bluuebunny/crossref_metadata_2025 huggingface dataset:
Distinct Sequences in the Cytoplasmic Domain of Complement Receptor 2 Are Involved in Antigen Internalization and Presentation
Authors: Barrault Denise V. , Knight Andrew M.
Published: April 2014

B cells express randomly rearranged surface Ig that forms part of a multiprotein complex known as the B cell receptor (BCR). Recognition of Ag via this receptor results in its capture, internalization, proteolysis and presentation to CD4+ T cells. The recognition of Ag by CD4+ T cells is critical for the selection of individual B cells, leading to the eventual secretion of a high affinity version of the BCR as an effective circulating Ab. B cells also express other receptors that recognize Ags associated with components of innate immunity. One of these receptors, CR2, binds Ags coated with activated complement components. Studies have shown that cross-linking CR2 and the BCR with complement-tagged Ags leads to enhanced Ag presentation by B cells. In addition, Ags targeted to B cell CR2 in the absence of BCR coligation are also efficiently presented to T cells. In this report, we identify several distinct sequences within the cytoplasmic domain of mouse CR2 (mCR2) that are essential for mCR2-mediated Ag presentation in both the presence and the absence of BCR cross-linking. The finding that distinct sequences in the cytoplasmic domain of mCR2 are essential for BCR-independent Ag presentation leads us to propose a novel role for CR2.
Carcinoembryonic Antigen-Related Cellular Adhesion Molecule 1 Isoforms Alternatively Inhibit and Costimulate Human T Cell Function
Authors: Chen Daohong , Iijima Hideki , Nagaishi Takashi , Nakajima Atsushi , Russell Sara , Raychowdhury Raktima , Morales Victor , Rudd Christopher E. , Utku Nalan , Blumberg Richard S.
Published: April 2014

Carcinoembryonic Ag-related cellular adhesion molecule 1 (CEACAM1) represents a group of transmembrane protein isoforms that consist of variable numbers of extracellular Ig-like domains together with either a long cytoplasmic (cyt) tail containing two immunoreceptor tyrosine-based inhibitory motifs or a unique short cyt tail. Although CEACAM1 has been reported to be expressed on the surface of T lymphocytes upon activation, its roles in T cell regulation are controversial due to the lack of functional characterization of each individual CEACAM1 isoform. We thus cotransfected Jurkat T cells with CEACAM1 isoform-encoding constructs and an IL-2 promoter-bearing plasmid or a small interference RNA targeting src homology domain 2 containing phosphatase 1. In a luciferase reporter assay and through measurements of cytokine secretion (IL-2, IL-4, and IFN-γ), CEACAM1 containing either a long or a short cyt tail inhibited or costimulated, respectively, TCR/CD3 complex plus CD28 mediated activation with the inhibitory functions of the long cyt tail dominating. The inhibitory function of CEACAM1, was dependent upon src homology domain 2 containing phosphatase 1 activity, required both tyrosine residues within the immunoreceptor tyrosine-based inhibitory motif domains of the cyt tail and was mediated through the mitogen-activated protein kinase pathway. CEACAM1-mediated inhibition could be functionally reconstituted by incubation of PBMC with either a CEACAM1-specific mAb or CEACAM1-Fc fusion protein in the presence of an allogeneic or mitogenic stimulus, respectively. These studies indicate that the long and short cyt tails of CEACAM1 serve as inhibitory and costimulatory receptors, respectively, in T cell regulation.
Heme Oxygenase-1 Modulates the Expression of Adhesion Molecules Associated with Endothelial Cell Activation
Authors: Soares Miguel P. , Seldon Mark P. , Gregoire Isabel Pombo , Vassilevskaia Tatiana , Berberat Pascal O. , Yu Jia , Tsui Tung-Yu , Bach Fritz H.
Published: April 2014

Heme oxygenase-1 (HO-1) cleaves the porphyrin ring of heme into carbon monoxide, Fe2+, and biliverdin, which is then converted into bilirubin. Heme-derived Fe2+ induces the expression of the iron-sequestering protein ferritin and activates the ATPase Fe2+-secreting pump, which decrease intracellular free Fe2+ content. Based on the antioxidant effect of bilirubin and that of decreased free cellular Fe2+, we questioned whether HO-1 would modulate the expression of proinflammatory genes associated with endothelial cell (EC) activation. We tested this hypothesis specifically for the genes E-selectin (CD62), ICAM-1 (CD54), and VCAM-1 (CD106). We found that HO-1 overexpression in EC inhibited TNF-α-mediated E-selectin and VCAM-1, but not ICAM-1 expression, as tested at the RNA and protein level. Heme-driven HO-1 expression had similar effects to those of overexpressed HO-1. In addition, HO-1 inhibited the activation of NF-κB, a transcription factor required for TNF-α-mediated up-regulation of these genes in EC. Bilirubin and/or Fe2+ chelation mimicked the effects of HO-1, whereas biliverdin or carbon monoxide did not. In conclusion, HO-1 inhibits the expression of proinflammatory genes associated with EC activation via a mechanism that is associated with the inhibition of NF-κB activation. This effect of HO-1 is mediated by bilirubin and/or by a decrease of free intracellular Fe2+ but probably not by biliverdin or carbon monoxide.
Distinct Roles for the OX40-OX40 Ligand Interaction in Regulatory and Nonregulatory T Cells
Authors: Takeda Ikuo , Ine Shoji , Killeen Nigel , Ndhlovu Lishomwa C. , Murata Kazuko , Satomi Susumu , Sugamura Kazuo , Ishii Naoto
Published: April 2014

The OX40 (CD134) molecule is induced primarily during T cell activation and, as we show in this study, is also expressed on CD25+CD4+ regulatory T (Treg) cells. A necessary role for OX40 in the development and homeostasis of Treg cells can be inferred from the reduced numbers of the cells present in the spleens of OX40-deficient mice, and their elevated numbers in the spleens of mice that overexpress the OX40 ligand (OX40L). The homeostatic proliferation of Treg cells following transfer into lymphopenic mice was also found to be potentiated by the OX40-OX40L interaction. Suppression of T cell responses by Treg cells was significantly impaired in the absence of OX40, indicating that, in addition to its homeostatic functions, OX40 contributes to efficient Treg-mediated suppression. However, despite this, we found that CD25−CD4+ T cells became insensitive to Treg-mediated suppression when they were exposed to OX40L-expressing cells, or when they were treated with an agonistic OX40-specific mAb. OX40 signaling could also abrogate the disease-preventing activity of Treg cells in an experimental model of inflammatory bowel disease. Thus, although the data reveal important roles for OX40 signaling in Treg cell development, homeostasis, and suppressive activity, they also show that OX40 signals can oppose Treg-mediated suppression when they are delivered directly to Ag-engaged naive T cells.
Glycoprotein 170 Induces Platelet-Activating Factor Receptor Membrane Expression and Confers Tumor Cell Hypersensitivity to NK-Dependent Cell Lysis
Authors: Geromin Daniela , Bourge Jean-François , Soulié Annie , Pawliuk Rob , Fleet Christina , Michel Eugene , Denizot Yves , Berthou Christian , Leboulch Philippe , Sigaux François , Sasportes Marilyne
Published: April 2014

Multidrug resistance (MDR) confers resistance to anticancer drugs and reduces therapeutic efficiency. It is often characterized by the expression of the MDR1 gene product P-glycoprotein (or gp170) at the membrane of tumor cells. To further propose a potential complementary tool in cancer treatment, the sensitivity of gp170 tumor cells to NK-dependent lysis was investigated. Two kinds of cells were generated from wild-type K562 erythroleukemic cells: the first were derived from Taxol-selected cells and cloned, whereas the second were retrovirally transduced by the cDNA of the MDR1 gene. The last process was also applied to the human embryonal carcinoma cells called Tera-2 cells. First, both cloned and MDR-1 K562 cells appeared highly susceptible to naive NK cell killing. Interestingly, in addition, Tera-2 cells that were not sensitive to NK lysis could be killed when they expressed gp170 at their membranes. In previous data, we demonstrated that NK cell release of bimolecular complexes composed of perforin and platelet-activating factor (PAF) interacting with the PAF-R, which has to be expressed on the target cell membranes, were components of NK tumor cell killing. In the present study, we show that gp170 has the capacity to drive constitutive PAF-R expression on tumor cells, which could be responsible for hypersensitivity to NK lysis and accelerated cell death.
The β2-Microglobulin Locus of Rainbow Trout (Oncorhynchus mykiss) Contains Three Polymorphic Genes
Authors: Magor Katharine E. , Shum Benny P. , Parham Peter
Published: April 2014

β2-microglobulin (β2m) associates with MHC and related class I H chains to form cell surface glycoproteins that mediate a variety of functions in defense. In humans, monomorphism of a single β2m gene contrasts with the diversity and polymorphism of the class I H chain genes, and a similar picture was seen in almost all other species examined. In this regard, rainbow trout (Oncorhynchus mykiss) appeared unusual: trout β2m genes gave a complicated and polymorphic pattern in Southern blots, and a minimum of 10 different mRNA encoding two distinct types of β2m were expressed by a single fish. Characterization of genomic clones from the same fish now shows that the rainbow trout β2m locus consists of two expressed genes and one partial gene that are closely linked. Four copies of the locus were identified and allelic variants of each gene defined, largely through comparison of the noncoding regions. A dramatic variation in the lengths of introns is caused by variable repetitive elements and accounts for the complex pattern seen in Southern blots. By comparison to noncoding sequences, the coding regions are conserved but the three loci differ within a cluster of codons that encode residues of β2m that do not interact with class I H chains. Additional diversity in the trout β2m genes appears to be due to somatic mutation that might be facilitated by the abundance of repetitive DNA elements within the 12 β2m genes of an individual rainbow trout.
Architectural Changes in the TCR:CD3 Complex Induced by MHC:Peptide Ligation
Authors: La Gruta Nicole L. , Liu Haiyan , Dilioglou Smaroula , Rhodes Michele , Wiest David L. , Vignali Dario A. A.
Published: April 2014

A hallmark of T cell activation is the ligation-induced down-modulation of the TCR:CD3 complex. However, little is known about the molecular events that drive this process. The CD3 ζ-chain has been shown to play a unique role in regulating the assembly, transport, and cell surface expression of the TCR:CD3 complex. In this study we have investigated the relationship between CD3ζ and the TCRαβCD3εδγ complex after ligation by MHC:peptide complexes. Our results show that there is a significant increase in free surface CD3ζ, which is not associated with the TCR:CD3 complex, after T cell stimulation. This may reflect dissociation of CD3ζ from the TCRαβCD3εδγ complex or transport of intracellular CD3ζ directly to the cell surface. We also show that MHC:peptide ligation also results in exposure of the TCR-associated CD3ζ NH2 terminus, which is ordinarily buried in the complex. These observations appears to be dependent on Src family protein tyrosine kinases, which are known to be critical for efficient T cell activation. These data suggest a mechanism by which ligated TCR may be differentiated from unligated TCR and selectively down-modulated.
A Disintegrin and Metalloproteinase 10-Mediated Cleavage and Shedding Regulates the Cell Surface Expression of CXC Chemokine Ligand 16
Authors: Gough Peter J. , Garton Kyle J. , Wille Paul T. , Rychlewski Marcin , Dempsey Peter J. , Raines Elaine W.
Published: April 2014

CXC chemokine ligand (CXCL)16 and scavenger receptor for phosphatidylserine and oxidized low-density lipoprotein were independently identified as a chemokine and a scavenger receptor, respectively, but have since been shown to be identical. CXCL16 is synthesized as a transmembrane protein with its chemokine domain at the end of a mucin-rich stalk. When expressed at the cell surface, CXCL16 functions as a scavenger receptor, binding and internalizing oxidized low-density lipoprotein and bacteria. As a soluble form, CXCL16 is a chemoattractant for activated CD4+ and CD8+ T cells through binding its receptor, CXCR6. In this study, we examined the mechanisms that regulate the conversion between these two functionally distinct forms of CXCL16. We demonstrate that murine CXCL16 is synthesized as an intracellular precursor that is rapidly transported to the cell surface where it undergoes metalloproteinase-dependent cleavage, causing the release of a fragment that constitutes the majority of the CXCL16 extracellular domain. Using a novel retroviral system for the generation of short interfering RNAs, we show that knockdown of a disintegrin and metalloproteinase (ADAM) family protease ADAM10 decreases this constitutive shedding of CXCL16. Furthermore, we show that overexpression of ADAM10 increases CXCL16 shedding, whereas overexpression of a dominant-negative form of ADAM10 lowers shedding of CXCL16 in a similar manner to short interfering RNAs. Through the modulation of ADAM10 function, we demonstrate that ADAM10-mediated constitutive shedding is a key regulator of CXCL16 cell surface expression. The identification of ADAM10 as a major protease responsible for the conversion of CXCL16 from a membrane-bound scavenger receptor to a soluble chemoattractant will provide new information for understanding the physiological function of this molecule.
Production of IL-12 by Macrophages Infected withToxoplasma gondiiDepends on the Parasite Genotype
Authors: Robben Paul M. , Mordue Dana G. , Truscott Steven M. , Takeda Kiyoshi , Akira Shizuo , Sibley L. David
Published: April 2014

Three clonal strain types (I, II, and III) of Toxoplasma gondii predominate worldwide. The outcome of infection in mice is highly dependent on the parasite genotype with type I strains being uniformly virulent, while types II and III are nonvirulent. Interactions with the innate immune response play a major role in determining the outcome of infection in the murine model. To identify key early differences in the innate immune response that contribute to pathogenesis, we examined the cytokine production of macrophages after in vitro infection with parasites of virulent type I and nonvirulent type II genotypes. Infection with type II strain parasites stimulated the production of proinflammatory cytokines, and particularly high levels of the Th1-polarizing cytokine, IL-12. Infection with type II strain parasites stimulated NF-κB nuclear translocation at early time points and led to the up-regulation of mRNA levels of IL-12 and other proinflammatory cytokines that was dependent on the myeloid differentiation factor 88 signaling pathway. Induction of IL-12 required active invasion by live parasites and was not blocked by infection with virulent type I strain parasites, arguing against an active inhibition of signaling. Our findings suggest that early induction of high levels of IL-12 by macrophages infected with type II strain parasites may contribute to more effective control.
T Cell-Intrinsic Expression of c-Rel Regulates Th1 Cell Responses Essential for Resistance toToxoplasma gondii
Authors: Mason Nicola J. , Liou Hsiou-Chi , Hunter Christopher A.
Published: April 2014

The ability of many microbial and inflammatory stimuli to activate members of the Rel/NF-κB family of transcription factors is associated with the regulation of innate and adaptive responses required to control infection. Individual family members play distinct roles during different infectious and inflammatory responses. For example, c-Rel is essential for the production of IL-12 in response to LPS, but dispensable for IL-12 production in response to Toxoplasma Ag. To assess the role of c-Rel during immunity to the intracellular pathogen Toxoplasma gondii, wild-type (WT) and c-Rel−/− mice were infected with Toxoplasma and the immune response was analyzed. c-Rel−/− mice developed severe toxoplasmic encephalitis with increased numbers of parasites compared with WT controls and succumbed to infection within 5–8 wk. Although increased susceptibility of c-Rel−/− mice was associated with decreased T cell activation, proliferation, and production of IFN-γ, these mice were able to generate Th1 effector cells that were present in the brain during chronic infection. In vitro mixing studies using WT and c-Rel−/− dendritic cells and WT and c-Rel−/− TCR transgenic T cells indicated that c-Rel−/− dendritic cells are defective in their ability to stimulate T cell responses. However, when c-Rel−/− T cells were transferred into T cell-deficient hosts, early defects in T cell activation, proliferation, and IFN-γ production persisted, and these mice remained susceptible to infection. Together, these studies indicate that although c-Rel is an important regulator of innate immune responses, it also plays an important role in optimization and maintenance of adaptive T cell responses during infection.
Concomitant Helper Response Rescues Otherwise Low Avidity CD8+ Memory CTLs to Become Efficient Effectors In Vivo
Authors: Kumaraguru Udayasankar , Suvas Susmit , Biswas Partha S. , Azkur Ahmet Kursat , Rouse Barry T.
Published: April 2014

This report seeks a means of maximizing memory CD8 T cell responses to peptide immunization. Delivery of the CD8 peptide epitope by stress protein, heat shock protein (hsp)70, results in excellent immunogenicity at the acute phase but memory responses were poor both in terms of the number of responding cells as well as their functional avidity. We demonstrate for the first time that hsp70 can also be used as a vehicle to achieve CD4 T cell responses to loaded peptide epitopes and that coimmunization with hsp70 loaded with both CD8 and CD4 peptide epitopes may increase memory up to 3-fold. Furthermore, CD8+ T cell memory responses were of higher avidity measured both by in vitro cytotoxicity assays and a new methodology that measures the avidity of CTL activity in vivo in mice. Our results emphasize that peptide immunization remains a viable approach to induce long-term CD8+ T cell function, providing steps are taken to assure appropriate stimulation of Th cell responses.
Increased Dendritic Cell Numbers Impair Protective Immunity to Intracellular Bacteria Despite Augmenting Antigen-Specific CD8+ T Lymphocyte Responses
Authors: Alaniz Robert C. , Sandall Sharsti , Thomas Elaine K. , Wilson Christopher B.
Published: April 2014

Dendritic cells (DCs) reside in tissues, where they function as sentinels, providing an essential link between innate and adaptive immunity. Increasing the numbers of DCs in vivo augments T cell responses, and can cause dramatic CTL-dependent tumor regression. To determine whether greater DC numbers promoted T cell-mediated protection in the context of host defense against intracellular bacteria, we treated mice with Flt3 ligand (Flt3-L) to increase DCs in vivo and challenged them with Listeria monocytogenes. Unexpectedly, after primary challenge with Listeria, the overall control of Listeria infection was impaired in Flt3-L-treated mice, which had greater bacterial burden and mortality than controls. Similar results were obtained when DC numbers were increased by treatment with polyethylene glycol-conjugated GM-CSF rather than Flt3-L and in mice infected with Mycobacterium tuberculosis. Impaired protection was not due to dysfunctional T cell responses, as Flt3-L-treated mice had a greater frequency and absolute number of Ag-specific CD8+ T cells, which produced IFN-γ, exhibited cytolytic activity, and transferred protection. The increased Listeria burden in Flt3-L-treated mice was preferentially associated with DCs, which were unable to kill Listeria and more resistant to CTL lysis compared with macrophages in vitro. Although we cannot exclude the possibility that other potential effects, in addition to increased numbers of DCs, are shared by Flt3-L and polyethylene glycol-conjugated GM-CSF and contributed to the increase in susceptibility observed in treated mice, these results support the notion that DC numbers must be properly controlled within physiological limits to optimize host defense to intracellular bacterial pathogens.
Control of Simian/Human Immunodeficiency Virus Viremia and Disease Progression after IL-2-Augmented DNA-Modified Vaccinia Virus Ankara Nasal Vaccination in Nonhuman Primates
Authors: Bertley Frederic M. N. , Kozlowski Pamela A. , Wang Shainn-Wei , Chappelle Joseph , Patel Jignesh , Sonuyi Oluwakemi , Mazzara Gail , Montefiori David , Carville Angela , Mansfield Keith G. , Aldovini Anna
Published: April 2014

A successful HIV vaccine may need to stimulate antiviral immunity in mucosal and systemic immune compartments, because HIV transmission occurs predominantly at mucosal sites. We report here the results of a combined DNA-modified vaccinia virus Ankara (MVA) vaccine approach that stimulated simian/human immunodeficiency virus (SHIV)-specific immune responses by vaccination at the nasal mucosa. Fifteen male rhesus macaques, divided into three groups, received three nasal vaccinations on day 1, wk 9, and wk 25 with a SHIV DNA plasmid producing noninfectious viral particles (group 1), or SHIV DNA plus IL-2/Ig DNA (group 2), or SHIV DNA plus IL-12 DNA (group 3). On wk 33, all macaques were boosted with rMVA expressing SIV Gag-Pol and HIV Env 89.6P, administered nasally. Humoral responses were evaluated by measuring SHIV-specific IgG and neutralizing Abs in plasma, and SHIV-specific IgA in rectal secretions. Cellular responses were monitored by evaluating blood-derived virus-specific IFN-γ-secreting cells and TNF-α-expressing CD8+ T cells, and blood- and rectally derived p11C tetramer-positive T cells. Many of the vaccinated animals developed both mucosal and systemic humoral and cell-mediated anti-SHIV immune responses, although the responses were not homogenous among animals in the different groups. After rectal challenge of vaccinated and naive animals with SHIV89.6P, all animals became infected. However a subset, including all group 2 animals, were protected from CD4+ T cell loss and AIDS development. Taken together, these data indicate that nasal vaccination with SHIV-DNA plus IL-2/Ig DNA and rMVA can provide significant protection from disease progression.
The Human Cationic Peptide LL-37 Induces Activation of the Extracellular Signal-Regulated Kinase and p38 Kinase Pathways in Primary Human Monocytes
Authors: Bowdish Dawn M. E. , Davidson Donald J. , Speert David P. , Hancock Robert E. W.
Published: April 2014

LL-37 is a cationic peptide that is found in the granules of neutrophils and is secreted by epithelial cells from a variety of tissues. Levels of LL-37 in vivo increase upon infection, and its production and secretion are increased upon stimulation with proinflammatory mediators. It has been postulated that LL-37 modulates the immune response by interacting with the effector cells of innate immunity; however, the mechanism of this interaction is unknown. LL-37 induced phosphorylation and activation of the mitogen-activated protein kinases, extracellular signal-regulated kinase 1/2 (ERK1/2) and p38, in human peripheral blood-derived monocytes and a human bronchial epithelial cell line, but not in B or T lymphocytes. Phosphorylation was not dependent on the G protein-coupled formyl peptide-like receptor 1, which was previously proposed to be the receptor for LL-37-induced chemotaxis on human monocytes and T cells. Activation of ERK1/2 and p38 was markedly increased by the presence of GM-CSF, but not M-CSF. Exposure to LL-37 also led to the activation of Elk-1, a transcription factor that is downstream of and activated by phosphorylated ERK1/2, the up-regulation of various Elk-1-controlled genes, and the transcription and secretion of IL-8. Inhibition of either p38 or ERK1/2 kinases led to a reduction in LL-37-induced IL-8 secretion and inhibition of the transcription of various chemokine genes. The ability of LL-37 to signal through these pathways has broad implications in immunity, monocyte activation, proliferation, and differentiation.
Cercarial Dermatitis Caused by Bird Schistosomes Comprises Both Immediate and Late Phase Cutaneous Hypersensitivity Reactions
Authors: Kouřilová Pavlína , Hogg Karen G. , Kolářová Libuše , Mountford Adrian P.
Published: April 2014

Avian schistosomes are the primary causative agent of cercarial dermatitis in humans, but despite its worldwide occurrence, little is known of the immune mechanism of this disease. Using a murine model, hosts were exposed to primary (1×) and multiple (4×) infections of Trichobilharzia regenti via the pinna. Penetration of larvae into the skin evoked immediate edema, thickening of the exposure site, and an influx of leukocytes, including neutrophils, macrophages, CD4+ lymphocytes, and mast cells. A large proportion of the latter were in the process of degranulating. After 1× infection, inflammation was accompanied by the release of IL-1β, IL-6, and IL-12p40. In contrast, in 4× reinfected animals the production of histamine, IL-4, and IL-10 was dramatically elevated within 1 h of infection. Analysis of Ag-stimulated lymphocytes from the skin-draining lymph nodes revealed that cells from 1× infected mice produced a mixed Th1/Th2 cytokine response, including abundant IFN-γ, whereas cells from 4× reinfected mice were Th2 polarized, dominated by IL-4 and IL-5. Serum Abs confirmed this polarization, with elevated levels of IgG1 and IgE after multiple infections. Infection with radiolabeled cercariae revealed that almost 90% of larvae remained in the skin, and the majority died within 8 days after infection, although parasites were cleared more rapidly in 4× reinfected mice. Our results are the first demonstration that cercarial dermatitis, caused by bird schistosomes, is characterized by an early type I hypersensitivity reaction and a late phase of cutaneous inflammation, both associated with a polarized Th2-type acquired immune response.
IL-4 and IL-13 Up-Regulate Intestinal Trefoil Factor Expression: Requirement for STAT6 and De Novo Protein Synthesis
Authors: Blanchard Carine , Durual Stéphane , Estienne Monique , Bouzakri Karim , Heim Markus H. , Blin Nikolaus , Cuber Jean-Claude
Published: April 2014

The development of intestinal goblet cell hyperplasia/hypertrophy during nematode infection involves the Th2 cytokines IL-4 and IL-13 via STAT6 activation. This is thought to play an important role in host protective immunity against the infection. In this study we demonstrate that IL-4 and IL-13 up-regulate the specific goblet cell product trefoil factor-3 (TFF3) from the mucus-producing HT-29 CL.16E and HT-29 cells selected by adaptation to methotrexate. Up-regulation of TFF3 mRNA and protein levels occurred in a time- and dose-dependent fashion and was accompanied by up-regulation of the goblet cell product mucin 2 (MUC2). Addition of actinomycin D before IL-4/IL-13 stimulation led to decreases in TFF3 mRNA levels similar to those observed in controls without IL-4/IL-13. Furthermore, IL-4-mediated increased TFF3 transcription required de novo protein synthesis. Stable transfection of HT-29 CL.16E cells with a truncated dominant-negative form of STAT6 produced a cell line that was unresponsive to IL-4/IL-13. Although only one consensus STAT6 binding site is contained in the TFF3 gene, located in the intron 1, it did not operate as an enhancer in the context of an SV40 promoter/luciferase construct. Thus, STAT6 activation mediates a transcriptional enhancement of TFF3 by induction of de novo synthesized protein in goblet cells.
Mannose-Binding Lectin Binds to Two Major Outer Membrane Proteins, Opacity Protein and Porin, ofNeisseria meningitidis
Authors: Estabrook Michele M. , Jack Dominic L. , Klein Nigel J. , Jarvis Gary A.
Published: April 2014

Human mannose-binding lectin (MBL) provides a first line of defense against microorganisms by complement activation and/or opsonization in the absence of specific Ab. This serum collectin has been shown to activate complement when bound to repeating sugar moieties on several microorganisms, including encapsulated serogroup B and C meningococci, which leads to increased bacterial killing. In the present study, we sought to identify the meningococcal cell surface components to which MBL bound and to characterize such binding. Outer membrane complex containing both lipooligosaccharide (LOS) and proteins and LOS from Neisseria meningitidis were examined for MBL binding by dot blot and ELISA. MBL bound outer membrane complex but not LOS. The binding to bacteria by whole-cell ELISA did not require calcium and was not inhibited by N-acetyl-glucosamine or mannose. With the use of SDS-PAGE, immunoblot analysis, and mAbs specific for meningococcal opacity (Opa) proteins and porin proteins, we determined that MBL bound to Opa and porin protein B (porB). The N-terminal amino acid sequences of the two MBL binding proteins confirmed Opa and PorB. Purified PorB inhibited the binding of MBL to meningococci. Escherichia coli with surface-expressed gonococcal Opa bound significantly more MBL than did the control strain. The binding of human factor H to purified PorB was markedly inhibited by MBL in a dose-dependent manner. Meningococci incubated with human serum bound MBL as detected by ELISA. We conclude that MBL binds to meningococci by a novel target recognition of two nonglycosylated outer membrane proteins, Opa and PorB.
Vaccination with Phosphoglycan-Deficient Leishmania major Protects Highly Susceptible Mice from Virulent Challenge without Inducing a Strong Th1 Response
Authors: Uzonna Jude E. , Späth Gerald F. , Beverley Stephen M. , Scott Phillip
Published: April 2014

Long-term immunity to Leishmania may require the continued presence of parasites, but previous attempts to create attenuated parasites that persist without causing disease have had limited success. Since Leishmania major mutants that lack lipophosphoglycan and other secreted phosphoglycans, termed lpg2−, persist indefinitely in infected mice without inducing any disease, we tested their ability to provide protection to virulent L. major challenge. In response to leishmanial Ag stimulation, cells from lpg2−-infected mice produced minimal levels of IL-4 and IL-10, as well as very low levels of IFN-γ. Nevertheless, when BALB/c mice infected with lpg2− parasites were challenged with virulent L. major they were protected from disease. Thus, these findings report on attenuated parasites that may be used to induce long-term protection against leishmaniasis and indicate that the immunity induced can be maintained in the absence of a strong Th1 response.
Streptococcal M5 Protein Prevents Neutrophil Phagocytosis by Interfering with CD11b/CD18 Receptor-Mediated Association and Signaling
Authors: Weineisen Maria , Sjöbring Ulf , Fällman Maria , Andersson Tommy
Published: April 2014

Group A streptococci (GAS) are common human pathogens that express major surface-associated virulence factors designated M proteins. In this study, we explored directly the cellular mechanisms behind their supposed ability to prevent phagocytosis. Isolated human neutrophils killed an M-negative GAS mutant (ΔM5), but not the wild-type parent strain (M5). After 3 h, 3–4 times as many ΔM5 as M5 bacteria were associated with the neutrophils, and more ΔM5 than M5 bacteria were ingested. However, there was no statistically significant difference between ΔM5 and M5 bacteria in regard to the percentage of the neutrophil-associated bacteria that were ingested, indicating that M5 protein prevents an adhesion receptor-dependent association with neutrophils and not the phagocytic machinery per se. Different Abs against CD11b/CD18 (CR3) blocked adhesion and killing of ΔM5 bacteria, whereas the blocking of two other complement receptors, CD11c/CD18 (CR4) and CD35 (CR1), did not. The CD11b/CD18-mediated killing of ΔM5 bacteria resulted in protein tyrosine phosphorylations and Cdc42 activation. Furthermore, inhibition of CD11b/CD18 receptor engagement or tyrosine kinase activity blocked the ΔM5-induced activation of Cdc42 as well as the killing of these bacteria. We conclude that M5 protein interferes with the CD11b/CD18-dependent association between GAS and neutrophils, and thereby blocks subsequent ingestion of the bacteria.
Diesel Exhaust Particles Suppress In Vivo IFN-γ Production by Inhibiting Cytokine Effects on NK and NKT Cells
Authors: Finkelman Fred D. , Yang Mingyan , Orekhova Tatyana , Clyne Erin , Bernstein Jonathan , Whitekus Michael , Diaz-Sanchez David , Morris Suzanne C.
Published: April 2014

Diesel exhaust particles (DEP) have strong, selective Th2 adjuvant activity when inhaled with conventional Ags. We used a novel technique for measuring in vivo cytokine production to investigate possible mechanisms by which DEP might promote a Th2 response. Injection of DEP i.p. stimulated IL-6 secretion, but failed to increase IL-4, IL-10, or TNF-α secretion, and decreased basal levels of IFN-γ. When injected with or before LPS, DEP had little effect on the LPS-induced TNF-α responses, but partially inhibited the LPS-induced IL-10 response and strongly inhibited the LPS-induced IFN-γ response. DEP also inhibited the IFN-γ responses to IL-12, IL-12 plus IL-18, IL-2, and poly(I · C). DEP treatment had little effect on the percentages of NK and NKT cells in the spleen, but inhibited LPS-induced IFN-γ production by splenic NK and NKT cells. In contrast, DEP failed to inhibit the IFN-γ response by anti-CD3 mAb-activated NKT cells. Taken together, these observations suggest that DEP inhibit Toll-like receptor ligand-induced IFN-γ responses by interfering with cytokine signaling pathways that stimulate NK and NKT cells to produce IFN-γ. Our observations also suggest that DEP may promote a Th2 response by stimulating production of inflammatory cytokines while simultaneously inhibiting production of IFN-γ, and raise the possibility that the same mechanisms contribute to the association between DEP exposure and asthma.
Decay-Accelerating Factor Deficiency Increases Susceptibility to Dextran Sulfate Sodium-Induced Colitis: Role for Complement in Inflammatory Bowel Disease
Authors: Lin Feng , Spencer David , Hatala Denise A. , Levine Alan D. , Medof M. Edward
Published: April 2014

Decay-accelerating factor (DAF or CD55) is expressed on colonic epithelial cells but its function in the mucosa is unknown. In humans, a proportion of DAF-deficient (Cromer INAB) patients develop inflammatory bowel disease (IBD). To evaluate how DAF deficiency may contribute to gut inflammation and thus could play a role in IBD pathogenesis, we compared the severity of dextran sulfate sodium-induced colitis in Daf1 gene-targeted and control mice. Seven days after consuming 3% dextran sulfate sodium in their drinking water, Daf1−/− mice suffered markedly greater weight loss (−24.7 ± 7.5% vs −14.2% ± 4.9%), exhibited uniformly bloody diarrhea as compared with soft stool in control mice, developed shortened colons, and had larger spleens. Histological examination of distal colons showed massively increased neutrophilic and mononuclear cell infiltration, greater epithelial cell destruction, and increased ulcerations. Cytokine production in organ cultures of colonic explants showed increased levels of IL-12 and IL-6. Fourteen days after switching back to regular water, in contrast to the Daf1+/+ controls which showed little stool abnormality, all Daf1−/− mice continued to have diarrhea. Organ culture cytokine measurements at this time point, i.e., the end of the recovery phase, showed markedly increased levels of IL-10 (6-fold), IL-12 (4-fold), and IL-6 (2-fold), as well as TNF-α (>10-fold) compared with the controls. Our findings argue that, as shown for IL-10 in IL-10−/− mice and IL-2 in IL-2−/− mice, DAF control of complement additionally is important in regulating gut homeostasis and consequently its activity may participate in protecting against IBD.
Human Thy-1 (CD90) on Activated Endothelial Cells Is a Counterreceptor for the Leukocyte Integrin Mac-1 (CD11b/CD18)
Authors: Wetzel Anne , Chavakis Triantafyllos , Preissner Klaus T. , Sticherling Michael , Haustein Uwe-Frithjof , Anderegg Ulf , Saalbach Anja
Published: April 2014

Leukocyte recruitment in response to inflammatory signals is in part governed by interactions between endothelial cell receptors belonging to the Ig superfamily and leukocyte integrins. In our previous work, the human Ig superfamily glycoprotein Thy-1 (CD90) was identified as an activation-associated cell adhesion molecule on human dermal microvascular endothelial cells. Furthermore, the interaction of Thy-1 with a corresponding ligand on monocytes and polymorphonuclear cells was shown to be involved in the adhesion of these leukocytes to activated Thy-1-expressing endothelial cells. In this study, we have identified the specific interaction between human Thy-1 and the leukocyte integrin Mac-1 (CD11b/CD18; αMβ2) both in cellular systems and in purified form. Monocytes and polymorphonuclear cells were shown to adhere to transfectants expressing human Thy-1 as well as to primary Thy-1-expressing human dermal microvascular endothelial cells. Furthermore, leukocyte adhesion to activated endothelium as well as the subsequent transendothelial migration was mediated by the interaction between Thy-1 and Mac-1. This additional pathway in leukocyte-endothelium interaction may play an important role in the regulation of leukocyte recruitment to sites of inflammation.
Expansion and Functional Relevance of High-Avidity Myelin-Specific CD4+ T Cells in Multiple Sclerosis
Authors: Bielekova Bibiana , Sung Myong-Hee , Kadom Nadja , Simon Richard , McFarland Henry , Martin Roland
Published: April 2014

Multiple sclerosis (MS) is an autoimmune disease in which myelin-specific T cells are believed to play a crucial pathogenic role. Nevertheless, so far it has been extremely difficult to demonstrate differences in T cell reactivity to myelin Ag between MS patients and controls. We believe that by using unphysiologically high Ag concentrations previous studies have missed a highly relevant aspect of autoimmune responses, i.e., T cells recognizing Ag with high functional avidity. Therefore, we focused on the characterization of high-avidity myelin-specific CD4+ T cells in a large cohort of MS patients and controls that was matched demographically and with respect to expression of MHC class II alleles. We demonstrated that their frequency is significantly higher in MS patients while the numbers of control T cells specific for influenza hemagglutinin are virtually identical between the two cohorts; that high-avidity T cells are enriched for previously in vivo-activated cells and are significantly skewed toward a proinflammatory phenotype. Moreover, the immunodominant epitopes that were most discriminatory between MS patients and controls differed from those described previously and were clearly biased toward epitopes with lower predicted binding affinities to HLA-DR molecules, pointing at the importance of thymic selection for the generation of the autoimmune T cell repertoire. Correlations between selected immunological parameters and magnetic resonance imaging markers indicate that the specificity and function of these cells influences phenotypic disease expression. These data have important implications for autoimmunity research and should be considered in the development of Ag-specific therapies in MS.
Targeted Bioactivity of Membrane-Anchored TNF by an Antibody-Derived TNF Fusion Protein
Authors: Bauer Stefan , Adrian Nicole , Williamson Barbara , Panousis Con , Fadle Natalie , Smerd Joanna , Fettah Ilknur , Scott Andrew M. , Pfreundschuh Michael , Renner Christoph
Published: April 2014

We describe the generation and characterization of a fusion protein consisting of a humanized anti-fibroblast-activating protein (anti-FAP) Ab and human TNF replacing the IgG1 CH2/CH3 Fc domain. The construct was generated by recombinant DNA technology and preserved its IgG1-derived dimeric structure with the TNF molecule linked as a dimer. Expression in CHO cells was optimized in serum-free medium under GMP conditions to achieve production levels up to 15 mg/liter. Recognition of the FAP Ag by the construct was as good as that by the parental anti-FAP Ab. TNF signaling was induce able via both TNF receptor types. When acting in solution, the Ab-linked TNF dimer exhibited a 10- to 20-fold lower activity compared with recombinant trimeric TNF. However, after binding to FAP-expressing cells, immobilized anti-FAP-TNF dimer was equivalent to membrane-anchored TNF with regard to bioactivity. Amplification of TNF-related pathways by mimicking the membrane-integrated TNF signaling was detectable in various systems, such as apoptosis induction or tissue factor production. The difference in TNF receptor type 1 and 2 signaling by the anti-FAP-TNF construct correlated well with its Ag-bound or -soluble status. Translating the approach into a xenograft animal model (BALB/c nu/nu mice), we demonstrated low toxicity with measurable antitumor efficacy for the TNF fusion protein after i.v. application. Immunohistochemical analysis of tumor sections showed restricted TNF-mediated macrophage recruitment to the targeted tissue in a time- and dose-dependent manner. These data warrant transfer of the anti-FAP-TNF immunocytokine into clinical trials for the treatment of FAP-positive tumors.
Immune Defects in 28-kDa Proteasome Activator γ-Deficient Mice
Authors: Barton Lance F. , Runnels Herbert A. , Schell Todd D. , Cho Yunjung , Gibbons Reta , Tevethia Satvir S. , Deepe George S. , Monaco John J.
Published: April 2014

Protein complexes of the 28-kDa proteasome activator (PA28) family activate the proteasome and may alter proteasome cleavage specificity. Initial investigations have demonstrated a role for the IFN-γ-inducible PA28α/β complex in Ag processing. Although the noninducible and predominantly nuclear PA28γ complex has been implicated in affecting proteasome-dependent signaling pathways, such as control of the mitotic cell cycle, there is no previous evidence demonstrating a role for this structure in Ag processing. We therefore generated PA28γ-deficient mice and investigated their immune function. PA28γ−/− mice display a slight reduction in CD8+ T cell numbers and do not effectively clear a pulmonary fungal infection. However, T cell responses in two viral infection models appear normal in both magnitude and the hierarchy of antigenic epitopes recognized. We conclude that PA28γ−/− mice, like PA28α−/−/β−/− mice, are deficient in the processing of only specific Ags.
IL-2, Regulatory T Cells, and Tolerance
Authors: Nelson Brad H.
Published: April 2014

IL-2 is a potent T cell growth factor that for many years was assumed to amplify lymphocyte responses in vivo. Accordingly, IL-2 has been used clinically to enhance T cell immunity in patients with AIDS or cancer, and blocking Abs to the IL-2R are used to inhibit T cell responses against transplanted tissues. It was later shown in mice that, unexpectedly, disruption of the IL-2 pathway results in lymphoid hyperplasia and autoimmunity rather than immune deficiency, indicating that the major physiological function of IL-2 is to limit rather than enhance T cell responses. This apparent paradox has recently been resolved with the discovery that IL-2 is critical for the development and peripheral expansion of CD4+CD25+ regulatory T cells, which promote self-tolerance by suppressing T cell responses in vivo. Our new understanding of IL-2 biology prompts a re-evaluation of how best to clinically manipulate this important immunoregulatory pathway.
Cutting Edge: Innate Immune System Discriminates between RNA Containing Bacterial versus Eukaryotic Structural Features That Prime for High-Level IL-12 Secretion by Dendritic Cells
Authors: Koski Gary K. , Karikó Katalin , Xu Shuwen , Weissman Drew , Cohen Peter A. , Czerniecki Brian J.
Published: April 2014

RNA derived from bacterial but not eukaryotic sources, when transfected into human monocyte-derived dendritic cell precursors, induces high-level IL-12 secretion in conjunction with dendritic cell maturation stimuli. In vitro-transcribed mRNA that mimics the structure of bacterial mRNA in the lack of a long 3′-poly(A) tail likewise induces IL-12 secretion, but this property is lost upon efficient enzymatic 3′-polyadenylation. Among other tested RNAs, only polyuridylic acid induced IL-12 p70. This RNA response phenomenon appears biologically distinct from the classically defined response to dsRNA. RNA-transfected APC also polarize T cells in an IL-12-dependent manner toward the IFN-γhighIL-5 low Th1 phenotype, suggesting a link between the detection of appropriately structured RNA and the skewing of immune responses toward those best suited for controlling intracellular microbes. RNA structured to emulate bacterial patterns constitutes a novel vaccine strategy to engender polarized Th1-type immune responses.
CCR7 Directs the Migration of Thymocytes into the Thymic Medulla
Authors: Kwan Joanne , Killeen Nigel
Published: April 2014

Developing thymocytes migrate from the cortex to the medulla of the thymus as a consequence of positive selection. This migration is likely to be essential for tolerance because it allows the developing cells to move into an environment that is optimal for negative selection. Guidance mechanisms that draw positively selected thymocytes into the medulla have not been clarified, but several studies have implicated chemokines in the process. CCR7, the receptor for the medullary chemokines CCL19 and CCL21, is induced on thymocytes during their positive selection. In this study we show that premature expression of CCR7 repositions CD4+CD8+ double-positive cells into the medulla of transgenic mice. This repositioning of the thymocytes is accompanied by impairment of their development. The data show the involvement of CCR7 in medullary migration and emphasize the importance of proper thymocyte positioning for efficient T cell development.
Siva-1 and an Alternative Splice Form Lacking the Death Domain, Siva-2, Similarly Induce Apoptosis in T Lymphocytes via a Caspase-Dependent Mitochondrial Pathway
Authors: Py Bénédicte , Slomianny Christian , Auberger Patrick , Petit Patrice X. , Benichou Serge
Published: April 2014

Siva-1 is a death domain-containing proapoptotic protein identified as an intracellular ligand of CD27 and of the glucocorticoid-induced TNFR family-related gene, which are two members of the TNFR family expressed on lymphoid cells. Although Siva-1 expression is up-regulated in multiple pathological processes, little is known about the signaling pathway underlying the Siva-induced apoptosis. In this study, we investigated the mechanism of the proapoptotic activity of Siva-1 and an alternative splice form lacking the death domain of Siva-1, Siva-2, in T lymphocytes in which Siva proteins, CD27, and glucocorticoid-induced TNFR family-related gene are primarily expressed. Overexpression of Siva proteins triggers a typical apoptotic process manifested by cell shrinkage and surface exposure of phosphatidylserine, and confirmed by ultrastructural features. Siva-induced apoptosis is related to the CD27-mediated apoptotic pathway and results in activation of both initiator and effector caspases. This pathway involves a mitochondrial step evidenced by activation of Bid and cytochrome c release, and is modulated by overexpression of Bcl-2 or Bcl-xL. The determinants for Siva-induced apoptosis are not contained within the death domain found in the central part of Siva-1, but rather in both the N-terminal and C-terminal regions shared by both Siva proteins. The N-terminal region also participates in the translocation of both Siva proteins into the nuclear compartment. These results indicate that Siva-1 and Siva-2 mediate apoptosis in T lymphocytes via a caspase-dependent mitochondrial pathway that likely involves both cytoplasmic and nuclear events.