bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induction, regulation, and function of soluble TRAP (CD40 ligand) during interaction of primary CD4+ CD45RA+ T cells with dendritic cells
Authors: Ludewig Burkhard , Henn Volker , Schröder Jens M. , Graf Daniel , Kroczek Richard A. 
Published: March 2007

AbstractTo assess the induction, regulation, and the relative roles of cell surface tumor necrosis factor‐related activation protein (TRAP; CD40 ligand) and the soluble form of TRAP (sTRAP) in the initial phase of T cell activation, primary CD4+ CD45RA+ (naive) T cells were co‐cultured with mature Langerhans' cells (mLC) in the presence of superantigen. In this cell system, TRAP was very efficiently induced in T cells at both the mRNA and protein levels. After appearing on the cell surface, TRAP was rapidly down‐regulated by a mechanism triggered through interaction of TRAP with CD40 on mLC. Co‐culture of T cells with mLC led to the release of sTRAP, an 18‐kDa protein capable of binding to CD40. Experimental data strongly suggest that sTRAP is not released by proteolytic cleavage of TRAP on the cell surface, but is generated in an intracellular compartment. Release of sTRAP and induction of TRAP cell surface expression were found to be regulated independently. In terms of function, sTRAP cannot compete with cell surface TRAP for ligation of CD40 on mLC, indicating that sTRAP release is not a mechanism for termination of the TRAP/CD40 interaction. However, sTRAP on its own rapidly down‐regulates CD40 expression on mLC and has long‐lasting anti‐apoptotic effects on dendritic cells. Thus, we infer from our results obtained in vitro that primary activation of CD4+ T cells by dendritic cells in the lymphoid tissues leads to release of sTRAP, which may act on CD40+ bystander cells in a cytokine‐like fashion.
Cell division in the compartment of naive and memory T lymphocytes
Authors: Bruno Ludovica , von Boehmer Harald , Kirberg Jörg 
Published: March 2007

AbstractExpression of activation markers and proliferative status were measured in peripheral CD4+ and CD8+ T cells of various T cell receptor (TCR)‐transgenic mice either before or after intentional antigenic stimulation. In the absence of intentional immunization, CD4+ T cells persisted as resting or partially activated and cycling cells depending on the specificity of their TCR. Similar results were obtained following transfer into T cell‐deficient recipients, i.e. T cells that were not cycling in situ did not cycle after transfer, whereas cells that were proliferating in situ also cycled after transfer. Thus, the TCR of some cells in the absence of intentional antigenic stimulation may bind to some unidentified ligand that does not induce tolerance, but rather slow expansion. In a different sort of experiment, activated T cells that were derived from noncycling naive T cells by deliberate antigenic stimulation continued to cycle slowly even a long time after transfer into antigen‐free recipients that did not induce proliferation of the naive cells. Thus, lymphokines or ligands that do not induce activation of naive T cells may be responsible for the maintenance of memory cells. Our experiments show that the latter does not depend on a second TCR expressed by the memory cells, since memory T cells from RAG‐2−/−TCR‐transgenic mice persisted to a similar extent.
Differential expression of CLIP: MHC class II and conventional endogenous peptide: MHC class II complexes by thymic epithelial cells and peripheral antigen‐presenting cells
Authors: Farr Andrew , Deroos Paul C. , Eastman Susan , Rudensky Alexander Y. 
Published: March 2007

AbstractMajor histocompatibility complex (MHC) class II molecules expressed by thymic epithelial cells are involved in positive selection of CD4 T cells, whereas the high‐avidity interaction of T cell receptors with the endogenous peptide : MHC class II complexes expressed on bone marrow (BM)‐derived antigen‐presenting cells (APC) and, to a lesser extent, on thymic epithelial cells mediate negative selection. To understand better the generation of the CD4 T cell repertoire both in the thymus and in the periphery we analyzed relative levels of expression of specific endogenous peptide: MHC class II complexes in thymic epithelial cells (TEC) and peripheral APC. Expression of Eα52–68: I‐Ab and class II‐associated invariant chain peptide (CLIP): I‐Ab complexes in thymic epithelial cells and in the bone‐marrow derived splenic APC, i.e. B cells, was studied using YAe and 30‐2 monoclonal antibodies which are specific for the corresponding complexes. To distinguish between expression of both complexes in radioresistant thymic epithelial elements and radiation sensitive BM‐derived APC, radiation BM chimeras were constructed. Using immunohistochemical and immunochemical approaches we demonstrated that the level of expression of Eα52–68:I‐Ab complexes in thymic epithelial cells is approximately 5–10 % of that seen in splenic cells whereas total class II levels were comparable. In contrast, CLIP: I‐Ab complexes are expressed at substantially higher levels in TEC vs. splenic APC. This result demonstrates quantitative differences in expression of distinct peptide: MHC class II complexes in thymic epithelial cells and peripheral splenic APC.
The role of tyrosine phosphorylation and PTP‐1C in CTLA‐4 signal transduction
Authors: Chambers Cynthia A. , Allison James P. 
Published: March 2007

AbstractRecently, there has been increasing interest in the inhibitory regulators of lymphocyte activation, and in particular, the role of CD28 homologue CTLA‐4 in the regulation of T cell responses. Interaction of CTLA‐4 with B7 ligands inhibits T cell responses, including T cell proliferation and interleukin‐2 (IL‐2) secretion. The mechanism(s) responsible for CTLA‐4 signal transduction are unknown, but it has been suggested that tyrosine phosphorylation is involved. Here we demonstrate that phorbol ester phorbol 12‐myrislate 13‐acetate (PMA), which increases tyrosine phosphorylation by stimulating protein kinase C and p21ras, can overcome the CTLA‐4‐mediated inhibition of T cell proliferation. This provides the first functional evidence that tyrosine phosphorylation is involved in CTLA‐4 signal transduction. Most interestingly, CTLA‐4‐mediated inhibition of IL‐2 secretion was not influenced by the presence of PMA. Further, we demonstrate that CTLA‐4 cross‐linking inhibits proliferation and IL‐2 secretion of T cells from motheaten mice. These mice lack PTP‐1C, a tyrosine phosphatase which mediates in a number of lymphocyte inhibitory responses, indicating that PTP‐1C is not essential for CTLA‐4 signaling. Collectively, these results demonstrate that regulation of tyrosine phosphorylation plays a pivotal role in CTLA‐4 function, and that the inhibition of the transition from G0/G1 to the S phase of the cell cycle and the inhibition of IL‐2 secretion require distinct signaling pathways. These experiments provide a useful model system which can be used to elucidate the signaling pathways involved in CTLA‐4 function and to understand how CTLA‐4, CD28 and T cell receptor‐mediated signals are integrated in T cell responses to antigen.
Human leukocyte antigen phenotype imposes complex constraints on the antigen‐specific cytotoxic T lymphocyte repertoire
Authors: Burrows Scott R. , Silins Sharon L. , Cross Simone M. , Au Peh Chen , Rischmueller Maureen , Burrows Jacqueline M. , Elliott Suzanne L. , McCluskey James 
Published: March 2007

AbstractThe memory response to the immunodominant Epstein‐Barr virus (EBV) epitope FLRGRAYGL, which associates with HLA B8, is exceptionally restricted, being dominated by cytotoxic T lymphocytes (CTL) with a single, public T cell receptor (TCR). CTL clones that express this receptor fortuitously cross‐react with the alloantigen HLA B44. However, of the two major subtypes of this HLA, B*4402 and B*4403, that differ by a single amino acid, only the former is recognized by these mature CTL clones. Individuals heterozygous for HLA B8 and B*4402 use alternative TCR for the EBV determinant since the dominant TCR is potentially self‐reactive. We now demonstrate that this clonotype is also essentially absent from the repertoire of CTL directed against the viral epitope in seven from seven unrelated individuals heterozygous for HLA B8 and B*4403. Thus immune tolerance of these CTL recognizing HLA B*4402 is associated with expression of either B*4402 or B*4403. This suggests that tolerance in the human T cell compartment requires a lower threshold of recognition than for effector function, thus providing a buffer zone minimizing the risk of autoimmunity. These data also illustrate the potential for non‐restricting HLA molecules to bias dramatically the T cell repertoire used for specific immune responses. Such influences may be the basis of the “protective” effects of certain HLA alleles in susceptibility to autoimmune disorders.
A novel peripheral CD4+CD8+ T cell population: Inheritance of CD8α expression on CD4+ T cells
Authors: Luhtala Marko , Lassila Olli , Toivanen Paavo , Vainio Olli 
Published: March 2007

AbstractIn this study we show the inheritance of a CD4+CD8+ peripheral T cell population in the H.B15 chicken strain. A large proportion of αβ T cells in peripheral blood (20–40%), spleen (10–20%) and intestinal epithelium (5–10%) co‐express CD4 and CD8α, but not CD8β. CD4+ CD8αα cells are functionally normal T cells, since they proliferate in response to mitogens and signals delivered via the αβT cell receptor as well as via the CD28 co‐receptor. These cells induce in vivo a graft versus host‐reaction, providing further evidence for their function as CD4+ T cells. The CD4+CD8αα T cell population was found in 75% of the first progeny and in 100% of further progenies, demonstrating that co‐expression of CD4 and CD8 on peripheral T cells is an inherited phenomenon. In addition, cross‐breeding data suggest a dominant Mendelian form of inheritance. The hereditary expression of CD8α on peripheral CD4+ T cells in chicken provides a unique model in which to study the regulation of CD4 and CD8 expression.
Cytotoxic T lymphocytes express a β3 integrin which can induce the phosphorylation of focal adhesion kinase and the related PYK‐2
Authors: Ma Eileen A. , Lou Olivia , Berg Nancy N. , Ostergaard Hanne L. 
Published: March 2007

AbstractFibronectin has been shown to stimulate tyrosine phosphorylation of a number of proteins in the 115–125 kDa range and facilitate degranulation by alloantigen‐specific cytotoxic T lymphocyte (CTL) clones in response to substimulatory amounts of anti‐CD3 or anti‐T cell receptor (TCR). The current study was initiated to further characterize integrin expression and usage by these CTL clones. We demonstrate that vitronectin and fibrinogen, but not laminin or collagen, are also able to both facilitate degranulation in the presence of substimulatory anti‐CD3 and stimulate tyrosine phosphorylation of these 115–125‐kDa proteins, with a 115‐kDa protein being the most prominently phosphorylated. These results implicate the expression and usage of the vitronectin receptor, α β3 integrin, by these CTL clones. We demonstrate by both flow cytometry and immunoprecipitation that CTL clones do in fact express β3 integrin. Immobilized antibody to β3 stimulates the phosphorylation of the 115–125‐kDa proteins, suggesting that engagement of β3 transmits the same signal into these cells as fibronectin or vitronectin. The fibronectin and vitronectin‐induced phosphorylation as well as adhesion to either fibronectin or vitronectin can be significantly inhibited with antibodies to β3 integrins. Finally, we are able to immunoprecipitate 115‐kDa proteins with antiserum to focal adhesion kinase and a related kinase, called PYK‐2, that becomes phosphorylated in response to vitronectin or immobilized anti‐β3. Taken together, these results demonstrate that CTL express and use β3‐integrins as signaling molecules which can augment TCR‐mediated stimulation.
Absolute dependence of T cell receptorhi cell generation and relative dependence of T cell receptorint cell generation on the thymus
Authors: Tsukahara Akihiro , Moroda Tetsuya , Iiai Tsuneo , Suzuki Susumu , Tada Takashi , Hatakeyama Katsuyoshi , Abo Toru 
Published: March 2007

AbstractRecent evidence indicates that conventional T cells are generated by the mainstream of T cell differentiation in the thymus and acquire a high density of T cell receptor expression (i.e. TCRhi). In contrast, primordial T cells (or NK1.1+ T cells) are generated by the extrathymic pathways or an alternative intrathymic pathway and express an intermediate density of TCR (i.e. TCRint). To obtain further evidence, it was examined how thymus grafting influenced the distribution of T cell populations in athymic nude mice. When BALB/c nu/nu mice were engrafted with thymocyte‐depleted BALB/c+/+ fetal thymi, two changes emerged after grafting: nude mice generated TCRhi cells de novo in the periphery as well as in the grafted thymi, and the absolute number of interleukin‐2 receptor β chain+ TCRint cells increased prominently in number in the periphery. Among thymic hormones tested, the administration of thymosin α induced a slight expansion of CD3int cells in nude mice. To examine a possible interaction of TCRint cells with TCRhi cells in the periphery, B6 nu/nu mice (Ly5.2+) were injected with TCRhi cells purified from the spleen of B6 Ly5.1 congenic mice. In this case, TCRint (Ly5.2+) cells expanded well in all tested organs of nude mice. These results suggest that the generation of TCRhi cells is absolutely dependent on the thymus and that TCRint cells expand under the influence of the thymus (humoral) and due to interaction with thymus‐derived conventional T cells.
NFE, a new transcriptional activator that facilitates p50 and c‐Rel‐dependent IgH 3′ enhancer activity
Authors: Linderson Ylva , Cross Daniel , Neurath Markus F. , Pettersson Sven 
Published: March 2007

AbstractThe induction of immunoglobulin heavy chain (IgH) 3′ enhancer activity has been coupled to ligand/receptor‐dependent activation of resting B cells. To search for transcriptional target sites that account for this induction, extracts from lipopolysaccharide (LPS)‐stimulated B cells and cell lines were used. Here we describe, by gel‐retardation analysis, the identification of an NF‐χB site and an adjacent nuclear factor ets‐like (NFE) site in the 3′ enhancer. The NFE motif binds four protein complexes in resting B cell extracts, of which two are down‐regulated upon LPS stimulation. Gel shift‐shift experiments of the NF‐χB complexes with specific antibodies identified p50 and c‐Rel proteins to be the predominant factors in primary LPS‐stimulated cell extracts. Site‐directed mutagenesis of these motifs demonstrates that they contribute to part of the enhancer activity in plasma cells. One copy of the NFχB/NFE motifs, linked to a hetero‐logous reporter construct, displays lymphoid‐restricted reporter gene activity in transient transfection assays. Mutation of either site abrogates all promoter activity. Complementation experiments demonstrate that although p50 and c‐Rel expression vectors reconstitute transcription of an intact NF‐χB/NFE reporter construct in a dose‐dependent manner, mutation of the NFE site or the NF‐χB site abrogates essentially all transcriptional activity in both plasma cells and in COS cells. Taken together, we provide evidence for the existence of an activator, NFE, which in combination with the p50 and c‐Rel proteins, are part of the transcription factor machinery that regulates 3′ enhancer activity, and thus the control of the IgH locus in late B lymphocyte development.
Structural identification of the hematopoietic progenitor antigen ER‐MP12 as the vascular endothelial adhesion molecule PECAM‐1 (CD31)
Authors: Ling Vincent , Luxenberg Deborah , Wang Jack , Nickbarg Elliot , Leenen Pieter J. M. , Neben Steven , Kobayashi Michiko 
Published: March 2007

AbstractThe monoclonal antibody ER‐MP12 was recently described to recognize an antigen present on cell subpopulations of adult mouse bone marrow, including pluri‐potent hematopoietic stem cells. In an effort to understand the function of ER‐MP12 antigen in hematopoiesis, we used biochemical and physical methods to determine its identity. ER‐MP12 antigen was isolated by immunoprecipitation from FDCP‐1 cell membrane proteins, yielding a glycosylated 113‐kDa band upon analysis by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Thirteen peptides derived from trypsinized ER‐MP12 antigen were analyzed by electrospray ionization mass spectrometry and compared to a protein sequence database. The search revealed the identity of the ER‐MP12 antigen as platelet endothelial cell adhesion molecule‐1, CD31 (PECAM‐1). This result was subsequently confirmed by Edman sequencing of a single ER‐MP12 peptide fragment followed by comparison with PECAM‐1 sequence. In addition, flow cytometric analysis of bone marrow and embryonic stem cells revealed highly similar profiles between ER‐MP12 and CD31 (MEC 13.3 antibody)‐stained cells. The presence of PECAM‐1 on primitive hematopoietic stem cells supports the theory for the interaction of hematopoietic progenitor and stem cells with bone marrow stroma and transendothelial migration.
Sensitivity of Epstein‐Barr virus‐induced B cell tumor to apoptosis mediated by anti‐CD95/Apo‐1/fas antibody
Authors: Durandy Anne , Le Deist Françoise , Emile Jean‐François , Debatin Klaus , Fischer Alain 
Published: March 2007

AbstractEpstein‐Barr virus (EBV) can induce uncontrolled B lymphocyte proliferation leading to fatal lymphoma in immunocompromised patients. The sensitivity to apoptosis of B lymphoid cell lines (LCL) derived from EBV‐induced lymphopro‐liferative disorders was investigated. In vitro and in vivo, these B LCL strongly express CD95/Apo‐1/fas antigen and undergo apoptosis upon stimulation with anti‐Apo‐1 monoclonal antibody. When inoculated into severe‐combined immunodeficient (scid) mice, human B cells lines developed into rapidly growing tumors. Administration of an agonistic anti‐Apo‐1 antibody significantly delayed tumor progression. Relapses were frequent, but were not caused by selection of resistant B cells, since B cells from relapsing tumors underwent apoptosis on re‐exposure. Induction of apoptosis by an anti‐C95/Apo‐1/fas‐specific antibody could be applied for therapy of EBV‐induced B cell tumors and contribute to our understanding of the mechanisms of T cell‐mediated elimination of EBV lymphomas in immunodeficient patients.
Comparison of cytotoxic T lymphocyte responses induced by peptide or DNA immunization: Implications on immunogenicity and immunodominance
Authors: Vitiello Antonella , Sette Alessandro , Yuan Lunli , Farness Peggy , Southwood Scott , Sidney John , Chesnut Robert W. , Grey Howard M. , Livingston Brian 
Published: March 2007

AbstractTo study the mechanisms that influence the immunogenicity and immunodominance of potential cytotoxic T lymphocyte (CTL) epitopes, we conducted a systematic analysis of the CTL response raised in HLA‐A*0201/Kb (A2/Kb) transgenic mice against the viral antigen, hepatitis B virus polymerase (HBV pol). From a pool of 26 nonamer peptides containing the HLA‐A*0201‐binding motif, we selected A2‐binding peptides, immunized A2/Kb animals, and tested the CTL raised against the peptide for recognition of HBV pol transfectants. Of nine immunogenic CTL epitopes, only four were recognized on HBV pol transfectants, whereas the other five were cryptic. Characterization of the peptide‐specific CTL lines indicated that crypticity may result from either poor processing or low T cell receptor (TCR) avidity. To identify the immunodominant epitopes, we determined the CTL specificities induced in A2/Kb animals in response to priming with HBV pol cDNA. We obtained a response against three epitopes that were contained with the set of four epitopes recognized by peptide‐specific CTL on HBV pol transfectants. Comparative analysis of cDNA priming and peptide priming revealed, therefore, the presence of a subdominant epitope. We conclude that for the HBV pol antigen, the repertoire of CTL specificities is shaped by major histocompatibility complex class I peptide binding capacity, antigen processing, and TCR availability.
Csk overexpression reduces several monokines and nitric oxide productions but enhances prostaglandin E2 production in response to lipopolysaccharide in the macrophage cell line J774A.1
Authors: Iwabuchi Kazuya , Hatakeyama Shigetsugu , Takahashi Akio , Ato Manabu , Okada Masato , Kajino Yuri , Kajino Ki‐Ichi , Ogasawara Kazumasa , Takami Kimitaka , Nakagawa Hachiro , Onoé Kazunori 
Published: March 2007

AbstractThe catalytic activity of src‐family protein tyrosine kinases (src‐PTK) is suppressed when a C‐terminal tyrosine is phosphorylated by an intracellular PTK, C‐terminal Src kinase (Csk). In the present report, to study the regulatory functions of the Csk in cells of monocyte/macrophage lineage, we transfected a eukaryotic expression vector containing rat csk cDNA in a macrophage cell line, J774A.1, and examined alterations of the response to lipopolysaccharide (LPS) in the transfectants which overexpressed Csk. Csk overexpression resulted primarily in a down‐regulation of Fgr activity, an src‐PTK expressed in J774A.1, and hyperphosphorylation of several cellular proteins of 35, 57, 66, 97 and 120–130 kDa. Furthermore, in these Csk transfectants, production of interleukin (IL)‐1α, IL‐6, tumor necrosis factor‐α, and nitric oxide (NO) following LPS stimulation were reduced compared with those in parental J774A.1 or J774A.1 transfected with the vector alone. The extent of reduction paralleled the amounts of Csk proteins expressed in the Csk‐transfected J774A.1. The reduced NO production in these cells was associated with low levels of mRNA of inducible NO synthetase. On the other hand, an enhancement of prostaglandin E2 production was observed in the Csk‐transfected J774A.1 cells upon stimulation with LPS, which appeared to result from the high level of prostaglandin‐H synthetase in the transfectants. The present findings indicate that overexpression of Csk has differential effects on the regulation of production of chemical mediators and monokines, probably via modulation of signal transduction downstream of LPS‐mediated signals.
Immunomodulatory effects of a plasmid expressing B7‐2 on human immunodeficiency virus‐1‐specific cell‐mediated immunity induced by a plasmid encoding the viral antigen
Authors: Tsuji Takashi , Hamajima Kenji , Ishii Norihisa , Aoki Ichiro , Fukushima Jun , Xin Ke‐qin , Kawamoto Susumu , Sasaki Shin , Matsunaga Kei‐Ichiro , Ishigatsubo Yoshiaki , Tani Kenji , Okubo Takao , Okuda Kenji 
Published: March 2007

AbstractB7 co‐stimulation is essential for activating resting T cells following antigen recognition by the T cell receptor. To determine whether B7 has adjuvant activities on human immunodeficiency virus type‐1 (HIV‐1)‐specific immunity induced by inoculation of a plasmid encoding HIV‐1 env and rev (DNA vaccine), B7‐1 and B7‐2 expression plasmids were co‐inoculated with the DNA vaccine. The delayed‐type hypersensitivity response and cytotoxic T lymphocyte (CTL) activity were significantly enhanced when B7‐2 expression plasmid was co‐inoculated with the DNA vaccine, but were unaffected when the B7‐1 expression plasmid was used with the vaccine instead. The immunological response enhanced by B7‐2 decreased below the level of mice immunized with the DNA vaccine in combination with CTLA4Ig, an inhibitor of the B7/CD28 co‐stimulatory signal, suggesting that this signal is critical for the enhanced response induced by co‐inoculation of the DNA vaccine and B7‐2 expression plasmid. This enhancement appeared to occur via an interferon‐γ (IFN‐γ)‐dependent mechanism, as combined administration of the B7‐2 plasmid and neutralizing anti‐IFN‐γ antibody abrogated the virus‐specific cell‐mediated immunity. These results suggest that this gene‐based co‐inoculation strategy using HIV‐1 viral antigen and B7‐2 co‐stimulatory molecule could be a powerful means of combating HIV‐1 infection.