In vitro differentiation and characterization of human peritoneal macrophages from CAPD-peritonitis patients

Studies on human macrophages are restricted due to difficulties in isolatin g significant numbers of human macrophages. High numbers of monocytes/macro phages can be obtained from peritonitis effluents of patients treated with peritoneal dialysis. To determine whether these cells might be useful for f unctional studies, we characterized peritoneal macrophages (PM) immediately after isolation from the dialysate effluents and their subsequent differen tiation. During a 10 days culture period they differentiated morphologicall y and phenotypically (FACS-analysis) from monocyte-like cells to macrophage s. Reflecting the intraperitoneal inflammation we found protein- and mRNA-s ynthesis of IL-8 and monocyte-chemoattractant-protein-1 (MCP-1) to be upreg ulated in PM after isolation from the effluents. In contrast, TNF-alpha was downregulated and could not be stimulated by LPS and/or IFN-gamma, reflect ing the phenomenon of desensitization. After 10 days in culture, cytokine p roduction normalized to a constitutive level and the TNF-alpha responsivene ss to LPS was restored. These data suggest the recovery of PM from the infl ammatory prestimulation. Therefore PM harvested from peritoneal dialysis ef fluents might provide a useful tool for further studies on the role of huma n macrophages in inflammation.