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Induction of IFN-gamma in macrophages by lipopolysaccharide
M J Fultz1, S A Barber, C W Dieffenbach
1Department of Microbiology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814.
Abstract:
In this paper we report that macrophages can be stimulated to express detectable levels of IFN-gamma-specific mRNA. Macrophages from lipopolysaccharide (LPS)-responsive, C3H/OuJ mice are induced by LPS to increase steady-state levels of IFN-gamma-specific mRNA, while those from LPS-hyporesponsive C3H/HeJ mice are not. This interstrain variation is apparently the result of LPS-specific signal differences since macrophages derived from both Lpsn and Lpsd mouse strains are able to produce comparable levels of IFN-gamma-specific mRNA following stimulation with polyinosinic-polycytidylic acid. The identity of the cell type responsible for this IFN-gamma message appears to be the macrophage as IFN-gamma-specific mRNA was also detectable following T and natural killer cell depletion, in the LPS-stimulated RAW 264.7 cell line, and in a homogeneous population of mature macrophages propagated in vitro by stimulation of bone marrow progenitors with recombinant colony stimulating factor-1. Immunofluorescent staining of fixed and permeabilized LPS-stimulated macrophages confirmed the presence of immunoreactive IFN-gamma protein. The possible significance of IFN-gamma production by macrophages is discussed in the context of normal macrophage differentiation as well as the inflammatory immune response.
Insights
Macrophages can produce interferon-gamma (IFN-gamma) mRNA and protein, with production levels varying based on lipopolysaccharide (LPS) responsiveness in different mouse strains. This suggests a role for macrophages in immune responses.
Area of Science:
- Immunology
- Cell Biology
Background:
- Macrophages are key immune cells involved in host defense.
- Interferon-gamma (IFN-gamma) is a crucial cytokine in immune regulation.
- Understanding macrophage cytokine production is vital for immune response studies.
Purpose of the Study:
- To investigate the capacity of macrophages to express IFN-gamma-specific mRNA and protein.
- To explore the influence of lipopolysaccharide (LPS) responsiveness on macrophage IFN-gamma production.
- To identify the specific cell type responsible for IFN-gamma expression in stimulated macrophages.
Main Methods:
- Stimulation of macrophages from different mouse strains (C3H/OuJ and C3H/HeJ) with LPS.
- Stimulation with polyinosinic-polycytidylic acid (poly I:C) to assess LPS-specific signaling.
- Depletion of T and natural killer cells.
- Culture of homogeneous macrophage populations from bone marrow progenitors.
- Detection of IFN-gamma-specific mRNA using molecular techniques.
- Immunofluorescent staining for IFN-gamma protein detection.
Main Results:
- Macrophages from LPS-responsive mice (C3H/OuJ) increased IFN-gamma mRNA levels upon LPS stimulation, unlike those from LPS-hyporesponsive mice (C3H/HeJ).
- Macrophage IFN-gamma mRNA production was comparable between strains when stimulated with poly I:C, indicating LPS-specific signaling differences.
- IFN-gamma mRNA and protein were confirmed in macrophages, even after T and NK cell depletion and in purified macrophage populations.
- RAW 264.7 cell line and in vitro propagated macrophages also expressed IFN-gamma mRNA.
Conclusions:
- Macrophages can be stimulated to produce IFN-gamma mRNA and protein.
- LPS-induced IFN-gamma production in macrophages is dependent on the mouse strain's LPS responsiveness.
- These findings highlight the potential role of macrophages in producing IFN-gamma during inflammatory immune responses and differentiation.