bluuebunny/crossref_metadata_2025 huggingface dataset:
The Molecular Basis for the Lack of Immunostimulatory Activity of Vertebrate DNA
Authors: Stacey Katryn J. , Young Greg R. , Clark Francis , Sester David P. , Roberts Tara L. , Naik Shalin , Sweet Matthew J. , Hume David A.
Published: April 2014

Macrophages and B cells are activated by unmethylated CpG-containing sequences in bacterial DNA. The lack of activity of self DNA has generally been attributed to CpG suppression and methylation, although the role of methylation is in doubt. The frequency of CpG in the mouse genome is 12.5% of Escherichia coli, with unmethylated CpG occurring at ∼3% the frequency of E. coli. This suppression of CpG alone is insufficient to explain the inactivity of self DNA; vertebrate DNA was inactive at 100 μg/ml, 3000 times the concentration at which E. coli DNA activity was observed. We sought to resolve why self DNA does not activate macrophages. Known active CpG motifs occurred in the mouse genome at 18% of random occurrence, similar to general CpG suppression. To examine the contribution of methylation, genomic DNAs were PCR amplified. Removal of methylation from the mouse genome revealed activity that was 23-fold lower than E. coli DNA, although there is only a 7-fold lower frequency of known active CpG motifs in the mouse genome. This discrepancy may be explained by G-rich sequences such as GGAGGGG, which potently inhibited activation and are found in greater frequency in the mouse than the E. coli genome. In summary, general CpG suppression, CpG methylation, inhibitory motifs, and saturable DNA uptake combined to explain the inactivity of self DNA. The immunostimulatory activity of DNA is determined by the frequency of unmethylated stimulatory sequences within an individual DNA strand and the ratio of stimulatory to inhibitory sequences.
More Is Not Necessarily Better: Prozone-Like Effects in Passive Immunization with IgG
Authors: Taborda Carlos P. , Rivera Johanna , Zaragoza Oscar , Casadevall Arturo
Published: April 2014

Despite a century of study, the relationship between Ag-specific Ig concentration and protection remains poorly understood for the majority of pathogens. In certain conditions, administration of high Ab doses before challenge with an infectious agent can be less effective than smaller Ab doses, a phenomenon which is consistent with a prozone-like effect. In this study, the relationship between IgG1, IgG2a, IgG2b, and IgG3 dose, infective inocula, and protection was investigated in a mouse model of Cryptococcus neoformans infection. The activity of each IgG subclass ranged from protective to disease-enhancing depending on both the Ab dose and infective inocula used. Enhanced dissemination to the brain was observed in mice given a high IgG2a dose and a relatively low inoculum. Ab administration had immunomodulatory effects, with cytokine expression in lung, brain, and spleen varying as a function of the infective inoculum Ab dose and IgG subclass. In vitro studies did not predict or explain the mechanism of in vivo prozone-like effects, because all isotypes were opsonic and elicited NO release from macrophages. IgG2a was most efficient in inducing a macrophage oxidative burst. These results reveal that an individual Ab can be protective, nonprotective, or disease-enhancing depending on its concentration relative to a challenge inoculum. Our findings have implications for the potential contribution of Ab responses to defense against microbial diseases because Ab-mediated immunity may be protective, nonprotective, or even deleterious to the host.
Galectin-9 Induces Apoptosis Through the Calcium-Calpain-Caspase-1 Pathway
Authors: Kashio Yumiko , Nakamura Kazuhiro , Abedin Mohammad J. , Seki Masako , Nishi Nozomu , Yoshida Naoko , Nakamura Takanori , Hirashima Mitsuomi
Published: April 2014

Galectin-9 (Gal-9) induced the apoptosis of not only T cell lines but also of other types of cell lines in a dose- and time-dependent manner. The apoptosis was suppressed by lactose, but not by sucrose, indicating that β-galactoside binding is essential for Gal-9-induced apoptosis. Moreover, Gal-9 required at least 60 min of Gal-9 binding and possibly de novo protein synthesis to mediate the apoptosis. We also assessed the apoptosis of peripheral blood T cells by Gal-9. Apoptosis was induced in both activated CD4+ and CD8+ T cells, but the former were more susceptible than the latter. A pan-caspase inhibitor (Z-VAD-FMK) inhibited Gal-9-induced apoptosis. Furthermore, a caspase-1 inhibitor (Z-YVAD-FMK), but not others such as Z-IETD-FMK (caspase-8 inhibitor), Z-LEHD-FMK (caspase-9 inhibitor), and Z-AEVD-FMK (caspase-10 inhibitor), inhibited Gal-9-induced apoptosis. We also found that a calpain inhibitor (Z-LLY-FMK) suppresses Gal-9-induced apoptosis, that Gal-9 induces calcium (Ca2+) influx, and that either the intracellular Ca2+ chelator BAPTA-AM or an inositol trisphosphate inhibitor 2-aminoethoxydiphenyl borate inhibits Gal-9-induced apoptosis. These results suggest that Gal-9 induces apoptosis via the Ca2+-calpain-caspase-1 pathway, and that Gal-9 plays a role in immunomodulation of T cell-mediated immune responses.
B7-H1 (Programmed Death-1 Ligand) on Dendritic Cells Is Involved in the Induction and Maintenance of T Cell Anergy
Authors: Selenko-Gebauer Nicole , Majdic Otto , Szekeres Andreas , Höfler Gerald , Guthann Elisabeth , Korthäuer Ulf , Zlabinger Gerhard , Steinberger Peter , Pickl Winfried F. , Stockinger Hannes , Knapp Walter , Stöckl Johannes
Published: April 2014

In an effort to identify immunoregulatory molecules on dendritic cells (DC), we generated and screened for mAbs capable of modulating the T cell stimulatory function of DC. A particularly interesting mAb was mAb DF272. It recognizes monocyte-derived DC, but not blood monocytes or lymphocytes, and has profound immunomodulatory effects on DC. Treatment of DC with intact IgG or Fab of mAb DF272 enhanced their T cell stimulatory capacity. This effect on DC was accompanied by neither an up-regulation of costimulatory molecules such as B7.1 (CD80), B7.2 (CD86), and MHC class II molecules nor by an induction of cytokine production, including IL-1, TNF-α, IL-10, and IL-12. Moreover, the well-established inhibitory function of IL-10-treated DC could be reverted with mAb DF272. Even T cells, anergized because of stimulation with IL-10-treated DC, could be reactivated and induced to proliferate upon stimulation with mAb DF272-treated DC. Furthermore, mAb DF272-treated DC favored the induction of a type-1 cytokine response in T cells and inhibited IL-10 production. By using a retrovirus-based cDNA expression library generated from DC, we cloned and sequenced the mAb DF272-defined cell surface receptor and could demonstrate that it is identical with B7-H1 (programmed death-1 ligand), a recently identified new member of the B7 family of costimulatory molecules. Our results thus demonstrate that the mAb DF272-defined surface molecule B7-H1 represents a unique receptor structure on DC that might play a role in the induction and maintenance of T cell anergy.
TGFβ1 Inhibits Ca2+-Calcineurin-Mediated Activation in Thymocytes
Authors: Bommireddy Ramireddy , Ormsby Ilona , Yin Moying , Boivin Gregory P. , Babcock George F. , Doetschman Thomas
Published: April 2014

TGFβ1 is a polypeptide growth modulatory and differentiation factor involved in many biological processes including immune homeostasis and self-tolerance. Tgfb1 knockout mice die around weaning age due to severe inflammation in most major organ systems, but the mechanism underlying this disease is not understood. In this study we demonstrate that Tgfb1−/− CD4+CD8+ and CD4+CD8− thymocytes are hyperresponsive to receptor-mediated and receptor-independent mitogenic stimulation. A suboptimal concentration of ionomycin in the presence of PMA fully activates Tgfb1−/− thymocytes, whereas the inhibitors of Ca2+ influx and calcineurin, EGTA and FK506, eliminate the hyperresponsiveness. Hence, the hypersensitivity of Tgfb1−/− thymocytes is due to a lowered threshold for Ca2+-dependent activation. Further, we demonstrate that the hypersensitivity of thymocytes results from the absence of TGFβ1 and not from the inflammatory environment because the thymocytes are hyperresponsive in preinflammatory-stage Tgfb1−/− mice. Our results suggest for the first time that TGFβ1 functions to inhibit aberrant T cell expansion by maintaining intracellular calcium concentration levels low enough to prevent a mitogenic response by Ca2+-independent stimulatory pathways alone. Consequently, TGFβ1 prevents autoimmune disease through a Ca2+ regulatory pathway that maintains the activation threshold above that inducible by self-MHC-TCR interactions.
SS-A/Ro52, an Autoantigen Involved in CD28-Mediated IL-2 Production
Authors: Ishii Tomonori , Ohnuma Kei , Murakami Akikazu , Takasawa Naruhiko , Yamochi Tadanori , Iwata Satoshi , Uchiyama Masahiko , Dang Nam H. , Tanaka Hirotoshi , Morimoto Chikao
Published: April 2014

An autoantibody against SS-A/Ro52 (Ro52) is most frequently found in the sera of patients with Sjögren’s syndrome, systemic lupus erythematosus, and congenital heart block from anti-Ro52 Ab-positive mother. However, the physiological function of the autoantigen SS-A/Ro52 has not yet been elucidated. In this study, we describe the role of Ro52 protein in T cell activation. Overexpression of SS-A/Ro52 in Jurkat T cell resulted in enhanced IL-2 production following CD28 stimulation. Furthermore, transfection of anti-Ro52-specific small RNA duplexes partially blocked the expression of native and overexpressed Ro52 in Jurkat T cell, resulting in decreased IL-2 production via CD28 pathway in these cells. Finally, intracellular localization of Ro52 dramatically changed following CD28 stimulation. Our data reveal a novel function of Ro52 in CD28-mediated pathway, which eventually contributes to cytokine production and expression of the T cell biological programs.
Sphingosine-1-Phosphate Receptor Agonism Impairs the Efficiency of the Local Immune Response by Altering Trafficking of Naive and Antigen-Activated CD4+ T Cells
Authors: Xie Jenny H. , Nomura Naomi , Koprak Sam L. , Quackenbush Elizabeth J. , Forrest Michael J. , Rosen Hugh
Published: April 2014

FTY720 (2-amino-[2-(4-octylphenyl) ethyl]-1,3-propanediol hydrochloride) is an immunosuppressive agent that inhibits allograft rejection. We recently demonstrated that FTY-phosphate, the active metabolite of FTY720, acts as a full agonist for sphingosine-1-phosphate (S1P) receptors. Furthermore, activation of S1P receptors with their natural ligand, S1P, as well as pharmacological ligands leads to lymphopenia, probably due to sequestration of lymphocytes in secondary lymphoid organs. In the present study we used a local Ag-challenged mouse model to examine the effects of FTY720 on T cell activation in the draining lymph node (DLN) and on the release of activated T cells to the peripheral blood compartment. We showed that the number of Ag-activated CD4+ T cells in the DLN after injection of Ag and CFA into a footpad was dramatically reduced after FTY720 treatment. However, T cell proliferation, both in vitro and in vivo, was not impaired by FTY720. Our results suggest that the reduced efficiency of T cell responses in the DLN in response to a local Ag is probably due to a defective recirculation of naive T cells caused by FTY720 treatment. Furthermore, we found that the numbers of naive and Ag-activated CD4+ T cells in the peripheral blood of Ag-challenged mice were equally reduced with FTY720 treatment, suggesting that both T cell subsets are sequestered in the DLNs. Thus, FTY720 induces immunosuppression through inhibition of both the recirculation of naive T cells and the release of Ag-activated T cells from the DLN to lymph and to the blood compartment.
B Cell Complement Receptor 2 Transfer Reaction
Authors: Lindorfer Margaret A. , Jinivizian Hasmig B. , Foley Patricia L. , Kennedy Adam D. , Solga Michael D. , Taylor Ronald P.
Published: April 2014

The B cell C receptor specific for C3dg (CR2) shares a number of features with the primate E C receptor (CR1). Previously, we have demonstrated, both in vitro and in animal models, that immune complexes (IC) bound to primate E CR1, either via C opsonization or by means of bispecific mAb complexes, can be transferred to acceptor macrophages in a process that also removes CR1 from the E. We have now extended this paradigm, the transfer reaction, to include B cell CR2. We used both flow cytometry and fluorescence microscopy to demonstrate that IC bound to Raji cell CR2, either via C opsonization or through the use of an anti-CR2 mAb, are transferred to acceptor THP-1 cells. This reaction, which appears to require Fc recognition of IgG bound to Raji cell CR2, also leads to transfer of CR2. Additional support for the B cell transfer reaction is provided in a prototype study in a monkey model in which IC bound to B cell CR2 are localized to the spleen. These findings may have important implications with respect to defining the role of C in IC handling during the normal immune response.
The Possible Role of TGF-β-Induced Suppressors of Cytokine Signaling Expression in Osteoclast/Macrophage Lineage Commitment In Vitro
Authors: Fox Simon W. , Haque S. Jaharul , Lovibond Alison C. , Chambers Timothy J.
Published: April 2014

Osteoclast formation is dependent on the ability of TGF-β to enable receptor activator of NF-κB ligand (RANKL)-induced commitment of hemopoietic precursors to the osteoclastic lineage. The mechanism by which TGF-β enables formation is unknown. One possibility is that TGF-β opposes Janus kinase (JAK)/STAT signals generated by inhibitory cytokines such as IFN-β. The JAK/STAT pathway is activated by cytokines that induce resistance to osteoclast formation, such as IFN-γ and M-CSF, and the effect of these is opposed by TGF-β. Recently, a group of STAT-induced factors, termed suppressors of cytokine signaling (SOCS), has been identified that inhibit JAK/STAT signals. Therefore, we tested the ability of TGF-β to induce SOCS expression in osteoclast precursors and examined the effect of SOCS expression on osteoclast/macrophage lineage commitment. We found that while SOCS mRNA is undetectable in macrophages, osteoclasts express SOCS-3, and TGF-β up-regulates this expression. Furthermore, TGF-β rapidly induces sustained SOCS-3 expression in macrophage/osteoclast precursors. To determine whether SOCS-3 plays a role in osteoclast differentiation we expressed SOCS-3 in precursors using a retroviral system. We found that osteoclast differentiation was significantly enhanced in SOCS-3-infected precursors, and SOCS-3 expression enables formation in the presence of anti-TGF-β Ab. On the other hand, antisense knockdown of SOCS-3 strongly suppressed osteoclast formation and significantly blunted the response to TGF-β. Moreover, like TGF-β, SOCS-3 expression opposed the inhibitory effect of IFN-β. These data suggest that TGF-β-induced expression of SOCS-3 may represent a mechanism by which TGF-β suppresses inhibitory cytokine signaling, priming precursors for a role in bone resorption.
Lipopolysaccharide Promotes the Survival of Osteoclasts Via Toll-Like Receptor 4, but Cytokine Production of Osteoclasts in Response to Lipopolysaccharide Is Different from That of Macrophages
Authors: Itoh Kanami , Udagawa Nobuyuki , Kobayashi Kanichiro , Suda Koji , Li Xiaotong , Takami Masamichi , Okahashi Nobuo , Nishihara Tatsuji , Takahashi Naoyuki
Published: April 2014

Lipopolysaccharide is a pathogen that causes inflammatory bone loss. Monocytes and macrophages produce proinflammatory cytokines such as IL-1, TNF-α, and IL-6 in response to LPS. We examined the effects of LPS on the function of osteoclasts formed in vitro in comparison with its effect on bone marrow macrophages, osteoclast precursors. Both osteoclasts and bone marrow macrophages expressed mRNA of Toll-like receptor 4 (TLR4) and CD14, components of the LPS receptor system. LPS induced rapid degradation of I-κB in osteoclasts, and stimulated the survival of osteoclasts. LPS failed to support the survival of osteoclasts derived from C3H/HeJ mice, which possess a missense mutation in the TLR4 gene. The LPS-promoted survival of osteoclasts was not mediated by any of the cytokines known to prolong the survival of osteoclasts, such as IL-1β, TNF-α, and receptor activator of NF-κB ligand. LPS stimulated the production of proinflammatory cytokines such as IL-1β, TNF-α, and IL-6 in bone marrow macrophages and peritoneal macrophages, but not in osteoclasts. These results indicate that osteoclasts respond to LPS through TLR4, but the characteristics of osteoclasts are quite different from those of their precursors, macrophages, in terms of proinflammatory cytokine production in response to LPS.
Conservation of Nonpeptide Antigen Recognition by Rhesus Monkey Vγ2Vδ2 T Cells
Authors: Wang Hong , Lee Hoi K. , Bukowski Jack F. , Li Hongmin , Mariuzza Roy A. , Chen Zheng W. , Nam Ki-Hoan , Morita Craig T.
Published: April 2014

We have previously found that monkey Vγ2Vδ2+ T cells mount adaptive immune responses in response to Mycobacterium bovis bacillus Calmette-Guérin infections. We have now analyzed rhesus monkey γδ T cell responses to nonpeptide Ags and superantigens. Like human Vγ2Vδ2+ T cells, rhesus monkey γδ T cells are stimulated when exposed to prenyl pyrophosphate, bisphosphonate, and alkylamine Ags. Responsiveness was limited to γδ T cells expressing Vγ2Vδ2 TCRs. Rhesus monkey Vγ2Vδ2+ T cells also responded to the superantigen, staphyloccocal enterotoxin A. Sequencing of the rhesus monkey Vγ2Vδ2 TCR revealed a strong sequence homology to human Vγ2Vδ2 TCR that preserves important sequence motifs. Moreover, chimeric TCRs that pair human Vγ2 with monkey Vδ2 and monkey Vγ2 with human Vδ2 retain reactivity to nonpeptide Ags and B cell lymphomas. A molecular model of the rhesus monkey Vγ2Vδ2 TCR has a basic region in the complementarity-determining region 3 binding groove that is similar to that seen in the human Vγ2Vδ2 TCR and preserves the topology of the complementarity-determining region loops. Thus, recognition of nonpeptide prenyl pyrophosphate, bisphosphonate, and alkylamine Ags is conserved in primates suggesting that primates can provide an animal model for human γδ T cell Ag responses.
ATM Is Not Required in Somatic Hypermutation of VH, but Is Involved in the Introduction of Mutations in the Switch μ Region
Authors: Pan-Hammarström Qiang , Dai Shujing , Zhao Yaofeng , van Dijk-Härd Iris F. , Gatti Richard A. , Børresen-Dale Anne-Lise , Hammarström Lennart
Published: April 2014

Class switch recombination (CSR) and somatic hypermutation (SHM) are mechanistically related processes that share common key factors such as activation-induced cytidine deaminase. We have previously shown a role for ATM (mutated in ataxia-telangiectasia) in CSR. In this paper we show that the frequency, distribution, and nature of base pair substitutions in the Ig variable (V) heavy chain genes in ataxia-telangiectasia patients are largely similar to those in normal donors, suggesting a normal SHM process. Characterization of the third complementarity-determining region in B cells from ataxia-telangiectasia patients also shows a normal V(D)J recombination process. SHM-like mutations could be identified in the switch (S) μ region (up to several hundred base pairs upstream of the Sμ-Sα breakpoints) in normal in vivo switched human B cells. In the absence of ATM, mutations can still be found in this region, but at less than half the frequency of that in normal donors. The latter mutations are mainly due to transitions (86% compared with 58% in controls) and are biased to A or T nucleotides. An ATM-dependent mechanism, different from that generating SHM in V genes, is therefore likely to be involved in introducing SHM-like mutations in the S region. ATM may thus be one of the factors that is not shared by the CSR and SHM processes.
Transactivation of gp130 in Myeloma Cells
Authors: French Jena D. , Walters Denise K. , Jelinek Diane F.
Published: April 2014

Receptor transactivation, i.e., interaction between unrelated receptor systems, is a growing theme in cytokine and growth factor signaling. In this study we reveal for the first time the ability of IFN-α to transactivate gp130 in myeloma cells. An epidermal growth factor receptor/gp130 chimeric receptor previously shown by us to transactivate endogenous gp130, provided a complementary tool to study the underlying mechanisms of receptor cross-talk. Further analysis revealed that transactivation of gp130 by IFN-α did not require the extracellular or trans-membrane domain of gp130. Moreover, transactivation of gp130 was critically dependent upon Janus kinase activation by the initiating receptor and correlated with rapid and sustained Janus kinase 1 and tyrosine kinase (Tyk) 2 tyrosine phosphorylation. Finally, transactivation of gp130 may be a common theme in myeloma cells, perhaps providing a mechanism for enhanced or qualitatively distinct cellular responses to specific stimuli.
c-Rel Is Required for Chromatin Remodeling Across the IL-2 Gene Promoter
Authors: Rao Sudha , Gerondakis Steve , Woltring Donna , Shannon M. Frances
Published: April 2014

IL-2 gene transcription occurs in an activation-dependent manner in T cells responding to TCR and CD28 activation. One of the critical events leading to increased IL-2 transcription is an alteration in chromatin structure across the 300-bp promoter region of the gene. We initially showed that IL-2 gene transcription in CD4+ primary T cells is dependent on the NF-κB family member, c-Rel, but not RelA. We found that c-Rel is essential for global changes in chromatin structure across the 300-bp IL-2 promoter in response to CD3/CD28 in primary CD4+ T cells, but not in response to pharmacological signals, paralleling the requirement for c-Rel in IL-2 mRNA and protein accumulation. Interestingly, measurement of activation-induced localized accessibility changes using restriction enzyme digestion revealed that accessibility close to the c-Rel binding site in the CD28RR region of the promoter is specifically dependent on c-Rel. In contrast, restriction enzyme sites located at a distance from the CD28RR behave independently of c-Rel. These results suggest a nonredundant role for c-Rel in generating a correctly remodeled chromatin state across the IL-2 promoter and imply that the strength of the signal determines the requirement for c-Rel.
Regulation of the Human FcεRI α-Chain Distal Promoter
Authors: Hasegawa Masanari , Nishiyama Chiharu , Nishiyama Makoto , Akizawa Yushiro , Takahashi Kyoko , Ito Tomonobu , Furukawa Susumu , Ra Chisei , Okumura Ko , Ogawa Hideoki
Published: April 2014

The α-chain of the high affinity receptor for IgE (FcεRI) is essential for cell surface expression of FcεRI and binding of the IgE Ab. The human α-chain gene possesses two promoters: the proximal promoter, which is highly conserved with that of rodent; and the distal promoter, the structure and role of which are largely unknown. Transcriptional regulation of the α-chain distal promoter was investigated in this study. Transient reporter assay revealed critical region for transcription activity located within −27/−17. EMSA identified Elf-1, YY1, and PU.1 as transcription factors binding to this region. In contrast to the proximal promoter, which was trans-activated by YY1 and PU.1, these transcription factors exhibited repressive function on this promoter. Addition of IL-4 caused a marked increase in transcription from the distal promoter and subsequently increased the intracellular production of the α-chain. These results indicate that IL-4-dependent up-regulation of the human α-chain was due to enhancement of distal promoter activity and suggests that the two promoters have different regulatory mechanisms for α-chain expression.
A New Model of Sheep Ig Diversification: Shifting the Emphasis Toward Combinatorial Mechanisms and Away from Hypermutation
Authors: Jenne Craig N. , Kennedy Laurie J. , McCullagh Peter , Reynolds John D.
Published: April 2014

The current model of Ig repertoire development in sheep focuses on the rearrangement of a small number (∼20) of Vλ gene segments. It is believed that this limited combinatorial repertoire is then further diversified through postrearrangement somatic hypermutation. This process has been reported to introduce as many as 110 mutations/1000 nucleotides. In contrast, our data have that indicated somatic hypermutation may diversify the preimmune repertoire to a much lesser extent. We have identified 64 new Vλ gene segments within the rearranged Ig repertoire. As a result, many of the unique nucleotide patterns thought to be the product of somatic hypermutation are actually hard-coded within the germline. We suggest that combinatorial rearrangement makes a much larger contribution, and somatic hypermutation makes a much smaller contribution to the generation of diversity within the sheep Ig repertoire than is currently acknowledged.
DM Loss in k Haplotype Mice Reveals Isotype-Specific Chaperone Requirements
Authors: Koonce Chad H. , Wutz Gordana , Robertson Elizabeth J. , Vogt Anne B. , Kropshofer Harald , Bikoff Elizabeth K.
Published: April 2014

DM actions as a class II chaperone promote capture of diverse peptides inside the endocytic compartment(s). DM mutant cells studied to date express class II bound by class II-associated invariant chain-derived peptide (CLIP), a short proteolytic fragment of the invariant chain, and exhibit defective peptide-loading abilities. To evaluate DM functional contributions in k haplotype mice, we engineered a novel mutation at the DMa locus via embryonic stem cell technology. The present experiments demonstrate short-lived Ak/CLIP complexes, decreased Ak surface expression, and enhanced Ak peptide binding activities. Thus, we conclude that DM loss in k haplotype mice creates a substantial pool of empty or loosely occupied Ak conformers. On the other hand, the mutation hardly affects Ek activities. The appearance of mature compact Ek dimers, near normal surface expression, and efficient Ag presentation capabilities strengthen the evidence for isotype-specific DM requirements. In contrast to DM mutants described previously, partial occupancy by wild-type ligands is sufficient to eliminate antiself reactivity. Mass spectrometry profiles reveal Ak/CLIP and a heterogeneous collection of relatively short peptides bound to Ek molecules. These experiments demonstrate that DM has distinct roles depending on its specific class II partners.
Actin Tyrosine Dephosphorylation by the Src Homology 1-Containing Protein Tyrosine Phosphatase Is Essential for Actin Depolymerization After Membrane IgM Cross-Linking
Authors: Baba Takeshi , Fusaki Noemi , Shinya Nobuko , Iwamatsu Akihiro , Hozumi Nobumichi
Published: April 2014

Src homology protein 1 (SHP-1) plays an important role in B cell Ag receptor (BCR) differentiation, proliferation, survival, and apoptosis. After BCR stimulation in apoptotic cells, SHP-1 has been shown to be recruited to phosphorylated immunoreceptor tyrosine-based inhibitory motifs present in receptors such as CD22 and CD72. However, the substrates of SHP-1 in the chicken B cell line, DT40, have remained undefined. To identify SHP-1 substrates in DT40, we used a trapping mutant, SHP-1 C/S (a catalytically inactive form). Cross-linking of BCR induced hyperphosphorylation of ∼44-kDa protein in C/S transfectants. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis revealed that this was actin (cytoplasmic type 5) carrying three immunoreceptor tyrosine-based inhibitory motif-like sequences. SHP-1 was shown to bind to one of these sequences in synthetic peptide binding experiment. Thus, actin is a direct SHP-1 substrate. Furthermore, more SHP-1 molecules translocate into lipid rafts, and their association with actin was increased after BCR stimulation. In C/S transfectants, actin polymerization induced by membrane IgM ligation was sustained to a greater extent for a longer time compared with wild-type transfectants. Therefore, actin dephosphorylation by SHP-1 is essential for actin depolymerization after BCR stimulation. Our data suggest that SHP-1 plays a pivotal role in reorganization of cytoskeletal architecture inducing actin dephosphorylation. These results clearly demonstrate the direct interaction of SHP-1 with actin.
Investigation of Early Events in FcεRI-Mediated Signaling Using a Detailed Mathematical Model
Authors: Faeder James R. , Hlavacek William S. , Reischl Ilona , Blinov Michael L. , Metzger Henry , Redondo Antonio , Wofsy Carla , Goldstein Byron
Published: April 2014

Aggregation of FcεRI on mast cells and basophils leads to autophosphorylation and increased activity of the cytosolic protein tyrosine kinase Syk. We investigated the roles of the Src kinase Lyn, the immunoreceptor tyrosine-based activation motifs (ITAMs) on the β and γ subunits of FcεRI, and Syk itself in the activation of Syk. Our approach was to build a detailed mathematical model of reactions involving FcεRI, Lyn, Syk, and a bivalent ligand that aggregates FcεRI. We applied the model to experiments in which covalently cross-linked IgE dimers stimulate rat basophilic leukemia cells. The model makes it possible to test the consistency of mechanistic assumptions with data that alone provide limited mechanistic insight. For example, the model helps sort out mechanisms that jointly control dephosphorylation of receptor subunits. In addition, interpreted in the context of the model, experimentally observed differences between the β- and γ-chains with respect to levels of phosphorylation and rates of dephosphorylation indicate that most cellular Syk, but only a small fraction of Lyn, is available to interact with receptors. We also show that although the β ITAM acts to amplify signaling in experimental systems where its role has been investigated, there are conditions under which the β ITAM will act as an inhibitor.
Depletion of Neutrophils in IL-10−/− Mice Delays Clearance of Gastric Helicobacter Infection and Decreases the Th1 Immune Response to Helicobacter
Authors: Ismail Hanan F. , Fick Pamela , Zhang Juan , Lynch Richard G. , Berg Daniel J.
Published: April 2014

Gastric infection with Helicobacter induces a lymphocyte-rich mucosal inflammation that contains a minor population of neutrophilic granulocytes. The function of neutrophils in the local immune response to gastric Helicobacter infection remains unknown. To investigate this issue, we conducted experiments in neutrophil-depleted control wild-type (wt) and IL-10−/− mice infected with Helicobacter felis by gastric lavage. Infection of wt mice elicited a mild, focal gastritis and a Helicobacter-specific Th1 immune response. In wt mice Helicobacter colonization of the stomach was persistent and progressively increased during the 29 days of observation. Infection of IL-10−/− mice with H. felis elicited a severe chronic gastritis and a greatly enhanced Helicobacter-specific Th1 immune response, as compared with wt mice. After initial colonization, the IL-0−/− mice completely cleared Helicobacter from the stomach by day 8. The gastric inflammation in wt and IL-10−/− mice contained modest numbers of neutrophils. The intensity of gastric inflammation and the extent of Helicobacter colonization were similar in control and in neutrophil-depleted wt mice. In contrast, neutrophil depletion of Helicobacter-infected IL-10−/− mice decreased the severity of gastritis, modulated the Helicobacter-specific Th1 immune response, and delayed the clearance of bacteria from the stomach. These studies identify a role for neutrophils in the local and systemic immune response to gastric Helicobacter in IL-10−/− mice.
The Hypervariable Region of Anaplasma marginale Major Surface Protein 2 (MSP2) Contains Multiple Immunodominant CD4+ T Lymphocyte Epitopes That Elicit Variant-Specific Proliferative and IFN-γ Responses in MSP2 Vaccinates
Authors: Brown Wendy C. , Brayton Kelly A. , Styer Cathryn M. , Palmer Guy H.
Published: April 2014

Major surface protein 2 (MSP2) is an immunodominant outer membrane protein of Anaplasma marginale and Anaplasma phagocytophilum pathogens that cause bovine anaplasmosis and human granulocytic ehrlichiosis, respectively. MSP2 has a central hypervariable region (HVR) flanked by highly conserved amino and carboxyl termini. During A. marginale infection, dynamic and extensive amino acid sequence variation in MSP2 occurs through recombination of msp2 pseudogenes into the msp2 expression site, followed by sequential segmental gene conversions to generate additional variants. We hypothesized that MSP2 variation leads to significant changes in Th cell recognition of epitopes in the HVR. T cell epitopes were mapped using T cells from native MSP2-immunized cattle and overlapping peptides spanning the most abundant of five different MSP2 HVRs in the immunogen. Several epitopes elicited potent effector/memory Th cell proliferative and IFN-γ responses, including those in three discreet blocks of sequence that undergo segmental gene conversion. Th cell clones specific for an epitope in the block 1 region of the predominant MSP2 variant type failed to respond to naturally occurring variants. However, some of these variants were recognized by oligoclonal T cell lines from MSP2 vaccinates, indicating that the variant sequences contain immunogenic CD4+ T cell epitopes. In competition/antagonism assays, the nonstimulatory variants were not inhibitory for CD4+ T cells specific for the agonist peptide. Dynamic amino acid sequence variation in MSP2 results in escape from recognition by some effector/memory MSP2-specific Th cells. Antigenic variation in MSP2 Th cell and B cell epitopes may contribute to immune evasion that allows long-term persistence of A. marginale in the mammalian reservoir.
A Common Mucosal Chemokine (Mucosae-Associated Epithelial Chemokine/CCL28) Selectively Attracts IgA Plasmablasts
Authors: Lazarus Nicole H. , Kunkel Eric J. , Johnston Brent , Wilson Eric , Youngman Kenneth R. , Butcher Eugene C.
Published: April 2014

IgA immunoblasts can seed both intestinal and nonintestinal mucosal sites following localized mucosal immunization, an observation that has led to the concept of a common mucosal immune system. In this study, we demonstrate that the mucosae-associated epithelial chemokine, MEC (CCL28), which is expressed by epithelia in diverse mucosal tissues, is selectively chemotactic for IgA Ab-secreting cells (ASC): MEC attracts IgA- but not IgG- or IgM-producing ASC from both intestinal and nonintestinal lymphoid and effector tissues, including the intestines, lungs, and lymph nodes draining the bronchopulmonary tree and oral cavity. In contrast, the small intestinal chemokine, TECK (CCL25), attracts an overlapping subpopulation of IgA ASC concentrated in the small intestines and its draining lymphoid tissues. Surprisingly, T cells from mucosal sites fail to respond to MEC. These findings suggest a broad and unifying role for MEC in the physiology of the mucosal IgA immune system.
Tumor-Derived TGF-β Reduces the Efficacy of Dendritic Cell/Tumor Fusion Vaccine
Authors: Kao John Y. , Gong Yusong , Chen Chuan-Min , Zheng Qiong-Duan , Chen Jian-Jun
Published: April 2014

Dendritic cell (DC)-based antitumor vaccine is a novel cancer immunotherapy that is promising for reducing cancer-related mortality. However, results from early clinical trials were suboptimal. A possible explanation is that many tumors secrete immunosuppressive factors such as TGF-β, which may hamper host immune response to DC vaccine. In this study, we demonstrated that TGF-β produced by tumors significantly reduced the potency of DC/tumor fusion vaccines. TGF-β-secreting (CT26-TGF-β) stable mouse colon cancer cell lines were generated using a retroviral vector expressing TGF-β. A non-TGF-β-secreting (CT26-neo) cell line was generated using an empty retroviral vector. The efficacies of DC/tumor fusion vaccines were assessed in vitro and in vivo. DC/CT26-TGF-β fusion cells failed to induce a strong T cell proliferative response in vitro, mainly due to the effect of TGF-β on T cell responsiveness rather than DC stimulatory capability. Animals vaccinated with DC/CT26-TGF-β fusion vaccine had lower tumor-specific CTL activity and had significantly lower survival after tumor challenge as compared with animals immunized with DC/CT26-neo hybrids (45 vs 77%, p < 0.05). Ex vivo exposure of DCs to TGF-β did not appear to lessen the efficacy of DC vaccine. These data suggest that tumor-derived TGF-β reduces the efficacy of DC/tumor fusion vaccine via an in vivo mechanism. Neutralization of TGF-β produced by the fusion cells may enhance the effectiveness of DC-based immunotherapy.
A Role for Triggering Receptor Expressed on Myeloid Cells-1 in Host Defense During the Early-Induced and Adaptive Phases of the Immune Response
Authors: Bleharski Joshua R. , Kiessler Viviane , Buonsanti Cecilia , Sieling Peter A. , Stenger Steffen , Colonna Marco , Modlin Robert L.
Published: April 2014

Triggering receptor expressed on myeloid cells (TREM)-1 is a cell surface molecule expressed on neutrophils and monocytes implicated in the propagation of the inflammatory response. To further characterize the function of this molecule in different phases of the immune response, we examined TREM-1 in the context of host defense against microbial pathogens. In primary human monocytes TREM-1 activation did not trigger innate antimicrobial pathways directed against intracellular Mycobacterium tuberculosis, and only minimally improved phagocytosis. However, activation of TREM-1 on monocytes did drive robust production of proinflammatory chemokines such as macrophage inflammatory protein-1α and IL-8. Engagement of TREM-1 in combination with microbial ligands that activate Toll-like receptors also synergistically increased production of the proinflammatory cytokines TNF-α and GM-CSF, while inhibiting production of IL-10, an anti-inflammatory cytokine. Expression of TREM-1 was up-regulated in response to TLR activation, an effect further enhanced by GM-CSF and TNF-α but inhibited by IL-10. Functionally, primary monocytes differentiated into immature dendritic cells following activation through TREM-1, evidenced by higher expression of CD1a, CD86, and MHC class II molecules. These cells had an improved ability to elicit T cell proliferation and production of IFN-γ. Our data suggest that activation of TREM-1 on monocytes participates during the early-induced and adaptive immune responses involved in host defense against microbial challenges.
The Resolution of Relapsing Fever Borreliosis Requires IgM and Is Concurrent with Expansion of B1b Lymphocytes
Authors: Alugupalli Kishore R. , Gerstein Rachel M. , Chen Jianzhu , Szomolanyi-Tsuda Eva , Woodland Robert T. , Leong John M.
Published: April 2014

The rate of pathogen clearance is a critical determinant of morbidity and mortality. We sought to characterize the immune response responsible for the remarkably rapid clearance of individual episodes of bacteremia caused by the relapsing fever bacterium, Borrelia hermsii. SCID or Rag−/− mice were incapable of resolving B. hermsii infection, indicating a critical role for T and/or B cells. TCR−/− mice, which lack T cells, and IL-7−/− mice, which are deficient in both T cells and follicular B cells, but not in B1 cells and splenic marginal zone (MZ) B cells, efficiently cleared B. hermsii. These findings suggested that B1 cells and/or MZ B cells, two B cell subsets that are known to participate in rapid, T-independent responses, might be involved. The efficient resolution of the episodes of moderate level bacteremia by splenectomized mice suggested that MZ B cells do not play the primary role in clearance of this bacterium. In contrast, xid mice, which are deficient in B1 cells, suffered more severe episodes of bacteremia than wild-type mice. The hypothesis that B1 cells are critical for clearance of B. hermsii was further supported by a selective expansion of the B1b (i.e., IgMhigh, IgD−/low, Mac1+ CD23−, and CD5−) cell subset in infected xid mice, which coincided with the eventual resolution of infection. Finally, mice selectively incapable of secreting IgM, the dominant isotype produced by B1 cells, were completely unable to clear B. hermsii. Together these results support the model that B1b cells generate the T-independent IgM required for the control and resolution of relapsing fever borreliosis.
Differential γ-Herpesvirus Distribution in Distinct Anatomical Locations and Cell Subsets During Persistent Infection in Mice
Authors: Flaño Emilio , Kim In-Jeong , Moore John , Woodland David L. , Blackman Marcia A.
Published: April 2014

Murine γ-herpesvirus 68 (MHV-68) provides an important experimental model for analyzing γ-herpesvirus latent infection. After intranasal infection with MHV-68, we analyzed the distribution of the virus in different anatomical locations and purified populations of cells. Our data show that long-term latency is maintained in a variety of anatomical locations and cell populations with different frequencies. Importantly, we demonstrate that although latency in the lung is established in a variety of cell subsets, long-term latency in the lung is only maintained in B cells. In contrast, splenic latency is maintained in macrophages and dendritic cells, as well as in B cells. In blood, isotype-switched B cells constitute the major viral reservoir. These results show that the cell subsets in which latency is established vary within different anatomical sites. Finally, we demonstrate that long-term latency is accompanied by a low level of infectious virus in lung and spleen. These data have important implications for understanding the establishment and maintenance of latency by γ2-herpesviruses.
IL-4 Exacerbates Anaphylaxis
Authors: Strait Richard T. , Morris Suzanne C. , Smiley Kristi , Urban Joseph F. , Finkelman Fred D.
Published: April 2014

We evaluated whether IL-4, a cytokine critical for inducing allergic responses, also contributes to the effector phase of allergy. Pretreatment of mice with IL-4 or the related cytokine, IL-13, rapidly and dramatically increased the severity of anaphylaxis induced by cross-linking FcεRI or FcγRIII. This effect was inhibited by endogenously produced IFN-γ, was T cell-, B cell-, and common γ-chain-independent, and required IL-4Rα and Stat6. IL-4Rα signaling also enhanced anaphylaxis in mice infected with a nematode parasite that stimulates IL-4/IL-13 production. IL-4 exacerbated anaphylaxis by acting synergistically with vasoactive mediators to increase vascular permeability. Synergy between IL-4 and vasoactive mediators during the effector phase of allergic inflammation may both contribute to allergic immunopathology and enhance protective immunity against gastrointestinal worms.
Unique Regulation of CCL18 Production by Maturing Dendritic Cells
Authors: Vulcano Marisa , Struyf Sofie , Scapini Patrizia , Cassatella Marco , Bernasconi Sergio , Bonecchi Raffaella , Calleri Angelica , Penna Giuseppe , Adorini Luciano , Luini Walter , Mantovani Alberto , Van Damme Jo , Sozzani Silvano
Published: April 2014

Dendritic cells (DC) orchestrate the trafficking of lymphocytes by secreting chemokines with different specificity and function. Chemokines are produced at higher levels by mature DC. This study shows that CCL18 is one of the most abundant chemokines produced by immature DC. In contrast to all other chemokines investigated to date, CCL18 was selectively down-regulated during the maturation process induced by LPS, TNF, CD40 ligand, Staphylococcus aureus Cowan I, Candida albicans, and influenza virus. IL-10 and vitamin D3, two known inhibitors of DC differentiation and function, strongly promoted CCL18 secretion, whereas IFN-γ, a costimulator of DC function, inhibited its production. IL-10 also induced CCL18 secretion in blood myeloid DC. No CCL18 secretion was observed in blood plasmacytoid DC. The opposite pattern of regulation was observed for CCL20, a prototypic inflammatory chemokine. CCL18 was found to be a chemotactic factor for immature DC. Therefore, CCL18 may act as a chemotactic signal that promotes the colocalization of immature DC with naive T lymphocytes in an IL-10-dominated environment with the consequent generation of T regulatory cells. These characteristics suggest that CCL18 may be part of an inhibitory pathway devoted to limiting the generation of specific immune responses at peripheral sites.
The Extracellular Matrix and Cytokines Regulate Microglial Integrin Expression and Activation
Authors: Milner Richard , Campbell Iain L.
Published: April 2014

Microglia are the primary immune effector cells resident within the CNS, whose activation into migratory, phagocytic cells is associated with increased expression of cell adhesion molecules of the integrin family. To determine which specific factors are important regulators of microglial activation and integrin expression, we have examined the influence of individual cytokines and extracellular matrix (ECM) substrates by quantifying cell surface expression of MHC and individual integrins by flow cytometry. We found that the proinflammatory cytokines TNF and IFN-α promoted microglial activation, as assessed by amoeboid morphology and increased expression of MHC class I, and also increased expression of the α4β1 and Mac-1 integrins. In contrast, TGF-β1 had the opposite effect and was dominant over the other cytokines. Furthermore, the ECM substrates fibronectin and vitronectin, but not laminin, also promoted microglial activation and increased expression of the α4β1, α5β1 and Mac-1 integrins, but significantly, the influence of fibronectin and vitronectin was not diminished by TGF-β1. Taken together, this work suggests that, in addition to cytokines, the ECM represents an important regulatory influence on microglial activity. Specifically, it implies that increases in the local availability of fibronectin or vitronectin, as a result of blood-brain barrier breakdown or increased expression in different pathological states of the CNS, could induce microglial activation and increased expression of integrins.
STAT4 Signal Pathways Regulate Inflammation and Airway Physiology Changes in Allergic Airway Inflammation Locally Via Alteration of Chemokines
Authors: Raman Kavita , Kaplan Mark H. , Hogaboam Cory M. , Berlin Aaron , Lukacs Nicholas W.
Published: April 2014

Mice homozygous for the STAT4-null mutation were sensitized to cockroach Ag, challenged intratracheally 21 days later, and compared with STAT4-competent allergic mice. The STAT4−/− mice showed significant decreases in airway hyperreactivity (AHR) and peribronchial eosinophils compared with wild-type controls. In addition, pulmonary levels of chemokines were decreased in the STAT4−/− mice, including CC chemokine ligand (CCL)5, CCL6, CCL11, and CCL17. However, levels of Th2-type cytokines, such as IL-4 and IL-13, as well as serum IgE levels were similar in the two groups. Transfer of splenic lymphocytes from sensitized wild-type mice into sensitized STAT4−/− mice did not restore AHR in the mutant mice. Furthermore, chemokine production and peribronchial eosinophilia were not restored during the cellular transfer experiments. Thus, it appears that STAT4 expression contributes to a type 2 process such as allergen-induced chemokine production and AHR. In additional studies, competent allergic mice were treated with anti-IL-12 locally in the airways at the time of allergen rechallenge. These latter studies also demonstrated a decrease in AHR. Altogether, these data suggest that STAT4-mediated pathways play a role locally within the airway for the exacerbation of the allergen-induced responses.