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Role of mesothelial cells in peritoneal antibacterial defence
M A Muijsken1, H J Heezius, J Verhoef
1Eijkman-Winkler Laboratory for Medical Microbiology, State University Utrecht Medical School, The Netherlands.
Abstract:
Whether phagocytosis of Staphylococcus aureus by polymorphonuclear neutrophils, monocytes, and peritoneal macrophages takes place when the staphylococci are adherent to monolayers of human mesothelial cells in the absence of opsonins was investigated. Adherence of S aureus to mesothelial monolayers increased significantly when the bacteria were opsonised with pooled human serum, but phagocytosis by polymorphonuclear neutrophils and monocytes occurred independently. Phagocytosis by peritoneal macrophages, however, was only marginal. Pretreatment of polymorphonuclear neutrophils with inhibitors of cellular metabolism and motility reduced their phagocytic capacity. These results indicate that the surface of mesothelial cells provides favourable conditions for the elimination of staphylococci in the peritoneal cavity. Phagocytic motility seems to be important in surface phagocytosis. The inability of peritoneal macrophages to phagocytise staphylococci adherent to the mesothelial cells suggests that they contribute little to the antibacterial defence of the peritoneal membrane of patients receiving peritoneal dialysis.
Insights
Human mesothelial cells facilitate Staphylococcus aureus clearance by immune cells like neutrophils and monocytes, independent of opsonins. This suggests mesothelial cells enhance peritoneal cavity antibacterial defenses.
Area of Science:
- Immunology
- Cell Biology
- Microbiology
Background:
- Phagocytosis is a key immune mechanism for clearing bacterial pathogens.
- The role of host cell surfaces in modulating phagocytosis requires further investigation.
- Staphylococcus aureus is a common cause of peritoneal infections, particularly in patients undergoing peritoneal dialysis.
Purpose of the Study:
- To investigate the phagocytosis of Staphylococcus aureus by human immune cells when bacteria adhere to mesothelial cells.
- To determine if opsonins are necessary for this process.
- To assess the contribution of different immune cells to bacterial clearance in this context.
Main Methods:
- Co-culture of Staphylococcus aureus with human mesothelial cell monolayers.
- Assessment of bacterial adherence and phagocytosis by polymorphonuclear neutrophils, monocytes, and peritoneal macrophages.
- Evaluation of phagocytosis in the presence and absence of human serum opsonins.
- Inhibition studies using metabolic and motility inhibitors on phagocytic cells.
Main Results:
- Bacterial adherence to mesothelial cells increased with serum opsonization.
- Phagocytosis by polymorphonuclear neutrophils and monocytes occurred independently of opsonins.
- Peritoneal macrophages showed only marginal phagocytosis of adherent bacteria.
- Inhibiting cellular metabolism and motility reduced neutrophil phagocytic capacity.
Conclusions:
- Mesothelial cell surfaces create favorable conditions for Staphylococcus aureus elimination in the peritoneal cavity.
- Phagocytic motility is crucial for effective surface phagocytosis.
- Peritoneal macrophages contribute minimally to antibacterial defense against adherent Staphylococcus aureus on mesothelial cells, impacting patients on peritoneal dialysis.