bluuebunny/crossref_metadata_2025_split huggingface dataset:
Signals through CD8 or CD4 can induce commitment to the CD4 lineage in the thymus
Authors: Bommhardt Ursula , Cole Michael S. , Yun Tso J. , Zamoyska Rose 
Published: March 2007

AbstractDifferentiation of thymocytes into mature single‐positive T cells is an ordered process involving sequential interactions between T cell receptor (TCR), coreceptors (CD4 or CD8) and their appropriate major histocompatibility complex‐encoded ligands. Precisely how these receptor/co‐receptor engagements determine lineage commitment is still controversial, but recently it has been suggested that quantitative differences in the signal transmitted by coligation of CD4 versus CD8 with TCR might provide the discriminating signal. We examine this hypothesis, using bispecific F(ab')2 antibodies to mimic TCR/co‐receptor engagement during thymocyte differentiation. These bispecific antibodies lack Fc and can engage surface molecules without extensive cross‐linking or targeting to Fc receptor‐bearing cells. We show that TCR/CD3 co‐ligation with CD4 induces efficient differentiation of mature CD4 lineage cells, irrespective of their TCR specificity. Interestingly, TCR/CD3 co‐ligation with CD8 also induces maturation of CD4T cells, although less efficiently, but not of CD8 T cells. Thus, although the signals delivered by co‐ligation of TCR and CD8 appear weaker than from co‐ligation of TCR and CD4, the outcome from either engagement is the same. These data suggest that differences in signal intensity alone do not determine lineage commitment in the thymus, but that distinct signals are required for CD4 and CD8 single‐positive cell differentiation.
Expression of class II, but not class I, major histocompatibility complex molecules is required for granuloma formation in infection with Schistosoma mansoni
Authors: Hernandez Hector J. , Wang Yong , Tzellas Nia , Stadecker Miguel J. 
Published: March 2007

AbstractPrevious studies have suggested that granulomatous inflammation in schistosomiasis is mediated by CD4+ T helper lymphocytes sensitized to parasite egg antigens. However, CD8+ T cells have also frequently been associated with the immune response to schistosome eggs. To examine more precisely the role of CD4+ and CD8+ T cells in the pathology of the schistosomal infection, we used mice with targeted mutations in major histocompatibility complex (MHC) class II or class I molecules. These mutations lead, respectively, to the virtual absence of CD4+ and CD8+ T cells. The results clearly show that schistosome‐infected MHC class II mutant mice failed to form granulomas around parasite eggs. In contrast, infected MHC class I mutant mice displayed characteristic granulomatous lesions that were comparable to those in wild‐type control mice. Moreover, lymphoid cells from MHC class II mutant mice were unable to react to egg antigens with either proliferative or cytokine [interferon‐gamma, interleukin (IL)‐4, IL‐10] responses; nor were they able to present egg antigens to specifically sensitized CD4+ T helper cells from infected syngeneic control mice. By comparison, cells from MHC class I mutant mice exercised all these functions in a manner comparable with those from wild‐type controls. These observations clearly demonstrate that schistosomal egg granulomas are mediated by MHC class II‐restricted CD4+ T helper cells. They also suggest that CD8+ T cells do not become sensitized to egg antigens and play little role, if any, in the pathogenesis of schistosomiasis.
Molecular cloning of the mouse proteasome subunits MC14 and MECL‐1: reciprocally regulated tissue expression of interferon‐γ‐modulated proteasome subunits
Authors: Stohwasser Ralf , Standera Sybille , Peters Inga , Kloetzel Peter‐M. , Groettrup Marcus 
Published: March 2007

AbstractThe primary structures of the interferon‐γ‐inducible mouse 20S proteasome subunit MECL‐1 and its alternate homolog MC14 were determined. Northern analysis of mouse tissues revealed that MECL‐1 mRNA predominantly occurred in thymus, lymph nodes, and spleen, whereas small amounts were detected in nonlymphoid tissues such as kidney, muscle, and testis. Unexpectedly, probing RNA blots with MC14 showed that tissues with high MECL‐1 expression contained little MC14 and vice versa. A very similar reciprocal tissue expression was subsequently found for the homologous subunit pairs LMP2 and δ as well as LMP7 and MB1. The subunit protein composition of 20S proteasomes purified from liver, thymus, and lung reflected RNA expression. The impact of a regulated reciprocal tissue expression is discussed with respect to thymic selection and the induction of tolerance in potentially autoreactive T cells.
Fibroblast dependency during early thymocyte development maps to the CD25+ CD44+ stage and involves interactions with fibroblast matrix molecules
Authors: Anderson Graham , Anderson Kim L. , Tchilian Elma Z. , Owen John J. T. , Jenkinson Eric J. 
Published: March 2007

AbstractWe have investigated the role of specific components of the thymic stroma during development of CD4− 8− T cell precursors by separating and reaggregating precursor subsets with individual or combinations of stromal cells. We show that while the development of CD25+44+ precursors is dependent upon a combination of major histocompatibility complex (MHC) class II+ thymic epithelial cells and fibroblasts, their direct descendants, CD25+ 44− precursors, develop to the CD4+8+ stage in the presence of MHC class II+ thymic epithelial cells alone. Thus, CD25+ 44+ precursors are the last developmental stage to be dependent upon fibroblast support. In addition, while metabolically inactive, 1‐ethyl‐3‐(3'‐dimethylaminopropyl)carbodiimide (ECDI)‐treated fibroblasts retain the ability to promote T cell development, prior treatment with hyaluronidase abrogates this effect, suggesting that fibroblast‐associated extracellular matrix components are the key elements involved. In support of this, we show that fibroblasts are located in cortical regions of the thymus where T cell precursors are known to reside, and that these fibroblasts are associated with an extensive extracellular matrix not found on thymic epithelial cells. Finally, antibodies to α4 integrin and CD44 interfere with the efficiency with which CD4+ 8+ cells are generated from CD25+ 44+ precursors in reaggregate cultures and also reduce the binding of the latter to 3T3 fibroblasts, suggesting these molecules play a role in bringing T cell precursors into contact with fibroblast‐associated extracellular matrix.
Human interdigitating dendritic cells directly stimulate CD40‐activated naive B cells
Authors: Björck Pia , Flores‐Romo Leopoldo , Liu Yong‐Jun 
Published: March 2007

AbstractHuman interdigitating dendritic cells (IDC) were isolated from tonsils based on their CD40+ lineage‐negative expression in situ. Isolated IDC displayed a phenotypic profile similar to that of IDC in tonsils and spleen in situ, characterized by high‐level expression of major histocompatibility complex class II, the co‐stimulatory molecules B7.1 (CD80) and B7.2 (CD86), expression of the late DC maturation marker CD83, and no expression of CD1a, CD13, or CD33. IDC also showed weak nonspecific esterase staining and had the ability to induce an allogeneic mixed lymphocyte reaction. In this study, we further show that in the presence of surrogate activated T cells in the form of CD40 ligation and IL‐2, IDC enhance the proliferation of naive B cells and induce their differentiation into plasma cells producing IgM. Evidence for the anatomical co‐localization of naive B cells and IDC in the T cell area together with the data obtained in vitro implies a role for IDC in the initiation of the extrafollicular reaction.
Penicilloyl peptides are recognized as T cell antigenic determinants in penicillin allergy
Authors: Padovan Elisabetta , Bauer Tanja , Tongio Marie Marte , Kalbacher Hubert , Weltzien Hans Ulrich 
Published: March 2007

AbstractAlthough hapten immune responses have been intensively studied in the mouse, very little is known about hapten determinants involved in human allergic reactions. Penicillins, as chemically reactive compounds of low molecular weight, constitute typical examples of hapten allergens for humans. Penicillins become immunogenic only after covalent binding to carrier proteins and in this form frequently induce IgE‐mediated allergic reactions in patients subjected to antibiotic treatment. However, our previous data strongly indicated that penicillins also form part of the epitopes contacting the antigen receptors of beta lactam‐specific T cells in allergic individuals. We have therefore investigated the molecular constraints involved in the T cell immune response to penicillin G (Pen G). Designer peptides containing a DRB1*0401‐binding motif and covalently modified with Pen G via a lysine σ‐amino group were found to induce proliferation of Pen G‐specific T cell clones. A precise positioning of the hapten molecule on the peptide backbone was required for optimal T cell recognition. Furthermore, we extended these observations from our designer peptides to show that a peptide sequence derived from a natural DRB1*1101‐binding peptide modified in vitro with Pen G, also acquired antigenic properties. Our data for the first time provide insight into the manner in which allergenic haptens are recognized by human T cells involved in allergic reactions to drugs and suggest possible mechanisms leading to the onset of these adverse immune responses.
TAP‐dependent major histocompatibility complex class I presentation of soluble proteins using listeriolysin
Authors: Darji Ayub , Chakraborty Trinad , Wehland Jürgen , Weiss Siegfried 
Published: March 2007

AbstractImmunization of mice with mixtures of listeriolysin, a pore‐forming hemolysin secreted by the pathogenic bacterium Listeria monocytogenes, together with soluble ovalbumin, nucleoprotein of influenza virus, or β‐galactosidase of Escherichia coli, resulted in strong cytotoxic CD8 T cell responses to each of the respective passenger proteins in vivo. Also, the concomitant addition of either protein with listeriolysin to target cells elicited efficient sensitization of these cells which could be attributed to the pore‐forming activity of listeriolysin. This response was dependent upon a functional TAP transporter and was inhibitable by brefeldin A, indicating the transfer of the soluble proteins into the cytosol and the classical major histocompatibility (MHC) class I presentation pathway. The treatment of target cells with listeriolysin under our experimental conditions did not affect cell viability and the pores generated by listeriolysin treatment were repaired within 60 min. Introduction of soluble proteins into the MHC class I presentation pathway by listeriolysin provides a powerful system to study the cytotoxic response towards intracellular pathogens and would allow for rapid screening of potential antigens in vaccine formulations.
L‐selectin ligands in rat high endothelium: multivalent sialyl Lewis x glycans are high‐affinity inhibitors of lymphocyte adhesion
Authors: Toppila Sanna , Lauronen Jouni , Mattila Pirkko , Turunen Juha Pekka , Penttilä Leena , Paavonen Timo , Renkonen Ossi , Renkonen Risto 
Published: March 2007

AbstractLymphocyte homing is initiated by their tethering to and rolling on the high endothelium and is followed by extravasation into the lymph nodes. We show here that glycosylated cell adhesion molecule‐1 (GlyCAM‐1), CD34, and sialyl Lewis x (sLex) are present on rat lymph node high endothelium analyzed by using monoclonal antibodies. α(1,3)fucosyltransferase VII (Fuc‐TVII), the last enzyme involved in the synthesis of the sLex sequence is also expressed on the rat lymph node high endothelium. We have synthesized a family of sLex‐decorated oligosaccharide structures and used them to inhibit lymphocyte binding to high endothelium in the Stamper‐Woodruff assay. Monovalent sLex, branched di‐ and tetravalent sLex, as well as a linear tetravalent sLex significantly reduce lymphocyte binding to endothelium. The branched and linear forms of tetravalent sLex were clearly superior inhibitors of the L‐selectin‐dependent lymphocyte adhesion, with IC50 values in low nanomolar range. In contrast, the fucose‐free analogs having the same charge and approximately the same size as the corresponding sLex glycans had no effect on lymphocyte binding and served as negative controls. Taken together, these data show the crucial importance of sLex in the endothelial ligands for L‐selectin. Furthermore, we suggest that L‐selectin acts as an oligomer on the lymphocyte surface as it binds multivalent sLex glycans.
Differential response of CD4+ V7+ and CD4+ V7− T cells to T cell receptor‐dependent signals: CD4+ V7+ T cells are co‐stimulation independent and anti‐V7 antibody blocks the induction of anergy by bacterial superantigen
Authors: Soares Luis R. B. , Rivas Alberto , Ruegg Curtis , Engleman Edgar G. 
Published: March 2007

AbstractV7 is a novel cell surface glycoprotein that is expressed on 25% of circulating T lymphocytes. This molecule appears to play a critical role in T cell activation based on the observation that a monoclonal anti‐V7 antibody inhibits T cell receptor (TCR)‐dependent interleukin‐2 (IL‐2) production and proliferation of T cells. In the current study, CD4+ V7+ and CD4+ V7− T cells were separated from one another and their response to various stimuli analyzed. Although there were only minor differences between the two subsets in the expression of activation/differentiation markers, including CD45RA and R0 isotypes, when exposed to immobilized anti‐CD3 or anti‐TCR antibodies in the absence of APC, CD4+ V7+ T cells alone produced IL‐2 and proliferated vigorously. By contrast, CD4+ V7− cells responded poorly to such stimuli, but they recovered their capacity to respond if antigen‐presenting cells (APC) or anti‐CD28 antibody were added to the cultures. The enhancement of the V7− T cell response by APC appears to be related to augmentation of TCR signals because the effect could be blocked by antibodies against molecules on APC [major histocompatibility (MHC) class II, CD86] that are known to up‐regulate such signals through their interaction with counter‐receptors on T cells. To assess the role of V7 in a system independent of co‐stimulation, CD4+ T cells were stimulated with the bacterial superantigens, staphylococcal enterotoxins A and B. The cells responded by proliferating and then becoming anergic. Addition of anti‐V7 antibody at the initiation of culture with superantigen did not inhibit cellular proliferation but prevented T cells from becoming anergic, while addition of anti‐CD28 antibody had no effect on either proliferation or anergy induction. These results indicate that V7 and CD28 mediate distinct intracellular signals and suggest that V7 functions to preserve T cell reactivity whether the stimulus is mitogenic or anergizing.
Characterization of mouse ALCAM (CD166): the CD6‐binding domain is conserved in different homologs and mediates cross‐species binding
Authors: Bowen Michael A. , Bajorath Jürgen , D'egidio Maurizia , Whitney Gena S. , Palmer Dawn , Kobarg Jörg , Starling Gary C. , Siadak Anthony W. , Aruffo Alejandro 
Published: March 2007

AbstractActivated leukocyte cell adhesion molecule (ALCAM; CD166) is a member of the immunoglobulin gene superfamily (IgSF) which is expressed by activated leukocytes and thymic epithelial cells and is a ligand for the lymphocyte antigen CD6. Herein, we report on the isolation and characterization of cDNA clones encoding mouse ALCAM (mALCAM). Comparison of the predicted amino acid sequence of mALCAM and human ALCAM (hALCAM) showed an overall identity of 93%. Binding studies with truncated forms of the extracellular region of mALCAM showed that the CD6 binding site is located in the N‐terminal Ig‐like domain and that mALCAM is capable of binding both human and mouse CD6. Mutagenesis studies on hALCAM suggested that residues critical for CD6 binding map to the predicted A‘GFCC’C″ β‐sheet of ALCAM's N‐terminal binding domain. Residue differences in the N‐terminal domains of mALCAM and hALCAM were analyzed with the aid of a molecular model of ALCAM. All residues critical for CD6 binding are conserved in both mALCAM and hALCAM, whereas residue differences map to the predicted BED face which is opposite the CD6 binding site on hALCAM. These findings provide a molecular rationale for the observed cross‐species CD6/ALCAM interaction and the apparent inability to generate monoclonal antibodies (mAb) against the CD6 binding site. RNA blot analysis showed that mRNA transcripts encoding mALCAM are expressed in the brain, lung, liver, and the kidney, as well as by activated leukocytes and a number of cell lines. A rat mAb specific for mALCAM was produced and by two‐color immunofluorescence studies was shown to bind to both activated CD4+ and CD8+ T cells.
Combined structural and immunological refinement of HIV‐1 HLA‐B8‐restricted cytotoxic T lymphocyte epitopes
Authors: Goulder Philip J. R. , Reid Scott W. , Price David A. , O'callaghan Chris A. , McMichael Andrew J. , Phillips Rodney E. , Yvonne Jones E. 
Published: March 2007

AbstractThis study demonstrates that use of structural information improves the definition and optimization of cytotoxic T lymphocyte (CTL) epitopes. Epitope optimization usually requires numerous truncated peptides or a reverse immunogenetic approach, where the peptide binding motif is used to predict epitopes. These binding motifs do not reliably predict all peptides which are CTL epitopes. Comparison of 24 peptides eluted from HLA‐B8 with 10 HLA‐B8‐restricted defined CTL epitopes demonstrated that known epitopes varied considerably at anchor positions. We used structural information based on determination of the crystal structure of the HLA‐B8‐GGKKKYKL complex to reassess previously described CTL epitopes, to predict new epitopes, and to predict the consequences of naturally occurring variation within epitopes. These predictions were confirmed by cytotoxicity and binding assays. Use of combined structural and immunological data more accurately defines the true peptide‐binding motif of a restriction element than eluted peptide data allows.
The C terminus of the human C5a receptor (CD88) is required for normal ligand‐dependent receptor internalization
Authors: Bock Daniel , Martin Ulrich , Gärtner Sören , Rheinheimer Claudia , Raffetseder Ute , Arseniev Lubomir , Barker Mike D. , Monk Peter N. , Bautsch Wilfried , Köhl Jörg , Klos Andreas 
Published: March 2007

AbstractThe biological effects of the potent inflammatory mediator C5a, a complement split product, on human neutrophils and monocytes are limited by the rapid internalization of its specific receptor (C5aR, CD88). The C terminus of the C5aR is phosphorylated after stimulation with C5a of phorbol ester, and this phosphorylation might lead to receptor internalization. In this context, we have studied the effects on C5aR internalization of C5a, phorbol 12‐myristate 13‐acetate (PMA), the protein kinase inhibitor staurosporine, and pertussis toxin on rat basophilic RBL.2H3 cells stably transfected with the human wild‐type or mutant C5aR. C5aR mutants lacked either part of the cytosolic C terminus, including suggested major phosphorylation sites, or a putative phosphorylation motif for protein kinase C in the third cytosolic loop. Additionally, agonist‐induced internalization was analyzed on HEK293 cells co‐transfected with C5aR and the pertussis toxin‐resistant G protein alpha subunit, Gα16. Staurosporine‐sensitive agonist‐dependent C5aR internalization could be detected, suggesting that C5aR phosphorylation, most likely of the C terminus, participates in this type of internalization. In contrast, PMA‐induced C5aR internalization seems to be independent of putative phosphorylation sites in either the truncated section of the C terminus or the third cytosolic loop. The phorbol ester‐induced C5aR internalization may, therefore, be caused by an indirect and less specific effect of protein kinase C on the internalization machinery. Manipulation of the pertussis toxin‐sensitive or ‐resistant G protein‐dependent signal transduction had no effect on ligand‐induced internalization.
Cyclosporin A interferes with the inducible degradation of NF‐xB inhibitors, but not with the processing of p105/NF‐xB1 in T cells
Authors: Marienfeld Ralf , Neumann Manfred , Chuvpilo Sergei , Escher Cornelia , Kneitz Burkhard , Avots Andris , Schimpl Anneliese , Serfling Edgar 
Published: March 2007

AbstractThe transcription factor NF‐xB controls the induction of numerous cytokine promoters during the activation of T lymphocytes. Inhibition of T cell activation by the immunosuppressants cyclosporin A (CsA) and FK506 exerts a suppressive effect on the induction of these NF‐xB‐controlled cytokine promoters. We show for human Jurkat T leukemia cells, as well as human and mouse primary T lymphocytes, that this inhibitory effect is accompanied by an impaired nuclear translocation of the Rel proteins c‐Rel, RelA/p65 and NF‐xB1/p50, whereas the nuclear appearance of RelB remains unaffected. CsA does not interfere with the synthesis of Rel proteins, but prevents the inducible degradation of cytosolic NF‐xB inhibitors IxBα and IxBβ upon T cell activation. CsA neither inhibits the processing of the NF‐xB1 precursor p105 to p50, nor does it “stabilize” the C‐terminal portion of p105, IxBγ, which is degraded during p105 processing to mature p50. These results indicate that CsA interferes with a specific event in the signal‐induced degradation of IxBα and IxBβ, but does not affect the processing of NF‐xB1/p105 to p50.
Germ‐line transcription and methylation status of the TCR‐Jα locus in its accessible configuration
Authors: Villey Isabelle , Quartier Pierre , Selz Françhise , de Villartay Jean‐Pierre 
Published: March 2007

AbstractWe have generated two in vivo mouse models to study the regulation of DNA accessibility to the V(D)J recombinase machinery in the T cell receptor (TCR)‐Jα locus. In recombination activating gene (RAG)‐deficient mice, both injection of a TCR‐β chain transgene (RTB mice) or anti‐CD3‐ε treatment in vivo (RT3 mice) lead to the same phenotype with homogeneous thymocyte populations blocked at the CD4+CD8+ double positive (DP) stage. At this developmental stage, the TCR‐α rearrangements are about to start, and the TCR‐Jα locus is frozen in an accessible but yet unrearranged configuration in these mice. We show high level of TCR‐α germ‐line transcription in thymocytes from RTB and RT3 mice. Transcripts are skewed towards the 5′ end of the TCR‐Jα locus, and the T early alpha (TEA) sterile transcript is predominant and therefore provides a useful marker for the TCR‐Jα locus opening. Analysis of the DNA methylation status reveals a global surmethylation of the TCR‐Jα locus in the thymus in comparison with non‐lymphoid cells in these mice. We propose that hypermethylation of the locus could precede a progressive demethylation, providing a specific protective and regulatory role in the rearrangement events.