Granulocyte macrophage-colony stimulating factor stimulates secretion of chemoattractive cytokines by peritoneal macrophages of CAPD patients

The recruitment of immunocompetent cells to the site of inflammation represents an essential part of the host defense during continuous ambulatory peritoneal dialysis (CAPD)-related peritonitis. Recently, it was shown that intraperitoneal application of granulocyte macrophage-colony stimulating factor (GM-CSF) leads to a marked transient recruitment of macrophages, paralleled by an increase in monocyte chemoattractant protein (MCP)-1. We, therefore, tested the in vitro effect of GM-CSF on the release of the chemotaxins interleukin (IL)-8 and MCP-1 by human peritoneal macrophages. Cells were stimulated with recombinant GM-CSF for 4, 12, and 20 hours in concentrations ranging from 0.1 to 100 pg/mL. Cells stimulated with lipopolysaccharide (LPS) or unstimulated cells served as control. Recombinant GM-CSF at concentrations found during CAPD peritonitis in vivo significantly increased the release of IL-8 and MCP-1 in a time- and dose-dependent manner. The maximum effect of IL-8 was observed directly after cell isolation, and decreased after a culture period of 10 days. Thus, our results indicate that peritoneal macrophages are the potential source of chemokines released upon GM-CSF stimulation.