IGG SUBCLASSES IN CAPD PATIENTS

Objective: To make a comparison of serum levels of immunoglobulin G (I gG) subclasses in adult continuous ambulatory peritoneal dialysis (CAP D) patients with those in age-and sex-matched hemodialysis patients an d healthy volunteers, and to analyze the contribution of removal of th ese proteins in peritoneal effluent to their plasma values. Design: A cross-sectional study. Setting: A renal unit of it university hospital . Patients:Twenty-three CAPD patients, 21 hemodialysis patients, and 2 1 healthy volunteers. Peritoneal transport studies were done in 8 of t he 23 CAPD patients. Methods: IgG subclasses were measured in serum by nephelometry. For the peritoneal transport studies an ELISA method on ethylenediamine tetracetic cid plasma was used. The same method was u sed in seven-to ten-fold concentrated peritoneal dialysate. Results: C APD patients had lower IgG2 and IgG4 levels than hemodialysis patients and healthy volunteers (p < 0.01). IgG2 values below 1.5 g/L were pre sent in 43% of the CAPD patients (p < 0.001 compared to healthy volunt eers). Peritonitis incidence was not different between CAPD patients w ith low or normal IgG2 plasma levels. Peritoneal clearance of IgG3 was lower than that of the other subclasses. Evidence was obtained for a depressed synthesis of IgG2 and IgG4 in CAPD patients. The hypothesis that interleukin-2 may be involved in the law synthesis rate of IgG2 i s discussed. Conclusion: Low serum IgG2 and IgG4 levels are present in stable, adult CAPD patients. These were not caused by increased perit oneal loss, but by decreased synthesis.