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

OX40 ligand (OX40L), a member of the TNF family, was shown to be capable of signaling both the cells on which it is expressed and those expressing OX40, its cognate receptor. Here we show that OX40L is expressed on dendritic cells (DC), the most efficient APC to prime naive T cells. The expression and the functional activity of OX40L were examined by means of mAbs used to stain or cross-link OX40L on 1) freshly isolated human blood DC (bDC) and 2) monocyte-derived DC at different stages of differentiation. These were derived from monocytes cultured either with IL-4 and granulocyte-macrophage CSF (IL-4-Mo-DC) or with IL-4 and granulocyte-macrophage CSF plus TNF-alpha. Both types of Mo-DC expressed OX40L after stimulation through CD40; ligation of OX40L on activated IL-4-Mo-DC enhanced by 4- to 35-fold their cytokine production (TNF-alpha, IL-12 p40, IL-1 beta, and IL-6) and increased CD80, CD86, CD54, and CD40 expression. Stimulation of activated IL-4-Mo-DC through OX40L strikingly enhanced their maturation as evidenced by CD83 up-regulation, CD115 (CSF-1R) down-regulation, and typical morphologic changes. OX40L was constitutively expressed on a subset of bDC, and its ligation slightly enhanced CD40L-stimulated IL-12 production. OX40L was down-regulated after overnight culture and spontaneously reexpressed on a subset of mature bDC (CD83high, CD33high, CD11chigh, CD5+). Thus, the expression of OX40L on DC suggests a physiologic role of this molecule during T cell priming by virtue of its ability to costimulate both T cell and DC activation and differentiation.
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PMID:Expression and function of OX40 ligand on human dendritic cells. 937 71

The OX-40R is a member of the TNF receptor family and is expressed primarily on activated CD4+ T cells. When the OX-40R is engaged by the OX-40 ligand (OX-40L), a potent costimulatory signal occurs. We have identified a population of CD11b+ cells, isolated from the central nervous system (CNS) of mice with actively induced experimental allergic encephalomyelitis (EAE), that expresses OX-40L. Moreover, the expression of OX-40L was found to be associated with paralytic episodes of EAE and was reduced or absent at disease recovery. These CD11b+ cells also coexpressed B7 and MHC class II. Therefore, to address the relative contributions of OX-40R/OX-40L and CD28/B7 to the costimulation of myelin-specific T cells, blocking studies were performed using soluble OX-40R and/or soluble CTLA-4. CD11b+ cells isolated from the CNS of mice with actively induced EAE were able to present Ag to proteolipid protein 139-151-specific T cell lines in vitro. The addition of soluble OX-40R:Ig to CD11b+ brain microglia/macrophages inhibited T cell proliferation by 50-70%. The addition of CTLA-4:Ig inhibited T cell proliferation by 20-30%, and the combination inhibited T cell proliferation by 95%. In vivo administration of soluble OX-40R at the onset of actively induced or adoptively transferred EAE reduced ongoing signs of disease, and the mice recovered more quickly from acute disease. The data imply that OX-40L, expressed by CNS-derived APC, acts to provide an important costimulatory signal to EAE effector T cells found within the inflammatory lesions. Furthermore, the data suggest that agents designed to inhibit the OX-40L/OX-40R complex may be useful for treating autoimmune disease.
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PMID:Blocking OX-40/OX-40 ligand interaction in vitro and in vivo leads to decreased T cell function and amelioration of experimental allergic encephalomyelitis. 997 47

OX40 ligand (OX40L) expressed on APCs, and its receptor, OX40 present on activated T cells, are members of the TNF/TNFR family, respectively, and have been located at the sites of inflammatory conditions. We have observed in OX40L-deficient mice (OX40L(-/-)) an impaired APC capacity and in our recently constructed transgenic mice expressing OX40L (OX40L-Tg), a markedly enhanced T cell response to protein Ags. Using these mice, we demonstrate here the critical involvement of the OX40L-OX40 interaction during the T cell priming events in the occurrence of experimental autoimmune encephalomyelitis (EAE). In OX40L(-/-) mice, abortive T cell priming greatly reduced the clinical manifestations of actively induced EAE, coupled with a reduction in IFN-gamma, IL-2, and IL-6 production in vitro. Adoptive transfer experiments however revealed an efficient transfer of disease to OX40L(-/-) mice using wild-type donor T cells, indicating an intact capacity of OX40L(-/-) mice to initiate effector responses. On the other hand, OX40L(-/-) donor T cells failed to transfer disease to wild-type recipient mice. Furthermore, OX40L-Tg mice developed a greater severity of EAE despite a delayed onset, while both OX40L-Tg/CD28(-/-) and OX40L-Tg/CD40(-/-) mice failed to develop EAE demonstrating a requisite for these molecules. These findings indicate a pivotal role played by OX40L in the pathogenesis of EAE.
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PMID:Critical involvement of OX40 ligand signals in the T cell priming events during experimental autoimmune encephalomyelitis. 1150 50

The interaction between OX40 and OX40 ligand (OX40L) is suggested to provide T cells with an effective costimulatory signals during T cell-APC interaction. To examine the in vivo effect of constitutive OX40/OX40L interaction during immune regulation, we report the establishment of OX40L-transgenic (OX40L-Tg) mice that constitutively express OX40L on T cells. Markedly elevated numbers of effector memory CD4(+) T cells, but not CD8(+) T cells, were observed in the secondary lymphoid organs of OX40L-Tg mice. Upon immunization with keyhole limpet hemocyanin in the absence of adjuvant, profound T cell proliferative responses and cytokine productions were seen in the OX40L-Tg mice as compared with wild-type mice. Furthermore, in OX40L-Tg mice administrated with superantigen, this constitutive OX40/OX40L interaction on CD4(+) T cells completely prevented normal in vivo clonal T cell deletion. Interestingly, OX40L-Tg mice on the C57BL/6 background spontaneously developed interstitial pneumonia and inflammatory bowel disease that was accompanied with a significant production of anti-DNA Ab in the sera. Surprisingly, these diseases were not evident on the OX40L-Tg mice on the BALB/c strain. However, such inflammatory diseases were successfully reproducible in recombination-activating gene (RAG)2-deficient mice upon transfer of OX40L-Tg CD4(+) T cells. Blockade of OX40/OX40L interaction in the recipient RAG2-deficient mice completely prevented disease development. The present results orchestrated in this study indicate that OX40/OX40L interaction may be a vital link in our understanding of T cell-mediated organ-specific autoimmunity.
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PMID:Constitutive OX40/OX40 ligand interaction induces autoimmune-like diseases. 1237 Apr 2

Efficient T cell priming by GM-CSF and CD40 ligand double-transduced C26 murine colon carcinoma is not sufficient to cure metastases in a therapeutic setting. To determine whether a cellular vaccine that interacts directly with both APC and T cells in vivo might be superior, we generated C26 carcinoma cells transduced with the T cell costimulatory molecule OX40 ligand (OX40L) either alone (C26/OX40L) or together with GM-CSF (C26/GM/OX40L), which is known to activate APC. Mice injected with C26/OX40L cells displayed only a delay in tumor growth, while the C26/GM/OX40L tumor regressed in 85% of mice. Tumor rejection required granulocytes, CD4+, CD8+ T cells, and APC-mediated CD40-CD40 ligand cosignaling, but not IFN-gamma or IL-12 as shown using subset-depleted and knockout (KO) mice. CD40KO mice primed with C26/GM/OX40L cells failed to mount a CTL response, and T cells infiltrating the C26/GM/OX40L tumor were OX40 negative, suggesting an impairment in APC-T cell cross-talk in CD40KO mice. Indeed, CD4+ T cell-depleted mice failed to mount any CTL activity against the C26 tumor, while treatment with agonistic mAb to CD40, which acts on APC, bypassed the requirement for CD4+ T cells and restored CTL activation. C26/GM/OX40L cells cured 83% of mice bearing lung metastases, whereas C26/OX40L or C26/GM vaccination cured only 28 and 16% of mice, respectively. These results indicate the synergistic activity of OX40L and GM-CSF in a therapeutic setting.
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PMID:OX40 ligand-transduced tumor cell vaccine synergizes with GM-CSF and requires CD40-Apc signaling to boost the host T cell antitumor response. 1249 88

OX40/OX40 ligand (OX40L) interactions have been shown to exert potent costimulatory effects on T-cell activation. OX40 expression is transiently up-regulated on T cells following T-cell receptor engagement, while OX40L is expressed on antigen-presenting cells following activation. Although expression of the OX40L by T cells has been reported, the requirements for induction of OX40L on T cells have not been studied in detail. Here, we demonstrate that the OX40L can be induced on murine CD4(+) and CD8(+) T cells after 6 days of culture under T helper type 1 (Th1) conditions, but not under Th2 conditions. Induction of OX40L expression required a high concentration of interleukin-12 (IL-12), was not seen in the presence of interferon-gamma, and was dependent on signal transducer and activator of transcription type 4 (STAT4). Notably, induction of OX40L on T cells was only seen at very low concentrations of antigen or anti-CD3. T-cell-expressed OX40L was fully capable of delivering a potent costimulatory signal that enhanced the proliferation of CD4(+) T cells as well as promoted their differentiation to Th2 cells. OX40L expression could also be induced on CD4(+) T cells in vivo following immunization with low-dose antigen and an IL-12 inducer. OX40/OX40L interactions between antigen-specific T cells may occur in T-cell zones in lymph node and spleen when OX40L expression has diminished on APC. Costimulation by T-cell-expressed OX40L may result in deviation of a Th1 response to a Th2 response under conditions where T cells are exposed to low concentrations of foreign or autoantigens in the presence of high concentrations of IL-12.
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PMID:Activated T cells express the OX40 ligand: requirements for induction and costimulatory function. 1642 55

Signals through the OX40 costimulatory receptor on naive CD4 T cells are essential for full-fledged CD4 T cell activation and the generation of CD4 memory T cells. Because the ligand for OX40 is mainly expressed by APCs, including activated B cells, dendritic cells, and Langerhans cells, the OX40-OX40 ligand (OX40L) interaction has been thought to participate in T cell-APC interactions. Although several reports have revealed the expression of OX40L on T cells, the functional significance of its expression on them is still unclear. In this study, we demonstrate that Ag stimulation induced an increase in the surface expression and transcript levels of OX40L in CD4 T cells. Upon contact with OX40-expressing T cells, the cell surface expression of OX40L on CD4 T cells was markedly down-regulated, suggesting that OX40-OX40L binding occurs through a novel T cell-T cell interaction. To investigate the function of this phenomenon, we examined the proliferative response and survival of OX40L-deficient CD4 T cells when challenged with Ag. In vitro studies demonstrated markedly less CD3-induced proliferation of OX40L-deficient CD4 T cells compared with wild-type CD4 T cells. When using TCR transgenic CD4 T cells upon Ag stimulation, survival of OX40L-deficient T cells was impaired. Furthermore, we show that upon antigenic stimulation, fewer OX40L-deficient CD4 T cells than wild-type cells survived following transfer into wild-type and sublethally irradiated recipient mice. Taken together, our findings indicate that OX40L-expressing T cells have an autonomous machinery that provides OX40 signals through a T cell-T cell circuit, creating an additional mechanism for sustaining CD4 T cell longevity.
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PMID:OX40-OX40 ligand interaction through T cell-T cell contact contributes to CD4 T cell longevity. 1667 Mar 6

Herpes stromal keratitis (HSK) is an immunopathological disease regulated by Th1 CD4 T cells, which require APC and costimulation within the infected cornea to mediate disease. Recent studies suggest the OX40:OX40 ligand (OX40L) interaction enhances effector cell cytokine secretion at inflammatory sites. OX40(+) cells were detected in HSV-1-infected mouse corneas as early as 3 days postinfection (dpi), prior to the onset of HSK, and their frequency increased through 15 dpi, when all mice exhibited severe HSK. OX40L(+) cells were first detected at 7 dpi, coincident with the initiation of HSK. It is interesting that the OX40L(+) cells did not coexpress MHC Class II or the dendritic cell (DC) marker CD11c. Our findings demonstrate rapid infiltration of activated (OX40(+)) CD4(+) T cells into HSV-1-infected corneas and expression of OX40L on MHC Class II-negative cells but surprisingly, not on MHC Class II(+) CD11c(+) DC, which are present in the infected corneas and required for HSK. Moreover, neither local nor systemic treatment of mice with a blocking antibody to OX40L or with a blocking fusion protein altered the course of HSK significantly, possibly as a result of a lack of OX40L expression on functional APC.
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PMID:Expression and function of the OX40/OX40L costimulatory pair during herpes stromal keratitis. 1718 58