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Comparative effects of various classes of mouse interferons on macrophage activation for tumor cell killing
Abstract:
The effects of mouse interferon-alpha (MuIFN-alpha), -beta (MuIFN-beta), and -gamma (MuIFN-gamma) on macrophage activation for tumor cell killing were determined by using proteose peptone-elicited peritoneal macrophages from C3H/HeN and C3H/HeJ mice under conditions that either included or were free of detectable endotoxin. Alone, under the conditions used, none of the interferons was able to activate macrophages directly for tumor cell killing. However, with a second signal provided to responsive macrophages by contaminating endotoxin, added bacterial lipopolysaccharide (LPS), or heat-killed Listeria monocytogenes (HKLM), all three types of interferon induced cytolytic activity, with MuIFN-gamma approximately 500 to 1000-fold more active than either MuIFN-alpha or -beta. Thus, all three interferons were able to prime macrophages for killing but required a second signal before cytolytic activity could be expressed. When MuIFN-gamma was mixed with either MuIFN-alpha or -beta and placed on macrophages, little or no killing developed. Mixtures of MuIFN-gamma with either MuIFN-alpha or -beta did increase the sensitivity of macrophages to triggering by LPS, however, compared with macrophages treated with MuIFN-gamma alone. The results are collectively important because they i) confirm that significant quantitative differences exist between the various interferons with regard to their capacity to prime macrophages for tumor cell killing; ii) indicate that to be an efficient activator each type of interferon must be combined with a second stimulus, such as LPS or HKLM; iii) show that neither MuIFN-alpha nor -beta can provide an efficient second triggering signal for macrophages that are primed by MuIFN-gamma; and iv) document that mixtures of MuIFN-gamma with either MuIFN-alpha or -beta are most efficient at inducing priming, compared with any one of the interferons used alone.
Insights
Mouse interferons alpha, beta, and gamma prime macrophages for tumor cell killing but require a second signal. Interferon-gamma is most potent, but combinations with alpha or beta enhance LPS-induced priming.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Macrophages are crucial immune cells involved in tumor surveillance and elimination.
- Interferons (IFNs) are cytokines known to modulate immune responses, including macrophage activation.
- Understanding the specific roles of different IFN types in macrophage-mediated tumor cell killing is essential for developing immunotherapies.
Purpose of the Study:
- To investigate the effects of mouse interferon-alpha (MuIFN-α), -beta (MuIFN-β), and -gamma (MuIFN-γ) on macrophage activation for tumor cell killing.
- To determine the necessity of a second signal for IFN-induced macrophage cytotoxicity.
- To compare the relative potencies of different MuIFN types and their combinations in macrophage activation.
Main Methods:
- Peritoneal macrophages from C3H/HeN and C3H/HeJ mice were used.
- Macrophage activation was assessed under conditions with and without detectable endotoxin.
- Second signals included bacterial lipopolysaccharide (LPS) or heat-killed Listeria monocytogenes (HKLM).
- Tumor cell killing assays were performed to quantify macrophage cytotoxic activity.
Main Results:
- None of the MuIFNs alone directly activated macrophages for tumor cell killing.
- All three MuIFNs primed macrophages, but required a second signal (LPS or HKLM) for cytolytic activity.
- MuIFN-γ was 500-1000 times more potent than MuIFN-α or MuIFN-β in inducing killing.
- Combinations of MuIFN-γ with MuIFN-α or MuIFN-β enhanced macrophage sensitivity to LPS triggering compared to MuIFN-γ alone.
Conclusions:
- MuIFN-γ is the most potent interferon for priming macrophages for tumor cell killing.
- A second signal is indispensable for the expression of IFN-induced macrophage cytotoxicity.
- Combinations of MuIFN-γ with MuIFN-α or MuIFN-β are most effective in priming macrophages, highlighting synergistic effects.