摘要:

AbstractGerminal centers (GC) constitute a specialized microenvironment essential for the formation of memory B cells, B cell affinity maturation and isotype switching. Within the GC, the B cells closely interact with follicular dendritic cells (FDC) and T cells, which both provide stimuli to the B cells that prevent their entry into apoptosis and promote their differentiation into memory cells or plasma cells. Cross‐linking of B cell immunoglobulin (Ig) receptors by antigen, stimulation of the integrin adhesion molecules LFA‐1 and VLA‐4 on the B cell through interaction with their counter receptors ICAM‐1 and VCAM‐1 on the FDC and cross‐linking of CD40 on the B cells through interaction with the CD40 ligand (CD40L) on T cells have been shown to prevent entry into apoptosis of GC B cells. Triggering of CD95, on the other hand, has been shown to induce apoptosis. We therefore investigated the interaction between adhesion‐mediated signals, Ig, CD40, and CD95. The spontaneous apoptosis of GC B cells was not further increased by adding anti‐CD95. However. CD95 stimulation did result in apoptosis of GC B cells in the presence of anti‐Ig or adhesion‐mediated rescue signals, which indicates that CD95 expressed on GC B cells is functionally active. In contrast, anti‐CD95 was unable to induce apoptosis in cells rescued via CD40 stimulation, suggesting an important role for CD40L expressed on GC T cells in apoptosis regulation. We also studied apoptosis of B cells adhering to FDC, and found that B cells that interact with FDC were also rescued from CD95‐induced apoptosis. A human CD40.Fcu fusion protein that blocks CD40 ligation failed to inhibit this effect. Our studies therefore indicate that neither CD40, Ig receptors, nor adhesion receptors mediate rescu

ISSN:0014-2980    

DOI:10.1002/eji.1830270102

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe state of integrin activation can be assessed by monoclonal antibodies (mAb) that selectively recognize integrins in their active form. We demonstrate herein that the expression of the epitope recognized by mAb HUTS‐21 is induced on T lymphoblasts upon binding of soluble vascular cell adhesion molecule (VCAM)‐1 and an 80‐kDa tryptic fragment of fibronectin (FN80) to the β1 integrins very late activation antigen (VLA)‐4 and VLA‐5, and that this effect is dependent on ligand concentration and is specific for β1 integrins. On T lymphoblasts adhering to immobilized fibronectin, the HUTS‐21 epitope localized exclusively to sites of integrin binding to fibronectin. These results indicate that mAb HUTS‐21 recognizes a ligand‐induced binding site (LIBS) on the common β1 subunit of VLA proteins. Engagement of β1 integrins through this LIBS epitope inhibited T lym‐phoblast movement on fibronectin, as determined by quantitative time‐lapse video microscopy studies. Furthermore, the HUTS‐21 mAb also prevented T lymphoblast‐directed migration through gradients of substratum‐immobilized β1 integrin ligands such as fibronectin or VCAM‐1, whereas it did not affect migration on intercellular adhesion molecule (ICAM)‐1. This anti‐LIBS mAb stimulated cell adhesion through postreceptor events, without affecting receptor affinity for ligand, and appears to interfere with cell migration by a mechanism distinct from that of

ISSN:0014-2980    

DOI:10.1002/eji.1830270103

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractAn inflammatory bowel disease (IBD) comparable to human ulcerative colitis is induced upon transfer of T cell‐depleted wild‐type (F1) bone marrow into syngeneic T cell‐deficient (tgε26) mice (F1 → tgε26). Previously we have shown that activated CD4+T cells predominate in transplanted tgε26 mice, and adoptive transfer experiments verified the potential of these cells to cause disease in immunodeficient recipient mice. Using flow cytometry for the detection of intracellular cytokine expression, we demonstrate in the present study that large numbers of CD4+and CD8+TCRαβ+T cells from the intraepithelial region and lamina propria of the colon of diseased, but not from disease‐free mice, produced interferon‐γ (IFN‐γ) and tumor necrosis factor‐α (TNF‐α). Large numbers of T cells from peripheral lymphoid tissues of these animals also expressed IFN‐α and TNF‐α, but few expressed interleukin‐4, demonstrating g strong bias towards Th1‐type T cell responses in these animals. TCRγδ+T cells, typically minor constituents of the inflammatory infiltrate of the colon in F1 → tgε26 mice, also expressed IFN‐γ at a high frequency upon CD3 stimulation. In light of these findings we examined the potential involvement of TCRγδ+T cells by testing their ability to induce colitis in tgε26 mice. We report here that tgε26 mice transplanted with T cell‐depleted bone marrow from TCRαnulland TCRβnullanimals developed IBD. Furthermore, disease in these mice correlated with the development of peripheral and colonic TCRαδ+T cells capable of IFN‐γ production. These results suggest that IFN‐γ may be a common mediator

ISSN:0014-2980    

DOI:10.1002/eji.1830270104

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractHuman CD1+CD14‐dendritic cells (DC) can be derived from CD14+monocytes using granulocyte/monocyte colony‐stimulating factor and interleukin (IL)‐4. We have previously shown that IL‐10 pre‐treatment of such DC significantly inhibited their antigen‐presenting capacity to CD4+T cell clones. In this study, we further analyze how IL‐10 influences antigen presentation. We first investigated whether IL‐10 could alter the early stage of antigen presentation, the capture of antigen. This can be mediated by mannose receptor (MR)‐mediated endocytosis and by fluid‐phase uptake through macropinocytosis. IL‐10‐treated DC showed an enhancement of both mechanisms of antigen capture, as indicated by the increase of fluorescein isothiocyanate‐dextran uptake through MR and lucifer yellow uptake. However, IL‐10‐treated DC, irradiated or glutaraldehyde‐fixed, were less efficient than untreated DC in stimulating mixed leukocyte reaction as well as in inducing the activation of peptide‐specific T cell clones, indicating that IL‐10 achieves its effects mainly by modifying the cell surface phenotype of DC. HLA class I and II, as well as intercellular adhesion molecule (ICAM)‐1, lymphocyte function‐associated antigen‐3, B7‐1, B7‐2 and ICAM‐3 expression were either significantly increased or essentially unchanged, and the ability to bind the epitope recognized by the T cell clones was also unaffected regardless of IL‐10 treatment. Our study also indicates that as‐yet unidentified accessory molecules may play an essential role in T cell activation. Thus, the IL‐10‐treated DC possess an increased capacity to capture antigen, with a concomitant decreased stimulatory activity. Our study suggests that IL‐10‐treated DC have the characteristics of highly immature DC (high capture ability, low stimulatory potency) and may represe

ISSN:0014-2980    

DOI:10.1002/eji.1830270105

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractBinding of T lymphocytes within the different compartments of the secondary lymphoid organs is crucial for the function of the cellular and the humoral immune response. It is still not known which adhesion molecules guide T cells to the distinct areas of the lymphoid microenvironment. In the current study anin situadhesion assay was used to define the receptors for binding of T cells to human tonsils. The T cell lines Jurkat and MOLT‐4 and normal, activated T cells were found to bind exclusively to germinal centers. Jurkat cells used the receptor pair integrin‐α4 (VLA‐4α)/VCAM‐1, whereas activated MOLT‐4 cells and normal T cells bound via both adhesion pathways, namely via integrin‐α4/VCAM‐1 and LFA‐1/ICAM‐1 and ‐2. It is suggested that these adhesion mechanisms are involved in the migration of T cells into the germinal centers of secondary lymphoid organs and that they influence the selection o

ISSN:0014-2980    

DOI:10.1002/eji.1830270106

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractTo ascertain whether the development of dendritic cells (DC) in mouse lymphoid organs is dependent on granulocyte/macrophage colony‐stimulating factor (GM‐CSF), we determined the number of DC in the thymus, spleen and lymph nodes of normal mice, of mice with the genes coding for GM‐CSF or its receptor inactivated, and of transgenic mice with excessive levels of GM‐CSF. DC were extracted from the tissues and enriched prior to flow cytometric analysis. The total DC level and the incidence of DC expressing lymphoid‐related markers (CD8hiCD11blo) and myeloid‐related markers (CD8loCD11bhi) were monitored. Both in GM‐CSF null mice, and GM‐CSF receptor null mice, DC of all surface phenotypes were present in all lymphoid organs; only small decreases in DC levels were recorded, except for the lymph nodes of GM‐CSF receptor null mice which showed a more pronounced (threefold) decrease in DC numbers. Since the GM‐CSF receptor null mice lacked the β chain common to the GM‐CSF, interleukin (IL)‐3 and IL‐5 receptors, the development of DC in the absence of GM‐CSF was not due to common β chain mediated developmental signals elicited by IL‐3 or IL‐5. In GM‐CSF transgenic mice, there was only a 50 % increase in DC numbers in thymus and spleen, paralleling an increase in overall cellularity, but a more pronounced (threefold) increase in DC numbers in lymph nodes. There was no evidence that GM‐CSF had a selective effect on any particular DC subpopulation defined by CD8 or CD11b expression. We conclude that the development of most lymphoid tissue DC can proceed in the absence of GM‐CSF, although this cytokine can produce some elevation of DC levels. It is not clear whether the enhancing effect of GM‐CSF is direct or an in

ISSN:0014-2980    

DOI:10.1002/eji.1830270107

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractHuman placental trophoblast cells that constitute the materno‐fetal interface during pregnancy escape maternal alloimmune attack. The different trophoblast cell subpopulations have developed efficient regulatory mechanisms to prevent expression of β2‐microglobulin‐associated HLA class Ia molecules at their cell surface. We previously reported the presence of HLA class Ia messages in villous cytotrophoblast cells and in the syncytiotrophoblast differentiatedin vitropurified from term placenta. In this study, we found that these transcripts are translated in heavy chain proteins that are endoglycosidase H sensitive and thus retained in the endoplasmic reticulum orcis‐Golgi. Moreover, these class Ia heavy chains can be co‐immunoprecipitated with the chaperone protein calnexin resident in the endoplasmic reticulum. When these trophoblast cells are treated with interferon (IFN)‐γ, part of the class Ia heavy chains become endoglycosidase H resistant, demonstrating that they have left the endoplasmic reticulum. Furthermore, after such a treatment, these heavy chains are detectable at the cell surface of these trophoblast cells, as assessed by two‐color flow cytometry analysis and immunoprecipitation of cell surface biotinylated proteins using the W6/32 anti‐HLA class I monoclonal antibody (mAb). IFN‐γ treatment induces a significant enhancement of the transcription of transporters associated with antigen processing (TAP1 and TAP2) rather than an increase of HLA class I or β2‐microglobulin messages. Finally, we demonstrate that an anti‐TAP1 mAb coimmunoprecipitates TAP1 proteins and HLA class Ia heavy chains in these IFN‐γ‐treated trophoblast cells. Thus, the constitutive absence of HLA class Ia cell surface expression in term villous cytotrophoblast and syncytiotrophoblast is likely to be due to a lack of transporter proteins that participate in the proper assembly of these molecules in the endoplasmic reticulum. Such a defect can be

ISSN:0014-2980    

DOI:10.1002/eji.1830270108

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe contribution of co‐receptors in signal transduction upon T cell receptor (TCR)‐mediated recognition of major histocompatibility complex (MHC) class II antigen by mature T lymphocytes expressing TCR derived from the apparently co‐receptor‐independent, I‐Ak‐specific allogeneic CD8+CTL clone QM11 has been examined. Mature double‐negative, CD8+and CD4+bulk T cell lines and clones expressing TCRQM11were developed from TCRQM11transgenic mice. All these T cells, irrespective of co‐receptor expression, showed specific lytic activity on cells expressing I‐Ak. Furthermore, co‐receptorless mutants were obtained from a CD4+and CD8+clone. The responses of these co‐receptorless mutants upon specific recognition of the alloantigen, as judged by cytolytic activity, granule exocytosis, lymphokine production, proliferation, and tyrosine phos‐phorylation of the ξ chain, were comparable to those of the original clones. Thus, the results proved the co‐receptor independence of the recognition of I‐Akby TCRQM11and further indicated there is no indispensable unique signal transduced by co‐receptors. However, when the amount of the available antigen was limited by anti‐I‐Akantibody, the CD4+T cell clone showed a remarkable resistance to the inhibition whereas the mismatched CD8+clone was readily inhibitable. The anti‐I‐Ak‐resistant component of the CD4+clone showed dependency on the CD4 molecule. Taken collectively, the results indicate that the role played by a co‐receptor molecule in mature T cells is purely quantitative amplification of the signal through the formation of a TCR/MHC/co‐receptor ternary complex, and also indicate that the role of co‐receptor molecules as TCR‐i

ISSN:0014-2980    

DOI:10.1002/eji.1830270109

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe consequence of recognition of antigen on antigen‐presenting cells that are induced to express major histocompatibility complex (MHC) class II molecules following an inflammatory process is still not clear. In this study, we have investigated the outcome of antigen presentation by epithelial cells and we have used as a model thyroid follicular cells (TFC) that are known to express MHC class II molecules in autoimmune thyroid diseases and acquire the capacity to present autoantigens to T cells infiltrating the thyroid gland. The result show that MHC class II‐expressing TFC were unable to stimulate a primary T cell alloresponse, using CD4+T cells from three HLA‐mismatched responders. Phenotypic analysis showed that TFC, after incubation with interferon‐γ, do not express the co‐stimulatory molecules B7‐1 (CD80) and ‐2 (CD86). Addition of murine DAP.3 cells expressing human B7‐1 (DAP.3‐B7) to cultures containing peripheral blood CD4+T cells and DR1‐expressing TFC led to a proliferative response, suggesting that the failure of TFC to stimulate a primary alloresponse was due to a lack of co‐stimulation. Similarly, HLA‐DR‐restricted, influenza‐specific T cell clones dependent on B7 for co‐stimulation did not respond to peptide presented by TFC; again the lack of response could be overcome by co‐culture of TFC with DAP.3‐B7. Furthermore, recognition of antigen on TFC inhibited interleukin‐2 (IL‐2) production in the B7‐dependent T cells. In contrast, in T helper type 0 (Th0) T cells, IL‐4 release was not affected by TFC presentation. In addition, antigen presentation by TFC favored IL‐4 production relative to IL‐2 production by B7‐indpendent Th0 clones. These results suggest that antigen presentation by MHC class II+TFC may induce tolerance in autoreactive Th1 cells but may simultaneously favors a Th2 response in uncommitted T ce

ISSN:0014-2980    

DOI:10.1002/eji.1830270110

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractNKR‐P1 is a type II transmembrane protein which acts as an activation receptor on natural killer (NK) cells. The cytoplasmic domains of the CD4, CD8 and 4‐1BB receptors contain the sequence Cys‐X‐Cys‐Pro which is directly involved in coupling to another pair of cysteines in the N‐terminal domain of the src family tyrosine kinase p56lck. The cytoplasmic domain of NKR‐P1 in rodents also contains the Cys‐X‐Cys‐Pro sequence, but the capacity of the receptor to bind p56lckis presently unknown. We tested for direct coupling between these proteins using both protein biochemistry and the yeast two‐hybrid technique. Immunoprecipitation studies showed that p56lckcan be co‐immunoprecipitated with NKR‐P1 from a rat NK tumor cell line. In addition, the cytoplasmic domain of NKR‐P1 interacted with the N‐terminal domain of p56lckin yeast as assessed by reporter gene activation. Integrity of the cysteine pairs in both proteins was critical in mediating the interaction. The experiments suggest that the association of p56lckwith NKR‐P1 is somewhat weaker than the p56lckassociation with CD8α, but of much lower avidity than between CD4 and p56lck. This could reflect a higher activation threshold for the NKR‐P1 and CD8 receptors, which are involved in cytolytic responses, compared to CD4 which is

ISSN:0014-2980    

DOI:10.1002/eji.1830270111

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY