bluuebunny/crossref_metadata_2025 huggingface dataset:
Persistent Cytomegalovirus-Specific Memory Responses in the Lung Allograft and Blood following Primary Infection in Lung Transplant Recipients
Authors: Shlobin Oksana A. , West Erin E. , Lechtzin Noah , Miller Susan M. , Borja Marvin , Orens Jonathan B. , Dropulic Lesia K. , McDyer John F.
Published: April 2014

Primary CMV infection in lung transplant recipients (LTRs) is associated with increased mortality. We studied 22 donor CMV-positive, recipient-negative (D+R−) LTRs for the development of posttransplant CMV-specific immunity. We found that 13 of 22 D+R− LTRs (59.1%) seroconverted (CMV IgG Ab+). Using pooled peptides of the immunodominant CMV Ags pp65 and IE1, we detected CMV-specific CD8+IFN-γ+ T cells in the PBMC of 90% of seroconverted individuals following primary infection by intracellular cytokine staining. In contrast, few seroconverters had detectable CMV-specific CD4+IFN-γ+ T cells during viral latency. However, the majority of IgG+ LTRs demonstrated CMV-specific CD4+ and CD8+ T cell proliferative responses from PBMC, with CD4+IFN-γ+ T cells detectable upon re-expansion. Examination of lung allograft mononuclear cells obtained by bronchoalveolar lavage revealed both CMV-specific CD4+ and CD8+IFN-γ+ T cells, including patients from whom CD4+IFN-γ+ T cells were simultaneously undetectable in the PBMC, suggesting differential effector memory populations between these compartments. Moreover, both responses in the PBMC and lung allograft were found to persist, despite substantial immunosuppression, long after primary infection. Clinical correlation in this cohort demonstrated that the acquisition of CMV immunity was associated with freedom from CMV disease (p ≤ 0.009) and preservation of allograft function (p ≤ 0.02) compared with those who failed to develop CMV immunity. Together, our data reveal immunologic heterogeneity in D+R− LTRs, with the development and persistence of primary CMV responses that may provide clinical benefit.
B Cells Are Crucial for Determinant Spreading of T Cell Autoimmunity among β Cell Antigens in Diabetes-Prone Nonobese Diabetic Mice
Authors: Tian Jide , Zekzer Dan , Lu Yuxin , Dang Hoa , Kaufman Daniel L.
Published: April 2014

The determinant spreading of T cell autoimmunity plays an important role in the pathogenesis of type 1 diabetes and in the protective mechanism of Ag-based immunotherapy in NOD mice. However, little is known about the role of APCs, particularly B cells, in the spreading of T cell autoimmunity. We studied determinant spreading in NOD/scid or Igμ−/− NOD mice reconstituted with NOD T and/or B cells and found that mice with mature B cells (TB NOD/scid and BMB Igμ−/− NOD), but not mice that lacked mature B cells (T NOD/scid and BM Igμ−/− NOD), spontaneously developed Th1 autoimmunity, which spread sequentially among different β cell Ags. Immunization of T NOD/scid and BM Igμ−/− NOD mice with a β cell Ag could prime Ag-specific Th1 or Th2 responses, but those T cell responses did not spread to other β cell Ags. In contrast, immunization of TB NOD/scid and BMB Igμ−/− NOD mice with a β cell Ag in IFA induced Th2 responses, which spread to other β cell Ags. Furthermore, we found that while macrophages and dendritic cells could evoke memory and effector T cell responses in vitro, B cells significantly enhanced the detection of spontaneously primed and induced Th1 responses to β cell Ags. Our data suggest that B cells, but not other APCs, mediate the spreading of T cell responses during the type 1 diabetes process and following Ag-based immunotherapy. Conceivably, the modulation of the capacity of B cells to present Ag may provide new interventions for enhancing Ag-based immunotherapy and controlling autoimmune diseases.
The P2X7 Receptor: A Key Player in IL-1 Processing and Release
Authors: Ferrari Davide , Pizzirani Cinzia , Adinolfi Elena , Lemoli Roberto M. , Curti Antonio , Idzko Marco , Panther Elisabeth , Di Virgilio Francesco
Published: April 2014

Human IL-1 family proteins are key mediators of the host response to infections, injury, and immunologic challenges. The mechanism by which IL-1 activates proinflammatory responses in target cells, and the plasma membrane receptors involved, is fairly well known. This has led to the development of innovative drugs that block IL-1 downstream to its synthesis and secretion. On the contrary, the mechanism of IL-1 and other IL-1 family members (e.g., IL-18) maturation and release is incompletely understood. Accruing evidence points to a plasma membrane receptor for extracellular ATP, the P2X7 receptor, as a key player in both processes. A deeper understanding of the mechanism by which the P2X7 receptor triggers IL-1 maturation and exteriorization may suggest novel avenues for the treatment of inflammatory diseases and provide a deeper insight in the fundamental mechanism of protease activation and cellular export of proteins lacking a leader sequence.
Cutting Edge: Itk-Dependent Signals Required for CD4+ T Cells to Exert, but Not Gain, Th2 Effector Function
Authors: Au-Yeung Byron B. , Katzman Shoshana D. , Fowell Deborah J.
Published: April 2014

The TCR signals for the release of CD4 effector function are poorly understood. Itk plays an essential role in Th2, but not Th1, responses. However, when Itk is required during Th2 development is unclear. We followed the fate of Itk-deficient T cells during Th2 development in vitro and in vivo using an IL-4/GFP reporter. Surprisingly, a similar frequency of itk−/− CD4+ cells differentiated and committed to the Th2 lineage as wild-type cells. However, Itk-deficient Th2 cells failed to exert effector function upon TCR triggering. Loss of function was marked by defective transcriptional enhancement of Th2 cytokines and GATA3. IL-4 production in itk−/− Th2s could be rescued by the expression of kinase-active Itk. Thus, Itk is necessary for the release, but not gain, of Th2 function. We suggest that the liberation of effector function is tightly controlled through qualitative changes in TCR signals, facilitating postdifferentiation regulation of cytokine responses.
Nitric Oxide Promotes Resistance to Tumor Suppression by CTLs
Authors: Su Zhanhai , Kuball Jürgen , Barreiros Ana-Paula , Gottfried Daniela , Ferreira Edite Antunes , Theobald Matthias , Galle Peter R. , Strand Dennis , Strand Susanne
Published: April 2014

Many human tumors express inducible NO synthetase (NOS2), but the roles of NO in tumor development are not fully elucidated. An important step during tumor development is the acquisition of apoptosis resistance. We investigated the dose-dependent effects of endogenously produced NO on apoptosis using ecdysone-inducible NOS2 cell lines. Our results show that short-term NOS2 expression enhances CD95-mediated apoptosis and T cell cytotoxicity dose dependently. Furthermore, we could show that during chronic exposure to NO, besides the primary cytotoxic NO effect, there is selection of cell clones resistant to NO that show cross-resistance to CD95-induced apoptosis and the killing by CTLs. We propose that NO production could initially act as an autocrine suicide or paracrine killing mechanism in cells undergoing malignant transformation. However, once failed, the outcome is fatal. NO promotes tumor formation by enhancing the selection of cells that can evade immune attack by acquiring apoptosis resistance.
Desiccating Stress Induces T Cell-Mediated Sjögren’s Syndrome-Like Lacrimal Keratoconjunctivitis
Authors: Niederkorn Jerry Y. , Stern Michael E. , Pflugfelder Stephen C. , De Paiva Cintia S. , Corrales Rosa M. , Gao Jianping , Siemasko Karyn
Published: April 2014

Chronic dry eye syndrome affects over 10 million people in the United States; it is associated with inflammation of the lacrimal gland (LG) and in some cases involves T cell infiltration of the conjunctiva. We demonstrate that environmental desiccating stress (DS) elicits T cell-mediated inflammation of the cornea, conjunctiva, and LG, but not other organs in mice. The lacrimal keratoconjunctivitis (LKC) was mediated by CD4+ T cells, which, when adoptively transferred to T cell-deficient nude mice, produced inflammation in the LG, cornea, and conjunctiva, but not in any other organ. Adoptively transferred CD4+ T cells produced LKC even though recipients were not exposed to DS. LKC was exacerbated in euthymic mice depleted of CD4+CD25+forkhead/winged helix transcription factor+ regulatory T cells. The results suggest that DS exposes shared epitopes in the cornea, conjunctiva, and LG that induce pathogenic CD4+ T cells that produce LKC, which under normal circumstances is restrained by CD4+CD25+forkhead/winged helix transcription factor+ regulatory T cells.
Essential Role of IκB Kinase α in Thymic Organogenesis Required for the Establishment of Self-Tolerance
Authors: Kinoshita Dan , Hirota Fumiko , Kaisho Tsuneyasu , Kasai Michiyuki , Izumi Keisuke , Bando Yoshimi , Mouri Yasuhiro , Matsushima Akemi , Niki Shino , Han Hongwei , Oshikawa Kiyotaka , Kuroda Noriyuki , Maegawa Masahiko , Irahara Minoru , Takeda Kiyoshi , Akira Shizuo , Matsumoto Mitsuru
Published: April 2014

IκB kinase (IKK) α exhibits diverse biological activities through protein kinase-dependent and -independent functions, the former mediated predominantly through a noncanonical NF-κB activation pathway. The in vivo function of IKKα, however, still remains elusive. Because a natural strain of mice with mutant NF-κB-inducing kinase (NIK) manifests autoimmunity as a result of disorganized thymic structure with abnormal expression of Rel proteins in the thymic stroma, we speculated that the NIK-IKKα axis might constitute an essential step in the thymic organogenesis that is required for the establishment of self-tolerance. An autoimmune disease phenotype was induced in athymic nude mice by grafting embryonic thymus from IKKα-deficient mice. The thymic microenvironment that caused autoimmunity in an IKKα-dependent manner was associated with defective processing of NF-κB2, resulting in the impaired development of thymic epithelial cells. Thus, our results demonstrate a novel function for IKKα in thymic organogenesis for the establishment of central tolerance that depends on its protein kinase activity in cooperation with NIK.
Induction of Peripheral T Cell Tolerance by Antigen-Presenting B Cells. I. Relevance of Antigen Presentation Persistence
Authors: Raimondi Giorgio , Zanoni Ivan , Citterio Stefania , Ricciardi-Castagnoli Paola , Granucci Francesca
Published: April 2014

Various mechanisms of peripheral T cell tolerization have evolved to avoid responses mediated by autoreactive T cells that have not been eliminated in the thymus. In this study, we investigated the peripheral conditions of Ag presentation required to induce T cell tolerance when the predominant APCs are B cells. We show that transient Ag presentation, in absence of inflammation and in a self-context, induces CD4+ T cell activation and memory formation. In contrast, chronic Ag presentation leads to CD4+ T cell tolerance. The importance of long-lasting Ag presentation in inducing tolerance was also confirmed in the herpes stromal keratitis autoimmune disease model. Keratogenic T cells could be activated or tolerized depending on the APC short or long persistence. Thus, when APCs are B cells, the persistence of the Ag presentation itself is one of the main conditions to have peripheral T cell tolerance.
Induction of Peripheral T Cell Tolerance by Antigen-Presenting B Cells. II. Chronic Antigen Presentation Overrules Antigen-Presenting B Cell Activation
Authors: Raimondi Giorgio , Zanoni Ivan , Citterio Stefania , Ricciardi-Castagnoli Paola , Granucci Francesca
Published: April 2014

Ag presentation in the absence of danger signals and Ag persistence are the inductive processes of peripheral T cell tolerization proposed so far. Nevertheless, it has never been definitively shown that chronic Ag presentation per se can induce T cell tolerance independent of the state of activation of APCs. In the present work, we investigated whether chronic Ag presentation by either resting or activated B cells can induce tolerance of peripheral Ag-specific T cells. We show that CD4+ T cells that re-encounter the Ag for a prolonged period, presented either by resting or activated Ag-presenting B cells, become nonfunctional and lose any autoimmune reactivity. Thus, when the main APCs are B cells, the major mechanism responsible for peripheral T cell tolerization is persistent Ag exposure, independent of the B cell activation state.
Suppressor of Cytokine Signaling 1 Stringently Regulates Distinct Functions of IL-7 and IL-15 In Vivo during T Lymphocyte Development and Homeostasis
Authors: Ramanathan Sheela , Gagnon Julien , Leblanc Chantal , Rottapel Robert , Ilangumaran Subburaj
Published: April 2014

SOCS1 −/− mice accumulate within the thymus and periphery CD8+ lymphocytes that express memory cell markers and display heightened in vitro responses to common γ-chain cytokines. To investigate whether dysregulated homeostasis of T lymphocytes and acquisition of memory phenotype by CD8+ cells in SOCS1−/− mice were mediated by IL-7 and/or IL-15 in vivo, we have generated SOCS1−/−IL-7−/−, SOCS1−/−IL-15−/− and SOCS1−/−IL-7−/−IL-15−/− mice. We observed that in mice lacking SOCS1, either IL-7 or IL-15 skewed thymocyte development toward CD8 lineage, whereas IL-15 is the principal mediator of dysregulated homeostasis in the periphery. Homeostatic proliferation of SOCS1−/− CD8+ lymphocytes in Rag1−/−, Rag1−/−IL-7−/−, Rag1−/−IL-15−/−, and Rag1−/−IL-7−/−IL-15−/− mice showed that SOCS1 deficiency did not overcome the requirement for IL-7 and IL-15 to sustain homeostatic expansion. Differential expression of memory phenotype markers CD44, CD122, and Ly6C by SOCS1−/−IL-15−/− CD8+ lymphocytes suggest that multiple signals contributed to the memory cell differentiation program. To address whether increased IL-15 responsiveness of SOCS1−/− CD8+ lymphocytes required prior TCR sensitization, we generated SOCS1−/− H-Y TCR transgenic (Tg) mice. Using female SOCS1−/− H-Y TCRtg mice in Rag1+/+ and Rag1−/− backgrounds, we show that acquisition of the memory phenotype by SOCS1-deficient CD8+ lymphocytes did not require prior antigenic stimulation, but required the presence of activated T cells. SOCS1 deficiency accelerated the maturation of CD8 single-positive thymocytes expressing Tg TCR, but did not compromise negative selection in HY-TCRtg males. Our findings illustrate distinct functions for IL-7 and IL-15 in T lymphocyte development and homeostasis, and stringent regulation of these processes by SOCS1.
Immunization-Induced Perturbation of Human Blood Plasma Cell Pool: Progressive Maturation, IL-6 Responsiveness, and High PRDI-BF1/BLIMP1 Expression Are Critical Distinctions between Antigen-Specific and Nonspecific Plasma Cells
Authors: González-García Inés , Ocaña Esther , Jiménez-Gómez Gema , Campos-Caro Antonio , Brieva José A.
Published: April 2014

The present study shows that reimmunization with tetanus toxoid (tet) caused a transient increase of the human blood plasma cell (PC) pool, detectable from 6th to 15th day postboost, as well as the temporal alteration of several PC features. Labeling of specific PC with FITC-tet C fragment (tetC) allowed kinetics analysis of the tetC+ and tetC− PC, and revealed remarkable differences between them: 1) the kinetics of tetC+ PC occurrence was exponential, and most of them appeared in a narrow time frame (5th to 8th day postboost), whereas the tetC− PC increase was lower (three to five times) and more prolonged (4th to 15th day postboost). 2) The tetC+ PC subset contained a fraction of cycling cells, expressed high levels of DR, CD138, and CD126, and responded to IL-6 by improving their survival and Ig secretion; in contrast, the tetC− PC showed higher CXCR4 and lower DR and CD138, did not respond to IL-6, and contained a fraction of apoptotic cells. 3) Sequential phenotypic analysis revealed maturational changes within the tetC+, but not tetC−, PC subset; sequencing of tetC+ PC IgVH genes showed clear features of Ag selection. 4) The tetC+ PC expressed several times more positive regulatory domain I- binding factor 1/B lymphocyte-induced maturation protein 1 transcription factor than the tetC− PC. 5) The tetC− PC and bone marrow resident PC similarly expressed low DR and high CXCR4, but differed in that the latter exhibited higher levels of CD31, CD138, and positive regulatory domain I- binding factor 1/B lymphocyte-induced maturation protein 1. These findings support the view that tetC+ PC contain bone marrow PC precursors, and tetC− PC probably belong to a removable compartment of aged PC.
Effector T Cell Differentiation and Memory T Cell Maintenance Outside Secondary Lymphoid Organs
Authors: Obhrai Jagdeep S. , Oberbarnscheidt Martin H. , Hand Timothy W. , Diggs Lonnette , Chalasani Geetha , Lakkis Fadi G.
Published: April 2014

Naive T cell circulation is restricted to secondary lymphoid organs. Effector and memory T cells, in contrast, acquire the ability to migrate to nonlymphoid tissues. In this study we examined whether nonlymphoid tissues contribute to the differentiation of effector T cells to memory cells and the long-term maintenance of memory T cells. We found that CD4, but not CD8, effector T cell differentiation to memory cells is impaired in adoptive hosts that lack secondary lymphoid organs. In contrast, established CD4 and CD8 memory T cells underwent basal homeostatic proliferation in the liver, lungs, and bone marrow, were maintained long-term, and functioned in the absence of secondary lymphoid organs. CD8 memory T cells found in nonlymphoid tissues expressed both central and effector memory phenotypes, whereas CD4 memory T cells displayed predominantly an effector memory phenotype. These findings indicate that secondary lymphoid organs are not necessary for the maintenance and function of memory T cell populations, whereas the optimal differentiation of CD4 effectors to memory T cells is dependent on these organs. The ability of memory T cells to persist and respond to foreign Ag independently of secondary lymphoid tissues supports the existence of nonlymphoid memory T cell pools that provide essential immune surveillance in the periphery.
Impact of HLA-B Alleles, Epitope Binding Affinity, Functional Avidity, and Viral Coinfection on the Immunodominance of Virus-Specific CTL Responses
Authors: Bihl Florian , Frahm Nicole , Di Giammarino Loriana , Sidney John , John Mina , Yusim Karina , Woodberry Tonia , Sango Kaori , Hewitt Hannah S. , Henry Leah , Linde Caitlyn H. , Chisholm John V. , Zaman Tauheed M. , Pae Eunice , Mallal Simon , Walker Bruce D. , Sette Alessandro , Korber Bette T. , Heckerman David , Brander Christian
Published: April 2014

Immunodominance is variably used to describe either the most frequently detectable response among tested individuals or the strongest response within a single individual, yet factors determining either inter- or intraindividual immunodominance are still poorly understood. More than 90 individuals were tested against 184 HIV- and 92 EBV-derived, previously defined CTL epitopes. The data show that HLA-B-restricted epitopes were significantly more frequently recognized than HLA-A- or HLA-C-restricted epitopes. HLA-B-restricted epitopes also induced responses of higher magnitude than did either HLA-A- or HLA-C-restricted epitopes, although this comparison only reached statistical significance for EBV epitopes. For both viruses, the magnitude and frequency of recognition were correlated with each other, but not with the epitope binding affinity to the restricting HLA allele. The presence or absence of HIV coinfection did not impact EBV epitope immunodominance patterns significantly. Peptide titration studies showed that the magnitude of responses was associated with high functional avidity, requiring low concentration of cognate peptide to respond in in vitro assays. The data support the important role of HLA-B alleles in antiviral immunity and afford a better understanding of the factors contributing to inter- and intraindividual immunodominance.
Mast Cell-Associated TNF Promotes Dendritic Cell Migration
Authors: Suto Hajime , Nakae Susumu , Kakurai Maki , Sedgwick Jonathon D. , Tsai Mindy , Galli Stephen J.
Published: April 2014

Mast cells represent a potential source of TNF, a mediator which can enhance dendritic cell (DC) migration. Although the importance of mast cell-associated TNF in regulating DC migration in vivo is not clear, mast cells and mast cell-derived TNF can contribute to the expression of certain models of contact hypersensitivity (CHS). We found that CHS to FITC was significantly impaired in mast cell-deficient KitW-sh/W-sh or TNF−/− mice. The reduced expression of CHS in KitW-sh/W-sh mice was fully repaired by local transfer of wild-type bone marrow-derived cultured mast cells (BMCMCs), but was only partially repaired by transfer of TNF−/− BMCMCs. Thus, mast cells, and mast cell-derived TNF, were required for optimal expression of CHS to FITC. We found that the migration of FITC-bearing skin DCs into draining lymph nodes (LNs) 24 h after epicutaneous administration of FITC in naive mice was significantly reduced in mast cell-deficient or TNF−/− mice, but levels of DC migration in these mutant mice increased to greater than wild-type levels by 48 h after FITC sensitization. Mast cell-deficient or TNF−/− mice also exhibited significantly reduced migration of airway DCs to local LNs at 24 h after intranasal challenge with FITC-OVA. Migration of FITC-bearing DCs to LNs draining the skin or airways 24 h after sensitization was repaired in KitW-sh/W-sh mice which had been engrafted with wild-type but not TNF−/− BMCMCs. Our findings indicate that mast cell-associated TNF can contribute significantly to the initial stages of FITC-induced migration of cutaneous or airway DCs.
Mast Cell-Dependent Down-Regulation of Antigen-Specific Immune Responses by Mosquito Bites
Authors: Depinay Nadya , Hacini Fériel , Beghdadi Walid , Peronet Roger , Mécheri Salaheddine
Published: April 2014

While probing host skin to search for blood vessels, the female Anopheles mosquito delivers Plasmodium parasites in the presence of saliva. Saliva from various blood-feeding vectors which contains several pharmacologically active components is believed to facilitate blood feeding as well as parasite transmission to the host. Recently, we found that mosquito saliva has the capacity to activate dermal mast cells and to induce local inflammatory cell influx. Our main objective in the present work is to investigate whether saliva, through mosquito bites, controls the magnitude of Ag-specific immune responses and whether this control is dependent on the mast cell-mediated inflammatory response. Using a mast cell knockin mouse model, we found that mosquito bites consistently induced MIP-2 in the skin and IL-10 in draining lymph nodes, and down-regulate Ag-specific T cell responses by a mechanism dependent on mast cells and mediated by IL-10. Our results provide evidence for new mechanisms which may operate during Plasmodium parasite transmission by mosquito bites.
A Novel NF-κB Binding Site Controls Human Granzyme B Gene Transcription
Authors: Huang Chunjian , Bi Enguang , Hu Yu , Deng Weiwen , Tian Zhigang , Dong Chen , Hu Yuanjie , Sun Bing
Published: April 2014

Granzyme B expression is essential for eliciting NK cell cytotoxicity and T cell function. However, its transcriptional regulatory mechanism is not well understood. In this report, we demonstrate in human NK cells and T cells that the NF-κB-signaling pathway is involved in such control. Furthermore, a novel downstream human granzyme B gene sequence (GGAGATTCCC) was identified for NF-κB binding. EMSA, luciferase, and chromatin immunoprecipitation assays in vitro and in vivo indicated that this NF-κB binding site is functional in an NK cell line and its primary counterpart. Our data also demonstrate that this binding site is functional in Jurkat T cells. Taken together, we identified a novel NF-κB binding site, which plays a pivotal role in controlling human granzyme B gene transcription.
Transactivator of Transcription from HIV Type 1 Subtype E Selectively Inhibits TNF Gene Expression via Interference with Chromatin Remodeling of the TNF Locus
Authors: Ranjbar Shahin , Rajsbaum Ricardo , Goldfeld Anne E.
Published: April 2014

The transactivator of transcription (Tat) protein is essential for efficient HIV type 1 (HIV-1) replication and is involved in the transcriptional regulation of the host immune response gene, TNF. In this study, we demonstrate that Tat proteins from representative HIV-1 subtype E isolates, but not from subtypes B or C, selectively inhibit TNF gene transcription and protein production in CD4+ Jurkat T cells. Strikingly, we show that this repression is due to a tryptophan at residue 32 of Tat E and is secondary to interference with recruitment of the histone acetyltransferase P/CAF to the TNF promoter and with chromatin remodeling of the TNF locus. This study presents a novel mechanism by which HIV-1 manipulates a host immune response gene that is important in its own replication. Moreover, these results demonstrate a new mechanism by which the TNF gene is regulated via chromatin remodeling secondary to viral infection.
Costimulatory Receptors in a Teleost Fish: Typical CD28, Elusive CTLA4
Authors: Bernard David , Riteau Béatrice , Hansen John D. , Phillips Ruth B. , Michel Frédérique , Boudinot Pierre , Benmansour Abdenour
Published: April 2014

T cell activation requires both specific recognition of the peptide-MHC complex by the TCR and additional signals delivered by costimulatory receptors. We have identified rainbow trout sequences similar to CD28 (rbtCD28) and CTLA4 (rbtCTLA4). rbtCD28 and rbtCTLA4 are composed of an extracellular Ig-superfamily V domain, a transmembrane region, and a cytoplasmic tail. The presence of a conserved ligand binding site within the V domain of both molecules suggests that these receptors likely recognize the fish homologues of the B7 family. The mRNA expression pattern of rbtCD28 and rbtCTLA4 in naive trout is reminiscent to that reported in humans and mice, because rbtCTLA4 expression within trout leukocytes was quickly up-regulated following PHA stimulation and virus infection. The cytoplasmic tail of rbtCD28 possesses a typical motif that is conserved in mammalian costimulatory receptors for signaling purposes. A chimeric receptor made of the extracellular domain of human CD28 fused to the cytoplasmic tail of rbtCD28 promoted TCR-induced IL-2 production in a human T cell line, indicating that rbtCD28 is indeed a positive costimulator. The cytoplasmic tail of rbtCTLA4 lacked obvious signaling motifs and accordingly failed to signal when fused to the huCD28 extracellular domain. Interestingly, rbtCTLA4 and rbtCD28 are not positioned on the same chromosome and thus do not belong to a unique costimulatory cluster as in mammals. Finally, our results raise questions about the origin and evolution of positive and negative costimulation in vertebrate immune systems.
Role of Fyn in the Rearrangement of Tubulin Cytoskeleton Induced through TCR
Authors: Martín-Cófreces Noa B. , Sancho David , Fernández Edgar , Vicente-Manzanares Miguel , Gordón-Alonso Mónica , Montoya María C. , Michel Frédérique , Acuto Oreste , Alarcón Balbino , Sánchez-Madrid Francisco
Published: April 2014

The translocation of the microtubule-organizing center (MTOC), its associated signaling complex, and the secretory apparatus is the most characteristic early event that involves the tubulin cytoskeleton of T or NK cells after their interaction with APC or target cells. Our results show that Fyn kinase activity is essential for MTOC reorientation in an Ag-dependent system. Moreover, T cells from Fyn-deficient mice are unable to rearrange their tubulin cytoskeleton in response to anti-CD3-coated beads. Analysis of conjugates of T cells from transgenic OT-I mice with dendritic cells revealed that an antagonist peptide induces translocation of the MTOC, and that this process is impaired in T cells from Fyn−/− OT-I mice. In addition, Fyn deficiency significantly affects the MTOC relocation mediated by agonist peptide stimulation. These results reveal Fyn to be a key regulator of tubulin cytoskeleton reorganization in T cells.
CXCL10 Is the Key Ligand for CXCR3 on CD8+ Effector T Cells Involved in Immune Surveillance of the Lymphocytic Choriomeningitis Virus-Infected Central Nervous System
Authors: Christensen Jeanette Erbo , de Lemos Carina , Moos Torben , Christensen Jan Pravsgaard , Thomsen Allan Randrup
Published: April 2014

IFN-γ-inducible protein 10/CXCL10 is a chemokine associated with type 1 T cell responses, regulating the migration of activated T cells through binding to the CXCR3 receptor. Expression of both CXCL10 and CXCR3 are observed during immunopathological diseases of the CNS, and this receptor/ligand pair is thought to play a central role in regulating T cell-mediated inflammation in this organ site. In this report, we investigated the role of CXCL10 in regulating CD8+ T cell-mediated inflammation in the virus-infected brain. This was done through analysis of CXCL10-deficient mice infected intracerebrally with lymphocytic choriomeningitis virus, which in normal immunocompetent mice induces a fatal CD8+ T cell-mediated meningoencephalitis. We found that a normal antiviral CD8+ T cell response was generated in CXCL10-deficient mice, and that lack of CXCL10 had no influence on the accumulation of mononuclear cells in the cerebrospinal fluid. However, analysis of the susceptibility of CXCL10-deficient mice to lymphocytic choriomeningitis virus-induced meningitis revealed that these mice just like CXCR3-deficient mice were partially resistant to this disease, whereas wild-type mice invariably died. Furthermore, despite marked up-regulation of the two remaining CXCR3 ligands: CXCL9 and 11, we found a reduced accumulation of CD8+ T cells in the brain parenchyma around the time point when wild-type mice succumb as a result of CD8+ T cell-mediated inflammation. Thus, taken together these results indicate a central role for CXCL10 in regulating the accumulation of effector T cells at sites of CNS inflammation, with no apparent compensatory effect of other CXCR3 ligands.
Trypsin-Sensitive Modulation of Intestinal Epithelial MD-2 as Mechanism of Lipopolysaccharide Tolerance
Authors: Cario Elke , Golenbock Douglas T. , Visintin Alberto , Rünzi Michael , Gerken Guido , Podolsky Daniel K.
Published: April 2014

Intestinal epithelial cells (IEC) are constantly exposed to both high concentrations of the bacterial ligand LPS and the serine protease trypsin. MD-2, which contains multiple trypsin cleavage sites, is an essential accessory glycoprotein required for LPS recognition and signaling through TLR4. The aim of this study was to characterize the expression and subcellular distribution of intestinal epithelial MD-2 and to delineate potential functional interactions with trypsin and then alteration in inflammatory bowel disease (IBD). Although MD-2 protein expression was minimal in primary IEC of normal colonic or ileal mucosa, expression was significantly increased in IEC from patients with active IBD colitis, but not in ileal areas from patients with severe Crohn’s disease. Endogenous MD-2 was predominantly retained in the calnexin-calreticulin cycle of the endoplasmic reticulum; only a small fraction was exported to the Golgi. MD-2 expression correlated inversely with trypsin activity. Biochemical evidence and in vitro experiments demonstrated that trypsin exposure resulted in extensive proteolysis of endogenous and soluble MD-2 protein, but not of TLR4 in IEC, and was associated with desensitization of IEC to LPS. In conclusion, the present study suggests that endoplasmic reticulum-associated MD-2 expression in IBD may be altered by ileal protease in inflammation, leading to impaired LPS recognition and hyporesponsiveness through MD-2 proteolysis in IEC, thus implying a physiologic mechanism that helps maintain LPS tolerance in the intestine.
TLRs Regulate the Gatekeeping Functions of the Intestinal Follicle-Associated Epithelium
Authors: Chabot Sophie , Wagner Jessica S. , Farrant Stephanie , Neutra Marian R.
Published: April 2014

Initiation of adaptive mucosal immunity occurs in organized mucosal lymphoid tissues such as Peyer’s patches of the small intestine. Mucosal lymphoid follicles are covered by a specialized follicle-associated epithelium (FAE) that contains M cells, which mediate uptake and transepithelial transport of luminal Ags. FAE cells also produce chemokines that attract Ag-presenting dendritic cells (DCs). TLRs link innate and adaptive immunity, but their possible role in regulating FAE functions is unknown. We show that TLR2 is expressed in both FAE and villus epithelium, but TLR2 activation by peptidoglycan or Pam3Cys injected into the intestinal lumen of mice resulted in receptor redistribution in the FAE only. TLR2 activation enhanced transepithelial transport of microparticles by M cells in a dose-dependent manner. Furthermore, TLR2 activation induced the matrix metalloproteinase-dependent migration of subepithelial DCs into the FAE, but not into villus epithelium of wild-type and TLR4-deficient mice. These responses were not observed in TLR2-deficient mice. Thus, the FAE of Peyer’s patches responds to TLR2 ligands in a manner that is distinct from the villus epithelium. Intraluminal LPS, a TLR4 ligand, also enhanced microparticle uptake by the FAE and induced DC migration into the FAE, suggesting that other TLRs may modulate FAE functions. We conclude that TLR-mediated signals regulate the gatekeeping functions of the FAE to promote Ag capture by DCs in organized mucosal lymphoid tissues.
Complement Component C3 Is Required for Protective Innate and Adaptive Immunity to Larval Strongyloides stercoralis in Mice
Authors: Kerepesi Laura A. , Hess Jessica A. , Nolan Thomas J. , Schad Gerhard A. , Abraham David
Published: April 2014

This study examines the role of complement components C3 and C5 in innate and adaptive protective immunity to larval Strongyloides stercoralis in mice. Larval survival in naive C3−/− mice was increased as compared with survival in wild-type mice, whereas C3aR−/− and wild-type mice had equivalent levels of larval killing. Larval killing in naive mice was shown to be a coordinated effort between effector cells and C3. There was no difference between survival in wild-type and naive C5−/− mice, indicating that C5 was not required during the innate immune response. Naive B cell-deficient and wild-type mice killed larvae at comparable levels, suggesting that activation of the classical complement pathway was not required for innate immunity. Adaptive immunity was equivalent in wild-type and C5−/− mice; thus, C5 was also not required during the adaptive immune response. Larval killing was completely ablated in immunized C3−/− mice, even though the protective parasite-specific IgM response developed and effector cells were recruited. Protective immunity was restored to immunized C3−/− mice by transferring untreated naive serum, but not C3-depleted heat-inactivated serum to the location of the parasites. Finally, immunized C3aR−/− mice killed larvae during the adaptive immune response as efficiently as wild-type mice. Therefore, C3 was not required for the development of adaptive immunity, but was required for the larval killing process during both protective innate and adaptive immune responses in mice against larval S. stercoralis.
Mycobacterium tuberculosis19-kDa Lipoprotein Inhibits IFN-γ-Induced Chromatin Remodeling ofMHC2TAby TLR2 and MAPK Signaling
Authors: Pennini Meghan E. , Pai Rish K. , Schultz David C. , Boom W. Henry , Harding Clifford V.
Published: April 2014

During infection of macrophages, prolonged signaling by Mycobacterium tuberculosis (Mtb) or its 19-kDa lipoprotein (LpqH; Rv3763) inhibits IFN-γ-induced expression of several immune function genes, including class II transactivator (CIITA), which regulates class II MHC. Mtb does not inhibit early IFN-γ signaling events, e.g., Stat1α activation. This study analyzed downstream mechanisms that regulate the transcription of MHC2TA, the gene encoding CIITA. Chromatin immunoprecipitation showed that IFN-γ induced acetylation of histones H3 and H4 at the CIITA promoter IV (pIV). In contrast, IFN-γ-dependent histone acetylation at CIITA pIV was inhibited by Mtb or 19-kDa lipoprotein. Mtb 19-kDa lipoprotein also inhibited IFN-γ-dependent recruitment of Brahma-related gene 1, a chromatin remodeling protein, to CIITA pIV. Mtb 19-kDa lipoprotein did not inhibit histone acetylation in TLR2−/− macrophages. Furthermore, 19-kDa lipoprotein did not inhibit CIITA expression or IFN-γ-dependent histone acetylation of CIITA pIV in macrophages treated with inhibitors of MAPKs p38 or ERK. Thus, CIITA expression was inhibited by TLR2-induced MAPK signaling that caused histone hypoacetylation at CIITA pIV and suppression of CIITA transcription. Chromatin remodeling at MHC2TA is a novel target of inhibition by Mtb. These mechanisms may diminish class II MHC expression by infected macrophages, contributing to immune evasion by Mtb.
Type I IFN Receptor Signals Directly Stimulate Local B Cells Early following Influenza Virus Infection
Authors: Coro Elizabeth S. , Chang W. L. William , Baumgarth Nicole
Published: April 2014

Rapidly developing Ab responses to influenza virus provide immune protection even during a primary infection. How these early B cell responses are regulated is incompletely understood. In this study, we show that the first direct stimulatory signal for local respiratory tract B cells during influenza virus infection is provided through the type I IFNR. IFNR-mediated signals were responsible for the influenza infection-induced local but not systemic up-regulation of CD69 and CD86 on virtually all lymph node B cells and for induction of a family of IFN-regulated genes within 48 h of infection. These direct IFNR-mediated signals were shown to affect both the magnitude and quality of the local virus-specific Ab response. Thus, ligand(s) of the type I IFNR are direct nonredundant early innate signals that regulate local antiviral B cell responses.
Role of the Property of C-Reactive Protein to Activate the Classical Pathway of Complement in Protecting Mice from Pneumococcal Infection
Authors: Suresh Madathilparambil V. , Singh Sanjay K. , Ferguson Donald A. , Agrawal Alok
Published: April 2014

C-reactive protein (CRP) is not an acute-phase protein in mice, and therefore, mice are widely used to investigate the functions of human CRP. It has been shown that CRP protects mice from pneumococcal infection, and an active complement system is required for full protection. In this study, we assessed the contribution of CRP’s ability of activating the classical pathway of complement in the protection of mice from lethal infection with virulent Streptococcus pneumoniae type 3. We used two CRP mutants, Y175A and K114A. The Y175A CRP does not bind C1q and does not activate complement in human serum. The K114A CRP binds C1q and activates complement more efficiently than wild-type CRP. Passively administered, both CRP mutants and the wild-type CRP protected mice from infection equally. Infected mice injected with wild-type or mutant CRP had reduced bacteremia, resulting in lower mortality and increased longevity compared with mice that did not receive CRP. Thus, the protection of mice was independent of CRP-mediated activation of the classical pathway of complement. To confirm that human CRP does not differentiate between human and mouse complement, we analyzed the binding of human CRP to mouse C1q. Surprisingly, CRP did not react with mouse C1q, although both mutant and wild-type CRP activated mouse C3, indicating species specificity of CRP-C1q interaction. We conclude that the mouse is an unfit animal for exploring CRP-mediated activation of the classical complement pathway, and that the characteristic of CRP to activate the classical complement pathway has no role in protecting mice from infection.
Ecto-5′-Nucleotidase (CD73)-Mediated Adenosine Production Is Tissue Protective in a Model of Bleomycin-Induced Lung Injury
Authors: Volmer Jonathan B. , Thompson Linda F. , Blackburn Michael R.
Published: April 2014

Adenosine signaling has diverse actions on inflammation and tissue injury. Levels of adenosine are rapidly elevated in response to tissue injury; however, the mechanisms responsible for adenosine production in response to injury are not well understood. In this study, we found that adenosine levels are elevated in the lungs of mice injured by the drug bleomycin. In addition, increased activity of ecto-5′-nucleotidase (CD73) was found in the lungs in conjunction with adenosine elevations. To determine the contribution of CD73 to the generation of adenosine in the lung, CD73−/− mice were subjected to bleomycin challenges. Results demonstrated that CD73−/− mice challenged with bleomycin no longer accumulated adenosine in their lungs, suggesting that the primary means of adenosine production following bleomycin injury resulted from the release and subsequent dephosphorylation of adenine nucleotides. CD73−/− mice challenged with bleomycin exhibited enhanced pulmonary inflammation and fibrosis as well as exaggerated expression of proinflammatory and profibrotic mediators in the lung. Intranasal instillations of exogenous nucleotidase restored the ability of lungs of CD73−/− mice to accumulate adenosine following bleomycin challenge. Furthermore, these treatments were associated with a decrease in pulmonary inflammation and fibrosis. CD73+/+ animals challenged with bleomycin and supplemented with exogenous nucleotidase also exhibited reduced inflammation. Together, these findings suggest that CD73-dependent adenosine production contributes to anti-inflammatory pathways in bleomycin-induced lung injury.
Monitoring the Antitumor Response of Naive and Memory CD8 T Cells in RAG1−/− Mice by Positron-Emission Tomography
Authors: Su Helen , Chang Daisy S. , Gambhir Sanjiv S. , Braun Jonathan
Published: April 2014

Therapeutic antitumor immunity depends on a highly migratory CTL population capable of activation and trafficking between lymphoid and tumor-bearing microanatomic sites. We recently adapted positron-emission tomography gene expression imaging for noninvasive, longitudinal localization and quantitation of antitumor T lymphocyte migration in vivo. In this study, we apply this system to enumerate the temporal accumulation of naive vs memory T cells. Naive or memory OT-1 CD8+ T cells, retrovirally marked with the sr39TK gene, were adoptively transferred into RAG1−/− animals bearing EL-4 or EG.7 (an OVA-expressing subline), and repetitively imaged by microPET over several weeks. Memory cells demonstrated early accumulation and apparent proliferation, with large T cell numbers at the Ag-positive tumor as early as day 1 after T cell transfer. Naive T cells did not accumulate in the E.G7 tumor until day 8, and reached only 25% of the peak levels achieved by memory T cells. Both naive and memory cells eradicated the Ag-expressing tumor at a comparable density of intratumoral T cells (2–4 × 106/g). However, due to the slower rate of T cell expansion and continued tumor growth, naive cells required ∼10-fold higher Ag-specific precursor frequency to reach a tumoricidal cell density. As recently reported, memory but not naive T cells accumulated in local lymph nodes and lungs, where they persisted as a resident population after tumor eradication. Positron-emission tomography-based immunologic imaging is a noninvasive modality providing unique and meaningful information on the dynamics of the antitumor CTL response.
The Potential of Adiponectin in Driving Arthritis
Authors: Ehling Angela , Schäffler Andreas , Herfarth Hans , Tarner Ingo H. , Anders Sven , Distler Oliver , Paul Gisela , Distler Jörg , Gay Steffen , Schölmerich Jürgen , Neumann Elena , Müller-Ladner Ulf
Published: April 2014

Articular adipose tissue is a ubiquitous component of human joints, but its local functions are largely unknown. Because recent studies revealed several links between adipose tissue, adipocytokines, and arthritis, we investigated the expression of the adipocytokine adiponectin and its functional role in articular adipose tissue and synovium of patients with different arthritides. In contrast to its protective role in endocrinological and vascular diseases, adiponectin was found to be involved in key pathways of inflammation and matrix degradation in the human joint. The effects of adiponectin in human synovial fibroblasts appear to be highly selective by inducing only two of the main mediators of rheumatoid arthritis pathophysiology, IL-6 and matrix metalloproteinase-1, via the p38 MAPK pathway. Owing to the observation that these effects could be inhibited by different TNF-α inhibitors, adipocytokines such as adiponectin may also be key targets for therapeutic strategies in inflammatory joint diseases. In summary, articular adipose tissue and adipocytokines cannot be regarded as innocent bystanders any more in chronic inflammatory diseases such as arthritis.
Cutting Edge: Lentiviral Short Hairpin RNA Silencing of PTEN in Human Mast Cells Reveals Constitutive Signals That Promote Cytokine Secretion and Cell Survival
Authors: Furumoto Yasuko , Brooks Steve , Olivera Ana , Takagi Yasuomi , Miyagishi Makoto , Taira Kazunari , Casellas Rafael , Beaven Michael A. , Gilfillan Alasdair M. , Rivera Juan
Published: April 2014

Engagement of the FcεRI expressed on mast cells induces the production of phosphatidylinositol 3, 4, 5-trisphosphate by PI3K, which is essential for the functions of the cells. PTEN (phosphatase and tensin homologue deleted on chromosome ten) directly opposes PI3K by dephosphorylating phosphatidylinositol 3, 4, 5-trisphosphate at the 3′ position. In this work we used a lentivirus-mediated short hairpin RNA gene knockdown method to study the role of PTEN in CD34+ peripheral blood-derived human mast cells. Loss of PTEN caused constitutive phosphorylation of Akt, p38 MAPK, and JNK, as well as cytokine production and enhancement in cell survival, but not degranulation. FcεRI engagement of PTEN-deficient cells augmented signaling downstream of Src kinases and increased calcium flux, degranulation, and further enhanced cytokine production. PTEN-deficient cells, but not control cells, were resistant to inhibition of cytokine production by wortmannin, a PI3K inhibitor. The findings demonstrate that PTEN functions as a key regulator of mast cell homeostasis and FcεRI- responsiveness.
CTLA-4 Engagement and Regulatory CD4+CD25+ T Cells Independently Control CD8+-Mediated Responses under Costimulation Blockade
Authors: Coenen Jeroen J. A. , Koenen Hans J. P. M. , van Rijssen Esther , Boon Louis , Joosten Irma , Hilbrands Luuk B.
Published: April 2014

Blockade of costimulatory signals is a promising therapeutic target to prevent allograft rejection. In this study, we sought to characterize to what extent CTLA-4 engagement contributes to the development of transplantation tolerance under the cover of CD40/CD40L and CD28/CD86 blockade. In vitro, we found that inhibition of the primary alloresponse and induction of alloantigen hyporesponsiveness by costimulation blockade was abrogated by anti-CTLA-4 mAb. In addition, regulatory CD4+CD25+ T cells (TREG) were confirmed to play a critical role in the induction of hyporesponsiveness by anti-CD40L and anti-CD86 mAb. Our data indicated that CTLA-4 engagement is not required for activation or suppressor function of TREG. Instead, in the absence of either CTLA-4 signaling or TREG, CD8+ T cell division was enhanced, whereas the inhibition of CD4+ T cell division by costimulation blockade remained largely unaffected. In vivo, the administration of additional anti-CTLA-4 mAb abrogated anti-CD40L- and anti-CD86 mAb-induced cardiac allograft survival. Correspondingly, rejection was accompanied by enhanced allograft infiltration of CD8+ cells. We conclude that CTLA-4 signaling and TREG independently cooperate in the inhibition of CD8+ T cell expansion under costimulation blockade.