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IL-12 induces IFN-gamma expression and secretion in mouse peritoneal macrophages
P Puddu1, L Fantuzzi, P Borghi
1Laboratorie of Immunology, Istituto Superiore di Sanità, Rome, Italy.
Abstract:
We previously reported that resting mouse peritoneal macrophages (PM) constitutively express low levels of IFN-gamma, whose production is consistently enhanced by exogenous IFN-gamma. In this study, we investigated the effects of IL-12 on the replication of vesicular stomatitis virus and on IFN-gamma gene expression in mouse PM. The addition of IL-12 to freshly explanted PM resulted in the persistence of an antiviral state to vesicular stomatitis virus, while control PM progressively became permissive for virus replication after 3 to 4 days in culture. The IL-12-induced antiviral state was inhibited by Abs to IFN-gamma, suggesting that endogenous IFN-gamma was largely responsible for this antiviral response. Moreover, IL-12 induced a consistent secretion of IFN-gamma, especially in cultured PM. The IL-1 2-induced antiviral state and IFN-gamma production were observed using PM from various strains of mice, including LPS-defective C3H/HeJ, NK-deficient bg/bg, DBA/2, Swiss (CD1), and Swiss nude mice treated or not with anti-asialo GM1 Abs. A 4-h treatment with IL-12 was sufficient to induce a marked accumulation of IFN-gamma mRNA, which was greater in cultured PM than in freshly harvested cells. Lastly, immunofluorescence studies in IL-12-stimulated macrophages clearly showed an enhancement of immunoreactive IFN-gamma compared with basal levels in cells exhibiting a macrophage (i.e., F4/80-positive) phenotype. Together, these findings demonstrate that IL-12 can directly stimulate mouse PM to produce IFN-gamma. We suggest that IL-12-induced IFN-gamma production by macrophages can play some role in the generation of the antiviral and immunoregulatory effects of IL-12.
Insights
Interleukin-12 (IL-12) induces an antiviral state in mouse macrophages by stimulating the production of interferon-gamma (IFN-gamma). This IL-12-driven IFN-gamma response in macrophages is crucial for antiviral defense.
Area of Science:
- Immunology
- Virology
- Cell Biology
Background:
- Resting mouse peritoneal macrophages (PM) constitutively express low levels of interferon-gamma (IFN-gamma).
- Exogenous IFN-gamma enhances IFN-gamma production in PM.
- The role of Interleukin-12 (IL-12) in modulating macrophage antiviral responses and IFN-gamma gene expression was previously unclear.
Purpose of the Study:
- To investigate the effects of IL-12 on vesicular stomatitis virus replication in mouse peritoneal macrophages (PM).
- To determine IL-12's impact on IFN-gamma gene expression and production in mouse PM.
- To elucidate the role of endogenous IFN-gamma in IL-12-mediated antiviral effects.
Main Methods:
- Primary mouse peritoneal macrophages (PM) were cultured and treated with IL-12.
- Antiviral state was assessed by monitoring vesicular stomatitis virus replication.
- IFN-gamma production and mRNA accumulation were measured using various techniques including immunofluorescence and RT-PCR.
- Antibodies to IFN-gamma were used to block the antiviral response.
Main Results:
- IL-12 treatment induced a persistent antiviral state in PM against vesicular stomatitis virus.
- This antiviral state was dependent on endogenous IFN-gamma, as it was inhibited by anti-IFN-gamma antibodies.
- IL-12 significantly enhanced IFN-gamma secretion and mRNA accumulation in PM, particularly in cultured cells.
- IL-12 directly stimulated IFN-gamma production in macrophages with a macrophage (F4/80-positive) phenotype.
Conclusions:
- IL-12 directly stimulates mouse peritoneal macrophages (PM) to produce IFN-gamma.
- IL-12-induced IFN-gamma production by macrophages contributes to the antiviral and immunoregulatory effects of IL-12.
- These findings highlight a key mechanism by which IL-12 mediates innate immune responses.