Showing papers on "Interferon published in 1997"
TL;DR: Much of the cellular response to IFN-gamma can be described in terms of a set of integrated molecular programs underlying well-defined physiological systems, for example the induction of efficient antigen processing for MHC-mediated antigen presentation, which play clearly defined roles in pathogen resistance.
Abstract: Interferons are cytokines that play a complex and central role in the resistance of mammalian hosts to pathogens. Type I interferon (IFN-alpha and IFN-beta) is secreted by virus-infected cells. Immune, type II, or gamma-interferon (IFN-gamma) is secreted by thymus-derived (T) cells under certain conditions of activation and by natural killer (NK) cells. Although originally defined as an agent with direct antiviral activity, the properties of IFN-gamma include regulation of several aspects of the immune response, stimulation of bactericidal activity of phagocytes, stimulation of antigen presentation through class I and class II major histocompatibility complex (MHC) molecules, orchestration of leukocyte-endothelium interactions, effects on cell proliferation and apoptosis, as well as the stimulation and repression of a variety of genes whose functional significance remains obscure. The implementation of such a variety of effects by a single cytokine is achieved by complex patterns of cell-specific gene regulation: Several IFN-gamma-regulated genes are themselves components of transcription factors. The IFN-gamma response is itself regulated by interaction with responses to other cytokines including IFN-alpha/beta, TNF-alpha, and IL-4. Over 200 genes are now known to be regulated by IFN-gamma and they are listed in a World Wide Web document that accompanies this review. However, much of the cellular response to IFN-gamma can be described in terms of a set of integrated molecular programs underlying well-defined physiological systems, for example the induction of efficient antigen processing for MHC-mediated antigen presentation, which play clearly defined roles in pathogen resistance. A promising approach to the complexity of the IFN-gamma response is to extend the analysis of the less understood IFN-gamma-regulated genes in terms of molecular programs functional in pathogen resistance.
2,956 citations
TL;DR: It is reported that a defined cocktail of tumor necrosis factor (TNF)‐α, IL‐1β and IL‐6 equals MCM in its potency to generate DC and that addition of PGE2 further enhances the yield and quality of DC generated.
Abstract: Culture conditions for human dendritic cells (DC) have been developed by several laboratories. Most of these culture methods, however, have used conditions involving fetal calf serum (FCS) to generate DC in the presence of granulocyte-macrophage colony-stimulating factor and interleukin (IL)-4. Recently, alternative culture conditions have been described using an additional stimulation with monocyte-conditioned medium (MCM) and FCS-free media to generate DC. As MCM is a rather undefined cocktail, the yield and quality of DC generated by these cultures varies substantially. We report that a defined cocktail of tumor necrosis factor (TNF)-alpha, IL-1beta and IL-6 equals MCM in its potency to generate DC. Addition of prostaglandin (PG)E2 to the cytokine cocktail further enhanced the yield, maturation, migratory and immunostimulatory capacity of the DC generated. More importantly, culture conditions also influenced the outcome of the T cell response induced. DC cultured with TNF-alpha/IL-1/IL-6 or MCM alone induced CD4+ T cells that release intermediate levels of interferon (IFN)-gamma and no IL-4 or IL-10. Production of IFN-gamma was significantly induced by addition of PGE2, while no effect on production of IL-4 or IL-10 was observed. Even more striking differences were observed for CD8+ T cells. While MCM conditions only induced IFN-gamma(low), IL-4(neg) cells, TNF-alpha/IL-1/IL-6 promoted growth of IFN-gamma(intermediate), IL-4(neg) CD8+ T cells. Addition of PGE2 again only further polarized this pattern enhancing IFN-gamma production by alloreactive CD8+ T cells in both cultures without inducing type 2 cytokines. Taken together, the data indicate that the defined cocktail TNF-alpha/IL-1/IL-6 can substitute for MCM and that addition of PGE2 further enhances the yield and quality of DC generated. TNF-alpha/IL-1, IL-6 + PGE2-cultured DC seem to be optimal for generation of IFN-gamma-producing CD4/CD8+ T cells.
1,209 citations
TL;DR: The results implicate caspase-1 in the physiological production of IGIF and demonstrate that it plays a critical role in the regulation of multiple proinflammatory cytokines, which would provide a new class of anti-inflammatory drugs with multipotent action.
Abstract: Interferon-gamma-inducing factor (IGIF, interleukin-18) is a recently described cytokine that shares structural features with the interleukin-1 (IL-1) family of proteins and functional properties with IL-12. Like IL-12, IGIF is a potent inducer of interferon (IFN)-gamma from T cells and natural killer cells. IGIF is synthesized as a biologically inactive precursor molecule (proIGIF). The cellular production of IL-1beta, a cytokine implicated in a variety of inflammatory diseases, requires cleavage of its precursor (proIL-1beta) at an Asp-X site by interleukin-1beta-converting enzyme (ICE, recently termed caspase-1). The Asp-X sequence at the putative processing site in proIGIF suggests that a protease such as caspase-1 might be involved in the maturation of IGIF. Here we demonstrate that caspase-1 processes proIGIF and proIL-1beta with equivalent efficiencies in vitro. A selective caspase-1 inhibitor blocks both lipopolysaccharide-induced IL-1beta and IFN-gamma production from human mononuclear cells. Furthermore, caspase-1-deficient mice are defective in lipopolysaccharide-induced IFN-gamma production. Our results thus implicate caspase-1 in the physiological production of IGIF and demonstrate that it plays a critical role in the regulation of multiple proinflammatory cytokines. Specific caspase-1 inhibitors would provide a new class of anti-inflammatory drugs with multipotent action.
1,137 citations
TL;DR: CpG ODN provide a signal to switch on Th1-dominated responses to coadministered antigen and are potential adjuvants for human vaccines to elicit protective Th1 immunity.
Abstract: Synthetic oligodeoxynucleotides (ODN) that contain unmethylated CpG motifs (CpG ODN) induce macrophages to secrete IL-12, which induces interferon (IFN)-γ secretion by natural killer (NK) cells. Since these cytokines can induce T helper 1 (Th1) differentiation, we examined the effects of coadministered CpG ODN on the differentiation of Th responses to hen egg lysozyme (HEL). In both BALB/c (Th2-biased) and B10.D2 (Th1-biased) mice, immunization with HEL in incomplete Freund's adjuvant (IFA) resulted in Th2-dominated immune responses characterized by HEL-specific secretion of IL-5 but not IFN-γ. In contrast, immunization with IFA-HEL plus CpG ODN switched the immune response to a Th1-dominated cytokine pattern, with high levels of HEL-specific IFN-γ secretion and decreased HEL-specific IL-5 production. IFA-HEL plus CpG ODN also induced anti-HEL IgG2a (a Th1-associated isotype), which was not induced by IFA-HEL alone. Control non–CpG ODN did not induce IFN-γ or IgG2a, excepting lesser increases in B10.D2 (Th1-biased) mice. Thus, CpG ODN provide a signal to switch on Th1-dominated responses to coadministered antigen and are potential adjuvants for human vaccines to elicit protective Th1 immunity.
1,100 citations
TL;DR: It is reported that NS5A represses PKR through a direct interaction with the protein kinase catalytic domain and that both PKR repression and interaction requires the ISDR, suggesting inactivation of PKR may be one mechanism by which HCV avoids the antiviral effects of IFN.
841 citations
TL;DR: RHuMig and rIP‐10 share additional activities, including inhibition of neovascularization, inhibition of hematopoietic progenitor cells, and anti‐tumor effects, and that, despite their similar activities assayed in vitro, Mig and IP‐10/Crg‐2 may serve non‐redundant functions in vivo.
Abstract: Mig and IP-lO are related members of the cxc subfamily of the chemokine family of cytokines. The murine Mig (MuMig), human IP-lO, and the mouse homologue of IP..1O, Crg-2, were all identified due to the dramatic inductions oftheir genes in monocytic cells treated with interferon-'y (IFN-'y). Studies using recombinant (r) human proteins show that, unlike most other CXC chemokines, rHuMig and rIP-lO have no activity on neutrophils but appear to target lympho- cytes specifically. rHuMig and rIP-lO are active as che- motactic factors for stimulated, but not for resting, T cells. Studies done in vitro and in vivo have shown that rHuMig and rIP-lO share additional activities, in- cluding inhibition of neovascularization, inhibition of hematopoietic progenitor cells, and anti-tumor effects. rlluMig and rIP-tO show reciprocal desensitization on activated T cells and have been demonstrated to share a receptor, CXCR3. The genes for both MuMig and Crg-2 are highly expressed in multiple tissues dur- ing experimental viral and protozoan infections in mice, but their patterns of expression differ. This suggests that the Migs and IP-1O/Crg-2 may play roles in host defense and that, despite their similar activities assayed in vitro, Mig and W-1O/Crg-2 may serve non-redundant functions in vivo. J. Leukoc. Biol. 61: 246-257; 1997.
793 citations
TL;DR: The selective expression and regulation of the IL-12R β2 subunit may help to understand the basis of Th1/Th2 differentiation and may provide therapeutic options for altering the Th1-Th2 balance in several immuno-pathological conditions such as autoimmune diseases and allergies.
Abstract: Interleukin-12 (IL-12), a heterodimeric cytokine produced by activated monocytes and dendritic cells, plays a crucial role in regulating interferon (IFN)-γ production and in the generation of IFN–γ–producing T helper 1 (Th1) cells. Here we show that the IL-12 receptor (IL12R) β2 subunit, a recently cloned binding and signal transducing component of the IL-12R, is expressed on human Th1 but not Th2 clones and is induced during differentiation of human naive cells along the Th1 but not the Th2 pathway. IL-12 and type I but not type II interferons induce expression of the IL-12R β2 chain during in vitro T cell differentiation after antigen receptor triggering. The selective expression and regulation of the IL-12R β2 subunit may help to understand the basis of Th1/Th2 differentiation and may provide therapeutic options for altering the Th1/Th2 balance in several immuno-pathological conditions such as autoimmune diseases and allergies.
757 citations
TL;DR: The possibility that PKR may function as a tumor suppressor and inducer of apoptosis suggests that this IFN-regulated protein kinase may be of central importance to the control of cell proliferation and transformation.
Abstract: This review describes the structure and function of the interferon (IFN)-inducible, double-stranded RNA-activated protein kinase PKR. This protein kinase has been studied extensively in recent years, and a large body of evidence has accumulated concerning its expression, interaction with regulatory RNA and protein molecules, and modes of activation and inhibition. PKR has been shown to play a variety of important roles in the regulation of translation, transcription, and signal transduction pathways through its ability to phosphorlate protein synthesis initiation factor eIF2, I-kB (the inhibitor of NF-kB), and other substrates. Expression studies involving both the wild-type protein and dominant negative mutants of PKR have established roles for the enzyme in the antiviral effects of IFNs, in the responses of uninfected cells to physiologic stresses, and in cell growth regulation. The possibility that PKR may function as a tumor suppressor and inducer of apoptosis suggests that this IFN-regulated protein ...
632 citations
TL;DR: The results suggest that both interferon action and apoptosis can be controlled at the level of RNA stability by RNase L, and that the 2‐5A system is likely to contribute to the antiviral activity ofinterferon by inducing apoptosis of infected cells.
Abstract: 2',5'-Oligoadenylate-dependent RNase L functions in the interferon-inducible, RNA decay pathway known as the 2-5A system. To determine the physiological roles of the 2-5A system, mice were generated with a targeted disruption of the RNase L gene. The antiviral effect of interferon alpha was impaired in RNase L-/- mice providing the first evidence that the 2-5A system functions as an antiviral pathway in animals. In addition, remarkably enlarged thymuses in the RNase L-/- mice resulted from a suppression of apoptosis. There was a 2-fold decrease in apoptosis in vivo in the thymuses and spleens of RNase L-/- mice. Furthermore, apoptosis was substantially suppressed in RNase L-/- thymocytes and fibroblasts treated with different apoptotic agents. These results suggest that both interferon action and apoptosis can be controlled at the level of RNA stability by RNase L. Another implication is that the 2-5A system is likely to contribute to the antiviral activity of interferon by inducing apoptosis of infected cells.
541 citations
TL;DR: Antibody‐neutralization studies further revealed that the anti‐tumor cytokines in the PSG‐MNC‐CM were mainly of TNF‐α and IFN‐γ, and these 2 cytokines acted synergistically on the inhibition of leukemic‐cell growth.
Abstract: The present study was to ascertain the immunomodulating and anti-tumor effects of Ganoderma (G.) lucidum. Polysaccharides (PS) from fresh fruiting bodies of G. lucidum (PS-G) were isolated and used to potentiate cytokine production by human monocytes-macrophages and T lymphocytes. Our results had shown that the levels of interleukin (IL)-1 beta, tumor necrosis factor (TNF)- alpha, and IL-6 in macrophage cultures treated with PS-G (100 micrograms/ml) were 5.1-, 9.8- and 29-fold higher, respectively, than those of untreated controls. In addition, the release of interferon (IFN)- gamma from T lymphocytes was also greatly promoted in the presence of PS-G (25-100 micrograms/ml). Furthermore, these cytokine-containing mononuclear cell-conditioned media (PSG-MNC-CM) were found to suppress the proliferation and clonogenicity of both the HL-60 and the U937 leukemic cell lines. DNA labeling and gel electrophoresis showed that treatment with PSG-MNC-CM markedly induced leukemic-cell apoptosis. Flow-cytometric analysis revealed that few (2.3 +/- 0.8%) apoptotic cells were seen in the control cultures, while PSG-MNC-CM treatment resulted in a significant increase in the apoptotic population both in the HL-60 (38.3 +/- 4.5%) and in the U937 (44.5 +/- 3.8%) cells. In addition, 40 to 45% of the treated leukemic cells were triggered to differentiate into mature monocytic cells expressing CD14 and CD68 surface antigens. However, PS-G alone had no such effects even at a higher dose of 400 micrograms/ml. Since untreated macrophages and T lymphocytes produced little or no cytokine, and normal MNC-CM did not suppress leukemic cell growth, it was suggestive that the anti-tumor activity of PSG-MNC-CM was derived from the elevated levels of cytokines. Antibody-neutralization studies further revealed that the anti-tumor cytokines in the PSG-MNC-CM were mainly of TNF- alpha and IFN- gamma, and these 2 cytokines acted synergistically on the inhibition of leukemic-cell growth.
446 citations
TL;DR: It is suggested that the host requires tight control of NK cells under these conditions, and endogenous IFN-alpha/beta is responsible for the lack of IL-12 during viral infections that fail to elicit detectable production of this factor.
TL;DR: It is reported that mouse embryo fibroblasts from mutant mice containing homozygous deletions in the PKR gene (Pkr(0/0) mice) were resistant to apoptotic cell death in response to double-stranded RNA, tumor necrosis factor-alpha, or lipopolysaccharide.
Abstract: Apoptosis occurs in response to different cellular stresses, including viral infection, inflammatory cytokines, growth factor deprivation, and UV light, but it is unclear whether these inducers share a common mechanism of induction. The interferon-induced, double-stranded RNA-activated protein kinase (PKR) has been implicated in processes that rely on apoptosis as control mechanisms in vivo, including antiviral activities, cell growth regulation, and tumorigenesis. Here we report that mouse embryo fibroblasts from mutant mice containing homozygous deletions in the PKR gene (Pkro/o mice) were resistant to apoptotic cell death in response to double-stranded RNA, tumor necrosis factor-α, or lipopolysaccharide. The mechanism underlying the suppression of apoptosis in the Pkro/o cells could be attributed to defects in the activation of DNA-binding activity for the transcription factor interferon regulatory factor-1 and in Fas mRNA induction. Thus, these results provide genetic evidence implicating a requirement for PKR in mediating different forms of stress-related apoptosis.
TL;DR: Interferon has important immunomodulatory properties, and treatment can induce autoimmune phenomena, the most frequent being autoimmune thyroiditis with either hypothyroidism or hyperthyroidism, especially in predisposed patients.
TL;DR: The ability of mice to control infection at sites distant to the site of vaccination suggests that systemic protection was achieved by LACK DNA vaccination, and DNA immunization may offer an attractive alternative vaccination strategy against intracellular pathogens, as compared with conventional vaccination with antigens combined with adjuvants.
Abstract: To determine whether DNA immunization could elicit protective immunity to Leishmania major in susceptible BALB/c mice, cDNA for the cloned Leishmania antigen LACK was inserted into a euykaryotic expression vector downstream to the cytomegalovirus promoter. Susceptible BALB/c mice were then vaccinated subcutaneously with LACK DNA and challenged with L. major promastigotes. We compared the protective efficacy of LACK DNA vaccination with that of recombinant LACK protein in the presence or absence of recombinant interleukin (rIL)-12 protein. Protection induced by LACK DNA was similar to that achieved by LACK protein and rIL-12, but superior to LACK protein without rIL-12. The immunity conferred by LACK DNA was durable insofar as mice challenged 5 wk after vaccination were still protected, and the infection was controlled for at least 20 wk after challenge. In addition, the ability of mice to control infection at sites distant to the site of vaccination suggests that systemic protection was achieved by LACK DNA vaccination. The control of disease progression and parasitic burden in mice vaccinated with LACK DNA was associated with enhancement of antigen-specific interferon-γ (IFN-γ) production. Moreover, both the enhancement of IFN-γ production and the protective immune response induced by LACK DNA vaccination was IL-12 dependent. Unexpectedly, depletion of CD8+ T cells at the time of vaccination or infection also abolished the protective response induced by LACK DNA vaccination, suggesting a role for CD8+ T cells in DNA vaccine induced protection to L. major. Thus, DNA immunization may offer an attractive alternative vaccination strategy against intracellular pathogens, as compared with conventional vaccination with antigens combined with adjuvants.
TL;DR: This study suggests that vIRF is a transforming oncogene active in B cell neoplasias that may provide a unique immune escape mechanism for infected cells, consistent with tumor suppressor pathways serving a dual function as host cell antiviral pathways.
Abstract: Kaposi's sarcoma-associated herpesvirus (KSHV) is a gammaherpesvirus linked to the development of Kaposi's sarcoma and a rare B cell lymphoma, primary effusion lymphoma. The KSHV gene ORF K9 encodes vIRF which is a protein with low but significant homology to members of the interferon (IFN) regulatory factor (IRF) family responsible for regulating intracellular interferon signal transduction (Moore PS, Boshoff C, Weiss RA and Chang Y. (1996). Science, 274, 1739-1744). vIRF inhibits IFN-beta signal transduction as measured using an IFN-responsive ISG54 reporter construct co-transfected with ORF K9 into HeLa and 293 cells. vIRF also suppresses genes under IFN regulatory control as shown by inhibition of the IFN-beta inducibility of p21WAF1/CIP1, however, no direct DNA-binding or protein-protein interactions characteristic for IRF repressor proteins were identified. Stable transfectant NIH3T3 clones expressing vIRF grew in soft agar and at low serum concentrations, lost contact inhibition and formed tumors after injection into nude mice indicating that vIRF has the properties of a viral oncogene. Since vIRF is primarily expressed in KSHV-infected B cells, not KS spindle cells, this study suggests that vIRF is a transforming oncogene active in B cell neoplasias that may provide a unique immune escape mechanism for infected cells. This data is consistent with tumor suppressor pathways serving a dual function as host cell antiviral pathways.
TL;DR: In embryo fibroblasts derived from Pkr°/° mice, interferon regulatory factor 1 (IRF‐1) or guanylate binding protein (Gbp) promoter–reporter constructs were unresponsive to IFN‐γ or pIC but response could be restored by co‐transfection with PKR.
Abstract: The interferon (IFN)-induced double-stranded RNA (dsRNA)-activated Ser/Thr protein kinase (PKR) plays a role in the antiviral and antiproliferative effects of IFN. PKR phosphorylates initiation factor eIF2alpha, thereby inhibiting protein synthesis, and also activates the transcription factor, nuclear factor-kappaB (NF-kappaB), by phosphorylating the inhibitor of NF-kappaB, IkappaB. Mice devoid of functional PKR (Pkr(o/o)) derived by targeted gene disruption exhibit a diminished response to IFN-gamma and poly(rI:rC) (pIC). In embryo fibroblasts derived from Pkr(o/o) mice, interferon regulatory factor 1 (IRF-1) or guanylate binding protein (Gbp) promoter-reporter constructs were unresponsive to IFN-gamma or pIC but response could be restored by co-transfection with PKR. The lack of responsiveness could be attributed to a diminished activation of IRF-1 and/or NF-kappaB in response to IFN-gamma or pIC. Thus, PKR acts as a signal transducer for IFN-stimulated genes dependent on the transcription factors IRF-1 and NF-kappaB.
TL;DR: The current knowledge of IP-10 and its homologues are highlighted as well as defining its likely involvement in regulating fibroproliferation following inflammatory lung injury.
TL;DR: It is shown that, under in vivo conditions, LPS also induces strong stimulation of T cells, implying a common mechanism that intermittent exposure to pathogens could contribute to the high background proliferation of memory–phenotype CD8+ cells found in normal animals.
Abstract: Lipopolysaccharide (LPS) from gram-negative bacteria causes polyclonal activation of B cells and stimulation of macrophages and other APC. We show here that, under in vivo conditions, LPS also induces strong stimulation of T cells. As manifested by CD69 upregulation, LPS injection stimulates both CD4 and CD8+ T cells, and, at high doses, stimulates naive (CD44lo) cells as well as memory (CD44hi) cells. However, in terms of cell division, the response of T cells after LPS injection is limited to the CD44hi subset of CD8+ cells. In contrast with B cells, proliferative responses of CD44hi CD8+ cells require only very low doses of LPS (10 ng). Based on studies with LPS-nonresponder and gene-knockout mice, LPS-induced proliferation of CD44hi CD8+ cells appears to operate via an indirect pathway involving LPS stimulation of APC and release of type I (α, β) interferon (IFN-I). Similar selective stimulation of CD44hi CD8+ cells occurs in viral infections and after injection of IFN-I, implying a common mechanism. Hence, intermittent exposure to pathogens (gram-negative bacteria and viruses) could contribute to the high background proliferation of memory–phenotype CD8+ cells found in normal animals.
TL;DR: Clinical and virological features are associated with higher response rates to interferon treatment, and although pretreatment factors do not accurately predict treatment outcome in individuals, they may be helpful in counseling patients and making treatment decisions.
TL;DR: The data indicate that the cytokines interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) inhibit transgene expression from certain widely used viral promoters/enhancers delivered by adenoviral, retroviral or plasmid vectors in vitro.
Abstract: One of the major limitations to current gene therapy is the low-level and transient vector gene expression due to poorly defined mechanisms, possibly including promoter attenuation or extinction. Because the application of gene therapy vectors in vivo induces cytokine production through specific or nonspecific immune responses, we hypothesized that cytokine-mediated signals may alter vector gene expression. Our data indicate that the cytokines interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) inhibit transgene expression from certain widely used viral promoters/enhancers (cytomegalovirus, Rous sarcoma virus, simian virus 40, Moloney murine leukemia virus long terminal repeat) delivered by adenoviral, retroviral or plasmid vectors in vitro. A constitutive cellular promoter (β-actin) is less sensitive to these cytokine effects. Inhibition is at the mRNA level and cytokines do not cause vector DNA degradation, inhibit total cellular protein synthesis, or kill infected/transfected cells. Admin...
TL;DR: The different cytokine profiles of T cells within the liver in chronic HBV and HCV infections illustrate a different behavior of the local immune response in these two infections that may have pathogenetic implications.
TL;DR: It is concluded that human cytomegalovirus induces interferon-responsive mRNAs, which accumulate after infection with virus that has been inactivated by treatment with UV light, indicating that the inducer is present in virions.
Abstract: We used differential display analysis to identify mRNAs that accumulate to enhanced levels in human cytomegalovirus-infected cells as compared with mock-infected cells. RNAs were compared at 8 hr after infection of primary human fibroblasts. Fifty-seven partial cDNA clones were isolated, representing about 26 differentially expressed mRNAs. Eleven of the mRNAs were virus-coded, and 15 were of cellular origin. Six of the partial cDNA sequences have not been reported previously. All of the cellular mRNAs identified in the screen are induced by interferon α. The induction in virus-infected cells, however, does not involve the action of interferon or other small signaling molecules. Neutralizing antibodies that block virus infection also block the induction. These RNAs accumulate after infection with virus that has been inactivated by treatment with UV light, indicating that the inducer is present in virions. We conclude that human cytomegalovirus induces interferon-responsive mRNAs.
TL;DR: Results demonstrate a new pathway for regulating cytokine responses, and suggest a mechanism for inhibition of IL-12-dependent immune responses during viral infections.
Abstract: Interferon (IFN)-α/β-mediated negative regulation of interleukin 12 (IL-12) and IFN-γ proteins is reported here. Both IFN-α and IFN-β inhibited fixed Staphylococcus aureus Cowan strain induction of IL-12 and IFN-γ production by mouse splenic leukocytes in culture. Extended studies with IFN-α demonstrated that inhibition was at the level of biologically active IL-12 p70. Effects were selective, as induction of tumor necrosis factor was unaffected and induction of IL-6 was enhanced. Neutralization of IFN-α/β expressed endogenously during infections with murine cytomegalovirus (MCMV) enhanced early IL-12 and IFN-γ protein production. Furthermore, during infections of mice with lymphocytic choriomeningitis virus (LCMV), this treatment revealed a previously undetected early IL-12 and IFN-γ protein expression, and mice deficient in IFN-α/β receptor function, but not control mice, also expressed endogenous LCMV-induced IL-12. The effects of IFN-α/β neutralization on production of IL-12 and IFN-γ during the viral infections were detected in both serum samples and medium conditioned with splenic leukocytes isolated from infected animals. In vitro studies demonstrated that splenic leukocytes isolated from LCMV-infected mice were primed to produce IL-12 in response to stimulation with Staphylococcus aureus Cowan strain, but that this responsiveness was sensitive to added IFN-α. Moreover, endogenous IFN-α/β induced by LCMV inhibited in vivo lipopolysaccharide stimulation of IL-12 production. These results demonstrate a new pathway for regulating cytokine responses, and suggest a mechanism for inhibition of IL-12-dependent immune responses during viral infections.
TL;DR: It is shown that CD4+ T cells from Leishmania-infected mice lacking one (+/-) or both (-/-) alleles of the IRF-1 gene developed a profound, gene dose-dependent decrease in IFNgamma production, which is a determining factor for Th1 responses.
TL;DR: Transfection analyses and data collectively support the conclusion that binding of Stat1α to the iNOS promoter's GAS is required for optimal induction of theiNOS gene by IFN-γ and LPS.
TL;DR: The decreased percentage of cells expressing IL-2 and IFN-γ in conjunction with an increased proportion of IL-4- and IL-10-producing cells among the CD4+ T cells in HIV-1-infected individuals demonstrate a Th1 to Th2 cytokine shift in the course of HIV infection on a single cell level.
Abstract: Objective To characterize changes of Th1/Th2 cytokine production by peripheral blood mononuclear cells (PBMC) that occur during the course of HIV infection by cytoplasmic cytokine staining on single cell level. Design and methods Mitogen-stimulated PBMC from 16 healthy donors, 18 HIV-1-infected individuals without AIDS and 14 patients with AIDS were stained intracellularly with fluorescein-labelled MAb against interleukin (IL)-2, IL-4, IL-10 and interferon (IFN)-gamma. Additionally, co-staining of CD4+ T-cell, CD8+ T-cell, natural killer (NK) cell, B-cell and monocytic markers was performed. Fluorescence staining was analysed by three-colour flow-cytometry. Results A reduced percentage of IL-2 and IFN-gamma (Th1 type)-producing cells among CD4+ T cells from HIV-1-infected individuals could be demonstrated. There was a continuous decrease of IFN-gamma-producing CD4+ T cells in the course of HIV infection and a dramatic reduction of IL-2-expressing cells among CD4+ T cells in patients with AIDS. In contrast to Th1 cytokines, the frequency of Th2 cytokine expressing cells among CD4+ T cells increased in HIV-infected individuals. The maximum frequency of IL-4-expressing cells among CD4+ T cells was seen in HIV-infected individuals without AIDS, whereas the rate of IL-10-producing cells was highest in patients with AIDS. In HIV-infected individuals no significant proportion of Th0 cells expressing both Th1 and Th2 cytokines was detectable. In CD8+ T cells the percentage of IL-2 was expressing cells decreased continuously accompanied by a strong increase of the frequency of IFN-gamma-producing cells. Conclusion The decreased percentage of cells expressing IL-2 and IFN-gamma in conjunction with an increased proportion of IL-4- and IL-10-producing cells among the CD4+ T cells in HIV-1-infected individuals demonstrate a Th1 to Th2 cytokine shift in the course of HIV infection on a single cell level. There was no evidence of a Th1 to Th0 cytokine shift. In addition to the loss of CD4+ T cells in HIV infection, the qualitative changes of Th1/Th2 cytokine expression may serve as a marker for progressive failure of cell-mediated immunity.
TL;DR: It is proposed that IFN-γ modulates a p53-independent apoptotic pathway by both directly and indirectly inducing select apoptosis-related genes.
TL;DR: Increased RNase L levels induced apoptosis and inhibition ofRNase L activity blocked viral-induced apoptosis, suggesting that apoptosis may be one of the antiviral mechanisms regulated by the 2–5A system.
Abstract: The 2-5A system contributes to the antiviral effect of interferons through the synthesis of 2-5A and its activation of the ribonuclease, RNase L. RNase L degrades viral and cellular RNA after activation by unique, 2'-5' phosphodiester-linked, oligoadenylates [2-5A, (pp)p5' A2'(P5'A2')]n, n >=2. Because both the 2-5A system and apoptosis can serve as viral defense mechanisms and RNA degradation occurs during both processes, we investigated the potential role of RNase L in apoptosis. Overexpression of human RNase L by an inducible promoter in NIH3T3 fibroblasts decreased cell viability and triggered apoptosis. Activation of endogenous RNase L, specifically with 2-5A or with dsRNA, induced apoptosis. Inhibition of RNase L with a dominant negative mutant suppressed poly (I).poly (C)-induced apoptosis in interferon-primed fibroblasts. Moreover, inhibition of RNase L suppressed apoptosis induced by poliovirus. Thus, increased RNase L levels induced apoptosis and inhibition of RNase L activity blocked viral-induced apoptosis. Apoptosis may be one of the antiviral mechanisms regulated by the 2-5A system.
TL;DR: The expression of IRf-7 is consistently high in type III latency cells and almost undetectable in type I latency, corresponding to the activity of endogenous Qp in these latency states and the ability of the IRF-7 proteins to repress Qp-reporter constructs.
Abstract: The Epstein-Barr virus (EBV) BamHI Q promoter (Qp) is the only promoter used for the transcription of Epstein-Barr virus nuclear antigen 1 (EBNA-1) mRNA in cells in the most restricted (type I) latent infection state However, Qp is inactive in type III latency With the use of the yeast one-hybrid system, a new cellular gene has been identified that encodes proteins which bind to sequence in Qp The deduced amino acid sequence of the gene has significant homology to the interferon regulatory factors (IRFs) This new gene and products including two splicing variants are designated IRF-7A, IRF-7B, and IRF-7C The expression of IRF-7 is predominantly in spleen, thymus, and peripheral blood leukocytes (PBL) IRF-7 proteins were identified in primary PBL with specific antiserum against IRF-7B protein IRF-7s can bind to interferon-stimulated response element (ISRE) sequence and repress transcriptional activation by both interferon and IRF-1 Additionally, a functional viral ISRE sequence, 5'-GCGAAAACGAAAGT-3', has been identified in Qp Finally, the expression of IRF-7 is consistently high in type III latency cells and almost undetectable in type I latency, corresponding to the activity of endogenous Qp in these latency states and the ability of the IRF-7 proteins to repress Qp-reporter constructs The identification of a functional viral ISRE and association of IRF-7 with type III latency may be relevant to the mechanism of regulation of Qp
TL;DR: The selective expression and regulation of the IL-12R β2 subunit may help to understand the basis of Th1/Th2 differentiation and may provide therapeutic options for altering the Th1-Th2 balance in several immuno-pathological conditions such as autoimmune diseases and allergies.