COMPLEMENT ACTIVATION BY CELLULOSIC DIALYSIS MEMBRANES

Aims-To assess the effect of cellulosic dialysis membranes on the prod uction of complement degradation products to determine to the role of the classical pathway. Method-Complement activation was studied in 33 patients during a single haemodialysis session using cellulosic membra nes. Pre- and post-dialysis plasma EDTA valves of C3, C4, C3dg, C4d an d C reactive protein (CRP) were measured. Statistical analysis was don e using the Wilcoxon signed rank test. Results-Post-dialysis C4 (p = 0 .0003), C3dg (p < 0.0001), and C4d (p = 0.003) concentrations were inc reased compared with pre-dialysis values. There was no significant cha nge in C3 (p = 0. 095) and (p = 0.13) values. Post-dialysis C3dg and C 4d concentrations correlated significantly (p = 0.007). IgG, an undial ysed molecule, was quantified and postdialysis valves were significant ly higher than those before dialysis (p = 0.0002), indicating a degree of haemoconcentration. To remove this effect, the C3:IgG, C4:IgG, C3d g:IgG, C4d:IgG and CRP:IgG ratios were calculated. Compared with pre-d ialysis values, post-dialysis C3dg:IgG and C4d:IgG ratios were increas ed and C3:IgG decreased significantly. No change was observed in C4:Ig G and CRP:IgG ratios. Conclusion-This study confirms that significant complement activation takes place following dialysis with cellulosic m embranes. This is denoted by an increase in C3dg. This was paralleled by a rise in C4d, implying a contributory role for the classical pathw ay. Concomitant post-dialysis increases in IgG and C4 indicate a degre e of haemoconcentration; but removal of this effect shows that C3dg an d C4d are increased following dialysis-suggesting classical, in additi on to alternative, pathway activation.