Serum Soluble CD14 Levels and Ultrafiltered Dialysate in Hemodialysis Patients

Ryoichi Nakazawa, MD, Department of Nephrology, Tokatsu Clinic Hospital, 822 Hinokuchi, Matsudo 271 (Japan) Dear Sir Endotoxin (lipopolysaccharide, LPS) exists in the dialysate and is closely associated with the pathophysiology of dialysis-related amyloidosis [1]. LPS binds to LPS-binding protein (LBP), and the complex binds to CD 14 on the surface of mature monocytes. CD 14, the receptor of this LPS-LBP complex, is released into the blood and becomes soluble CD 14 (sCD14). sCD14 inhibits binding of the LPS-LBP complex to membrane-bound CD 14, thereby neutralizing LPS. sCD 14 has a role in the LPS-dependent activation of endothelial and epithelial cells [2]. We measured serum sCD14, hyaluronic acid, and dialysate LPS in hemodialysis patients in order to evaluate their association with dialysis-related amyloidosis. One hundred and three patients (57 men and 46 women, mean age 60.4 years) with chronic renal failure participated in the study. They were undergoing maintenance hemodialysis for more than 3 months (mean length of dialysis: 84.8 months, range 3-266) thrice weekly, 4 h/session. Cuprophane (n = 54), cellulose acetate (n =16), ethylene/vinyl alcohol (n = 8), polymethyl methacrylate (n = 11) or high-flux (n = 14) membranes were used prior to the study. Nine continuous ambulatory peritoneal dialysis (CAPD) patients were also enrolled in the study. The dialysate was either untreated or ultrafil-tered using 1 or 2 polyethersulfone filters for 15 months. The subjects were divided into groups as follows: group 1, 23 patients, dia-lysed with ultrafilters after sessions on a reverse-osmosis unit and a central supply unit; group 2, 26 patients, dialysed with an ultrafilter after sessions on a reverse-osmosis unit, and group 3, 54 patients, treated with regular dialysate. For bacteriological testing, a 50-ml sample of the dialysate was cultured on nutrient agar plates at 30 o C for 3-7 days. Endotoxin levels of the dialysate were measured using Endospecy, an endotoxin-spe-cific chromogenic limulus test reagent [3]. sCD14 levels were determined by enzyme immunoassay [4]. Hyaluronic acid was measured using a sandwich binding protein assay [5]. The predialysis sCD 14 level was significantly higher in the dialysis patients, and in 79.6% of the cases it exceeded 6 μg/ml. No correlation was observed between the sCD14 level and the level of hyaluronic acid or the duration of hemodialysis. No significant difference of sCD 14 was seen between groups with and without dialysis-related amyloidosis. The high levels of