Peritoneal mononuclear cell differentiation and cytokine production in intermittent and continuous automated peritoneal dialysis.

The long period without dialysate exchanges in nightly intermittent peritoneal dialysis (NIPD; no peritoneal filling during the day) and continuous cyclic peritoneal dialysis (CCPD; peritoneal filling during the day) might lead to an improved repopulation and functional regeneration of peritoneal macrophages (PMOs). We investigated this issue in seven stable, noninfected CCPD patients and seven stable, noninfected NIPD patients. PMO differentiation and cytokine production were measured after automated peritoneal dialysis and after a 12- to 14-hour period without dialysate exchanges. PMO maturation was evaluated by antibody staining. The proportion of "young" monocytes (positive for 27E10 and RM3/1) was decreased, whereas the proportion of mature macrophages (positive for 25F9) was significantly increased after the exchange-free interval. No differences between NIPD and CCPD were observed. The cytokine response to lipopolysaccharide was significantly increased after the exchange-free interval in both NIPD and CCPD. The interleukin-1 receptor antagonist (IL-1Ra) content of PMO lysates significantly increased after the exchange-free interval in both groups, but no changes were found in dialysate and serum IL-1Ra. We conclude that the long daytime interval without dialysate exchanges allows for additional PMO differentiation. Furthermore, the potential for cytokine release, which is inhibited (possibly by dialysate effects) after automated peritoneal dialysis, is restored after a 12- to 14-hour interval without peritoneal dialysis exchanges. The "dry" day in NIPD seems to have no important additional positive effect compared with CCPD.