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PubMed1996

Transcriptionally active Stat1 is required for the antiproliferative effects of both interferon alpha and interferon gamma.

Type I (alpha, beta) and type II (gamma) interferons (IFNs) can restrict the growth of many cell types. INF-stimulated gene transcription, a key early event in IFN response, acts through the Janus kinase-signal transducers and activators of transcription pathway, in which both IFN-alpha and IFN-gamma activate the transcription factor Stat1. A cell line lacking Stat1 (U3A) was not growth-arrested by IFN-alpha or IFN-gamma, and experiments were carried out with U3A cells permanently expressing normal or various mutant forms of Stat1 protein. Only cells in which complete Stat1 activity was available (Stat1alpha) were growth-inhibited by IFN-gamma. A mutant that supports 20-30% normal transcription did not cause growth restraint. In contrast, IFN-alpha growth restraint was imposed by cells producing Stat1beta, which lacks transcriptional activation potential. This parallels earlier results showing the truncated Stat1 can function in IFN-alpha gene activation. In addition to experiments on long-term cultured cells, we also found that wild-type primary mouse embryonic fibroblasts were inhibited by IFNs, but fibroblasts from Stat1-deficient mouse embryos were not inhibited by IFNs.

Animals↗

PubMed1997

Interferon-alpha/beta inhibition of interleukin 12 and interferon-gamma production in vitro and endogenously during viral infection.

Interferon (IFN)-alpha/beta-mediated negative regulation of interleukin 12 (IL-12) and IFN-gamma proteins is reported here. Both IFN-alpha and IFN-beta inhibited fixed Staphylococcus aureus Cowan strain induction of IL-12 and IFN-gamma production by mouse splenic leukocytes in culture. Extended studies with IFN-alpha 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-alpha/beta expressed endogenously during infections with murine cytomegalovirus (MCMV) enhanced early IL-12 and IFN-gamma protein production. Furthermore, during infections of mice with lymphocytic choriomeningitis virus (LCMV), this treatment revealed a previously undetected early IL-12 and IFN-gamma protein expression, and mice deficient in IFN-alpha/beta receptor function, but not control mice, also expressed endogenous LCMV-induced IL-12. The effects of IFN-alpha/beta neutralization on production of IL-12 and IFN-gamma 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-alpha. Moreover, endogenous IFN-alpha/beta 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.

Animals↗

PubMed1995

Triggering of the human interleukin-6 gene by interferon-gamma and tumor necrosis factor-alpha in monocytic cells involves cooperation between interferon regulatory factor-1, NF kappa B, and Sp1 transcription factors.

We investigated the molecular basis of the synergistic induction by interferon-gamma (IFN-gamma)/tumor necrosis factor-alpha (TNF-alpha) of human interleukin-6 (IL-6) gene in THP-1 monocytic cells, and compared it with the basis of this induction by lipopolysaccharide (LPS). Functional studies with IL-6 promoter demonstrated that three regions are the targets of the IFN-gamma and/or TNF-alpha action, whereas only one of these regions seemed to be implicated in LPS activation. The three regions concerned are: 1) a region between -73 and -36, which is the minimal element inducible by LPS or TNF-alpha; 2) an element located between -181 and -73, which appeared to regulate the response to IFN-gamma and TNF-alpha negatively; and 3) a distal element upstream of -224, which was inducible by IFN-gamma alone. LPS signaling was found to involve NF kappa B activation by the p50/p65 heterodimers. Synergistic induction of the IL-6 gene by IFN-gamma and TNF-alpha, in monocytic cells, involved cooperation between the IRF-1 and NF kappa B p65 homodimers with concomitant removal of the negative effect of the retinoblastoma control element present in the IL-6 promoter. This removal occurred by activation of the constitutive Sp1 factor, whose increased binding activity and phosphorylation were mediated by IFN-gamma.

Base Sequence↗

PubMed1998

Characterization of the interferon regulatory factor-7 and its potential role in the transcription activation of interferon A genes.

The family of interferon regulatory factors (IRFs) plays an important role in modulating cellular responses to viral infection and cytokines, including IFNs. The transcription factors that are involved in the transcriptional activation of the IFNB gene have been extensively studied. However, the molecular mechanism by which virus activates the expression of the IFNA gene remains to be defined. Recently, we have identified a new IRF-7 isoform, denoted as IRF-7H, which encodes a protein of 514 amino acids and is most closely related to the IRF-3. The expression of IRF-7 is restricted to the lymphoid cell types and is inducible by virus, lipopolysaccharide, and IFNA. The functional characterization of IRF-7H reveals a presence of transactivation domain located carboxyl-terminal to its DNA binding domain. Overexpression of IRF-7H results in an activation of IFNA promoter in transient transfection assay and a strong enhancement of virus-mediated activation of this promoter. Whereas in uninfected cells, overexpressed IRF-7H is present mainly in the cytoplasm, viral infection facilitates the transfer of IRF-7H to the nucleus; overexpression of IRF-3 interferes with the virus-induced translocation of IRF-7H. Thus, IRF-7 exhibits functional similarity to IRF-3; however, the preferential expression of IRF-7 in lymphoid cells (the cell type that expresses IFNA) suggests that IRF-7 may play a critical role in regulating the IFNA gene expression.

Alternative Splicing↗

PubMed2004

Interferon-gamma acts proapoptotic on hepatic stellate cells (HSC) and abrogates the antiapoptotic effect of interferon-alpha by an HSP70-dependant pathway.

The activated hepatic stellate cell (HSC) is an important fibrogenic cell type of the liver. Interferon-alpha (IFN-alpha) has recently been shown to elicit an antiapoptotic effect on activated HSC by a JAK-2-dependent inhibition of caspase-8 activation. As JAK-2 has so far been shown to be a member of the IFN-gamma signal transduction pathway we studied the effect of IFN-gamma on apoptosis as well as on its signaling in primary cultured rat HSC. IFN-gamma elicited a proapoptotic effect in activated HSC. The combination of both, IFN-gamma and IFN-alpha, however, completely cancelled each other's effect. No effect of the two cytokines on major members of apoptosis-regulating systems (CD95, CD95L, bcl-2, bax, bcl-xL, p53, p21WAF1, p27, NFkappaB) could be observed. Western Blot analysis revealed that gene expression of the chaperone HSP70 was found to be downregulated by IFN-gamma but upregulated by IFN-alpha. The effect could be abrogated by administration of both. After transfection of activated HSC with a pCMV-HSP70 M expression vector the proapoptotic effect of IFN-gamma was cancelled. Using HSP70 antisense, the antiapoptotic effect of IFN-alpha was cancelled as well. However IFN-gamma had no effect on upregulation of JAK-2 and pJAK-2 by IFN-alpha. Taken together IFN-gamma and IFN-alpha exert opposite effects on apoptosis in HSC. This effect is mediated by their counteracting effect on HSP70 expression which acts antiapoptotic at the level of caspase-8.

Animals↗

PubMed2005

Long-term follow-up of interferon monotherapy in 454 consecutive naive patients infected with hepatitis C virus: multi-course interferon therapy may reduce the risk of hepatocellular carcinoma and increase survival.

OBJECTIVE: The long-term effects of multi-course interferon (IFN) monotherapy in patients infected with hepatitis C virus (HCV) are still unclear. MATERIAL AND METHODS: To evaluate the effects of multi-course IFN on hepatocarcinogenesis and survival, a follow-up study was conducted comprising 454 consecutively recruited non-cirrhotic naive patients infected with HCV, who had received IFN monotherapy between 1987 and 1992. The median follow-up was 11.3 years. RESULTS: A sustained response (SR) after the first IFN was achieved by 152 patients (33.5%) (Group A). Of 302 patients (66.5%) with non-SR after the first IFN, 130 patients (28.6%) did not receive additional IFN (Group B), and the remaining 172 patients (37.9%) received multi-course IFN monotherapy (Group C). With regard to hepatocarcinogenesis and survival rates for liver-related deaths, Groups A and C both showed significantly better long-term clinical outcome than Group B (p < 0.001; log-rank test). Three independent factors were identified by multivariate analyses (fibrosis stage 3, Group B, and age > or = 50) for all patients and two factors (fibrosis stage 3 and age > or = 50) for Group C associated with hepatocarcinogenesis. With regard to hepatocarcinogenesis rates according to the mean alanine aminotransferase (ALAT) levels during the IFN-free period in Group C, significantly higher rates were noted in patients with ALAT levels above 1.5 x the upper normal limit (17.6%) than those below the limit (0%) (p < 0.05). CONCLUSIONS: Multi-course IFN monotherapy reduces the risk of hepatocarcinogenesis and increases survival, and low ALAT levels during the IFN-free period are associated with lower hepatocarcinogenesis rates in multi-course IFN.

Adolescent↗

PubMed1965

LEUKOCYTES AND INTERFERON IN THE HOST RESPONSE TO VIRAL INFECTIONS. I. MOUSE LEUKOCYTES AND LEUKOCYTE-PRODUCED INTERFERON IN VACCINIA VIRUS INFECTION IN VITRO.

1. Investigation of the role of leukocytes in vaccinia virus infection is reported in an in vitro model, in the absence of an immune response. 2. Mouse leukocytes were shown to be capable of inhibiting the progression of vaccinia virus infection in primary mouse embryo fibroblast cultures. The degree of protection varied from slowing of spread of infection to complete control of the infection with eventual elimination of detectable virus and recovery of the culture. 3. Interferon production by leukocytes is thought to be an important factor in the observed protective effect.

Chick Embryo↗

PubMed1993

Interferon alpha increases the frequency of interferon gamma-producing human CD4+ T cells.

An increased ratio of T helper type 2 (Th2)- vs Th1-like cells contributes to the immune dysregulation in allergic disease situations and in many chronic infections, including AIDS. Th2-type immune responses are characterized by Th cells that produce increased levels of interleukin-4 (IL-4) and decreased levels of interferon gamma (IFN-gamma). The induction of either a Th1- or a Th2-like phenotype may be critically controlled by the antigen-presenting cells and their cytokines, e.g., IFN-alpha. In this study we have determined the frequencies of potential IL-4- and/or IFN-gamma-producing T cells in the peripheral blood of randomly selected healthy individuals, and analyzed whether IFN-alpha controls IL-4 and/or IFN-gamma production. Purified CD4+ or CD8+ T cells were stimulated for 24 h via the T cell receptor/CD3 complex in the presence or absence of IFN-alpha, and single IL-4- and IFN-gamma-secreting cells were detected in enzyme-linked immunospot assays. In the absence of IFN-alpha, CD4 cells produced IFN-gamma at frequencies of 1:50-300, and produced IL-4 at frequencies of 1:110-<1:100,000. Addition of IFN-alpha during the activation of CD4 cells increased the levels of IFN-gamma mRNA. As a consequence, the numbers of IFN-gamma-producing CD4 cells and the amounts of secreted IFN-gamma increased 10-fold. In contrast, IFN-alpha did not increase the frequency of IL-4-secreting CD4 cells. In the absence of IFN-alpha, addition of exogenous IL-4 to cultures of CD4 cells suppressed IFN-gamma secretion by 70%. However, in the presence of IFN-alpha, IL-4 did not display any suppressive effect. Compared with CD4 cells, CD8 cells produced IFN-gamma more frequently (1:5-10) but IL-4 less frequently (1:5,300 to < 1:100,000). IFN-alpha did not display any effect on the frequency of either IFN-gamma or IL-4 production by CD8 cells. Taken together the results indicate that IFN-alpha increases the frequency of IFN-gamma-secreting CD4 Th cells and antagonizes the suppressive effect of IL-4 on IFN-gamma production. As a consequence, IFN-alpha may favor the induction and maintenance of Th1-like cells and thereby counteract Th2-driven allergic immune responses.

Acquired Immunodeficiency Syndrome↗

PubMed1995

Interferon beta, a cofactor in the interferon gamma production induced by gram-negative bacteria in mice.

The interferon (IFN) gamma production of splenocytes from closely related C57BL/10ScSn (Sn) and C57BL/10ScCr (Cr) mice was compared. Concanavalin A and CD3 monoclonal antibodies induced high levels of IFN-gamma in both Sn and Cr splenocytes. By contrast, treatment with gram-negative bacteria induced IFN-gamma only in Sn splenocytes; in Cr splenocytes, the IFN-gamma response was heavily impaired. The IFN-gamma induction by bacteria requires the cooperation of IFN-gamma-producing cells with macrophages. Depletion of macrophages from Sn splenocytes resulted in the loss of ability to produce IFN-gamma after bacterial stimulation. Reconstitution with new Sn macrophages restored the IFN-gamma responsiveness, whereas reconstitution with Cr macrophages failed to do so. Normal function of IFN-gamma-producing cells and a defective function of macrophages of Cr mice was demonstrated by evidence showing that whole or macrophage-depleted Cr splenocytes, when supplemented with Sn macrophages, acquire the ability to produce IFN-gamma in response to bacteria. A similar effect was achieved by supplementing Cr splenocytes with supernatants of bacteria-stimulated Sn macrophages or with recombinant murine IFN-beta or IFN-alpha. Preincubation of active macrophage supernatants with antibodies to IFN-beta suppressed the helper activity for Cr splenocytes. Moreover, the bacteria-induced production of IFN-gamma by Sn splenocytes could be inhibited by antibodies to murine IFN-beta. The results provide evidence that IFN-beta is an important cofactor of IFN-gamma induction, which is not induced in Cr mice by gram-negative bacteria.

Animals↗

PubMed1999

Two roads diverged: interferon alpha/beta- and interleukin 12-mediated pathways in promoting T cell interferon gamma responses during viral infection.

Viral infections induce CD8 T cell expansion and interferon (IFN)-gamma production for defense, but the innate cytokines shaping these responses have not been identified. Although interleukin (IL)-12 has the potential to contribute, IL-12-dependent T cell IFN-gamma has not been detected during viral infections. Moreover, certain viruses fail to induce IL-12, and elicit high levels of IFN-alpha/beta to negatively regulate it. The endogenous factors promoting virus-induced T cell IFN-gamma production were defined in studies evaluating CD8 T cell responses during lymphocytic choriomeningitis virus infections of mice. Two divergent supporting pathways were characterized. Under normal conditions of infections, the CD8 T cell IFN-gamma response was dependent on endogenous IFN-alpha/beta effects, but was IL-12 independent. In contrast, in the absence of IFN-alpha/beta functions, an IL-12 response was revealed and substituted an alternative pathway to IFN-gamma. IFN-alpha/beta-mediated effects resulted in enhanced, but the alternative pathway also promoted, resistance to infection. These observations define uniquely important IFN-alpha/beta-controlled pathways shaping T cell responses during viral infections, and demonstrate plasticity of immune responses in accessing divergent innate mechanisms to achieve similar ultimate goals.

Animals↗

PubMed2003

Comparison of 12-month courses of interferon-alpha-2b-lamivudine combination therapy and interferon-alpha-2b monotherapy among patients with untreated chronic hepatitis B.

We compared the use of prolonged synchronous combination therapy with interferon (IFN)-alpha-2b and lamivudine with the use of IFN-alpha-2b monotherapy in patients with untreated hepatitis B e antigen (HBeAg)-positive chronic hepatitis B virus (HBV) infection. Thirty-three patients received therapy with lamivudine (100 mg daily) and IFN-alpha-2b (10 million U 3 times per week) for 12 months; 16 patients received IFN-alpha-2b alone (10 million U 3 times per week for 12 months). The primary end point was sustained suppression of HBV DNA and HBeAg seroconversion, which was observed in 15 (45%) of 33 patients treated with combination therapy and in 3 (19%) of 16 patients treated with monotherapy (P=.133). Both therapeutic regimens were well tolerated. Combination therapy increased the rate of sustained suppression of HBeAg and resulted in significant improvement in Knodell histologic activity index scores, compared with monotherapy. However, there was no significant difference in rates of sustained suppression between the 2 groups at the end of follow-up.

Adolescent↗

PubMed2006

Identification of proteins immunologically related to interferon regulatory factor-1 that bind with interferon regulatory factor element.

Interferon regulatory factor (IRF)-1 expression was surveyed in nontransformed and oncogene-transformed mouse fibroblasts, using Western immunoblot with an IRF-1-specific antiserum, to examine possible differences resulting from cellular transformation. Ten additional proteins that reacted with the IRF-1 antibody and that underwent specific competition by peptide antigen were observed in extracts of both nontransformed and oncogene-transformed cell lines. Cross-reacting proteins were also observed in mouse macrophage extracts. Protein was captured from fibroblast nuclear extracts, using oligonucleotides representing IRF-binding sequences linked to magnetic beads. Captured proteins were eluted and analyzed by immunoblot with anti-IRF-1. Along with 43-kDa IRF-1, 4 of the 7 nuclearly located cross-reacting proteins (97, 90, 66, and 33 kDa) were found to complex with the IRF binding element. These proteins, with an epitope in common with the IRF-1 C-terminal region and IRF element DNA sequence-binding capability, may represent new members of the IRF family.

Animals↗

PubMed2000

Combined treatment with low-dose interferon plus vinblastine is associated with less toxicity than conventional interferon monotherapy in patients with metastatic renal cell carcinoma.

The outcome of treatment of advanced renal cell carcinoma is disappointing. In interferon (IFN)-treated patients, the high incidence of adverse effects causes many patients to withdraw from treatment. This 12-week randomized study compared the incidence of toxicity associated with high-dose IFN monotherapy (15 x 10(6) U thrice weekly) and treatment with the combination of low-dose IFN (5 x 10(6) U thrice weekly) and 6 mg/m2 vinblastine (VBL) every 14 days in 100 consecutive patients. There was no significant difference in response rate between treatment arms (42% IFN vs. 34% IFN + VBL) or between subgroups (by tumor location). Combined treatment was associated with a significantly lower incidence of fever, fatigue, and weight loss but with a higher incidence of leukopenia. There was no significant difference in the incidence of other events. More patients treated with IFN monotherapy required bed rest, and overall treatment costs were 60% higher than for combined treatment. It is concluded that combined treatment with low-dose IFN and VBL, without loss of short-term efficacy, is better tolerated and less expensive than high-dose IFN monotherapy.

Adult↗

PubMed2001

Combined sequential treatment with interferon and dsRNA abrogates virus resistance to interferon action.

Many viruses have evolved mechanisms to resist the action of interferon (IFN). These include production of viral gene products that sequester double-stranded RNA (dsRNA) and of small helical RNA. These potentially prevent activation of dsRNA-dependent pathways of IFN action or block expression of cellular genes activated exclusively by dsRNA that may contribute to the antiviral state. Thus, dsRNA might be rate limiting in the development of an IFN-mediated antiviral state. In support of this hypothesis, dsRNA added exogenously to IFN-treated cells in the form of poly(rI):poly(rC) is shown to establish in a dose-dependent manner an antiviral state against two viruses otherwise highly refractory to IFN action, avian reovirus (ARV) and Newcaste disease virus (NDV). Cells exposed singly to high doses of IFN or dsRNA reduced the plaque-forming capacity of these viruses on chicken embryo cells 2-fold. When used in combination, there was up to a 100-fold reduction. In order to abrogate IFN resistance, dsRNA must be added after, not before, an IFN-mediated latent antiviral state is established. dsRNA added exogenously is thought to achieve the threshold required for activation of dsRNA-dependent pathways of IFN action or to induce some dsRNA-stimulated gene whose product acts synergistically with that of some IFN-stimulated gene. The combined sequential treatment with IFN and dsRNA may be useful in overcoming the anti-IFN activity of viruses of clinical interest or in other clinical conditions.

Animals↗

PubMed2004

Potent inhibition of SARS-associated coronavirus (SCOV) infection and replication by type I interferons (IFN-alpha/beta) but not by type II interferon (IFN-gamma).

We sought to investigate the anti-severe acute respiratory syndrome (SARS)-associated coronavirus (SCoV) activities of type I (alpha and beta) and type II (gamma) interferons (IFN) in vitro. Type I IFNs protected cells from cytopathic effects (CPE) induced by SCoV, and inhibited viral genomic RNA replication in FRhk-4 cells (measured by quantitative RT-PCR) in a dose-dependent manner. Intracellular viral RNA copies were reduced 50% by IFN-alpha at a concentration of 25 U/ml and by IFN-beta at a concentration of 14 U/ml. IFN-gamma had fewer effects on inhibition of viral infection and replication. The type I IFN receptor signaling pathway in host cells is mainly involved in the inhibition of SCoV infection and replication. Type I IFNs could be used as potential agents for anti-SARS treatment.

Antiviral Agents↗

PubMed1985

Serum interferon level and (2'-5')oligoadenylate synthetase activity in lymphocytes during clinical interferon application.

Determinations of (2'-5')oligoadenylate synthetase (OAS) in extracts of peripheral mononuclear cells were used to monitor clinical treatment by human leukocyte-derived alpha-interferon (IFN-alpha). The maximum activity of this enzyme was detected about 6 h after the maximum IFN activity in the patient's serum, its half-life being severalfold longer than that of circulating IFN. Thus, even some days after its clearance, IFN can be detected by means of this enzyme. Sixfold increases of the IFN dose were not able to further increase OAS activity induced by doses of about 5 X 10(4) units/kg body weight in adult persons. Intravenous administration of IFN seems not to be superior to its i.m. injection.

2',5'-Oligoadenylate Synthetase↗

PubMed1986

Effects of recombinant human leukocyte interferon treatment of endogenous interferon production in patients with chronic type-B hepatitis.

Interferon (IFN) added to cell culture systems alters the capacity of the cells to produce IFN when appropriately stimulated. To evaluate the effects of in vivo administration of IFN on the production of IFN by peripheral blood mononuclear cells (PBMCs), we studied patients with chronic type-B hepatitis who received doses of recombinant human leukocyte (alpha) IFN (IFN-alpha) ranging from 5 X 10(6) units daily to 60 X 10(6) thrice weekly. The production of endogenous IFN stimulated by specific inducers (Sendai virus for IFN-alpha; phytohemagglutinin for IFN-gamma) was studied in cell cultures containing PBMCs obtained from patients before or during courses of IFN treatment. In untreated controls, no change in the mean capacity of PBMCs to produce IFN-alpha was noted after 2 weeks. Priming of endogenous IFN-alpha production, as reflected by earlier production of IFN by PBMCs in culture, occurred in all treated patients irrespective of the dose of IFN-alpha received. Whereas mean 24-hour (total) endogenous IFN-alpha fell in all treatment groups, the response was highly variable in individual patients and half showed no change in total production. Individual variations in endogenous IFN-alpha production were unrelated to serum IFN levels achieved during treatment, changes in serum aminotransferase levels, reduction of hepatitis B virus replication during therapy, or the proportions of T and B lymphocytes in culture. In contrast to the changes in IFN-alpha production, IFN-gamma production by PBMCs was not affected by IFN-alpha treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1986

Regulation of human gamma-interferon and beta-interferon gene expression in PHA-activated lymphocytes.

Two interferon (IFN) messengers were synthesized in phytohemagglutinin (PHA)-activated lymphocytes: IFN-gamma mRNA and a messenger hybridizing with the IFN-beta 2 probe. They were induced rapidly and declined at a stage when overall RNA was still efficiently transcribed. The IFN-beta 2 mRNA (15S) present in the lymphocytes was slightly different from its fibroblastic counterpart (14S). The kinetics of the accumulation and decay of both lymphocyte IFN messengers differed when assessed by hybridization with the two IFN probes, IFN-gamma mRNA was not detected before mitogenic activation and accumulated for up to 15 h postactivation, while IFN-beta 2 mRNA accumulated even in the absence of PHA activation for up to 5 h, even though the activation raised the IFN-beta 2 mRNA level at 5 h. The disappearance of IFN messengers was prevented when cycloheximide was added 5 h after PHA activation, when the transcription of both messengers had already been turned on, suggesting the presence of the repressor mechanism proposed for IFN-beta 1 and IFN-beta 2 mRNAs in fibroblasts. In the absence of PHA activation, cycloheximide did not induce IFN-beta 2 mRNA transcription as it did in fibroblasts and moreover prevented the accumulation of the messenger observed in the control cells. In contrast to IFN-beta 2 mRNA, cycloheximide treatment of lymphocytes produced a slight accumulation of IFN-gamma mRNA. This accumulation was already detectable 6 h posttreatment and its level remained unchanged for up to 24 h. Addition of actinomycin D, 5 h after PHA activation, did not impair the shut off and accelerated the decay of IFN messengers.

Cells, Cultured↗