bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional Effects of TNF-α on a Human Follicular Dendritic Cell Line: Persistent NF-κB Activation and Sensitization for Fas-Mediated Apoptosis
Authors: Park Sun-Mi , Park Hae-Young , Lee Tae H.
Published: April 2014

Follicular dendritic cells (FDC) play crucial roles in germinal center (GC) formation and differentiation of GC B cells. FDC functions are influenced by cytokines produced in the GC. Among the GC cytokines, TNF is known to be essential for the formation and maintenance of the FDC network in the GC. We found that TNF is a mitogenic growth factor to an established FDC-like cell line, HK cells. Differing from most cell types which become desensitized to TNF action, HK cells exhibited persistent TNF signaling, as demonstrated by prolonged and biphasic NF-κB activation even after 3 days of TNF treatment. As a result, antiapoptotic genes including TNFR-associated factors 1 and 2, and cellular inhibitor of apoptosis proteins 1 and 2 were persistently induced by TNF, leading to the protection against TNF-mediated cell death. However, TNF pretreatment enhanced Fas-mediated apoptosis by up-regulating surface Fas expression in an NF-κB-dependent pathway. During the GC responses, proliferation followed by FDC death has not been documented. However, our in vitro results suggest that FDCs proliferate in response to TNF, and die by Fas-mediated apoptosis whose susceptibility is enhanced by TNF, representing a mode of action for TNF in the maintenance of FDC networks by regulating the survival or death of FDC.
Regulation of Developing B Cell Survival by RelA-Containing NF-κB Complexes
Authors: Prendes Maria , Zheng Ye , Beg Amer A.
Published: April 2014

Mice deficient in the RelA (p65) subunit of NF-κB die during embryonic development. Fetal liver (FL) hemopoietic precursors from these mice were used to generate RelA-deficient lymphocytes by adoptive transfer into lethally irradiated mature lymphocyte-deficient recombination-activating gene-1−/− mice. Strikingly, RelA−/− lymphocyte generation was greatly diminished compared with that of RelA+/+ lymphocytes. The most dramatic reduction was noticed in the numbers of developing B cells, which were considerably increased when RelA−/− FL cells that were also TNFR1 deficient were used. The role of RelA was further investigated in FL-derived developing B cells in vitro. Our results show that RelA is a major component of constitutive and TNF-α-induced κB site-binding activity in developing B cells, and provide evidence for a direct role of TNF-α in killing RelA−/− B cells. The absence of RelA significantly reduced mRNA expression of the antiapoptotic genes cellular FLICE-inhibitory protein and Bcl-2. Retroviral transduction of RelA−/− B cells with either cFLIP or Bcl-2 significantly reduced TNF-α killing. Together, these results indicate that RelA plays a crucial role in regulating developing B cell survival by inhibiting TNF-α cytotoxicity.
Expression and Function of Toll-Like Receptors in Eosinophils: Activation by Toll-Like Receptor 7 Ligand
Authors: Nagase Hiroyuki , Okugawa Shu , Ota Yasuo , Yamaguchi Masao , Tomizawa Hideyuki , Matsushima Kouji , Ohta Ken , Yamamoto Kazuhiko , Hirai Koichi
Published: April 2014

We investigated the expression of a panel of Toll-like receptors (TLRs) and their functions in human eosinophils. Eosinophils constitutively expressed TLR1, TLR4, TLR7, TLR9, and TLR10 mRNAs (TLR4 greater than TLR1, TLR7, TLR9, and TLR10 greater than TLR6). In contrast, neutrophils expressed a larger variety of TLR mRNAs (TLR1, TLR2, TLR4, TLR6, TLR8 greater than TLR5, TLR9, and TLR10 greater than TLR7). Although the expression levels in eosinophils were generally less prominent compared with those in neutrophils, eosinophils expressed a higher level of TLR7. Furthermore, among various TLR ligands (S-(2,3-bis(palmitoyloxy)-(2-RS)-propyl)-N-palmitoyl-Cys-Ser-(Lys)4, poly(I:C), LPS, R-848, and CpG DNA), only R-848, a ligand of TLR7 and TLR8, regulated adhesion molecule (CD11b and L-selectin) expression, prolonged survival, and induced superoxide generation in eosinophils. Stimulation of eosinophils by R-848 led to p38 mitogen-activated protein kinase activation, and SB203580, a p38 mitogen-activated protein kinase inhibitor, almost completely attenuated R-848-induced superoxide generation. Although TLR8 mRNA expression was hardly detectable in freshly isolated eosinophils, mRNA expression of TLR8 as well as TLR7 was exclusively up-regulated by IFN-γ but not by either IL-4 or IL-5. The up-regulation of the TLRs by IFN-γ had potentially functional significance: the extent of R-848-induced modulation of adhesion molecule expression was significantly greater in cells treated with IFN-γ compared with untreated cells. Although the natural ligands for TLR7 and TLR8 have not yet been identified, our results suggest that eosinophil TLR7/8 systems represent a potentially important mechanism of a host-defensive role against viral infection and mechanism linking exacerbation of allergic inflammation and viral infection.
Broadly Increased Sensitivity to Cytotoxic T Lymphocytes Resulting from Nef Epitope Escape Mutations
Authors: Ali Ayub , Pillai Satish , Ng Hwee , Lubong Rachel , Richman Douglas D. , Jamieson Beth D. , Ding Yan , McElrath M. Juliana , Guatelli John C. , Yang Otto O.
Published: April 2014

Nef is an HIV-1 protein that is absent in most retroviruses, yet its reading frame is highly maintained despite frequent targeting by CD8+ CTL in vivo. Because Nef is not necessarily required for viral replication, this consistent maintenance suggests that Nef plays an important role(s) and substantial fitness constraints prevent its loss in vivo. The ability of Nef to down-regulate cell surface MHC class I (MHC-I) molecules and render infected cells resistant to CTL in general is likely to be an important contributing function. We demonstrate that mutational escape of HIV-1 from Nef-specific CTL in vitro leads to progeny virions that are increased in their susceptibility to CTL of specificities for proteins other than Nef. The escape mutants contain multiple nef mutations that impair the ability of the virus to down-regulate MHC-I through disruption of its reading frame as well as epitope point mutations. Given the rarity of nef frameshifts in vivo, these data support the concept that the ability to down-regulate MHC-I could be a key constraint for preservation of Nef in vivo.
Glycolipid Antigen Drives Rapid Expansion and Sustained Cytokine Production by NK T Cells
Authors: Crowe Nadine Y. , Uldrich Adam P. , Kyparissoudis Konstantinos , Hammond Kirsten J. L. , Hayakawa Yoshihiro , Sidobre Stephané , Keating Rachael , Kronenberg Mitchell , Smyth Mark J. , Godfrey Dale I.
Published: April 2014

NKT cells are enigmatic lymphocytes that respond to glycolipid Ags presented by CD1d. Although they are key immunoregulatory cells, with a critical role in immunity to cancer, infection, and autoimmune diseases, little is known about how they respond to antigenic challenge. Current theories suggest that NKT cells die within hours of stimulation, implying that their direct impact on the immune system derives from the initial cytokine burst released before their death. Here we show that NKT cell disappearance results from TCR down-regulation rather than apoptosis, and that they expand to many times their normal number in peripheral tissues within 2–3 days of stimulation, before contracting to normal numbers over subsequent days. This expansion is associated with ongoing cytokine production, biased toward a Th1 (IFN-γ+ IL-4−) phenotype, in contrast to their initial Th0 (IFN-γ+IL-4+) phenotype. This study provides critical new insight into how NKT cells can have such a major impact on immune responses, lasting many days beyond the initial stimulation of these cells.
Dynamics of Pathogenic and Suppressor T Cells in Autoimmune Diabetes Development
Authors: Gregori Silvia , Giarratana Nadia , Smiroldo Simona , Adorini Luciano
Published: April 2014

In the nonobese diabetic (NOD) mouse, pathogenic and suppressor CD4+ T cells can be distinguished by the constitutive expression of CD25. In this study, we demonstrate that the progression of autoimmune diabetes in NOD mice reflects modifications in both T cell subsets. CD4+CD25+ suppressor T cells from 8-, but not 16-wk-old NOD mice delayed the onset of diabetes transferred by 16-wk-old CD25-depleted spleen cells. These results were paralleled by the inhibition of alloantigen-induced proliferation of CD4+CD25− cells, indicating an age-dependent decrease in suppressive activity. In addition, CD4+CD25− pathogenic T cells became progressively less sensitive to immunoregulation by CD4+CD25+ T cells during diabetes development. CD4+CD25− T cells showed a higher proliferation and produced more IFN-γ, but less IL-4 and IL-10, whereas CD4+CD25+ T suppressor cells produced significantly lower levels of IL-10 in 16- compared with 8-wk-old NOD mice. Consistent with these findings, a higher frequency of Th1 cells was observed in the pancreas of 16-wk-old compared with 8-wk-old NOD mice. An increased percentage of CD4+CD25− T cells expressing CD54 was present in 16-wk-old and in diabetic NOD, but not in BALB/c mice. Costimulation via CD54 increased the proliferation of CD4+CD25− T cells from 16-, but not 8-wk-old NOD mice, and blocking CD54 prevented their proliferation, consistent with the role of CD54 in diabetes development. Thus, the pathogenesis of autoimmune diabetes in NOD mice is correlated with both an enhanced pathogenicity of CD4+CD25− T cells and a decreased suppressive activity of CD4+CD25+ T cells.
The Central Tolerance Response to Male Antigen in Normal Mice Is Deletion and Not Receptor Editing
Authors: Holman Philmore O. , Walsh Elizabeth R. , Hogquist Kristin A.
Published: April 2014

It is widely accepted that developing T cells can undergo clonal deletion in the thymus in response to a high affinity self-Ag. This is largely based on studies of TCR transgenics. However, encounter with high affinity self-Ag can also result in receptor editing in TCR transgenic models. Because all TCR transgenics display ectopic receptor expression, the tolerance mechanism that predominates in normal mice remains an open question. When self-Ag drives receptor editing during T cell development, one expects to find in-frame, self-reactive TCRα joins on TCR excision circles (TRECs), which are the products of secondary V/J recombination in the TCRα locus. Such joins are not expected if clonal deletion occurs, because the progenitor cell would be eliminated by apoptosis. To test the relative utilization of receptor editing vs clonal deletion, we determined the frequency of in-frame, male-specific joins on TRECs in male and female HYβ transgenic mice. In comparison with female HYβ transgenic mice, our analysis showed a lower frequency of TRECs with male-reactive V17J57 joins in male mice. Thus, it would appear that receptor editing is not a predominant tolerance mechanism for this self-Ag.
HSP110-HER2/neu Chaperone Complex Vaccine Induces Protective Immunity Against Spontaneous Mammary Tumors in HER-2/neu Transgenic Mice
Authors: Manjili Masoud H. , Wang Xiang-Yang , Chen Xing , Martin Thomas , Repasky Elizabeth A. , Henderson Robert , Subjeck John R.
Published: April 2014

Heat shock proteins (HSPs) are shown to be strong immunoadjuvants, eliciting both innate and adaptive immune responses against cancers. HSP110 is related in sequence to HSP70 and is ∼4-fold more efficient in binding to and stabilizing denatured protein substrates compared with HSP70. In the present study we evaluated the ability of a heat shock complex of HSP110 with the intracellular domain (ICD) of human HER-2/neu to elicit effective antitumor immune responses and to inhibit spontaneous mammary tumors in FVB-neu (FVBN202) transgenic mice. The HSP110-ICD complex was capable of breaking tolerance against the rat neu protein and inhibiting spontaneous mammary tumor development. This vaccine induced ICD-specific IFN-γ and IL-4 production. Depletion studies revealed that CD8+ T cells were involved in protection against challenge with mouse mammary tumors, whereas CD4+ T cells revealed partial protection. Increased IgG2a Ab titer in the sera of tumor-free animals after vaccination and elevated CD4+ CD25+ regulatory T cells in the PBL of tumor-bearing animals suggested that IFN-γ-producing Th1 cells may be responsible for partial protection of CD4+ T cells against the mammary tumor challenge, whereas CD4+CD25+ regulatory T cells (Th2 cells) may suppress the antitumor immune responses. Together, these results suggest that HSP110-ICD complex can elicit effective IFN-γ-producing T cells against spontaneous mammary tumors and that up-regulation of CD4+ CD25+ regulatory T cells may prevent complete eradication of the tumor following immunotherapy.
Functional Segregation of the TCR and Antigen-MHC Complexes on the Surface of CTL
Authors: Mekala Divya J. , Geiger Terrence L.
Published: April 2014

As CTL adhere to and lyze their targets, they extract cognate Ag-MHC and represent this on their own cell surface. Whether such self-presented cognate Ag stimulate the TCR of a CTL is uncertain. To analyze this, we examined TCR capping in response to self-presented Ag. We found that OVA peptide-specific OT-1 CTL that were pulsed with cognate peptide Ag did not cap their TCR, implying that the autologously presented MHC-Ag complex does not normally stimulate the TCR. However, this functional separation of the TCR and its ligand on the cell surface was not absolute. Treatment of Ag-pulsed OT-1 CTL with agents that alter cell surface charge, including trypsin, papain, tunicamycin, neuraminidase, and polybrene, allowed Ag-specific TCR capping. The TCR capped together with the restricting MHC molecule on the surface of the cell, implying an interaction between the TCR and cell-associated Ag. Further, the treated CTL underwent a time- and dose-dependent suicidal death that was both Fas- and perforin-dependent. Therefore, our results indicate that the association of the TCR with its MHC-peptide ligand on the surface of a CTL is normally proscribed by biophysical properties of the plasma membrane. Overcoming this restriction allows TCR stimulation and induces CTL effector functions and cell suicide.
T Cell-Specific Disruption of Arylhydrocarbon Receptor Nuclear Translocator (Arnt) Gene Causes Resistance to 2,3,7,8-Tetrachlorodibenzo-p-dioxin-Induced Thymic Involution
Authors: Tomita Shuhei , Jiang Hou-Bo , Ueno Tomoo , Takagi Satoshi , Tohi Keiko , Maekawa Shin-ichi , Miyatake Akira , Furukawa Aizo , Gonzalez Frank J. , Takeda Junji , Ichikawa Yoshiyuki , Takahama Yousuke
Published: April 2014

The arylhydrocarbon receptor nuclear translocator (ARNT) is a member of the basic helix-loop-helix, PER-ARNT-SIM family of heterodimeric transcription factors, and serves as a dimerization partner for arylhydrocarbon receptor (AHR) and hypoxia-inducible factor-1α. To assess the function of ARNT in T cells, we disrupted the Arnt gene specifically in T cells of mice by conditional gene targeting using T cell-specific p56lck-Cre (Lck-Cre) transgenic Arnt-floxed mice. Thus generated, T cell-specific Arnt-disrupted mice (Lck-Cre;Arntflox/Δ transgenic mice) exhibited complete loss of the expression of ARNT protein only in T cells, and were viable and appeared normal. The Arnt-disrupted T cells in the thymus were phenotypically and histologically normal. The Arnt-deficient T cells in the spleen were capable of responding to TCR stimulation in vitro. However, unlike normal mice in which exposure to the environmental pollutant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an AHR ligand, resulted in thymic involution, the thymus of Lck-Cre;Arntflox/Δ mice were resistant to TCDD treatment in vivo. In contrast, benzo(a)pyrene, another AHR ligand, still caused thymic involution in Lck-Cre;Arntflox/Δ mice. Finally, fetal thymus organ culture using Lck-Cre;Arntflox/Δ and K5-Cre;Arntflox/Δ (epithelial cell-specific Arnt-disrupted mice) showed that thymocytes rather than thymic epithelial cells are predominantly responsible for TCDD-induced thymic atrophy. Our results indicate that ARNT in T lineage cells is essential for TCDD-mediated thymic involution.
Enhanced Effector and Memory CTL Responses Generated by Incorporation of Receptor Activator of NF-κB (RANK)/RANK Ligand Costimulatory Molecules into Dendritic Cell Immunogens Expressing a Human Tumor-Specific Antigen
Authors: Wiethe Carsten , Dittmar Kurt , Doan Tracy , Lindenmaier Werner , Tindle Robert
Published: April 2014

The outcome of dendritic cell (DC) presentation of Ag to T cells via the TCR/MHC synapse is determined by second signaling through CD80/86 and, importantly, by ligation of costimulatory ligands and receptors located at the DC and T cell surfaces. Downstream signaling triggered by costimulatory molecule ligation results in reciprocal DC and T cell activation and survival, which predisposes to enhanced T cell-mediated immune responses. In this study, we used adenoviral vectors to express a model tumor Ag (the E7 oncoprotein of human papillomavirus 16) with or without coexpression of receptor activator of NF-κB (RANK)/RANK ligand (RANKL) or CD40/CD40L costimulatory molecules, and used these transgenic DCs to immunize mice for the generation of E7-directed CD8+ T cell responses. We show that coexpression of RANK/RANKL, but not CD40/CD40L, in E7-expressing DCs augmented E7-specific IFN-γ-secreting effector and memory T cells and E7-specific CTLs. These responses were also augmented by coexpression of T cell costimulatory molecules (RANKL and CD40L) or DC costimulatory molecules (RANK and CD40) in the E7-expressing DC immunogens. Augmentation of CTL responses correlated with up-regulation of CD80 and CD86 expression in DCs transduced with costimulatory molecules, suggesting a mechanism for enhanced T cell activation/survival. These results have generic implications for improved tumor Ag-expressing DC vaccines, and specific implications for a DC-based vaccine approach for human papillomavirus 16-associated cervical carcinoma.
Lysosomal Localization of Murine CD1d Mediated by AP-3 Is Necessary for NK T Cell Development
Authors: Cernadas Manuela , Sugita Masahiko , van der Wel Nicole , Cao Xiaochun , Gumperz Jenny E. , Maltsev Sergei , Besra Gurdyal S. , Behar Samuel M. , Peters Peter J. , Brenner Michael B.
Published: April 2014

The presentation of lipid and glycolipid Ags to T cells is mediated through CD1 molecules. In the mouse and rat only a single isoform, CD1d, performs these functions, while humans and all other mammals studied have members of both group I (CD1a, -b, and -c) and group II (CD1d) isoforms. Murine CD1d contains a cytoplasmic tyrosine-based sorting motif that is similar to motifs recognized by adaptor protein complexes that sort transmembrane proteins. Here we show that the adaptor protein complex, AP-3, directly interacts with murine CD1d and controls its targeting to lysosomes. AP-3 deficiency results in a redistribution of CD1d from lysosomes to the cell surface of thymocytes, B cell-depleted splenocytes, and dendritic cells. The altered trafficking of CD1d in AP-3-deficient mice results in a significant reduction of NK1.1+TCR-β+ and CD1d tetramer-positive cells, consistent with a defect in CD1d self-Ag presentation and thymocyte-positive selection. The AP-3 complex has recently been shown to associate with the human CD1b isoform, which has an intracellular distribution pattern similar to that of murine CD1d. We propose that lysosomal sampling may be so critical for efficient host defense that mice have evolved mechanisms to target their single CD1 isoform to lysosomes for sampling lipid Ags. Here we show the dominant mechanism for this trafficking is mediated by AP-3.
Blockade of B7-H1 Suppresses the Development of Chronic Intestinal Inflammation
Authors: Kanai Takanori , Totsuka Teruji , Uraushihara Koji , Makita Shin , Nakamura Tetsuya , Koganei Kazutaka , Fukushima Tsuneo , Akiba Hisaya , Yagita Hideo , Okumura Ko , Machida Utako , Iwai Hideyuki , Azuma Miyuki , Chen Lieping , Watanabe Mamoru
Published: April 2014

A newly identified costimulatory molecule, programmed death-1 (PD-1), provides a negative signal that is essential for immune homeostasis. However, it has been suggested that its ligands, B7-H1 (PD-L1) and B7-dendritic cells (B7-DC; PD-L2), could also costimulate T cell proliferation and cytokine secretion. Here we demonstrate the involvement of PD-1/B7-H1 and B7-DC interaction in the development of colitis. We first examined the expression profiles of PD-1 and its ligands in both human inflammatory bowel disease and a murine chronic colitis model induced by adoptive transfer of CD4+CD45RBhigh T cells to SCID mice. Second, we assessed the therapeutic potential of neutralizing anti-B7-H1 and/or B7-DC mAbs using this colitis model. We found significantly increased expression of PD-1 on T cells and of B7-H1 on T, B, and macrophage/DCs in inflamed colon from both inflammatory bowel disease patients and colitic mice. Unexpectedly, the administration of anti-B7-H1, but not anti-B7-DC, mAb after transfer of CD4+CD45RBhigh T cells suppressed wasting disease with colitis, abrogated leukocyte infiltration, and reduced the production of IFN-γ, IL-2, and TNF-α, but not IL-4 or IL-10, by lamina propria CD4+ T cells. These data suggest that the interaction of PD-1/B7-H1, but not PD-1/B7-DC, might be involved in intestinal mucosal inflammation and also show a possible role of interaction between B7-H1 and an as yet unidentified receptor for B7-H1 in inducing T cell activation.
Ex Vivo Analysis of Thymic CD4 T Cells in Nonobese Diabetic Mice with Tetramers Generated from I-Ag7/Class II-Associated Invariant Chain Peptide Precursors
Authors: Jang Mei-Huei , Seth Nilufer P. , Wucherpfennig Kai W.
Published: April 2014

The MHC determines susceptibility and resistance to type 1 diabetes in humans and nonobese diabetic (NOD) mice. To investigate how a disease-associated MHC molecule shapes the T cell repertoire in NOD mice, we generated a series of tetramers from I-Ag7/class II-associated invariant chain peptide precursors by peptide exchange. No CD4 T cell populations could be identified for two glutamic acid decarboxylase 65 peptides, but tetramers with a peptide mimetic recognized by the BDC-2.5 and other islet-specific T cell clones labeled a distinct population in the thymus of young NOD mice. Tetramer-positive cells were identified in the immature CD4+CD8low population that arises during positive selection, and in larger numbers in the more mature CD4+CD8− population. Tetramer labeling was specific based on the use of multiple control tetramers, including one with a single amino acid analog peptide in which a critical TCR contact residue was substituted. The T cell population was already present in the thymus of 2-wk-old NOD mice before the typical onset of insulitis and was detected in B10 mice congenic for the NOD MHC locus, but not B10 control mice. These results demonstrate that a T cell population can expand in the thymus of NOD mice to levels that are at least two to three orders of magnitude higher than estimated for a given specificity in the naive T cell pool. Based on these data, we propose a model in which I-Ag7 confers susceptibility to type 1 diabetes by biasing positive selection in the thymus and later presenting peptides from islet autoantigens to such T cells in the periphery.
IFN-γ-Induced MHC Class II Expression: Transactivation of Class II Transactivator Promoter IV by IFN Regulatory Factor-1 is Regulated by Protein Kinase C-α
Authors: Giroux Mélanie , Schmidt Manuel , Descoteaux Albert
Published: April 2014

Previous studies based on pharmacological evidence suggested a requirement for protein kinase C (PKC) activity in the regulation of IFN-γ-induced MHC class II (MHC-II) expression. In the present study, we investigated the molecular mechanisms by which PKC-α modulates IFN-γ-induced MHC-II expression in the mouse macrophage cell line RAW 264.7. Overexpression of a dominant-negative (DN) mutant of PKC-α inhibited the expression of IFN-γ-induced MHC-II but had no effect on IFN-γ-induced STAT1 nuclear translocation and DNA binding activity, as well as on the expression of inducible NO synthase, IFN consensus sequence binding protein, MHC class I, IFN regulatory factor (IRF)-1, and IFN-γ-inducible protein-10. Further analysis showed that IFN-γ-induced expression of the MHC class II transactivator (CIITA), a transcriptional coactivator essential for MHC-II expression, was inhibited in DN PKC-α-overexpressing cells. Studies with reporter constructs containing the promoter IV region of CIITA revealed that overexpression of a constitutively active mutant of PKC-α enhanced IRF-1, but not IRF-2, transcriptional activity. Furthermore, characterization of IRF-1 from both normal and DN PKC-α-overexpressing cells revealed differences in IRF-1 posttranslational modifications. Collectively, our data suggest a novel regulatory mechanism for IFN-γ-induced MHC-II expression, whereby PKC regulates CIITA expression by selectively modulating the transcriptional activity of IRF-1.
Phosphatidylcholine-Specific Phospholipase C Activity Is Necessary for the Activation of STAT6
Authors: Zamorano Jose , Rivas Maria Dolores , Garcia-Trinidad Antonio , Qu Cheng-Kui , Keegan Achsah D.
Published: April 2014

It is well established that Janus kinase (JAK) tyrosine kinases play a key role in the activation of STAT6 by IL-4. In this study, we investigated additional molecules involved in this process. We previously found that IL-4 and TNF-α cooperate in the activation of STAT6 and NF-κB, suggesting that these transcription factors are regulated by common intracellular signaling pathways. To test this hypothesis, we analyzed the effect of known inhibitors of NF-κB on the activation of STAT6. We discovered that inhibitors of phosphatidylcholine-specific phospholipase C (PC-PLC), but not other lipases, blocked the activation of STAT6 by IL-4. The activation of PC-PLC seems to be an early event in IL-4 signaling, because its inhibition abrogated JAK activation and STAT6 tyrosine phosphorylation. Interestingly, we found that the effects of pervanadate and sodium orthovanadate on STAT6 activation correspond to their effect on PC-PLC. Thus, pervanadate by itself activated PC-PLC, JAK, and STAT6, whereas sodium orthovanadate suppressed PC-PLC, JAK, and STAT6 activation by IL-4. We further found that PC-PLC activation is necessary but not sufficient to promote STAT6 activation, and therefore, additional intracellular pathways regulated by IL-4 and pervanadate may collaborate with PC-PLC to signal STAT6 activation. It has been reported that IL-4 signals PC-PLC activation; in this study, we provide evidence that this phospholipase plays a key role in IL-4 signaling.
Dual Phosphorylation of Phosphoinositide 3-Kinase Adaptor Grb2-Associated Binder 2 Is Responsible for Superoxide Formation Synergistically Stimulated by Fcγ and Formyl-Methionyl-Leucyl-Phenylalanine Receptors in Differentiated THP-1 Cells
Authors: Momose Haruka , Kurosu Hiroshi , Tsujimoto Noriko , Kontani Kenji , Tsujita Kyoko , Nishina Hiroshi , Katada Toshiaki
Published: April 2014

The class Ia phosphoinositide (PI) 3-kinase consisting of p110 catalytic and p85 regulatory subunits is activated by Tyr kinase-linked membrane receptors such as FcγRII through the association of p85 with the phosphorylated receptors or adaptors. The heterodimeric PI 3-kinase is also activated by G protein-coupled chemotactic fMLP receptors, and activation of the lipid kinase plays an important role in various immune responses, including superoxide formation in neutrophils. Although fMLP-induced superoxide formation is markedly enhanced in FcγRII-primed neutrophils, the molecular mechanisms remain poorly characterized. In this study, we identified two Tyr-phosphorylated proteins, c-Cbl (Casitas B-lineage lymphoma) and Grb2-associated binder 2 (Gab2), as PI 3-kinase adaptors that are Tyr phosphorylated upon the stimulation of FcγRII in differentiated neutrophil-like THP-1 cells. Interestingly, Gab2 was, but c-Cbl was not, further Ser/Thr phosphorylated by fMLP. Thus, the adaptor Gab2 appeared to be dually phosphorylated at the Ser/Thr and Tyr residues through the two different types of membrane receptors. The Ser/Thr phosphorylation of Gab2 required the activation of extracellular signal-regulated kinase, and fMLP receptor stimulation indeed activated extracellular signal-regulated kinase in the cells. Enhanced superoxide formation in response to Fcγ and fMLP was markedly attenuated when the Gab2 Ser/Thr phosphorylation was inhibited. These results show the importance of the dual phosphorylation of PI 3-kinase adaptor Gab2 for the enhanced superoxide formation in neutrophil-type cells.
Deficient Anti-Listerial Immunity in the Absence of Perforin Can Be Restored by Increasing Memory CD8+ T Cell Numbers
Authors: Messingham Kelly A. Nordyke , Badovinac Vladimir P. , Harty John T.
Published: April 2014

Compared with wild-type (WT) mice, Listeria monocytogenes (LM)-vaccinated perforin-deficient (PKO) mice have elevated levels of CD8+ T cell memory, but exhibit reduced levels of protection against virulent LM. In this study, Ag-specific CD8+ T cells from LM-vaccinated WT and PKO mice were used in adoptive transfer assays to determine the contribution of perforin-dependent cytolysis in protective immunity to LM. Perforin deficiency resulted in an ∼5-fold reduction in the per-cell protective capacity of Ag-specific memory CD8+ T cells that was not caused by differences in memory cell quality as measured by CD62L/CD27 expression, TCR repertoire use, functional avidity, differences in expansion of Ag-specific cells upon infection, or maintenance of memory levels over time. However, perforin-deficient CD8+ T cells exhibited reduced in vivo cytotoxic function compared to WT CD8+ T cells. Consistent with the existence of perforin-independent effector pathways, double-vaccinated PKO mice were as resistant to challenge with LM as single-vaccinated WT mice. Thus, increasing the number of memory CD8+ T cells can overcome diminished per-cell protective immunity in the absence of perforin.
Functional Characterization of Class Ia- and Non-Class Ia-RestrictedChlamydia-Reactive CD8+ T Cell Responses in Humans
Authors: Gervassi Ana L. , Probst Peter , Stamm Walter E. , Marrazzo Jeanne , Grabstein Kenneth H. , Alderson Mark R.
Published: April 2014

CD8+ T cells are a key immune component for the eradication of many intracellular pathogens. This study aims to characterize the human CD8+ T cell response to naturally processed chlamydial Ags in individuals exposed to the intracellular pathogen Chlamydia trachomatis. By using C. trachomatis-infected autologous dendritic cells (DCs) as stimulators, Chlamydia-reactive CD8+ T cell responses were detected in all 10 individuals tested. The majority of the Chlamydia-reactive CD8+ T cells were non-MHC class Ia restricted in all three of the individuals tested. From one donor, three non-class Ia-restricted and two class Ia-restricted Chlamydia-specific CD8+ T cells were cloned and characterized further. All five T cell clones secreted IFN-γ in response to autologous DCs infected with viable Chlamydia, but not with DCs pulsed with inactivated chlamydial elementary bodies. MHC class Ia-restricted and non-class Ia-restricted responses were inhibited by DC treatment with a proteasomal inhibitor and an endoplasmic reticulum-Golgi transport inhibitor, suggesting that these T cells recognize a peptide Ag translocated to the host cell cytosol during infection that is processed via the classical class Ia Ag-processing pathway. Even though both restricted and nonrestricted CD8+ T cells produced IFN-γ in response to Chlamydia-infected fibroblasts, only the non-class Ia-restricted cells were lytic for these targets. The class Ia-restricted CTLs, however, were capable of cytolysis as measured by redirected killing. Collectively, these data demonstrate that both class Ia-restricted and non-classically restricted CD8+ T cells are elicited in C. trachomatis-exposed individuals. Their role in host immunity remains to be elucidated.
A Dominant Role of Toll-Like Receptor 4 in the Signaling of Apoptosis in Bacteria-Faced Macrophages
Authors: Haase Rudolf , Kirschning Carsten J. , Sing Andreas , Schröttner Percy , Fukase Koichi , Kusumoto Shoichi , Wagner Hermann , Heesemann Jürgen , Ruckdeschel Klaus
Published: April 2014

Conserved bacterial components potently activate host immune cells through transmembrane Toll-like receptors (TLRs), which trigger a protective immune response but also may signal apoptosis. In this study, we investigated the roles of TLR2 and TLR4 as inducers of apoptosis in Yersinia enterocolitica-infected macrophages. Yersiniae suppress activation of the antiapoptotic NF-κB signaling pathway in host cells by inhibiting inhibitory κB kinase-β. This leads to macrophage apoptosis under infection conditions. Experiments with mouse macrophages deficient for TLR2, TLR4, or both receptors showed that, although yersiniae could activate signaling through both TLR2 and TLR4, loss of TLR4 solely diminished Yersinia-induced apoptosis. This suggests implication of TLR4, but not of TLR2, as a proapoptotic signal transducer in Yersinia-conferred cell death. In the same manner, agonist-specific activation of TLR4 efficiently mediated macrophage apoptosis in the presence of the proteasome inhibitor MG-132, an effect that was less pronounced for activation through TLR2. Furthermore, the extended stimulation of overexpressed TLR4 elicited cellular death in epithelial cells. A dominant-negative mutant of Fas-associated death domain protein could suppress TLR4-mediated cell death, which indicates that TLR4 may signal apoptosis through a Fas-associated death domain protein-dependent pathway. Together, these data show that TLR4 could act as a potent inducer of apoptosis in macrophages that encounter a bacterial pathogen.
Toll-Like Receptor Ligands Modulate Dendritic Cells to Augment Cytomegalovirus- and HIV-1-Specific T Cell Responses
Authors: Loré Karin , Betts Michael R. , Brenchley Jason M. , Kuruppu Janaki , Khojasteh Soorena , Perfetto Stephen , Roederer Mario , Seder Robert A. , Koup Richard A.
Published: April 2014

Optimal Ag targeting and activation of APCs, especially dendritic cells (DCs), are important in vaccine development. In this study, we report the effects of different Toll-like receptor (TLR)-binding compounds to enhance immune responses induced by human APCs, including CD123+ plasmacytoid DCs (PDCs), CD11c+ myeloid DCs (MDCs), monocytes, and B cells. PDCs, which express TLR7 and TLR9, responded to imidazoquinolines (imiquimod and R-848) and to CpG oligodeoxynucleotides stimulation, resulting in enhancement in expression of costimulatory molecules and induction of IFN-α and IL-12p70. In contrast, MDCs, which express TLR3, TLR4, and TLR7, responded to poly(I:C), LPS, and imidazoquinolines with phenotypic maturation and high production of IL-12 p70 without producing detectable IFN-α. Optimally TLR ligand-stimulated PDCs or MDCs exposed to CMV or HIV-1 Ags enhanced autologous CMV- and HIV-1-specific memory T cell responses as measured by effector cytokine production compared with TLR ligand-activated monocytes and B cells or unstimulated PDCs and MDCs. Together, these data show that targeting specific DC subsets using TLR ligands can enhance their ability to activate virus-specific T cells, providing information for the rational design of TLR ligands as adjuvants for vaccines or immune modulating therapy.
Compromised Host Defense on Pseudomonas aeruginosa Biofilms: Characterization of Neutrophil and Biofilm Interactions
Authors: Jesaitis Algirdas J. , Franklin Michael J. , Berglund Deborah , Sasaki Maiko , Lord Connie I. , Bleazard Justin B. , Duffy James E. , Beyenal Haluk , Lewandowski Zbigniew
Published: April 2014

Pseudomonas aeruginosa is an opportunistic pathogen that forms biofilms on tissues and other surfaces. We characterized the interaction of purified human neutrophils with P. aeruginosa, growing in biofilms, with regard to morphology, oxygen consumption, phagocytosis, and degranulation. Scanning electron and confocal laser microscopy indicated that the neutrophils retained a round, unpolarized, unstimulated morphology when exposed to P. aeruginosa PAO1 biofilms. However, transmission electron microscopy demonstrated that neutrophils, although rounded on their dorsal side, were phagocytically active with moderate membrane rearrangement on their bacteria-adjacent surfaces. The settled neutrophils lacked pseudopodia, were impaired in motility, and were enveloped by a cloud of planktonic bacteria released from the biofilms. The oxygen consumption of the biofilm/neutrophil system increased 6- and 8-fold over that of the biofilm alone or unstimulated neutrophils in suspension, respectively. H2O2 accumulation was transient, reaching a maximal measured value of 1 μM. Following contact, stimulated degranulation was 20–40% (myeloperoxidase, β-glucuronidase) and 40–80% (lactoferrin) of maximal when compared with formylmethionylleucylphenylalanine plus cytochalasin B stimulation. In summary, after neutrophils settle on P. aeruginosa biofilms, they become phagocytically engorged, partially degranulated, immobilized, and rounded. The settling also causes an increase in oxygen consumption of the system, apparently resulting from a combination of a bacterial respiration and escape response and the neutrophil respiratory burst but with little increase in the soluble concentration of H2O2. Thus, host defense becomes compromised as biofilm bacteria escape while neutrophils remain immobilized with a diminished oxidative potential.
Up-Regulation of Matrix Metalloproteinase-9 in T Lymphocytes of Mammary Tumor Bearers: Role of Vascular Endothelial Growth Factor
Authors: Owen Jennifer L. , Iragavarapu-Charyulu Vijaya , Gunja-Smith Zeenat , Herbert Lynn M. , Grosso Joseph F. , Lopez Diana M.
Published: April 2014

Matrix metalloproteinase-9 (MMP-9), a matrix-degrading enzyme, is crucial in tumor invasion and metastasis and is implicated in leukocyte extravasation. In this report, we demonstrate that during growth of the D1–7,12-dimethylbenzanthracene-3 mammary tumor in BALB/c mice, there is progressive up-regulation of MMP-9 in splenic T cells at both the transcriptional and translational levels. Our previous work has identified several factors produced by this tumor, including PGE2, GM-CSF, and phosphatidyl serine; however, none of these agents induces increased production of MMP-9 by normal splenic T cells. Although not produced by the tumor, TNF-α and IL-6 are up-regulated in both macrophages and B cells in tumor-bearing mice. Exposure of normal T cells to these two cytokines, however, also fails to up-regulate MMP-9 production. Vascular endothelial growth factor (VEGF) is produced by many tumors, and we determined that the mammary tumor used in our studies expresses high levels of this angiogenic growth factor. Importantly, splenic T cells from tumor bearers constitutively produce increased amounts of VEGF, and treatment of normal T cells with VEGF results in up-regulated MMP-9 production. Of crucial importance is the finding that tumor-infiltrating T cells also produce high levels of VEGF and MMP-9. Our studies indicate that VEGF can act directly on T lymphocytes and that elevated VEGF levels may contribute to the aberrant MMP-9 secretion by mammary tumor bearers’ T cells.
Th1-Biased Tertiary Lymphoid Tissue Supported by CXC Chemokine Ligand 13-Producing Stromal Network in Chronic Lesions of Autoimmune Gastritis
Authors: Katakai Tomoya , Hara Takahiro , Sugai Manabu , Gonda Hiroyuki , Shimizu Akira
Published: April 2014

Secondary lymphoid tissue is developmentally programmed and characterized by well-ordered compartmentalization of lymphocyte subsets and specialized stromal cells supporting the tissue architecture. By contrast, tertiary lymphoid tissue is defined as that induced in ectopic sites by inflammation, although its immunological role is largely unknown. In this study, we characterize the lymphoid tissue induced in the chronic lesion of murine autoimmune gastritis (AIG). Within the lymphoid cluster in the gastric mucosa, there is a clear segregation of T and B cells. Follicle-like B cell areas are always located on the luminal side of the mucosa, while T cells are located in the basal part. A typical lymphoid reticular network and follicular dendritic cells support the structure. Importantly, complement receptor 1+ follicular dendritic cells within the follicle express a B cell homing chemokine, CXC chemokine ligand 13. The number and size of the clusters correlate with the age of the mice and the serum autoantibody titer, suggesting the functional importance of the clusters in local Ab production, although involvement of the autoantibody in the disease progression is still unclear. AIG gastric lesions are known to constitute a Th1-biased, memory T cell-dependent immunomicroenvironment. The expression pattern of cytokines, including lymphotoxin-β, and chemokines in the AIG stomach is consistent with this observation. Taken together, these facts suggest that, during the chronic phase of autoimmunity, long-lasting lymphocyte infiltration probably induces a unique tertiary lymphoid tissue that has a function distinct from that of regional lymph nodes. These neolymphoid tissues may maintain the local self reactivity supporting the vicious cycle of Th1-type reaction as well as autoantibody production.
Defective Phagocytosis and Clearance of Pseudomonas aeruginosa in the Lung Following Bone Marrow Transplantation
Authors: Ojielo Charles I. , Cooke Kenneth , Mancuso Pete , Standiford Theodore J. , Olkiewicz Krystyna M. , Clouthier Shawn , Corrion Leigh , Ballinger Megan N. , Toews Galen B. , Paine Robert , Moore Bethany B.
Published: April 2014

Bone marrow transplantation (BMT) is an important therapeutic option for a variety of malignant and nonmalignant disorders. Unfortunately, BMT recipients are at increased risk of infection, and in particular, pulmonary complications occur frequently. Although the risk of infection is greatest during the neutropenic period immediately following transplant, patients are still vulnerable to pulmonary infections even after neutrophil engraftment. We evaluated the risk of infection in this postengraftment period by using a well-established mouse BMT model. Seven days after syngeneic BMT, B6D2F1 mice are no longer neutropenic, and by 3 wk, they demonstrate complete reconstitution of the peripheral blood. However, these mice remain more susceptible throughout 8 wk to infection after intratracheal administration of Pseudomonas aeruginosa; increased mortality in the P. aeruginosa-infected BMT mice correlates with increased bacterial burden in the lungs as well as increased systemic dissemination. This heightened susceptibility to infection was not secondary to a defect in inflammatory cell recruitment to the lung. The inability to clear P. aeruginosa in the lung correlated with reduced phagocytosis of the bacteria by alveolar macrophages (AMs), but not neutrophils, decreased production of TNF-α by AMs, and decreased levels of TNF-α and IFN-γ in the bronchoalveolar lavage fluid following infection. Expression of the β2 integrins CD11a and CD11c was reduced on AMs from BMT mice compared with wild-type mice. Thus, despite restoration of peripheral blood count, phagocytic defects in the AMs of BMT mice persist and may contribute to the increased risk of infection seen in the postengraftment period.
The Hemopoietic Rho/Rac Guanine Nucleotide Exchange Factor Vav1 Regulates N-Formyl-Methionyl-Leucyl-Phenylalanine-Activated Neutrophil Functions
Authors: Kim Chaekyun , Marchal Christophe C. , Penninger Josef , Dinauer Mary C.
Published: April 2014

Vav1 is a hemopoietic-specific Rho/Rac guanine nucleotide exchange factor that plays a prominent role in responses to multisubunit immune recognition receptors in lymphoid cells, but its contribution to regulation of neutrophil functions is unknown. Activated Rho family GTPases are critical participants in neutrophil signaling cascades initiated by binding of FMLP and other chemoattractants to their cognate G protein-coupled receptors. Therefore, we investigated whether Vav1 regulates chemoattractant-induced responses in neutrophils. We found that superoxide production elicited by FMLP in Vav1−/− murine neutrophils isolated from either bone marrow or from peritoneal exudates was substantially reduced compared with that of wild type. Filamentous actin generation in FMLP-stimulated Vav1−/− neutrophils was also markedly reduced, whereas it was normal in response to IL-8 or leukotriene B4. FMLP induced tyrosine phosphorylation of Vav1, whereas IL-8 or leukotriene B4 did not, correlating with the requirement for Vav1 in chemoattractant-stimulated filamentous actin generation. Neutrophil motility in vitro and neutrophil mobilization into peripheral blood in vivo elicited by FMLP were both decreased in Vav1−/− mice. Hence, this study defines a new role for Vav1 in regulating granulocytic leukocytes as well as linking Vav1 to specific cellular responses downstream of a seven transmembrane domain receptor.
HLA-DRB1*0402 (DW10) Transgene Protects Collagen- Induced Arthritis-Susceptible H2Aq and DRB1*0401 (DW4) Transgenic Mice from Arthritis
Authors: Taneja Veena , Taneja Neelam , Behrens Marshall , Pan Suchong , Trejo Tad , Griffiths Marie , Luthra Harvinder , David Chella S.
Published: April 2014

To investigate the role of HLA-DR4 in predisposition to arthritis, we generated transgenic mice carrying DRB1*0401 and DRB1*0402 genes. We have previously shown that DRB1*0401 molecule renders B10.RQB3 (H2Aq) mice susceptible to porcine and human type II collagen-induced arthritis. We report that the introduction of DRB1*0402 transgene does not lead to development of arthritis in mice when they are immunized with porcine and human type II collagen. In addition, DRB1*0402 protects B10.RQB3 mice against developing arthritis with bovine type II collagen. These data show that DRB1 can modulate the disease mediated by Aq. In vivo depletion of DRB1*0402 did not lead to induction of collagen-induced arthritis in transgenic mice. In vitro cytokine analysis shows that mice protected from collagen-induced arthritis produce lower amounts of Th1 and higher levels of Th2 type cytokines upon immunization with type II collagen. Protection of mice was also related to higher apoptosis in DW10 mice as indicated by higher amounts of BclII in response to type II collagen. On the basis of our observations in HLA transgenic mice, we hypothesize that DRB1 polymorphism can modulate disease by shaping the T cell repertoire in thymus and select autoreactive T cells.
Expression of Activated Notch3 in Transgenic Mice Enhances Generation of T Regulatory Cells and Protects against Experimental Autoimmune Diabetes
Authors: Anastasi Emanuela , Campese Antonio F. , Bellavia Diana , Bulotta Angela , Balestri Anna , Pascucci Monica , Checquolo Saula , Gradini Roberto , Lendahl Urban , Frati Luigi , Gulino Alberto , Di Mario Umberto , Screpanti Isabella
Published: April 2014

Thymic-derived dysregulated tolerance has been suggested to occur in type 1 diabetes via impaired generation of CD4+CD25+ T regulatory cells, leading to autoimmune β cell destruction. In this study, we demonstrate that Notch3 expression is a characteristic feature of CD4+CD25+ cells. Furthermore, streptozotocin-induced autoimmune diabetes fails to develop in transgenic mice carrying the constitutively active intracellular domain of Notch3 in thymocytes and T cells. The failure to develop the disease is associated with an increase of CD4+CD25+ T regulatory cells, accumulating in lymphoid organs, in pancreas infiltrates and paralleled by increased expression of IL-4 and IL-10. Accordingly, CD4+ T cells from Notch3-transgenic mice inhibit the development of hyperglycemia and insulitis when injected into streptozotocin-treated wild-type mice and display in vitro suppressive activity. These observations, therefore, suggest that Notch3-mediated events regulate the expansion and function of T regulatory cells, leading to protection from experimental autoimmune diabetes and identify the Notch pathway as a potential target for therapeutic intervention in type 1 diabetes.