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Direct activation of murine peritoneal macrophages for nitric oxide production and tumor cell killing by
1Department of Medicine, University of Kansas Medical Center, Kansas City 66160-7317, USA.
Abstract:
Interferon-gamma (IFN-gamma) is known to prime macrophages for tumor cell lysis and nitric oxide (NO) production as measured by enhanced sensitivity to lipopolysaccharide (LPS). In the present study, the ability of IFN-gamma to directly activate peritoneal macrophages from C57BL/6 and Balb/c mice for tumor cytotoxicity and NO production was evaluated. Macrophage-mediated tumor cell killing was measured by an 18 h 51Cr release assay using P815 mastocytoma cells as targets. Concurrent NO production was measured as nitrite in the supernatants of macrophage cultures. Incubation of macrophages with IFN-gamma resulted in activation of macrophages for tumor cell lysis. IFN-gamma alone also activated macrophages for NO production under identical conditions. Addition of LPS along with IFN-gamma resulted in synergism in the activation of macrophages for both cytolysis and NO production. LPS contamination of the IFN-gamma preparation was absent as evidenced by the following criteria: (1) the IFN-gamma preparation as well as the reagents used were shown to be free of LPS contamination based on LAL endotoxin tests (sensitivity 25 pg/ml), (2) the ability of IFN-gamma to activated macrophages was not abrogated by prior treatment of the cytokine with polymyxin B, whereas the effect of LPS was inhibited (70-100%) under similar conditions, (3) pretreatment of the IFN-gamma preparation with a specific endotoxin neutralizing protein did not abrogate the ability of IFN-gamma to induce macrophage activation, and (4) heat treatment of solutions containing IFN-gamma alone or IFN-gamma+LPS abolished only the effect of IFN-gamma, not that of LPS.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Interferon-gamma (IFN-gamma) directly activates macrophages for tumor cell lysis and nitric oxide (NO) production. This cytokine
Area of Science:
- Immunology
- Cell Biology
- Cancer Research
Background:
- Interferon-gamma (IFN-gamma) is known to prime macrophages for enhanced tumor cell lysis and nitric oxide (NO) production.
- The direct activating capacity of IFN-gamma on macrophages requires further investigation.
Purpose of the Study:
- To evaluate the direct activation of peritoneal macrophages by IFN-gamma for tumor cytotoxicity and NO production.
- To assess the synergistic effects of IFN-gamma and lipopolysaccharide (LPS) on macrophage activation.
Main Methods:
- Peritoneal macrophages from C57BL/6 and Balb/c mice were incubated with IFN-gamma.
- Macrophage-mediated tumor cell killing was measured using an 18-hour 51Cr release assay with P815 mastocytoma cells.
- Nitric oxide (NO) production was quantified as nitrite in macrophage culture supernatants.
Main Results:
- IFN-gamma alone activated macrophages, inducing both tumor cell lysis and NO production.
- The combination of LPS and IFN-gamma demonstrated synergistic activation of macrophages for cytolysis and NO production.
- Rigorous testing confirmed the absence of LPS contamination in the IFN-gamma preparation.
Conclusions:
- IFN-gamma directly activates macrophages, enhancing their ability to kill tumor cells and produce NO.
- IFN-gamma exhibits synergistic effects with LPS in macrophage activation.
- These findings highlight IFN-gamma's potent direct immunomodulatory effects on macrophages.