Cellulose membranes suppress complement activation in patients after hemodialysis

Membranes used for dialysis therapy activate complement. Complement activation is maximal after initiating dialysis and returns to predialysis values by the end of dialysis. No changes in C3 levels have been detected after dialysis. We hypothesized that although C3 levels were unchanged, C3 activity could be altered by dialysis. We measured complement activation in vitro in serum from patients randomized to dialysis treatments using different types of membranes. The classical pathway was activated with aggregated immunoglobulin G (IgG), and the alternative pathway was activated with inulin. Both the classical and alternative pathways were suppressed after dialysis using cellulose membranes (aggregate IgG, P < 0.01; inulin, P < 0.001). When polyacrylonitrile (PAN) or polyethylene glycol grafted cellulose membranes were used for dialysis, only minor suppression of complement pathways was measured. Levels of the control factor SP-40,40 increased at later times for dialysis using cellulose membranes (P < 0.05). Factor H levels were also greater after dialysis using cellulose membranes compared with PAN membranes (P < 0.05). In summary, cellulose membranes suppress complement activation in serum. One suppressing factor may be the complement control factor SP-40,40.