IgG glycation and function during continuous ambulatory peritoneal dialysis

IgG in dialysate may have an important role in anti-infection mechanisms during continuous ambulatory peritoneal dialysis (CAPD). As Fc fragment oligosaccharidic chains are crucial for IgG effector functions, we have tested the hypothesis that IgG glycation might occur during CAPD and modify IgG properties. Purified normal IgG was incubated with glucose solutions of different concentrations and pH. Separation of glycated IgG was performed by affinity chromatography. Complement activation (C3c deposition) and phagocytosis by polymorphonuclear leucocytes (PMN) were studied in vitro using Staphylococcus aureus Wood (STAW) as antigen. In addition, we compared the percentages of glycated IgG in IgG purified from sera and dialysates of 12 CAPD patients. The percentage of glycated IgG after in vitro incubation of normal IgG with glucose solutions was directly proportional to glucose concentrations, incubation time and pH. Glycated IgG anti-STAW induced a higher C3c deposition than non-glycated IgG anti-STAW (C3c/IgG (mean +/- SD) 0.96 +/- 0.06 vs 0.79 +/- 0.08; P = 0.027). PMN phagocytosis was not affected by IgG glycation. The percentages of glycated IgG in dialysates of CAPD patients were greater than those in corresponding sera (5.38 +/- 2.36% vs 4.56 +/- 2.47%; P = 0.006). It is concluded that IgG glycation may take place in the peritoneal cavity during CAPD and lead to enhanced complement activation. This could explain the high degree of complement activation previously described in dialysate of CAPD patients and might theoretically result in a reduction of complement factors available in dialysate for adequate anti-infection mechanisms.