First -Line Defense Mechanisms in the Peritoneal Cavity during Peritoneal Dialysis

B acterial peritonitis remains one of the major problems in patients with end-stage renal fail ure undergoing peritoneal dialysis (PD). Besides the increased risk of microbial contamination of the peritoneal cavity via the peritoneal catheter (either intraluminal or periluminal passage), the high prevalence of peritonitis in PD patients may also be due to a reduced host resistance. Indications for defects in host defense mechanisms are the relatively avirulent nature of the bacteria that commonly cause peritoneal dialysis-related peritonitis (1) and the finding that some microorganisms such as coagulase-negative staphylococci may survive and grow within PD-derived peritoneal macrophages (2). Both systemic and intraperitoneal host resistance may playa role in the development of infectious peritonitis. Systemic host resistance is influenced by multiple factors including uremia (3,4), diabetes, malnutrition, age, blood dyscrasias, and immunosuppressive therapy. In this article we will focus on the intraperitoneal host resistance during peritoneal dialysis. Both cellular and humoral aspects of host defense mechanisms in the peritoneal cavity will be discussed. To elucidate the influence of peritoneal dialysis on host resistance, we will compare the different aspects of the defense mechanisms in the peritoneal cavity during dialysis with those in a normal situation. FIRST-LlNE DEFENSES It has been reported that even in PD patients, contamination of the peritoneal cavity does not always lead to clinical peritonitis (5,6). Whether a