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Ultrastructure of phagocytosed Paracoccidioides brasiliensis in nonactivated or activated macrophages
E Brummer1, S H Sun, J L Harrison
1Department of Medicine, Santa Clara Valley Medical Center, San Jose, California.
Abstract:
Transmission electron microscopy was used to study ultrastructures in Paracoccidioides brasiliensis yeast cells after ingestion by nonactivated or cytokine-activated murine peritoneal macrophages. Yeast cells ingested by nonactivated macrophages had typical bi- and trilayered cell walls, plasma membranes, mitochondria, nuclei, vacuoles, etc., which remained intact for 24 h of coculture. In contrast, yeast cells ingested by activated macrophages exhibited abnormal mitochondrial ultrastructures within 4 h of interaction. Subsequent events that occurred were the formation of several clear vacuoles per cell, disintegration of the cytoplasm, and development of empty cells with intact walls. These findings provide, for the first time, insights into stepwise damage to fungal cells by activated macrophages (of particular interest in this instance because of prior evidence that the damage is due to nonoxidative mechanisms) and give possible clues regarding fungicidal mechanisms.
Insights
Activated macrophages cause stepwise damage to Paracoccidioides brasiliensis yeast cells, starting with mitochondrial changes and leading to cell death. This reveals new insights into fungal cell destruction mechanisms.
Area of Science:
- Mycology
- Immunology
- Cell Biology
Background:
- Paracoccidioides brasiliensis is a fungus causing paracoccidioidomycosis.
- Macrophages are key immune cells involved in fungal clearance.
- Previous studies suggested nonoxidative mechanisms for macrophage-mediated fungal damage.
Purpose of the Study:
- To investigate the ultrastructural changes in Paracoccidioides brasiliensis yeast cells after ingestion by activated murine peritoneal macrophages.
- To elucidate the stepwise process of fungal cell damage induced by activated macrophages.
Main Methods:
- Transmission electron microscopy (TEM) was employed.
- Murine peritoneal macrophages, both nonactivated and cytokine-activated, were used.
- Co-culture of macrophages with Paracoccidioides brasiliensis yeast cells for up to 24 hours.
Main Results:
- Yeast cells in nonactivated macrophages remained intact with normal ultrastructure for 24 hours.
- Yeast cells in activated macrophages showed abnormal mitochondrial ultrastructures within 4 hours.
- Subsequent damage included vacuole formation, cytoplasmic disintegration, and empty cells with intact walls.
Conclusions:
- Activated macrophages induce a sequential damage pathway in Paracoccidioides brasiliensis yeast cells.
- The findings provide insights into the fungicidal mechanisms of activated macrophages, potentially via nonoxidative pathways.
- This study offers a detailed ultrastructural view of macrophage-mediated fungal cell destruction.