- Peritonitis caused by Candida albicans is a major complication of continuous ambulatory peritoneal dialysis (CAPD). Increasing the activity of the peritoneal macrophages--the predominant cell type found in the peritoneal cavity--may be of great importance in the prevention and therapy of peritonitis. Therefore, the activating effect of tuftsin was studied on human peritoneal macrophages from CAPD patients. Tuftsin induced a biphasic effect on macrophage activity within a range of 2 X 10(-9)-2 X 10(-6) M, with a maximal activity of 2 X 10(-7) M. At this concentration, tuftsin enhanced by twofold cell association with radiolabelled candida (from 2 +/- 0.2 to 4 +/- 0.2 candida per macrophage) and superoxide anion production in response to exposure to candida (from 150 +/- 20 to 300 +/- 20 nmoles/mg). These results suggest the potential use of tuftsin as a therapeutic drug.