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Updated: Aug 21, 2026
Depletion and Reconstitution of Macrophages in Mice
Published on: August 1, 2012
Reversibility of morphine effects on phagocytosis by murine macrophages
M I Lázaro1, N Tomassini, I González
1Biology Department, University of Puerto Rico, San Juan, USA.
Abstract:
Proneness of addicts to infections may be partially due to opiate effects on immune cells. We find that acute morphine inhibits phagocytosis in murine peritoneal macrophages in vitro with apparent desensitization at high concentrations, whereas chronic exposure results in a state akin to tolerance/dependence where macrophages seem to require morphine to phagocytize at a control level. However, both putative desensitization and tolerance/dependence are reversible, since drug re-addition several hours after withdrawal results in inhibition, as in acute exposure. This shows that opiate effects on immune cells are variably related to the experimental context in which they are administered, which is of relevance for understanding their potential role in immunosuppression.
Insights
Opiates like morphine impact immune cell function, affecting infection risk in addicts. Both acute and chronic morphine exposure alter macrophage phagocytosis, with effects being reversible and context-dependent.
Area of Science:
- Immunology
- Pharmacology
- Cell Biology
Background:
- Addiction to opiates is linked to increased infection susceptibility.
- Opiate drug effects on immune cells may contribute to this phenomenon.
Purpose of the Study:
- To investigate the in vitro effects of morphine on macrophage phagocytosis.
- To understand how acute versus chronic morphine exposure influences immune cell function.
- To explore the reversibility and context-dependency of opiate-induced immunomodulation.
Main Methods:
- Murine peritoneal macrophages were used for in vitro experiments.
- Phagocytosis assays were conducted following acute and chronic morphine exposure.
- Drug re-addition experiments were performed after withdrawal to assess reversibility.
Main Results:
- Acute morphine inhibited macrophage phagocytosis, with desensitization at high concentrations.
- Chronic morphine exposure led to a tolerance/dependence state, requiring morphine for normal phagocytosis.
- Both desensitization and tolerance/dependence effects were reversible upon drug withdrawal and re-administration.
Conclusions:
- Opiate effects on immune cells, specifically macrophage phagocytosis, are complex and context-dependent.
- These findings are relevant for understanding the role of opiates in immunosuppression and infection risk in addicts.
- The reversibility of these effects suggests potential therapeutic implications.
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