1. The generation of the plasma SC5b—9 complex (the soluble form of the membrane attack complex) during haemodialysis was studied in 29 patients together with markers of the classical (C4d fragment) and alternative (Bb fragment) pathways and the common iC3b fragment.
2. In the patients dialysed with Hemophan and Cuprophan membranes, a rapid increase in the plasma levels of SC5b—9 complex, Bb fragment and iC3b fragment occurred within 15 min of the initiation of the haemodialysis procedure. The SC5b—9 complex and the Bb fragment concentrations remained at a plateau until 120 min thereafter. The iC3b fragment level showed a continual decline.
3. The C4d fragment concentrations remained unchanged, indicating that generation of the membrane attack complex is most likely due only to activation of the alternative pathway.
4. The generation of the membrane attack complex occurred throughout the full haemodialysis period. In patients treated with Polysulfon membranes no statistically significant variation in these components was noted.
5. The study shows that the membrane attack complex may be generated during the full period of the haemodialysis session and is a stable index of biocompatibility.
6. Moreover, it seems be involved directly in haemodialysis-associated phenomena.