bluuebunny/crossref_metadata_2025_split huggingface dataset:
Non-Fc Receptor-Binding Humanized Anti-CD3 Antibodies Induce Apoptosis of Activated Human T Cells
Authors: Carpenter Paul A. , Pavlovic Sandra , Tso J. Y. , Press Oliver W. , Gooley Theodore , Yu Xue-Zhong , Anasetti Claudio 
Published: April 2014

AbstractHuman trials in organ allografts have demonstrated that murine anti-CD3 mAbs are immunosuppressive. By mimicking Ag, anti-CD3 can produce T cell activation, anergy, or death. Activation of resting T cells in vivo results in dose-limiting cytokine release and is caused by Ab-mediated cross-linking of T cells and Fcγ receptor (FcR)-bearing cells. With the goal of minimizing cytokine-induced toxicity, anti-CD3 have been engineered to lower Fc binding avidity. Preclinical murine studies have indicated that non-FcR-binding anti-CD3 can induce apoptosis of Ag-activated T cells. Since induction of T cell apoptosis may be an important mechanism of immunosuppression by anti-CD3, we tested whether Fc mutations affect the ability of anti-human CD3 to induce apoptosis of activated T cells. We compared wild-type murine anti-CD3, M291, and OKT3 and their humanized, FcR- and non-FcR-binding structural variants in quantitative assays of T cell apoptosis. Non-FcR-binding variants produced more sustainable phosphorylation of extracellular signal-regulated kinase-2, greater release of IFN-γ, and more effectively caused activation-dependent T cell apoptosis. Non-FcR-binding variants dissociated more quickly from the T cell surface and caused less internalization of the TCR, which then remained available in greater abundance on the cell surface for signaling. Cross-linking of non-FcR-binding variants by antiglobulin enhanced TCR internalization and minimized induction of T cell apoptosis. We conclude that non-FcR-binding, humanized anti-CD3 have improved ability to induce apoptosis of activated T cells, presumably by allowing durable expression of the TCR and sustained signaling.
Examination of CD8+ T Cell Function in Humans Using MHC Class I Tetramers: Similar Cytotoxicity but Variable Proliferation and Cytokine Production Among Different Clonal CD8+ T Cells Specific to a Single Viral Epitope
Authors: Lim Dong-Gyun , Bieganowska Bourcier Katarzyna , Freeman Gordon J. , Hafler David A. 
Published: April 2014

AbstractFollowing infection by human T cell lymphotrophic virus-I (HTLV-I), high frequencies of polyclonal Tax11–19-reactive CD8+ T cells can be detected in the peripheral blood. To investigate whether there are differences in the effector functions of these cells, we generated a panel of Tax11–19-reactive T cell clones by single cell sorting of HLA-A2/Tax11–19 tetramer binding CD8+ T cells followed by repeated stimulation with PHA and IL-2. Examination of the TCRs revealed 17 different T cell clones with unique clonal origins. Nine representative CD8+ T cell clones showed a similar cytotoxic dose-response activity against Ag-pulsed target cells, even though they express different TCRs. This cytotoxic effector function was not influenced by the engagement of either CD28 or CD2 costimulatory molecules. In contrast to the cytotoxic activity, qualitatively different degrees of proliferative response and cytokine secretion were observed among T cell clones of different clonal origin. The induction of proliferation and cytokine secretion required the engagement of costimulatory molecules, particularly CD2-LFA-3 interaction. These results indicate that functionally diverse, polyclonal CTL populations can be activated specific to a single immunodominant viral epitope; they can manifest virtually identical cytotoxic effector function but have marked differences in proliferation and cytokine secretion.
IL-12 Receptor β2 (IL-12Rβ2)-Deficient Mice Are Defective in IL-12-Mediated Signaling Despite the Presence of High Affinity IL-12 Binding Sites
Authors: Wu Chang-you , Wang Xin , Gadina Massimo , O’Shea John J. , Presky David H. , Magram Jeanne 
Published: April 2014

AbstractTwo subunits of the IL-12 receptor (IL-12R), IL-12Rβ1 and IL-12Rβ2, have been identified and cloned. Previous studies demonstrated that the IL-12Rβ1 subunit was required for mouse T and NK cells to respond to IL-12 in vivo. To investigate the role of IL-12Rβ2 in IL-12 signaling, we have generated IL-12Rβ2-deficient (IL-12Rβ2−/−) mice by targeted mutation in embryonic stem (ES) cells. Although Con A-activated splenocytes from IL-12Rβ2−/− mice still bind IL-12 with both high and low affinity, no IL-12-induced biological functions can be detected. Con A-activated splenocytes of IL-12Rβ2−/− mice failed to produce IFN-γ or proliferate in response to IL-12 stimulation. NK lytic activity of IL-12Rβ2−/− splenocytes was not induced when incubated with IL-12. IL-12Rβ2−/− splenocytes were deficient in IFN-γ secretion when stimulated with either Con A or anti-CD3 mAb in vitro. Furthermore, IL-12Rβ2−/− mice were deficient in vivo in their ability to produce IFN-γ following endotoxin administration and to generate a type 1 cytokine response. IL-12-mediated signal transduction was also defective as measured by phosphorylation of STAT4. These results demonstrate that although mouse IL-12Rβ1 is the subunit primarily responsible for binding IL-12, IL-12Rβ2 plays an essential role in mediating the biological functions of IL-12 in mice.
Peptide-MHC Class I Tetrameric Complexes Display Exquisite Ligand Specificity
Authors: Burrows Scott R. , Kienzle Norbert , Winterhalter Adam , Bharadwaj Mandvi , Altman John D. , Brooks Andrew 
Published: April 2014

AbstractThe production of synthetic MHC-peptide tetramers has revolutionized cellular immunology by revealing enormous CD8+ T cell expansions specific for peptides from various pathogens. A feature of these reagents, essential for their staining function, is that they bind T cells with relatively high avidity. This could, theoretically, promote cross-reactivity with irrelevant T cells leading to overestimates of epitope-specific T cell numbers. Therefore, we have investigated the fine specificity of CTL staining with these reagents for comparison with functional data. Using a panel of CTL clones with distinct fine specificity patterns for analogs of an HLA-B8-binding EBV epitope, together with B8 tetramers incorporating these peptides, we show a very good correlation between tetramer staining and peptide activity in cytotoxicity assays. Significant staining only occurred with tetramers that incorporate strong stimulatory agonist peptides and not weak agonists that are unlikely to induce full T cell activation at physiological levels of presentation. In almost every case where a peptide analog had &gt;10-fold less activity than the optimal EBV peptide in cytotoxicity assays, the corresponding tetramer stained with &gt;10-fold less intensity than the EBV epitope tetramer. Furthermore, by examining an EBV-specific clonotypic T cell expansion in EBV-exposed individuals, we show similar fine specificity in tetramer staining of fresh peripheral T cells. Collectively, our data demonstrate the exquisite specificity of class I MHC-peptide tetramers, underlining their accuracy in quantifying only those T cells capable of recognizing the low levels of cell surface peptide presented after endogenous Ag processing.
Cytokine-Stimulated T Lymphocyte Proliferation Is Regulated by p27Kip1 1
Authors: Zhang Shangming , Lawless Victoria A. , Kaplan Mark H. 
Published: April 2014

AbstractT lymphocyte growth is regulated by the cyclin-dependent kinase inhibitor p27Kip1. Mice deficient in p27Kip1 have increased proliferative responses to multiple cytokines, including IL-2, IL-4, and IL-12, but not to anti-CD3. In the absence of p27Kip1, T cells proliferate faster than control cells, as evidenced by increased [3H]thymidine uptake, increased cell growth and division, and an increased number of cells in S phase. Importantly, this regulation is specific for p27Kip1 in T cells, because hyperproliferation of T cells from mice deficient in p21Cip1/Waf1 was not observed. In vivo, there is an expansion of activated/memory CD4+ cells in p27Kip1-deficient mice before and after immunization. Furthermore, Ag-stimulated spleen cells from immunized p27Kip1-deficient mice demonstrated increased proliferative responses to IL-2 and increased secretion of IFN-γ. Although IL-4 stimulated proliferative responses are diminished in Stat6-deficient T cells, activated T cells from mice doubly deficient in both p27Kip1 and Stat6 recover normal proliferative responses to IL-4. Together, these data firmly support a role for p27Kip1 as a negative regulator of cytokine-stimulated T cell growth.
Enhanced Dendritic Cell Maturation by TNF-α or Cytidine-Phosphate-Guanosine DNA Drives T Cell Activation In Vitro and Therapeutic Anti-Tumor Immune Responses In Vivo
Authors: Brunner Christoph , Seiderer Julia , Schlamp Angelika , Bidlingmaier Martin , Eigler Andreas , Haimerl Wolfgang , Lehr Hans-Anton , Krieg Arthur M. , Hartmann Gunther , Endres Stefan 
Published: April 2014

AbstractDendritic cells (DC) manipulated ex vivo can induce tumor immunity in experimental murine tumor models. To improve DC-based tumor vaccination, we studied whether DC maturation affects the T cell-activating potential in vitro and the induction of tumor immunity in vivo. Maturation of murine bone marrow-derived DC was induced by GM-CSF plus IL-4 alone or by further addition of TNF-α or a cytidine-phosphate-guanosine (CpG)-containing oligonucleotide (ODN-1826), which mimics the immunostimulatory effect of bacterial DNA. Flow cytometric analysis of costimulatory molecules and MHC class II showed that DC maturation was stimulated most by ODN-1826, whereas TNF-α had an intermediate effect. The extent of maturation correlated with the secretion of IL-12 and the induction of alloreactive T cell proliferation. In BALB/c mice, s.c. injection of colon carcinoma cells resulted in rapidly growing tumors. In this model, CpG-ODN-stimulated DC cocultured with irradiated tumor cells also induced prophylactic protection most effectively and were therapeutically effective when administered 3 days after tumor challenge. Thus, CpG-ODN-enhanced DC maturation may represent an efficient means to improve clinical tumor vaccination.
Clonality and Longevity of CD4+CD28null T Cells Are Associated with Defects in Apoptotic Pathways
Authors: Vallejo Abbe N. , Schirmer Michael , Weyand Cornelia M. , Goronzy Jörg J. 
Published: April 2014

AbstractCD4+CD28null T cells are oligoclonal lymphocytes rarely found in healthy individuals younger than 40 yr, but are found in high frequencies in elderly individuals and in patients with chronic inflammatory diseases. Contrary to paradigm, they are functionally active and persist over many years. Such clonogenic potential and longevity suggest altered responses to apoptosis-inducing signals. In this study, we show that CD4+CD28null T cells are protected from undergoing activation-induced cell death. Whereas CD28+ T cells underwent Fas-mediated apoptosis upon cross-linking of CD3, CD28null T cells were highly resistant. CD28null T cells were found to progress through the cell cycle, and cells at all stages of the cell cycle were resistant to apoptosis, unlike their CD28+ counterparts. Neither the activation-induced up-regulation of the IL-2R α-chain (CD25) nor the addition of exogenous IL-2 renders them susceptible to Fas-mediated apoptosis. These properties of CD28null T cells were related to high levels of Fas-associated death domain-like IL-1-converting enzyme-like inhibitory protein, an inhibitor of Fas signaling that is normally degraded in T cells following activation in the presence of IL-2. Consistent with previous data showing protection of CD28null cells from spontaneous cell death, the present studies unequivocally show dysregulation of apoptotic pathways in CD4+CD28null T cells that favor their clonal outgrowth and maintenance in vivo.
Regulation of Toll-Like Receptor 2 Expression by Macrophages FollowingMycobacterium aviumInfection
Authors: Wang Tianyi , Lafuse William P. , Zwilling Bruce S. 
Published: April 2014

AbstractRecent studies have implicated Toll-like receptors (TLR), especially TLR2 and TLR4, as sentinel receptors that signal the interaction of macrophages with bacterial pathogens via a NF-κB-mediated pathway. The regulation of TLR gene expression, however, has not been intensively studied. Here, we report that TLR2 mRNA was induced following infection of murine macrophages with Mycobacterium avium. The changes in TLR2 mRNA correlated with an increase in TLR2 surface expression. Infection with M. avium resulted in a concomitant decrease in TLR4 mRNA. The effect of M. avium infection on TLR2 mRNA appeared to be mediated, in part, by TLR2 because the induction of the mRNA was partially blocked by preincubation of the macrophages with an anti-human TLR2 Ab. In contrast, the effect of LPS stimulation was mediated via TLR4 because infection of macrophages from LPSd mice, which do not express active TLR4, resulted in an increase in TLR2 mRNA, while treatment of macrophages from these mice with LPS failed to induce TLR2 mRNA. Several cytokines, including TNF-α, IL-1α, and GM-CSF, but not IFN-γ, induced TLR2 mRNA. M. avium infection resulted in the induction of TLR2 mRNA by macrophages from both TNFRI knockout and NF-κB p50 knockout mice.
Relative Diabetogenic Properties of Islet-Specific Tc1 and Tc2 Cells in Immunocompetent Hosts
Authors: Vizler Csaba , Bercovici Nadège , Heurtier Agnès , Pardigon Nathalie , Goude Karine , Bailly Karine , Combadière Christophe , Liblau Roland S. 
Published: April 2014

AbstractCD8+ T cells are important effectors, as well as regulators, of organ-specific autoimmunity. Compared with Tc1-type CD8+ cells, Tc2 cells have impaired anti-viral and anti-tumor effector functions, although no data are yet available on their pathogenic role in autoimmunity. Our aim was to explore the role of autoreactive Tc1 and Tc2 cells in autoimmune diabetes. We set up an adoptive transfer model in which the recipients were transgenic mice expressing influenza virus hemagglutinin (HA) specifically in their pancreatic β islet cells (rat insulin promoter-HA mice) and islet-specific Tc1 and Tc2 cells were generated in vitro from HA-specific CD8+ cells of TCR transgenic mice (CL4-TCR mice). One million Tc1 cells, differentiated in vitro in the presence of IL-12, transferred diabetes in 100% of nonirradiated adult rat insulin promoter-HA recipients; the 50% diabetogenic dose was 5 × 105. Highly polarized Tc2 cells generated in the presence of IL-4, IL-10, and anti-IFN-γ mAb had a relatively low, but definite, diabetogenic potential. Thus, 5 × 106 Tc2 cells caused diabetes in 6 of 18 recipients, while the same dose of naive CD8+ cells did not cause diabetes. Looking for the cause of the different diabetogenic potential of Tc1 and Tc2 cells, we found that Tc2 cells are at least as cytotoxic as Tc1 cells but their accumulation in the pancreas is slower, a possible consequence of differential chemokine receptor expression. The diabetogenicity of autoreactive Tc2 cells, most likely caused by their cytotoxic activity, precludes their therapeutic use as regulators of autoimmunity.
Differential Sensitivity to Mutations in a Single Peptide by Two TCRs Having Identical β-Chains and Closely Related α-Chains
Authors: Dittel Bonnie N. , Janeway Charles A. 
Published: April 2014

AbstractThe TCR on CD4 T cells binds to and recognizes MHC class II:antigenic peptide complexes through molecular contacts with the peptide amino acid residues that face up and out of the peptide-binding groove. This interaction primarily involves the complementarity-determining regions (CDR) of the TCR α- and β-chains contacting up to five residues of the peptide. We have used two TCRs that recognize the same antigenic peptide and have identical Vβ8.2 chains, but differ in all three CDR of their related Vα2 chains, to examine the fine specificity of the TCR:peptide contacts that lead to activation. By generating a peptide library containing all 20 aa residues in the five potential TCR contact sites, we were able to demonstrate that the two similar TCRs responded differentially when agonist, nonagonist, and antagonist peptide functions were examined. Dual substituted peptides containing an agonist residue at the N terminus, which interacts with CDR2α, and an antagonist residue at the C terminus, which interacts with the CDR3β, were used to show that the nature of the overall signal through the TCR is determined by a combination of the type of signal received through both the TCR α- and β-chains.
Mapping of the Region of Complement Receptor (CR) 1 Required forPlasmodium falciparumRosetting and Demonstration of the Importance of CR1 in Rosetting in Field Isolates
Authors: Rowe J. Alexandra , Rogerson Stephen J. , Raza Ahmed , Moulds Joann M. , Kazatchkine Michel D. , Marsh Kevin , Newbold Chris I. , Atkinson John P. , Miller Louis H. 
Published: April 2014

AbstractThe malaria parasite Plasmodium falciparum induces a number of novel adhesion properties in the erythrocytes that it infects. One of these properties, the ability of infected erythrocytes to bind uninfected erythrocytes to form rosettes, is associated with severe malaria and may play a direct role in the pathogenesis of disease. Previous work has shown that erythrocytes deficient in complement receptor (CR) 1 (CR1, CD35; C3b/C4b receptor) have greatly reduced rosetting capacity, indicating an essential role for CR1 in rosette formation. Using deletion mutants and mAbs, we have localized the region of CR1 required for the formation of P. falciparum rosettes to the area of long homologous repeat regions B and C that also acts as the binding site for the activated complement component C3b. This result raises the possibility that C3b could be an intermediary in rosetting, bridging between the infected erythrocyte and CR1. We were able to exclude this hypothesis, however, as parasites grown in C3-deficient human serum formed rosettes normally. We have also shown in this report that rosettes can be reversed by mAb J3B11 that recognizes the C3b binding site of CR1. This rosette-reversing activity was demonstrated in a range of laboratory-adapted parasite strains and field isolates from Kenya and Malawi. Thus, we have mapped the region of CR1 required for rosetting and demonstrated that the CR1-dependent rosetting mechanism occurs commonly in P. falciparum isolates, and could therefore be a potential target for future therapeutic interventions to treat severe malaria.
Desensitization of CXC Chemokine Receptor 4, Mediated by IL-16/CD4, Is Independent of p56lckEnzymatic Activity
Authors: Van Drenth Charlotte , Jenkins Ayana , Ledwich Lindsey , Ryan Thomas C. , Mashikian Margaret Vallen , Brazer William , Center David M. , Cruikshank William W. 
Published: April 2014

AbstractCCR5 and CXC chemokine receptor 4 (CXCR4) are coreceptors for CD4 as defined by HIV-1 glycoprotein (gp) 120 binding. Pretreatment of T cells with gp120 results in modulation of both CCR5 and CXCR4 responsiveness, which is dependent upon p56lck enzymatic activity. The recent findings that pretreatment of T cells with a natural CD4 ligand, IL-16, could alter cellular responsiveness to macrophage-inflammatory protein-1β (MIP-1β) stimulation, prompted us to investigate whether IL-16 could also alter CXCR4 signaling. These studies demonstrate that IL-16/CD4 signaling in T lymphocytes also results in loss of stromal derived factor-1α (SDF-1α)/CXCR4-induced chemotaxis; however, unlike MIP-1β/CCR5, the effects were not reciprocal. There was no effect on eotaxin/CCR3-induced chemotaxis. Desensitization of CXCR4 by IL-16 required at least 10–15 min pretreatment; no modulation of CXCR4 expression was observed, nor was SDF-1α binding altered. Using murine T cell hybridomas transfected to express native or mutated forms of CD4, it was determined that IL-16/CD4 induces a p56lck-dependent inhibitory signal for CXCR4, which is independent of its tyrosine catalytic activity. By contrast, IL-16/CD4 desensitization of MIP-1β/CCR5 responses requires p56lck enzymatic activity. IL-16/CD4 inhibition of SDF-1α/CXCR4 signals requires the presence of the Src homology 3 domain of p56lck and most likely involves activation of phosphatidylinositol-3 kinase. These studies indicate the mechanism of CXCR4 receptor desensitization induced by a natural ligand for CD4, IL-16, is distinct from the inhibitory effects induced by either gp120 or IL-16 on CCR5.
Involvement of the Ubiquitin-Proteasome Pathway in the Degradation of Nontyrosine Kinase-Type Cytokine Receptors of IL-9, IL-2, and Erythropoietin
Authors: Yen Chao-Huang , Yang Yu-Chung , Ruscetti Sandra K. , Kirken Robert A. , Dai Ren Ming , Li Chou-Chi H. 
Published: April 2014

Abstract
The ubiquitin-dependent proteasome-mediated (Ub-Pr) degradation pathway has been shown to regulate a large variety of substrates, including nuclear, cytosolic, and membrane proteins. In mammalian systems, polyubiquitin modification has been identified in a number of cell surface receptors for more than a decade; however, its biological significance has remained unclear until recently. For growth factor receptors with intrinsic tyrosine kinase domains, polyubiquitination is believed to trigger the internalization and subsequent degradation via the lysosomal pathway. In this study we provide the first evidence that non-tyrosine kinase-type cytokine surface receptors, IL-9R α-chain, IL-2 receptor β-chain, and erythropoietin receptor, can be polyubiquitinated and degraded by proteasomes. The Ub-Pr pathway regulates both the basal level turnover and the ligand-induced degradation of the receptors. A previously identified putative molecular chaperon, valosin-containing protein, undergoes tyrosine phosphorylation in a cytokine-dependent manner and associates with the receptor complexes following receptor engagement, suggesting that valosin-containing protein may target the ubiquitinated receptors to the proteasome for degradation.
Vβ T Cell Repertoire of CD8+ Splenocytes Selected on Nonpolymorphic MHC Class I Molecules
Authors: Laouini Dhafer , Casrouge Armanda , Dalle Sophie , Lemonnier François , Kourilsky Philippe , Kanellopoulos Jean 
Published: April 2014

Abstract
In this work, we have studied the role of the MHC class Ib molecules in the selection and maintenance of CD8+ T splenocytes. We have compared the CD8+ T cell repertoires of wild-type, H-2K-deficient, H-2D-deficient, or double knockout C57BL/6 mice. We show that the different CD8+ repertoires, selected either by class Ia and class Ib or by class Ib molecules only, use the various Vα (AV) and Vβ (BV) rearrangements in the same proportion and without biases in the CDR3 size distribution. Furthermore, we have estimated the size of the BV repertoire in the four different strains of mice. Interestingly, we have found that the BV repertoire size is proportional to the overall number of CD8+ splenocytes. This observation implies that BV diversity is positively correlated with the number of CD8+ cells, even when the number of CD8+ splenocytes is dramatically reduced (90% in the double knockout mice).