Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0033036 (APC)
 10,214 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glycosylphosphatidylinositol (GPI)-modified variants of murine B7-1 and B7-2 cell surface costimulators were produced via chimerization with alternative GPI-modification signal sequences from decay-accelerating factor (DAF). GPI anchorage was verified by demonstrating phosphatidylinositol-specific phospholipase C (PI-PLC) sensitivity of the chimeric polypeptides in both immunofluorescence/flow-cytometric and immunoprecipitation analyses. The various GPI-modified chimeric B7-1:DAF and B7-2:DAF polypeptides were shown to retain costimulator function, in both an in vitro proliferation assay and an in vivo triggering of cytotoxicity assay. The findings indicate that costimulator function for both B7-1 and B7-2 is not dependent upon native hydrophobic transmembrane anchorage. Moreover, the functionality of the GPI-modified variants in enhancing the immunogenicity of the murine T lymphoma line EL-4 suggests a novel route for generating APC-centered immunotherapeutics, including cellular cancer vaccines, that is based upon protein transfer of GPI-modified costimulators.
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PMID:Glycosylphosphatidylinositol-modified murine B7-1 and B7-2 retain costimulator function. 749 30

The interaction of T cell CD28/CTLA-4 receptors with B7-1 activation Ag on APC represents an important costimulatory pathway in T cell activation. However, it is now evident that this costimulatory pathway is neither unique nor universal for the activation of T cells. Our previous study indicated that a 60-kDa membrane protein, recognized by mAb 2D10, was expressed before B7 by activated murine B cells. This molecule was critically involved in activation of T cells in response to auto- and alloantigens. In the present study, we report on the isolation of a cDNA for this early T cell costimulatory molecule (ETC-1). ETC-1, like B7-1, is a member of the Ig supergene family and is composed of 303 amino acids. Nucleic acid sequence comparison indicated that ETC-1 is identical to the B7-2 molecule. When expressed in Chinese hamster ovary cells, ETC-1 showed profound T cell costimulatory activity as demonstrated by its ability to enhance CD4 T cell proliferation in response to Con A or anti-CD3 stimulation. Furthermore, ETC-1 also bound to both CD28-Ig and CTLA4-Ig fusion proteins. These results strongly support the notion that the interaction of ETC-1/B7-2 with CD28 or CTLA-4 receptors represents an alternative T cell costimulatory pathway.
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PMID:Molecular cloning and expression of early T cell costimulatory molecule-1 and its characterization as B7-2 molecule. 751 26

Granulomatous inflammation in schistosomiasis is a manifestation of cell-mediated hypersensitivity to parasite egg Ags that is predictably reduced in size over the course of the disease. This down-regulation may reflect a state of anergy in the T cells mediating granuloma formation after interaction with accessory cells incapable of providing full stimulation. The present studies were conducted to investigate this mechanism at the molecular level. We found that granuloma macrophages (GM) strongly inhibit the ability of splenic APC to stimulate egg Ag-specific Th1 responses. This property was shown to be dependent on their secretion of IL-10. Moreover, activated GM in culture were found to express little or no costimulatory Ags B7 or B7-2. However, when their autocrine secretion of IL-10 was neutralized with specific mAb, GM displayed an up-regulation of costimulatory molecules as well as of MHC class II Ags. Most importantly, GM cultured in the presence of anti-IL-10 mAb, acquired the ability to stimulate egg Ag-specific T cells. By independently blocking each of the induced costimulatory Ags, it appeared that B7-2 molecules provided stronger costimulation than B7. In separate experiments, culture supernatants from GM exerted a powerful inhibition of costimulatory Ag expression on Con-A-stimulated peritoneal exudate cells in vivo, which could similarly be attributed to IL-10. Our results demonstrate that IL-10 can play a critical role in the generation of accessory cells that, by virtue of down-regulation of costimulatory molecules, may be capable of inducing anergy in T cells mediating the vigorous granulomatous response of acute stage schistosomiasis. Our studies lend support to the contention that a state of unresponsiveness in pathogenic T cells may precipitate the down-regulation of granuloma formation and provide a molecular basis for the underlying mechanisms.
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PMID:Regulation of T helper cell responses in experimental murine schistosomiasis by IL-10. Effect on expression of B7 and B7-2 costimulatory molecules by macrophages. 752 26

Signals initiated through both the TCR complex and CD28 are required for optimal activation of T lymphocytes. Recently, it has been demonstrated that CD28 interacts with two different ligands, designated CD80 (B7/B7-1) and CD86 (B70/B7-2). We have produced stable transfectants that express CD80, CD86, or both ligands and have examined their ability to costimulate T cell proliferation, cytokine production, and the generation of CTL. When we used small, resting human peripheral blood T cells as responders, both CD80 and CD86 transfectants efficiently costimulated anti-CD3 mAb-induced proliferation and the secretion of IL-2 and IFN-gamma. Additionally, both CD80 and CD86 transfectants were able to generate functional CTL. The magnitude and kinetics of these responses were similar, which indicates that both ligands provide efficient costimulatory signals. Because many APCs coexpress both CD80 and CD86, we compared the ability of anti-CD80 and anti-CD86 mAbs to inhibit allogeneic MLR stimulated with B lymphoblastoid cell lines and showed that it is necessary to inhibit interactions with both ligands to optimally block CD28-dependent proliferation. Given the limited homology of CD80 and CD86, it was surprising that the binding of CD28-Ig fusion protein to CD80 and that to CD86 transfectants were essentially indistinguishable. Binding of CTLA-4-Ig fusion protein to both transfectants also was quite similar, but was of higher affinity than CD28-Ig binding. Results from these studies indicate that both CD80 and CD86 are potent and similar costimulators of T lymphocytes. Therefore, the role of CD80 and CD86 in an immune response may be determined primarily by their differential expression on APC.
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PMID:CD80 (B7) and CD86 (B70) provide similar costimulatory signals for T cell proliferation, cytokine production, and generation of CTL. 752 24

Regulation of immune responses depends on interactions between APCs and T cells. Such cellular interactions are mediated by surface molecules including MHC class II Ags (DR) and CD28 ligands B7-1 (CD80) and B7-2 (CD86). Recent evidence indicates that the presence or absence of costimulatory molecules on APCs significantly influences the qualitative and quantitative nature of an immune response. In this report, we analyze two relevant cytokines in skin immunobiology, granulocyte-macrophage (GM)-CSF and IL-10, and demonstrate their effects on cultured dendritic cells obtained from dermis (DDCs) of normal skin and psoriatic lesions. For comparison, the effects on these professional APCs were contrasted with cultured blood-derived monocytes. Normal and psoriatic skin-derived DDCs express high levels of CD86 over CD80, and the overall hierarchy is DR > CD86 > CD80, whereas cultured monocytes express low and equivalent levels of CD80 and CD86. If Ab is added to GM-CSF at the initial period of cultivation, DDCs that emigrate have lower levels of CD86 without any detectable effect on CD80 or DR expression and display a reduced capacity to stimulate either superantigen-driven or alloantigen-responsive T cells. Conversely, by adding GM-CSF to monocytes, CD86 levels are enhanced. When IL-10 was added at the beginning of culture, DDCs had significantly lower levels of CD86, without any effect on CD80 or DR expression, and like anti-GM-CSF-treated cells, these DDCs had approximately a 50% reduction in their T cell-stimulating capacity. In contrast, when monocytes were treated identically with exogenously added IL-10, they retained their relatively low levels of CD80 and CD86 with no detectable change in APC function. Blocking studies of DDC:T cell interaction indicated that CD86 was more important than CD80. Thus, differential expression patterns and functional cytokine responses involving these APC populations may be relevant to skin disorders such as psoriasis, in which discordant patterns of CD28 ligand expression and disordered cytokine networks are present.
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PMID:Psoriatic skin-derived dendritic cell function is inhibited by exogenous IL-10. Differential modulation of B7-1 (CD80) and B7-2 (CD86) expression. 753 80

APC-associated B7 and ETC-1/B7-2 are two major costimulatory molecules for full activation of T lymphocytes during auto- and allogeneic immune responses. In this report, we further examine the role of the two molecules in murine CD4+ T cell activation and anergy development. As suggested in antibody blocking studies, optimal activation of CD4+ T cells in response to anti-CD3 stimulation requires collaborative signaling through the two molecules. Simultaneous blockade of B7 and ETC-1/B7-2 renders CD4+ T cells unresponsive to anti-CD3 restimulation. PCR analysis and cytokine reconstitution studies show that the observed unresponsiveness is correlated to a significant reduction of Th1-type cytokine production, suggesting B7 and ETC-1/B7-2-mediated costimulatory signaling may be specifically active in regulation of the function of the Th1 subset.
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PMID:In vitro induction of T cell anergy by blocking B7 and early T cell costimulatory molecule ETC-1/B7-2. 753 98

Human memory B cells that carry mutated IgV region genes were isolated from tonsils by negative selection of IgD+ naive B cells and CD38+ germinal center B cells and plasma cells. They were mainly found within the intraepithelial areas, but not in the B cell follicles of human tonsils. Memory B cells but not naive B cells have the capacity to present antigen directly to T cells, owing to the constitutive expression of the accessory molecules B7-1/CD80 and B7-2/CD86. Signals through antigen receptors and CD40 antigen result in these two molecules being further up-regulated more rapidly and strongly on memory B cells than on naive B cells. The unique anatomical localization of memory B cells beneath the surface of mucosa, together with their strong APC capacity, may explain the well-known prompt and robust secondary antibody responses.
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PMID:Memory B cells from human tonsils colonize mucosal epithelium and directly present antigen to T cells by rapid up-regulation of B7-1 and B7-2. 753 80

Engagement of the TCR/CD3 complex together with ligation of CD28 by its counterstructures B7-1 (CD80) and B7-2 (CD86) on APC are required for mitogenic T cell activation. After activation, T cells not only express B7-1 and B7-2 molecules, but a second receptor for the B7 ligands, CTLA-4, can be found on their surfaces. We here show that B cells can be induced to express CTLA-4 on the plasma membrane. Similar to what has been reported for T cells, CTLA-4 expression on B cells was transient. Purified B cells did not express CTLA-4 when mitogenically activated with alpha IgM and CD40 Ab, but did express the molecule when cultured in the presence of membranes from activated T cells, which suggests that induction of CTLA-4 expression on B cells was dependent on direct cell-cell contact of B lymphocytes and activated T cells. CTLA-4 molecules isolated from either T or B cells were biochemically indistinguishable. Moreover, because the ability of chimeric B7-1/Ig proteins to bind to activated B cells was correlated with CTLA-4 expression levels on these cells, we conclude that B cell-expressed CTLA-4 has ligand binding capacity. These data suggest that costimulatory receptors and their specific ligands not only play a role in T cell stimulation, but contribute in a direct fashion to the regulation of B cell responses.
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PMID:Activated T cells can induce high levels of CTLA-4 expression on B cells. 754 32

The potential role of different subsets of APCs to stimulate naive CD4+ T cells to peptide and protein Ags in vivo was examined. Mice lacking B cells (microMT knockout mice) were impaired in their priming to protein but not peptide Ags, suggesting a requirement for B cells in priming to protein Ags in vivo. Experiments designed to determine the ability of splenic dendritic cells (DCs) and B lymphocytes to take up peptide or protein Ags in vivo demonstrated that peptide Ags were taken up preferentially by DCs, whereas proteins were taken up by Ag-specific B cells in vivo. A further examination of the Ag-specific B cells pulsed in vivo with protein Ags revealed a marked up-regulation in surface expression of B7-2 costimulatory molecules, detectable as early as 4 h after Ag administration. Based on their potency in the uptake and processing of protein Ags as well as their ability to up-regulate costimulatory molecules through Ag internalization, we suggest that Ag-specific B cells will be an important APC in priming naive CD4+ T cells to protein Ags in vivo.
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PMID:B lymphocytes can be competent antigen-presenting cells for priming CD4+ T cells to protein antigens in vivo. 756 Oct 77

Dendritic cells (DC) are the principle APC involved in primary immune responses; their major function is to obtain Ag in tissues, migrate to lymphoid organs, and activate T cells. DC are also the first immune cells to arrive at sites of inflammation on mucous membranes, the major site of sexual transmission of HIV. We have demonstrated previously that three populations of cells that can develop a dendritic morphology are present in peripheral blood. Two of these populations can express CD83, a marker of DC, and appear to be at different stages of maturation: 1) a precursor population and 2) a mature immunostimulatory DC. Precursor-derived DC express high levels of CD86 (B7-2) and HLA-DR but no CD80 (B7-1), whereas mature DC have high levels of expression of all three markers. Mature DC in peripheral blood bind HIV to their surface and induce infection when added to autologous CD4+ T cells in the absence of added stimuli, such as mitogens. These mature DC, when isolated directly from peripheral blood, appear to be conjugated to T cells, and these conjugates are infected easily and productively with HIV. These findings suggest a role for DC in early HIV infection in which they bind virus and interact with T cells locally or after migrating to a lymphoid organ, thus establishing a productive infection. Furthermore, they likely play a role in the propagation of HIV infection by activating T cells in the presence of HIV, which leads to viral replication and immune cell destruction.
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PMID:Both a precursor and a mature population of dendritic cells can bind HIV. However, only the mature population that expresses CD80 can pass infection to unstimulated CD4+ T cells. 756 Nov 24


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