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Potentiation of lymphokine-induced macrophage activation by tumor necrosis factor-alpha
S Heidenreich1, M Weyers, J H Gong
1Institute of Immunology, University of Marburg, West Germany.
Abstract:
In this study, we examined the possible role of TNF-alpha and lymphotoxin (TNF-beta) as cofactors of macrophage activation. The results demonstrate that both TNF were capable of enhancing the cytostatic and cytolytic activity of murine peritoneal macrophages against Eb lymphoma cells. The potentiation of tumor cytotoxicity became apparent when macrophages from DBA/2 mice were suboptimally activated by either a T cell clone-derived macrophage-activating factor or by IFN-gamma plus LPS. Neither TNF-alpha nor TNF-beta could induce tumor cytotoxicity in IFN-gamma-primed macrophages, indicating that TNF cannot replace LPS as a triggering signal of activation. In LPS-resistant C3H/HeJ macrophages, which were unresponsive to IFN-gamma plus LPS, a supplementation with TNF fully restored activation to tumor cytotoxicity. Furthermore, TNF-alpha potentiated a variety of other functions in low-level activated macrophages such as a lactate production and release of cytotoxic factors. At the same time, TNF-alpha produced a further down-regulation of pinocytosis, tumor cell binding and RNA synthesis observed in activated macrophages. These data demonstrate new activities for both TNF-alpha and TNF-beta as helper factors that facilitate macrophage activation. In particular, the macrophage product TNF-alpha may serve as an autocrine signal to potentiate those macrophage functions that were insufficiently activated by lymphokines.
Insights
Tumor Necrosis Factor-alpha (TNF-alpha) and TNF-beta act as crucial cofactors in macrophage activation. These factors enhance macrophage cytotoxic activity against tumor cells, particularly when macrophages are suboptimally stimulated.
Area of Science:
- Immunology
- Cell Biology
- Cancer Research
Background:
- Macrophage activation is critical for immune responses against pathogens and tumors.
- Tumor Necrosis Factor (TNF) family members, including TNF-alpha and lymphotoxin (TNF-beta), are key cytokines involved in immune regulation.
- The precise role of TNF-alpha and TNF-beta as cofactors in modulating macrophage activation requires further elucidation.
Purpose of the Study:
- To investigate the role of TNF-alpha and TNF-beta as cofactors in macrophage activation.
- To determine if TNF-alpha and TNF-beta can enhance the cytotoxic and cytostatic activity of macrophages against tumor cells.
- To explore the impact of TNF-alpha and TNF-beta on various macrophage functions.
Main Methods:
- Murine peritoneal macrophages from DBA/2 and C3H/HeJ mice were used.
- Macrophages were activated with suboptimal stimuli such as T cell clone-derived macrophage-activating factor, IFN-gamma plus LPS.
- The effects of TNF-alpha and TNF-beta supplementation on macrophage cytotoxicity, lactate production, and other functions were assessed.
Main Results:
- Both TNF-alpha and TNF-beta enhanced the cytostatic and cytolytic activity of macrophages against Eb lymphoma cells.
- TNF-alpha and TNF-beta potentiated tumor cytotoxicity in suboptimally activated macrophages.
- In LPS-resistant macrophages, TNF supplementation fully restored activation to tumor cytotoxicity.
- TNF-alpha enhanced lactate production and release of cytotoxic factors while down-regulating pinocytosis, tumor cell binding, and RNA synthesis in activated macrophages.
Conclusions:
- TNF-alpha and TNF-beta act as important helper factors that facilitate macrophage activation.
- TNF-alpha may function as an autocrine signal to enhance macrophage functions insufficiently activated by lymphokines.
- These findings highlight the significant role of TNF-alpha and TNF-beta in augmenting anti-tumor immunity mediated by macrophages.