bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced Th1 Response toStaphylococcus aureusInfection in Human Lactoferrin-Transgenic Mice
Authors: Guillén Cristina , McInnes Iain B. , Vaughan Diane M. , Kommajosyula Sharada , Van Berkel Patrick H. C. , Leung Bernard P. , Aguila Antonio , Brock Jeremy H.
Published: April 2014

Lactoferrin (Lf) is an iron-binding protein of external secretions and neutrophil secondary granules with antimicrobial and immunomodulatory activities. To further define these properties of Lf, we have investigated the response to Staphylococcus aureus infection in transgenic mice carrying a functional human Lf gene. The transgenic mice cleared bacteria significantly better than congenic littermates, associated with a trend to reduced incidence of arthritis, septicemia, and mortality. We identified two pathways by which S. aureus clearance was enhanced. First, human Lf directly inhibited the growth of S. aureus LS-1 in vitro. Second, S. aureus-infected transgenic mice exhibited enhanced Th1 immune polarization. Thus, spleen cells from infected transgenic mice produced higher levels of TNF-α and IFN-γ and less IL-5 and IL-10 upon stimulation ex vivo with the exotoxin toxic shock syndrome toxin-1 compared with congenic controls. To confirm that these effects of Lf transgene expression could occur in the absence of live bacterial infection, we also showed that Lf-transgenic DBA/1 mice exhibited enhanced severity of collagen-induced arthritis, an established model of Th1-induced articular inflammation. Higher levels of stainable iron in the spleens of transgenic mice correlated with human Lf distribution, but all other parameters of iron metabolism did not differ between transgenic mice and wild-type littermates. These results demonstrate that human Lf can mediate both antimicrobial and immunomodulatory activities with downstream effects on the outcome of immune pathology in infectious and inflammatory disease.
Antibody-Mediated Control of Persistent γ-Herpesvirus Infection
Authors: Kim In-Jeong , Flaño Emilio , Woodland David L. , Blackman Marcia A.
Published: April 2014

The human γ-herpesviruses, EBV and Kaposi’s sarcoma-associated herpesvirus, establish life-long latency and can reactivate in immunocompromised individuals. T cells play an important role in controlling persistent EBV infection, whereas a role for humoral immunity is less clear. The murine γ-herpesvirus-68 has biological and structural similarities to the human γ-herpesviruses, and provides an important in vivo experimental model for dissecting mechanisms of immune control. In the current studies, CD28−/− mice were used to address the role of Abs in control of persistent murine γ-herpesvirus-68 infection. Lytic infection was controlled in the lungs of CD28−/− mice, and latency was maintained in B cells at normal frequencies. Although class-switched virus-specific Abs were initially generated in the absence of germinal centers, titers and viral neutralizing activity rapidly waned. T cell depletion in CD28−/− mice with compromised Ab responses, but not in control mice with intact Ab responses, resulted in significant recrudescence from latency, both in the spleen and the lung. Recrudescence could be prevented by passive transfer of immune serum. These data directly demonstrate an important contribution of humoral immunity to control of γ-herpesvirus latency, and have significant implications for clinical intervention.
Trypanosoma cruziInfection Selectively Renders Parasite-Specific IgG+ B Lymphocytes Susceptible to Fas/Fas Ligand-Mediated Fratricide
Authors: Zuñiga Elina , Motran Claudia C. , Montes Carolina L. , Yagita Hideo , Gruppi Adriana
Published: April 2014

The control of B cell expansion has been thought to be solely regulated by T lymphocytes. We show in this study that Trypanosoma cruzi infection induces up-regulation of both Fas and Fas ligand (FasL) molecules on B cells and renders them susceptible to B cell-B cell killing (referred to as fratricide throughout this paper) mediated via Fas/FasL. Moreover, by in vivo administration of anti-FasL blocking mAb we demonstrate that Fas-mediated B cell apoptosis is an ongoing process during this parasitic infection. We also provide evidence that B cells that have switched to IgG isotype are the preferential targets of B cell fratricide. More strikingly, this death pathway selectively affects IgG+ B cells reactive to parasite but not self Ags. Parasite-specific but not self-reactive B cells triggered during this response are rescued after either in vitro or in vivo FasL blockade. Fratricide among parasite-specific IgG+ B lymphocytes could impair the immune control of T. cruzi and possibly other chronic protozoan parasites. Our results raise the possibility that the blockade of Fas/FasL interaction in the B cell compartment of T. cruzi-infected mice may provide a means for enhancing antiparasitic humoral immune response without affecting host tolerance.
Role of NADPH Oxidase in the Mechanism of Lung Neutrophil Sequestration and Microvessel Injury Induced by Gram-Negative Sepsis: Studies in p47phox−/− and gp91phox−/− Mice
Authors: Gao Xiao-pei , Standiford Thedodore J. , Rahman Arshad , Newstead Michael , Holland Steven M. , Dinauer Mary C. , Liu Qing-hui , Malik Asrar B.
Published: April 2014

We addressed the role of O⨪2 generated by the NADPH oxidase complex in the mechanism of polymorphonuclear leukocyte (PMN) accumulation and transalveolar migration and lung microvascular injury. Studies were made in mice lacking the p47phox and gp91phox subunits of NADPH oxidase (p47phox−/− and gp91phox−/−) in which PMN are incapable of the respiratory burst. The mice were challenged i.p. with live Escherichia coli to induce sepsis. We observed time-dependent increases in PMN sequestration and migration from 1 to 6 h after challenge with 2 × 108 E. coli. The responses in knockout mice were greater post-E. coli challenge compared with control mice; i.e., transalveolar PMN migration post-E. coli challenge increased by ∼50% in the null mice above values in wild type. The increased PMN infiltration was associated with decreased lung bacterial clearance. The generation of the chemoattractant macrophage-inflammatory protein-2 in lung tissue was greater in NADPH oxidase-defective mice after E. coli challenge than control mice; moreover, macrophage-inflammatory protein-2 Ab pretreatment prevented the PMN infiltration. We also observed that E. coli failed to increase lung microvascular permeability in p47phox−/− and gp91phox−/− mice despite the greater lung PMN sequestration. Thus, O⨪2 production is required for the induction of sepsis-induced lung microvascular injury. We conclude that NADPH oxidase-derived O⨪2 generation has an important bactericidal role, such that an impairment in bacterial clearance in NADPH oxidase-defective mice results in increased chemokine generation and lung tissue PMN infiltration.
CD8+ T Cells Are Required for Primary Immunity in C57BL/6 Mice Following Low-Dose, Intradermal Challenge withLeishmania major
Authors: Belkaid Yasmine , Von Stebut Esther , Mendez Susana , Lira Rosalia , Caler Elisabet , Bertholet Sylvie , Udey Mark C. , Sacks David
Published: April 2014

Standard murine models of cutaneous leishmaniasis, involving s.c. inoculation of large numbers of Leishmania major promastigotes, have not supported an essential role for CD8+ T cells in the control of primary infection. Recently, a L. major model combining two main features of natural transmission, low parasite dose and inoculation into a dermal site, has been established in resistant C57BL/6 mice. In the present studies, C57BL/6 mice with CD8+ T cell deficiencies, including CD8−/− and CD8-depleted mice, failed to control the growth of L. major following inoculation of 100 metacyclic promastigotes into the ear dermis. The resulting dermal pathology was minor and delayed. Lesion formation in wild-type mice was coincident with the killing of parasites in the inoculation site. Both events were associated with the accumulation of CD8+ T lymphocytes in the skin and with the capacity of CD8+ T cells recovered from draining lymph nodes or infected dermis to release IFN-γ following coculture with infected dendritic cells. Reconstitution of resistance to L. major in RAG−/− mice using T cells from naive donors was optimal when both CD4+ and CD8+ T cells were transferred. Primed CD8+ T lymphocytes obtained from C57BL/6 mice during the acute stage of infection were able to mediate both pathology and immunity when transferred alone. The low dose, intradermal challenge model reveals that CD8+ T cells play an essential role in both pathogenesis of and immunity to primary infection with L. major in the skin.
C/EBPβGene Inactivation Causes Both Impaired and Enhanced Gene Expression and Inverse Regulation of IL-12 p40 and p35 mRNAs in Macrophages
Authors: Gorgoni Barbara , Maritano Diego , Marthyn Paola , Righi Marco , Poli Valeria
Published: April 2014

The transcription factor C/EBPβ is believed to play a fundamental role in regulating activated macrophage functions. However, the molecular mechanisms and the target genes involved have been, so far, poorly characterized, partly due to the difficulty of reproducibly obtaining homogeneous and abundant primary macrophage populations. In this study, we describe the generation and characterization of immortalized macrophage-like cell lines from C/EBPβ-deficient and wild-type mice. Using these cells, we were able to identify a number of genes involved in activated macrophage functions whose induction was affected in the C/EBPβ−/− cells. IFN-γ/LPS-dependent induction of IL-6, IL-1β, TNF-α, inducible NO synthase, and plasminogen activator inhibitor-1 mRNAs was variably impaired, while IL-12 p40, RANTES and macrophage inflammatory protein-1β mRNAs were up-regulated in the absence of C/EBPβ. The differential mRNA expression correlated with differential transcription levels of the corresponding genes, and was in most cases confirmed in primary macrophage populations. Moreover, in sharp contrast to the enhanced induction of IL-12 p40 mRNA, C/EBPβ−/− primary macrophages derived from both the bone marrow and the peritoneal cavity displayed totally defective expression of IL-12 p35 mRNA. Therefore, the IL-12 p35 gene represents a novel obligatory target for C/EBPβ in macrophages and this may explain the defective production of bioactive IL-12 and the impaired Th1 responses of C/EBPβ-deficient mice to Candida albicans infection observed in previous work.
Store-Operated Calcium Entry in Human Neutrophils Reflects Multiple Contributions from Independently Regulated Pathways
Authors: Itagaki Kiyoshi , Kannan K. B. , Livingston David H. , Deitch Edwin A. , Fekete Zoltan , Hauser Carl J.
Published: April 2014

Human polymorphonuclear neutrophil (PMN) responses to G protein-coupled chemoattractants are highly dependent upon store-operated Ca2+ entry (SOCE). Recent research suggests that SOCE currents can be mediated by a variety of related channel proteins of the transient receptor potential superfamily. SOCE has been regarded as a specific response to depletion of cell calcium stores. We hypothesized that net SOCE might reflect the contributions of more than one calcium entry pathway. SOCE was studied in normal human PMN using Ca2+ and Sr2+ ions. We found that PMN SOCE depends on at least two divalent cation influx pathways. One of these was nonspecific and Sr2+ permeable; the other was Ca2+ specific. The two pathways show different degrees of dependence on store depletion by thapsigargin and ionomycin, and differential sensitivity to inhibition by 2-aminoethyoxydiphenyl borane and gadolinium. The inflammatory G protein-coupled chemoattractants fMLP, platelet-activating factor, and IL-8 elicit unique patterns of Sr2+ and Ca2+ influx channel activation, and SOCE responses to these agonists displayed differing degrees of linkage to prior Ca2+ store depletion. The mechanisms of PMN SOCE responses to G protein-coupled chemoattractants are physiologically diverse. They appear to reflect Ca2+ transport through a variety of channels that are independently regulated to varying degrees by store depletion and by G protein-coupled receptor activation.
Regulation of the Mannan-Binding Lectin Pathway of Complement on Neisseria gonorrhoeae by C1-Inhibitor and α2-Macroglobulin
Authors: Gulati Sunita , Sastry Kedarnath , Jensenius Jens C. , Rice Peter A. , Ram Sanjay
Published: April 2014

We examined complement activation by Neisseria gonorrhoeae via the mannan-binding lectin (MBL) pathway in normal human serum. Maximal binding of MBL complexed with MBL-associated serine proteases (MASPs) to N. gonorrhoeae was achieved at a concentration of 0.3 μg/ml. Preopsonization with MBL-MASP at concentrations as low as 0.03 μg/ml resulted in ∼60% killing of otherwise fully serum-resistant gonococci. However, MBL-depleted serum (MBLdS) reconstituted with MBL-MASP before incubation with organisms (postopsonization) failed to kill at a 100-fold higher concentration. Preopsonized organisms showed a 1.5-fold increase in C4, a 2.5-fold increase in C3b, and an ∼25-fold increase in factor Bb binding; enhanced C3b and factor Bb binding was classical pathway dependent. Preopsonization of bacteria with a mixture of pure C1-inhibitor and/or α2-macroglobulin added together with MBL-MASP, all at physiologic concentrations before adding MBLdS, totally reversed killing in 10% reconstituted serum. Reconstitution of MBLdS with supraphysiologic (24 μg/ml) concentrations of MBL-MASP partially overcame the effects of inhibitors (57% killing in 10% reconstituted serum). We also examined the effect of sialylation of gonococcal lipooligosaccharide (LOS) on MBL function. Partial sialylation of LOS did not decrease MBL or C4 binding but did decrease C3b binding by 50% and resulted in 80% survival in 10% serum (lacking bacteria-specific Abs) even when sialylated organisms were preopsonized with MBL. Full sialylation of LOS abolished MBL, C4, and C3b binding, resulting in 100% survival. Our studies indicate that MBL does not participate in complement activation on N. gonorrhoeae in the presence of “complete” serum that contains C1-inhibitor and α2-macroglobulin.
Restricted Localization of the TNF Receptor CD120a to Lipid Rafts: A Novel Role for the Death Domain
Authors: Cottin Vincent , Doan Joyce E. S. , Riches David W. H.
Published: April 2014

The TNF-α receptor, CD120a, has recently been shown to be localized to both plasma membrane lipid rafts and to the trans Golgi complex. Through a combination of both confocal microscopy and sucrose density gradient ultracentrifugation, we show that amino acid sequences located within the death domain (DD) of CD120a are both necessary and sufficient to promote the appropriate localization of the receptor to lipid rafts. Deletion of the DD (CD120a.Δ321-425) prevented the receptor from being targeted to lipid rafts and resulted in a uniform plasma membrane localization. A similar loss of raft localization was also observed following pairwise deletion of the six α-helices that comprise the DD. In all situations, the loss of the ability of CD120a to become localized to lipid rafts following mutagenesis was paralleled by a failure of the receptor to initiate apoptosis. Furthermore, introduction of the lpr mutation into CD120a (CD120a.L351N) also resulted in both a loss in the ability of the receptor to signal apoptosis and to be appropriately localized to rafts. In contrast to CD120a, CD120b, which lacks a DD, is mainly expressed in the bulk plasma membrane and to a lesser extent in lipid rafts, but is absent from the Golgi complex. However, a chimeric receptor in which the DD of CD120a was fused to the cytoplasmic domain of CD120b was predominantly localized to lipid rafts. Collectively, these findings suggest that in addition to its role in CD120a signaling, an appropriately folded and functionally active DD is required for the localization of the receptor to lipid rafts.
IL-9 Inhibits Oxidative Burst and TNF-α Release in Lipopolysaccharide-Stimulated Human Monocytes Through TGF-β
Authors: Pilette Charles , Ouadrhiri Youssef , Van Snick Jacques , Renauld Jean-Christophe , Staquet Philippe , Vaerman Jean-Pierre , Sibille Yves
Published: April 2014

IL-9 is a Th2 cytokine that exerts pleiotropic activities on T cells, B cells, mast cells, hematopoietic progenitors, and lung epithelial cells, but no effect of this cytokine has been reported so far on mononuclear phagocytes. Human blood monocytes preincubated with IL-9 for 24 h before LPS or PMA stimulation exhibited a decreased oxidative burst, even in the presence of IFN-γ. The inhibitory effect of IL-9 was specifically abolished by anti-hIL-9R mAb, and the presence of IL-9 receptors was demonstrated on human blood monocytes by FACS. IL-9 also down-regulated TNF-α and IL-10 release by LPS-stimulated monocytes. In addition, IL-9 strongly up-regulated the production of TGF-β1 by LPS-stimulated monocytes. The suppressive effect of IL-9 on the respiratory burst and TNF-α production in LPS-stimulated monocytes was significantly inhibited by anti-TGF-β1, but not by anti-IL-10Rβ mAb. Furthermore, IL-9 inhibited LPS-induced activation of extracellular signal-regulated kinase 1/2 mitogen-activated protein kinases in monocytes through a TGF-β-mediated induction of protein phosphatase activity. In contrast, IL-4, which exerts a similar inhibitory effect on the oxidative burst and TNF-α release by monocytes, acts primarily through a down-regulation of LPS receptors. Thus, IL-9 deactivates LPS-stimulated blood mononuclear phagocytes, and the mechanism of inhibition involves the potentiation of TGF-β1 production and extracellular signal-regulated kinase inhibition. These findings highlight a new target cell for IL-9 and may account for the beneficial activity of IL-9 in animal models of exaggerated inflammatory response.
IL-16 Regulation of Human Mast Cells/Basophils and Their Susceptibility to HIV-1
Authors: Qi Jian Cheng , Stevens Richard L. , Wadley Robert , Collins Andrew , Cooley Margaret , Naif Hassan M. , Nasr Najla , Cunningham Anthony , Katsoulotos Gregory , Wanigasek Yewlan , Roufogalis Basil , Krilis Steven A.
Published: April 2014

AIDS patients often contain HIV-1-infected mast cells (MCs)/basophils in their peripheral blood, and in vivo-differentiated MCs/basophils have been isolated from the blood of asthma patients that are HIV-1 susceptible ex vivo due to their surface expression of CD4 and varied chemokine receptors. Because IL-16 is a ligand for CD4 and/or an undefined CD4-associated protein, the ability of this multifunctional cytokine to regulate the development of human MCs/basophils from nongranulated progenitors residing in cord or peripheral blood was evaluated. After 3 wk of culture in the presence of c-kit ligand, IL-16 induced the progenitors residing in the blood of normal individuals to increase their expression of chymase and tryptase about 20-fold. As assessed immunohistochemically, >80% of these tryptase+ and/or chymase+ cells expressed CD4. The resulting cells responded to IL-16 in an in vitro chemotaxis assay, and this biologic response could be blocked by anti-IL-16 and anti-CD4 Abs as well as by a competitive peptide inhibitor corresponding to a sequence in the C-terminal domain of IL-16. The additional finding that IL-16 induces calcium mobilization in the HMC-1 cell line indicates that IL-16 acts directly on MCs and their committed progenitors. IL-16-treated MCs/basophils also are less susceptible to infection by an M/R5-tropic strain of HIV-1. Thus, IL-16 regulates MCs/basophils at a number of levels, including their vulnerability to retroviral infection.
Chronic Graft-Versus-Host in Ig Knockin Transgenic Mice Abrogates B Cell Tolerance in Anti-Double-Stranded DNA B Cells
Authors: Sekiguchi Debora R. , Jainandunsing Sandra M. , Fields Michele L. , Maldonado Michael A. , Madaio Michael P. , Erikson Jan , Weigert Martin , Eisenberg Robert A.
Published: April 2014

Anti-dsDNA Abs are specific diagnostic markers of systemic lupus erythematosus, and are also implicated in kidney pathology. Anti-dsDNA B cells have been shown to be tolerized in nonautoimmune mice. The immunodysregulation that causes these cells to break tolerance is presumably part of the fundamental defects in systemic lupus erythematosus. To explore these mechanisms, we used the chronic graft-versus-host model mediated by MHC class II differences. Induction of chronic graft-vs-host in anti-DNA H chain knockin (3H9.KI) transgenic mice on a nonautoimmune background resulted in specific activation of anti-dsDNA B cells, as evidenced by high titers of soluble Ab in sera and a high frequency (70%) of anti-dsDNA B cell clones recovered as hybridomas. In addition, the λ+-anti-dsDNA B cells developed increased expression of cell surface activation markers, and concentrated in the T cell area of the follicle with an Ab-forming cell-compatible phenotype. Genetic analysis of the hybridoma clones showed strong evidence of secondary rearrangements of the L chain associated with anti-dsDNA reactivity. Thus, our study indicates that alloreactive T cell help can break tolerance in a complex manner, involving several events.
De Novo Central Nervous System Processing of Myelin Antigen Is Required for the Initiation of Experimental Autoimmune Encephalomyelitis
Authors: Tompkins Stephen Mark , Padilla Josette , Dal Canto Mauro C. , Ting Jenny P.-Y. , Van Kaer Luc , Miller Stephen D.
Published: April 2014

We demonstrate the absolute requirement for a functioning class II-restricted Ag processing pathway in the CNS for the initiation of experimental autoimmune encephalomyelitis (EAE). C57BL/6 (B6) mice deficient for the class II transactivator, which have defects in MHC class II, invariant chain (Ii), and H-2M (DM) expression, are resistant to initiation of myelin oligodendrocyte protein (MOG) peptide, MOG35–55-specific EAE by both priming and adoptive transfer of encephalitogenic T cells. However, class II transactivator-deficient mice can prime a suboptimal myelin-specific CD4+ Th1 response. Further, B6 mice individually deficient for Ii and DM are also resistant to initiation of both active and adoptive EAE. Although both Ii-deficient and DM-deficient APCs can present MOG peptide to CD4+ T cells, neither is capable of processing and presenting the encephalitogenic peptide of intact MOG protein. This phenotype is not Ag-specific, as DM- and Ii-deficient mice are also resistant to initiation of EAE by proteolipid protein peptide PLP178–191. Remarkably, DM-deficient mice can prime a potent peripheral Th1 response to MOG35–55, comparable to the response seen in wild-type mice, yet maintain resistance to EAE initiation. Most striking is the demonstration that T cells from MOG35–55-primed DM knockout mice can adoptively transfer EAE to wild-type, but not DM-deficient, mice. Together, these data demonstrate that the inability to process antigenic peptide from intact myelin protein results in resistance to EAE and that de novo processing and presentation of myelin Ags in the CNS is absolutely required for the initiation of autoimmune demyelinating disease.
Genetic Analysis of Autoimmune Sialadenitis in Nonobese Diabetic Mice: A Major Susceptibility Region on Chromosome 1
Authors: Boulard Olivier , Fluteau Guy , Eloy Laure , Damotte Diane , Bedossa Pierre , Garchon Henri-Jean
Published: April 2014

The nonobese diabetic (NOD) mouse strain provides a good study model for Sjögren’s syndrome (SS). The genetic control of SS was investigated in this model using different matings, including a (NOD × C57BL/6 (B6))F2 cross, a (NOD × NZW)F2 cross, and ((NOD × B6) × NOD) backcross. Multiple and different loci were detected depending on parent strain combination and sex. Despite significant complexity, two main features were prominent. First, the middle region of chromosome 1 (chr.1) was detected in all crosses. Its effect was most visible in the (NOD × B6)F2 cross and dominated over that of other loci, including those mapping on chr.8, 9, 10, and 16; the effect of these minor loci was observed only in the absence of the NOD haplotype on chr.1. Most critically, the chr.1 region was sufficient to trigger an SS-like inflammatory infiltrate of salivary glands as shown by the study of a new C57BL/6 congenic strain carrying a restricted segment derived from NOD chr.1. Second, several chromosomal regions were previously associated with NOD autoimmune phenotypes, including Iddm (chr.1, 2, 3, 9, and 17, corresponding to Idd5, Idd13, Idd3, Idd2, and Idd1, respectively), accounting for the strong linkage previously reported between insulitis and sialitis, and autoantibody production (chr.10 and 16, corresponding to Bana2 and Bah2, respectively). Interestingly, only two loci were detected in the (NOD × NZW)F2 cross, on chr.1 in females and on chr.7 in males, probably because of the latent autoimmune predisposition of the NZW strain. Altogether these findings reflect the complexity and heterogeneity of human SS.
Two Distinctly HLA-Associated Contiguous Linear Epitopes Uniquely Expressed Within the Islet Antigen 2 Molecule Are Major Autoantibody Epitopes of the Diabetes-Specific Tyrosine Phosphatase-Like Protein Autoantigens
Authors: Bearzatto Massimo , Naserke Heike , Piquer Sandra , Koczwara Kerstin , Lampasona Vito , Williams Alistair , Christie Michael R. , Bingley Polly J. , Ziegler Anette-G. , Bonifacio Ezio
Published: April 2014

The related tyrosine phosphatase-like proteins islet Ag (IA)-2 and IA-2β are autoantigens of type 1 diabetes in humans. Autoantibodies are predominantly against IA-2, and IA-2-specific epitopes are major autoantibody targets. We used the close homology of IA-2 and IA-2β to design chimeras and mutants to identify humoral IA-2-specific epitopes. Two major IA-2 epitopes that are absent from the related autoantigens IA-2β and IA-2Δ 13 splice variant ICA512.bdc were found contiguous to each other within IA-2 juxtamembrane amino acids 611–620 (epitope JM1) and 621–630 (epitope JM2). JM1 and JM2 are recognized by sera from 67% of patients with IA-2 Abs, and relatives of patients with type 1 diabetes having Abs to either JM epitope had a >50% risk for developing type 1 diabetes within 6 years, even in the absence of diabetes-associated HLA genotypes. Remarkably, the presence of Abs to one of these two epitopes was mutually exclusive of the other; JM2 Abs and not JM1 Abs were found in relatives with HLA DR3/4, DR4/13, or DR1/4 genotypes; and the binding of autoantibodies to the JM2 epitope, but not the JM1 epitope, markedly affected proteolysis of IA-2. This is a unique demonstration of HLA-associated B cell responses to epitopes within a single autoantigen in humans and is consistent with modification of Ag processing by specific Ab-influencing peptide presentation by HLA molecules.
Antiphospholipid Antibodies Induce Monocyte Chemoattractant Protein-1 in Endothelial Cells
Authors: Cho Chul-Soo , Cho Mi-La , Chen Pojen P. , Min So-Youn , Hwang Sue-Yun , Park Kyung-Soo , Kim Wan-Uk , Min Do-June , Min Jun-Ki , Park Sung-Hwan , Kim Ho-Youn
Published: April 2014

The presence of antiphospholipid Ab is associated with increased risk of thrombosis. The monocyte-endothelial cell interaction has been suggested to play a key role at the site of vascular injury during thrombosis. Therefore, we tested the effect of anticardiolipin Abs (aCL) on the production of monocyte chemoattractant protein-1 (MCP-1) in HUVEC. We found that monoclonal aCL as well as IgG fractions from patients with antiphospholipid syndrome (APS-IgG) could induce the production of MCP-1 in HUVEC. The ability of IgG aCL to induce MCP-1 production could be abrogated by preabsorption with cardiolipin liposomes. Simultaneous addition of either monoclonal aCL or APS-IgG with IL-1β resulted in synergistic increase in MCP-1 production, whereas the addition of control IgG lacking aCL activity did not alter IL-1β-induced levels of MCP-1. MCP-1 mRNA expression was also up-regulated when HUVEC were incubated with either APS-IgG or monoclonal aCL, and down-regulated by the treatment of dexamethasone. In addition, we found that serum levels of MCP-1 in 76 systemic lupus erythematosus patients correlated well with the titers of IgG aCL. Collectively, these results indicate that aCL could promote endothelial cell-monocyte cross-talk by enhancing the endothelial production of MCP-1, thereby shifting the hemostatic balance toward the prothrombotic state of APS.
Generation of CD4+CD45RA+ Effector T Cells by Stimulation in the Presence of Cyclic Adenosine 5′-Monophosphate- Elevating Agents
Authors: Suárez Ana , Mozo Lourdes , Gutiérrez Carmen
Published: April 2014

After TCR cross-linking, naive CD4+CD45RA+ T cells switch to the expression of the CD45RO isoform and acquire effector functions. In this study we have shown that cAMP-elevating agents added to anti-CD3- and anti-CD28-stimulated cultures of T lymphocytes prevent acquisition of the CD45RO+ phenotype and lead to the generation of a new subpopulation of primed CD4+CD45RA+ effector cells (cAMP-primed CD45RA). These cells displayed a low apoptotic index, as the presence of dibutyryl cAMP (dbcAMP)-rescued cells from CD3/CD28 induced apoptosis. Inhibition of CD45 splicing by dbcAMP was not reverted by addition of exogenous IL-2. cAMP-primed CD45RA cells had a phenotype characteristic of memory/effector T lymphocytes, as they showed an up-regulated expression of CD2, CD44, and CD11a molecules, while the levels of CD62L Ag were down-regulated. These cells also expressed the activation markers CD30, CD71, and HLA class II Ags at an even higher level than CD3/CD28-stimulated cells in the absence of dbcAMP. In agreement with this finding, cAMP-primed CD45RA cells were very efficient in triggering allogenic responses in a MLR. In addition, cAMP-primed CD45RA cells produce considerable amounts of the Th2 cytokines, IL-4, IL-10, and IL-13, whereas the production of IFN-γ and TNF-α was nearly undetectable. The elevated production of IL-13 by neonatal and adult cAMP-primed CD45RA cells was specially noticeable. The cAMP-dependent inhibition of CD45 splicing was not caused by the production of immunosuppressor cytokines. These results suggest that within the pool of CD4+CD45RA+ cells there is a subpopulation of effector lymphocytes generated by activation in the presence of cAMP-elevating agents.
Modulation of Tissue-Specific Immune Response to Cardiac Myosin Can Prolong Survival of Allogeneic Heart Transplants
Authors: Fedoseyeva Eugenia V. , Kishimoto Koji , Rolls Hillary K. , Illigens Ben M.-W. , Dong Victor M. , Valujskikh Anna , Heeger Peter S. , Sayegh Mohamed H. , Benichou Gilles
Published: April 2014

The role of immune response to tissue-specific Ags in transplant rejection is poorly defined. We have previously reported that transplantation of cardiac allografts triggers a CD4+ Th1 cell response to cardiac myosin (CM), a major contractile protein of the heart, and that pretransplant activation of proinflammatory CM-specific T cells accelerates rejection. In this study, we show that administration of CM together with IFA (CM/IFA) can prevent acute rejection of an allogeneic heart transplant. Prolongation of cardiac graft survival is associated with activation of CM- and allo-specific T cells secreting type 2 cytokines (IL-4, IL-5) and reduction of the frequency of proinflammatory IFN-γ-secreting (type 1) alloreactive T cells. Blocking of IL-4 cytokine with Abs abrogates the prolongation. CM/IFA treatment prevents acute rejection of MHC class I-mismatched, but not fully mismatched grafts. However, if donor heart is devoid of MHC class II expression, CM-IFA administration delays rejection of fully allogeneic cardiac transplants. This finding suggests that the effect of CM modulation depends on the type (direct vs indirect) and strength of recipient’s CD4+ T cell alloresponse. Our results underscore the important role of host immunity to tissue-specific Ags in the rejection of an allograft. This study demonstrates that modulation of the immune response to a tissue-specific Ag can significantly prolong cardiac allograft survival, an observation that may have important implications for the development of novel selective immune therapies in transplantation.
Cross-Reactive Antigen Is Required to Prevent Erosion of Established T Cell Memory and Tumor Immunity: A Heterologous Bacterial Model of Attrition
Authors: Smith Dean K. , Dudani Renu , Pedras-Vasconcelos Joao A. , Chapdelaine Yvan , van Faassen Henk , Sad Subash
Published: April 2014

Induction and maintenance of T cell memory is critical for the control of intracellular pathogens and tumors. Memory T cells seem to require few “maintenance signals,” though often such studies are done in the absence of competing immune challenges. Conversely, although attrition of CD8+ T cell memory has been characterized in heterologous viral models, this is not the case for bacterial infections. In this study, we demonstrate attrition of T cell responses to the intracellular pathogen Listeria monocytogenes (LM) following an immune challenge with a second intracellular bacterium, Mycobacterium bovis (bacillus Calmette-Guérin, BCG). Mice immunized with either LM or recombinant LM (expressing OVA; LM-OVA), develop a potent T cell memory response. This is reflected by peptide-specific CTL, IFN-γ production, and frequency of IFN-γ-secreting T cells to native or recombinant LM Ags. However, when the LM-infected mice are subsequently challenged with BCG, there is a marked reduction in the LM-specific T cell responses. These reductions are directly attributable to the effects on CD4+ and CD8+ T cells and the data are consistent with a loss of LM-specific T cells, not anergy. Attrition of the Ag (OVA)-specific T cell response is prevented when LM-OVA-immunized mice are challenged with a subsequent heterologous pathogen (BCG) expressing OVA, demonstrating memory T cell dependence on Ag. Although the reduction of the LM-specific T cell response did not impair protection against a subsequent LM rechallenge, for the first time, we show that T cell attrition can result in the reduction of Ag-specific antitumor (B16-OVA) immunity previously established with LM-OVA immunization.
Suppressor of Cytokine Signaling-3 Is Recruited to the Activated Granulocyte-Colony Stimulating Factor Receptor and Modulates its Signal Transduction
Authors: Hörtner Michael , Nielsch Ulrich , Mayr Lorenz M. , Johnston James A. , Heinrich Peter C. , Haan Serge
Published: April 2014

G-CSF is a polypeptide growth factor used in treatment following chemotherapy. G-CSF regulates granulopoiesis and acts on its target cells by inducing homodimerization of the G-CSFR, thereby activating intracellular signaling cascades. The G-CSFR encompasses four tyrosine motifs on its cytoplasmic tail that have been shown to recruit a number of regulatory proteins. Suppressor of cytokine signaling 3 (SOCS-3), also referred to as cytokine-inducible Src homolgy 2-containing protein 3, is a member of a recently discovered family of feedback inhibitors that have been shown to inhibit the Janus kinase/STAT pathway. In this study, we demonstrate that human SOCS-3 is rapidly induced by G-CSF in polymorphonuclear neutrophils as well as in the myeloid precursor cell line U937 and that SOCS-3 negatively regulates G-CSFR-mediated STAT activation. Most importantly, we show that SOCS-3 is recruited to the G-CSFR in a phosphorylation-dependent manner and we identify phosphotyrosine (pY)729 as the major recruitment site for SOCS-3. Furthermore, we demonstrate that SOCS-3 directly binds to this pY motif. Surface plasmon resonance analysis reveals a dissociation constant (KD) for this interaction of around 2.8 μM. These findings strongly suggest that the recruitment of SOCS-3 to pY729 is important for the modulation of G-CSFR-mediated signal transduction by SOCS-3.
Dendritic Cell Immunogenicity Is Regulated by Peroxisome Proliferator-Activated Receptor γ
Authors: Nencioni Alessio , Grünebach Frank , Zobywlaski Anke , Denzlinger Claudio , Brugger Wolfram , Brossart Peter
Published: April 2014

Dendritic cells (DC) are the most potent APCs known that play a key role for the initiation of immune responses. Ag presentation to T lymphocytes is likely a constitutive function of DC that continues during the steady state. This raises the question of which mechanism(s) determines whether the final outcome of Ag presentation will be induction of immunity or of tolerance. In this regard, the mechanisms controlling DC immunogenicity still remain largely uncharacterized. In this paper we report that the nuclear receptor peroxisome proliferator-activated receptor γ (PPAR-γ), which has anti-inflammatory properties, redirects DC toward a less stimulatory mode. We show that activation of PPAR-γ during DC differentiation profoundly affects the expression of costimulatory molecules and of the DC hallmarker CD1a. PPAR-γ activation in DC resulted in a reduced capacity to activate lymphocyte proliferation and to prime Ag-specific CTL responses. This effect might depend on the decreased expression of costimulatory molecules and on the impaired cytokine secretion, but not on increased IL-10 production, because this was reduced by PPAR-γ activators. Moreover, activation of PPAR-γ in DC inhibited the expression of EBI1 ligand chemokine and CCR7, both playing a pivotal role for DC migration to the lymph nodes. These effects were accompanied by down-regulation of LPS-induced nuclear localized RelB protein, which was shown to be important for DC differentiation and function. Our results suggest a novel regulatory pathway for DC function that could contribute to the regulated balance between immunity induction and self-tolerance maintenance.
T Cell Antigen Receptor Engagement and Specificity in the Recognition of Stress-Inducible MHC Class I-Related Chains by Human Epithelial γδ T Cells
Authors: Wu Jennifer , Groh Veronika , Spies Thomas
Published: April 2014

Human γδ T cells with the TCR variable region Vδ1 occur mainly in epithelia and respond to stress-induced expression of the MHC class I-related chains A and B, which have no function in Ag presentation. MIC function as ligands for NKG2D-DAP10, an activating receptor complex that triggers NK cells, costimulates CD8 αβ and Vγ9Vδ2 γδ T cells, and is required for stimulation of Vδ1 γδ T cells. It is unresolved, however, whether triggering of Vδ1 γδ TCRs is also mediated by MIC or by unidentified cell surface components. Soluble MICA tetramers were used as a binding reagent to demonstrate specific interactions with various Vδ1 γδ TCRs expressed on transfectants of a T cell line selected for lack of NKG2D. Tetramer binding was restricted to TCRs derived from responder T cell clones classified as reactive against a broad range of MIC-expressing target cells and was abrogated when TCRs were composed of mismatched γ- and δ-chains. These results and the inability of Vδ1 γδ T cells to respond to target cells expressing the ULBP/N2DL ligands of NKG2D, which are highly divergent from MIC, indicate that MIC delivers both the TCR-dependent signal 1 and the NKG2D-dependent costimulatory signal 2. This dual function may serve to prevent erroneous γδ T cell activation by cross-reactive cell surface determinants.
T Cell Proliferation Induced by Autologous Non-T Cells Is a Response to Apoptotic Cells Processed by Dendritic Cells
Authors: Chernysheva Anna D. , Kirou Kyriakos A. , Crow Mary K.
Published: April 2014

Self-reactive T cells are present in the mature immune repertoire as demonstrated by T cell proliferation induced by autologous non-T cells in the autologous mixed lymphocyte reaction. This reaction generates regulatory T cells in vitro and may reflect immune regulatory pathways in vivo, but the antigenic peptides recognized remain uncharacterized. We revisited this issue in light of the importance of apoptosis in immune regulation. We found that apoptosis among peripheral blood non-T stimulator cells is associated with augmented induction of autologous T cell proliferation. Our data show that caspase activity in the non-T stimulator population is essential for induction of autologous T cell proliferation, suggesting that cellular components in the non-T cell fraction are enzymatically modified, most likely by effector caspases, and have a direct or indirect effect on autoreactive T cell activation. Furthermore, exposure of macrophage-derived dendritic cells to apoptotic non-T cells augments autologous T cell proliferation, and blockade of αvβ5 integrin, but not αvβ3, inhibits the capacity of irradiated non-T cells or dendritic cells to stimulate autologous T cell proliferation. These experiments, using an entirely autologous system, suggest the interpretation that autoreactive T cells may recognize self-Ags modified through the actions of caspases and presented to T cells by dendritic cells. Induction of an in vivo autologous mixed lymphocyte reaction by caspase-modified self-Ags present in apoptotic cells may represent a mechanism to maintain peripheral immune tolerance.
The CD154-CD40 T Cell Costimulation Pathway Is Required for Host Sensitization of CD8+ T Cells by Skin Grafts Via Direct Antigen Presentation
Authors: Zhai Yuan , Shen Xiu-Da , Gao Feng , Coito Ana J. , Wasowska Barbara A. , Salama Alan , Schmitt Isabela , Busuttil Ronald W. , Sayegh Mohamed H. , Kupiec-Weglinski Jerzy W.
Published: April 2014

Although the CD154-CD40 T cell costimulation pathway has been shown to mediate alloimmune responses in normal recipients, little is known about its role in sensitized hosts. In this work, by using novel models of cardiac allograft rejection in skin-sensitized CD154- and CD40-deficient mice, we reaffirm the key role of CD154-CD40 signaling in host sensitization to alloantigen in vivo. First, we identified CD8+ T cells as principal effectors in executing accelerated rejection in our model. Disruption of CD154-CD40 signaling in recipients at the T cell side (CD154-deficient) but not at the APC side (CD40-deficient) abrogated accelerated (<2 days) rejection and resulted in long-term (>100 days) graft survival. This suggests that the CD154-dependent mechanism in host CD8+ T cell sensitization operates via the direct Ag presentation. Then, in comparative studies of alloimmune responses in CD154-deficient and wild-type recipients, we showed that, although alloreactive B cell responses were inhibited, alloreactive T cell responses were down-regulated selectively in the CD8+ T cell compartment, leaving CD4+ T cells largely unaffected. This unique alteration in host alloreactivity, seen not only in peripheral lymphocytes but also in allograft infiltrate, may represent the key mechanism by which disruption of CD154-CD40 signaling prevents sensitization to alloantigen in vivo and leads to long-term allograft survival.
Chemotactic Responsiveness Toward Ligands for CXCR3 and CXCR4 Is Regulated on Plasma Blasts During the Time Course of a Memory Immune Response
Authors: Hauser Anja E. , Debes Gudrun F. , Arce Sergio , Cassese Giuliana , Hamann Alf , Radbruch Andreas , Manz Rudolf A.
Published: April 2014

Plasma blasts formed during memory immune responses emigrate from the spleen to migrate into the bone marrow and into chronically inflamed tissues where they differentiate into long-lived plasma cells. In this study, we analyze the chemokine responsiveness of plasma blasts formed after secondary immunization with OVA. Starting from day 4 and within ∼48 h, OVA-specific plasma blasts emigrate from spleen and appear in the bone marrow. Although these migratory cells have lost their responsiveness to many B cell attracting chemokines, e.g., CXC chemokine ligand (CXCL)13 (B lymphocyte chemoattractant), they migrate toward CXCL12 (stromal cell-derived factor 1α), and toward the inflammatory chemokines CXCL9 (monokine induced by IFN-γ), CXCL10 (IFN-γ-inducible protein 10), and CXCL11 (IFN-inducible T cell α chemoattractant). However, the responsiveness of plasma blasts to these chemokines is restricted to a few days after their emigration from the spleen, indicating a role for these molecules and their cognate receptors, i.e., CXCR3 and CXCR4, in the regulation of plasma blast migration into the bone marrow and/or inflamed tissues.
Level of B Cell Antigen Receptor Surface Expression Influences Both Positive and Negative Selection of B Cells During Primary Development
Authors: Heltemes Lynn M. , Manser Tim
Published: April 2014

To examine the effect of B cell Ag receptor (BCR) surface density on B cell development, we studied multiple lines of mice containing various copy numbers of an IgHμδ transgene. The VH gene in this transgene encodes multireactive BCRs with low affinity for self Ags. These BCRs promote differentiation to a B cell subpopulation that shares some, but not all of the properties of marginal zone (MZ) B cells. Surface BCR level was found to be related to transgene gene copy number in these mice. In mice containing 1–15 copies of the transgene, elevated surface BCR levels were correlated with increased numbers of B cells in the MZ-like subset. However, in mice containing 20–30 copies of the transgene, massive clonal deletion of B cells was observed in the bone marrow, few B cells populated the spleen, and B cells were essentially absent from the lymph nodes. These data support the idea that autoantigens mediate not only negative, but positive selection of developing B cells as well. More importantly, they illustrate the profound influence of BCR surface density on the extent to which either of these selective processes take place.
Infection of APC by Human Cytomegalovirus Controlled Through Recognition of Endogenous Nuclear Immediate Early Protein 1 by Specific CD4+ T Lymphocytes
Authors: Le Roy Emmanuelle , Baron Michel , Faigle Wolfgang , Clément Danièle , Lewinsohn David M. , Streblow Daniel N. , Nelson Jay A. , Amigorena Sebastian , Davignon Jean-Luc
Published: April 2014

Infections by human CMV are controlled by cellular immune responses. Professional APC such as monocytes and macrophages can be infected in vivo and are considered as a reservoir of virus. However, CMV-specific CD4+ responses against infected APC have not been reported. To develop a model of CD4-infected APC interaction, we have transfected the U373MG astrocytoma cell line with the class II transactivator (CIITA). Confocal microscopy experiments showed that U373MG-CIITA cells expressed markers characteristic of APC. Functional assays demonstrated that infected U373MG-CIITA APC processed and presented both exogenous and endogenously neosynthesized nuclear immediate early (IE) protein 1 through the MHC class II pathway. More importantly, endogenous presentation of IE1 by infected APC lead to efficient control of CMV infection as revealed by decreased viral titer. Thus, these results describe the endogenous presentation of a nuclear viral protein by the MHC class II pathway and suggest that IE1-specific CD4+ T cells may play an important role in CMV infection by directly acting against infected APC.
A Role for NF-κB Activation in Perforin Expression of NK Cells Upon IL-2 Receptor Signaling
Authors: Zhou Jun , Zhang Jin , Lichtenheld Mathias G. , Meadows Gary G.
Published: April 2014

Optimal NK cell development and activation as well as cytolytic activity involves IL-2Rβ signals that also up-regulate expression of the pore-forming effector molecule perforin. Although the Jak/Stat pathway and specifically Stat5 transcription factors are required to promote many of the respective downstream events, the role of additional signaling pathways and transcription factors remains to be clarified. This report investigates the role of NF-κB activation for perforin expression by NK cells. It is demonstrated that IL-2-induced up-regulation of perforin in primary NK cells and in a model cell line is blocked by two pharmacological agents known to inhibit NF-κB activation. Direct evidence for the activation of the NF-κB pathway by IL-2R signals in NK cells involves activation of the IKKα kinase, inhibitory protein κBα degradation, nuclear translocation of p50/p65 complexes, and ultimately, transcriptional activation of the perforin gene via an NF-κB binding element in its upstream enhancer. Taken together, these observations strongly suggest that IL-2R signals can activate a pathway leading to NF-κB activation in NK cells and that this pathway is involved in the control of perforin expression.