bluuebunny/crossref_metadata_2025_split huggingface dataset:
CD28:B7 interactions promote T cell adhesion
Authors: Turcovski‐Corrales Susan M. , Fenton Robert G. , Peltz Gary , Taub Dennis D. 
Published: March 2007

AbstractCD28 activation by antibody‐mediated ligation has been shown to provide an important co‐stimulatory signal for T cell adhesion to purified protein ligands. However, the effect of CD28 ligation by one of its natural ligands, B7.1, on T cell adhesion to other cells has not been studied. Therefore, in the present manuscript, we characterized the adhesive interactions between human T cells and B7.1‐transfected major histocompatibility complex class II+ and class II− melanoma cells. In our studies, human T cells and T cell clones adhered to B7.1‐transfected melanoma cells, but not to untransfected parental cells. The adhesive reaction in this model was rapid, occurring within 15 min, and was inhibited by anti‐B7.1 antibody and soluble CTLA‐4 immunoglobulin. Antibody inhibition studies demonstrated that adhesion between T cells and B7.1‐transfected melanoma cells was mediated by interactions between LFA‐1:ICAM‐1 and CD2:LFA‐3. Inhibition by pharmacological agents demonstrated that the CD28‐induced adhesion required specific intracellular signaling events. A protein kinase C inhibitor, staurosporin, significantly inhibited T cell binding to transfected melanoma cells, while cyclosporin A and wortmannin, an inhibitor of phosphatidylinositol‐3‐kinase, did not. These results suggest that the presence of B7 on various cell populations may activate lymphocytes to adhere better, thus promoting activation, cytolysis, and migration.
Pertussis toxin‐sensitive GTP‐binding proteins regulate activation‐induced apoptotic cell death of human natural killer cells
Authors: Carracedo Julia , Ramírez Rafael , Marchetti Philippe , Pintado Oscar C. , Baixeras Elena , Martínez Carlos , Kroemer Guido 
Published: March 2007

AbstractApoptosis of natural killer (NK) cells can be induced by non‐specific physical damage (UV irradiation, heat shock) or by simultaneous ligation of the CD 16 and the interleukin‐2 receptor (IL‐2R) molecules, but not with either anti‐CD 16 or IL‐2 alone. Whereas blockade of GTP‐binding protein (G protein)‐mediated signal transduction using ADP‐ribosylating bacterial toxins or the GTPase‐resistant GTP analog guanosine 5′‐0‐(3‐thiotriphosphate (GTPγS) does not affect non‐specific induction of NK cell apoptosis, such interventions do inhibit induction of apoptosis by anti‐CD16/IL‐2. The G proteins involved in the regulation of activation‐induced NK apoptosis are sensitive to pertussis toxin (PTX) and to the non‐specific GTP analog GTPγS but not to cholera toxin, Pseudomonas exotoxin A or diphtheria toxin. A pertussis toxin mutant that lacks ADP‐ribosylating activity, but conserves the membrane translocating and T cell‐mitogenic effects of the native molecule, fails to inhibit NK apoptosis. To exert their apoptosis‐inhibitory effect, PTX and GTPγS must be employed before cells are activated. Later addition has no effect, suggesting the implication of G proteins in the transmission of apoptosis‐inducing signals, but not in the effector stage of apoptosis. Pre‐incubation with PTX or GTPγS does not affect the activation of NK cells by CD 16 cross‐linking, IL‐2 stimulation ‐ or both, as assessed by the induction of CD69 expression, protein tyrosine phosphorylation and calcium mobilization. Moreover, neither PTX nor GTPγS compromise the effector function of NK cells or the susceptibility of target cells to NK‐mediated lysis. These data suggest apoptosis as a novel mechanism by which NK responses may be controlled in vivo, as well as an experimental and therapeutical strategy to counteract endogenous down‐regulation of NK responses.
Dendritic cells generated from peripheral blood transfected with human tyrosinase induce specific T cell activation
Authors: Alijagic Selma , Möller Peter , Artuc Metin , Jurgovsky Klaus , Czarnetzki Beate M. , Schadendorf Dirk 
Published: March 2007

AbstractPeptides of melanosomal proteins have recently been shown to be recognized in an HLA‐restricted mode by specific cytolytic T lymphocytes in melanoma patients. Dendritic antigen‐presenting cells (DC) are considered to be the most effective stimulators of T cell responses, and the use of these cells has therefore been proposed to generate therapeutic responses to tumor antigens in cancer patients. We, therefore, generated DC from peripheral blood of normal donors in the presence of granulocyte/macrophage colony‐stimulating factor and interleukin‐4. Flow cytometric analysis of the cells during a 2‐week culture revealed a loss of CD14 and CD34 expression, a concomittent increase of CD1a, CD11a, b and c, CD44, CD45, CD54, HLA‐class I and II, and intermediate levels of CD26, CD80 and CD86. Cultured DC stimulated proliferation of allogeneic T cells and induced a marked, up to 20‐fold, stimulation of T cell proliferation after pulsing with tetanus toxoid. To achieve independence of already‐identified antigenic peptides presented in HLA class I‐restricted fashion, which limits the general applicability of such peptides for vaccination of melanoma patients, we tested whether DC are transfectable with eukaryotic expression plasmids. DC transfected with two reporter genes (CAT, β‐galactosidase) using a liposome‐based transfection technique, exhibited only low levels of enzymatically active proteins, but were able to degrade rapidly intracellular proteins and to process peptides efficiently. Chloramphenicol acetyltransferase as well as tyrosinase mRNA were detectable after transfection by reverse‐transcriptase‐polymerase chain reaction, and enzyme activities became measurable. Furthermore, DC transfected with the tyrosinase gene were able to induce specific T cell activation in vitro, indicating appropriate peptide processing and presentation in DC after transfection. These data suggest new approaches to future tumor vaccination strategies.
Immature B cells from human and mouse bone marrow can change their surface light chain expression
Authors: Ghia Paolo , Gratwohl Alois , Signer Erich , Winkler Thomas H. , Melchers Fritz , Rolink Antonius G. 
Published: March 2007

AbstractThe capacity of bone marrow‐derived surface immunoglobulin‐positive (sIg+) human and mouse immature B cells, generated either in vitro or in vivo, to change their light (L) chain expression, has been assayed by the number of cells which change in vitro from one type of L chain to the other type, or to no sIg at all. Immature sIg+ B cells were generated in vitro from sIg− precursor cells from human or mouse bone marrow. The immature sIg+ cells expressed RAG‐1. Human sIg+ cells expressed xfr; and λ L chains in ratios between 1:1 and 3:1, whereas in mouse cells, this ratio ranged from 10:1 to 20:1. Upon reculture of the human and mouse xfr;+sIg+ cells, about half of them remained xfr;+, a quarter became λ+, and another quarter became sIg−. Between 1 and 3% expressed both xfr; and λ chains. Of the human λ+ cells, about two‐thirds remained λ+, only 1 to 2% became xfr;+, while the other third became sIg−. Again, between 1 and 3% expressed both xfr; and λ L chains. These results indicate that expression of sIgM in the B cell membrane does not terminate L chain gene rearrangement, and that some order exists in xfr; versus λ gene rearrangements. Hence, human and mouse xfr;+ immature B cells can become λ+, but very few of the λ+ cells can become xfr;+, and both can become sIg−. Further, human CD10+/sIg+ xfr;+ and λ+ cells and mouse B220low/sIglow xfr;+ cells enriched from bone marrow, i.e. immature B cells differentiated in vivo, changed their Ig phenotype upon in vitro culture, but in lower frequencies. By contrast, human and mouse mature B cells did not change their L chain or Ig phenotype. Hence, at least a part of the sIg+ immature B cells in bone marrow retain the capacity to change their L chain and Ig phenotype, and this capacity is lost when they become mature, peripheral B cells.
Efficient immune responses in mice lacking N‐region diversity
Authors: Gilfillan Susan , Bachmann Martin , Trembleau Sylvie , Adorini Luciano , Kalinke Ulrich , Zinkernagel Rolf , Benoist Christophe , Mathis Diane 
Published: March 2007

AbstractMice with a null mutation in the terminal deoxynucleotidyl transferase (TdT) gene harbor immunoglobulin and T cell receptor repertoires essentially devoid of N‐region diversity. Consequently, the CDR3 loops important for antigen recognition are shorter and considerably less diverse than those of wild‐type controls. We find surprisingly normal immune responses in TdT° mice, as regards both efficiency and specificity. This provokes a reconsideration of the assumption that N‐region diversity is required for an effective T and B cell repertoire.
Engagement of CD20 suppresses apoptosis in germinal center B cells
Authors: Holder Michelle , Grafton Gillian , Macdonald Ian , Finney Michael , Gordon John 
Published: March 2007

AbstractIn a screen of 67 monoclonal antibodies (mAb) included in the Blind Panel of B cell antibodies for the 5th International Workshop on Human Leukocyte Differentiation Antigens, only the CD20 mAb – included as a positive control for immunophenotyping studies – was found to suppress the spontaneous apoptosis which occurs in human germinal center (GC) B cells when placed in tissue culture at 37°C. Further detailed study using the 1F5 mAb confirmed this observation, showing that rescue from apoptosis via CD20, while not as efficient as that obtained on ligating CD40, was of similar magnitude to that achieved on engagement of surface immunoglobulin (sIg) by immobilized antibody. Also similar to anti‐Ig, the CD20 mAb rescued from apoptosis without priming for the proliferation of GC B cells: this was quite different to its action on resting, non‐GC B cells, where it provides a potent priming signal for cell cycle progression in response to IL‐4 or anti‐CD40. Unlike the survival signal engendered via sIg, CD20 engagement neither mobilized Ca2+ from intracellular stores or opening of a Ca2+ channel with 1F5, nor did it affect the ability of anti‐Ig to open a Ca2+ gate in GC B cells. An unexpected feature of CD20‐mediated rescue of GC B cells from apoptosis was a failure to turn on Bcl‐2 expression.
Are murine marginal‐zone macrophages the splenic white pulp analog of high endothelial venules?
Authors: Lyons A. Bruce , Parish Christopher R. 
Published: March 2007

AbstractThe entry of lymphocytes into the spleen, in contrast to lymph nodes, does not involve high endothelial venule (HEV) interaction. The precise point of entry, as well as the mechanism by which lymphocytes enter the lymphoid areas of the spleen, remains controversial. We examined in detail the effect of two agents, pertussis toxin (PT) and the sulfated polysaccharide fucoidan, on splenic lymphocyte entry and positioning. These have previously been shown to interfere with lymphocyte extravasation across HEV. PT prevents lymphocyte extravasation, but not binding, to HEV, whereas fucoidan prevents binding and thus subsequent extravasation. Studies presented here show that pretreatment of murine lymphocytes with PT does not numerically affect entry into spleen, but profoundly alters lymphocyte positioning within the spleen. When fluorescently labeled, PT‐treated lymphocytes are injected intravenously, they initially accumulate in the marginal zone, in apparent association with the layer of marginal zone macrophages (MZMϕ) which form a shell around the white pulp. They fail to traverse this layer into the white pulp, and subsequently localize in the red pulp. In contrast, untreated cells initially appear in the marginal zone, then continue to migrate into the white pulp after traversing the MZMϕ layer. The localization of PT‐pretreated lymphocytes adjacent to the MZMϕ layer is disrupted by intravenous administration of fucoidan. Using a flow cytometric assay of aggregation between MZMϕ and lymphocytes, we confirmed that fucoidan is also able to inhibit this association in vitro, whereas PT has no effect on this interaction. We propose that MZMϕ in the mouse are the splenic analog of HEV, forming the port of entry of lymphocytes into the white pulp of the spleen.
Cross‐recognition by T cells of an epitope shared by two unrelated mycobacterial antigens
Authors: Harris David P. , Vordermeier Hans‐Martin , Singh Mahavir , Moreno Carlos , Jurcevic Stipo , Ivanyi Juraj 
Published: March 2007

AbstractThe molecular mimicry represented by cross‐recognition of determinants shared by unrelated antigens by antibodies or T cells is of broad immunological interest. In this study, we analyzed the cross‐recognition by CD4+ T cells of a peptide epitope shared by two mycobacterial proteins of diverse sequence, represented by the 19‐kDa antigen of Mycobacterium tuberculosis and the 28‐kDa antigen of Mycobacterium leprae. This epitope was immunodominant with respect to the 19‐kDa antigen, but cryptic in relation to the 28‐kDa antigen. The cross‐reactive epitope cores were identified by Pepscan window analysis and found to be eight residues long in both antigens (residues 69–76 and 127–134). Alignment of these octameric sequences revealed two identical and five conservatively related amino acids. Within the epitope core, two residues (73Asn and 76Ile) were identified as critical for recognition on the basis of inhibition of the cross‐reactive T cell proliferative response using singly substituted analog peptides. These results suggest that T cell cross‐reactive epitopes can exist in proteins with apparently not more than random levels of sequence homology. Their potential for unsuspected cross‐sensitization may play a role in the maintenance of T cell memory, in the pathogenesis of autoimmune diseases and possibly in a wide range of host immune responses to infectious pathogens.
Bacterial superantigens induce T cell unresponsiveness in B cell‐deficient mice
Authors: Miethke Thomas , Wahl Claudia , Heeg Klaus , Wagner Hermann 
Published: March 2007

AbstractBacterial superantigens such as staphylococcal enterotoxin B (SEB) cause in vivo a profound and long‐lasting state of unresponsiveness in ligand‐reactive T cells. To test whether presentation of SEB by small resting B cells to ligand‐reactive T cells is essential for the induction of T cell unresponsiveness, we analyzed the effect of SEB in B cell‐deficient mice. We observed T cell deletion and T cell unresponsiveness in both B cell‐deficient mice and control mice. We conclude that presentation of SEB by resting B cells is not a prerequisite for the induction of T cell unresponsiveness in vivo.
Lack of inducible nitric oxide synthase activity in T cell clones and T lymphocytes from naive and Leishmania major‐infected mice
Authors: Thüring Heike , Stenger Steffen , Gmehling Daniela , Röllinghoff Martin , Bogdan Christian 
Published: March 2007

AbstractNitric oxide (NO) generated by the inducible isoform of nitric oxide synthase (iNOS) is implicated in a number of immunological processes including killing of intracellular parasites, suppression of T cell proliferation, production of cytokines and destruction of tissue in autoimmune diseases. Considering that cytokine‐activated mouse macrophages, fibroblasts and endothelial cells are potent producers of NO, we investigated whether T cells, as central participants in immune responses, can also be activated for the release of NO. Neither thymocytes nor type 1 or type 2 T helper cell clones generated significant amounts of nitrite (the stable end product of NO in culture supernatants) when stimulated by T cell mitogens, cytokines or antigen in the presence of irradiated antigen‐presenting cells. Similarly, T cells freshly isolated from mice acutely infected with the intracellular pathogen Leishmania major did not produce NO upon restimulation in vitro. The lack of NO production was not due to the expression of enzymatically inactive iNOS, as we were unable to detect any iNOS protein in activated T helper clones or in freshly isolated T cells from infected mice by Western (protein) blot analysis. Finally, we tested whether iNOS expression in T cells might be restricted to a minor subpopulation and therefore only detectable on a single cell level. After immunofluorescence staining of lymph node or spleen cells from infected mice with antibodies against iNOS, F4/80‐ or Thy‐1‐antigen, macrophages, but no T cells, were found to express iNOS. Thus, we have no evidence that activated T helper cell clones or T cells from L. major‐infected mice are high producers of NO.
Processing and presentation of type II collagen, a fibrillar autoantigen, by H‐2q antigen‐presenting cells
Authors: Manoury‐Schwartz Bénédicte , Chiocchia Gilles , Fournier Catherine 
Published: March 2007

AbstractNative type II collagen (CII) is a high molecular‐weight fibrillar molecule which induces a chronic polyarthritis in mice expressing the H‐2q haplotype. The present study was initiated to analyze the processing and the presentation of this nonglobular protein by H‐2q antigen‐presenting cells (APC). Efficiency of presentation was assessed by the ability of antigen‐pulsed APC to activate collagenspecific CD4+ T cell hybridomas. Fixation of APC or the presence of chloroquine completely blocked the reactivity of the T cell hybrids to native, denatured and cyanogen bromide (CB) degraded CII, thus indicating the requirement of intracellular processing for adequate presentation of CII peptides to T cells. In the presence of various processing inhibitors (brefeldin A, leupeptin and Ntosyl‐L‐phenylalanine chloromethylketone) stimulation of T hybrids by CIIpulsed APC was reduced, pointing to the need of newly synthesized class II molecules, the use of several intracellular compartments and the implication of different proteases in the generation of CII peptides. Peritoneal macrophages and, to a lesser extent, total spleen cells, presented native and denatured CII with higher efficiency than purified splenic dendritic cells, naive or even immune B cells from CII‐primed mice. In contrast, these dendritic and B cells were fully competent to present intact ovalbumin to a specific T cell hybrid. The stimulation by dendritic cells and immune B cells was greater when CB peptides of CII were added instead of the native molecule. Similarly, the cleavage of CII was an absolute requirement for its presentation by epidermal cells and B cell lymphomas to the T cell hybridomas. Taken together, these findings emphasize the crucial role of intracellular processing for recognition of soluble CII, similar to most antigens. However, in contrast to ovalbumin, the size and fibrillar nature of the native CII molecule influences its capture by the APC, thus limiting the type of APC able to present this antigen.
In susceptible mice, Leishmania major induce very rapid interleukin‐4 production by CD4+ T cells which are NK1.1−
Authors: Launois Pascal , Ohteki Toshiaki , Swihart Kristin , MacDonald H. Robson , Louis Jacques A. 
Published: March 2007

AbstractSusceptibility of BALB/c mice to infection with Leishmania major is associated with a T helper type 2 (Th2) response. Since interleukin‐4 (IL‐4) is critically required early for Th2 cell development, the kinetics of IL‐4 mRNA expression was compared in susceptible and resistant mice during the first days of infection. In contrast to resistant mice, susceptible mice exhibited a peak of IL‐4 mRNA in their spleens 90 min after i.v. injection of parasites and in lymph nodes 16 h after s.c. injection. IL‐12 and interferon‐γ (IFN‐γ) down‐regulated this early peak of IL‐4 mRNA; the effect of IL‐12 was IFN‐γ dependent. Treatment of resistant C57BL/6 mice with anti‐IFN‐γ allowed the expression of this early IL‐4 response to L. major. The increased IL‐4 mRNA expression occurred in Vβ8, 7, 2− CD4+ cells in BALB/c mice and NK1.1− CD4+ cells in anti‐IFN‐γ treated C57BL/6 mice. These results show that the NK1.1+ CD4+ cells, responsible for the rapid burst of IL‐4 production after i.v. injection of anti‐CD3, do not contribute to the early IL‐4 response to L. major.
Characterization of processing requirements and metal cross‐reactivities in T cell clones from patients with allergic contact dermatitis to nickel
Authors: Moulon Corinne , Vollmer Jörg , Weltzien Hans‐Ulrich 
Published: March 2007

AbstractMetal ions such as nickel, cobalt, copper and palladium are known to be potent sensitizers in humans, but the antigenic determinants created by these metals as well as the mechanisms of recognition by specific T cell clones are still not elucidated. In this paper, nickel‐specific T lymphocyte clones were isolated from four patients exhibiting contact dermatitis to this metal. A panel of 42 independent T cell clones was studied. They were shown to recognize nickel in the context of major histocompatibility complex (MHC) class II molecules and to belong to the CD4 subset. Using fixed autologous Epstein‐Barr virus‐transformed B cells as antigen‐presenting cells (APC), we could distinguish two distinct groups of T cell clones on the basis of processing requirements: 40% of the T cell clones were strictly processing dependent, whereas the remaining 60% could proliferate in response to nickel even in the presence of glutaraldehyde‐fixed APC. Furthermore, we present arguments indicating that individual Ni‐specific T cell clones cross‐react with some transition metals (e.g. Cu or Pd), but not with others (e.g. Co, Cr and Pt), presented by identical MHC class II molecules. These results thus provide an explanation for the multiple metal‐reactivities observed in vivo in human patients: they indicate that for Cu and Pd, these co‐reactivities in vivo might be due to cross‐reactivity at the clonal level. Our findings also suggest that this is not the case for cobalt allergy, which might result from co‐sensitization of the patient to cobalt in addition to nickel.
Identification of an ionomycin/cyclosporin A‐responsive element within the human T cell receptor gamma enhancer
Authors: Hettmann Thore , Cohen Amos 
Published: March 2007

AbstractActivation through the Ca2+/calcineurin pathway is essential to the transcription of many cytokine genes. The conserved cis‐acting sequence, GGAAAA, and transcription factors binding to this sequence are involved in the response to increased intracellular Ca2+ concentrations. Here we report the identification and importance of the same sequence in a non‐cytokine gene, the human T cell receptor gamma (TCRG) enhancer. Results from site‐directed mutations and electrophoretic mobility shift assays strongly suggest that this sequence mediates the ionomycin‐induced activation of the TCRG enhancer. Our studies provide an explanation for a previous observation that TCRG mRNA levels, but not mRNA levels for T cell receptor alpha and ‐beta, are increased by ionomycin treatment.