bluuebunny/crossref_metadata_2025 huggingface dataset:
A Natural Model ofLeishmania majorInfection Reveals a Prolonged “Silent” Phase of Parasite Amplification in the Skin Before the Onset of Lesion Formation and Immunity
Authors: Belkaid Yasmine , Mendez Susana , Lira Rosalia , Kadambi Navin , Milon Genevieve , Sacks David
Published: April 2014

A model of Leishmania major infection in C57BL/6 mice has been established that combines two main features of natural transmission: low dose (100 metacyclic promastigotes) and inoculation into a dermal site (the ear dermis). The evolution of the dermal lesion could be dissociated into two distinct phases. The initial “silent” phase, lasting 4–5 wk, favored establishment of the peak load of parasites in the dermis in the absence of lesion formation or any overt histopathologic changes in the site. The second phase corresponds to the development of a lesion associated with an acute infiltration of neutrophils, macrophages, and eosinophils into the dermis and was coincident with the killing of parasites in the site. The onset of immunity/pathology was correlated with the appearance of cells staining for IL-12p40 and IFN-γ in the epidermal compartment, and an expansion of T cells capable of producing IFN-γ in the draining lymph node. Parasite growth was not enhanced over the first 4.5 wk in anti-CD4-treated mice, SCID mice, or C57BL/6 mice deficient in IL-12p40, IFN-γ, CD40 ligand, or inducible NO synthase. These mice all failed to ultimately control infection in the site, but in some cases (anti-CD4 treated, IL-12p40−/−, CD40 ligand−/−, and SCID) high dermal parasite loads were associated with little or no pathology. These results extend to a natural infection model a role for Th1 cells in both acquired resistance and lesion formation, and document the remarkable avoidance of this response during a prolonged phase of parasite amplification in the skin.
Early Onset of CD8 Transgene Expression Inhibits the Transition from DN3 to DP Thymocytes
Authors: Wack Andreas , Coles Mark , Norton Trisha , Hostert Arnd , Kioussis Dimitris
Published: April 2014

In this paper we show that the effects of transgenic coreceptor expression on thymocyte development depend on the onset of transgene expression. Thus, a CD8 transgene expressed on CD44+CD25+ (DN2) and CD44−CD25+ (DN3) cells causes a partial block at the stage when TCRβ selection takes place and diminishes expansion at the subsequent developmental stages, resulting in increased DN3 and markedly reduced double-positive (DP) thymocyte numbers. This effect is evident on a polyclonal TCR repertoire as well as in TCR-transgenic mice (F5). By contrast, a CD8 transgene that leads to the same degree of overexpression on DP thymocytes, but is not expressed on double-negative subsets, has no effect on thymus size or composition. Therefore, the reduction of DP thymocyte numbers in CD8 TCRtg mice can be attributed to interferences at early developmental stages rather than to increased negative selection of DP cells.
CTLA-4 (CD152) Can Inhibit T Cell Activation by Two Different Mechanisms Depending on Its Level of Cell Surface Expression
Authors: Carreno Beatriz M. , Bennett Frann , Chau Thu A. , Ling Vincent , Luxenberg Deborah , Jussif Jason , Baroja Miren Lorea , Madrenas Joaquín
Published: April 2014

CTLA-4 (CD152) engagement results in down-regulation of T cell activation. Two mechanisms have been postulated to explain CTLA-4 inhibition of T cell activation: negative signaling and competitive antagonism of CD28:B7-mediated costimulation. We assessed the contributions of these two mechanisms using a panel of T cell lines expressing human CTLA-4 with mutations in the cytoplasmic region. Under conditions of B7-independent costimulation, inhibition of IL-2 production following CTLA-4 engagement required the CTLA-4 cytoplasmic region. In contrast, under B7-dependent costimulation, inhibition of IL-2 production by CTLA-4 engagement was directly proportional to CTLA-4 cell surface levels and did not require its cytoplasmic region. Thus, CTLA-4 down-regulates T cell activation by two different mechanisms—delivery of a negative signal or B7 sequestration—that are operational depending on the levels of CTLA-4 surface expression. These two mechanisms may have distinct functional outcomes: rapid inhibition of T cell activation or induction of T cell anergy.
CD40 Ligand Trimer and IL-12 Enhance Peripheral Blood Mononuclear Cells and CD4+ T Cell Proliferation and Production of IFN-γ in Response to p24 Antigen in HIV-Infected Individuals: Potential Contribution of Anergy to HIV-Specific Unresponsiveness
Authors: Dybul Mark , Mercier George , Belson Michael , Hallahan Claire W. , Liu Shuying , Perry Cheryl , Herpin Betsey , Ehler Linda , Davey Richard T. , Metcalf Julie A. , Mican JoAnn M. , Seder Robert A. , Fauci Anthony S.
Published: April 2014

It has been suggested that CD4+ T cell proliferative responses to HIV p24 Ag may be important in the control of HIV infection. However, these responses are minimal or absent in many HIV-infected individuals. Furthermore, while in vitro and in vivo responses to non-HIV recall Ags improve upon administration of highly active antiretroviral therapy, there does not appear to be a commensurate enhancement of HIV-specific immune responses. It is possible that CD4+ p24-specific T cells are deleted early in the course of infection. However, it is also possible that a discrete unresponsiveness, or anergy, contributes to the lack of proliferation to p24. To evaluate the possible contribution of unresponsiveness to the lack of CD4+ T cell proliferation to p24 in HIV-infected individuals, we attempted to overcome unresponsiveness. CD40 ligand trimer (CD40LT) and IL-12 significantly increased PBMC and CD4+ T cell proliferative responses to p24 Ag in HIV-infected, but not uninfected, individuals. No increase in proliferative response to CMV Ag was observed. CD40LT exerted its effect through B7-CD28-dependent and IL-12- and IL-15-independent mechanisms. Finally, the increase in proliferation with CD40LT and IL-12 was associated with an augmented production of IFN-γ in most, but not all, individuals. These data suggest the possible contribution of HIV-specific unresponsiveness to the lack of CD4+ T cell proliferation to p24 Ag in HIV-infected individuals and that clonal deletion alone does not explain this phenomenon. They also indicate the potential for CD40LT and IL-12 as immune-based therapies for HIV infection.
CD8+ T Cells Are Necessary for Recognition of Allelic, But Not Locus-Mismatched or Xeno-, HLA Class I Transplantation Antigens
Authors: Borenstein Steven H. , Graham Jeremy , Zhang Xiao-Li , Chamberlain John W.
Published: April 2014

Although HLA transgenic mice (HLA TgM) could provide a powerful approach to investigate human MHC-specific T cell responsiveness, the extent to which these molecules are recognized by the mouse immune system remains unclear. We established TgM expressing HLA class I alleles A2, B7, or B27 in their fully native form (HLAnat) or as hybrid molecules (HLAhyb) of the HLA α1/α2 domains linked to the H-2Kb α3, transmembrane, and cytoplasmic domains (i.e., to maintain possible species-specific interactions). Comparison of each as xeno- (i.e., by non-TgM) vs allo- (i.e., by TgM carrying an alternate HLA allele) transplantation Ags revealed the following: 1) Although HLAhyb molecules induced stronger xeno-CD8+ T cell responses in vitro, additional effector mechanisms must be active in vivo because HLAnat skin grafts were rejected faster by non-TgM; 2) gene knockout recipients showed that xenorejection of HLAnat and, unexpectedly, HLAhyb grafts doesn’t depend on CD8+ or CD4+ T cells or B cells; 3) each HLAhyb strain developed tolerance to “self” but rejected allele- (-B27 vs -B7) and locus- (-B vs -A) mismatched grafts, the former requiring CD8+ T cells, the latter by CD8+ T cell-independent mechanisms. The finding that recognition of xeno-HLAhyb does not require CD8+ T cells while recognition of the identical molecule in a strictly allo context does, demonstrates an α1/α2 domain-dependent difference in effector mechanism(s). Furthermore, the CD8+ T cell-independence of locus-mismatched rejection suggests the degree of similarity between self and non-self α1/α2 determines the effector mechanism(s) activated. The HLA Tg model provides a unique approach to characterize these mechanisms and develop tolerance protocols in the context of human transplantation Ags.
Proteolytic Activities of Two Types of Mannose-Binding Lectin-Associated Serine Protease
Authors: Matsushita Misao , Thiel Steffen , Jensenius Jens C. , Terai Itaru , Fujita Teizo
Published: April 2014

Mannose (or mannan)-binding lectin (MBL) is an oligomeric serum lectin that plays a role in innate immunity by activating the complement system. In human, two types of MBL-associated serine protease (MASP-1 and MASP-2) and a truncated protein of MASP-2 (small MBL-associated protein; sMAP or MAp19) are complexed with MBL. To clarify the proteolytic activities of MASP-1 and MASP-2 against C4, C2, and C3, we isolated these two types of MASP in activated forms from human serum by sequential affinity chromatography. On an anti-MASP-1 column, MASP-2 passed through the column in the presence of EDTA and high salt concentration, whereas MASP-1 was retained. Isolated MASP-1 and MASP-2 exhibited proteolytic activities against C3 and C4, respectively. C2 was activated by both MASPs. C1 inhibitor (C1 INH), an inhibitor for C1r and C1s, formed equimolar complexes with MASP-1 and MASP-2 and inhibited their proteolytic activities.
JNK1 Is Required for T Cell-Mediated Immunity AgainstLeishmania majorInfection
Authors: Constant Stephanie L. , Dong Chen , Yang Derek D. , Wysk Mark , Davis Roger J. , Flavell Richard A.
Published: April 2014

c-Jun N-terminal kinase (JNK) is a mitogen-activated protein kinase that plays important regulatory roles in helper T cell differentiation. In the current study, we used Jnk1-deficient mice to examine the function of JNK during an in vivo pathogenic infection, leishmaniasis, which is strongly influenced by Th1/Th2 effector mechanisms. The data show that Jnk1-deficient mice, despite their usually genetically resistant background, were unable to resolve Leishmania infections. Jnk1−/− mice displayed reduced delayed-type hypersensitivity in response to the pathogen, which was associated with a T cell defect. We found that, although these mice can direct an apparent Th1-response, there is also simultaneous generation of Leishmania-specific Th2 responses, which possibly down-modulate protective Th1-mediated immune function. These findings demonstrate that the negative regulation of Th2 cytokine production by the JNK1 signaling pathway is essential for generating Th1-polarized immunity against intracellular pathogens, such as Leishmania major.
Simvastatin Modulates Cytokine-Mediated Endothelial Cell Adhesion Molecule Induction: Involvement of an Inhibitory G Protein
Authors: Sadeghi Mehran M. , Collinge Mark , Pardi Ruggero , Bender Jeffrey R.
Published: April 2014

Endothelial cell adhesion molecules (CAMs) E-selectin, ICAM-1, and VCAM-1 play variably important roles in immune-mediated processes. They are induced by the proinflammatory cytokines IL-1 and TNF-α, and NF-κB is required for the regulated expression of all three genes. Regulators of this pathway could potentially be potent immune modulators. We studied the effect of a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, simvastatin, on cytokine-induced expression of CAMs in HUVEC. Unexpectedly, pretreatment with simvastatin potentiated the induction of all three endothelial CAMs by IL-1 and TNF, but not LPS or PMA, as detected by flow cytometry. Northern blot analysis demonstrated an increase in steady state IL-1-induced E-selectin mRNA levels in cells pretreated with simvastatin. This was associated with an increase in nuclear translocation of NF-κB, as detected by EMSA. The effect of simvastatin was reversed by mevalonate and geranylgeranyl pyrophosphate but not squalene, indicating that an inhibitory prenylated protein is involved in endothelial responses to proinflammatory cytokines. Pertussis toxin mimicked the effect of simvastatin, and the G protein activator NaF inhibited the cytokine-induced expression of endothelial CAMs, indicating that a Giα protein is involved. These results demonstrate that cytokine-mediated activation of the endothelium, and specifically CAM induction, can be modulated by a heterotrimeric G protein-coupled pathway. This may represent a “basal tone” of endothelial inactivation, which can either be disinhibited or amplified, depending on the stimulus.
Inhibition of LPS-induced Cytokines by Bcl-xL in a Murine Macrophage Cell Line
Authors: Lakics Viktor , Medvedev Andrei E. , Okada Seiji , Vogel Stefanie N.
Published: April 2014

The antiapoptotic molecule Bcl-xL has been implicated in the differentiation and survival of activated macrophages in inflammatory conditions. In this report, the role of Bcl-xL in LPS-induced cytokine gene expression and secretion was studied. Bcl-xL-transfected RAW 264 macrophages were protected from gliotoxin-induced apoptosis, indicating the presence of functional Bcl-xL. Overexpression of Bcl-xL in this macrophage cell line was also associated with a marked inhibition of LPS-induced TNF-α, JE/monocyte chemoattractant protein 1, and macrophage inflammatory protein 2 secretion. Inhibition of LPS-induced cytokine secretion was paralleled by a decrease in levels of steady-state mRNA for the above cytokines and for IL-1β. Decreased production of TNF-α in Bcl-xL transfectants was not due to increased mRNA degradation, as the mRNA half-lives were the same in Bcl-xL transfectants and control macrophages. Although the composition of NF-κB complexes detected by EMSA and supershift analysis in nuclear lysates derived from Bcl-xL transfectants and control cells was indistinguishable, LPS-induced inhibitory κBα degradation, as well as NF-κB binding and AP-1 activation, were slightly decreased by ectopic expression of Bcl-xL. More strikingly, LPS-induced phosphorylation of p38 mitogen-activated protein kinase and c-Jun N-terminal kinase was strongly repressed by Bcl-xL overexpression, offering a possible mechanism for the inhibition of LPS-induced cytokine production. These data provide the first evidence for a novel role for Bcl-xL as an anti-inflammatory mediator in macrophages.
Butyrophilin, a Milk Protein, Modulates the Encephalitogenic T Cell Response to Myelin Oligodendrocyte Glycoprotein in Experimental Autoimmune Encephalomyelitis
Authors: Stefferl Andreas , Schubart Anna , Storch Maria , Amini Aminullah , Mather Ian , Lassmann Hans , Linington Christopher
Published: April 2014

Experimental autoimmune encephalomyelitis (EAE) induced by sensitization with myelin oligodendrocyte glycoprotein (MOG) is a T cell-dependent autoimmune disease that reproduces the inflammatory demyelinating pathology of multiple sclerosis. We report that an encephalitogenic T cell response to MOG can be either induced or alternatively suppressed as a consequence of immunological cross-reactivity, or “molecular mimicry” with the extracellular IgV-like domain of the milk protein butyrophilin (BTN). In the Dark Agouti rat, active immunization with native BTN triggers an inflammatory response in the CNS characterized by the formation of scattered meningeal and perivascular infiltrates of T cells and macrophages. We demonstrate that this pathology is mediated by a MHC class II-restricted T cell response that cross-reacts with the MOG peptide sequence 76–87, IGEGKVALRIQN (identities underlined). Conversely, molecular mimicry with BTN can be exploited to suppress disease activity in MOG-induced EAE. We demonstrate that not only is EAE mediated by the adoptive transfer of MOG74–90 T cell lines markedly ameliorated by i.v. treatment with the homologous BTN peptide, BTN74–90, but that this protective effect is also seen in actively induced disease following transmucosal (intranasal) administration of the peptide. These results identify a mechanism by which the consumption of milk products may modulate the pathogenic autoimmune response to MOG.
A Genetic Model of Stress Displays Decreased Lymphocytes and Impaired Antibody Responses Without Altered Susceptibility toStreptococcus pneumoniae
Authors: Murray Susan E. , Lallman Holly R. , Heard Amanda D. , Rittenberg Marvin B. , Stenzel-Poore Mary P.
Published: April 2014

Stress pathways affect immune function, the most notable of these pathways being activation of the hypothalamic-pituitary-adrenal (HPA) axis. Although HPA activation has generally been relegated to an immunosuppressive role, recent evidence suggests that stress and HPA activation can be immunoenhancing in certain situations. To investigate specific effects of stress on immune function, we used a genetic model of chronic stress wherein transgenic mice overexpress corticotropin-releasing hormone (CRH), a primary mediator of the stress response. In these mice, CRH is overproduced in the brain, leading to chronic activation of the HPA axis. We found that CRH-transgenic mice have decreased leukocyte numbers in lymphoid compartments, with preferential loss of B lymphocytes. They also exhibit decreased Ab production and impaired isotype switching in response to immunization with a thymus-dependent Ag, phosphocholine-keyhole limpet hemocyanin. Despite these deficits, immunization protected CRH-transgenic and wild-type mice equally well against lethal challenge with Streptococcus pneumoniae, an encapsulated Gram-positive bacterium known to require Ab-mediated opsonization for clearance. While IgG responses are severely depressed in these mice, IgM titers are only modestly decreased. This fairly robust IgM response may be sufficient to protect against S. pneumoniae. Additionally, while total leukocyte numbers are decreased in these mice, neutrophil numbers are increased. This increase in number of neutrophils may compensate for the depressed IgG response, allowing adequate host defense during chronic stress.
Competitive Inhibition In Vivo and Skewing of the T Cell Repertoire of Antigen-Specific CTL Priming by an Anti-Peptide-MHC Monoclonal Antibody
Authors: Chung Doo Hyun , Belyakov Igor M. , Derby Michael A. , Wang Jian , Boyd Lisa F. , Berzofsky Jay A. , Margulies David H.
Published: April 2014

We have recently described a mAb, KP15, directed against the MHC-I/peptide molecular complex consisting of H-2Dd and a decamer peptide corresponding to residues 311–320 of the HIV IIIB envelope glycoprotein gp160. When administered at the time of primary immunization with a vaccinia virus vector encoding gp160, the mAb blocks the subsequent appearance of CD8+ CTL with specificity for the immunodominant Ag, P18-I10, presented by H-2Dd. This inhibition is specific for this particular peptide Ag; another H-2Dd-restricted gp160 encoded epitope from a different HIV strain is not affected, and an H-2Ld-restricted epitope encoded by the viral vector is also not affected. Using functional assays and specific immunofluorescent staining with multivalent, labeled H-2Dd/P18-I10 complexes (tetramers), we have enumerated the effects of blocking of priming on the subsequent appearance, avidity, and TCR Vβ usage of Ag-specific CTL. Ab blocking skews the proportion of high avidity cells emerging from immunization. Surprisingly, Vβ7-bearing Ag-specific TCR are predominantly inhibited, while TCR of several other families studied are not affected. The ability of a specific MHC/peptide mAb to inhibit and divert the CD8+ T cell response holds implications for vaccine design and approaches to modulate the immune response in autoimmunity.
Identification of New Epitopes from Four Different Tumor-Associated Antigens: Recognition of Naturally Processed Epitopes Correlates with HLA-A∗0201-Binding Affinity
Authors: Keogh Elissa , Fikes John , Southwood Scott , Celis Esteban , Chesnut Robert , Sette Alessandro
Published: April 2014

Forty-two wild-type and analogue peptides derived from p53, carcinoembryonic Ag, Her2/neu, and MAGE2/3 were screened for their capacity to induce CTLs, in vitro, capable of recognizing tumor target lines. All the peptides bound HLA-A*0201 and two or more additional A2 supertype alleles with an IC50 of 500 nM or less. A total of 20 of 22 wild-type and 9 of 12 single amino acid substitution analogues were found to be immunogenic in primary in vitro CTL induction assays, using normal PBMCs and GM-CSF/IL-4-induced dendritic cells. These results suggest that peripheral T cell tolerance does not prevent, in this system, induction of CTL responses against tumor-associated Ag peptides, and confirm that an HLA class I affinity of 500 nM or less is associated with CTL epitope immunogenicity. CTLs generated by 13 of 20 of the wild-type epitopes, 6 of 9 of the single, and 2 of 5 of the double substitution analogues tested recognized epitopes generated by endogenous processing of tumor-associated Ags and expressed by HLA-matched cancer cell lines. Further analysis revealed that recognition of naturally processed Ag was correlated with high HLA-A2.1-binding affinity (IC50 = 200 nM or less; p = 0.008), suggesting that high binding affinity epitopes are frequently generated and can be recognized as a result of natural Ag processing. These results have implications for the development of cancer vaccines, in particular, and for the process of epitope selection in general.
CD28 Signaling Augments Elk-1-Dependent Transcription at the c-fosGene During Antigen Stimulation
Authors: Li Wei , Whaley Carmella D. , Bonnevier Jody L. , Mondino Anna , Martin Molly E. , Aagaard-Tillery Kjersti M. , Mueller Daniel L.
Published: April 2014

Untransformed CD4+ Th1 cells stimulated with Ag and APC demonstrated a dependence on B7- and CD28-mediated costimulatory signals for the expression and function of AP-1 proteins. The induction of transactivation by the c-fos gene regulator Elk-1 mirrored this requirement for TCR and CD28 signal integration. c-Jun N-terminal kinase (JNK) (but not extracellular signal-regulated kinase or p38) protein kinase activity was similarly inhibited by neutralizing anti-B7 mAbs. Blockade of JNK protein kinase activity with SB 202190 prevented both Elk-1 transactivation and c-Fos induction. These results identify a unique role for B7 costimulatory molecules and CD28 in the activation of JNK during Ag stimulation in Th1 cells, and suggest that JNK regulates Elk-1 transactivation at the c-fos gene to promote the formation of AP-1 complexes important to IL-2 gene expression.
Functional Evidence That Conserved TCR CDRα3 Loop Docking Governs the Cross-Recognition of Closely Related Peptide:Class I Complexes
Authors: Messaoudi Ilhem , LeMaoult Joel , Metzner Beatrix M. , Miley Michael J. , Fremont Daved H. , Nikolich-Žugich Janko
Published: April 2014

The TCR recognizes its peptide:MHC (pMHC) ligand by assuming a diagonal orientation relative to the MHC helices, but it is unclear whether and to what degree individual TCRs exhibit docking variations when contacting similar pMHC complexes. We analyzed monospecific and cross-reactive recognition by diverse TCRs of an immunodominant HVH-1 glycoprotein B epitope (HSV-8p) bound to two closely related MHC class I molecules, H-2Kb and H-2Kbm8. Previous studies indicated that the pMHC portion likely to vary in conformation between the two complexes resided at the N-terminal part of the complex, adjacent to peptide residues 2–4 and the neighboring MHC side chains. We found that CTL clones sharing TCR β-chains exhibited disparate recognition patterns, whereas those with drastically different TCRβ-chains but sharing identical TCRα CDR3 loops displayed identical functional specificity. This suggested that the CDRα3 loop determines the TCR specificity in our model, the conclusion supported by modeling of the TCR over the actual HSV-8:Kb crystal structure. Importantly, these results indicate a remarkable conservation in CDRα3 positioning, and, therefore, in docking of diverse TCRαβ heterodimers onto variant peptide:class I complexes, implying a high degree of determinism in thymic selection and T cell activation.
Glucocorticoid Augmentation of Macrophage Capacity for Phagocytosis of Apoptotic Cells Is Associated with Reduced p130Cas Expression, Loss of Paxillin/pyk2 Phosphorylation, and High Levels of Active Rac
Authors: Giles Katherine M. , Ross Katherine , Rossi Adriano G. , Hotchin Neil A. , Haslett Christopher , Dransfield Ian
Published: April 2014

Phagocytic clearance of apoptotic granulocytes has a pivotal role in determining an inflammatory outcome, resolution or progression to a chronic state associated with development of fibrotic repair mechanisms, and/or autoimmune responses. In this study, we describe reprogramming of monocyte to macrophage differentiation by glucocorticoids, resulting in a marked augmentation of their capacity for phagocytosis of apoptotic neutrophils. This monocyte/macrophage phenotype was characterized by decreased phosphorylation, and therefore recruitment of paxillin and pyk2 to focal contacts and a down-regulation of p130Cas, a key adaptor molecule in integrin adhesion signaling. Glucocorticoid-treated cells also displayed higher levels of active Rac and cytoskeletal activity, which were mirrored by increases in phagocytic capability for apoptotic neutrophils. We propose that changes in the capacity for reorganization of cytoskeletal elements induced by glucocorticoids are essential for efficient phagocytic uptake of apoptotic cells.
Recombinant Adenovirus Coexpressing Covalent Peptide/MHC Class II Complex and B7-1: In Vitro and In Vivo Activation of Myelin Basic Protein-Specific T Cells
Authors: Chen Jiang , Huber Brigitte T. , Grand Richard J. , Li Wei
Published: April 2014

Previous studies have demonstrated that an MHC class II molecule with an antigenic peptide genetically fused to its β-chain is capable of presenting this peptide to CD4+ T cells. We hypothesized that covalent peptide/class II complex may direct the accessory molecules to exert their function specifically onto T cells in a TCR-guided fashion. To test this hypothesis, we generated several recombinant adenoviruses expressing covalent myelin basic protein peptide/I-Au complex (MBP1–11/I-Au) and the costimulatory molecule B7-1. Functional studies demonstrated that adenovirus-infected cells are capable of activating an MBP1–11-specific T cell hybridoma. Coexpression of the B7-1 molecule and MBP1–11/I-Au by the same adenovirus leads to synergy in T cell activation elicited by virus-infected cells. Furthermore, studies in syngeneic mice infected with the various adenoviruses revealed that MBP1–11-specific T cells are specifically activated by the coexpression of B7-1 and MBP1–11/I-Au in vivo. In conclusion, the coexpression of the covalent peptide/class II complex and accessory molecules by the same adenovirus provides a unique strategy to modulate the epitope-specific T cell response in a TCR-guided fashion. This approach may be applicable to investigate the roles of other accessory molecules in the engagement of the TCR class II molecule by substituting B7-1 with other accessory molecules in the recombinant adenovirus.
Enhanced Proliferation and Increased IFN-γ Production in T Cells by Signal Transduced Through TNF-Related Apoptosis-Inducing Ligand
Authors: Chou Ai-Hsiang , Tsai Hwei-Fang , Lin Ling-Li , Hsieh Shie-Liang , Hsu Ping-I , Hsu Ping-Ning
Published: April 2014

TNF-related apoptosis-inducing ligand (TRAIL, also called Apo2L), a novel member of TNF superfamily, induces apoptosis in transformed cell lines of diverse origin. TRAIL is expressed in most of the cells, and the expression is up-regulated in activated T cells. Four receptors for TRAIL have been identified, and there is complex interplay between TRAIL and TRAIL receptors in vivo. The actual biological function of TRAIL/TRAIL receptor is still not clear. Growing evidence has demonstrated that members of TNF superfamily transduce signals after engagement with their receptors. Cross-linking of TRAIL by plate-bound rTRAIL receptor, death receptor 4-Fc fusion protein enhanced T cell proliferation and increased IFN-γ production in conjunction with immobilized suboptimal anti-CD3 stimulation in mouse splenocytes. The increase of T cell proliferation by death receptor 4-Fc was dose dependent, and this effect could be blocked by soluble rTRAIL proteins, indicating the occurrence of reverse signaling through TRAIL on T cell. The enhanced secretion of IFN-γ mediated via TRAIL could be blocked by SB203580, a p38 mitogen-activated protein kinase-specific inhibitor. Thus, in addition to its role in inducing apoptosis by binding to the death receptors, TRAIL itself can enhance T cell proliferation after TCR engagement and signal the augmentation of IFN-γ secretion via a p38-dependent pathway. This provides another example of reverse signaling by a member of TNF superfamily. In conclusion, our data suggest that TRAIL can itself transduce a reverse signal, and this may shed light on the biological function of TRAIL.
Antibody-Independent Antiviral Function of Memory CD4+ T Cells In Vivo Requires Regulatory Signals from CD8+ Effector T Cells
Authors: Zhong Weimin , Roberts Alan D. , Woodland David L.
Published: April 2014

Previous studies have shown that vaccine-primed CD4+ T cells can mediate accelerated clearance of respiratory virus infection. However, the relative contributions of Ab and CD8+ T cells, and the mechanism of viral clearance, are poorly understood. Here we show that control of a Sendai virus infection by primed CD4+ T cells is mediated through the production of IFN-γ and does not depend on Ab. This effect is critically dependent on CD8+ cells for the expansion of CD4+ T cells in the lymph nodes and the recruitment of memory CD4+ T cells to the lungs. Passive transfer of a CD8+ T cell supernatant into CD8+ T cell-depleted, hemagglutinin-neuraminidase (HN)421–436-immune μMT mice substantially restored the virus-specific memory CD4+ response and enhanced viral control in the lung. Together, the data demonstrate for the first time that in vivo primed CD4+ T cells have the capacity to control a respiratory virus infection in the lung by an Ab-independent mechanism, provided that CD8+ T cell “help” in the form of soluble factor(s) is available during the virus infection. These studies highlight the importance of synergistic interactions between CD4+ and CD8+ T cell subsets in the generation of optimal antiviral immunity.
Virally Infected Hepatocytes Are Resistant to Perforin-Dependent CTL Effector Mechanisms
Authors: Kafrouni Michel I. , Brown Geri R. , Thiele Dwain L.
Published: April 2014

Cell-mediated cytotoxicity plays an important role in the clearance of noncytopathic viruses from infected tissues. Perforin-dependent cytotoxic mechanisms have been noted to play an important role in the clearance of infections from multiple extrahepatic organs. In contrast, mice with defects in the Fas/Fas ligand (FasL)-mediated cytotoxicity pathway exhibit delayed clearance of adenovirus from the liver without apparent delay in the clearance of viral infections from extrahepatic organs. The present studies examined the role of cytotoxic effector mechanisms in intrahepatic immune responses to a replication-defective, recombinant β-galactosidase-encoding adenovirus (AdCMV-lacZ). Delayed clearance of AdCMV-lacZ from the livers of FasL-defective B6.gld mice, but not perforin-deficient B6.pfp−/− mice, was noted despite no significant differences in initial hepatic CD8+ T cell IFN-γ or TNF responses or in activation of intrahepatic cytotoxic lymphocytes cells capable of killing AdCMV-lacZ-infected fibroblast targets. In contrast, AdCMV-lacZ-infected hepatocyte targets were far more sensitive to killing by intrahepatic cytotoxic lymphocytes from B6.pfp−/− than from B6.gld mice, and residual levels of virus-specific killing of hepatocyte targets by FasL-defective B6.gld CTL were blocked by TNF inhibition. These results suggest that inherent resistance of hepatocytes to cytotoxicity mediated by perforin-dependent mechanisms leaves Fas/FasL-dependent, cell-mediated cytotoxicity as the major pathway for CTL-mediated killing of virally infected hepatocytes and accounts for the more prominent role of perforin-independent anti-viral mechanisms in immune responses in the liver.
Autoantigen Glycoprotein 70 Expression Is Regulated by a Single Locus, Which Acts as a Checkpoint for Pathogenic Anti-Glycoprotein 70 Autoantibody Production and Hence for the Corresponding Development of Severe Nephritis, in Lupus-Prone BXSB Mice1
Authors: Haywood Michelle E. K. , Vyse Timothy J. , McDermott Aileen , Thompson E. Mary , Ida Akinori , Walport Mark J. , Izui Shozo , Morley Bernard J.
Published: April 2014

Retroviral envelope glycoprotein gp70 is present in the sera of immunologically normal and autoimmune-prone strains of mice. However, only lupus-prone mice spontaneously develop gp70-anti-gp70 immune complexes (gp70IC), and these have been implicated in the development of nephritis. We investigated the genetic factors that affect the production of both free serum gp70 and gp70IC in the lupus-prone BXSB mouse strain by analyzing (BXSB × (C57BL/10 × BXSB)F1)- and (C57BL/10 × (C57BL/10 × BXSB)F1)-backcrossed male mice. Production of gp70 mapped to a single major locus located on chromosome 13 (Bxs6) with a maximum log likelihood of the odds of 36.7 (p = 1.6 × 10−38). The level of gp70IC was highly dependent on Bxs6-related gp70 production, and high titer autoantibody production only occurred when serum gp70 levels were greater than a threshold value of ∼4.0 μg/ml. The subdivision of the (BXSB × (C57BL/10 × BXSB)F1)-backcrossed mice into those homozygous or heterozygous for Bxs6 enabled a remarkable association to be observed between high levels of gp70IC and severe nephritis in the Bxs6 homozygote population. A further mapping study in these two subgroups identified a previously unrecognized interval associated with the production of autoantibodies.
MHC Class I-Restricted Determinants on the Glutamic Acid Decarboxylase 65 Molecule Induce Spontaneous CTL Activity
Authors: Quinn Anthony , McInerney Marcia F. , Sercarz Eli E.
Published: April 2014

CD4+ T cell responses to glutamic acid decarboxylase (GAD65) spontaneously arise in nonobese diabetic (NOD) mice before the onset of insulin-dependent diabetes mellitus (IDDM) and may be critical to the pathogenic process. However, since both CD4+ and CD8+ T cells are involved in autoimmune diabetes, we sought to determine whether GAD65-specific CD8+ T cells were also present in prediabetic NOD mice and contribute to IDDM. To refine the analysis, putative Kd-binding determinants that were proximal to previously described dominant Th determinants (206–220 and 524–543) were examined for their ability to elicit cytolytic activity in young NOD mice. Naive NOD spleen cells stimulated with GAD65 peptides 206–214 (p206) and 546–554 (p546) produced IFN-γ and showed Ag-specific CTL responses against targets pulsed with homologous peptide. Conversely, several GAD peptides distal to the Th determinants, and control Kd-binding peptides did not induce similar responses. Spontaneous CTL responses to p206 and p546 were mediated by CD8+ T cells that are capable of lysing GAD65-expressing target cells, and p546-specific T cells transferred insulitis to NOD.scid mice. Young NOD mice pretreated with p206 and p546 showed reduced CTL responses to homologous peptides and a delay in the onset of IDDM. Thus, MHC class I-restricted responses to GAD65 may provide an inflammatory focus for the generation of islet-specific pathogenesis and β cell destruction. This report reveals a potential therapeutic role for MHC class I-restricted peptides in treating autoimmune disease and revisits the notion that the CD4- and CD8-inducing determinants on some molecules may benefit from a proximal relationship.
Dendritic Cells (DCs) in Rheumatoid Arthritis (RA): Progenitor Cells and Soluble Factors Contained in RA Synovial Fluid Yield a Subset of Myeloid DCs That Preferentially Activate Th1 Inflammatory-Type Responses
Authors: Santiago-Schwarz Frances , Anand Prachi , Liu Sean , Carsons Steven E.
Published: April 2014

There is evidence that mature dendritic cells (DCs) present in the rheumatoid arthritis (RA) joint mediate immunopathology in RA. In this study, we indicate that early myeloid progenitors for DCs and DC growth factors existing in RA synovial fluid (SF) are also likely participants in the RA disease process. A fraction of cells lacking markers associated with mature DCs or DC precursors and enriched in CD34negative myeloid progenitors was isolated from RA SF. These cells proliferated extensively when cultured in vitro with cytokines that promote the growth of myeloid DCs (GM-CSF/TNF/stem cell factor/IL-4) and, to a lesser degree, when cultured with monocyte/granulocyte-restricted growth factors (M-CSF/GM-CSF). Mature DCs derived from RA SF progenitors with CD14-DC cytokines known to be prevalent in the inflamed RA joint (GM-CSF/TNF/stem cell factor/IL-13) were potent stimulators of allogeneic T cells and inflammatory-type Th1 responses and included CD14-DC subtypes. Cell-free RA SF facilitated DC maturation from myeloid progenitors, providing direct evidence that the inflamed RA joint environment instructs DC growth. Enhanced development of CD14-derived DCs was correlated with the presence of soluble TNFR (p55), raising the possibility that soluble TNFR also regulate CD14-derived DC growth in vivo. SF from patients with osteoarthritis contained neither myeloid DC progenitors nor DC growth factors. The existence of DC progenitors and myeloid DC growth factors in RA SF supports the concept that RA SF may be a reservoir for joint-associated DCs and reveals a compelling mechanism for the amplification and perpetuation of DC-driven responses in the RA joint, including inflammatory-type Th1 responses.
Cross-Presentation by Dendritic Cells of Tumor Antigen Expressed in Apoptotic Recombinant Canarypox Virus-Infected Dendritic Cells
Authors: Motta Iris , André Fabrice , Lim Annick , Tartaglia James , Cox William I. , Zitvogel Laurence , Angevin Eric , Kourilsky Philippe
Published: April 2014

We have investigated the possible usefulness of recombinant canarypox virus (ALVAC) encoding the melanoma-associated Ag, Melan-A/MART-1 (MART-1), in cancer immunotherapy, using a dendritic cell (DC)-based approach. ALVAC MART-1-infected DC express, and are able to process and present, the Ag coded by the viral vector. One consistent feature of infection by ALVAC is that these viruses induce apoptosis, and we show cross-presentation of Ag when uninfected DC are cocultured with ALVAC MART-1-infected DC. Uptake of apoptotic virally infected DC by uninfected DC and subsequent expression of tumor Ag in the latter were verified by flow cytometry analysis, image cytometry, and confocal microscopy. Functional activity was monitored in vitro by the stimulation of a MART-1-specific cytotoxic T cell clone. Heightened efficiency in Ag presentation is evidenced in the 2- to 3-fold increase in IFN-γ production by the T cell clone, as compared with the ALVAC-infected DC alone. Cocultures of ALVAC MART-1-infected and uninfected DC are able to induce MART-1-specific T cell immune responses, as assessed by HLA class I/peptide tetramer binding, IFN-γ ELISPOT assays, and cytotoxicity tests. Overall, our data indicate that DC infected with recombinant canarypox viruses may represent an efficient presentation platform for tumor Ags, which can be exploited in clinical studies.
Cutting Edge: Bacterial Flagellin Activates Basolaterally Expressed TLR5 to Induce Epithelial Proinflammatory Gene Expression
Authors: Gewirtz Andrew T. , Navas Tony A. , Lyons Sean , Godowski Paul J. , Madara James L.
Published: April 2014

Flagellin, the structural component of bacterial flagella, is secreted by pathogenic and commensal bacteria. Flagellin activates proinflammatory gene expression in intestinal epithelia. However, only flagellin that contacts basolateral epithelial surfaces is proinflammatory; apical flagellin has no effect. Pathogenic Salmonella, but not commensal Escherichia coli, translocate flagellin across epithelia, thus activating epithelial proinflammatory gene expression. Investigating how epithelia detect flagellin revealed that cell surface expression of Toll-like receptor 5 (TLR5) conferred NF-κB gene expression in response to flagellin. The response depended on both extracellular leucine-rich repeats and intracellular Toll/IL-1R homology region of TLR5 as well as the adaptor protein MyD88. Furthermore, immunolocalization and cell surface-selective biotinylation revealed that TLR5 is expressed exclusively on the basolateral surface of intestinal epithelia, thus providing a molecular basis for the polarity of this innate immune response. Thus, detection of flagellin by basolateral TLR5 mediates epithelial-driven inflammatory responses to Salmonella.
Signaling Through TNF Receptor p55 in TNF-α-Deficient Mice Alters the CXCL13/CCL19/CCL21 Ratio in the Spleen and Induces Maturation and Migration of Anergic B Cells into the B Cell Follicle
Authors: Mandik-Nayak Laura , Huang Guangming , Sheehan Kathleen C. F. , Erikson Jan , Chaplin David D.
Published: April 2014

The organization of secondary lymphoid tissues into distinct T and B cell compartments supports proper regulation of an immune response to foreign Ags. In the splenic white pulp, this compartmentalization is also thought to be important in the maintenance of B cell tolerance. Using lymphotoxin-α-(LT-α)-, TNF-α-, or TNFRp55-deficient mice, all with disrupted splenic architecture, we tested whether normal T/B segregation and/or intact follicular structure are necessary for the maintenance of anti-dsDNA B cell anergy. This study demonstrates that anti-dsDNA B cells remain tolerant in LT-α−/−, TNF-α−/−, and TNFRp55−/− mice; however, TNF-α or a TNF-α-dependent factor is required for their characteristic positioning to the T/B interface. Providing a TNF-α signal in TNF-α−/− mice by systemic administration of an agonist anti-TNFRp55 mAb induces the maturation of the anti-dsDNA B cells and their movement away from the T cell area toward the B cell area. Additionally, the agonist Ab induces changes in the follicular environment, including FDC clustering, up-regulation of the CXC chemokine ligand CXCL13, and down-regulation of the CC chemokine ligands CCL19 and CCL21. Therefore, this study suggests that a balance between B and T cell tropic chemokine signals may be an important mechanism for positioning anergic B cells at the T/B interface of the splenic white pulp.
Regulatory T Cells Induced by 1α,25-Dihydroxyvitamin D3 and Mycophenolate Mofetil Treatment Mediate Transplantation Tolerance
Authors: Gregori Silvia , Casorati Mara , Amuchastegui Susana , Smiroldo Simona , Davalli Alberto M. , Adorini Luciano
Published: April 2014

1α,25-Dihydroxyvitamin D3, the active form of vitamin D3, and mycophenolate mofetil, a selective inhibitor of T and B cell proliferation, modulate APC function and induce dendritic cells (DCs) with a tolerogenic phenotype. Here we show that a short treatment with these agents induces tolerance to fully mismatched mouse islet allografts that is stable to challenge with donor-type spleen cells and allows acceptance of donor-type vascularized heart grafts. Peritransplant macrophages and DCs from tolerant mice express down-regulated CD40, CD80, and CD86 costimulatory molecules. In addition, DCs from the graft area of tolerant mice secrete, upon stimulation with CD4+ cells, 10-fold lower levels of IL-12 compared with DCs from acutely rejecting mice, and induce a CD4+ T cell response characterized by selective abrogation of IFN-γ production. CD4+ but not CD8+ or class II+ cells from tolerant mice, transferred into naive syngeneic recipients, prevent rejection of donor-type islet grafts. Graft acceptance is associated with impaired development of IFN-γ-producing type 1 CD4+ and CD8+ cells and an increased percentage of CD4+CD25+ regulatory cells expressing CD152 in the spleen and in the transplant-draining lymph node. Transfer of CD4+CD25+ cells from tolerant but not naive mice protects 100% of the syngeneic recipients from islet allograft rejection. These results demonstrate that a short treatment with immunosuppressive agents, such as 1α,25-dihydroxyvitamin D3/mycophenolate mofetil, induces tolerance to islet allografts associated with an increased frequency of CD4+CD25+ regulatory cells that can adoptively transfer transplantation tolerance.
Circulating Human B Cells That Express Surrogate Light Chains Display a Unique Antibody Repertoire
Authors: Meffre Eric , Chiorazzi Michael , Nussenzweig Michel C.
Published: April 2014

Circulating human B cells that coexpress V-preB and conventional L chains (V-preB+L+ B cells) are a recently described subset of B cells that express Abs with features of self-reactivity. Initial analysis of V-preB+L+ B cells was limited to Ig-κ and to the small, underused VH5 family. To determine whether Abs commonly expressed by V-preB+L+ B cells show similar features, we analyzed Ig H chains from three highly expressed VH families, VH1, VH3, and VH4, and Ig-λ. We find that VH1 and VH3 Abs expressed by V-preB+L+ B cells resemble VH5 in that they display increased JH6 use, long CDR3s, and an increased frequency of D-D fusions. Abs in all three of these VH families also show skewed D reading frame use resulting in predominance of hydrophobic amino acids, which are counterselected in conventional B cells. Like Ig-κ genes, the Ig-λ genes in V-preB+L+ B cells show long CDR3s, but they differ from Ig-κ genes in that they display no evidence of receptor editing. We conclude that a large number of H and L chain Abs expressed by V-preB+L+ B cells display features associated with self-reactive Abs.
Catalytic Subunit of Protein Kinase A Is an Interacting Partner of the Inflammation-Responsive Transcription Factor Serum Amyloid A-Activating Factor-1
Authors: Ray Bimal K. , Chen Jing , Ray Alpana
Published: April 2014

Serum amyloid A-activating factor-1 (SAF-1) is a zinc finger transcription factor that is activated by many mediators of inflammation including IL-1, IL-6, and bacterial LPS. However, the mechanism of activation is not fully understood. To identify possible activation partners for SAF-1, we used a yeast two-hybrid system that detected interaction between the catalytic subunit of cyclic AMP-dependent protein kinase (PKA-Cα) and SAF-1. Immunofluorescence and combined immunoprecipitation-Western blot analyses revealed colocalization and interaction between SAF-1 and PKA-Cα. In vivo evidence of SAF-1 and PKA-Cα interaction was further revealed by coimmunoprecipitation of these two proteins in cAMP-activated liver cells. We further show that SAF-1 is phosphorylated in vitro by PKA-Cα and that addition of cAMP markedly induces in vivo phosphorylation of SAF-1 and transcription of SAF-regulated reporter genes. These results showed that SAF1-PKA-Cα interaction is involved in functional activation of SAF-1.