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Downregulation of tumor necrosis factor expression in the human Mono-Mac-6 cell line by lipopolysaccharide
1Institute for Immunology, University of Munich, Federal Republic of Germany.
Abstract:
Mono-Mac-6 cells, but not U937 cells, can be induced to rapidly express tumor necrosis factor (TNF) mRNA and protein when triggered with lipopolysaccharide (LPS) at 1 microgram/ml. Preincubation of the cells for 3 d with low amounts of LPS (10 ng/ml) results in nearly complete suppression of TNF secretion. This downregulation appears to occur at the pretranslational level since specific mRNA is virtually undetectable under these conditions. By contrast, the same preincubation with 10 ng/ml LPS results in enhanced phagocytosis (28.6-67.2% for Staphylococcus aureus), demonstrating that not all monocyte functions are suppressed. While these results show that only stringent exclusion of LPS from culture media allows for induction of TNF in the Mono-Mac-6 cell line, the pronounced effect of LPS preincubation may also provide a suitable model with which to study the mechanisms of LPS-induced desensitization.
Insights
Mono-Mac-6 cells rapidly express tumor necrosis factor (TNF) when stimulated with lipopolysaccharide (LPS). However, low-dose LPS preincubation suppresses TNF but enhances phagocytosis, offering insights into monocyte desensitization.
Area of Science:
- Immunology
- Cell Biology
Background:
- Tumor necrosis factor (TNF) is a key cytokine in immune responses.
- Lipopolysaccharide (LPS) is a potent immune stimulant.
- Monocyte cell lines like Mono-Mac-6 and U937 are used to study immune cell functions.
Purpose of the Study:
- To investigate the differential response of Mono-Mac-6 and U937 cells to LPS stimulation.
- To explore the effect of LPS preincubation on TNF production and phagocytosis in Mono-Mac-6 cells.
Main Methods:
- Stimulation of Mono-Mac-6 and U937 cells with LPS (1 µg/ml).
- Preincubation of Mono-Mac-6 cells with low-dose LPS (10 ng/ml) for 3 days.
- Measurement of TNF mRNA and protein expression.
- Assessment of phagocytosis of Staphylococcus aureus.
Main Results:
- Mono-Mac-6 cells, unlike U937 cells, express TNF mRNA and protein upon LPS stimulation.
- Low-dose LPS preincubation significantly suppresses TNF secretion in Mono-Mac-6 cells at the pretranslational level.
- This preincubation enhances phagocytic activity in Mono-Mac-6 cells, indicating selective functional modulation.
Conclusions:
- Stringent exclusion of LPS is necessary for TNF induction in Mono-Mac-6 cells.
- LPS preincubation in Mono-Mac-6 cells provides a model for studying LPS-induced desensitization mechanisms.
- Monocyte functions can be differentially regulated by LPS exposure.