Properties of human peritoneal macrophages from continuous ambulatory peritoneal dialysis (CAPD) patients.

Patients undergoing CAPD are prone to episodes of peritonitis caused principally by infection with Staphylococcus epidermidis. Since macrophages are believed to be of prime importance in protection of the peritoneal cavity we have examined certain activities of CAPD peritoneal macrophages and compared them with normal peritoneal macrophages and blood monocytes. CAPD macrophages were obtained from spent overnight dialysis fluid and normal ceils from patients undergoing laparoscopy. The ability of macrophages to ingest and kill S. epidermidis was measured by a radiometric assay in which incorporation of [3 H]-uridine into viable bacteria was used to determine these two parameters simultaneously. The degree of ingestion of a test dose of S. epidermidis by CAPD macrophages (81.6%) did not differ significantly from that of normal peritoneal macrophages (89.8%) but the proportion of ingested bacteria that were killed was reduced in CAPD cells (88.3% versus 99.9%, P < 0.001). Release of H 2 0 2 by CAPD macrophages following triggering with opsonised zymosan was determined and also found to be reduced (6.4 /zmol/10/~g DNA) in comparison with normal peritoneal macrophages (10.6 /~mol/10 /~g DNA: P < 0.01) but analogous to that found for