those that fail to undergo IL-7-driven homeostatic proliferation. Thus, naive T cells can be induced to undergo homeostatic proliferation of variable speed with a few members of the common γ-chain (CD132) family of cytokines, the speed of proliferation depending on the levels of the particular cytokine involved.
Neural Crest Origin of Perivascular Mesenchyme in the Adult Thymus
Authors: Müller Susanna M. , Stolt Claus C. , Terszowski Grzegorz , Blum Carmen , Amagai Takashi , Kessaris Nicoletta , Iannarelli Palma , Richardson William D. , Wegner Michael , Rodewald Hans-Reimer
Published: April 2014

The endodermal epithelial thymus anlage develops in tight association with neural crest (NC)-derived mesenchyme. This epithelial-NC interaction is crucial for thymus development, but it is not known how NC supports thymus development or whether NC cells or their progeny make any significant contribution to the adult thymus. By nude mouse blastocyst complementation and by cell surface phenotype, we could previously separate thymus stroma into Foxn1-dependent epithelial cells and a Foxn1-independent mesenchymal cell population. These mesenchymal cells expressed vascular endothelial growth factor-A, and contributed to thymus vascularization. These data suggested a physical or functional association with thymic blood vessels, but the origin, location in the thymus, and function of these stromal cells remained unknown. Using a transgenic mouse expressing Cre recombinase in premigratory NC (Sox10-Cre), we have now fate-mapped the majority of these adult mesenchymal cells to a NC origin. NC-derived cells represent tightly vessel-associated pericytes that are sandwiched between endothelium and epithelium along the entire thymus vasculature. The ontogenetic, phenotypic, and positional definition of this distinct perivascular mesenchymal compartment provides a cellular basis for the role of NC in thymus development and possibly maintenance, and might be useful to address properties of the endothelial-epithelial barrier in the adult thymus.
Equivalent Specificity of Peripheral Blood and Islet-Infiltrating CD8+ T Lymphocytes in Spontaneously Diabetic HLA-A2 Transgenic NOD Mice
Authors: Énée Emmanuelle , Martinuzzi Emanuela , Blancou Philippe , Bach Jean-Marie , Mallone Roberto , van Endert Peter
Published: April 2014

CD8+ T cells play an important role in the initiation of insulitis and in the destructive stage leading to insulin-dependent diabetes mellitus. A string of recent studies has led to the identification of numerous HLA-A2-restricted epitopes derived from pancreatic β cell Ags. It is hoped that assays detecting responses of patient PBMC to such epitopes might be instrumental for early diagnosis of β cell-directed autoimmunity and for monitoring trials of immunointervention. However, it remains unclear whether the results of assays studying PBMC reflect responses of islet-infiltrating lymphocytes, and to what extent they correlate with disease risk and/or activity. We have used female and male humanized NOD mice expressing HLA-A2 in addition to murine MHC class I molecules to study spontaneous responses of islet-infiltrating blood, spleen, and lymph node lymphocytes of various age groups to a panel of 16 epitopes. Twelve of these are restricted by HLA-A2, have previously been shown to be recognized by patient CTL, and have identical sequences in human and murine autoantigens. Using an IFN-γ ELISPOT assay, we find highly similar hierarchies of epitope immunodominance in the different T cell compartments, including peripheral blood and pancreatic islets. Moreover, we demonstrate that most of the epitopes eliciting dominant responses in humans display similar status in the mouse model. These results emphasize the potential of humanized mice as tools for studying spontaneous autoimmune CTL responses, and they provide a strong rationale for the development and use of assays monitoring responses of CD8+ PBMC in human type 1 diabetes.
A 9-Centimorgan Interval of Chromosome 10 Controls the T Cell-Dependent Psoriasiform Skin Disease and Arthritis in a Murine Psoriasis Model
Authors: Wang Honglin , Kess Daniel , Lindqvist Anna-Karin B. , Peters Thorsten , Sindrilaru Anca , Wlaschek Meinhard , Blakytny Robert , Holmdahl Rikard , Scharffetter-Kochanek Karin
Published: April 2014

Psoriasis is a complex genetic disease of unresolved pathogenesis with both heritable and environmental factors contributing to onset and severity. In addition to a disfiguring skin inflammation, approximately 10–40% of psoriasis patients suffer from destructive joint involvement. Previously, we reported that the CD18 hypomorphic PL/J mouse carrying a mutation resulting in reduced expression of the common chain of β2 integrins (CD11/CD18) spontaneously develops a skin disease that closely resembles human psoriasis. In contrast, the same mutation on C57BL/6J background did not demonstrate this phenotype. By a genome-wide linkage analysis, two major loci were identified as contributing to the development of psoriasiform dermatitis under the condition of low CD18 expression. Using a congenic approach, we now demonstrate that the introduction of a 9-centimorgan fragment of chromosome 10 derived from the PL/J strain into the disease-resistant CD18 hypomorphic C57BL/6J was promoting the development of psoriasiform skin disease and notably also arthritis. We therefore designated this locus psoriasiform skin disease-associated locus 1 (PSD1). High numbers of CD4+ T cells and TNF-α producing macrophages were detected both in inflamed skin and joints in these congenic mice, with a complete resolution upon TNF-α inhibitor therapy or depletion of CD4+ T cells. For the first time, we have identified a distinct genetic element that contributes to the T cell-dependent development of both psoriasiform skin disease and associated arthritis. This congenic model will be suitable to further investigations of genetic and molecular pathways that cause psoriasiform dermatitis and arthritis, and it may also be relevant for other autoimmune diseases.
Down-Modulation of TCR Expression by Salmonella enterica serovar Typhimurium
Authors: van der Velden Adrianus W. M. , Dougherty Jeffrey T. , Starnbach Michael N.
Published: April 2014

T cell-mediated adaptive immunity is required to help clear infection with the facultative intracellular bacterial pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium), yet development of T cell-mediated adaptive immunity to S. Typhimurium has been described as slow and inefficient. A key step in inducing T cell-mediated adaptive immunity is T cell priming; the activation, proliferation, and differentiation of naive T cells following initial encounter with Ag. We previously demonstrated that S. Typhimurium had a direct inhibitory effect on naive T cells from mouse, blocking their proliferation. In this study, we show that S. Typhimurium down-modulates expression of the TCR β-chain, a molecule that is essential for Ag recognition and T cell function. Specifically, we demonstrate that reduced amounts of surface and intracellular TCR-β protein and decreased levels of tcrβ transcript are expressed by T cells cultured in the presence of S. Typhimurium. We further show that the down-modulation of TCR-β expression requires contact between S. Typhimurium and the T cells and that once contact occurs, a factor capable of reducing TCR-β expression is secreted. These results provide new insight into the mechanism by which S. Typhimurium may inhibit T cell priming and avoid clearance by the adaptive immune system.
HIV Envelope Suppresses CD4+ T Cell Activation Independent of T Regulatory Cells
Authors: Hu Haitao , Fernando Kathy , Ni Houping , Weissman Drew
Published: April 2014

We previously demonstrated that HIV envelope glycoprotein (Env), delivered in the form of a vaccine and expressed by dendritic cells or 293T cells, could suppress Ag-stimulated CD4+ T cell proliferation. The mechanism remains to be identified but is dependent on CD4 and independent of coreceptor binding. Recently, CD4+ regulatory T (Treg) cells were found to inhibit protective anti-HIV CD4+ and CD8+ T cell responses. However, the role of Tregs in HIV remains highly controversial. HIV Env is a potent immune inhibitory molecule that interacts with host CD4+ cells, including Treg cells. Using an in vitro model, we investigated whether Treg cells are involved in Env-induced suppression of CD4+ T cell proliferation, and whether Env directly affects the functional activity of Treg cells. Our data shows that exposure of human CD4+ T cells to Env neither induced a higher frequency nor a more activated phenotype of Treg cells. Depletion of CD25+ Treg cells from PBMC did not overcome the Env-induced suppression of CD4+ T cell proliferation, demonstrating that CD25+FoxP3+ Treg cells are not involved in Env-induced suppression of CD4+ T cell proliferation. In addition, we extend our observation that similar to Env expressed on cells, Env present on virions also suppresses CD4+ T cell proliferation.
Heme Oxygenase-1 Is a Critical Regulator of Nitric Oxide Production in Enterohemorrhagic Escherichia coli-Infected Human Enterocytes
Authors: Vareille Marjolaine , Rannou François , Thélier Natacha , Glasser Anne-Lise , de Sablet Thibaut , Martin Christine , Gobert Alain P.
Published: April 2014

Enterohemorrhagic Escherichia coli (EHEC) are the causative agent of hemolytic-uremic syndrome. In the first stage of the infection, EHEC interact with human enterocytes to modulate the innate immune response. Inducible NO synthase (iNOS)-derived NO is a critical mediator of the inflammatory response of the infected intestinal mucosa. We therefore aimed to analyze the role of EHEC on iNOS induction in human epithelial cell lines. In this regard, we show that EHEC down-regulate IFN-γ-induced iNOS mRNA expression and NO production in Hct-8, Caco-2, and T84 cells. This inhibitory effect occurs through the decrease of STAT-1 activation. In parallel, we demonstrate that EHEC stimulate the rapid inducible expression of the gene hmox-1 that encodes for the enzyme heme oxygenase-1 (HO-1). Knock-down of hmox-1 gene expression by small interfering RNA or the blockade of HO-1 activity by zinc protoporphyrin IX abrogated the EHEC-dependent inhibition of STAT-1 activation and iNOS mRNA expression in activated human enterocytes. These results highlight a new strategy elaborated by EHEC to control the host innate immune response.
NK Cells Expressing a Progesterone Receptor Are Susceptible to Progesterone-Induced Apoptosis
Authors: Arruvito Lourdes , Giulianelli Sebastián , Flores Ana C. , Paladino Natalia , Barboza Marcos , Lanari Claudia , Fainboim Leonardo
Published: April 2014

It has been proposed that progesterone (P4) induces the suppression of immune responses, particularly during pregnancy. However, knowledge about the mechanisms involved has remained largely elusive. We demonstrate herein that peripheral blood NK (PBNK) cells express both classical progesterone receptor (PR) isoforms and are specifically affected by the actions of P4 through two apparently independent mechanisms. Progesterone induces caspase-dependent PBNK cell death, which is reversed by two different anti-progestins, ZK 98.299 and RU 486, supporting the involvement of classical PR isoforms. It was suggested that CD56brightCD16− killer Ig-like receptor (KIR)− NK cells might represent precursor cells, which, upon activation, acquire the features of a more mature NK subset expressing KIR receptors. The present study demonstrates that PR expression seems to be restricted to more mature KIR+ PBNK cells. The expression of PR had a functional counterpart in the suppressive effect of P4 on IL-12-induced IFN-γ secretion. This cytokine suppression was mainly observed in KIR+ PBNK cells, without affecting the high secretion of IFN-γ by CD56bright PBNK cells. The lack of PR expression on CD56brightKIR− PBNK cells provides an additional phenotypic marker to test the idea that they might represent the PBNK precursors selectively recruited into the endometrium where they differentiate to become the uterine NK cells. Additionally, these findings may be relevant to NK cell function in viral immunity, human reproduction, and tumor immunity.
Stat6 Signaling Suppresses VLA-4 Expression by CD8+ T Cells and Limits Their Ability to Infiltrate Tumor Lesions In Vivo
Authors: Sasaki Kotaro , Zhao Xi , Pardee Angela D. , Ueda Ryo , Fujita Mitsugu , Sehra Sarita , Kaplan Mark H. , Kane Lawrence P. , Okada Hideho , Storkus Walter J.
Published: April 2014

VLA-4 plays a critical role in T cell trafficking into inflammatory sites. Our recent studies have suggested that VLA-4 expression on CD8+ T cells is negatively controlled by IL-4 and serves as a functionally distinguishing variable for why Type-1, but not Type-2, CD8+ T cells are able to traffic into tumors. In this study, using in vitro culture of murine CD8+ T cells under Type-1 and Type-2 cytokine conditions, we show that IL-4-mediated down-regulation of VLA-4 expression is completely abrogated in Stat6-deficient CD8+ T cells. Conversely, CD8+ T cells expressing a constitutively active mutant form Stat6 (Stat6VT) failed to express VLA-4 even in the absence of IL-4-stimulation. Notably, Type-2 CD8+ T cells developed from Stat6−/− but not wild-type mice were competent to migrate into tumor lesions in vivo. These results suggest that Stat6-signaling is necessary and sufficient to restrict CD8+ T cell expression of VLA-4 (by IL-4), thereby serving as a regulator for CD8+ T cell infiltration into tumors.
An Age-Old Paradigm Challenged: Old Baboons Generate Vigorous Humoral Immune Responses to LcrV, A Plague Antigen
Authors: Stacy Sue , Pasquali Amanda , Sexton Valerie L. , Cantwell Angelene M. , Kraig Ellen , Dube Peter H.
Published: April 2014

Immune senescence in the elderly results in decreased immunity with a concomitant increase in susceptibility to infection and diminished efficacy of vaccination. Nonhuman primate models have proven critical for testing of vaccines and therapeutics in the general population, but a model using old animals has not been established. Toward that end, immunity to LcrV, a protective Ag from Yersinia pestis, was tested in young and old baboons. Surprisingly, there was no age-associated loss in immune competence; LcrV elicited high-titer, protective Ab responses in the older individuals. The primary responses in the younger baboons were lower, but they did show boosting upon secondary immunization to the levels achieved in the old animals. The LcrV Ag was also tested in mice and, as expected, age-associated loss of immunity was seen; older animals responded with lower-titer Abs and, as a result, were more susceptible to Yersinia challenge. Thus, although age-related loss in immune function has been observed in humans, rodents, and some nonhuman primates, baboons appear to be unusual; they age without losing immune competence.
Evidence That CD8+ Dendritic Cells Enable the Development of γδ T Cells That Modulate Airway Hyperresponsiveness
Authors: Cook Laura , Miyahara Nobuaki , Jin Niyun , Wands J. M. , Taube Christian , Roark Christina L. , Potter Terry A. , Gelfand Erwin W. , O'Brien Rebecca L. , Born Willi K.
Published: April 2014

Airway hyperresponsiveness (AHR), a hallmark of asthma and several other diseases, can be modulated by γδ T cells. In mice sensitized and challenged with OVA, AHR depends on allergen-specific αβ T cells; but Vγ1+ γδ T cells spontaneously enhance AHR, whereas Vγ4+ γδ T cells, after being induced by airway challenge, suppress AHR. The activity of these γδ T cell modulators is allergen nonspecific, and how they develop is unclear. We now show that CD8 is essential for the development of both the AHR suppressor and enhancer γδ T cells, although neither type needs to express CD8 itself. Both cell types encounter CD8-expressing non-T cells in the spleen, and their functional development in an otherwise CD8-negative environment can be restored with transferred spleen cell preparations containing CD8+ dendritic cells (DCs), but not CD8+ T cells or CD8− DCs. Our findings suggest that CD8+ DCs in the lymphoid tissues enable an early step in the development of γδ T cells through direct cell contact. DC-expressed CD8 might take part in this interaction.
Th1 and Th2 Cells Form Morphologically Distinct Immunological Synapses
Authors: Thauland Timothy J. , Koguchi Yoshinobu , Wetzel Scott A. , Dustin Michael L. , Parker David C.
Published: April 2014

The arrangement of molecules at the interface between T cells and APCs is known as the immunological synapse (IS). We conducted experiments with supported planar bilayers and transfected fibroblast APC to examine the IS formed by polarized Th1 and Th2 cells. Th1 cells formed typical “bull’s-eye” IS with a ring of adhesion molecules surrounding MHC/TCR interactions at all Ag concentrations tested, while Th2 cells formed multifocal IS at high concentrations of Ag. At low Ag concentrations, the majority of Th2 cells formed IS with a compact, central accumulation of MHC/TCR, but ICAM-1 was not excluded from the center of the IS. Additionally, CD45 was excluded from the center of the interface between Th1 cells and APC, while CD45 was found at the center of the multifocal IS formed by Th2 cells. Finally, phosphorylated signaling molecules colocalized with MHC/TCR to a greater extent in Th2 IS. Together, our results indicate that the IS formed by Th1 and Th2 cells are distinct in structure, with Th2 cells failing to form bull’s-eye IS.
Functional Analysis of Histone Methyltransferase G9a in B and T Lymphocytes
Authors: Thomas Lance R. , Miyashita Hiroki , Cobb Robin Milley , Pierce Steven , Tachibana Makoto , Hobeika Elias , Reth Michael , Shinkai Yoichi , Oltz Eugene M.
Published: April 2014

Lymphocyte development is controlled by dynamic repression and activation of gene expression. These developmental programs include the ordered, tissue-specific assembly of Ag receptor genes by V(D)J recombination. Changes in gene expression and the targeting of V(D)J recombination are largely controlled by patterns of epigenetic modifications imprinted on histones and DNA, which alter chromatin accessibility to nuclear factors. An important component of this epigenetic code is methylation of histone H3 at lysine 9 (H3K9me), which is catalyzed by histone methyltransferases and generally leads to gene repression. However, the function and genetic targets of H3K9 methyltransferases during lymphocyte development remain unknown. To elucidate the in vivo function of H3K9me, we generated mice lacking G9a, a major H3K9 histone methyltransferase, in lymphocytes. Surprisingly, lymphocyte development is unperturbed in G9a-deficient mice despite a significant loss of H3K9me2 in precursor B cells. G9a deficiency is manifest as modest defects in the proliferative capacity of mature B cells and their differentiation into plasma cells following stimulation with LPS and IL-4. Precursor lymphocytes from the mutant mice retain tissue- and stage-specific control over V(D)J recombination. However, G9a deficiency results in reduced usage of Igλ L chains and a corresponding inhibition of Igλ gene assembly in bone marrow precursors. These findings indicate that the H3K9me2 epigenetic mark affects a highly restricted set of processes during lymphocyte development and activation.
MEK1/2 Induces STAT5-Mediated Germline Transcription of the TCRγ Locus in Response to IL-7R Signaling
Authors: Maki Kazushige , Ikuta Koichi
Published: April 2014

The IL-7R plays an essential role in γδ T cell development by inducing V-J recombination of the TCRγ locus through STAT5. Although tyrosine residues in the intracellular domain of the mouse IL-7R α-chain (IL-7Rα) have been implicated in STAT5 activation, it is still unknown whether they are essential for γδ T cell development. In this study, we showed that those IL-7Rα tyrosine residues are not essential for γδ T cell development, because phenylalanine replacement of four intracellular tyrosine residues (IL-7R-FFFF) partially rescued γδ T cell development of IL-7Rα−/− progenitors. To examine signaling pathways activated by IL-7R-FFFF, we introduced a chimeric receptor consisting of the human IL-4R α-chain and mouse IL-7R-FFFF (4R/7R-FFFF) into an IL-7-dependent pre-B cell line and found that 4R/7R-FFFF induced TCRγ germline transcription and STAT5 activation. Treatment of cells with MEK1/2 inhibitors significantly decreased levels of TCRγ germline transcription and STAT5 tyrosine phosphorylation mediated by 4R/7R-FFFF, suggesting that MEK1/2 plays an alternative role in STAT5 activation by IL-7R. MEK1/2 associated with STAT5 and induced STAT5 tyrosine phosphorylation and DNA binding activity. Furthermore, MEK1 directly phosphorylated a STAT5 tyrosine residue in vitro. Finally, active MEK1 partially rescued TCRγ germline transcription by IL-7R in a pre-T cell line. These results demonstrate that MEK1/2 induces TCRγ germline transcription by phosphorylating STAT5 through IL-7R-FFFF and suggest a potential role for MAPK in IL-7R tyrosine-independent activation of STAT5.
The Anti-Apoptotic Bcl-2 Family Member Mcl-1 Promotes T Lymphocyte Survival at Multiple Stages
Authors: Dzhagalov Ivan , Dunkle Alexis , He You-Wen
Published: April 2014

T lymphocyte development and function are tightly regulated by the intrinsic death pathway through members of the Bcl-2 family. Genetic studies have demonstrated that the Bcl-2 family member Mcl-1 is an important anti-apoptotic protein in the development of multiple cell types including T lymphocytes. However, the expression pattern and anti-apoptotic roles of Mcl-1 in T lymphocytes at different developmental stages remain to be fully determined. In this study, we examined the expression pattern of Mcl-1 in different populations of T cells at the single-cell level and found that Mcl-1 protein is constitutively expressed in all T cell populations and up-regulated upon TCR stimulation. We then investigated the role of Mcl-1 in the survival of these different populations by conditionally deleting Mcl-1 at various T cell stages. Our results show that Mcl-1 is required for the survival of double-negative and single-positive thymocytes as well as naive and activated T cells. Furthermore, we demonstrate that Mcl-1 functions together with Bcl-xL to promote double-positive thymocyte survival. Thus, Mcl-1 is a critical anti-apoptotic factor for the survival of T cells at multiple stages in vivo.
IFN-α/β Signaling Is Required for Polarization of Cytokine Responses toward a Protective Type 1 Pattern during Experimental Cryptococcosis
Authors: Biondo Carmelo , Midiri Angelina , Gambuzza Maria , Gerace Elisabetta , Falduto Maria , Galbo Roberta , Bellantoni Antonella , Beninati Concetta , Teti Giuseppe , Leanderson Tomas , Mancuso Giuseppe
Published: April 2014

The antiviral activities of type I IFNs have long been established. However, comparatively little is known of their role in defenses against nonviral pathogens. We examined here the effects of type I IFNs on host resistance against the model pathogenic yeast Cryptococcus neoformans. After intratracheal or i.v. challenge with this fungus, most mice lacking either the IFN-α/β receptor (IFN-α/βR) or IFN-β died from unrestrained pneumonia and encephalitis, while all wild-type controls survived. The pulmonary immune response of IFN-α/βR−/− mice was characterized by increased expression of IL-4, IL-13, and IL-10, decreased expression of TNF-α, IFN-γ, inducible NO synthetase, and CXCL10, and similar levels of IL-12 mRNA, compared with wild-type controls. Histopathological analysis showed eosinophilic infiltrates in the lungs of IFN-α/βR−/− mice, although this change was less extensive than that observed in similarly infected IFN-γR-deficient animals. Type I IFN responses could not be detected in the lung after intratracheal challenge. However, small, but statistically significant, elevations in IFN-β levels were measured in the supernatants of bone marrow-derived macrophages or dendritic cells infected with C. neoformans. Our data demonstrate that type I IFN signaling is required for polarization of cytokine responses toward a protective type I pattern during cryptococcal infection.
IL-1β-Driven ST2L Expression Promotes Maturation Resistance in Rapamycin-Conditioned Dendritic Cells
Authors: Turnquist Hēth R. , Sumpter Tina L. , Tsung Allan , Zahorchak Alan F. , Nakao Atsunori , Nau Gerard J. , Liew Foo Y. , Geller David A. , Thomson Angus W.
Published: April 2014

Maturation resistance and tolerogenic properties can be conferred on human and murine dendritic cells (DC), crucial regulators of T cell responses, by exposure to rapamycin (RAPA), a “tolerance-sparing” immunosuppressive agent. Mechanisms underlying this acquired unresponsiveness, typified by diminished functional responses to TLR or CD40 ligation, have not been identified. We report that in vitro and in vivo conditioning of murine myeloid DC with RAPA elicits the de novo production of IL-1β by otherwise phenotypically immature DC. Interestingly, IL-1β production promotes overexpression of the transmembrane form of the IL-1R family member, IL-1R-like 1, also know as ST2 on RAPA-conditioned DC (RAPA-DC). ST2 is the recently identified receptor for IL-33, a cytokine favoring Th2 responses. In addition, transmembrane ST2, or ST2L, has been implicated as a potent negative regulator of TLR signaling. RAPA-DC generated from ST2−/− mice exhibited higher levels of costimulatory molecules (CD86) than wild-type RAPA-DC. Consistent with its regulatory function, IL-1β-induced ST2L expression suppressed the responsiveness of RAPA-DC to TLR or CD40 ligation. Thus, as a result of their de novo production of IL-1β, RAPA-DC up-regulate ST2L and become refractory to proinflammatory, maturation-inducing stimuli. This work identifies a novel mechanism through which a clinically important immunosuppressant impedes the capacity of DC to mature and consequently stimulate effector/adaptive T cell responses.
Macrophage Dysfunction and Susceptibility to Pulmonary Pseudomonas aeruginosa Infection in Surfactant Protein C-Deficient Mice
Authors: Glasser Stephan W. , Senft Albert P. , Whitsett Jeffrey A. , Maxfield Melissa D. , Ross Gary F. , Richardson Theresa R. , Prows Daniel R. , Xu Yan , Korfhagen Thomas R.
Published: April 2014

To determine the role of surfactant protein C (SP-C) in host defense, SP-C-deficient (Sftpc−/−) mice were infected with the pulmonary pathogen Pseudomonas aeruginosa by intratracheal injection. Survival of young, postnatal day 14 Sftpc−/− mice was decreased in comparison to Sftpc+/+ mice. The sensitivity to Pseudomonas bacteria was specific to the 129S6 strain of Sftpc−/− mice, a strain that spontaneously develops interstitial lung disease-like lung pathology with age. Pulmonary bacterial load and leukocyte infiltration were increased in the lungs of Sftpc−/− mice 24 h after infection. Early influx of polymorphonuclear leukocytes in the lungs of uninfected newborn Sftpc−/− mice relative to Sftpc+/+ mice indicate that the lack of SP-C promotes proinflammatory responses in the lung. Mucin expression, as indicated by Alcian blue staining, was increased in the airways of Sftpc−/− mice following infection. Phagocytic activity of alveolar macrophages from Sftpc−/− mice was reduced. The uptake of fluorescent beads in vitro and the number of bacteria phagocytosed by alveolar macrophages in vivo was decreased in the Sftpc−/− mice. Alveolar macrophages from Sftpc−/− mice expressed markers of alternative activation that are associated with diminished pathogen response and advancing pulmonary fibrosis. These findings implicate SP-C as a modifier of alveolar homeostasis. SP-C plays an important role in innate host defense of the lung, enhancing macrophage-mediated Pseudomonas phagocytosis, clearance and limiting pulmonary inflammatory responses.
IL-8 as Antibody Therapeutic Target in Inflammatory Diseases: Reduction of Clinical Activity in Palmoplantar Pustulosis
Authors: Skov Lone , Beurskens Frank J. , Zachariae Claus O. C. , Reitamo Sakari , Teeling Jessica , Satijn David , Knudsen Kim M. , Boot Elmieke P. J. , Hudson Debra , Baadsgaard Ole , Parren Paul W. H. I. , van de Winkel Jan G. J.
Published: April 2014

IL-8 is a chemokine that has been implicated in a number of inflammatory diseases involving neutrophil activation. HuMab 10F8 is a novel fully human mAb against IL-8, which binds a discontinuous epitope on IL-8 overlapping the receptor binding site, and which effectively neutralizes IL-8-dependent human neutrophil activation and migration. We investigated whether interference in the cytokine network by HuMab 10F8 might benefit patients suffering from palmoplantar pustulosis, a chronic inflammatory skin disease. Treatment of patients with HuMab 10F8 was well tolerated and significantly reduced clinical disease activity at all five endpoints, which included a ≥50% reduction in the formation of fresh pustules. IL-8 neutralization was monitored at the site of inflammation by assessing exudates of palmoplantar pustulosis lesions. HuMab 10F8 sequestered IL-8 in situ, as observed by rapid dose-dependent decreases of IL-8 concentrations immediately following Ab infusion. These data demonstrate a critical role for IL-8 in the pathophysiology of palmoplantar pustulosis. HuMab 10F8 is capable of interrupting IL-8 activity in vivo and represents a candidate for treatment of inflammatory diseases and other pathological conditions associated with IL-8 overproduction.
Altered Function of Factor I Caused by Amyloid β: Implication for Pathogenesis of Age-Related Macular Degeneration from Drusen
Authors: Wang Jiying , Ohno-Matsui Kyoko , Yoshida Takeshi , Kojima Ariko , Shimada Noriaki , Nakahama Ken-ichi , Safranova Olga , Iwata Nobuhisa , Saido Takaomi C. , Mochizuki Manabu , Morita Ikuo
Published: April 2014

The results of recent studies have implicated local inflammation and complement activation as the processes involved in the pathogenesis of age-related macular degeneration (AMD). We have demonstrated that amyloid β (Aβ), which is deposited in drusen, causes an imbalance in the angiogenesis-related factors in retinal pigment epithelial cells. We have also shown that neprilysin gene-disrupted mice accumulate Aβ, and develop several features of AMD. The purpose of this study was to investigate the mechanisms involved in the development of AMD that are triggered by Aβ. Our results showed that Aβ binds to complement factor I which inhibits the ability of factor I to cleave C3b to inactivated iC3b. Factor H and factor I are soluble complement-activation inhibitors, and preincubation of factor I with Aβ in the presence of factor H abolished the ability of Aβ to cleave C3b, and also abolished the ability of factor I to cleave FGR-AMC. In contrast, Aβ did not affect the function of factor H even after binding. The production of iC3b was significantly decreased when C3b and factor H were incubated with the eyes from neprilysin gene-disrupted mice as compared with when C3b and factor H were incubated with eyes from age-matched wild-type mice. These results suggest that Aβ activates the complement system within drusen by blocking the function of factor I leading to a low-grade, chronic inflammation in subretinal tissues. These findings link four factors that have been suggested to be associated with AMD: inflammation, complement activation, Aβ deposition, and drusen.
Acrolein Inhalation Suppresses Lipopolysaccharide-Induced Inflammatory Cytokine Production but Does Not Affect Acute Airways Neutrophilia
Authors: Kasahara David Itiro , Poynter Matthew E. , Othman Ziryan , Hemenway David , van der Vliet Albert
Published: April 2014

Acrolein is a reactive unsaturated aldehyde that is produced during endogenous oxidative processes and is a major bioactive component of environmental pollutants such as cigarette smoke. Because in vitro studies demonstrate that acrolein can inhibit neutrophil apoptosis, we evaluated the effects of in vivo acrolein exposure on acute lung inflammation induced by LPS. Male C57BL/6J mice received 300 μg/kg intratracheal LPS and were exposed to acrolein (5 parts per million, 6 h/day), either before or after LPS challenge. Exposure to acrolein either before or after LPS challenge did not significantly affect the overall extent of LPS-induced lung inflammation, or the duration of the inflammatory response, as observed from recovered lung lavage leukocytes and histology. However, exposure to acrolein after LPS instillation markedly diminished the LPS-induced production of several inflammatory cytokines, specifically TNF-α, IL-12, and the Th1 cytokine IFN-γ, which was associated with reduction in NF-κB activation. Our data demonstrate that acrolein exposure suppresses LPS-induced Th1 cytokine responses without affecting acute neutrophilia. Disruption of cytokine signaling by acrolein may represent a mechanism by which smoking contributes to chronic disease in chronic obstructive pulmonary disease and asthma.
Identification of Annexin 1 as a Novel Autoantigen in Acute Exacerbation of Idiopathic Pulmonary Fibrosis
Authors: Kurosu Katsushi , Takiguchi Yuichi , Okada Osamu , Yumoto Norio , Sakao Seiichiro , Tada Yuji , Kasahara Yasunori , Tanabe Nobuhiro , Tatsumi Koichiro , Weiden Michael , Rom William N. , Kuriyama Takayuki
Published: April 2014

Consistent with the hypothesis that pulmonary epithelial apoptosis is the key to the acute exacerbation of idiopathic pulmonary fibrosis (IPF), we conducted serological identification of Ags by recombinant expression cloning (SEREX) analysis using type II alveolar cell carcinoma (A549) cell lines to identify disease-related Abs. In a survey of Abs to the recombinant autoantigens identified by SEREX analysis, five Abs were identified as novel candidates for the acute exacerbation of IPF. Abs to annexin 1 were detected in 47 and 53% of the sera and bronchoalveolar lavage materials from patients with acute exacerbation of IPF. Some identical TCR Vβ genes were identified in sequential materials obtained at 1–3 mo in all 10 acute exacerbation IPF cases, suggesting that some infiltrating CD4-positive T cells sharing limited epitopes expand by Ag-driven stimulation during disease extension. The CDR3 region of these identical TCR Vβ genes showed high homology with the N-terminal portion of annexin 1, including in the HLA-DR ligand epitopes predicted by TEPITOPE analysis. By Western blotting analysis and observation of the CD4-positive T cell responses in bronchoalveolar lavage samples, the N-terminal portion of annexin 1 was cleaved and found to induce marked proliferative responses of CD4-positive T cells in three patients. Our study demonstrates that annexin 1 is an autoantigen that raises both Ab production and T cell response in patients with acute exacerbation of IPF, and that the N-terminal portion of annexin 1 plays some role in the pathogenesis of acute exacerbation in IPF patients.
B Lymphocyte Autoimmunity in Rheumatoid Synovitis Is Independent of Ectopic Lymphoid Neogenesis
Authors: Cantaert Tineke , Kolln Johanna , Timmer Trieneke , van der Pouw Kraan Tineke C. , Vandooren Bernard , Thurlings Rogier M. , Cañete Juan D. , Catrina Anca I. , Out Theo , Verweij Cor L. , Zhang Yiping , Tak Paul P. , Baeten Dominique
Published: April 2014

B lymphocyte autoimmunity plays a crucial role in the pathogenesis of rheumatoid arthritis. The local production of autoantibodies and the presence of ectopic lymphoid neogenesis in the rheumatoid synovium suggest that these dedicated microenvironments resembling canonical lymphoid follicles may regulate the initiation and maturation of B cell autoimmunity. In this study, we assessed experimentally the relevance of ectopic lymphoid neogenesis for B cell autoimmunity by a detailed structural, molecular, and serological analysis of seropositive and seronegative human synovitis. We demonstrate that synovial lymphoid neogenesis is a reversible process associated with inflammation which is neither restricted to nor preferentially associated with autoantibody positive rheumatic conditions. Despite the abundant expression of key chemokines and cytokines required for full differentiation toward germinal center reactions, synovial lymphoid neogenesis in rheumatoid arthritis only occasionally progresses toward fully differentiated follicles. In agreement with that observation, we could not detect Ag-driven clonal expansion and affinity maturation of B lymphocytes. Furthermore, ectopic lymphoid neogenesis is not directly associated with local production of anti-citrullinated protein Abs and rheumatoid factor in the rheumatoid joint. Therefore, we conclude that synovial lymphoid neogenesis is not a major determinant of these rheumatoid arthritis-specific autoantibody responses.
Fusions of Dendritic Cells with Breast Carcinoma Stimulate the Expansion of Regulatory T Cells while Concomitant Exposure to IL-12, CpG Oligodeoxynucleotides, and Anti-CD3/CD28 Promotes the Expansion of Activated Tumor Reactive Cells
Authors: Vasir Baldev , Wu Zekui , Crawford Keith , Rosenblatt Jacalyn , Zarwan Corrine , Bissonnette Adam , Kufe Donald , Avigan David
Published: April 2014

Vaccination of patients with dendritic cell (DC)/breast carcinoma fusions stimulated antitumor immune responses in a majority of patients with metastatic disease but only a subset demonstrate evidence of tumor regression. To define the factors that limit vaccine efficacy, we examined the biological characteristics of DC/breast carcinoma fusions as APCs and the nature of the vaccine-mediated T cell response. We demonstrate that fusion of DCs with breast carcinoma cells up-regulates expression of costimulatory and maturation markers and results in high levels of expression of IL-12 consistent with their role as activated APCs. Fusion cells also express the chemokine receptor CCR7, consistent with their ability to migrate to the draining lymph node. However, DC/breast cancer fusions stimulate a mixed T cell response characterized by the expansion of both activated and regulatory T cell populations, the latter of which is characterized by expression of CTLA-4, FOXP3, IL-10, and the suppression of T cell responses. Our results demonstrate that IL-12, IL-18, and TLR 9 agonist CpG oligodeoxynucleotides reduce the level of fusion-mediated regulatory T cell expansion. Our results also demonstrate that sequential stimulation with DC/breast carcinoma fusions and anti-CD3/CD28 results in the marked expansion of activated tumor-specific T cells. These findings suggest that DC/breast carcinoma fusions are effective APCs, but stimulate inhibitory T cells that limit vaccine efficacy. In contrast, exposure to TLR agonists, stimulatory cytokines, and anti-CD3/CD28 enhances vaccine efficacy by limiting the regulatory T cell response and promoting expansion of activated effector cells.
Global T Cell Dysregulation in Non-Autoimmune-Prone Mice Promotes Rapid Development of BAFF-Independent, Systemic Lupus Erythematosus-Like Autoimmunity
Authors: Stohl William , Jacob Noam , Quinn William J. , Cancro Michael P. , Gao Huaxin , Putterman Chaim , Gao Xiaoni , Pricop Luminita , Koss Michael N.
Published: April 2014

In otherwise non-autoimmune-prone C57BL/6 (B6) mice rendered genetically deficient in CD152 (CTLA-4), polyclonal hypergammaglobulinemia with increased levels of systemic lupus erythematosus (SLE)-associated IgG autoantibodies, glomerular IgG and C3 deposition, and interstitial nephritis all developed by 3–5 wk of age. Remarkably, superimposing genetic deficiency of BAFF (B cell-activating factor belonging to the TNF family) onto CD152 deficiency did not substantially attenuate humoral autoimmunity and immunopathology in these mice, despite the resulting marked reduction in B-lineage cells. Although superimposing a BAFF transgene (resulting in constitutive BAFF overexpression) onto CD152-deficient mice did lead to increases in B-lineage cells and serum levels of certain SLE-associated IgG autoantibodies, renal immunopathology remained largely unaffected. Taken together, these results demonstrate that global T cell dysregulation, even in an otherwise non-autoimmune-prone host, can promote systemic humoral autoimmunity and immunopathology in a BAFF-independent manner. Moreover, supraphysiologic expression of BAFF in the setting of ongoing autoimmunity does not necessarily lead to greater immunopathology. These findings may help explain the limited clinical efficacy appreciated to date of BAFF antagonists in human SLE.