Alternative activation of macrophages in human peritoneum: implications for peritoneal fibrosis

Background. Depending on the cytokine microenvironment, macrophages (Mφ) can adopt a proinflammatory (M1) or a profibrotic (M2) phenotype characterized by the expression of cell surface proteins such as CD206 and CD163 and soluble factors such as CC chemokine ligand 18 (CCL18). A key role for Mφ in fibrosis has been observed in diverse organ settings. We studied the Mφ population in a human model of peritoneal dialysis in which continuous stress due to dialysis fluids and recurrent peritonitis represent a risk for peritoneal membrane dysfunction reflected as ultrafiltration failure (UFF) and peritoneal fibrosis.