摘要:

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 modifiedin vitrowith 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 immu

ISSN:0014-2980    

DOI:10.1002/eji.1830270602

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractImmunoglobulin χ promoters show sequence divergence but conserved function between different subgroups. Here we show that three separate 5′ elements are required for synergistic stimulation of transcription with the decamer in a χ promoter. These sites are a 5′ E‐box, a 3′ AT‐rich region in the pentadecamer (pd) element, and the χ‐Y element. Elf‐1 is a novel χ‐Y element ligand induced upon mitogenic stimulation of resting B lymphocytes. Furthermore, the 5′ E2A‐like E‐box in the pd element could be substituted by an upstream stimulatory factor motif with conservation of function. Thus, the synergistic activation requirements of χ transcription is strictly dependent on the quantitative presence of transcription factor‐binding motifs 5′ of the decamer, but these differ qualitatively in that they may bind an array of pr

ISSN:0014-2980    

DOI:10.1002/eji.1830270603

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractIt has been suggested that loss of uninfected T cells in HIV infection occurs because of lymphocyte activation resulting in cell death by apoptosis. To address the question of whether cross‐linking of CD4/HIV gp120 complexes by antibodies were sufficient to induce T cell depletionin vivo, we developed an animal model of continuous interaction between human CD4 (hCD4), gp120 and anti‐gp120 antibodies in the absence of other viral factors. Double‐transgenic mice have been generated in which T cells express on their membrane hCD4 and secrete HIV gp120. Although these mice have hCD4/gp120 complexes present on the surface of T cells, they do not show gross immunological abnormalities, and they are able to produce anti‐gp120 antibodies following immunization with denaturated gp120. However, double‐transgenic mice with antibodies to gp120, when immunized with tetanus toxoid, mount an IgG response that is significantly lower than that of double‐transgenic mice without antibodies to gp120. Furthermore, the presence of anti‐gp120 antibodies leads to CD4+T cell depletion and immunodeficiency in the absence of HIV infection. Thus, the antibody response to gp120 can lead to CD4+T cell att

ISSN:0014-2980    

DOI:10.1002/eji.1830270604

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractIn mouse Peyer's patches (PP), dendritic cells (DC) are localized in T cell areas as NLDC145+CD11c+ cells, and in the dome and corona region of the follicle as NLDC145− CD11c+ cells, respectively, suggesting the presence of two different DC populations with distinct roles in antigen uptake, processing, and presentation. However, it is not clear how this relates to DC maturation. In this report, we demonstrate that freshly‐isolated CD11c+ DC have the properties of immature DC since they endocytose soluble antigens, phagocytose particulate material such as latex beads, synthetize major histocompatibility complex (MHC) class II and invariant chain, but, at the same time, display low stimulatory activity for resting T cells, as shown in mixed‐lymphocyte reaction and oxidative mitogenesis assays. When cultured for 24 h in the presence of the cytokines granulocyte‐macrophage colony‐stimulating factor and tumor necrosis factor or anti‐CD40, the cells undergo dramatic phenotypic and functional changes characteristic of DC maturation. After 24 h stimulationin vitro, CD11c+ cells lose the ability to take up proteins such as ovalbumin, and in parallel with this decline, the biosynthesis of MHC class II and invariant chain is dramatically down‐regulated or eliminated. On the other hand cells treatedin vitroexhibit on the cell surface higher levels of MHC class II, of co‐stimulatory molecules (CD80, CD86), of adhesion molecules (CD44, intercellular adhesion molecule‐1), and acquire expression of the interdigitating DC surface marker NLDC145. Concomitantly, the ability to stimulate naive T cells drastically increased afterin vitrotreatment with both stimuli. Taken together, our results indicate that the majority of DC in the PP are immature in terms of their antigen‐uptake capacity. These sentinel antigen presenting cells are strategically positioned at the dome region of PP, where antigens are transcytosed via the M cells from the gut lumen. A second population of mature interdigitating NLDC145+CD11c+ DC stimulates naive unprimed T cells in interfollicular areas by up‐regulation of surface ligands

ISSN:0014-2980    

DOI:10.1002/eji.1830270605

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractHuman major histocompatibility complex class I allele HLA‐B27 is associated with a group of diseases called spondyloarthropathies. In reactive arthritis (ReA), the disease is triggered by certain infections,e.g.gastroenteritis caused bySalmonella.The host/microbe interaction is abnormal in susceptible individuals leading to inefficient elimination of arthritis‐triggering bacteria, fragments of them, or both, after the initial infection. Using transfected human monocytic U937 cell lines, we demonstrate that the expression of the HLA‐B27 antigen does not influence the uptake ofS. enteritidisinto U937 cellsin vitro.Interestingly, HLA‐B27 remarkably impairs the elimination ofS. enteritidiswithin the HLA‐B27 transfected U937 cells. The impaired elimination of ReA‐triggering microbes by HLA‐B27+monocytes may offer an explanation for the persistence of ReA‐triggering microbes in susceptible HLA‐B27+individuals. This modulation of the host/microbe interaction by HLA‐B27 may have an important role in the

ISSN:0014-2980    

DOI:10.1002/eji.1830270606

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractIt has been shown recently that mast cells play an essential role as a source of tumor necrosis factor‐α production during neutrophil recruitment to sites of bacterial infection. Increased numbers of mast cells are indeed noted at sites of wound healing and inflammation. These cells are either recruited from the bone marrow or proliferate locally under cytokine stimulation. Little is known about how mast cell progenitors extravasate into tissue. Using antibody‐like fusion proteins of mouse E‐selectin and P‐selectin, we have analyzed the ability of immature mouse bone marrow‐derived mast cells (BMMC) to interact with the endothelial selectins. The P‐selectin glycoprotein ligand‐1 (PSGL‐1) was affinity‐isolated from detergent extracts of surface biotinylated BMMC with both selectin‐IgG fusion proteins. However, only P‐selectin‐IgG, but not E‐selectin‐IgG showed significant interaction with intact BMMC as tested by flow cytometry and cell attachment assays with the immobilized fusion proteins under flow and non‐flow conditions at physiological shear stress. Thus, in spite of carrying the necessary carbohydrate modifications which enable solubilized PSGL‐1 to bind avidly to E‐selectin, PSGL‐1 on the surface of BMMC is presented in a way that prevents it from interacting efficiently with E‐selectin. Affinity‐purified rabbit antibodies against mouse PSGL‐1 almost completely blocked the interaction of BMMC with P‐selectin‐IgG in flow cytometry as well as in cell adhesion assays under static and under flow conditions. Our data reveal that PSGL‐1 is the major binding site for P‐selectin on mouse BMMC progenitors, but does

ISSN:0014-2980    

DOI:10.1002/eji.1830270607

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractTo determine the major histocompatibility complex (MHC) restriction of the T/B cell interaction involved in a negative regulation of Ig production, we used mouse model of T cell‐induced IgG2absuppressionin vivo.Normal or specifically triggered T splenocytes from mice of the Ighahaplotype, when neonatally transferred into histocompatible Igha/bheterozygotes, are able to induce a specific and total suppression of the IgG2aballotype. Nevertheless, only transfer of IgG2ab‐primed IghaT splenocytes induces this suppression in Ighb/bhomozygous congenic mice in which the whole IgG2a isotype production is inhibited. This suppression is chronically maintained by CD8+T cells, but can be experimentally reversed. We have established that the suppression induction required a CD4+CD8+T cell cooperation and operated via the recognition by the involved TCR of Cγ2ab‐derived peptides presented by the target B cells in an MHC haplotype‐restricted manner. Here, by using Ighbmice genetically deficient for MHC class I (β2‐microglobulin%, or β2m%) or class II (I‐Aβ%) molecules, we demonstrate functionally that the suppression induction implicates an MHC class I‐, but not class II‐restricted interaction. Indeed, the anti‐IgG2abT cells transferred into IghbH‐2bI‐Aβ%mice carry out the suppression process normally, while in IghbH‐2bβ2m%recipients, their suppression induction capacity is significantly inhibited. Moreover, the Cγ2ab103–118 peptide, identified as the sole Cγ2ab‐derived peptide able to amplify the anti‐IgG2abT cell reactivity in IghaH‐2bmice, is also able to stabilize the H‐2Db, but not the H‐2Kbclass I molecules at the surface of RMA‐S (TAP2−, H‐2b) cells. These results indicate that, despite the CD4+/CD8+T cell cooperation during the induction phase of suppression only MHC class I molecule expression is required at the surfac

ISSN:0014-2980    

DOI:10.1002/eji.1830270608

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractImmunization of mice with mixtures of listeriolysin, a pore‐forming hemolysin secreted by the pathogenic bacteriumListeria monocytogenes, together with soluble ovalbumin, nucleoprotein of influenza virus, or β‐galactosidase ofEscherichia coli, resulted in strong cytotoxic CD8 T cell responses to each of the respective passenger proteinsin 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 formul

ISSN:0014-2980    

DOI:10.1002/eji.1830270609

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

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 mu

ISSN:0014-2980    

DOI:10.1002/eji.1830270610

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractHuman CD1 form a group of nonpolymorphic leukocyte surface molecules with homology to major histocompatibility complex (MHC) proteins. Recent findings in human and in mouse demonstrate the capacity of CD1 molecules to present nonpeptide components like lipids or lipoglycans as well as peptides. We studied the involvement of β2‐microglobulin (β2m) in expression of the classic human CD1 proteins CD1a, CD1b, and CD1c. The β2m‐deficient human melanoma cell line FO‐1 was transiently transfected with either CD1a, CD1b, or CD1c DNA alone, or in combination with β2m using the adenovirus‐enhanced receptor‐mediated transfer infection system. Only co‐transfection of FO‐1 cells with CD1 + β2m resulted in the detection of CD1 Ag by monoclonal antibodies (mAb). This indicated that CD1 mAb recognized determinants are dependent on β2m and raised the question whether β2m‐free forms of CD1 can be expressed. Therefore, to visualize CD1 molecule expression independently of β2m, we expressed tagged recombinant forms. A full‐length CD1b construct tagged at the very C terminus with a small peptide was transported to the plasma membrane only when β2m was co‐transfected. β2m involvement in the transport of CD1 was confirmed by expression of soluble forms of CD1a, CD1b, and CD1c in three different cell types. Analogous to tagged full‐length CD1b, secretion of the soluble CD1 constructs was strictly dependent on β2m. The soluble CD1 chimeras were secreted as complexes with endogenous β2m. Thus, similar to its role for MHC class I expression, β2m is essential for processing and surface transport of the classic human

ISSN:0014-2980    

DOI:10.1002/eji.1830270611

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY