Assembly of terminal SC5b-9 complement complexes: a new index of blood-membrane interaction.

Activation of the complement system during the course of hemodialysis was recognized more than 20 years ago and since then the generation of C3a and C5a desarg has been used as parameters of blood-membrane interaction. More recently, determination of terminal C5b-9 complement complexes has become feasible. In the present study we determined plasma concentrations of C5b-9 complexes during hemodialysis using Cuprophan or Hemophan membranes. As early as 10 min into dialysis, Cuprophan membranes led to higher arterial plasma concentrations of C5b-9 complexes in comparison to Hemophan-containing devices. With Cuprophan, systemic arterial peak values of 237 +/- 27 U/ml were reached 45 min after the onset of dialysis, while corresponding peak values using Hemophan were only 58 +/- 16 U/ml. Venous concentrations of C5b-9 complexes, measured at the outlet of the dialyzer, were 489 +/- 102 U/ml with Cuprophan and 77 +/- 19 U/ml with Hemophan dialyzers. As an index of red cell lysis, plasma levels of free hemoglobin were evaluated. There was hemolysis with both membranes. Free hemoglobin levels increased threefold with Cuprophan and only twofold with Hemophan membranes. Taken together, plasma concentrations of C5b-9 complexes clearly discern between dialysis membranes of high or low compatibility. The fact that there is simultaneous lysis of red cells might indicate that deposition of C5b-9 complexes on innocent cells occurs which would lead subsequently to an array of diverse pathophysiological reactions.