Host defence in continuous ambulatory peritoneal dialysis: the effect of the dialysate on phagocyte function.

Peritoneal dialysis fluid was examined after dwell periods of from 30 min to 18 h. Macrophages formed more than 70% of all cells recovered, irrespective of dwell time. The viability of these cells was 95% or greater even in 30 min effluent. Peritoneal macrophages and polymorphonuclear leucocytes were incubated in unused peritoneal dialysis fluid. By 30 min the viability of polymorphonuclear leucocytes had fallen to 50% but that of peritoneal macrophages was still 84%. However, phagocytosis of unopsonized zymosan by both cell types was depressed after only 10 min exposure. Peritoneal dialysis effluents obtained after dwell times of 30-180 min were examined for their effect on phagocytosis in vitro. These fluids suppressed peritoneal macrophages function as compared to RPMI 1640. Effluent after an overnight dwell did not affect phagocytosis. The suppressant effect decreased with increasing dwell time. Polymorphonuclear leucocytes were affected to a greater degree than peritoneal macrophages. Tests showed that this decreased phagocytosis was not due to cell death nor was it due to the osmolality or lactate content of the dialysate. Adjusting pH only improved cell function slightly. Phagocyte function appears to be depressed for clinically significant periods of the CAPD cycle.