Showing papers on "Interferon published in 1984"

Secretory products of macrophages and their physiological functions

Abstract: Macrophages secrete a variety of biologically active substances into their local milieu, including proteins, lipids, nucleotide metabolites, and oxygen metabolites. To date, more than 50 substances secreted by macrophages have been reported: enzymes; enzyme inhibitors; plasma proteins such as complement components, coagulation factors, and apolipoprotein E; factors that regulate the functions of other cells such as interferon, interleukin 1, mitogens, and angiogenesis factor; and low molecular weight substances such as reactive metabolites of oxygen and derivatives of arachidonic acids. Macrophage-derived products are probably important in the local environment, and they are believed to be important in the physiological and pathological functions of macrophages in inflammation, tissue repair, lipoprotein metabolism, acute phase response, and in microbicidal, antiviral, tumoricidal, and immunoregulatory activities; however, macrophages may not be the sole source for the secretion of some of these products. The secretion of these products is intricately regulated, developmentally and environmentally.

Interferons in the treatment of human cancer.

Abstract: The interferons are the best known of biologic antineoplastic agents. Progress with the clinical application of interferons to cancer has been slow and complicated by the need for attention to a new spectrum of therapeutic and toxic effects manifest by the interferons. This summary of current phase I and II trial results with the interferons establishes their clinical potential. The maximally tolerated dosages of the most common species of interferon alpha produced in eukaryotic cells as well as by recombinant DNA technology in bacteria are now described in a variety of different disease states. "Naturally" produced eukaryotic as well as bacterially synthesized interferons have a similar, wide range of biologic effects in vitro and in vivo. Antiviral, antiproliferative, immunologic, and enzymologic functions of the interferons relevant to antineoplastic functions are under study. Knowledge of these mechanisms should improve the clinical results obtained in human cancer. Species and subspecies differences in the activity of interferons may lead to selective use of the pure interferon subspecies, alone or in combination. The use of the interferons and other antineoplastic biologics, such as antibody or chemotherapy, are subsequent goals that are now on the horizon.

Recombinant alpha-2 interferon therapy for Kaposi's sarcoma associated with the acquired immunodeficiency syndrome

Abstract: In a randomized prospective study we tested the toxicity and efficacy of recombinant alpha-2 interferon in the treatment of Kaposi's sarcoma associated with the acquired immunodeficiency syndrome. High doses (50 X 10(6) U/m2 body surface area, intravenously) or low doses (1 X 10(6) U/m2, subcutaneously) of recombinant alpha-2 interferon were administered to 20 patients for 5 days/wk, every other week, for four treatment cycles. Therapy was well tolerated subjectively and caused only mild hematologic and hepatic toxicity at both dose levels. No consistent or sustained changes were seen in immunologic variables during or after treatment. Six patients with Kaposi's sarcoma, four at high dose and two at low dose, had objective responses (complete or partial) to treatment. However, therapy did not appear to eradicate cytomegalovirus carriage or prevent opportunistic infections related to cytomegalovirus.

Site-specific mutagenesis of the human fibroblast interferon gene

Abstract: Human fibroblast interferon has three cysteine residues, located at amino acid positions 17, 31, and 141. Using the technique of site-specific mutagenesis with a synthetic oligonucleotide primer, we changed the codon for cysteine-17 to a codon for serine. The resulting interferon, IFN-beta Ser-17, retains the antiviral, natural killer cell activation, and antiproliferative activities of native fibroblast interferon. The purified IFN-beta Ser-17 protein has an antiviral specific activity of 2 X 10(8) units/mg, similar to that of purified native fibroblast interferon. In addition, the purified protein is stable to long-term storage at -70 degrees C.

Gamma-interferon is one of several direct B cell-maturing lymphokines.

Abstract: Two classes of molecules often released after the interaction of T lymphocytes, macrophages and antigen are B-cell maturation factors (BMF)1-3 and immune (gamma) interferon (IFN-gamma)4-7. BMFs directly induce the maturation of resting B lymphocytes to the state of active immunoglobulin secretion, while IFN-gamma is defined by the reduction of viral infectivity in vitro. However, interferons have been shown to have a variety of effects and they have also been reported both to increase and decrease B-cell differentiation in intact animals and complex cellular mixtures in vitro. Here we show that murine IFN-gamma produced by recombinant DNA technology shows similar biological effects to BMFs from two other sources. All three preparations induce immunoglobulin secretion by both normal resting murine splenic B cells and the comparable B-cell tumour line WEHI-279.1 (refs 1, 3). IFN-gamma and the other two BMFs are not identical, however, as anti-IFN-gamma antibodies block the effects on B cells of IFN-gamma, but not those of the other two lymphokines. IFN-gamma may be one of several molecules with a direct role in driving the maturation of resting B cells to active immunoglobulin secretion.

Enhanced expression of surface tumor-associated antigens on human breast and colon tumor cells after recombinant human leukocyte α-interferon treatment

Abstract: Treatment of human breast or colon carcinoma cells with recombinantly derived human leukocyte (clone A) interferon (IFN-alpha A) increases the surface expression of specific tumor-associated antigens (TAAs) recognized by monoclonal antibodies (MAbs). The MAbs used, B1.1, B6.2, and B72.3, recognize three distinct TAAs, i.e., the Mr 180,000 carcinoembryonic antigen, a Mr 90,000, and a Mr 220,000 to 400,000 glycoprotein, respectively. The binding of the MAbs to the surface of tumor cells increased in a dose-dependent manner, with optimal levels of TAA enhancement at 100 to 1,000 units IFN-alpha A/ml. Higher concentrations of IFN-alpha A that were cytostatic or cytotoxic were also less effective in enhancing TAA expression. Human melanoma (A375) cells and normal fibroblasts (WI-38 and Flow 4000) do not express any of the three TAAs, either before or after interferon treatment. The ability of IFN-alpha A to increase the expression of TAAs on human carcinoma cells was also temporally dependent, with optimal enhancement occurring after 16 to 24 hr. The enhancement of specific TAAs at the surface of the carcinoma cells by IFN-alpha A was confirmed, using fluorescence-activated cell sorter analysis. These data demonstrate that the IFN-alpha A-mediated increase of surface antigen is a result of both an accumulation of more antigen per cell, and an increase in the percentage of cells expressing the antigen. The ability of recombinant interferon to enhance specific TAAs on human carcinoma cells may be exploited in designing protocols for the in situ detection and therapy of human carcinoma lesions by MAbs, as well as in further defining the role of specific TAAs in the expression of the transformed phenotype.

Transcriptional induction of two genes in human cells by beta interferon.

Abstract: The binding of interferons to distinct cell surface receptors leads to the induction of synthesis of several unique polypeptides and their corresponding mRNAs (1-6). We have isolated two cDNAs that are complementary to nuclear RNA whose synthesis is induced from undetectable levels to maximal rates of transcription within 30-60 min after the addition of beta interferon to human fibroblasts or to HeLa cells. These results prove that a single polypeptide can, by binding to a specific plasma membrane receptor, promptly activate the transcription of a defined set of genes.

Role of γ-interferon in antibody-producing responses

Abstract: Interferon preparations, especially those containing γ-interferon (IFN-γ), have long been known to modulate immune responses1–3 However, because many studies used only partially purified interferons, it has been difficult to separate the immunoregulatory effects of the interferons from those of other biologically active molecules contaminating the preparations Recently, with the cloning of the Interferon genes in mouse and man, it has become possible to use these cloned interferons directly to test their effects in assays other than those involving the protection of cells from viruses For example, cloned IFN-γ has been shown to be a potent inducer of Ia antigen expression on macrophages4,5 Similarly, cloned IFN-γ has been reported to act as a macrophage activation factors, as judged by the ability of activated macrophages to kill tumour cells in vitro6 We demonstrate here that cloned murine IFN-γ can also substitute for a late-acting helper factor which acts synergistically with other helper factors in the stimulation of B-cell antibody responses in vitro

Interferon is the suppressor of hematopoiesis generated by stimulated lymphocytes in vitro.

Abstract: Lymphocytes that inhibit hematopoiesis may have a pathogenic role in some forms of bone marrow failure, and lymphocyte-mediated suppression may also be important in the normal regulation of bone marrow function. We have investigated the mechanism of in vitro suppression of hematopoiesis by T cells by using the methylcellulose colony culture system. Total peripheral blood T cells and separated subpopulations of helper (OKT4+) and suppressor (OKT8+) cells that have been stimulated by exposure to lectin suppress autologous colony formation by bone marrow myeloid (CFU-C) and erythroid (BFU-E) progenitor cells. Medium conditioned by these cells is also inhibitory, indicating that the suppressor activity is a soluble factor. A strong correlation existed for the concentration of interferon and the degree of hematopoietic suppressor activity in these supernatants; both activities peaked at days 3 to 5 of incubation and had sharply declined by day 7. Interferon production was enhanced by exposure of lymphocytes to sheep red blood cells during the rosetting procedure. Specific antiserum and a monoclonal antibody directed against gamma-(immune) interferon abrogated the inhibitory activity for hematopoiesis produced by lectin-stimulated T cells; an antiserum to alpha-interferon was generally much less effective in neutralizing activity. We infer from these results that gamma-interferon is the mediator of hematopoietic suppression generated by lectin-treated T-cells.

Acute Interstitial Nephritis with the Nephrotic Syndrome Following Recombinant Leukocyte A Interferon Therapy for Mycosis Fungoides

Abstract: RECOMBINANT leukocyte A interferon is a highly purified single molecular species of alpha interferon that is produced by recombinant-DNA methods and has been shown to have biologic activity.1 The c...

Systemic alpha‐interferon therapy of multiple sclerosis

Abstract: A randomized, double-blind, placebo-controlled crossover study tested the efficacy of natural alpha interferon in altering exacerbating-remitting MS. Twenty-four patients with frequent exacerbations were treated for 6-month periods, beginning with either 5 × l06 IU of interferon daily or placebo. A 6-month washout period followed each treatment. Exacerbation rates were reduced during interferon and placebo phases compared with pre-study rates; a greater reduction occurred on interferon, particularly following placebo, possibly reflecting a learning phenomenon. Fifteen patients with a strictly exacerbating-remitting course had fewer and milder exacerbations on interferon compared with those on placebo, whereas 9 patients with a progressive component continued to have active disease. These results suggest that interferon might reduce exacerbations in certain patients and indicate guidelines for future trials of interferon in MS.

Positive Interactions between Human Interferon and Cyclophosphamide or Adriamycin in a Human Tumor Model System

Abstract: Human lymphoblastoid interferon strongly increased the antitumor activity of suboptimal doses of two commonly used anticancer drugs, cyclophosphamide and Adriamycin, on a human breast tumor xenograft growing in nude mice. A combination of human lymphoblastoid interferon with either of these agents caused regression and in some cases total disappearance of tumors at doses of drug and interferon that, used singly, were capable only of inhibiting tumor growth. The combined therapy also resulted in a greatly increased survival. Studies with interferon and cyclophosphamide indicated that the antitumor activity was greatest when the two agents were administered simultaneously rather than sequentially.

Inhibition of growth of Toxoplasma gondii in cultured fibroblasts by human recombinant gamma interferon.

Abstract: The growth of Toxoplasma gondii in cultured human fibroblasts was inhibited by recombinant human gamma interferon at concentrations of 8 to 16 U/ml. The interferon was titrated by observing a total inhibition of parasite plaque formation 7 days after infection. Inhibition of the growth of T. gondii in the early days after infection was measured by marked reductions in the incorporation of radioactive uracil, a precursor that can only be used by the parasites. This assay showed that when cells were pretreated with gamma interferon for 1 day and then infected, inhibition of T. gondii growth could be readily detected 1 or 2 days after infection. When the pretreatment was omitted and parasites and gamma interferon were added at the same time, no inhibition of parasite growth could be detected 1 day later, although it was apparent after 2 days. Cultures from which the gamma interferon had been removed by washing after a 1-day treatment showed inhibition of T. gondii growth. Gamma interferon had no effect on the viability of extracellular parasites, but it did inhibit the synthesis of host cell RNA and protein by ca. 50% 3 days after treatment. This degree of inhibition is unlikely, of itself, to compromise the growth of T. gondii. Recombinant alpha and beta interferons had no effect on the growth of T. gondii. Images

Effect of IFN-γ on the immune response in vivo and on gene expression in vitro

Abstract: T lymphocytes produce a variety of immunoregulatory molecules including gamma interferon (IFN-γ)1–3 and antigen-specific suppressor and enhancer factors4–7. During our studies of active substances obtained from cloned T-cell lines, we observed that certain fractions administered to mice resulted in enhancement of immune responses. Preliminary characterization of the substance suggested that it could be IFN-γ and we therefore undertook a study of the action of IFN-γ produced by recombinant DNA methodology on immune responses. We found that for several antigens, administration of IFN-γ to mice leads to two- to five-fold enhancement of antibody formation provided that the IFN-γ and antigen are administered together. The effect was dose dependent, giving a maximal response at 500–600 anti-viral units per mouse. Preliminary studies suggest that the macrophage may be the target of IFN-γ action. Addition of IFN-γ to cultures of a macrophage cell line leads to a greater than 10-fold increase in the level of RNA coding for I-region-encoded cell surface molecules.

Selective reduction of c-myc mRNA in Daudi cells by human beta interferon

Abstract: Under normal growth conditions, the human lymphoblastoid cell line Daudi expresses high levels of c-myc mRNA. These cells are also sensitive to growth inhibition by interferons. We have compared the levels of mRNA for the c-myc in untreated and human beta interferon (IFN-beta)-treated Daudi cells by RNA dot-blot and blot-hybridization analysis methods. Using a synthetic oligonucleotide complementary to the human c-myc mRNA as the probe, we detected a more than 75% reduction in the c-myc hybridizable poly(A)+ RNA in the IFN-beta-treated cells. This reduction in the c-myc mRNA appears to be selective because the level of actin mRNA is not significantly affected by the IFN-beta treatment. In addition, neither in vitro translation of mRNA extracted from IFN-beta-treated cells nor in vivo synthesis of cellular proteins in IFN-beta-treated cells are quantitatively affected. We surmise that the selective reduction in the amount of c-myc mRNA in IFN-beta-treated Daudi cells may be related to the IFN-induced inhibition of the Daudi tumor cell growth.

In vivo significance of NK cell on resistance against virus (HSV-1) infections in mice.

Abstract: Susceptibility to infection with herpes simplex virus type 1 (HSV-1) was examined in euthymic as well as athymic nude mice which were continuously depleted of natural killer (NK) cell activity by i.v. injection of anti-asialo GM1. In those NK cell activity-depleted mice, the mortality rate of infection with HSV-1 and the virus titers in the brain, liver, and spleen were notably higher than in the control mice. The enhanced susceptibility was demonstrated only in the mice receiving anti-asialo GM1 and HSV-1 simultaneously, but not in the mice in which NK cell deletion was postponed by injecting the antisera 5 days after the virus inoculation. Interferon (IFN) production of peritoneal exudate cells was also reduced in the anti-asialo GM1-injected mice. The decline of resistance against HSV-1 infection proved to be primarily due to deletion of NK cells, but not due to the inability to produce IFN, because repeated injections of IFN increased the NK cell activity and prolonged the life of HSV-1-infected mice with an intact NK cell activity. In the NK cell activity-depleted mice, however, neither the NK cell activity nor the life span was improved by the administration of IFN.

Activation of the ppp(A2'p)nA system in interferon-treated, Herpes simplex virus-infected cells and evidence for novel inhibitors of the ppp(A2'p)nA-dependent RNase

Abstract: High doses (100–1000 reference units/ml) of α or β interferons are required to inhibit the growth of herpes simplex virus types I and II (HSV-I and HSV-II) in human Chang cells. In contrast, much lower doses (10–100 reference units/ml) of interferon inhibit replication of encephalomyocarditis virus (EMCV) in these cells. In the HSV-infected cells these high doses did not prevent the virus-induced shut off of host protein synthesis. The interferons were more effective in reducing the virus yield of HSV-I than of HSV-II. At the above concentrations they inhibited HSV-I protein synthesis but had little apparent effect on that of HSV-II. Similar amounts of (2′-5′)oligo(adenylate)s were synthesised in response to HSV-I, HSV-II and EMCV infection of Chang cells after treatment with α or β interferons. No (i.e. < 1 nM) (2′-5′)oligo(adenylate)s were found in control cells or on virus infection alone. Only low levels of ppp(A2′p)nA-specific rRNA cleavage were observed in the interferon-treated HSV-infected cells. In contrast, high levels were found in response to EMCV, despite the fact that ppp(A2′p)nA accumulated to similar levels with each of the three viruses in these cells. High-performance liquid chromatographic analysis of material from interferon-treated Chang cells 18 h after infection with HSV-I or HSV-II, combined with radiobinding, radioimmune and rRNA cleavage assays, confirmed the presence of ppp(A2′p)nA and ppp(A2′p)nA at greater than nanomolar concentration. In addition, apparently equivalent amounts of two other putative (2′-5′)oligo(adenylate) derivatives which compete in the radiobinding and radioimmune assays, were present. These compounds were only weak activators of the ppp(A2′p)nA-dependent RNase and under appropriate conditions were capable of inhibiting the activation of this RNase by authentic ppp(A2′p)nA. The presence of these potentially inhibitory compounds provides a possible explanation for the relatively low levels of activation of the ppp(A2′p)nA-dependent RNase in interferon-treated, HSV-infected Chang cells.

Endogenous regulation of macrophage proliferative expansion by colony-stimulating factor-induced interferon

Abstract: Stimulation of cultures of murine bone-marrow cells with specific macrophage growth factor (colony-stimulating factor I) resulted in the production of type I interferon. Neutralization of this endogenous interferon by antiserum directed against interferons alpha and beta resulted in a significant enhancement of mononuclear phagocyte proliferation from committed marrow precursors. The effect of the antiserum was lost in cultures depleted of adherent cells, an indication that an adherent regulatory cell (or cells) in the marrow limits mononuclear phagocyte proliferation by producing antiproliferative interferon in response to high levels of specific growth factor.

Interferon induces natural killer cell blastogenesis in vivo.

Abstract: Interferon (IFN), types beta and gamma, and IFN inducers polyinosinic-polycytidylic acid and lymphocytic choriomeningitis virus, all stimulated the generation of blast-natural killer (NK) cells in mouse spleens, Blast-NK cells were characterized on the basis of size, 3H-thymidine uptake, and NK cell markers These data indicate that in addition to augmenting NK cell-mediated lysis, IFN may regulate NK cell proliferation in vivo.

Injection of mice with antibody to interferon renders peritoneal macrophages permissive for vesicular stomatitis virus and encephalomyocarditis virus.

Abstract: Vesicular stomatitis virus (VSV) and encephalomyocarditis virus (EMCV) multiply in only a small percentage of peritoneal macrophages freshly explanted from 4- to 6-week-old male or female DBA/2, BALB/c, C3H, C57BL/6, or Swiss mice. However, when these mice were injected intraperitoneally with potent sheep (or goat) anti-mouse interferon alpha/beta globulin 4 days prior to harvesting peritoneal macrophages, the viruses multiplied to high titers and most of the cells were infected, as determined by total virus yield (VSV and EMCV), percentage of VSV antigen-positive cells (immunofluorescence), and determination of VSV infectious centers. This effect was not observed when mice were inoculated with other sheep hyperimmune or normal serum globulins. Anti-interferon globulin appeared to act in vivo because incubation of this globulin with peritoneal macrophages during the period of cell attachment or during the 18 hr after virus absorption did not render these cells permissive for VSV. Injection of mice with anti-interferon globulin did not affect the binding and uptake of labeled VSV by peritoneal macrophages. Although the underlying mechanism of this phenomenon is unknown, the results suggest that there may be low levels of endogenous interferon that contribute to host defense by maintaining some cells in an antiviral state.

Biological and antigenic similarities of murine interferon-gamma and macrophage-activating factor.

Abstract: Murine peritoneal exudate cells (PEC) treated with murine recombinant interferon-gamma (IFN-gamma) (greater than 99% estimated purity), or concanavalin A-stimulated spleen cell supernatants developed tumoricidal properties (macrophage activation factor [MAF] activity). MAF activity was found to occur with treatments of 10 U/ml IFN-gamma, and at levels as low as 1 U/ml IFN-gamma if a second signal (5 ng/ml endotoxin) was present in the MAF assay. Endotoxin (lipopolysaccharide [LPS]) alone at these levels failed to induce MAF; induction of MAF was observed at 1,000-fold greater levels. The ability of IFN-gamma to stimulate murine PEC was species specific. Various sources of materials that displayed MAF activity, including supernatants from interleukin 2-dependent cloned cytotoxic murine T lymphocyte lines that did not display detectable antiviral activity, were neutralized by antibody raised and affinity purified against recombinant IFN-gamma. Thus, IFN-gamma, although never detectable by antiviral assays, appears to be present in many lymphokine preparations and has potent macrophage activation capability.

Immunomodulatory Activity of Panax ginseng Extract

Abstract: Panax ginseng extract is capable of enhancing antibody plaque forming cell response and circulating antibody titre against sheep erythrocytes, cell mediated immunity against Semliki forest virus antigen, and natural killer cell activity in mice. It also enhanced production of interferon of both the pH stable and labile types induced by an interferon inducer of fungal origin.

Weak HLA and beta 2-microglobulin expression of neuronal cell lines can be modulated by interferon.

Abstract: Previous work showed that each of four human neuronal cell lines expresses less than or equal to 0.5% of the HLA-A,B,C and beta 2-microglobulin seen in glial, lymphoid, and other cell types, and there is a corresponding weak expression in neuroblastoma tumor and adult brain. Here, we probe the genetic basis of this weak expression. For each of three neuroblastoma cell lines, we show that HLA-A,B,C and beta 2-microglobulin can be induced by interferon and that the induction occurs within every cell of the population. Class II (Ia) molecules are not detected. Microscopic assay and radioimmunoassay of intact cells suggest that the induced antigen appears at the cell surface as well as within each cell. Immunoblot analysis confirms that the induced proteins have the structure of class I molecules. Thus, the normal weak HLA and beta 2-microglobulin expression of these cell lines appears to reflect a regulatory control rather than a primary genetic lesion. According to current theory, lack of HLA-A,B,C should protect transformed, infected, or damaged neurons--but also neurons in neural transplants--from T-cell-mediated immunosurveillance. The possibility that neuronal HLA-A,B,C expression may be under regulatory control is of importance in this context.

Inhibition of protein synthesis stimulates the transcription of human beta-interferon genes in Chinese hamster ovary cells

Abstract: Using Chinese hamster ovary (CHO) cells transfected with a plasmid carrying the human beta-interferon gene, we find that inhibitors of protein synthesis, in the absence of any other inducer, stimulate the production of interferon RNA; this effect is maintained in cells in which the plasmid sequences have been amplified 25- to 50-fold. Nuclear transcription assays show that a major effect of cycloheximide is to increase the rate of transcription of the interferon gene. This contradicts the generally accepted explanation that inhibitors of protein synthesis augment interferon production by stabilizing interferon mRNA. In addition, we have studied the effects of double stranded RNA [poly(rI) X poly(rC)] on the induction of interferon RNA in the presence and absence of cycloheximide. Our results indicate that poly(rI) X poly(rC) by itself causes a transient increase in interferon RNA; however, in the presence of cycloheximide this effect is prolonged. We do not, however, find an increase in transcription of the interferon gene(s) as an early response to poly(rI) X poly(rC). Finally, we have found that cells treated with cycloheximide or infected with Newcastle disease virus induce large amounts of a secreted 11-kDa protein. This cellular protein is not inducible by poly(rI) X poly(rC). We propose that both interferon and this 11-kDa protein belong to a family of proteins in which production is regulated in a coordinate fashion during viral inhibition of cellular protein synthesis.

Inducible expression of amplified human beta interferon genes in CHO cells.

Abstract: Plasmid DNA containing the human beta-interferon (IFN-beta) gene and mouse dihydrofolate reductase cDNA was transfected into dihydrofolate reductase-negative Chinese hamster ovary cells. Dihydrofolate reductase-positive transformants were obtained, and cells containing amplified copies of mouse dihydrofolate reductase were selected by exposure to increasing methotrexate concentrations. These cells were found to express high levels of human IFN-beta after polyriboinosinic acid-polyribocytidylic acid superinduction or NDV infection; this was a result of coamplification of the IFN-beta gene. Levels of expression of 1 U/cell per day were achieved on superinduction, giving corresponding titers of up to 10(10) U/liter medium in culture supernatants. Constitutive production of IFN-beta rates of about 0.5% of superinduced rates was observed; cells producing these levels of IFN-beta had acquired resistance to cytotoxic antiviral effects of IFN-beta. Two forms of human IFN-beta were produced; a major glycosylated 23,000-dalton form and an unglycosylated 18,500-dalton form. The latter had greatly reduced antiviral activity. IFN-beta production was very sensitive to cellular growth rate; the highest levels were produced by density-arrested cultures. Regulation of IFN-beta production by polyriboinosinic acid-polyribocytidylic acid or by cell density effects required the presence of DNA sequences 5' to the IFN-beta-coding sequences; replacement of these sequences with the simian virus 40 early promoter resulted in uninducible, density-independent production of IFN-beta.