Inverse MCP-1/IL-8 ratio in effluents of CAPD patients with peritonitis and in isolated cultured human peritoneal macrophages

An important event in intraperitoneal inflammation is the influx of leukocytes into the peritoneal cavity. Chemokines such as interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) play a major role in the recruitment of immune cells to the site of inflammation. We determined the concentrations of two members of the chemokine family, IL-8 and MCP-1, in the dialysate effluents of 18 continuous ambulatory peritoneal dialysis (CAPD) patients with peritonitis and of 18 non-infected CAPD patients by specific enzyme-linked immunosorbant assays (ELISA). Isolated peritoneal macrophages (PMs) from CAPD peritonitis patients were cultured and IL-8 and MCP-1 production was determined on protein (ELISA) and mRNA level (Northern blot) at designated timepoints over a 72-h culture period. PMs from non-infected patients served as controls. Much higher concentrations of IL-8 and MCP-1 were found in dialysate effluents of peritonitis patients than in effluents of non-infected patients: IL-8 2.39 ± 1.15 vs 0.05 ± 0.01 ng/ml and MCP-1 22.5 ± 6.27 vs 0.42 ± 0.07 ng/ml. IL-8 and MCP-1 release by cultured PMs from peritonitis patients and non-infected patients revealed significant differences: IL-8 40.3 ± 2.2 ng/ml after 3 h and 194.2 ± 34.9 ng/ml after 12 h compared to 21.02 ± 6.15 ng/ml after 3 h and 89.64 ± 30.28 ng/ml after 12 h, respectively; MCP-1 3.3 ± 0.9 ng/ml after 3 h and 25.7 ± 7.4 ng/ml after 12 h compared to 1.1 ± 0.2 ng/ml and 1.8 ± 0.2 ng/ml, respectively. Interestingly, the ratio of IL-8 to MCP-1 concentrations in the dialysate effluents (1:9.4) is reversed in the supernatants of cultured PMs. In the effluents and in the culture supernatants of PMs from CAPD peritonitis patients high amounts of IL-8 and MCP-1 are detectable, suggesting that PMs are an important source for these chemokines during peritonitis. Because of the inverse ratio of IL-8 and MCP-1 in the effluents and culture supernatants it can be assumed that PMs are responsible for the MCP-1 concentration to a lesser extent than for the IL-8 concentration in the effluents.