Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.69 (APC)
 16,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recent investigations in antigen processing suggest that many hematopoietic and nonhematopoietic cell types are capable of presenting alloantigen to T lymphocytes. However, the role of certain nonclassical antigen presenting cells is blurred by their apparent ability to down-regulate the immune response as well as activate immune cells, depending upon the microenvironment and the functional state of the responding cells. In this study we examine the ability of cultured allogeneic keratinocytes to inhibit the response of naive T cells to alloantigen or to anti-CD3. Our results demonstrate that as few as 6.25 x 10(3) keratinocytes significantly inhibited T cell proliferation in response to alloantigen as well as anti-CD3-mediated stimulation (49 and 54%, respectively). HK-mediated inhibition of T cell proliferation did not require cell contact, suggesting that inhibition is mediated by cytokines or other soluble factors. This was further supported by experiments demonstrating the inducibility of HK inhibitory activity in the presence of FCS, and the partial blockage of HK inhibitory activity through the addition of indomethacin or anti-TGFbeta antibody. Interestingly, the data suggest that IL-10, a known immunomodulatory cytokine, does not play a role in the inhibitory activity seen in this system. Taken together the results suggest that HK have the potential to regulate the response of T cells to antigen presented by other APC through the production of soluble factors.
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PMID:Normal human keratinocytes inhibit the proliferation of unprimed T cells by TGFbeta and PGE2, but not IL-10. 901 84

We have previously reported the cloning of a novel cytokine, IFN-gamma-inducing factor (IGIF), which shared some biologic activities with IL-12. In this study, we analyzed the effects of murine IGIF on the activation of T cells, and compared the effects with those of IL-12. IGIF alone had no effect on the activation of T cell lines or Th1 clones, while IGIF increased the IFN-gamma production by antigen-stimulated T cell lines, but had no effect on IL-4 or IL-10 production. As reported with IL-12, IGIF served as a costimulatory factor for Th1 clones stimulated with Ag on B cell APC, immobilized anti-CD3, Con A, or IL-2 to augment IFN-gamma production and to induce IL-2R alpha-chain expression and proliferation of the Th1 clones, whereas IGIF had little or no effect on the IL-4 production and proliferation of Th2 clones stimulated with anti-CD3 or Ag. However, IGIF synergized with IL-12 to further augment the IFN-gamma production of the Th1 clones. Even in the presence of saturated amounts of IL-12, IGIF still augmented the IFN-gamma production and proliferation and enhanced the IL-2R alpha-chain expression of the Th1 clones. In contrast with IL-12, IGIF induced IL-2 production by Ag- or anti-CD3-stimulated Th1 clones. These two findings indicate that IGIF and IL-12 are utilizing different signal transduction pathways. We also found that IGIF as well as IL-12 was endogenously released through interaction between Th1 cells and spleen cell APC in the presence of specific Ag, and that it regulated IFN-gamma production. These results further suggest that IGIF may act as an immunoregulatory factor in the immune response.
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PMID:IFN-gamma-inducing factor (IGIF) is a costimulatory factor on the activation of Th1 but not Th2 cells and exerts its effect independently of IL-12. 902 88

Peripheral blood V gamma 9/V delta 2 T cells proliferate vigorously in response to heat-killed Mycobacterium tuberculosis (Mtb) and Daudi Burkitt's lymphoma cells. We have analyzed the respective roles of IL-10 and IL-12 in gamma delta T cell activation, using the selective expansion of V gamma 9 cells in Mtb- or Daudi-stimulated PBMC as a readout. IL-10 inhibited in a dose-dependent fashion the V gamma 9 responsiveness to Mtb. In contrast, IL-10 did not impair reactivity toward Daudi cells, even when added at 10 ng/ml. The inhibitory action of IL-10 could be overcome by the exogenous supply of IL-2 or IL-12. Blockade of endogenous IL-10 by neutralizing mAb increased responsiveness to Mtb but not to Daudi cells. Low concentrations of exogenous IL-12 increased the V gamma 9 responsiveness to Mtb in 6 of 11 healthy donors. In contrast, IL-12 inhibited V gamma 9 cell expansion in response to Daudi stimulation in all of the tested individuals. Neutralizing anti-IL-12 Ab significantly suppressed V gamma 9 responsiveness to Mtb in IL-12 nonresponders but only slightly inhibited the latter responsiveness in IL-12 responders. The effect of anti-IL-12 Ab correlated with the level of Mtb-stimulated endogenous IL-12 production. In purified gamma delta T cells, IL-12 synergized with IL-2 to stimulate cellular expansion in response to Daudi cells. This effect was reduced when T cell-depleted APC were added back. Finally, neutralization of endogenous IFN-gamma by Ab abrogated V gamma 9 cell responsiveness to Mtb but exerted only a minor inhibition of the reactivity toward Daudi cells. Taken together, these results reveal significant differences in the cytokine requirement of gamma delta T cell activation by Mtb or Daudi lymphoma cells, respectively.
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PMID:Activation of human gamma delta T cells by Mycobacterium tuberculosis and Daudi lymphoma cells: differential regulatory effect of IL-10 and IL-12. 905 20

Injection of goat anti-mouse IgD antibody (G alpha M IgD) to mice has been shown to induce polyclonal IgG1 and IgE production by B cells and IL-4 production by goat Ig-specific T cells. Surface IgD crosslinking also activates function of B cells as antigen presenting cells. Although the G alpha M IgD treatment is a well established system for regulation of immune response against antigens that bind to B cell receptor, we found that the G alpha M IgD treatment also influences immune response against irrelevant bacterial antigen. The T cells from the G alpha M IgD-treated Listeria monocytogenes-infected mice showed increased IL-4 production and decreased IFN-gamma and IL-2 production against listerial antigen compared with those from control L. monocytogenes-infected mice. Interestingly, changes were also found in antigen presenting cells in the G alpha M IgD-treated mice. MHC class II expression of both B cells and macrophages decreased significantly in the G alpha M IgD-treated mice, suggesting cytokine induced by G alpha M IgD-treatment may suppress MHC class II expression and modulate APC function in the G alpha M IgD-treated mice. In accordance with the assumption, T cells from the G alpha M IgD-treated mice produced high amount of IL-4 and IL-10 in in vitro culture with goat serum which contain goat Ig. These result suggest that G alpha M IgD treatment may modulate APC function in the G alpha M IgD-treated mice through Th2 type cytokine(s) produced by goat Ig-specific T cells, which results in changes of Th response against irrelevant antigen.
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PMID:Down-regulation of Listeria monocytogenes-specific Th1 cytokine response by treatment of mice with goat antibody to mouse IgD. 906 84

T cells from the intestinal mucosal proliferate poorly in vitro, and the contribution of Ag-specific recognition to this hyporesponsiveness is unclear, since the Ag repertoire of intestinal mucosal T cells is unknown. In this study, T cell proliferation in response to Ag-prepulsed autologous peripheral blood-derived APC was examined. Whereas T cells from peripheral blood proliferated to inner membrane and cytoplasmic Escherichia coli proteins, T cells from intestinal mucosa responded only to purified component Ags of these proteins and not to their combination. This suggests that the lack of proliferation in response to these Ags presented as a mixture is not due to the absence of E. coli-specific T cells in the mucosa, but, rather, to down-regulation after T cell recognition. Down-regulation was assayed by measuring the inhibition of autologous peripheral blood T cell proliferation in response to Ag-prepulsed APC. Coculture with leukocytes from intestinal mucosa and not from mesenteric lymph nodes, inhibited autologous peripheral blood T cell proliferation in response to E. coli proteins, but not to tetanus toxoid, PHA, or IL-2. Inhibition was independent of cell contact, provided APC were available to the mucosal cell population, and was reversible by neutralization of IL-10 or TGF-beta with mAb or depletion of mucosal CD4+ T cells. Taken together, the data suggest that mucosal T cell unresponsiveness to luminal Ags is mediated by production of inhibitory cytokines after specific Ag recognition by CD4+ T cells.
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PMID:CD4+ T cell down-regulation in human intestinal mucosa: evidence for intestinal tolerance to luminal bacterial antigens. 910 24

The immune response and immunopathologic manifestations in schistosomiasis are largely dependent on Ag-specific CD4+ Th cells. In turn, the stimulatory/regulatory function of the Th cells is dependent on signals emanating from accessory cells. B cells are capable of functioning as accessory cells, and their role in experimental murine schistosomiasis was investigated by using mice with targeted mutations in the J(H) locus. This phenotype results in the absence of B cells and of Ab production. After 7.5- to 8-wk infections, mesenteric lymph node cells from the JHD B-less mice displayed lower proliferative responses to schistosomal egg Ag than did cells from infected control mice. Most importantly, compared with cells from controls, egg Ag-stimulated JHD lymph node cells produced significantly higher amounts of the Th1 response-associated cytokines IFN-gamma and IL-12, while their production of the Th2-type cytokines IL-4 and IL-10 was dramatically reduced or undetectable. Similarly, irradiated splenocytes from uninfected JHD mice, used as APC, elicited significantly stronger Th1 and weaker Th2 responses from egg Ag-specific CD4+ Th cells than splenocytes from control mice. Despite these sharply contrasting cytokine profiles, there were no significant differences either in the size and composition of the resulting egg granulomas or in the number of deposited eggs in the livers of infected JHD vs control mice. Taken together, the findings in the JHD mouse reflect an impairment in the ability to mount a Th2 response, which translates into a loss of the Th1 to Th2 switch characteristically seen in normal schistosome-infected mice. These results suggest that B cells promote Th2-type responses, and that typical granulomatous responses proceed in their absence.
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PMID:In infection with Schistosoma mansoni, B cells are required for T helper type 2 cell responses but not for granuloma formation. 914 98

A wide variety of human tumors express IL-10 for reasons poorly understood. We have analyzed the effect of spontaneous IL-10 expression by a mouse tumor (J558L) on its immunoparalyzing effect. Because "cross-priming" of T cells by host Ag-presenting cells for MHC class I-restricted tumor Ags is a major pathway for induction of tumor immunity and that is enhanced by granulocyte-macrophage (GM) CSF, we expressed this cytokine in J558L cells. GM-CSF-secreting cells were not effective when used for immunization against challenge with the parental tumor. Inhibition of IL-10 expression through an IL-10 antisense retrovirus restored the vaccine efficacy of GM-CSF-producing J558L cells, demonstrating a direct role of IL-10 in paralyzing the GM-CSF-induced antitumor immune response. Since the tumor used for challenge produced IL-10, we conclude that IL-10 interfered primarily with the initiation but not the effector phase of the immune response. Immunohistochemical analysis of the vaccine site showed a GM-CSF-induced accumulation of dendritic cells (DC) (MHC class II+ and DEC-205+) in the absence of IL-10. In the presence of IL-10, DC accumulation was completely inhibited. Together, our results demonstrate an antagonistic effect of IL-10 with respect to GM-CSF-induced DC accumulation and tumor immunity and suggest a new mechanism by which tumors escape immune recognition: namely by preventing APC from obtaining access to tumor Ags.
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PMID:Interleukin-10 prevents dendritic cell accumulation and vaccination with granulocyte-macrophage colony-stimulating factor gene-modified tumor cells. 921 94

IL-12, a 75-kDa heterodimeric cytokine composed of two chains (p35 and p40), is a central regulator of immune responses and may be implicated in the pathogenesis of certain inflammatory diseases of the central nervous system (CNS). We have examined the capacity of two CNS APC, microglia and astrocytes, to produce IL-12 upon stimulation with cytokines, LPS, or a neurotropic virus. In purified microglial cultures from neonatal mouse brains, expression of IL-12 p35 and p40 mRNA is induced by LPS and is stimulated maximally by combined IFN-gamma/LPS treatment, as detected by semiquantitative reverse-transcriptase PCR. LPS induces secretion of IL-12 p40, but not of IL-12 p75, as detected by specific ELISA. Combined stimulation with IFN-gamma/LPS enhances IL-12 p40 secretion and induces IL-12 p75 secretion by microglia. Conversely, mouse astrocytes do not express IL-12 p35 mRNA and do not secrete IL-12 p75 under any condition tested. IL-12 production by activated microglia is inhibited by IL-10, PGE2, and cAMP-elevating agents. Coculture of microglia with astrocytes or exposure of microglia to astrocyte-conditioned medium also results in marked reduction of IL-12 p75 and p40 secretion by IFN-gamma/LPS-stimulated microglia, indicating a regulatory role of astrocytes on IL-12 production. This novel mechanism of IL-12 regulation may play an important role in the control of immune responses during infection or in Th1 cell-mediated autoimmune diseases of the CNS.
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PMID:IL-12 production by central nervous system microglia is inhibited by astrocytes. 925 19

The immune system changes during the lifespan of man. Many described changes in the immune system of the elderly were dependent on illness or chronic diseases. To exclude these pathological changes in the immune system and to exclusively describe age-dependent changes, Ligthart et al. defined immunogerontological criteria to study the immune system in the elderly, the SENIEUR-Protocol. Most changes in the immune system of elderly are within the normal ranges of the appropriate parameter. However, there are many significant differences between the status of the immune system in healthy young and elderly individuals, within these normal ranges. The comparison between SENIEUR-elderly and healthy young and the additional comparison of these two groups with centenarians allows the discussion of potential pathological effects of these changes. In this article we summarize the described changes of the immune system in SENIEUR-elderly and centenarians. The serum levels of the immunoglobulins G, M and A increased with age, as well as the number of benign monoclonal gammopathies and the number of autoantibodies. The titers of zinc are significantly decreased in the serum of the elderly. The production of the acute phase protein C-reactive protein is not age-dependent, whereas the serum levels of alpha 2-macroglobulin are significantly increased in the elderly. The number of lymphocytes decreased and the number of neutrophils increased with aging. Monocytes, basophils, and eosinophils are without changes during life. There are many descriptions about changes of the leukocyte sub-population in aging, which are not always comparable. However, the number of T cells (CD3) decreases. Within the T cells the CD8 cells decreased more than the CD4 cells, resulting in an increased CD4/CD8 ratio. Memory T cells (CD45RO) increase during life, whereas naive T cells (CD45RA) decrease. Interestingly, centenarians have more naive T cells SENIEUR-elderly. The number of B cells (CD19) decreased also, whereas the number of natural killer (NK) cells (CD16, CD56, CD57) increases with aging. The capacity of leukocytes from the elderly to produce cytokines is also significantly different from those of the young. The release of the TH1-cytokines interleukin (IL)-2 and interferon (IFN)-gamma is decreased, whereas the production of the TH2-cytokines IL-4 and IL-10 is increased in the elderly. The production of proinflammatory cytokines such as IL-1, IL-6, IL-8, and tumor necrosis factor-alpha is increased in the elderly. In contrast, the capacity to produce the antiviral cytokine IFN-alpha is reduced in elderly individuals. In conclusion, the immune system shows many age-dependent changes, but we know little about the reason and the potential pathological effects of these changes.
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PMID:[Characteristics of immunologic test values in the elderly]. 933 53

Dendritic cells (DC) form a specialized system for presenting Ag to naive or quiescent T cells and consequently play a central role in the induction of T and B cell immunity. In this study we used DC generated from peripheral progenitors to analyze the effect of IL-10 on the accessory function of human DC. We demonstrate that immature DC, harvested on days 9 to 11 and exposed to IL-10 for the last 2 days of culture, show a strongly reduced capacity to stimulate a CD4+ T cell response in an allogeneic MLR in a dose-dependent manner. In contrast, fully mature DC are completely resistant to the effects of IL-10. These results were obtained in both an alloantigen-induced MLR and an anti-CD3 mAb-induced response of primed and naive (CD45RA+) CD4+ T cells. FACS analysis revealed inhibition of the up-regulation of the costimulatory molecules CD58 and CD86 and the specific DC marker CD83 in DC pretreated with IL-10. These data suggest that IL-10 inhibited the development of fully mature DC. Furthermore, DC precultured with IL-10, but not controls, induced a state of alloantigen-specific anergy in CD4+ T cells and of peptide-specific anergy in the influenza hemagglutinin-specific T cell clone HA1.7. Analysis of the supernatants of these anergic T cells revealed a reduced production of IL-2 and IFN-gamma compared with that in control cells. Collectively, these data suggest that IL-10 converts immature DC into tolerogenic APC, which might be a useful tool in the therapy of patients with autoimmune or allergic diseases.
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PMID:Induction of tolerance by IL-10-treated dendritic cells. 936 1


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