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Activation of pleural macrophages by intrapleural application of Corynebacterium parvum
Abstract:
A single ipl injection of 0.25 mg CP into CBA mice led to accumulation of macrophages in the pleural cavity, but it did not influence RES as an injection given iv ipl CP caused a three-to-five-fold increase in the number of nucleated cells in the pleural cavity which persisted at least 14 days. Of these cells 86% were macrophages as shown by their esterase activity. Less than 30% of cells from the pleural cavity of normal mice were esterase positive. Macrophages from the pleural cavity of CP-treated mice were capable of destroying in vitro cultures of a syngeneic mammary carcinoma, while normal pleural macrophages exerted no effect; the former were not cytotoxic for either syngeneic or allogeneic embryo fibroblasts. Ipl CP protected mice against iv injected mammary carcinoma cells; given to mice 7 days after iv inoculation of tumor cells it significantly reduced the number of tumor nodules in their lungs.
Insights
Intrapleural injections of cyclophosphamide (CP) in mice significantly increased pleural macrophages, enhancing their ability to destroy mammary carcinoma cells and protect against tumor development.
Area of Science:
- Immunology
- Oncology
- Cell Biology
Background:
- The reticuloendothelial system (RES) plays a role in immune surveillance.
- Macrophages are key immune cells involved in tumor destruction.
Purpose of the Study:
- To investigate the effect of intrapleural cyclophosphamide (CP) on pleural macrophages and their anti-tumor activity.
- To assess the protective effect of CP against mammary carcinoma in mice.
Main Methods:
- CBA mice received a single intrapleural injection of 0.25 mg CP.
- Cellular composition of the pleural cavity was analyzed, focusing on esterase-positive cells (macrophages).
- In vitro cytotoxicity assays were performed using pleural macrophages against syngeneic mammary carcinoma cells and fibroblasts.
- Mice were challenged with intravenous mammary carcinoma cells, with CP administered at different time points.
Main Results:
- Intrapleural CP led to a 3-to-5-fold increase in pleural nucleated cells, predominantly macrophages (86%), persisting for at least 14 days.
- Pleural macrophages from CP-treated mice exhibited significant in vitro cytotoxicity against syngeneic mammary carcinoma.
- Normal pleural macrophages showed no cytotoxic effect.
- CP-treated macrophages were not cytotoxic to syngeneic or allogeneic embryo fibroblasts.
- Intrapleural CP administration protected mice against intravenous mammary carcinoma cells, significantly reducing lung tumor nodules when given 7 days post-inoculation.
Conclusions:
- Intrapleural cyclophosphamide effectively recruits and activates macrophages in the pleural cavity.
- These activated macrophages demonstrate specific anti-tumor cytotoxicity against mammary carcinoma.
- Intrapleural CP confers protection against mammary carcinoma metastasis.