bluuebunny/crossref_metadata_2025 huggingface dataset:
Injury Primes the Innate Immune System for Enhanced Toll-Like Receptor Reactivity
Authors: Paterson Hugh M. , Murphy Thomas J. , Purcell Elizabeth J. , Shelley Odhran , Kriynovich Sara J. , Lien Egil , Mannick John A. , Lederer James A.
Published: April 2014

Severe injury causes a dramatic host response that disrupts immune homeostasis and predisposes the injured host to opportunistic infections. Because Toll-like receptors (TLRs) recognize conserved microbial Ags and endogenous danger signals that may be triggered by injury, we wanted to determine how injury influences TLR responses. Using an in vivo injury model, we demonstrate that injury significantly increased TLR2- and TLR4-induced IL-1β, IL-6, and TNF-α production by spleen cells. This influence of injury on TLR reactivity was observed as early as 1 day after injury and persisted for at least 7 days. The outcome of similar studies performed using TLR4-mutant C57BL/10ScN/Cr mice revealed that TLR2 responses remained primed, thus suggesting that injury-induced priming can occur independently of endogenous TLR4 signaling. Increased TLR4 reactivity was also observed in vivo, because LPS-challenged injured mice demonstrated significantly higher cytokine expression levels in the lung, liver, spleen, and plasma. Macrophages and dendritic cells were the major source of these cytokines as judged by intracellular cytokine staining. Moreover, ex vivo studies using enriched macrophage and dendritic cell populations confirmed that T cells did not contribute to the enhanced TLR2 and TLR4 responses. The results of flow cytometry studies using TLR2- and TLR4-MD-2-specific Abs indicated that injury did not markedly alter cell surface TLR2 or TLR4-MD-2 expression. Taken together, these findings establish that injury primes the innate immune system for enhanced TLR2- and TLR4-mediated responses and provides evidence to suggest that augmented TLR reactivity might contribute to the development of heightened systemic inflammation following severe injury.
NF-κB Is Required Within the Innate Immune System to Inhibit Microflora-Induced Colitis and Expression of IL-12 p40
Authors: Tomczak Michal F. , Erdman Susan E. , Poutahidis Theofilos , Rogers Arlin B. , Holcombe Hilda , Plank Benjamin , Fox James G. , Horwitz Bruce H.
Published: April 2014

We have previously presented evidence demonstrating that mice deficient in NF-κB subunits are susceptible to colitis induced by the pathogenic enterohepatic Helicobacter species, H. hepaticus. However, it has not been determined whether NF-κB is required within inhibitory lymphocyte populations, within cells of the innate immune system, or both, to suppress inflammation. To examine these issues, we have performed a series of adoptive transfer experiments using recombination-activating gene (Rag)-2−/− or p50−/−p65+/−Rag-2−/− mice as hosts for wild-type (WT) and p50−/−p65+/− lymphocyte populations. We have shown that although the ability of H. hepaticus to induce colitis in Rag-2−/− mice is inhibited by the presence of either WT or p50−/−p65+/− splenocytes, these splenocyte populations are unable to suppress H. hepaticus-induced colitis in p50−/−p65+/−Rag-2−/− mice. Colitis in these animals is characterized by increased expression of inflammatory cytokines including IL-12 p40, and depletion of IL-12 p40 from p50−/−p65+/− mice ameliorates H. hepaticus-induced disease. Consistent with a primary defect in the regulation of IL-12 expression, H. hepaticus induced markedly higher levels of IL-12 p40 in p50−/−p65+/− macrophages than in WT macrophages. These results suggest that inhibition of H. hepaticus-induced IL-12 p40 expression by NF-κB subunits is critical to preventing colonic inflammation in response to inflammatory microflora.
Mucosal T Cells Expressing High Levels of IL-7 Receptor Are Potential Targets for Treatment of Chronic Colitis
Authors: Yamazaki Motomi , Yajima Tomoharu , Tanabe Masanobu , Fukui Kazuto , Okada Eriko , Okamoto Ryuichi , Oshima Shigeru , Nakamura Tetsuya , Kanai Takanori , Uehira Masahiro , Takeuchi Tsutomu , Ishikawa Hiromichi , Hibi Toshifumi , Watanabe Mamoru
Published: April 2014

The IL-7/IL-7R-dependent signaling pathway plays a crucial role in regulating the immune response in intestinal mucosa. Here we demonstrate the pivotal role of this pathway in the development and treatment of chronic colitis. T cells expressing high levels of IL-7R were substantially infiltrated in the chronic inflamed mucosa of TCR α-chain knockout mice and IL-7 transgenic mice. Transfer of mucosal T cells expressing high levels of IL-7R, but not T cells expressing low levels of IL-7R, from these mice into recombinase-activating gene-2−/− mice induced chronic colitis. Selective elimination of T cells expressing high levels of IL-7R by administrating small amounts of toxin-conjugated anti-IL-7R Ab completely ameliorated established, ongoing colitis. These findings provide evidence that therapeutic approaches targeting mucosal T cells expressing high levels of IL-7R are effective in the treatment of chronic intestinal inflammation and may be feasible for use in the therapy of human inflammatory bowel disease.
Systemic Rather Than Local Heme Oxygenase-1 Overexpression Improves Cardiac Allograft Outcomes in a New Transgenic Mouse
Authors: Araujo Jesus A. , Meng Lingzhong , Tward Aaron D. , Hancock Wayne W. , Zhai Yuan , Lee Annie , Ishikawa Kazunobu , Iyer Suhasini , Buelow Roland , Busuttil Ronald W. , Shih Diana M. , Lusis Aldons J. , Kupiec-Weglinski Jerzy W.
Published: April 2014

Heme oxygenase-1 (HO-1), a rate-limiting enzyme in heme catabolism, exhibits potent antioxidant and anti-inflammatory properties. We developed HO-1 transgenic (Tg) mice using a rat HO-1 genomic transgene under the control of the endogenous promoter. Transgene expression was demonstrated by RT-PCR in all studied tissues, and a modest HO-1 overexpression was documented by Western, ELISA, and enzyme activity assays. To assess the effect of local vs systemic HO-1 in the acute rejection response, we used Tg mice as organ donors or recipients of MHC-incompatible heart grafts. In the local HO-1 overexpression model, Tg allografts survived 10.5 ± 0.7 days (n = 10), compared with 6.5 ± 0.4 days (n = 6) for wild-type donor controls (p = 0.0001). In the systemic HO-1 overexpression model, Tg recipients maintained allografts for 26.8 ± 3.4 days (n = 10), compared with 6.3 ± 0.1 days (n = 12) in wild-type controls (p = 0.00009). Inhibition of HO activity by treatment with tin protoporphyrin blunted survival advantage in Tg mice and resulted in acute graft rejection (n = 3). Increased carboxyhemoglobin levels were consistently noted in Tg mice. Comparisons of grafts at day 4 indicated that HO-1 overexpression was inversely associated with vasculitis/inflammatory cell infiltrate in both models. Hearts transplanted into Tg recipients showed decreased CD4+ lymphocyte infiltration and diminished immune activation, as judged by CD25 expression. Thus, although local and systemic HO-1 overexpression improved allograft outcomes, systemic HO-1 led to a more robust protection and resulted in a significant blunting of host immune activation. This Tg mouse provides a valuable tool to study mechanisms by which HO-1 exerts beneficial effects in organ transplantation.
Selective Targeting of Melanoma and APCs Using a Recombinant Antibody with TCR-Like Specificity Directed Toward a Melanoma Differentiation Antigen
Authors: Denkberg Galit , Lev Avital , Eisenbach Lea , Benhar Itai , Reiter Yoram
Published: April 2014

Tumor-associated, MHC-restricted peptides, recognized by tumor-specific CD8+ lymphocytes, are desirable targets for novel approaches in immunotherapy because of their highly restricted fine specificity. Abs that recognize these tumor-associated MHC-peptide complexes, with the same specificity as TCR, would therefore be valuable reagents for studying Ag presentation by tumor cells, for visualizing MHC-peptide complexes on cells, and eventually for developing new targeting agents for cancer immunotherapy. To generate molecules with such a unique, fine specificity, we immunized HLA-A2 transgenic mice with a single-chain HLA-A2, complexed with a common antigenic T cell HLA-A2-restricted epitope derived from the melanoma differentiation Ag gp100. Using a phage display approach, we isolated a recombinant scFv Ab that exhibits a characteristic TCR-like binding specificity, yet, unlike TCRs, it did so with a high affinity in the nanomolar range. The TCR-like Ab can recognize the native MHC-peptide complex expressed on the surface of APCs, and on peptide-pulsed or native melanoma cells. Moreover, when fused to a very potent cytotoxic effector molecule in the form of a truncated bacterial toxin, it was able to specifically kill APCs in a peptide-dependent manner. These results demonstrate the utility of high affinity TRC-like scFv recombinant Abs directed toward human cancer T cell epitopes. Such TCR-like Abs may prove to be very useful for monitoring and visualizing the expression of specific MHC-peptide complexes on the surface of tumor cells, APCs, and lymphoid tissues, as well as for developing a new family of targeting agents for immunotherapy.
CD28 Engagement Promotes Actin Polymerization Through the Activation of the Small Rho GTPase Cdc42 in Human T Cells
Authors: Salazar-Fontana Laura Inés , Barr Valarie , Samelson Lawrence E. , Bierer Barbara E.
Published: April 2014

Engagement of the costimulatory molecule CD28 is an important step in the optimal activation of T cells. Nevertheless, the specific role of CD28 in the formation of the immunological synapse and cytoskeletal changes that occur upon TCR/CD3 complex engagement is still poorly understood. Using Ab-coated surfaces, we show that CD28 engagement in the absence of any other signal induced the formation of cytoplasmic elongations enriched in filamentous actin (F-actin), in this work called filopodia or microspikes. Such structures were specific for engagement of CD28 on mAb-coated surfaces because they could not be observed in surfaces coated with either poly(l-lysine) or anti-CD3 mAb. The signaling pathway coupling CD28 to cytoskeletal rearrangements required Src-related kinase activity and promoted Vav phosphorylation and Cdc42 activation independently of the ζ-chain-associated kinase (ZAP-70). CD28-induced filopodia required Cdc42 GTPase activity, but not the related Rho GTPase Rac1. Moreover, Cdc42 colocalized to areas of increased F-actin. Our results support a specific role for the activation of the small Rho GTPase Cdc42 in the actin reorganization mediated by CD28 in human T cells.
Human Chorionic Gonadotropin Contributes to Maternal Immunotolerance and Endometrial Apoptosis by Regulating Fas-Fas Ligand System
Authors: Kayisli Umit A. , Selam Belgin , Guzeloglu-Kayisli Ozlem , Demir Ramazan , Arici Aydin
Published: April 2014

The first known hormonal signal of the conceptus during implantation is human chorionic gonadotropin (hCG). Interestingly, increased apoptosis in human endometrium coincides with the implantation window. Factors from the fetal or placental origin as well as maternal hormonal factors are likely to have a potential role in the regulation of apoptotic signaling molecules. We hypothesized that hCG may be a placental link for the development of local maternal immunotolerance. Fas-Fas ligand (FasL) system is one of the apoptotic signaling pathways, shown to be important in the development of local immune tolerance during and after implantation. We report that hCG treatment decreases cell proliferation and increases apoptosis in endometrial cells. Moreover, hCG stimulates FasL mRNA and protein expression without affecting Fas mRNA in these cells. Interestingly, in coculture experiments, hCG-treated endometrial cells induce an increase in T cell apoptosis. Our in vivo results reveal that cells of early pregnancy decidua express strong FasL immunoreactivity, and decidual areas containing interstitial cytotrophoblasts have numerous TUNEL-positive cells. Compared with decidual areas devoid of interstitial cytotrophoblasts, we observed in decidual areas containing interstitial cytotrophoblasts clearly less amount of TUNEL-positive cells. These results suggest that hCG may be a link in the development of peritrophoblastic immune tolerance and may facilitate the trophoblast invasion by regulating proapoptotic molecules such as FasL in endometrial cells.
The Decline in B Lymphopoiesis in Aged Mice Reflects Loss of Very Early B-Lineage Precursors
Authors: Miller Juli P. , Allman David
Published: April 2014

The primary age-related loss in B cell progenitors is thought to be at the pro- to pre-B cell transition. However, we show that the frequencies and absolute numbers of all progenitor populations for the B cell lineage, including B-lineage-committed pro-B cells and multipotent B-lymphoid progenitors, decline in aged C57BL/6 mice. Moreover, when derived from aged mice, lymphoid progenitors within every population examined exhibited suboptimal IL-7 responsiveness, demonstrating that age-associated suboptimal IL-7R signaling is a general property of all early B-lineage precursors. Collectively, these data indicate that aging results in a previously unappreciated decline in the earliest stages of B cell development.
Analysis of H2-O Influence on Antigen Presentation by B Cells
Authors: Alfonso Christopher , Williams G. Stuart , Han Jung-Ok , Westberg Johan A. , Winqvist Ola , Karlsson Lars
Published: April 2014

HLA-DM (DM; in mouse H2-DM) promotes the exchange of MHC class II-associated peptides, resulting in the accumulation of stable MHC class II-peptide complexes. In naive (but not germinal center) B cells, a large part of DM is tightly associated with HLA-DO (DO; in mouse H2-O), but the functional consequence of this association for Ag presentation is debated. Here, we have extended previous studies by examining the presentation of multiple epitopes after Ag internalization by fluid phase endocytosis or receptor-mediated uptake by membrane Ig (mIg) receptors. We find that the effects of H2-O are more complex than previously appreciated; thus, while only minor influences on Ag presentation could be detected after fluid phase uptake, many epitopes were substantially affected after mIg-mediated uptake. Unexpectedly, the presentation of different epitopes was found to be enhanced, diminished, or unaffected in the absence of H2-O, depending on the specificity of the mIg used for Ag internalization. Interestingly, epitopes from the same Ag did not necessarily show the same H2-O dependency. This finding suggests that H2-O may control the repertoire of peptides presented by B cells depending on the mIg-Ag interaction. The absence of DO/H2-O from germinal center B cells suggests that this control may be released during B cell maturation.
Two Distinct Mechanisms For Induction of Dendritic Cell Apoptosis in Response to IntactStreptococcus pneumoniae
Authors: Colino Jesus , Snapper Clifford M.
Published: April 2014

Apoptotic dendritic cells (DCs) are ineffective at inducing immunity. Thus, parameters that regulate DC viability during a primary infection will help to determine the outcome of the subsequent immune response. In this regard, pathogens have developed strategies to promote DC apoptosis to counterbalance the nascent primary immune response. We demonstrate, using cultured bone marrow-derived DCs, that Streptococcus pneumoniae can induce DC apoptosis through two distinct mechanisms: 1) a rapid, caspase-independent mechanism of apoptosis induction, critically dependent on bacterial expression of pneumolysin, and 2) a delayed-onset, caspase-dependent mechanism of apoptosis induction associated with terminal DC maturation. Delayed-onset apoptosis does not require bacterial internalization, but rather is triggered by the interaction of bacterial subcapsular components and bone marrow-derived DC (likely Toll-like) receptors acting in a myeloid differentiation factor 88-dependent manner. In this regard, heavy polysaccharide encapsulation interferes with both DC maturation and apoptosis induction. In contrast, neither CD95/CD95 ligand interactions nor TNF-α appear to play a role in the delayed onset of apoptosis. These data are the first to define two mechanistically distinct pathways of DC apoptosis induction in response to an extracellular bacterium that likely have important consequences for the establishment of antibacterial immunity.
Dendritic Cells Mediate NK Cell Help for Th1 and CTL Responses: Two-Signal Requirement for the Induction of NK Cell Helper Function
Authors: Mailliard Robbie B. , Son Young-Ik , Redlinger Richard , Coates Patrick T. , Giermasz Adam , Morel Penelope A. , Storkus Walter J. , Kalinski Pawel
Published: April 2014

Early stages of viral infections are associated with local recruitment and activation of dendritic cells (DC) and NK cells. Although activated DC and NK cells are known to support each other’s functions, it is less clear whether their local interaction in infected tissues can modulate the subsequent ability of migrating DC to induce T cell responses in draining lymph nodes. In this study, we report that NK cells are capable of inducing stable type 1-polarized “effector/memory” DC (DC1) that act as carriers of NK cell-derived helper signals for the development of type 1 immune responses. NK cell-induced DC1 show a strongly elevated ability to produce IL-12p70 after subsequent CD40 ligand stimulation. NK-induced DC1 prime naive CD4+ Th cells for high levels of IFN-γ, but low IL-4 production, and demonstrate a strongly enhanced ability to induce Ag-specific CD8+ T cell responses. Resting NK cells display stringent activation requirements to perform this novel, DC-mediated, “helper” function. Although their interaction with K562 cells results in effective target cell killing, the induction of DC1 requires a second NK cell-activating signal. Such costimulatory signal can be provided by type I IFNs, common mediators of antiviral responses. Therefore, in addition to their cytolytic function, NK cells also have immunoregulatory activity, induced under more stringent conditions. The currently demonstrated helper activity of NK cells may support the development of Th1- and CTL-dominated type 1 immunity against intracellular pathogens and may have implications for cancer immunotherapy.
B220+ Double-Negative T Cells Suppress Polyclonal T Cell Activation by a Fas-Independent Mechanism That Involves Inhibition of IL-2 Production
Authors: Hamad Abdel Rahim A. , Mohamood Abdiaziz S. , Trujillo Crystal J. , Huang Ching-Tai , Yuan Emily , Schneck Jonathan P.
Published: April 2014

Fas-mediated apoptosis is a key mechanism for elimination of autoreactive T cells, yet loss of function mutations in the Fas signaling pathway does not result in overt T cell-mediated autoimmunity. Furthermore, mice and humans with homozygous Faslpr or Fas ligandgld mutations develop significant numbers of B220+ CD4− CD8− double-negative (DN) αβ T cells (hereafter referred to as B220+ DN T cells) of poorly understood function. In this study, we show that B220+ DN T cells, whether generated in vitro or isolated from mutant mice, can suppress the ability of activated T cells to proliferate or produce IL-2, IL-10, and IFN-γ. B220+ DN T cells that were isolated from either lpr or gld mice were able to suppress proliferation of autologous and syngeneic CD4 T cells, showing that suppression is Fas independent. Furthermore, restoration of Fas/Fas ligand interaction did not enhance suppression. The mechanism of suppression involves inhibition of IL-2 production and its high affinity IL-2R α-chain (CD25). Suppression also requires cell/cell contact and TCR activation of B220+ DN T cells, but not soluble cytokines. These findings suggest that B220+ DN T cells may be involved in controlling autoreactive T cells in the absence of Fas-mediated peripheral tolerance.
Suppressor of Cytokine Signaling 1 Regulates IL-15 Receptor Signaling in CD8+CD44high Memory T Lymphocytes
Authors: Ilangumaran Subburaj , Ramanathan Sheela , La Rose Jose , Poussier Philippe , Rottapel Robert
Published: April 2014

T lymphocyte survival, proliferation, and death in the periphery are dependent on several cytokines. Many of these cytokines induce the expression of suppressor of cytokine signaling-1 (SOCS1), a feedback inhibitor of JAK kinases. However, it is unclear whether the cytokines that regulate T lymphocyte homeostasis are critically regulated by SOCS1 in vivo. Using SOCS1−/−IFN-γ−/− mice we show that SOCS1 deficiency causes a lymphoproliferative disorder characterized by decreased CD4/CD8 ratio due to chronic accumulation of CD8+CD44high memory phenotype T cells. SOCS1-deficient CD8+ T cells express elevated levels of IL-2Rβ, show increased proliferative response to IL-15 and IL-2 in vitro, and undergo increased bystander proliferation and vigorous homeostatic expansion in vivo. Sorted CD8+CD44high T cells from SOCS1−/−IFN-γ−/− mice respond 5 times more strongly than control cells, indicating that SOCS1 is a critical regulator of IL-15R signaling. Consistent with this idea, IL-15 stimulates sustained STAT5 phosphorylation in SOCS1-deficient CD8+ T cells. IL-15 strongly induces TNF-α production in SOCS1-deficient CD8+ T cells, indicating that SOCS1 is also a critical regulator of CD8+ T cell activation by IL-15. However, IL-15 and IL-2 induce comparable levels of Bcl-2 and Bcl-xL in SOCS1-deficient and SOCS1-sufficient CD8+ T cells, suggesting that cytokine receptor signals required for inducing proliferation and cell survival signals are not identical. These results show that SOCS1 differentially regulates common γ-chain cytokine signaling in CD8+ T cells and suggest that CD8+ T cell homeostasis is maintained by distinct mechanisms that control cytokine-mediated survival and proliferation signals.
Differential c-Myc Responsiveness to B Cell Receptor Ligation in B Cell-Negative Selection
Authors: Leider Nira , Melamed Doron
Published: April 2014

Responsiveness of c-Myc oncogene to B cell receptor ligation has been implicated in the induction of apoptosis in transformed and normal immature B cells. These studies provided compelling evidence to link the c-Myc oncogene with the process of negative selection in B-lymphocytes. However, in addition to apoptosis, B cell-negative selection has been shown to occur by secondary Ig gene rearrangements, a mechanism called receptor editing. In this study, we assessed whether differential c-Myc responsiveness to B cell receptor (BCR) ligation is associated with the mechanism of negative selection in immature B cells. Using an in vitro bone marrow culture system and an Ig-transgenic mouse model (3-83) we show here that c-Myc is expressed at low levels throughout B cell development and that c-Myc responsiveness to BCR ligation is developmentally regulated and increased with maturation. Furthermore, we found that the competence to mount c-Myc responsiveness upon BCR ligation is important for the induction of apoptosis and had no effect on the process of receptor editing. Therefore, this study suggests an important role of c-Myc in promoting and/or maintaining B cell development and that compartmentalization of B cell tolerance may also be developmentally regulated by differential c-Myc responsiveness.
Adenoviral Infection Decreases Mortality from Lipopolysaccharide-Induced Liver Failure Via Induction of TNF-α Tolerance
Authors: Yarovinsky Timur O. , Powers Linda S. , Butler Noah S. , Bradford Mary A. , Monick Martha M. , Hunninghake Gary W.
Published: April 2014

Effects of adenoviral infection on in vivo responses to LPS mediated by TNF-α were evaluated in a murine model. Adenovirus-infected mice showed decreased mortality from fulminant hepatitis induced by administration of LPS or staphylococcal enterotoxin B in the presence of D-galactosamine. Importantly, TNF-α resistance genes within adenoviral E3 region were not required, because E1,E3-deleted vectors showed similar effects. Adenovirus-infected mice exhibited higher TNF-α levels after LPS stimulation, no difference in TNFR1 expression, and similar mortality from Fas-induced fulminant hepatitis. Decreased production of IL-6 and KC in response to exogenous TNF-α, in addition to protection from TNF-α, suggested that adenoviral infection results in TNF-α tolerance.
Effect of Promoter Methylation on the Regulation ofIFN-γ Gene During In Vitro Differentiation of Human Peripheral Blood T Cells into a Th2 Population
Authors: Yano Shingo , Ghosh Paritosh , Kusaba Hitoshi , Buchholz Meredith , Longo Dan L.
Published: April 2014

The carefully orchestrated events that result in a protective immune response are coordinated to a large extent by cytokines produced by Th1 and Th2 cell subsets. Th1 cells preferentially produce IL-2 and IFN-γ, resulting in a cellular response that helps to eliminate infected cells. In contrast, Th2 cells produce IL-4, IL-5, IL-6, and IL-10, stimulating an Ab response that attacks extracellular pathogens, thereby preventing the cells from becoming infected. To elucidate the mechanisms of differential regulation of cytokine genes by these two different subsets of T cells, we established an in vitro differentiation model of freshly isolated human peripheral blood T cells in which IFN-γ was used as an index gene to study the transcriptional regulation. The data presented here demonstrate that the IFN-γ promoter undergoes differential methylation during in vitro differentiation: the promoter becomes hypermethylated in Th2 cells, whereas it is hypomethylated in Th1 cells. Hypermethylation in Th2 cells results in chromatin condensation and exclusion of CREB proteins from the IFN-γ promoter. Treatment with 5-azacytidine, a demethylating agent, causes Th2 cells to reverse histone condensation and enables CREB recruitment to the hypomethylated promoter. This results in the increased production of IFN-γ. These data indicate the importance of promoter methylation in the regulation of the IFN-γ gene during differentiation.
Prime-Boost Vaccination with HIV-1 Gag Protein and Cytosine Phosphate Guanosine Oligodeoxynucleotide, Followed by Adenovirus, Induces Sustained and Robust Humoral and Cellular Immune Responses
Authors: Tritel Marc , Stoddard Amy M. , Flynn Barbara J. , Darrah Patricia A. , Wu Chang-you , Wille Ulrike , Shah Javeed A. , Huang Yue , Xu Ling , Betts Michael R. , Nabel Gary J. , Seder Robert A.
Published: April 2014

A prophylactic vaccine for HIV-1 will probably require the induction and maintenance of both humoral and cellular immunity. One current strategy to achieve such long term immune responses is a prime-boost vaccination approach using a DNA priming inoculation, followed by recombinant viral boost. In this report we use a novel prime-boost approach in which the priming injections consist of recombinant HIV-1 Gag protein mixed with cytosine phosphate guanosine oligodeoxynucleotide (CpG ODN), followed by recombinant adenoviral boost expressing HIV-1 Gag. Analysis of the immune responses indicates that HIV-1 Gag protein plus CpG ODN immunization alone induces potent humoral as well as Th1 and CD8+ T cell responses. Boosting with recombinant adenovirus strikingly enhances CD8+, but not Th1, T cell responses, resulting in CD8+ T cell responses far greater in magnitude than Th1 responses. Furthermore, the Th1 and CD8+ T cell responses following prime-boost immunization were seen in both lymphoid and peripheral mucosal organs and were sustained over several months. Together, these data suggest a new immunization approach for elicitation of long term humoral and cellular immune responses.
Epitope-Enhanced Conserved HIV-1 Peptide Protects HLA-A2-Transgenic Mice Against Virus Expressing HIV-1 Antigen
Authors: Okazaki Takahiro , Pendleton C. David , Lemonnier François , Berzofsky Jay A.
Published: April 2014

HIV epitopes may have developed to be poor immunogens. As a counterapproach HIV vaccine strategy, we used epitope enhancement of a conserved HIV reverse transcriptase (RT) epitope for induction of antiviral protection in HLA-A2-transgenic mice mediated by human HLA-A2-restricted CTLs. We designed two epitope-enhanced peptides based on affinity for HLA-A2, one substituted in anchor residues (RT-2L9V) and the other also with tyrosine at position 1 (RT-1Y2L9V), and examined the balance between HLA binding and T cell recognition. CTL lines and bulk cultures in two HLA-A2-transgenic mouse strains showed that RT-2L9V was more effective in inducing CTL reactive with wild-type Ag than RT-1Y2L9V, despite the higher affinity of the latter, because the 1Y substitution unexpectedly altered T cell recognition. Accordingly, RT-2L9V afforded the greatest protection in vivo against a surrogate virus expressing HIV-1 RT mediated by HLA-A2-restricted CTL in a mouse in which all CTL are restricted to only the human HLA molecule. Such antiviral protection has not been previously achieved with an HLA epitope-enhanced vaccine. These findings define a critical balance between MHC affinity and receptor cross-reactivity required for effective epitope enhancement and also demonstrate construction and efficacy of such a component of a new generation vaccine.
Intracellular Mediators of Granulysin-Induced Cell Death
Authors: Okada Satoshi , Li Qing , Whitin John C. , Clayberger Carol , Krensky Alan M.
Published: April 2014

Granulysin, a molecule present in the granules of CTL and NK cells, is cytolytic against microbes and tumors. Granulysin induces apoptosis of mammalian cells by damaging mitochondria and causing the release of cytochrome c and apoptosis-inducing factor, resulting in DNA fragmentation. Here we show that Ca2+ and K+ channels as well as reactive oxygen species are involved in granulysin-mediated Jurkat cell death. The Ca2+ channel blockers, nickel and econazole, and the K+ channel blockers, tetraethylammonium chloride, apamin, and charybdotoxin, inhibit the granulysin-induced increase in intracellular Ca2+ ([Ca2+]i), the decrease in intracellular K+, and apoptosis. Thapsigargin, which releases Ca2+ from the endoplasmic reticulum, prevents a subsequent granulysin-induced increase in [Ca2+]i in Jurkat cells, indicating that the initial increase in [Ca2+]i is from intracellular stores. The rise in [Ca2+]i precedes a decrease in intracellular K+, and elevated extracellular K+ prevents granulysin-mediated cell death. In granulysin-treated cells, electron transport is uncoupled, and reactive oxygen species are generated. Finally, an increase in intracellular glutathione protects target cells from granulysin-induced lysis, indicating the importance of the redox state in granulysin-mediated cell death.
C1 Inhibitor Prevents Endotoxin Shock Via a Direct Interaction with Lipopolysaccharide
Authors: Liu Dongxu , Cai Shenghe , Gu Xiaogang , Scafidi Jennifer , Wu Xiao , Davis Alvin E.
Published: April 2014

C1 inhibitor (C1INH) is beneficial in animal models of endotoxemia and sepsis. However, the mechanism(s) of C1INH protection remain(s) ill-defined. In this study, we demonstrated that both active C1INH and reactive center-cleaved, inactive C1INH protected mice from lethal Gram-negative endotoxemia. Both forms of C1INH blocked the LPS-binding protein-dependent binding of Salmonella typhimurium LPS to the murine macrophage cell line, RAW 264.7, and suppressed LPS-induced TNF-α mRNA expression. Inhibition of LPS binding to RAW 264.7 cells was reversed with anti-C1INH Ab and was more efficient when C1INH was incubated first with LPS rather than with the cells. C1INH also suppressed LPS-induced up-regulation of TNF-α mRNA in whole human blood. The interaction of C1INH with LPS was directly demonstrated both by ELISA and by nondenaturing PAGE, but deletion of the amino-terminal 97-aa residues abrogated this binding. Therefore, C1INH, in addition to its function as a serine protease inhibitor, has a novel anti-inflammatory function mediated via its heavily glycosylated amino-terminal non-serpin domain.
Apoptotic Cells and Innate Immune Stimuli Combine to Regulate Macrophage Cytokine Secretion
Authors: Lucas Mark , Stuart Lynda M. , Savill John , Lacy-Hulbert Adam
Published: April 2014

Macrophage interactions with apoptotic cells can suppress inflammatory responses, but cell death by apoptosis may also trigger inflammation. We now report that murine macrophages exposed to the combination of apoptotic cells and archetypal ligands for Toll-like receptors (TLRs) 2, 4, and 9 mount cytokine responses that differ importantly from those elicited by either class of stimulus alone. TLR ligands induced early and sustained secretion of TNF-α, macrophage-inflammatory protein (MIP) 1α and MIP-2 with later secretion of IL-10, IL-12, and TGF-β1; apoptotic cells alone stimulated late TGF-β1 secretion only. The combination of apoptotic cells and TLR ligands enhanced early secretion of TNF-α, MIP-1α, and MIP-2 and increased late TGF-β1 secretion, while suppressing late TNF-α, IL-10, and Il-12 by mechanisms which could nevertheless be overridden by IFN-γ. We propose that this combinatorial macrophage cytokine response to apoptotic cells and TLR ligands may contribute to recruitment and activation of innate immune defense when cell death occurs at infected inflamed sites while promoting later resolution with diminished engagement of adaptive immunity.
Inhibition of Rho Family GTPases Results in Increased TNF-α Production After Lipopolysaccharide Exposure
Authors: Monick Martha M. , Powers Linda S. , Butler Noah S. , Hunninghake Gary W.
Published: April 2014

These studies demonstrate that treatment of macrophages with lovastatin, a cholesterol-lowering drug that blocks farnesylation and geranylgeranylation of target proteins, increases LPS-induced TNF-α production. This is reversed by the addition of mevalonate, which bypasses the lovastatin block. Examination of membrane localization of RhoA, Cdc42, Rac1, and Ras demonstrated decreased membrane localization of the geranylgeranylated Rho family members (RhoA, Cdc42, and Rac1) with no change in the membrane localization of farnesylated Ras. LPS-induced TNF-α production in the presence of the Rho family-specific blocker (toxin B from Clostridium difficile) was significantly enhanced consistent with the lovastatin data. One intracellular signaling pathway that is required for TNF-α production by LPS is the extracellular signal-regulated kinase (ERK). Significantly, we found prolonged ERK activation after LPS stimulation of lovastatin-treated macrophages. When we inhibited ERK, we blocked the lovastatin-induced increase in TNF-α production. As a composite, these studies demonstrate a negative role for one or more Rho family GTPases in LPS-induced TNF-α production.
M-CSF Induces Vascular Endothelial Growth Factor Production and Angiogenic Activity From Human Monocytes
Authors: Eubank Tim D. , Galloway Michelle , Montague Christine M. , Waldman W. James , Marsh Clay B.
Published: April 2014

The impact of the immune response in malignancy is poorly understood. While immune cells can destroy transformed cells, the targeting and accumulation of monocytes and macrophages at tumor sites may promote tumor metastases. The growth factor M-CSF is important in promoting monocyte survival. Since M-CSF−/− mice are protected against tumor metastases, we hypothesized that M-CSF induced monocytes to produce angiogenic factors that facilitate metastases. In this study we demonstrate that recombinant human M-CSF induces freshly isolated normal human monocytes to produce and release the growth factor vascular endothelial growth factor (VEGF) in a dose-dependent manner, which peaked at 5 days in culture. VEGF released by these monocytes is biologically active, as cell-free supernatants from these M-CSF-stimulated monocytes induced tube formation in HUVEC. Network formation by these HUVECs after treatment with supernatants from monocytes stimulated with M-CSF were inhibited by anti-VEGF, but not by the isogenic control, Abs. Collectively, these data support an important role for M-CSF and monocytes in VEGF production and angiogenesis.
Immunoregulatory Role of Ocular Macrophages: The Macrophages Produce RANTES to Suppress Experimental Autoimmune Uveitis
Authors: Sonoda Koh-Hei , Sasa Yukio , Qiao Hong , Tsutsumi Chikako , Hisatomi Toshio , Komiyama Sohtaro , Kubota Toshiaki , Sakamoto Taiji , Kawano Yoh-Ichi , Ishibashi Tatsuro
Published: April 2014

Murine experimental autoimmune uveitis (EAU) is a model of human uveitis. Ocular-infiltrating macrophages play a crucial role in the generation of tissue damage in EAU. In fact, several chemokines are actually produced in the inflamed eye. The aim of this study was to elucidate the role of ocular macrophage-derived chemokines in EAU. C57BL/6 mice were immunized with human interphotoreceptor retinoid binding protein peptide 1–20, and the EAU severity was scored at multiple time points based on microscopic fundus observations (retinal vascular dilatation and exudates) and histological examinations. The peak inflammatory response was observed 1 wk (day 16) after the beginning of macrophage infiltration to the eye (day 9). Ocular-infiltrating cells were enriched or depleted of macrophages by magnetic beads and analyzed by real-time RT-PCR for chemokine mRNA production. We found that only the macrophage-enriched cells from the eye produced RANTES, and thus proposed that macrophage-derived RANTES facilitated the ocular inflammations. In contrast to our postulate, neutralization of RANTES by specific Ab in vivo on days 9 and 13 exacerbated EAU. We also found that the ratio of ocular CD4/CD8 T cells was markedly increased after treatment. As a result, RANTES neutralization might exacerbate EAU by modulating the type of T cell subsets recruited to the eye. In conclusion, our data provide insight into the immunoregulatory role of macrophages and RANTES in the pathogenesis of ocular inflammation. Not all macrophage-derived chemokines cause local inflammation, since RANTES produced by ocular macrophages appears to suppress EAU.
Definition of TCR Epitopes for CTL-Mediated Attack of Cutaneous T Cell Lymphoma
Authors: Winter Dorian , Fiebiger Edda , Meraner Paul , Auer Herbert , Brna Christine , Strohal Robert , Trautinger Franz , Knobler Robert , Fischer Gottfried F. , Stingl Georg , Maurer Dieter
Published: April 2014

Therapeutic vaccination against cutaneous T cell lymphoma (CTCL) requires the characterization of cancer cell-specific CTL epitopes. Despite reported evidence for tumor-reactive cytotoxicity in CTCL patients, the nature of the recognized determinants remains elusive. The clonotypic TCR of CTCL cells is a promising candidate tumor-specific Ag. In this study, we report that the clonotypic and framework regions of the TCRs expressed in the malignant T cell clones of six CTCL patients contain multiple peptides with anchor residues fitting the patients’ MHC class I molecules. We demonstrate that TCR peptide-specific T cells from the blood of healthy donors and patients can be induced to become cytotoxic effectors after repeated stimulation with 6 of 11 selected peptides with experimentally proven affinity for HLA-A*0201. Importantly, 4 of these 6 CTL lines reproducibly recognize and lyse autologous primary CTCL cells in MHC class I/CD8-dependent fashion. These tumoricidal CTL lines are directed against epitopes from V, hypervariable, and C regions of TCRα. We therefore conclude that recombined as well as V framework regions of the tumor cell TCRs contain predictable epitopes for CTL-mediated attack of CTCL cells. Our data further suggest that such peptides represent valuable tools for future anti-CTCL vaccination approaches.
Cutting Edge: Effector Memory CD8+ T Cells in the Lung Airways Retain the Potential to Mediate Recall Responses
Authors: Ely Kenneth H. , Roberts Alan D. , Woodland David L.
Published: April 2014

Previous studies have shown that long-lived memory CD8+ T cells persist in the lung airways following the resolution of a murine Sendai virus infection. These cells are CD11alow, noncytolytic, and do not proliferate in the lung airways raising the possibility that they are “end stage” or terminally differentiated memory cells. In this current report, we investigated the functional characteristics of these cells by analyzing their capacity to respond to secondary viral infection outside of the lung environment. We show that, after transfer into the bloodstream, CD11alow memory T cells from the lung airways can return to the secondary lymphoid tissue and respond to a secondary viral challenge. Furthermore, these cells re-express CD11a, which may contribute to their migratory and proliferative capacity. These data demonstrate that lung airway memory CD8+ T cells are not terminally differentiated cells and retain the capacity to mediate recall responses to infection.
Cutting Edge: Signaling and Cell Surface Expression of a μH Chain in the Absence of λ5: A Paradigm Revisited
Authors: Schuh Wolfgang , Meister Silke , Roth Edith , Jäck Hans-Martin
Published: April 2014

Pre-B cell receptor (pre-BCR) signals are essential for pro-B cells to mature efficiently into pre-B cells. The pre-BCR is an Ig-like transmembrane complex that is assembled from two μH chains (μHC) and two surrogate L chains consisting of the non-covalently associated polypeptides VpreB and λ5. In λ5−/− mice, pro-B cell maturation is impaired, but not completely blocked, implying that a μHC induces differentiation signals in the absence of λ5. Using a mouse model, in which transgenic μHC expression can be controlled by tetracycline, we show that in the absence of λ5, the transgenic μHC promotes in vivo differentiation of pro-B cells, induces IL-7-dependent cell growth, and is expressed on the surface of pre-B cells. Our findings not only show that an incomplete pre-BCR can initiate signals, but also challenge the paradigm that an IgHC must associate with an IgLC or a SLC to gain transport and signaling competency.
IFN-α Skews Monocyte Differentiation into Toll-Like Receptor 7-Expressing Dendritic Cells with Potent Functional Activities
Authors: Mohty Mohamad , Vialle-Castellano Alexandra , Nunes Jacques A. , Isnardon Daniel , Olive Daniel , Gaugler Béatrice
Published: April 2014

IFN-α is an important cytokine for the generation of a protective T cell-mediated immune response to viruses. In this study, we asked whether IFN-α can regulate the functional properties of dendritic cells (DCs). We show that monocytes cultured in the presence of GM-CSF and IFN-α can differentiate into DCs (IFN-α-derived DCs (IFN-DCs)). When compared with DCs generated in the presence of GM-CSF and IL-4 (IL-4-derived DCs), IFN-DCs exhibited a typical DC morphology and expressed, in addition to DC markers CD1a and blood DC Ag 4, a similar level of costimulatory and class II MHC molecules, but a significantly higher level of MHC class I molecules. After maturation with CD40 ligand, IFN-DCs up-regulated costimulatory, class I and II MHC molecules and expressed mature DC markers such as CD83 and DC-lysosome-associated membrane protein. IFN-DCs were endowed with potent functional activities. IFN-DCs secreted large amounts of the inflammatory cytokines IL-6, IL-10, TNF-α, IL-1β, and IL-18, and promoted a Th1 response that was independent of IL-12p70 and IL-18, but substantially inhibited by IFN-α neutralization. Furthermore, immature IFN-DCs induced a potent autologous Ag-specific immune response, as evaluated by IFN-γ secretion and expansion of CD8+ T cells specific for CMV. Also, IFN-DCs expressed a large number of Toll-like receptors (TLRs), including acquisition of TLR7, which is classically found on the natural type I IFN-producing plasmacytoid DCs. Like plasmacytoid DCs, IFN-DCs could secrete IFN-α following viral stimulation or TLR7-specific stimulation. Taken together, these results illustrate the critical role of IFN-α at the early steps of immune response to pathogens or in autoimmune diseases.
T/NK Bipotent Progenitors in the Thymus Retain the Potential to Generate Dendritic Cells
Authors: Shen Hui Qing , Lu Min , Ikawa Tomokatsu , Masuda Kyoko , Ohmura Koichiro , Minato Nagahiro , Katsura Yoshimoto , Kawamoto Hiroshi
Published: April 2014

We have previously shown that the earliest thymic progenitors retain the potential to generate T and NK cells and that they lose the bipotentiality to give rise to unipotent T and NK progenitors during the progression of intrathymic developmental stages. The present study examines the ability of these thymic progenitors for generation of dendritic cells (DC) with a new clonal assay that is capable of determining the developmental potential for DC in addition to T cells and NK cells. We found that the large majority of the T/NK bipotential progenitors in the earliest population of fetal thymus was able to generate DC. Although the DC potential is lost with the progression of the differentiation stage, some of the T/NK bipotential progenitors still retain their DC potential even at the CD44+CD25+ stage.
KIR2DL4 Is an IL-2-Regulated NK Cell Receptor That Exhibits Limited Expression in Humans but Triggers Strong IFN-γ Production
Authors: Kikuchi-Maki Akiko , Yusa Sei-ichi , Catina Tracey L. , Campbell Kerry S.
Published: April 2014

Killer cell Ig-like receptor (KIR)2DL4 (2DL4, CD158d) was previously described as the only KIR expressed by every human NK cell. It is also structurally atypical among KIRs because it possesses a basic transmembrane residue, which is characteristic of many activating receptors, but also contains a cytoplasmic immunoreceptor tyrosine-based inhibitory motif (ITIM). We expressed epitope-tagged 2DL4 in an NK-like cell line to study receptor function. Three distinct 2DL4 cDNA clones were analyzed: one encoding the “conventional” 2DL4 with the cytoplasmic ITIM (2DL4.1) and two encoding different cytoplasmic truncated forms lacking the ITIM (2DL4.2 and 2DL4∗). Surprisingly, one truncated receptor (2DL4.2), which is the product of a prevalent human 2DL4 allele, was not expressed on the cell surface, indicating that some individuals may lack functional 2DL4 protein expression. Conversely, both 2DL4.1 and 2DL4∗ were expressed on the cell surface and up-regulated by IL-2. Analysis of primary NK cells with anti-2DL4 mAb confirmed the lack of surface expression in a donor with the 2DL4.2 genotype. Donors with the 2DL4.1 genotype occasionally expressed receptor only on CD56high NK cells, although their expression was up-regulated by IL-2. Interestingly, Ab engagement of epitope-tagged 2DL4 triggered rapid and robust IFN-γ production, but weak redirected cytotoxicity in an NK-like cell line, which was the opposite pattern to that observed upon engagement of another NK cell activating receptor, NKp44. Importantly, both 2DL4.1 and 2DL4∗ exhibited similar activation potential, indicating that the ITIM does not influence 2DL4.1 activating function. The unique activation properties of 2DL4 suggest linkage to a distinct signaling pathway.
Essential Role for STAT5 Signaling in CD25+CD4+ Regulatory T Cell Homeostasis and the Maintenance of Self-Tolerance
Authors: Antov Andrey , Yang Lili , Vig Monika , Baltimore David , Van Parijs Luk
Published: April 2014

A population of CD25+CD4+ regulatory T cells (T regs) functions to maintain immunological self tolerance by inhibiting autoreactive T cell responses. CD25+CD4+ T regs are present in low, but steady, numbers in the peripheral lymphoid tissues of healthy mice. Recent studies have shown that IL-2 is an essential growth factor for these cells. How this cytokine functions to regulate CD25+CD4+ T reg homeostasis and prevent autoimmune disease remains unknown. In conventional CD4+ T cells, IL-2 triggers signaling pathways that promote proliferation and survival by activating the STAT5 transcription factor and by increasing the expression of the antiapoptotic protein, Bcl-2. We show here that bcl-2 deficiency does not affect CD25+CD4+ T reg homeostasis, and that ectopic expression of this molecule fails to rescue CD25+CD4+ T reg numbers or to prevent the development of autoimmunity in IL-2-deficient mice. Furthermore, transient activation of STAT5 is sufficient to increase CD25+CD4+ T reg numbers in IL-2-deficient mice. Our study uncovers an essential role for STAT5 in maintaining CD25+CD4+ T reg homeostasis and self-tolerance.