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Morphine alters macrophage and lymphocyte populations in the spleen and peritoneal cavity
M E Hilburger1, M W Adler, T J Rogers
1Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, PA 19140, USA.
Abstract:
We have previously shown that subcutaneous implantation of a 75 mg morphine pellet results in suppression of the ability of murine splenocytes to mount an antibody response to sheep red blood cells, due in part to a reduction of macrophage function. The present studies used flow cytometry to examine whether the decrement in macrophage function in the spleens of morphine-treated mice results from a reduction in macrophage numbers. Parallel analysis was carried out on non-elicited peritoneal cells. In the spleen, morphine resulted in a reduction in the relative proportion of macrophages and B-cells, with a concomitant increase in the proportion of T-cells. Alteration in the ratio of CD4+ to CD8+ T-cells was not observed. In contrast, in the peritoneal cavity, morphine increased the number of macrophages and reduced the number of B-cells. Naltrexone blocked all of the changes in cellular composition. These results support the conclusion that an important mechanism in the immunosuppression seen in the spleens of mice implanted with morphine pellets is a differential reduction in the number of macrophages and B-cells as compared with T-cells. Further, these studies show that subsets of cells of the immune system are differentially affected by morphine in different anatomical compartments.
Insights
Morphine alters immune cell populations in mice, reducing spleen macrophages and B-cells while increasing T-cells. These changes, reversed by naltrexone, indicate compartment-specific immune suppression.
Area of Science:
- Immunology
- Pharmacology
- Cell Biology
Background:
- Subcutaneous morphine pellet implantation (75 mg) previously shown to suppress antibody response in murine splenocytes.
- This suppression is partly attributed to reduced macrophage function.
Purpose of the Study:
- To investigate if morphine-induced decrease in macrophage function is due to reduced macrophage numbers in mouse spleens.
- To analyze immune cell composition changes in spleen and peritoneal cavity following morphine treatment.
Main Methods:
- Flow cytometry used to analyze cellular composition of spleen and peritoneal cells in morphine-treated mice.
- Comparison of cell populations (macrophages, B-cells, T-cells) between treated and control groups.
- Assessment of naltrexone's effect on morphine-induced cellular changes.
Main Results:
- Morphine treatment reduced the proportion of macrophages and B-cells in the spleen, with a concurrent increase in T-cells.
- No significant alteration in the CD4+ to CD8+ T-cell ratio was observed in the spleen.
- In contrast, morphine increased macrophage numbers and decreased B-cells in the peritoneal cavity.
- Naltrexone administration effectively blocked all observed changes in cellular composition.
Conclusions:
- Morphine-induced immunosuppression in mouse spleens involves a differential reduction in macrophages and B-cells relative to T-cells.
- Morphine affects immune cell subsets differently across distinct anatomical compartments (spleen vs. peritoneal cavity).
- Naltrexone demonstrates efficacy in reversing morphine-mediated alterations in immune cell distribution.