Lipopolysaccharide-binding protein is present in effluents of patients with Gram-negative and Gram-positive CAPD peritonitis

Background: Bacterial peritonitis is a frequentcomplication during treatment of end-stage renal failure by continuousambulatory peritoneal dialysis. Local host defence mechanisms including thesecretion of proinflammatory cytokines by peritoneal macrophage are ofparticular importance in the pathogenesis of infectious complications.LPS-binding protein (LBP) and soluble CD14 (sCD14) are serum factors knownto regulate the endotoxin-induced cellular immune response. However, it isstill unknown whether LBP and sCD14 are also present in the peritonealeffluent of CAPD patients. Methods: Using specificimmunoassays, we examined the concentration of LBP, sCD14 and theproinflammatory cytokines TNF=&agr;, IL-1{beta} and IL-6 in thedialysis effluents of 31 patients with CAPD-associated peritonitis. Twentypatients without peritonitis served as controls. Intraperitoneal LPSconcentrations were determined using the limulus amebocyte lysate assay. Results: Bacterial lipopolysaccharide could bedetected in 42% of the infected dialysis effluents. In comparison tocontrols (0.2±0.05 &mgr;g/ml), LBP was significantlyelevated in both Gram-negative/LPS-positive (1.03±0.3&mgr;g/ml) and Gram-positive infections (0.5±0.14&mgr;g/ml) (P<0.05). No significant differences were detectedconcerning the intraperitoneal sCD14 levels in the three patient groups.Levels of TNF-&agr;, IL-1{beta} and IL-6 were significantlyincreased in the effluents of patients with bacterial peritonitis comparedto non-infected controls. Moreover the respective cytokine concentrationswere significantly higher in the Gram-negative/LPS-positive compared to thegram-positive bacterial infections (P<0.01).Conclusion: Our data demonstrate that LBP issignificantly elevated in the dialysis effluents of patients withCAPD-associated peritonitis caused by both Gram-negative and Gram-positivebacteria and might be used as a marker of intraperitoneal infection.Moreover, our findings support the concept that LBP enhances the effects ofLPS on cytokine production by peritoneal macrophages. The function of LBPin Gram-positive infection remains to be further elucidated. Keywords: CAPD-associated peritonitis; cytokines;lipopolysaccharide-binding protein; macrophages; peritoneal dialysis;soluble CD14