bluuebunny/crossref_metadata_2025_split huggingface dataset:
Progressive Surface B Cell Antigen Receptor Down-Regulation Accompanies Efficient Development of Antinuclear Antigen B Cells to Mature, Follicular Phenotype
Authors: Heltemes-Harris Lynn , Liu Xiaohe , Manser Tim 
Published: April 2014

AbstractPrevious studies have suggested that B cell Ag receptor (BCR) down-regulation by potentially pathological autoreactive B cells is associated with pathways leading to developmental arrest and receptor editing, or anergy. In this study we compare the primary development of B cells in two strains of mice expressing transgenic BCRs that differ by a single amino acid substitution that substantially increases reactivity for nuclear autoantigens such as DNA. Surprisingly, we find that both BCRs promote efficient development to mature follicular phenotype, but the strongly autoreactive BCR fails to promote marginal zone B cell development. The follicular B cells expressing the strongly autoreactive BCR do not appear to be anergic, as they robustly respond to polyclonal stimuli in vitro, are not short-lived, and can participate in germinal center reactions. Strikingly however, substantial and progressive down-modulation of surface IgM and IgD takes place throughout their primary development in the BM and periphery. We propose that BCR-autoantigen interactions regulate this pathway, resulting in reduced cellular avidity for autoantigens. This process of “learned ignorance” could allow autoreactive B cells access to the foreign Ag-driven memory B cell response, during which their self-reactivity would be attenuated by somatic hypermutation and selection in the germinal center.
Dendritic Cell Immunization Route Determines CD8+ T Cell Trafficking to Inflamed Skin: Role for Tissue Microenvironment and Dendritic Cells in Establishment of T Cell-Homing Subsets
Authors: Dudda Jan C. , Simon Jan C. , Martin Stefan 
Published: April 2014

Abstract
The effector/memory T cell pool branches in homing subsets selectively trafficking to organs such as gut or skin. Little is known about the critical factors in the generation of skin-homing CD8+ T cells, although they are crucial effectors in skin-restricted immune responses such as contact hypersensitivity and melanoma defense. In this study, we show that intracutaneous, but not i.v. injection of bone marrow-derived dendritic cells induced skin-homing CD8+ T cells with up-regulated E-selectin ligand expression and effector function in contact hypersensitivity. The skin-homing potential and E-selectin ligand expression remained stable in memory phase without further Ag contact. In contrast, i.p. injection induced T cells expressing the gut-homing integrin α4β7. Although differential expression of these adhesion molecules was strictly associated with the immunization route, the postulated skin-homing marker CCR4 was transiently up-regulated in all conditions. Interestingly, dendritic cells from different tissues effectively induced the corresponding homing markers on T cells in vitro. Our results suggest a crucial role for the tissue microenvironment and dendritic cells in the instruction of T cells for tissue-selective homing and demonstrate that Langerhans cells are specialized to target T cells to inflamed skin.
MHC Class II Molecules Play a Role in the Selection of Autoreactive Class I-Restricted CD8 T Cells That Are Essential Contributors to Type 1 Diabetes Development in Nonobese Diabetic Mice
Authors: Serreze David V. , Holl T. Matthew , Marron Michele P. , Graser Robert T. , Johnson Ellis A. , Choisy-Rossi Caroline , Slattery Robyn M. , Lieberman Scott M. , DiLorenzo Teresa P. 
Published: April 2014

Abstract
Development of autoreactive CD4 T cells contributing to type 1 diabetes (T1D) in both humans and nonobese diabetic (NOD) mice is either promoted or dominantly inhibited by particular MHC class II variants. In addition, it is now clear that when co-expressed with other susceptibility genes, some common MHC class I variants aberrantly mediate autoreactive CD8 T cell responses also essential to T1D development. However, it was unknown whether the development of diabetogenic CD8 T cells could also be dominantly inhibited by particular MHC variants. We addressed this issue by crossing NOD mice transgenically expressing the TCR from the diabetogenic CD8 T cell clone AI4 with NOD stocks congenic for MHC haplotypes that dominantly inhibit T1D. High numbers of functional AI4 T cells only developed in controls homozygously expressing NOD-derived H2g7 molecules. In contrast, heterozygous expression of some MHC haplotypes conferring T1D resistance anergized AI4 T cells through decreased TCR (H2b) or CD8 expression (H2q). Most interestingly, while AI4 T cells exert a class I-restricted effector function, H2nb1 MHC class II molecules can contribute to their negative selection. These findings provide insights to how particular MHC class I and class II variants interactively regulate the development of diabetogenic T cells and the TCR promiscuity of such autoreactive effectors.
Innate Immune Discrimination of Apoptotic Cells: Repression of Proinflammatory Macrophage Transcription Is Coupled Directly to Specific Recognition
Authors: Cvetanovic Marija , Ucker David S. 
Published: April 2014

Abstract
Physiological cell death is a process the purpose of which is the elimination of functionally inappropriate cells in a manner that does not elicit an inflammatory response. We have shown previously that the ability of apoptotic corpses to be recognized by macrophages and to modulate the proinflammatory responses of those cells represents paradoxically a gain-of-function acquired during the physiological cell death process. Cells that die pathologically (that is, necrotic vs apoptotic corpses) also are recognized by macrophages but do not down-regulate macrophage inflammatory responses; the recognition of these two classes of native dying cells occurs via distinct and noncompeting mechanisms. We have examined the apoptotic modulation of proinflammatory cytokine gene transcription in macrophages (by real-time RT-PCR analysis) and the corresponding modulation of transcriptional activators (by transcriptional reporter analyses). Our data demonstrate that apoptotic cells target the proinflammatory transcriptional machinery of macrophages with which they interact, without apparent effect on proximal steps of Toll-like receptor signaling. The modulatory activity of the corpse is manifest as an immediate-early inhibition of proinflammatory cytokine gene transcription, and is exerted directly upon binding to the macrophage, independent of subsequent engulfment and soluble factor involvement. Recognition and inflammatory modulation represent key elements of an innate immune response that discriminates live from effete cells, and without regard to self.
Dual Role of CCR2 during Initiation and Progression of Collagen-Induced Arthritis: Evidence for Regulatory Activity of CCR2+ T Cells
Authors: Brühl Hilke , Cihak Josef , Schneider Martin A. , Plachý Jiří , Rupp Tamara , Wenzel Isabell , Shakarami Mehdi , Milz Stefan , Ellwart Joachim W. , Stangassinger Manfred , Schlöndorff Detlef , Mack Matthias 
Published: April 2014

Abstract
Chemokines play an important role in the recruitment of leukocytes and have recently been shown to also attract regulatory T cells. Using blocking mAbs, we analyzed the role of the chemokine receptor CCR2 during initiation and progression of collagen-induced arthritis in mice. Blockade of CCR2 from days 0 to 15 markedly improved clinical signs of arthritis and histological scores measuring leukocyte infiltration, synovial hyperplasia, and bone and cartilage erosion. CCR2 blockade during disease initiation significantly reduced plasma titers of collagen Abs in vivo. In vitro CCR2 blockade also interfered with collagen-specific activation and proliferation of T cells. Surprisingly, CCR2 blockade from days 21 to 36 markedly aggravated clinical and histological signs of arthritis and increased the humoral immune response against collagen. We show that CCR2 is expressed on regulatory T cells. Purified CCR2+ T cells are fully anergic toward polyclonal and collagen-specific activation and potently suppress activation of other T and B cells. The subpopulation of CCR2+ CD25+ regulatory T cells increases ∼5-fold in the progression phase, while CCR2 expression on other leukocyte populations remains unchanged. These findings identify CCR2+ T cells as regulatory T cells and indicate that CCR2 also plays an important role in down-modulating an inflammatory response.
NKp44 Triggers NK Cell Activation through DAP12 Association That Is Not Influenced by a Putative Cytoplasmic Inhibitory Sequence
Authors: Campbell Kerry S. , Yusa Sei-ichi , Kikuchi-Maki Akiko , Catina Tracey L. 
Published: April 2014

Abstract
NKp44 (NCR2) is a member of the natural cytotoxicity receptor (NCR) family that is expressed on activated human NK cells. We dissected structural attributes of NKp44 to determine their contributions to receptor function. Our results demonstrate that surface expression and NK cell activation by NKp44 is mediated through noncovalent association with the immunoreceptor tyrosine-based activation motif-containing protein, DAP12. Physical linkage to DAP12 requires lysine-183 in the NKp44 transmembrane domain. Intriguingly, the cytoplasmic domain of NKp44 also contains a sequence that matches the immunoreceptor tyrosine-based inhibitory motif (ITIM) consensus. By expressing a chimeric receptor in an NK-like cell line, we found that this ITIM-like motif from NKp44 lacks inhibitory capacity in a redirected cytotoxicity assay. The NKp44 cytoplasmic tyrosine was efficiently phosphorylated in the chimeric receptor upon treating the cells with pervanadate, but it was unable to recruit ITIM-binding negative effector phosphatases. We also generated NK-like cell lines expressing epitope-tagged wild-type or tyrosine to phenylalanine mutant (Y238F) versions of NKp44 and compared their capacities to induce activation marker expression, promote IFN-γ production, or stimulate target cell cytotoxicity. We did not detect any tyrosine-dependent reduction or enhancement of NK cell activation through wild-type vs. Y238F mutant NKp44. Finally, the cytoplasmic tyrosine-based sequence did not provide a docking site for the AP-2 clathrin adaptor, nor did it potentiate receptor internalization. In summary, all activating properties and surface expression of NKp44 are mediated through its association with DAP12, and the putative ITIM in the NKp44 cytoplasmic domain does not appear to attenuate activating function.
TCR Vaccines against a Murine T Cell Lymphoma: A Primary Role for Antibodies of the IgG2c Class in Tumor Protection
Authors: Lambert Stacie L. , Okada Craig Y. , Levy Ronald 
Published: April 2014

Abstract
Tumor-associated proteins can act as effective immunotherapeutic targets. Immunization with tumor TCR protein conjugated to the immunogenic protein keyhole limpet hemocyanin (KLH) protects mice from tumor challenge with the murine T cell lymphoma C6VL. The immune mechanisms responsible for this tumor protection are of interest for designing more effective vaccine strategies. Previous studies using depletion experiments had suggested a CD8-mediated component of protection induced by TCR-KLH vaccines. In this study we used CD8α knockout, μMT, and FcγR knockout mice to investigate the relative roles of CD8+ T cells and Ab in protective immunity induced by TCR-KLH immunization. We found that CD8+ T cells are not required for tumor protection, although they may contribute to protection. Vaccine-induced Abs are sufficient to mediate protection against this murine T cell lymphoma through an FcR-dependent mechanism. This was confirmed with Ab transfers, which protect challenged mice. Additionally, recombinase-activating gene 1−/− splenocytes can mediate Ab-dependent cellular cytotoxicity against this tumor in the presence of bound anti-TCR Abs. IFN-γ knockout mice demonstrated a requirement for IFN-γ, probably via generation of IgG2c Abs, in vaccine-induced tumor protection. IFN-γ knockout mice were not protected by immunization and had a severe impairment in IgG2c Ab production in response to immunization. Although mock-depleted anti-TCR Abs could transfer tumor protection, IgG2c-deficient anti-TCR Abs were unable to transfer tumor protection to wild-type mice. These results suggest that TCR-KLH vaccine-induced tumor protection in the C6VL system is primarily attributable to the induction of IgG2c Abs and humoral immunity.
A Switch in Costimulation from CD28 to 4-1BB during Primary versus Secondary CD8 T Cell Response to Influenza In Vivo
Authors: Bertram Edward M. , Dawicki Wojciech , Sedgmen Bradley , Bramson Jonathan L. , Lynch David H. , Watts Tania H. 
Published: April 2014

Abstract
4-1BBL−/− mice exhibit normal primary CD8 T cell responses to influenza virus, but show decreased CD8 T cell numbers late in the primary response as well as decreased secondary responses. In contrast, CD28−/− mice are defective in initial CD8 T cell expansion. Using agonistic anti-4-1BB Ab to replace the CD28 or 4-1BB signal, we examined the timing of the required signals for CD28 vs 4-1BB costimulation. A single dose of agonistic anti-4-1BB Ab added only during priming restores the secondary CD8 T cell response in CD28−/− mice. Once the T cell numbers in the primary response reach a minimum threshold, a full secondary response is achieved even in the absence of CD28. In contrast, anti-4-1BB added during priming fails to correct the defective secondary response in 4-1BBL−/− mice, whereas addition of anti-4-1BB during challenge fully restores this response. Thus, there is a switch in costimulatory requirement from CD28 to 4-1BB during primary vs recall responses. Adoptive transfer studies show that T cells primed in 4-1BBL−/− or wild-type mice are equally capable of re-expansion when rechallenged in wild-type mice. These studies rule out a model in which signals delivered through 4-1BB during priming program the T cells to give a full recall response and suggest that 4-1BB-4-1BBL interactions take place at later stages in the immune response. The results indicate that anti-4-1BB or 4-1BBL therapy will be most effective during the boost phase of a prime-boost vaccination strategy.
Antigen-Specific Inhibition of CD8+ T Cell Response by Immature Myeloid Cells in Cancer Is Mediated by Reactive Oxygen Species
Authors: Kusmartsev Sergei , Nefedova Yulia , Yoder Daniel , Gabrilovich Dmitry I. 
Published: April 2014

Abstract
Tumor growth is associated with the accumulation of immature myeloid cells (ImC), which in mice are characterized by the expression of Gr-1 and CD11b markers. These cells suppress Ag-specific CD8+ T cells via direct cell-cell contact. However, the mechanism of immunosuppressive activity of tumor-derived ImC remains unclear. In this study we analyzed the function of ImC isolated from tumor-free control and tumor-bearing mice. Only ImC isolated from tumor-bearing mice, not those from their control counterparts, were able to inhibit the Ag-specific response of CD8+ T cells. ImC obtained from tumor-bearing mice had significantly higher levels of reactive oxygen species (ROS) than ImC isolated from tumor-free animals. Accumulation of H2O2, but not superoxide or NO, was a major contributor to this increased pool of ROS. It appears that arginase activity played an important role in H2O2 accumulation in these cells. Inhibition of ROS in ImC completely abrogated the inhibitory effect of these cells on T cells, indicating that ImC generated in tumor-bearing hosts suppress the CD8+ T cell response via production of ROS. Interaction of ImC with Ag-specific T cells in the presence of specific Ags resulted in a significant increase in ROS production compared with control Ags. That increase was independent of IFN-γ production by T cells, but was mediated by integrins CD11b, CD18, and CD29. Blocking of these integrins with specific Abs abrogated ROS production and ImC-mediated suppression of CD8+ T cell responses. This study demonstrates a new mechanism of Ag-specific T cell inhibition mediated by ROS produced by ImCs in cancer.
Cutting Edge: Distinct TCR- and CD28-Derived Signals Regulate CD95L, Bcl-xL, and the Survival of Primary T Cells
Authors: Kerstan Andreas , Hünig Thomas 
Published: April 2014

AbstractTCR-driven clonal expansion of T cells is limited by activation-induced cell death through CD95/CD95L interactions. This cell-contact dependent mechanism is attenuated by costimulation through CD28. Here, we show that primary rat lymph node T cells activated by “superagonistic” CD28-specific mAb, which do not require TCR-engagement for full T cell activation, do not up-regulate CD95L. CD28 superagonist activated T cells are highly resistant to artificial CD95 cross-linking, and display a marked up-regulation of the survival factor Bcl-xL. Consistently, NF-κB factors, known to promote Bcl-xL transcription, are strongly activated by superagonistic CD28 mAb stimulation. In contrast, a weaker induction of NFAT, which positively regulates the CD95L gene, in CD28 activated cells as compared with TCR- or TCR/CD28-stimulated cells was observed. Thus, by recruiting the mitogenic activity of CD28 in the absence of TCR engagement, the anti-apoptotic signals provided by costimulation are revealed without interfering proapoptotic effects induced by TCR stimulation.
Mature Human Thymocytes Migrate on Laminin-5 with Activation of Metalloproteinase-14 and Cleavage of CD44
Authors: Vivinus-Nebot Mylène , Rousselle Patricia , Breittmayer Jean-Philippe , Cenciarini Claire , Berrih-Aknin Sonia , Spong Suzanne , Nokelainen Pasi , Cottrez Françoise , Marinkovich M. Peter , Bernard Alain 
Published: April 2014

AbstractWe have previously shown that laminin-5 is expressed in the human thymic medulla, in which mature thymocytes are located. We now report that laminin-5 promotes migration of mature medullary thymocytes, whereas it has no effect on cortical immature thymocytes. Migration was inhibited by blocking mAbs directed against laminin-5 integrin receptors and by inhibitors of metalloproteinases. Interactions of thymocytes with laminin-5 induced a strong up-regulation of active metalloproteinase-14. However, we found that thymocytes did not cleave the laminin-5 γ2 chain, suggesting that they do not use the same pathway as epithelial cells to migrate on laminin-5. Interactions of thymocytes with laminin-5 also induced the release of a soluble fragment of CD44 cell surface molecule. Moreover, CD44-rich supernatants induced thymocyte migration in contrast with supernatants depleted in CD44 by immunoadsorption. CD44 cleavage was recently reported to be due to metalloproteinase-14 activation and led to increased migration in cancer cells. Thus, in this study, we show that laminin-5 promotes human mature thymocyte migration in vitro via a multimolecular mechanism involving laminin-5 integrin receptors, metalloproteinase-14 and CD44. These data suggest that, in vivo, laminin-5 may function in the migration of mature thymocytes within the medulla and be part of the thymic emigration process.
CCL17 and IL-10 as Effectors That Enable Alternatively Activated Macrophages to Inhibit the Generation of Classically Activated Macrophages
Authors: Katakura Tatsushi , Miyazaki Masaru , Kobayashi Makiko , Herndon David N. , Suzuki Fujio 
Published: April 2014

AbstractClassically activated macrophages (CAMφ) have been described as a major effector cell on the host’s innate immunities. However, CAMφ are not generated in immunocompromised hosts whose alternatively activated macrophages (AAMφ) predominate. In this study, the mechanism by which AAMφ suppress the ability of resident macrophages (RMφ) to generate CAMφ was investigated. AAMφ were isolated from peritoneal exudates of mice 2 days after third-degree thermal injuries affecting 15% total body surface area. CAMφ were generated from RMφ (peritoneal Mφ from normal mice) through stimulation with CpG DNA, a typical CAMφ inducer. RMφ did not polarize to CAMφ when they were cultured with AAMφ in a dual-chamber Transwell even when supplemented with CpG DNA. In addition, RMφ stimulated with CpG DNA did not convert to CAMφ when they were cultured with the culture fluids of AAMφ (AAMφ Culture-Sup). AAMφ Culture-Sup contained IL-6, IL-10, CCL17, PGE2, and TGF-β. Among these, CCL17 and IL-10 inhibited CAMφ generation. The ability of AAMφ Culture-Sup to inhibit CAMφ generation was eliminated when the Culture-Sup was treated with a mixture of mAbs directed against CCL17 and IL-10. These results indicate that CCL17 and IL-10 released from AAMφ inhibit CAMφ generation from RMφ stimulated with CpG DNA.
Lck Is Required for Activation-Induced T Cell Death after TCR Ligation with Partial Agonists
Authors: Yu Xue-Zhong , Levin Steven D. , Madrenas Joaquin , Anasetti Claudio 
Published: April 2014

AbstractTCR engagement can induce either T cell proliferation and differentiation or activation-induced T cell death (AICD) through apoptosis. The intracellular signaling pathways that dictate such a disparate fate after TCR engagement have only been partially elucidated. Non-FcR-binding anti-CD3 mAbs induce a partial agonist TCR signaling pattern and cause AICD on Ag-activated, cycling T cells. In this study, we examined TCR signaling during the induction of AICD by anti-CD3 fos, a non-FcR-binding anti-CD3 mAb. This mAb activates Fyn, Lck, and extracellular signal-regulated kinase, and induces phosphorylation of Src-like adapter protein, despite the inability to cause calcium mobilization or TCR polarization. Anti-CD3 fos also fails to effectively activate ζ-associated protein of 70 kDa or NF-κB. Using Ag-specific T cells deficient for Fyn or Lck, we provide compelling evidence that activation of Lck is required for the induction of AICD. Our data indicate that a selective and distinct TCR signaling pattern is required for AICD by TCR partial agonist ligands.
Importance of IL-10 for CTLA-4-Mediated Inhibition of Tumor-Eradicating Immunity
Authors: Jovasevic Vladimir M. , Gorelik Leonid , Bluestone Jeffrey A. , Mokyr Margalit B. 
Published: April 2014

AbstractIn this study, we show that engagement of CTLA-4 on tumor-infiltrating lymphocytes from low-dose melphalan (l-phenylalanine mustard (l-PAM))-treated MOPC-315 tumor bearers led to IL-10 secretion. In addition, the inhibitory activity of CTLA-4 ligation for IFN-γ secretion following stimulation with anti-CD3 plus anti-CD28 mAb depended on IL-10 production. Consistent with the importance of IL-10 for CTLA-4-mediated inhibition, administration of neutralizing anti-IL-10 mAb to low-dose l-PAM-treated MOPC-315 tumor bearers (administration of blocking anti-CTLA-4 mAb) resulted in enhanced tumor-infiltrating lymphocyte-mediated anti-MOPC-315 cytotoxicity and led to complete tumor eradication in a higher percentage of mice than that observed with low-dose l-PAM alone. The percentage of MOPC-315 tumor-bearing mice cured following administration of neutralizing anti-IL-10 mAb to low-dose l-PAM-treated MOPC-315 tumor bearers was comparable to that observed following administration of blocking anti-CTLA-4 mAb. Moreover, IL-10 neutralization together with CTLA-4 blockade did not provide added therapeutic benefits to low-dose l-PAM-treated MOPC-315 tumor bearers. Taken together, these results indicate that CTLA-4 blockade improves the therapeutic outcome of low-dose l-PAM for MOPC-315 tumor bearers by inhibiting IL-10 secretion as a consequence of blocking CTLA-4 ligation.