bluuebunny/crossref_metadata_2025 huggingface dataset:
Iodine and IFN-γ Synergistically Enhance Intercellular Adhesion Molecule 1 Expression on NOD.H2h4 Mouse Thyrocytes
Authors: Sharma Rajni B. , Alegria Judy D. , Talor Monica V. , Rose Noel R. , Caturegli Patrizio , Burek C. Lynne
Published: April 2014

NOD.H2h4 mice spontaneously develop autoimmune lymphocytic thyroiditis that mimics human Hashimoto’s thyroiditis, a disease where iodine, IFN-γ, and adhesion molecules have all been implicated in the pathogenesis. To study how iodine and IFN-γ modulate the expression of ICAM-1, we analyzed NOD.H2h4 thyrocytes in baseline conditions (day 0) and at several time points following supplementation of iodine in the drinking water. On day 0, a small percentage (∼10%) of thyrocytes constitutively expressed ICAM-1. The expression gradually increased to 13, 25, and 41% on days 7, 14 and 28, respectively, returning to baseline (9%) on day 35. The initial ICAM-1 kinetics was paralleled by thyroidal infiltration of CD45+ hemopoietic cells, which increased from an average of 4% on day 0 to an average of 13, 21, and 24% on days 14, 28, and 35, respectively. To distinguish whether the observed ICAM-1 increase was a direct effect of iodine or a consequence of the immune infiltrate, we treated mouse primary thyrocyte cultures with 0.01 mM sodium iodine and showed a 3-fold increased ICAM-1 expression. To assess interaction between IFN-γ and iodine, we analyzed CD45 and ICAM-1expression on thyrocytes from NOD.H2h4 wild-type and NOD.H2h4 thyr-IFN-γ transgenic littermates. Strikingly, IFN-γ interacted synergistically with iodine to enhance ICAM-1 expression on thyrocytes. These findings suggest that iodine and IFN-γ cooperate to promote thyroidal expression of ICAM-1 in this mouse model of thyroiditis, highlighting the complex interplay present in the pathogenesis of Hashimoto’s thyroiditis.
An MHC Class Ib-Restricted TCR That Cross-Reacts with an MHC Class Ia Molecule
Authors: Reed-Loisel Lisa M. , Sullivan Barbara A. , Laur Oskar , Jensen Peter E.
Published: April 2014

TCR transgenic 6C5 T cells recognize an insulin B chain epitope presented by the nonclassical class I MHC molecule, Qa-1b. Positive selection of these T cells was shown previously to require Qa-1b. Despite dedicated specificity for Qa-1b, evidence presented in the current study indicates that 6C5 T cells can cross-recognize a classical class I molecule. Clonal deletion was observed unexpectedly in 6C5.H-2bxq mice, which do not express I-E MHC class II molecules and thus should not be subject to superantigen-mediated negative selection. 6C5 T cells were observed to respond in vivo and in vitro to spleen cells from allogeneic H-2q mice, and specificity was mapped to Dq. Evidence was obtained for direct recognition of Dq, rather than indirect presentation of a Dq-derived peptide presented by Qa-1b. Polyclonal CD8+ T cells from class Ia-deficient KbDb−/− mice reacted in vitro to allogeneic spleen cells with an apparent frequency comparable to conventional class Ia-restricted T cells. Our results provide a clear example of a Qa-1-specific TCR that can cross-react with a class Ia molecule and evidence supporting the idea that this may be a common property of T cells selected by class Ib molecules.
Restricted STAT5 Activation Dictates Appropriate Thymic B versus T Cell Lineage Commitment
Authors: Goetz Christine A. , Harmon Ian R. , O’Neil Jennifer J. , Burchill Matthew A. , Johanns Tanner M. , Farrar Michael A.
Published: April 2014

The molecular mechanisms regulating lymphocyte lineage commitment remain poorly characterized. To explore the role of the IL7R in this process, we generated transgenic mice that express a constitutively active form of STAT5 (STAT5b-CA), a key downstream IL7R effector, throughout lymphocyte development. STAT5b-CA mice exhibit a 40-fold increase in pro-B cells in the thymus. As documented by BrdU labeling studies, this increase is not due to enhanced B cell proliferation. Thymic pro-B cells in STAT5b-CA mice show a modest increase in cell survival (∼4-fold), which correlates with bcl-xL expression. However, bcl-xL transgenic mice do not show increases in thymic B cell numbers. Thus, STAT5-dependent bcl-xL up-regulation and enhanced B cell survival are not sufficient to drive the thymic B cell development observed in STAT5b-CA mice. Importantly, thymic pro-B cells in STAT5b-CA mice are derived from early T cell progenitors (ETPs), suggesting that STAT5 acts by altering ETP lineage commitment. Supporting this hypothesis, STAT5 binds to the pax5 promoter in ETPs from STAT5b-CA mice and induces pax5, a master regulator of B cell development. Conversely, STAT5b-CA mice exhibit a decrease in the DN1b subset of ETPs, demonstrating that STAT5 activation inhibits early T cell differentiation or lineage commitment. On the basis of these findings, we propose that the observed expression of the IL-7R on common lymphoid progenitors, but not ETPs, results in differential STAT5 signaling within these distinct progenitor populations and thus helps ensure appropriate development of B cells and T cells in the bone marrow and thymic environments, respectively.
Recombinant Tumor-Associated MUC1 Glycoprotein Impairs the Differentiation and Function of Dendritic Cells
Authors: Rughetti Aurelia , Pellicciotta Ilenia , Biffoni Mauro , Bäckström Malin , Link Thomas , Bennet Eric P. , Clausen Henrik , Noll Thomas , Hansson Gunnar C. , Burchell Joy M. , Frati Luigi , Taylor-Papadimitriou Joyce , Nuti Marianna
Published: April 2014

Tumors exploit several strategies to evade immune recognition, including the production of a large number of immunosuppressive factors, which leads to reduced numbers and impaired functions of dendritic cells (DCs) in the vicinity of tumors. We have investigated whether a mucin released by tumor cells could be involved in causing these immunomodulating effects on DCs. We used a recombinant purified form of the MUC1 glycoprotein, an epithelial associated mucin that is overexpressed, aberrantly glycosylated, and shed during cancer transformation. The O-glycosylation profile of the recombinant MUC1 glycoprotein (ST-MUC1) resembled that expressed by epithelial tumors in vivo, consisting of large numbers of sialylated core 1 (sialyl-T, ST) oligosaccharides. When cultured in the presence of ST-MUC1, human monocyte-derived DCs displayed a modified phenotype with decreased expression of costimulatory molecules (CD86, CD40), Ag-presenting molecules (DR and CD1d), and differentiation markers (CD83). In contrast, markers associated with an immature phenotype, CD1a and CD206 (mannose receptor), were increased. This effect was already evident at day 4 of DC culture and was dose dependent. The modified phenotype of DCs corresponded to an altered balance in IL-12/IL-10 cytokine production, with DC expressing an IL-10highIL-12low phenotype after exposure to ST-MUC1. These DCs were defective in their ability to induce immune responses in both allogeneic and autologous settings, as detected in proliferation and ELISPOT assays. The altered DC differentiation and Ag presentation function induced by the soluble sialylated tumor-associated mucin may represent a mechanism by which epithelial tumors can escape immunosurveillance.
Development of the Expressed Ig CDR-H3 Repertoire Is Marked by Focusing of Constraints in Length, Amino Acid Use, and Charge That Are First Established in Early B Cell Progenitors
Authors: Ivanov Ivaylo I. , Schelonka Robert L. , Zhuang Yingxin , Gartland G. Larry , Zemlin Michael , Schroeder Harry W.
Published: April 2014

To gain insight into the mechanisms that regulate the development of the H chain CDR3 (CDR-H3), we used the scheme of Hardy to sort mouse bone marrow B lineage cells into progenitor, immature, and mature B cell fractions, and then performed sequence analysis on VH7183-containing Cμ transcripts. The essential architecture of the CDR-H3 repertoire observed in the mature B cell fraction F was already established in the early pre-B cell fraction C. These architectural features include VH gene segment use preference, DH family usage, JH rank order, predicted structures of the CDR-H3 base and loop, and the amino acid composition and average hydrophobicity of the CDR-H3 loop. With development, the repertoire was focused by eliminating outliers to what appears to be a preferred repertoire in terms of length, amino acid composition, and average hydrophobicity. Unlike humans, the average length of CDR-H3 increased during development. The majority of this increase came from enhanced preservation of JH sequence. This was associated with an increase in the prevalence of tyrosine. With an accompanying increase in glycine, a shift in hydrophobicity was observed in the CDR-H3 loop from near neutral in fraction C (−0.08 ± 0.03) to mild hydrophilic in fraction F (−0.17 ± 0.02). Fundamental constraints on the sequence and structure of CDR-H3 are thus established before surface IgM expression.
DNA Polymerase η Contributes to Strand Bias of Mutations of A versus T in Immunoglobulin Genes
Authors: Mayorov Vladimir I. , Rogozin Igor B. , Adkison Linda R. , Gearhart Patricia J.
Published: April 2014

DNA polymerase (pol) η participates in hypermutation of A:T bases in Ig genes because humans deficient for the polymerase have fewer substitutions of these bases. To determine whether polymerase η is also responsible for the well-known preference for mutations of A vs T on the nontranscribed strand, we sequenced variable regions from three patients with xeroderma pigmentosum variant (XP-V) disease, who lack polymerase η. The frequency of mutations in the intronic region downstream of rearranged JH4 gene segments was similar between XP-V and control clones; however, there were fewer mutations of A:T bases and correspondingly more substitutions of C:G bases in the XP-V clones (p < 10−7). There was significantly less of a bias for mutations of A compared with T nucleotides in the XP-V clones compared with control clones, whereas the frequencies for mutations of C and G were identical in both groups. An analysis of mutations in the WA sequence motif suggests that polymerase η generates more mutations of A than T on the nontranscribed strand. This in vivo data from polymerase η-deficient B cells correlates well with the in vitro specificity of the enzyme. Because polymerase η inserts more mutations opposite template T than template A, it would generate more substitutions of A on the newly synthesized strand.
Deoxyuridine Is Generated Preferentially in the Nontranscribed Strand of DNA from Cells Expressing Activation-Induced Cytidine Deaminase
Authors: Martomo Stella A. , Fu Dongtao , Yang William W. , Joshi Nikhil S. , Gearhart Patricia J.
Published: April 2014

Activation-induced cytidine deaminase (AID) is required for somatic hypermutation and class switch recombination of Ig genes in B cells. Although AID has been shown to deaminate deoxycytidine to deoxyuridine in DNA in vitro, there is no physical evidence for increased uracils in DNA from cells expressing AID in vivo. We used several techniques to detect uracil bases in a gene that was actively transcribed in Escherichia coli cells expressing AID. Plasmid DNA containing the gene was digested with uracil-DNA glycosylase to remove uracil, and apurinic/apryimidinic endonuclease to nick the abasic site. The nicked DNA was first analyzed using alkaline gel electrophoresis, in which there was a 2-fold increase in the linear form of the plasmid after AID induction compared with plasmid from noninduced bacteria. Second, using a quantitative denaturing Southern blot technique, the gene was predominantly nicked in the nontranscribed strand compared with the transcribed strand. Third, using ligation-mediated PCR, the nicks were mapped on the nontranscribed strand and were located primarily at cytosine bases. These data present direct evidence for the presence of uracils in DNA from cells that are induced to express AID, and they are preferentially generated at cytosines in the nontranscribed strand during transcription.
The Influences of Hinge Length and Composition on the Susceptibility of Human IgA to Cleavage by Diverse Bacterial IgA1 Proteases
Authors: Senior Bernard W. , Woof Jenny M.
Published: April 2014

The influences of IgA hinge length and composition on its susceptibility to cleavage by bacterial IgA1 proteases were examined using a panel of IgA hinge mutants. The IgA1 proteases of Streptococcus pneumoniae, Streptococcus sanguis strains SK4 and SK49, Neisseria meningitidis, Neisseria gonorrhoeae, and Haemophilus influenzae cleaved IgA2-IgA1 half hinge, an Ab featuring half of the IgA1 hinge incorporated into the equivalent site in IgA1 protease-resistant IgA2, whereas those of Streptococcus mitis, Streptococcus oralis, and S. sanguis strain SK1 did not. Hinge length reduction by removal of two of the four C-terminal proline residues rendered IgA2-IgA1 half hinge resistant to all streptococcal IgA1 metalloproteinases but it remained sensitive to cleavage by the serine-type IgA1 proteases of Neisseria and Haemophilus spp. The four C-terminal proline residues could be substituted by alanine residues or transferred to the N-terminal extremity of the hinge without affect on the susceptibility of the Ab to cleavage by serine-type IgA1 proteases. However, their removal rendered the Ab resistant to cleavage by all the IgA1 proteases. We conclude that the serine-type IgA1 proteases of Neisseria and Haemophilus require the Fab and Fc regions to be separated by at least ten (or in the case of N. gonorrhoeae type I protease, nine) amino acids between Val222 and Cys241 (IgA1 numbering) for efficient access and cleavage. By contrast, the streptococcal IgA1 metalloproteinases require 12 or more appropriate amino acids between the Fab and Fc to maintain a minimum critical distance between the scissile bond and the start of the Fc.
Transcriptional Regulation of the Mouse IL-7 Receptor α Promoter by Glucocorticoid Receptor
Authors: Lee Hai-Chon , Shibata Hirofumi , Ogawa Shinya , Maki Kazushige , Ikuta Koichi
Published: April 2014

Expression of the IL-7R α-chain (IL-7Rα) is strictly regulated during the development and maturation of lymphocytes. Glucocorticoids (GC) have pleiotypic effects on the growth and function of lymphocytes. Although GC have been reported to induce the transcription of IL-7Rα gene in human T cells, its molecular mechanism is largely unknown. In this study, we show that GC up-regulate the levels of IL-7Rα mRNA and protein in mouse T cells. This effect does not require protein synthesis de novo, because protein synthesis inhibitors do not block the process. Mouse IL-7Rα promoter has striking homology with human and rat, containing consensus motifs of Ikaros, PU.1, and Runx1 transcription factors. In addition, a conserved noncoding sequence (CNS) of ∼270 bp was found 3.6-kb upstream of the promoter, which was designated as CNS-1. A GC receptor (GR) motif is present in the CNS-1 region. Importantly, we show by reporter assay that the IL-7Rα promoter has specific transcription activity in T cells. This activity highly depends on the PU.1 motif. Furthermore, GC treatment augments the transcriptional activity through the GR motif in the CNS-1 region. We also demonstrate that GR binds to the GR motif by EMSA. In addition, by chromatin immunoprecipitation assay, we show that GR is rapidly recruited to endogenous CNS-1 chromatin after GC stimulation. These results demonstrate that GR binds to the GR motif in the CNS-1 region after GC stimulation and then activates the transcription of the IL-7Rα promoter. Thus, this study identifies the IL-7Rα CNS-1 region as a GC-responsive element.
Differential Src Family Kinase Activity Requirements for CD3ζ Phosphorylation/ZAP70 Recruitment and CD3ε Phosphorylation
Authors: Lysechko Tara L. , Ostergaard Hanne L.
Published: April 2014

The current model of T cell activation is that TCR engagement stimulates Src family tyrosine kinases (SFK) to phosphorylate CD3ζ. CD3ζ phosphorylation allows for the recruitment of the tyrosine kinase ZAP70, which is phosphorylated and activated by SFK, leading to the phosphorylation of downstream targets. We stimulated mouse CTLs with plate-bound anti-CD3 and, after cell lysis, recovered proteins that associated with the CD3 complex. The protein complexes were not preformed, and a number of tyrosine-phosphorylated proteins were inducibly and specifically associated with the TCR/CD3 complex. These results suggest that complex formation only occurs at the site of TCR engagement. The recruitment and tyrosine phosphorylation of most proteins were abolished when T cells were stimulated in the presence of the SFK inhibitor PP2. Surprisingly, CD3ζ, but not CD3ε, was inducibly tyrosine phosphorylated in the presence of PP2. Furthermore, ZAP70 was recruited, but not phosphorylated, after TCR stimulation in the presence of PP2, thus confirming the phosphorylation status of CD3ζ. These data suggest that there is a differential requirement for SFK activity in phosphorylation of CD3ζ vs CD3ε. Consistent with this possibility, ZAP70 recruitment was also detected with anti-CD3-stimulated, Lck-deficient human Jurkat T cells. We conclude that TCR/CD3-induced CD3ζ phosphorylation and ZAP70 recruitment do not absolutely require Lck or other PP2-inhibitable SFK activity, but that SFK activity is absolutely required for CD3ε and ZAP70 phosphorylation. These data reveal the potential for regulation of signaling through the TCR complex by the differential recruitment or activation of SFK.
Differential Expression Regulation of the α and β Subunits of the PA28 Proteasome Activator in Mature Dendritic Cells
Authors: Ossendorp Ferry , Fu Nathalie , Camps Marcel , Granucci Francesca , Gobin Sam J. P. , van den Elsen Peter J. , Schuurhuis Danita , Adema Gosse J. , Lipford Grayson B. , Chiba Tomoki , Sijts Alice , Kloetzel Peter-M. , Ricciardi-Castagnoli Paola , Melief Cornelis J. M.
Published: April 2014

Activation of dendritic cells (DC) by Th-dependent (CD40) or -independent (LPS, CpG, or immune complexes) agonistic stimuli strongly enhances the expression of the proteasome activator PA28αβ complex. Upon activation of DC, increased MHC class I presentation occurred of the melanocyte-associated epitope tyrosinase-related protein 2180-188 in a PA28αβ-dependent manner. In contrast to other cell types, regulation of PA28αβ expression in DC after maturation was found to be IFN-γ independent. In the present study, we show that expression of PA28α and β subunits was differentially regulated. Firstly, PA28α expression is high in both immature and mature DC. In contrast, PA28β expression is low in immature DC and strongly increased in mature DC. Secondly, we show the presence of a functional NF-κB site in the PA28β promoter, which is absent in the PA28α promoter, indicating regulation of PA28β expression by transcription factors of the NF-κB family. In addition, glycerol gradient analysis of DC lysates revealed elevated PA28αβ complex formation upon maturation. Thus, induction of PA28β expression allows proper PA28αβ complex formation, thereby enhancing proteasome activity in activated DC. Therefore, maturation of DC not only improves costimulation but also MHC class I processing. This mechanism enhances the CD8+ CTL (cross)-priming capacity of mature DC.
STAT-1 Mediates the Stimulatory Effect of IL-10 on CD14 Expression in Human Monocytic Cells
Authors: Rahimi Ali Akbar Rahim , Gee Katrina , Mishra Sasmita , Lim Wilfred , Kumar Ashok
Published: April 2014

IL-10, an anti-inflammatory cytokine, has been shown to exhibit stimulatory functions including CD14 up-regulation on human monocytic cells. CD14-mediated signaling following LPS stimulation of monocytic cells results in the synthesis of proinflammatory cytokines. Our results show that LPS-induced CD14 expression on monocytic cells may be mediated by endogenously produced IL-10. To investigate the molecular mechanism by which IL-10 enhances CD14 expression, both human monocytes and the promyelocytic HL-60 cells were used as model systems. IL-10 induced the phosphorylation of PI3K and p42/44 ERK MAPK. By using specific inhibitors for PI3K (LY294002) and ERK MAPKs (PD98059), we demonstrate that LY294002 either alone or in conjunction with PD98059 inhibited IL-10-induced phosphorylation of STAT-1 and consequently CD14 expression. However, IL-10-induced STAT-3 phosphorylation remained unaffected under these conditions. Finally, STAT-1 interfering RNA inhibited IL-10-induced CD14 expression. Taken together, these results suggest that IL-10-induced CD14 up-regulation in human monocytic cells may be mediated by STAT-1 activation through the activation of PI3K either alone or in concert with the ERK MAPK.
Qualitative and Quantitative Differences in Peptides Bound to HLA-B27 in the Presence of Mouse versus Human Tapasin Define a Role for Tapasin as a Size-Dependent Peptide Editor
Authors: Sesma Laura , Galocha Begoña , Vázquez Miriam , Purcell Anthony W. , Marcilla Miguel , McCluskey James , de Castro José A. López
Published: April 2014

Tapasin (Tpn) is a chaperone of the endoplasmic reticulum involved in peptide loading to MHC class I proteins. The influence of mouse Tpn (mTpn) on the HLA-B*2705-bound peptide repertoire was analyzed to characterize the species specificity of this chaperone. B*2705 was expressed on Tpn-deficient human 721.220 cells cotransfected with human (hTpn) or mTpn. The heterodimer to β2-microglobulin-free H chain ratio on the cell surface was reduced with mTpn, suggesting lower B*2705 stability. The B*2705-bound peptide repertoires loaded with hTpn or mTpn shared 94–97% identity, although significant differences in peptide amount were observed in 16–17% of the shared ligands. About 3–6% of peptides were bound only with either hTpn or mTpn. Nonamers differentially bound with mTpn had less suitable anchor residues and bound B*2705 less efficiently in vitro than those loaded only with hTpn or shared nonamers. Decamers showed a different pattern: those found only with mTpn had similarly suitable residues as shared decamers and bound B*2705 with high efficiency. Peptides differentially presented by B*2705 on human or mouse cells showed an analogous pattern of residue suitability, suggesting that the effect of mTpn on B*2705 loading is comparable in both cell types. Thus, mTpn has quantitative and qualitative effects on the B*2705-bound peptide repertoire, impairing presentation of some suitable ligands and allowing others with suboptimal anchor residues and lower affinity to be presented. Our results favor a size-dependent peptide editing role of Tpn for HLA-B*2705 that is species-dependent and suboptimally performed, at least for nonamers, by mTpn.
Sustained Pre-TCR Expression in Notch1IC-Transgenic Rats Impairs T Cell Maturation and Selection
Authors: van den Brandt Jens , Kwon Soon-Hwan , Hünig Thomas , McPherson Kirsty G. , Reichardt Holger M.
Published: April 2014

Notch1 is involved in directing cell fate decisions in a variety of developmental scenarios. Extending previous experiments in mice, we generated transgenic rats expressing the intracellular domain of Notch1 in the thymus. Importantly, this leads to sustained expression of the pre-TCR throughout thymocyte development, accompanied by a reduction of αβTCR complexes. In addition, re-expression of RAG-1 and RAG-2 in TCRβ+ cells is impaired, and the Vα repertoire is altered. Consequently, thymocytes in transgenic rats do not undergo positive selection and largely fail to progress to the single positive stage. According to our model, the previously reported effects of Notch1 on the CD4/CD8 cell fate decision may be explained by a differential sensitivity of the two lineages toward altered TCR signaling.
T Cell Retargeting with MHC Class I-Restricted Antibodies: The CD28 Costimulatory Domain Enhances Antigen-Specific Cytotoxicity and Cytokine Production
Authors: Willemsen Ralph A. , Ronteltap Cees , Chames Patrick , Debets Reno , Bolhuis Reinder L. H.
Published: April 2014

T cells require both primary and costimulatory signals for optimal activation. The primary Ag-specific signal is delivered by engagement of the TCR. The second Ag-independent costimulatory signal is mediated by engagement of the T cell surface costimulatory molecule CD28 with its target cell ligand B7. However, many tumor cells do not express these costimulatory molecules. We previously constructed phage display derived FAB, G8, and Hyb3, Ab-based receptors with identical specificity but distinct affinities for HLA-A1/MAGE-A1, i.e., “TCR-like” specificity. These chimeric receptors comprised the FcεRI-γ signaling element. We analyzed whether linking the CD28 costimulation structure to it (γ + CD28) could affect the levels of MHC-restricted cytolysis and/or cytokine production. Human scFv-G8POS T lymphocytes comprising the γ + CD28 vs the γ signaling element alone produced substantially more IL-2, TNF-α, and IFN-γ in response to HLA-A1/MAGE-A1POS melanoma cells. Also a drastic increase in cytolytic capacity of scFv-G8POS T cells, equipped with γ + CD28 vs the γ-chain alone was observed.
Enhanced Expression of CD20 in Human Tumor B Cells Is Controlled through ERK-Dependent Mechanisms
Authors: Wojciechowski Wojciech , Li Huifen , Marshall Shannon , Dell’Agnola Chiara , Espinoza-Delgado Igor
Published: April 2014

Rituximab, a chimeric Ab directed against CD20, induces apoptosis in targeted cells. Although the majority of B cell malignancies express the CD20 Ag, only ∼50% of patients will respond to single-agent rituximab. The available data suggest that a decreased CD20 expression could account for the lack of response observed in some patients treated with rituximab. Despite the potential critical role of CD20 in the biology of B cell malignancies, the mechanisms controlling its expression are poorly understood. We evaluated the effect of the immune modulator agent bryostatin-1 on the expression of CD20 in non-Hodgkin’s lymphoma cells. Using the B cell lines, DB and RAMOS, as well as tumor cells derived from a chronic lymphocytic leukemia patient, we demonstrated that bryostatin-1 enhanced the expression of both CD20 mRNA and protein. The enhanced expression of CD20 was associated with increased transcriptional activity of the CD20 gene, whereas the stability of CD20 mRNA was not affected. The effect of bryostatin-1 on CD20 expression in non-Hodgkin’s lymphoma cells was mediated through the MAPK kinase/ERK signal transduction pathway and involved protein kinase C, but was independent of p38 MAPK and was insensitive to dexamethasone. Cells pretreated with bryostatin-1 were more susceptible to the proapoptotic effect of anti-CD20 Ab. Overall, these data demonstrate for the first time that ERK phosphorylation is required for the up-regulated expression of CD20 on B cell malignancies. The findings also suggest that bryostatin-1 and rituximab could be a valuable combined therapy for B cell malignancies.
Glucocorticoid-Induced TNF Receptor Functions as a Costimulatory Receptor That Promotes Survival in Early Phases of T Cell Activation
Authors: Esparza Edward M. , Arch Robert H.
Published: April 2014

Glucocorticoid-induced TNFR (GITR) is a member of the TNFR family that can inhibit the suppressive function of regulatory T cells and promote the survival and activation of T cells. However, little is known about the molecular mechanisms regulating T cell survival and activation downstream of GITR. To gain further insight into the cellular events and signaling pathways triggered by GITR, survival, proliferation, and cytokine production as well as activation of MAPKs and NF-κB were monitored after cross-linking of the receptor on naive and activated T cells. GITR cross-linking provided costimulation of naive and activated T cells and resulted in activation of MAPKs and NF-κB. Although GITR-induced signaling pathways augmented the survival of naive T cells, they were not sufficient to inhibit activation-induced cell death triggered by CD3 cross-linking of activated T cells. Differences in the contributions of GITR to cell survival between naive and activated T cells suggest that the receptor triggers specific pathways depending on the activation state of the T cell.
Glucocorticoid-Induced TNF Receptor, a Costimulatory Receptor on Naive and Activated T Cells, Uses TNF Receptor-Associated Factor 2 in a Novel Fashion as an Inhibitor of NF-κB Activation
Authors: Esparza Edward M. , Arch Robert H.
Published: April 2014

Glucocorticoid-induced TNFR (GITR) has been implicated as an essential regulator of immune responses to self tissues and pathogens. We have recently shown that GITR-induced cellular events promote survival of naive T cells, but are insufficient to protect against activation-induced cell death. However, the molecular mechanisms of GITR-induced signal transduction that influence physiologic and pathologic immune responses are not well understood. TNFR-associated factors (TRAFs) are pivotal adapter proteins involved in signal transduction pathways of TNFR-related proteins. Yeast two-hybrid assays and studies in HEK293 cells and primary lymphocytes indicated interactions between TRAF2 and GITR mediated by acidic residues in the cytoplasmic domain of the receptor. GITR-induced activation of NF-κB is blocked by A20, an NF-κB-inducible protein that interacts with TRAFs and functions in a negative feedback mechanism downstream of other TNFRs. Interestingly, in contrast with its effects on signaling triggered by other TNFRs, our functional studies revealed that TRAF2 plays a novel inhibitory role in GITR-triggered NF-κB activation.
Structure/Function Analysis of Tristetraprolin (TTP): p38 Stress-Activated Protein Kinase and Lipopolysaccharide Stimulation Do Not Alter TTP Function
Authors: Rigby William F. C. , Roy Kristen , Collins Jane , Rigby Sam , Connolly John E. , Bloch Donald B. , Brooks Seth A.
Published: April 2014

Tristetraprolin (TTP) is the only trans-acting factor shown to be capable of regulating AU-rich element-dependent mRNA turnover at the level of the intact animal; however, the mechanism by which TTP mediated RNA instability is unknown. Using an established model system, we performed structure/function analysis with TTP as well as examined the current hypothesis that TTP function is regulated by p38-MAPKAP kinase 2 (MK2) activation. Deletion of either the N- or C-terminal domains inhibited TTP function. Extensive mutagenesis, up to 16%, of serines and threonines, some of which were predicted to mediate proteasomal targeting, did not alter human TTP function. Mutation of the conserved MK2 phosphorylation sites enhanced human TTP function in both resting and p38-stress-activated protein kinase-MK2-activated cells. However, p38-stress-activated protein kinase-MK2 activation did not alter the activity of either wild-type or mutant TTP. TTP localized to the stress granules, with arsenite treatment reducing this localization. In contrast, arsenite treatment enhanced stress granule localization of the MK2 mutant, consistent with the involvement of additional pathways regulating this event. Finally, we determined that, in response to LPS stimulation, human TTP moves onto the polysomes, and this movement occurs in the absence of 14-3-3. Taken together, these data indicate that, although p38 activation alters TTP entry into the stress granule, it does not alter TTP function. Moreover, the interaction of TTP with 14-3-3, which may limit entry into the stress granule, is not involved in the downstream message stabilization events.
The Non-MHC Quantitative Trait LocusCia5Contains Three Major Arthritis Genes That Differentially Regulate Disease Severity, Pannus Formation, and Joint Damage in Collagen- and Pristane-Induced Arthritis
Authors: Brenner Max , Meng Hsiang-Chi , Yarlett Nuriza C. , Joe Bina , Griffiths Marie M. , Remmers Elaine F. , Wilder Ronald L. , Gulko Pércio S.
Published: April 2014

Cia5 is a locus on rat chromosome 10 which regulates the severity of collagen- and pristane-induced arthritis (CIA and PIA). To refine the region toward positional identification, Cia5 subcongenic strains were generated and studied in PIA and CIA. The protective effect of the telomeric locus Cia5a was confirmed in both models. A second arthritis severity locus (Cia5d) was identified within the most centromeric portion of Cia5. DA.F344(Cia5d) rats had a significantly lower median arthritis severity index in PIA, but not in CIA, compared with DA. On histologic analyses DA.F344(Cia5a) and DA.F344(Cia5d) congenics with PIA preserved a nearly normal joint architecture compared with DA, including significant reduction in synovial hyperplasia, pannus, angiogenesis, inflammatory infiltration, bone and cartilage erosions. Cia5 and Cia5a synovial levels of IL-1β mRNA were reduced. Although both DA.F344(Cia5) and DA.F344(Cia5a) rats were protected in CIA, the arthritis scores of DA.F344(Cia5) were significantly higher than those of DA.F344(Cia5a), suggesting the existence of a third locus where F344-derived alleles centromeric from Cia5a contribute to increased arthritis severity. The existence of the third locus was further supported by higher levels of autoantibodies against rat type II collagen in DA.F344(Cia5) congenics compared with DA.F344(Cia5a). Our results determined that Cia5 contains three major arthritis severity regulatory loci regulating central events in the pathogenesis of arthritis, and differentially influencing CIA and PIA. These loci are syntenic to regions on human chromosomes 17q and 5q implicated in the susceptibility to rheumatoid arthritis, suggesting that the identification of these genes will be relevant to human disease.
Exacerbated Susceptibility to Infection-Stimulated Immunopathology in CD1d-Deficient Mice
Authors: Smiley Stephen T. , Lanthier Paula A. , Couper Kevin N. , Szaba Frank M. , Boyson Jonathan E. , Chen Wangxue , Johnson Lawrence L.
Published: April 2014

Mice lacking functional CD1d genes were used to study mechanisms of resistance to the protozoan parasite Toxoplasma gondii. Wild-type (WT) BALB/c mice, CD1d-deficient BALB/c mice, and WT C57BL/6 mice all survived an acute oral infection with a low dose of mildly virulent strain ME49 T. gondii cysts. In contrast, most CD1d-deficient C57BL/6 mice died within 2 wk of infection. Despite having parasite burdens that were only slightly higher than WT mice, CD1d-deficient C57BL/6 mice displayed greater weight loss and intestinal pathology. In C57BL/6 mice, CD4+ cells can cause intestinal pathology during T. gondii infection. Compared with WT mice, infected CD1d-deficient C57BL/6 mice had higher frequencies and numbers of activated (CD44high) CD4+ cells in mesenteric lymph nodes. Depletion of CD4+ cells from CD1d-deficient mice reduced weight loss and prolonged survival, demonstrating a functional role for CD4+ cells in their increased susceptibility to T. gondii infection. CD1d-deficient mice are deficient in Vα14+ T cells, a major population of NKT cells. Involvement of these cells in resistance to T. gondii was investigated using gene-targeted Jα18-deficient C57BL/6 mice, which are deficient in Vα14+ T cells. These mice did not succumb to acute infection, but experienced greater weight loss and more deaths than B6 mice during chronic infection, indicating that Vα14+ cells contribute to resistance to T. gondii. The data identify CD4+ cells as a significant component of the marked susceptibility to T. gondii infection observed in CD1d-deficient C57BL/6mice, and establish T. gondii as a valuable tool for deciphering CD1d-dependent protective mechanisms.
B Lymphocyte Activation by Human Papillomavirus-Like Particles Directly Induces Ig Class Switch Recombination via TLR4-MyD88
Authors: Yang Rongcun , Murillo Francisco Martinez , Delannoy Michael J. , Blosser R. Lee , Yutzy William H. , Uematsu Satoshi , Takeda Kiyoshi , Akira Shizuo , Viscidi Raphael P. , Roden Richard B. S.
Published: April 2014

Vaccination with human papillomavirus type 16 (HPV16) L1 virus-like particles (VLP) induces both high titer neutralizing IgG and protective immunity. Because protection from experimental infection by papillomavirus is mediated by neutralizing IgG, we sought the mechanisms that trigger humoral immunity to HPV16 L1 VLP. We find that HPV16 L1 VLP bind to murine B lymphocytes thereby inducing activation-induced cytidine deaminase expression and Ig class switch recombination to cause the generation of IgG. HPV16 L1 VLP also activate production of proinflammatory factors IFN-α, IL-6, MIP-1α, RANTES, and KC, up-regulate the expression of costimulatory molecules by naive B cells, and increase the B1 B cell subpopulation. These B cell responses to HPV16 L1 VLP are dependent upon MyD88. Although MyD88−/− B cells produce only μ transcript after exposure to HPV16 L1 VLP, MyD88+/+ B cells express α, γ, and μ Ig H chain and activation-induced cytidine deaminase transcripts. Notably, TLR4 mutant C3H/HeJ mice exhibited significantly reduced HPV16 VLP-specific IgG1, IgG2a, IgG2b, and IgG3 titers after vaccination as compared with the control C3H/HeOuJ mice. HPV16 L1 VLP directly activated class switch recombination and costimulatory molecule expression by B cells of C3H/HeOuJ mice but not C3H/HeJ mice. Thus HPV16 L1 VLP directly activate B cells to induce CD4+ T cell independent humoral immune responses via TLR4- and MyD88-dependent signaling.
Generation of Antifungal Effector CD8+ T Cells in the Absence of CD4+ T Cells duringCryptococcus neoformansInfection
Authors: Lindell Dennis M. , Moore Thomas A. , McDonald Roderick A. , Toews Galen B. , Huffnagle Gary B.
Published: April 2014

Immunity to the opportunistic fungus Cryptococcus neoformans is dependent on cell-mediated immunity. Individuals with defects in cellular immunity, CD4+ T cells in particular, are susceptible to infection with this pathogen. In host defense against a number of pathogens, CD8+ T cell responses are dependent upon CD4+ T cell help. The goal of these studies was to determine whether CD4+ T cells are required for the generation of antifungal CD8+ T cell effectors during pulmonary C. neoformans infection. Using a murine intratracheal infection model, our results demonstrated that CD4+ T cells were not required for the expansion and trafficking of CD8+ T cells to the site of infection. CD4+ T cells were also not required for the generation of IFN-γ-producing CD8+ T cell effectors in the lungs. In CD4− mice, depletion of CD8+ T cells resulted in increased intracellular infection of pulmonary macrophages by C. neoformans, increasing the pulmonary burden of the infection. Neutralization of IFN-γ in CD4−CD8+ mice similarly increased macrophage infection by C. neoformans, thereby blocking the protection provided by CD8+ T cells. Altogether, these data support the hypothesis that effector CD8+ T cell function is independent of CD4+ T cells and that IFN-γ production from CD8+ T cells plays a role in controlling C. neoformans by limiting survival of C. neoformans within macrophages.
FliC-Specific CD4+ T Cell Responses Are Restricted by Bacterial Regulation of Antigen Expression
Authors: Cummings Lisa A. , Barrett Sara L. Rassoulian , Wilkerson W. David , Fellnerova Ivana , Cookson Brad T.
Published: April 2014

Salmonella typhimurium, a facultatively intracellular pathogen, regulates expression of virulence factors in response to distinct environments encountered during the course of infection. We tested the hypothesis that the transition from extra- to intracellular environments during Salmonella infection triggers changes in Ag expression that impose both temporal and spatial limitations on the host T cell response. CD4+ T cells recovered from Salmonella immune mice were propagated in vitro using Ag derived from bacteria grown in conditions designed to emulate extra- or intracellular environments in vivo. Extracellular phase bacteria supported a dominant T cell response to the flagellar subunit protein FliC, whereas intracellular phase bacteria were unable to support expansion of FliC-specific T cells from populations known to contain T cells with reactivity to this Ag. This result was attributed to bacterial regulation of FliC expression: transcription and protein levels were repressed in bacteria growing in the spleens of infected mice. Furthermore, Salmonella-infected splenocytes taken directly ex vivo stimulated FliC-specific T cell clones only when intracellular FliC expression was artificially up-regulated. Although it has been suggested that a microanatomical separation of immune T cells and infected APC exists in vivo, we demonstrate that intracellular Salmonella can repress FliC expression below the T cell activation threshold. This potentially provides a mechanism for intracellular Salmonella at systemic sites to avoid detection by Ag-specific T cells primed at intestinal sites early in infection.
Inhibition of MAPK and NF-κB Pathways Is Necessary for Rapid Apoptosis in Macrophages Infected with Yersinia
Authors: Zhang Yue , Ting Adrian T. , Marcu Kenneth B. , Bliska James B.
Published: April 2014

Macrophages respond to infection with pathogenic Yersinia species by activating MAPK- and NF-κB-signaling pathways. To counteract this response, Yersiniae secrete a protease (Yersinia outer protein J (YopJ)) that is delivered into macrophages, deactivates MAPK- and NF-κB-signaling pathways, and induces apoptosis. NF-κB promotes cell survival by up-regulating expression of several apoptosis inhibitor genes. Previous studies show that deactivation of the NF-κB pathway by YopJ is important for Yersinia-induced apoptosis. To determine whether deactivation of the NF-κB pathway is sufficient for Yersinia-induced apoptosis, two inhibitors of the NF-κB pathway, IκBα superrepressor or A20, were expressed in macrophages. Macrophages expressing these proteins were infected with Yersinia pseudotuberculosis strains that secrete functionally active or inactive forms of YopJ. Apoptosis levels were substantially higher (5- to 10-fold) when active YopJ was delivered into macrophages expressing IκBα superrepressor or A20, suggesting that deactivation of the NF-κB pathway is not sufficient for rapid Yersinia-induced apoptosis. When macrophages expressing A20 were treated with specific inhibitors of MAPKs, similar levels of apoptosis (within ∼2-fold) were observed when active or inactive YopJ were delivered during infection. These results suggest that MAPK and NF-κB pathways function together to up-regulate apoptosis inhibitor gene expression in macrophages in response to Yersinia infection and that YopJ deactivates both pathways to promote rapid apoptosis. In addition, treating macrophages with a proteasome inhibitor results in higher levels of infection-induced apoptosis than can be achieved by blocking NF-κB function alone, suggesting that proapoptotic proteins are stabilized when proteasome function is blocked in macrophages.
Late Priming and Variability of Epitope-Specific CD8+ T Cell Responses during a Persistent Virus Infection
Authors: Kemball Christopher C. , Lee Eun D. Han , Vezys Vaiva , Pearson Thomas C. , Larsen Christian P. , Lukacher Aron E.
Published: April 2014

Control of persistently infecting viruses requires that antiviral CD8+ T cells sustain their numbers and effector function. In this study, we monitored epitope-specific CD8+ T cells during acute and persistent phases of infection by polyoma virus, a mouse pathogen that is capable of potent oncogenicity. We identified several novel polyoma-specific CD8+ T cell epitopes in C57BL/6 mice, a mouse strain highly resistant to polyoma virus-induced tumors. Each of these epitopes is derived from the viral T proteins, nonstructural proteins produced by both productively and nonproductively (and potentially transformed) infected cells. In contrast to CD8+ T cell responses described in other microbial infection mouse models, we found substantial variability between epitope-specific CD8+ T cell responses in their kinetics of expansion and contraction during acute infection, maintenance during persistent infection, as well as their expression of cytokine receptors and cytokine profiles. This epitope-dependent variability also extended to differences in maturation of functional avidity from acute to persistent infection, despite a narrowing in TCR repertoire across all three specificities. Using a novel minimal myeloablation-bone marrow chimera approach, we visualized priming of epitope-specific CD8+ T cells during persistent virus infection. Interestingly, epitope-specific CD8+ T cells differed in CD62L-selectin expression profiles when primed in acute or persistent phases of infection, indicating that the context of priming affects CD8+ T cell heterogeneity. In summary, persistent polyoma virus infection both quantitatively and qualitatively shapes the antiviral CD8+ T cell response.
Retinoic Acid and Polyriboinosinic:Polyribocytidylic Acid Stimulate Robust Anti-Tetanus Antibody Production while Differentially Regulating Type 1/Type 2 Cytokines and Lymphocyte Populations
Authors: Ma Yifan , Chen Qiuyan , Ross A. Catharine
Published: April 2014

Retinoic acid (RA), a bioactive retinoid, and polyriboinosinic:polyribocytidylic acid (PIC) are known to promote immunity in vitamin A-deficient animals. In this study, we hypothesized that RA, PIC, and the combination can provide significant immunoadjuvant activity even in the vitamin A-adequate state. Six-week-old C57BL/6 mice were immunized with tetanus toxoid (TT) and treated with RA and/or PIC at priming in three independent studies of short and long duration. RA and PIC differentially regulated both primary and secondary anti-TT IgG isotypes, whereas the combination of RA + PIC stimulated the highest level of anti-TT IgG production and, concomitantly, a ratio of IgG1 to IgG2a similar to that of the control group. The regulation of Ab response was strongly associated with type 1/type 2 cytokine gene expression. Whereas RA reduced type 1 cytokines (IFN-γ and IL-12), PIC enhanced both type 1 and type 2 cytokines (IL-4 and IL-12) and cytokine-related transcription factors. Despite the presence of PIC, the IL-4:IFN-γ ratio was significantly elevated by RA. In addition, RA and/or PIC modulated NK/NKT cell populations and the level of expression of the costimulatory molecules CD80/CD86, evident 3 days after priming. Notably, the NKT:NK and CD80:CD86 ratios were correlated with the IL-4:IFN-γ ratio, indicative of multiple converging modes of regulation. Overall, RA, PIC, and RA + PIC rapidly and differentially shaped the anti-tetanus Ig response. The robust, durable, and proportionate increase in all anti-TT IgG isotypes induced by RA + PIC suggests that this combination is promising as a means to enhance the Ab response to TT and similar vaccines.
In Vivo Modulation of T Cell Responses and Protective Immunity by TCR Antagonism during Infection
Authors: Lau Lisa L. , Jiang Jiu , Shen Hao
Published: April 2014

Infectious agents are known to express altered peptide ligands that antagonize T cells in vitro; however, direct evidence of TCR antagonism during infection is still lacking, and its importance in the context of infection remains to be established. In this study, we used a murine model of infection with recombinant Listeria monocytogenes and addressed three issues that are critical for assessing the role of TCR antagonism in the modulation of the immune response. First, we demonstrated that the antagonist peptide efficiently inhibited the ability of the agonist to prime naive TCR-transgenic T cells in vivo. Second, we showed clonal memory T cells were antagonized during recall responses, resulting in loss of protective immunity. Lastly, we observed that even in the context of a polyclonal response, TCR antagonism greatly inhibits the agonist-specific response, leading to altered hierarchy of immunodominance and reduced T cell memory and protective immunity. These results provide direct evidence of clonal TCR antagonism of naive and memory CD8 T cells during infection and demonstrate the effect of TCR antagonism on protective immunity. Thus, agonist/antagonist interactions may play an important role in determining the immunodominance and repertoire of T cell targets, and evaluation of immune responses and vaccine strategies may require examination of not only agonists but also antagonists and their interactions during an infection.