bluuebunny/crossref_metadata_2025_split huggingface dataset:
T cell receptor α‐chain tail is required for protein kinase C‐mediated down‐regulation, but not for signaling
Authors: Thomas Bäckström B. , Rubin Bent , Peter Annick , Tiefenthaler Georg , Palmer Ed 
Published: March 2007

AbstractAntigen stimulation through the T cell receptor (TCR) induces phosphorylation of the associated CD3 γδσ‐ and ζ‐chain cytoplasmic tails. These events lead to the induction of the intracellular signaling pathways with concomitant receptor down‐regulation. The TCR is down‐regulated from the cell surface by the activation of protein kinase C (PKC) and subsequent serine phosphorylation of the CD3 γ‐chain. We report here that the TCR α‐chain cytoplasmic tail is also necessary for PKC‐mediated internalization of the TCR complex. The requirement for the TCR α‐chain cytoplasmic tail is specific for internalization of the TCR complex, since down‐regulation of CD4 is still intact in hybridoma cells expressing a tailless TCR α‐chain. The absence of TCR internalization directly correlates with defective PKC‐mediated phosphorylation of the CD3 γ‐chain. Despite deficient PKC‐mediated TCR down‐regulation, the tailless αβ TCR still transduces antigenic signals resulting in the production of interleukin‐2. Although the TCR tails are not obviously required for signal transduction, the TCR α‐tail may serve as a targeting domain for PKC‐mediated down‐regulation of the TCR complex.
Late events in the intracellular sorting of major histocompatibility complex class II molecules are regulated by the 80‐82 segment of the class II β chain
Authors: Tan L. J. , Ceman Stephanie , Chervonsky Alexander , Rodriguez‐Paris Juan , Steck Theodore L. , Sant Andrea J. 
Published: March 2007

AbstractThe molecular mechanisms that regulate sorting of major histocompatibility complex (MHC) class II molecules into the endocytic pathway are poorly understood. For many proteins, access to endosomal compartments is regulated by cytosolically expressed sequences. We present evidence that a sequence in the lumenal domain of the MHC class II molecule regulates a very late event in class II biogenesis. Class II molecules containing single amino acid changes in the highly conserved 80–82 region of the β chain were introduced into invariant chain (Ii)‐negative fibroblasts with wild‐type α chain, and the derived transfectants were analyzed biochemically. Using an endosomal isolation technique, we have quantified the level of class II molecules expressed in endocytic compartments and found that in the absence of Ii, approximately 15% of total cellular class II molecules can be isolated from endosomal compartments. Mutation at position 80 enhances this localization, while changes at positions 81 and 82 ablate class II expression in endosomal compartments. In addition, we have evaluated whether the induced changes in intracellular distribution of class II molecules were due to alterations in early biosynthetic events, indicative of misfolding of the molecules, or to modulation of later trafficking events more likely to be a consequence of the modulation of a specific transport event. Despite the dramatic effects on endosomal localization induced by the mutations, early bio‐synthetic events and maturation of class II were unaffected by the mutations. Collectively, our data argue that late trafficking events that control the ability of the class II molecule to access antigens is regulated by the 80–82 segment of the MHC class II β chains.
Clustering the adhesion molecules VLA‐4 (CD49d/CD29) in Jurkat T cells or VCAM‐1 (CD106) in endothelial (ECV 304) cells activates the phosphoinositide pathway and triggers Ca2+ mobilization
Authors: Ricard Isabelle , Payet Marcel D. , Dupuis Gilles 
Published: March 2007

AbstractLigation of very late antigen (VLA)‐4 (α4β1 integrin) with a cross‐linked anti‐α4 subunit monoclonal antibody (mAb) triggered a biphasic Ca2+ response in Jurkat cell populations and in peripheral human lymphocytes. Cross‐linking vascular cell adhesion molecule (VCAM)‐1 (the counter‐receptor of VLA‐4) in ECV 304 endothelial cells generated a biphasic Ca2+ response. Tumor necrosis factor‐α‐primed human umbilical cord vascular endothelial cells also responded to the cross‐linked mAb with a biphasic Ca2+ profile. Ligated VLA‐4 (Jurkat cells) or VCAM‐1 (ECV 304) stimulated the production of myo‐inositol 1,4,5‐trisphosphate. ECV 304 cells induced a biphasic Ca2+ response in Fura2‐loaded Jurkat cells, whereas a transient response was observed when Jurkat cells were added to Fura2‐loaded ECV 304 cells. The Ca2+ responses in these experiments involved VLA‐4/VCAM‐1 interactions since they were significantly reduced (∼ 80%) by prior treatment of the target cells with the relevant noncross‐linked mAb. Close contact between the cells triggered mutual Ca2+ signaling as shown by spectrofluorimetric and confocal microscopy time‐dependent recordings. Fibronectin and its CS‐1 fragment (V25) triggered a sustained Ca2+ response in Jurkat cells (confocal microscopy). Our results suggest that the VLA‐4 and VCAM‐1 adhesion molecules can transduce a signal that involves activation of the phosphoinositide pathway and the mobilization of Ca2+.
Single‐cell analyses of CD4+ T cells from αβ T cell receptor‐transgenic mice: a distinct mucosal cytokine phenotype in the absence of transgene‐specific antigen
Authors: Saparov Arman , Elson Charles O. , Devore‐Carter Denise , Bucy R. Pat , Weaver Casey T. 
Published: March 2007

AbstractDevelopment of distinct CD4+ T cell cytokine phenotypes may be conditioned by the anatomic site in which activation occurs. A double‐label in situ hybridization technique was used to characterize co‐expression of cytokine mRNA in antigen‐specific responses of Peyer's patch (PP), lamina propria (LP), and splenic (SP) CD4+ T cells isolated from αβ T cell receptor‐transgenic mice. Interleukin (IL)‐2 was the dominant cytokine expressed by antigen‐stimulated PP and SP populations, though it was expressed by a minority of the activated T cells. Cells that expressed interferon (IFN)‐γ were less frequent, and IL‐4, IL‐5, and IL‐10 were infrequent. In contrast, cells that expressed IFN‐γ or IL‐10 were most frequent in the LP population, with lower frequencies of IL‐2, and few IL‐4‐ and IL‐5‐positive cells. Co‐expression of two cytokines by the same cell was the exception, regardless of the anatomic site from which the T cells were isolated. The surface phenotype of transgene‐positive T cells isolated from each anatomic site was distinct, despite the absence of in vivo exposure to antigen for which the transgenic T cell receptor is specific. These data suggest that the cytokine responses of CD4+ T cells may be conditioned by the microenvironment, independently of specific antigen, and that the LP CD4+ T population has a distinct cytokine expression pattern with counter‐regulatory properties that may be important for homeostasis in mucosal immune tissues.
An example of idiotypic mimicry
Authors: Grandien Alf , Andersson Jan , Portnoi Denis , Coutinho Antonio 
Published: March 2007

AbstractWe have evaluated the impact of transgenic immunoglobulin (TGIg) expression on endogenous antibody repertoires. The transgenic system was chosen as to allow for normal recombination of endogenous Ig genes, secretion of TGIg from early development on, and distinguishing the TGIg from endogenous Ig by several serological markers on the C and V regions of the molecules. The transgenic construct encodes a complete anti‐(4‐hydroxy‐3‐iodo‐5‐nitrophenyl)acetyl (NP) antibody molecule carrying a well‐defined idiotype, bearing a λ1 light chain and a chimeric heavy chain encoded by a human α2 C region devoid of its membrane exon, and the murine B1.8 VDJ‐region. Endogenous antibody repertoires were analyzed in mitogen‐driven limiting dilution cultures, in single‐cell assays for naturally activated Ig‐secreting cells, and in hybridomas derived by direct fusion of spleen cells from unmanipulated animals. The results show that a very high frequency of splenic resting B cells and plasma cells in transgenic animals produce IgM with B1.8‐cross‐reactive idiotypes. This was confirmed by hybridoma analysis which also established that the levels of transgene expression and of idiotype‐positive IgM production by the same cell are not correlated. The affinities of idiotype‐positive endogenous Ig varied, but were generally several orders of magnitude lower than the transgene‐encoded idiotype. V regions from idiotype‐cross‐reactive IgM heavy chains showed marked diversity in sequences that were all different from the transgenic B1.8. These results are compatible with idiotypic mimicry resulting from intercellular selection based on degenerate, whole V region reactivities.
Molecular cloning of human RP105
Authors: Fugier‐Vivier Isabelle , de Bouteiller Odette , Guret Christiane , Fossiez François , Banchereau Jacques , Mattei Marie‐Geneviève , Aït‐Yahia Smina , Garcia Eric , Lebecque Serge , Liu Yong‐Jun 
Published: March 2007

AbstractRP105 is a 105‐kDa type I membrane protein of the leucine‐rich repeat (LRR) family. Anti‐RP105 sensitizes B cells to antigen‐receptor‐mediated apoptosis, but protects B cells from radiation‐induced apoptosis and stimulates B cell proliferation. The sequence of the mouse RP105 has been reported. Here, we report the characterization of the human RP105. The 2.6‐kb cDNA encodes a protein of 661 amino acids which displays 78% homology with mouse RP105. The 22 LRR and the 9 potential N‐linked glycosylation sites within the extracellular region are conserved. While previous studies have shown that RP105 is expressed on surface IgM+IgD++ B cells in mice, human RP105 was shown to be expressed on all subsets of mature B cells and dendritic cells. Human RP105 gene was mapped to the long arm of chromosome 5, where numerous cytokines and receptors have been localized.
HLA‐G recognition by human natural killer cells. Involvement of CD94 both as inhibitory and as activating receptor complex
Authors: Pende Daniela , Sivori Simona , Accame Laura , Pareti Laura , Falco Michela , Geraghty Dan , Le Bouteiller Philippe , Moretta Lorenzo , Moretta Alessandro 
Published: March 2007

AbstractThe lack of classical human histocompatibility leukocyte antigen (HLA) molecules in human placenta prevents the recognition and lysis by maternal T lymphocytes but poses the problem of susceptibility to natural killer (NK) cell‐mediated lysis. The nonclassical HLA class I molecule HLA‐G may mediate protection from NK cells. NK cells are known to express a number of HLA class I‐specific inhibitory receptors. These include members of the immunoglobulin (Ig) superfamily (p58, p70, p140), characterized by a defined allele specificity, and CD94/NKG2A with a broad specificity for different HLA class I molecules. We analyzed a series of NK cell clones derived from normal peripheral blood expressing different NK receptors (NKR). Clones were analyzed for their cytolytic activity against the HLA class I‐negative 221 cell line either untransfected or transfected with HLA‐G (221/G) or other informative alleles, as control. All clones expressing CD94/NKG2A [as identified by the Z199 monoclonal antibody (mAb)] displayed a markedly reduced cytolytic activity against 221/G. Moreover, mAb directed to the CD94/NKG2A complex completely restored target cell lysis. Among NKG2A‐negative NK clones, different functional patterns could be detected. Clones expressing inhibitory receptors belonging to the Ig superfamily lysed 221/G target cells with equal or higher efficiency than untransfected 221 cells. These data indicated that p58, p70 and p140 do not function as HLA‐G‐specific inhibitory NKR, and that HLA‐G‐specific activating NKR also exist. Further analysis indicated that in these clones (characterized by the CD94+/NKG2A− phenotype) mAb specific for CD94, but not for the other NKR, reversed the activating effect. Infrequent clones were also isolated that, in spite of the lack of CD94/NKG2A, displayed HLA‐G specificity, thus suggesting the existence of a different, still unknown NKR.
Reduced intracellular oxidative metabolism promotes firm adhesion of human polymorphonuclear leukocytes to vascular endothelium under flow conditions
Authors: Montoya María C. , Luscinskas Francis W. , del Pozo Miguel A. , Aragonés Julían , de Landázuri Manuel O. 
Published: March 2007

AbstractThe interaction of polymorphonuclear leukocytes (PMN) with the vascular endothelium and their subsequent extravasation to the tissues is a key step during different physiological and pathological processes. In certain of these pathologies the oxygen tension becomes very low, leading to reduced cellular oxidative status. To evaluate the effect of lowering the intracellular redox status in the interaction of PMN with the endothelium, exposure to hypoxic conditions as well as treatment with different antioxidant agents was carried out. PMN exposure to hypoxia enhanced β2 integrin‐dependent adhesion to intercellular adhesion molecule‐1‐coated surfaces, concomitant with a decrease in the intracellular redox status of the cell. As occurs with hypoxia, treatment with antioxidants produced a decrease in the oxidation state of PMN. These agents enhanced adhesion of PMN to human umbilical vein endothelial cells stimulated with tumor necrosis factor‐α (TNF‐α), and this effect was also mediated by β2 integrins LFA‐1 and Mac‐1. Adhesion studies under defined laminar flow conditions showed that the antioxidant treatment induced an enhanced adhesion mediated by β2 integrins with a decrease in the fraction of PMN rolling on TNF‐α‐activated endothelial cells. The up‐regulated PMN adhesion was correlated to an increase in the expression and activation of integrin Mac‐1, without loss of L‐selectin surface expression. Altogether, these results demonstrate that a reduction in the intracellular oxidative state produces an enhanced β2 integrin‐dependent adhesion of PMN to stimulated endothelial cells under conditions of flow.
CD28 is not required for rejection of unmanipulated syngeneic and autologous tumors
Authors: Wen Tao , Kono Koji , Shahinian Arda , Kiessling Rolf , Mak Tak W. , Klein George 
Published: March 2007

AbstractTo gain a better understanding of the requirement of CD28 co‐stimulation in different types of T cell‐dependent tumor rejection responses, we performed a series of syngeneic and autologous tumor rejection experiments on CD28 knockout mice. In a preimmunization‐challenge model, virally‐induced ALC lymphoma and methylcholanthrene‐induced MC57X fibrosarcoma transplants were rejected similarly by syngeneic CD28 knockout and immunocompetent controls. ALC‐specific cytotoxic T lymphocytes (CTL) and MC57X‐specific tumor necrosis factor (TNF) release were induced in CD28 knockouts, although at a reduced level in the latter case. Secondly, the spontaneous regression of Moloney murine sarcoma virus (MMSV)‐induced primary tumors in the autologous hosts occurred equally in CD28 knockouts and in immunocompetent control mice. A comparable virus‐specific CTL response was generated in both, as revealed in cytolytic assays against RBL‐5 targets. Thirdly, the spontaneous rejection of the B7‐transfected EL‐4 lymphoma by immunocompetent hosts was abrogated in CD28 knockout mice, since more than 82% CD28 knockouts developed tumors after inoculation with B7‐transfected EL‐4 cells. Our results therefore show that CD28 co‐stimulatory molecules are not required for the rejection of unmanipulated syngeneic tumors in hyperimmunized hosts and the regression of MMSV‐induced sarcoma in autochthonous hosts.
Lymphotoxin but not tumor necrosis factor functions to maintain splenic architecture and humoral responsiveness in adult mice
Authors: Mackay Fabienne , Majeau Gerard R. , Lawton Pornsri , Hochman Paula S. , Browning Jeffrey L. 
Published: March 2007

AbstractTo compare the function of the tumor necrosis factor (TNF) and lymphotoxin (LT)α/β systems in the mature immune system, these two pathways were blocked with soluble receptor‐immunoglobulin (R‐Ig) fusion proteins in normal adult mice. Inhibition of LTα/β signaling using LTβR‐Ig or a blocking monoclonal antibody against murine LTβ had profound effects. The spleen lacked discrete B cell follicles and the marginal zone was altered. Less marked changes were detected in lymph nodes. LTα/β inhibition also prevented germinal center formation in the spleen and impaired Ig production in response to sheep red blood cells (SRBC) immunization. These results show that the LTα/β system is required for the maintenance of splenic architecture and normal immune responses, and not simply for the development of peripheral immune organs during ontogeny. In contrast, inhibition of the TNF/LTα pathway with TNF‐R55‐Ig did not affect the splenic architecture or the anti‐SRBC response. Splenic defects and impaired antibody responses are seen in TNF‐deficient mice, suggesting that TNF is important during development. Therefore relative to TNF, the LT system has the dominant influence on splenic organization and anti‐SRBC Ig formation in the adult mouse.
Positive and negative thymic selection in T cell receptor‐transgenic mice correlate with Nur77 mRNA expression
Authors: Xue Yintong , Chomez Patrick , Castanos‐Velez Esmeralda , Biberfeld Peter , Perlmann Thomas , Jondal Mikael 
Published: March 2007

AbstractThe orphan nuclear receptor Nur77 has been implicated in thymic negative selection. We studied the effect of two T cell receptor (TCR) transgenes on positive selction and Nur77 mRNA expression in thymus. DO11.10 mice, expressing a transgenic TCR specific for an ovalbumin (OVA) 323–339 peptide presented by I‐Ad, were found to have an enlarged thymus with a reduced apoptotic activity, measured by flow cytometry, reduced mitochondrial membrane potential and terminal deoxynucleotidyl transferase‐mediated dUTP nick end labeling (TUNEL) techniques. In contrast, in F5 mice expressing a transgenic TCR recognizing the influenza virus nucleoprotein (NP) 366–374 peptide restricted by Db, this positive selection effect was much less pronounced. Positive thymic selection in DO11.10 TCR+ mice correlated with a reduced level of Nur77 mRNA expression shown by Northern blot. F5 mice expressed levels close to those expressed by the wild type. Both transgenic mouse strains responded with extensive cortical apoptosis, and with up‐regulation of Nur77 mRNA, to injection of cognate peptides. As 9‐cis‐Retinoic acid (9‐cis‐RA) inhibits Nur77‐dependent apoptosis in T cell hybridomas in vitro, mice were pretreated with the drug to investigate a similar effect in vivo. However, the drug itself, at saturating concentrations, caused extensive apoptosis in immature CD4+/CD8+ thymocytes. The result demonstrates a correlation between Nur77 expression and thymic apoptotic activity, both during positive and negative selection events.
Location‐specific regulation of transgenic Ly49A receptors by major histocompatibility complex class I molecules
Authors: Fahlén Linda , Khoo Nelson K. S. , Daws Michael R. , Sentman Charles L. 
Published: March 2007

AbstractInhibitory receptors expressed on natural killer (NK) cells and T cells specific for major histocompatibility complex (MHC) class I are believed to prevent these cells from responding to normal self tissues. To understand the regulation and function of Ly49 receptor molecules in vivo, we used the CD2 promoter to target Ly49A expression to all thymocytes, T cells, and NK cells. In animals expressing its MHC class I ligand, H‐2Dd or H‐2Dk, there was a large decrease in the expression of Ly49A on thymocytes, peripheral T cells, and NK1.1+ cells. The extent of the down‐regulation of Ly49A was dependent on the expression of the MHC ligand for Ly49A and on the site where the cells were located. The level of expression of endogenous Ly49A was similarly found to be dependent upon the organ where the cells resided. Data from bone marrow chimeras indicated that most cell types may regulate Ly49A expression, but the efficacy to regulate receptor expression may vary depending on the cell type.
Two murine homologues of the human chemokine receptor CXCR4 mediating stromal cell‐derived factor 1α activation of Gi2 are differentially expressed in vivo
Authors: Moepps Barbara , Frodl Reinhard , Rodewald Hans‐Reimer , Baggiolini Marco , Gierschik Peter 
Published: March 2007

AbstractPrevious results have shown that pertussis toxin‐sensitive Gi proteins are likely to be involved in regulating the emigration of mature thymocytes from the thymus. In this study, a low stringency polymerase chain reaction (PCR) approach was used to identify Gi protein‐coupled cell surface receptors expressed in mouse thymocytes. Among the ten G protein‐coupled receptor cDNA isolated, the most prevalent cDNA encoded a polypeptide highly homologous to the human leukocyte‐expressed seven‐transmembrane‐domain receptor LESTR, also referred to as HIV entry cofactor, fusin, or CXCR4. Isolation of full‐length cDNA revealed that alternative RNA splicing produces transcripts encoding two isoforms of the murine LESTR, differing by the presence of two amino acids in the N‐terminal portion of the longer protein. Functional reconstitution of recombinant murine LESTR with recombinant heterotrimeric G proteins in baculovirus‐infected insect cells showed that both receptor variants mediate stromal cell‐derived factor 1α activation of the pertussis toxin‐sensitive G protein Gi2. Receptor subtype‐specific reverse transcriptase‐PCR analysis revealed differential expression of the two receptor mRNA in lymphoid tissues and brain, indicating that distinct functions are mediated by the two receptor isoforms in these tissues. The presence of LESTR mRNA in very early thymocytes as well as in immature (CD4+ CD8+) thymocytes suggests that both CD4 and LESTR are co‐expressed and render developing human thymocytes susceptible for HIV entry, which may affect generation of both CD4+ CD8− and CD4− CD8+ mature lineages.
B cell‐deficient μMT mice as an experimental model for Mycoplasma infections in X‐linked agammaglobulinemia
Authors: Berglöf Anna , Sandstedt Karin , Feinstein Ricardo , Bölske Göran , Smith C. I. Edvard 
Published: March 2007

AbstractB cell‐deficient μMT mice were investigated as an experimental model for human X‐linked agammaglobulinemia (XLA). Mice were intranasally infected with Mycoplasma pulmonis and in 16 out of 17 μMT mice, dissemination of the bacteria from the airways was observed. More than 50% of these mice developed arthritis and/or changes in periarticular tissues. Mycoplasmal infection in μMT mice thus resembles the disease seen in XLA patients implying the usefulness of the model.