Role of mesothelial cells in peritoneal antibacterial defence.

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.