Downregulation of Newcastle disease virus (NDV)-dependent IFN-alpha/beta production in macrophages by IFN-induced gene products of the locus If-1.

We have found that in cultured mouse bone-marrow-derived macrophages (BMDM), endogenous IFN-beta specifically regulates Newcastle disease virus (NDV) induced interferon (IFN)-alpha/beta synthesis, possibly by influencing the activity of genes within the regulatory locus If-1. Comparison of anti-IFN-beta-treated BMDM from C57BL/6 mice and the congenic line B.6C-H28c carrying the high (h) or low (l) producer allele of If-1, respectively, revealed a much stronger response of the If-1l allele to exogenous IFN-alpha treatment. Twenty IU rIFN-alpha 4 were sufficient to induce nearly complete suppression of NDV-induced IFN-alpha and IFN-beta production in BMDM from B6.C-H28c mice, but had no effect on the IFN-alpha/beta response induced by Sendai virus, another member of the paramyxovirus group. Simultaneous treatment of BMDM with cycloheximide inhibited the suppressive effect of rIFN-alpha 4, indicating that IFN induced the expression of one or several new proteins encoded by gene(s) within the If-1l locus which are responsible for the NDV-specific downregulation of IFN-alpha/beta production. A time course analysis indicated that the suppressive activity of IFN-induced If-1l gene products took 12 h to develop. It was preceded by an opposite priming effect, leading to enhancement of the early IFN-alpha/beta response to NDV measured 5 h after infection. This priming effect in BMDM was, however, only visible during an 8-h period of IFN-alpha treatment, whereas in the continued presence of IFN for 12 h or longer, priming was superimposed by the inhibitory action of the If-1l gene products.(ABSTRACT TRUNCATED AT 250 WORDS)     

Production of Interferon-β by Murine T-Cell Lines Induced by 10-Carboxymethyl-9-Acridanone

Besides the established T-cell property of producing gamma interferon (IFN-gamma), murine T cells additionally possess the ability to produce IFN-alpha and IFN-beta when appropriate inducers such as 10-carboxymethyl-9-acridanone (CMA) or Newcastle disease virus (NDV) are used. Interleukin 2 (IL-2)-dependent murine T-cell lines, but not purified resting splenic T cells, responded to CMA and NDV with production of IFN-alpha, beta. The IFN production by these T cells was not restricted to a special subset, since T cells expressing the Lyt 1+2- and the Lyt 1-2+ phenotype responded to these inducers with IFN production. After prolonged passaging of the T-cell lines in IL-2-containing medium, the ability to respond to CMA with production of antiviral activity was sustained longer than the ability for concanavalin A-induced IFN-gamma production. Whereas the NDV-induced T-cell supernates contained both IFN-alpha and IFN-beta, the induction with CMA resulted exclusively in the synthesis of IFN-beta by the T-cell lines.     

Susceptibility to Yersinia pseudotuberculosis Infection is Linked to the Pattern of Macrophage Activation

T helper 1 cells play a crucial role in the clearance of Yersinia pseudotuberculosis infection. By producing cytokines and presenting antigens to T cells, activated macrophages can orientate the adaptive immune response. The pathway used by macrophages to metabolize arginine has been employed as an important parameter to discriminate their activation state. In this study, the pattern of macrophage activation in Y. pseudotuberculosis- infected BALB/ c ( Yersinia -susceptible) and C57BL/6 ( Yersinia -resistant) mice and their immunostimulatory capacity were analysed. In the early phase of infection, macrophages obtained from C57BL/6 mice produced higher levels of NO, lower arginase activity, and larger amounts of IL-12 and TNF-α than macrophages from BALB/ c mice. On the other hand, macrophages derived from BALB/ c mice produced higher levels of IL-10 and TGF-β than C57BL/6 mice. The Y. pseudotuberculosis infection leads to a fall in the macrophage immunostimulatory capacity of both strains of mice, with T-cell proliferation significantly reduced 12 h after infection. Moreover, we observed in the supernatant of co-culture of macrophages from infected mice with T lymphocytes from heat-killed Yersinia -immunized mice lower IFN-γ production by cells from BALB/ c mice than by C57BL/6 mice, and IL-4 was produced only by BALB/ c mice on the first- and third-day post-infection. These results suggest that the pattern of macrophage activation is associated with susceptibility and resistance to Y. pseudotuberculosis infection in BALB/ c and C57BL/6 mice.     

IL-3 is an important differentiation factor for the development of prostaglandin E2-producing macrophages between C57BL/6 and BALB/c mice

We have previously reported that peritoneal and splenic macrophages from Th2-dominant BALB/c mice produced higher amounts of prostaglandin (PG) E2 than cells from C57BL/6 mice. In this study, we investigated how macrophages from BALB/c mice acquire the ability of enhanced PGE2 production, using bone marrow-derived macrophages differentiated by M-CSF, GM-CSF or IL-3. There is no strain difference in PGE2 production by GM-CSF- and M-CSF-differentiated macrophages; however, IL-3-differentiated macrophages from BALB/c mice produced higher amounts of PGE2 and lower amounts of type I cytokines than cells from C57BL/6 mice. IL-3-differentiated macrophages from BALB/c mice expressed larger amounts of mRNA of membrane-bound (microsomal) PGE synthase-1 (mPGES-1). The amounts of PGE2 produced by macrophages were significantly reduced in mPGES-1-deficient mice, and these mice displayed enhanced Th1 responses after Propionibacterium acnes treatment compared with wild-type mice. Microarray analysis revealed 63 genes that are differentially expressed more than fivefold in macrophages between C57BL/6 and BALB/c mice. These results indicate that mPGES-1-mediated PGE2 produced by macrophages regulates immune responses, and IL-3 is an important factor for the differentiation of macrophages that produce higher amounts of PGE2 through mPGES-1 activity in BALB/c mice.     

Role of inducible nitric oxide synthase and NADPH oxidase in early control of Burkholderia pseudomallei infection in mice

Infection with the soil bacterium Burkholderia pseudomallei can result in a variety of clinical outcomes, including asymptomatic infection. The initial immune defense mechanisms which might contribute to the various outcomes after environmental contact with B. pseudomallei are largely unknown. We have previously shown that relatively resistant C57BL/6 mice can restrict bacterial B. pseudomallei growth more efficiently within 1 day after infection than highly susceptible BALB/c mice. By using this model, our study aimed to investigate the role of macrophage-mediated effector mechanisms during early B. pseudomallei infection. Depletion of macrophages revealed an essential role of these cells in the early control of infection in BALB/c and C57BL/6 mice. Strikingly, the comparison of the anti-B. pseudomallei activity of bone marrow-derived macrophages (BMM) from C57BL/6 and BALB/c mice revealed an enhanced bactericidal activity of C57BL/6 BMM, particularly after gamma interferon (IFN-gamma) stimulation. In vitro experiments with C57BL/6 gp91phox-/- BMM showed an impaired intracellular killing of B. pseudomallei compared to experiments with wild-type cells, although C57BL/6 gp91phox-/- cells still exhibited substantial killing activity. The anti-B. pseudomallei activity of C57BL/6 iNOS-/- BMM was not impaired. C57BL/6 gp91phox-/- mice lacking a functional NADPH oxidase were more susceptible to infection, whereas C57BL/6 mice lacking inducible nitric oxide synthase (iNOS) did not show increased susceptibility but were slightly more resistant during the early phase of infection. Thus, our data suggest that IFN-gamma-mediated but iNOS-independent anti-B. pseudomallei mechanisms of macrophages might contribute to the enhanced resistance of C57BL/6 mice compared to that of BALB/c mice in the early phase of infection.     

In Vitro Development of Bone-Marrow-Derived Macrophages Influence of Mouse Genotype on Response to Colony-Stimulating Factors and Autocrine Interferon Induction

Responsiveness to granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage CSF (M-CSF) of bone marrow cells derived from different mouse strains was investigated. There were great variations in proliferation between different strains of inbred mice. Bone marrow cells from mouse strains with a high rate of proliferation in response to GM-CSF also had a high proliferating capacity to M-CSF. The response to either CSF did not correlate with a certain H-2 haplotype. GM-CSF induced consistently higher proliferation than M-CSF. Proliferation in response to M-CSF, but not to GM-CSF, could be enhanced by the addition of antibodies against interferon (IFN). IFN is the only known inducer of (2'-5') oligoadenylate (oligo (A] synthetase. This enzyme was induced in macrophages grown in the presence of M-CSF, but not in GM-CSF promoted cells. Enzyme induction was completely abrogated by simultaneous treatment with anti-IFN alpha/beta. Infection of macrophages with herpes simplex virus type 1 (HSV) and vesicular stomatitis virus (VSV) revealed that GM-CSF-promoted cells were highly susceptible to lytic infection by these viruses. In contrast, virus titres in M-CSF-cultured cells were 100-fold lower. We conclude that, contrary to M-CSF, GM-CSF does not induce autocrine IFN during haematopoiesis. As judged from data with BALB/c mice, the sensitivity to the anti-proliferative effect of the autocrine IFN may be a factor which influences M-CSF-promoted proliferation.     

Bacterial induction of beta interferon in mice is a function of the lipopolysaccharide component

We investigated the reason for the inability of lipopolysaccharide (LPS)-resistant (Lps-defective [Lps(d)]) C57BL/10ScCr mice to produce beta interferon (IFN-beta) when stimulated with bacteria. For this purpose, the IFN-beta and other macrophage cytokine responses induced by LPS and several killed gram-negative and gram-positive bacteria in LPS-sensitive (Lps-normal [Lps(n)]; C57BL/10ScSn and BALB/c) and Lps(d) (C57BL/10ScCr and BALB/c/l) mice in vitro and in vivo were investigated on the mRNA and protein levels. In addition, double-stranded RNA (dsRNA) was used as a nonbacterial stimulus. LPS and all gram-negative bacteria employed induced IFN-beta in the Lps(n) mice but not in the Lps(d) mice. All gram-positive bacteria tested failed to induce significant amounts of IFN-beta in all four of the mouse strains used. As expected, all other cytokines tested (tumor necrosis factor alpha, interleukin 1alpha [IL-1alpha], IL-6, and IL-10) were differentially induced by gram-negative and gram-positive bacteria. Stimulation with dsRNA induced IFN-beta and all other cytokines mentioned above in all mouse strains, regardless of their LPS sensitivities. The results suggest strongly that LPS is the only bacterial component capable of inducing IFN-beta in significant amounts that are readily detectable under the conditions used in this study. Consequently, in mice, IFN-beta is inducible only by gram-negative bacteria, but not in C57BL/10ScCr or other LPS-resistant mice.     

Role of interferon and interferon regulatory factors in early protection against Venezuelan equine encephalitis virus infection

To investigate the role of type I interferon (IFN) and its regulatory transacting proteins, interferon regulatory factors (IRF-1 and IRF-2), in early protection against infection with virulent Venezuelan equine encephalitis virus (VEE), we utilized mice with targeted mutations in the IFN-alpha/beta receptor, IRF-1, or IRF-2 genes. IFN-alpha/beta-receptor knockout mice are highly susceptible to peripheral infection with virulent or attenuated VEE, resulting in their death within 24 and 48 h, respectively. Treatment of normal macrophages with anti-IFN-alpha/beta antibody prior to and during infection with molecularly cloned virulent VEE resulted in increased VEE replication. However, treatment with high doses of IFN or IFN-inducing agents failed to alter percentage mortality or average survival times in mice challenged with a low dose of virulent VEE. In IRF-1 and IRF-2 knockout mice (IRF-1(-/-) and IRF-2(-/-)), the 100% protection against virulent VEE that is conferred by attenuated VEE within 24 h in control C57BL/6 mice was completely absent in IRF-2(-/-) mice, whereas 50% of IRF-1(-/-) mice were protected. IRF-2(-/-) mice were deficient in clearing VEE virus from the spleen and the brain compared to the heterozygous IRF-2(+/-) knockout or C57BL/6 (+/+) mice. Furthermore, a distinct pattern of histopathological changes was observed in brains of IRF-2(-/-) mice after VEE exposure. Taken together, these findings imply that the altered immune response in IRF-1 and IRF-2 knockout mice results in altered virus dissemination, altered virus clearance, and altered virus-induced pathology. Thus, type I interferon, as well as IRF-1 and IRF-2, appears to play an important and necessary role in the pathogenesis of, and protection against, VEE infection.     

Resistance to Mycobacterium lepraemurium is correlated with the capacity to generate macrophage activating factor(s) in response to mycobacterial antigens in vitro.

The kinetics of cell-mediated immunity developed during the course of Mycobacterium lepraemurium infection were determined in resistant (C57BL) and susceptible (BALB/c) mice. Control of M. lepraemurium growth following footpad infection was T-cell dependent in C57BL mice as shown by the finding that T-cell deprived mice had enhanced bacterial counts in the footpad. In contrast, T-cell deprivation did not significantly alter the course of infection in BALB/c mice. However a T-cell dependent inflammatory response, resulting in an increase in size of the infected footpad, occurred in both strains, although it developed slightly later in BALB/c mice. Cells isolated from the lymph nodes, draining the infected foot-pads, were assayed for their proliferative responses to heat-killed M. lepraemurium (HK-MLM) antigens. Although lymph node cells from both mouse strains proliferated to HK-MLM early in the infection (1-2 weeks) both C57BL and BALB/c mice developed diminished in vitro proliferative reactivity within 4-6 weeks post-infection. Supernatants derived from cultures of lymph-node cells that had been stimulated with concanavalin A (Con A) or HK-MLM antigens, were assayed for the presence of macrophage-activating factor (MAF) activity using a tumour cytostasis assay and interferon (IFN) activity using a viral growth inhibition assay. Significantly higher levels of MAF and IFN were found in culture supernatants deprived from HK-MLM stimulated lymph-node cells from infected C57BL mice than from BALB/c mice during the first 8 weeks of infection. However, cells from infected mice of both strains produced similar amounts of both MAF and IFN in response to Con A.     

Differential susceptibility to acute Trypanosoma cruzi infection in BALB/c and C57BL/6 mice is not associated with a distinct parasite load but cytokine abnormalities

Inoculation of Trypanosoma cruzi, Tulahuén strain, into C57BL/6 and BALB/c mice led to an acute infection characterized by marked parasitaemia, myocardial inflammation and thymocyte depletion. While C57BL/6 mice showed a progressive and lethal disease, BALB/c mice partly recovered. To characterize these murine models more effectively, we studied the parasite burden, serum levels of major infection outcome-related cytokines, the in vitro features of T. cruzi infection in peritoneal macrophages and the immunophenotype of thymic cells. The greater disease severity of T. cruzi-infected C57BL/6 mice was not linked to an increased parasite load, as parasitaemia, myocardial parasite nests and amastigote counts in peritoneal macrophages were not different from those in BALB/c mice. Cortical thymocyte loss was accompanied by the presence of apoptotic bodies and fragmented nuclear DNA, whereas fluorocytometric analysis at 17 days postinfection (p.i.) revealed a more pronounced loss of CD4+ CD8+ cells in C57BL/6 mice. This group displayed higher levels of TNF-alpha on days 14 and 21 p.i., in the presence of lower IL-1beta and IL-10 concentrations by days 14 and 21, and days 7 and 14 p.i., respectively. Day-21 evaluation showed higher concentrations of nitrate and TNF-alpha soluble receptors in C57BL/6 mice with no differences in IFN-gamma levels, with respect to the BALB/c group. Increased morbidity of C57BL/6 T. cruzi-infected mice does not seem to result from an aggravated infection but from an unbalanced relationship between pro- and anti-inflammatory mediators.     

Induction of interferon-alpha by interferon-beta, but not of interferon-beta by interferon-alpha, in the mouse

The antigenicity of the interferon (IFN) produced in transgenic mice carrying an extra mouse IFN-beta gene under the control of mouse metallothionein-I enhancer-promoter was examined after induction with Cd2+. Unexpectedly, IFN-alpha in addition to IFN-beta was detected in the serum. Induction of IFN-alpha was also observed when recombinant mouse IFN-beta was injected into normal mice. IFN-alpha was first detected in the circulation 6-10 hr after the administration of IFN-beta, and after 12 hr, IFN-alpha became the major component of serum IFN. On the other hand, when IFN-alpha was injected, no production of IFN-beta was observed. Messenger RNAs specific for IFN-alpha and endogenous IFN-beta were detected in the spleen, though the amount of IFN-beta mRNA was much less than that of IFN-alpha mRNA. These mRNAs were not detected in other organs including the liver where exogenous IFN-beta gene was markedly expressed. These observations showed that the expression of IFN-alpha is inducible by IFN-beta in the mouse, and the spleen was suggested to be the main site of production. Possible mechanisms of the induction are discussed.     

Differential CD86 and CD40 co-stimulatory molecules and cytokine expression pattern induced by Trypanosoma cruzi in APCs from resistant or susceptible mice

Differential aspects of the host immune response generated by Trypanosoma cruzi infection were examined in two different mouse strains, BALB/c (haplotype H2-Kd) which does not overcome the acute phase of the infection and C57BL/6 (haplotype H2-Kb) which survives to the acute phase. After infection an increase in CD3+ T cells was observed in both mouse strains in the peritoneal cavity. However, while the CD3+ T cells from the BALB/c mice showed an increase in the IL-4 cytokine expression level, the same type of cells from the C57BL/6 mice showed an increase in IFN-gamma expression. In addition, only the macrophages from the C57BL/6 mice were activated secreting IL-12 and TNF-alpha and producing, moreover, high levels of nitrites. It was observed that also after parasite infection the expression of macrophage and dendritic cells CD40 and CD86 co-stimulation molecules from the spleen were diminished in BALB/c but not in C57BL/6 mice. In correlation with this observation the macrophages from the spleen of infected BALB/c mice secreted lower concentrations of nitrites than the C57BL/6 mouse cells. Also, the spleen dendritic cells from infected BALB/c mice had a small potential to present alloantigens in contrast to that observed in the infected C57BL/6 mouse cells.     

Role of interferon in persistent infection of macrophages with herpes simplex virus

Splenic macrophage cultures from C57BL/6 mice resistant to infection with herpes simplex virus (HSV) in vivo survived HSV infection in vitro. In contrast, macrophages from HSV-susceptible DBA/2 mice were completely lysed by the virus. During prolonged culturing, macrophages from C57BL/6 mice continued to produce infectious virus, indicating establishment of a persistent infection. At this time, interferon (IFN) was undetectable. However, as shown directly by the addition of an anti-IFN serum and indirectly by an increased activity of (2'-5')oligoadenylate synthetase, IFN was involved in the maintenance of the persistent infection. During the acute phase of virus infection, viral DNA replication was identical in macrophages from resistant or susceptible mice. Later, viral DNA content and the number of cells expressing HSV antigens decreased in macrophages from C57BL/6 mice. However, single cells remained to express viral proteins and to produce infectious particles. The results show that macrophages can be persistently infected with HSV due to their genetically controlled properties.     

The role of macrophage activation and of Bcg-encoded macrophage function(s) in the control of Mycobacterium avium infection in mice.

Following the intraperitoneal inoculation of 2.5 x 10(8) colony-forming units of Mycobacterium avium strain ATCC 25291, there was bacillary growth in the liver, spleen and peritoneal cavity of C57BL/6, C57BL/10, DBA/1 and BALB/c mice whereas DBA/2, C3H/He, CBA/Ca and CD-1 mice controlled the infection showing constant or slightly decreasing numbers of viable bacteria in the liver and spleen and effective clearance of the bacilli from the peritoneal cavities. The acquisition of non-specific resistance (NSR) to Listeria monocytogenes during the infection by M. avium was high in C57BL/6, BALB/c and C3H/He mice and negligible in DBA/2 and CD-1 mice. The magnitude of the acquisition of NSR was reduced in T cell-deficient mice and was directly proportional to the dose of the inoculum of M. avium. The production of hydrogen peroxide by phorbol myristate acetate-stimulated peritoneal macrophages of M. avium-infected mice was higher in C57BL/6 and BALB/c mice than in CD-1, DBA/2 and C3H/He animals. BALB/c. Bcgr (C.D2) mice, unlike their congenic strain BALB/c, restricted bacterial growth following the intravenous inoculation of 2.5 x 10(8) CFU of M. avium as efficiently as DBA/2 mice. C.D2 and BALB/c peritoneal macrophages from infected mice produced similar amounts of H2O2 but BALB/c mice developed higher levels of NSR to listeria than C.D2 mice. The production of nitrite by peritoneal macrophages from infected mice was found to be enhanced in DBA/2 and C3H/He but not in BALB/c, C57BL/6, DC-1 and C.D2 mice. Resident peritoneal macrophages from C.D2 mice were more bacteriostatic in vitro for M. avium than macrophages from BALB/c mice. The same relative differences between the two macrophage populations were observed when the cells were activated with lymphokines. The results show that the populations were observed when the cells were activated with lymphokines. The results show that the resistance to M. avium infection in mice is under the control of the Bcg gene and that susceptibility may be due to some defect in macrophage antibacterial function not completely overcome by the activation of this phagocyte in the susceptible strains of mice.     

Mouse genes influence antiviral action of interferon in vivo.

BALB/c mice are more sensitive to the antiviral effect of interferon than C57BL/6 mice, as demonstrated by experiments involving protection against lethal infection with encephalomyocarditis virus. This greater sensitivity of the BALB/c genotype to interferon action is in accord with previous observations that the bone marrow-derived erythroid precursors and macrophages of BALB/c mice are more sensitive to the anti-proliferative action of interferon than those of C57BL/6 mice. An analysis of the loci involved in the modulation of the activity of interferon against encephalomyocarditis virus infection was carried out in (BALB/c x C57BL/6)F1 progeny and in six recombinant inbred lines originally derived from a BALB/c x C57BL/6 cross. The antiviral effect of exogenous interferon in the F1 progeny was comparable to the effect in BALB/c mice, indicating dominance of the greater sensitivity to interferon action. The results obtained with the six recombinant inbred lines suggested a multifactorial influence. In vitro, interferon pretreatment of encephalomyocarditis virus-infected BALB/c and C57BL/6 fibroblast cultures did not reveal a difference in sensitivity between the two mouse genotypes. This finding demonstrates that it is not always possible to extrapolate from in vitro to in vivo when sensitivity to interferon action is studied.     

Evidence that NK cells and interferon are required for genetic resistance to lethal infection with ectromelia virus

Summary C 57 BL/6 mice developed resistance to lethal intravenous challenge with virulent (Moscow strain) ectromelia virus between 2 and 3 weeks of age. The fraction of C 57 BL/6 mice in which virus was detected in spleen was significantly lower than for DBA/2 mice by day 3. Thereafter, C 57 BL/6 mice had significantly reduced virus titers in spleen compared with those of DBA/2 mice. Resistance was abrogated by treatment with anti-asialo GM₁ gammaglobulin, which blocks NK cell activity, or with anti-interferon (IFN) , . C 57 BL/6 mice carrying the bg/bg mutation, associated with a deficiency of NK cells, were highly susceptible to lethal infection as were athymic mice derived from a resistant genetic background. Virus titers in spleens of C 57 BL/6 mice treated with anti-asialo GM₁ or anti-IFN , were significantly higher 4 days after virus challenge than were titers in C 57 BL/6 mice treated with normal rabbit serum. The results strongly suggest that genetic resistance to lethal ectromelia virus infection requires non-specific host defenses such as NK cells and IFN , that are activated during the first 3 to 4 days of infection.     

Rapid killing of actinomycin D-treated tumour cells by mononuclear phagocytes: reactivity in mouse strains with defective classical tumour cytotoxicity

In confirmation of previous data, macrophages from C3H/HeJ, C57BL/10ScCR and A/J mice, exposed in vivo to BCG or in vitro to lymphokines, had little tumoricidal activity, as assessed in a 48-hr [3H]thymidine release assay against TU5 tumour cells, compared to macrophages from C3H/HeN, C57BL/6 and (BALB/c X DBA/2)F1 mice. Macrophages from these mouse strains were examined for their capacity to kill actinomycin D-pretreated WEHI 164 sarcoma cells in a 6-hr 51chromium release assay (drug-dependent cellular cytotoxicity, DDCC). Peptone-elicited macrophages from C3H/HeN, C57BL/6, (BALB/c X DBA/2)F1, C57BL/10ScCR and A/J mice had high DDCC activity, whereas C3H/HeJ macrophages expressed little cytotoxicity against actinomycin D-pretreated WEHI 164 cells. In vivo exposure to BCG or inactivated streptococci caused a modest augmentation of the DDCC effector function of C3H/HeJ macrophages, but levels of reactivity remained 20-fold less than those of similarly treated normal mice. Thus, C57BL/10ScCR and A/J macrophages have defective classical direct cytotoxicity but mediate DDCC efficiently, whereas C3H/HeJ macrophages are defective in both effector functions.     

Effect of prostaglandins on interferon synthesis in murine macrophage-like cell lines

Murine macrophage-like cell lines were used to determine whether exogenously added prostaglandins and endogenous prostaglandins suppress interferon (IFN) synthesis in macrophages. The amount of IFN produced by J774A.1 cells induced with bacterial lipopolysaccharide (LPS) was reduced by 0.1 and 1 microM PGE1 or PGE2. These prostaglandins also inhibited Newcastle disease virus (NDV) induced IFN production, but only at a concentration of 1 microM. Thromboxane B2 at 0.01 to 1 microM had no effect on IFN production. Cells treated before, during, or before and during IFN synthesis with 0.15 to 4.8 microM indomethacin to inhibit prostaglandin synthesis did not increase IFN yields. Indomethacin also had no effect on NDV-induced IFN production by P388D1 and PU5-1.8 cells, and these cells remained nonresponsive to LPS for IFN production. These results indicate that endogenous levels of cyclooxygenase-dependent metabolites of arachidonic acid do not regulate IFN synthesis in macrophages.