An analysis of functional activity via the three complement pathways during hemodialysis sessions: a new insight into the association between the lectin pathway and C5 activation

BACKGROUND We have recently demonstrated that hemodialysis (HD) patients have significantly higher levels of functional complement activity (FCA) in all three pathways, i.e. the classical pathway, alternative pathway and lectin pathway (LP), than in age-matched controls, though the role of FCA during HD still remains unknown. METHODS Serial plasma or serum samples were obtained from five patients during HD in order to investigate the kinetics of complement components. The levels of the C5b-9 complex, the FCA of the three pathways, a derivative of C3a (C3a desArg) and a derivative of C5a (C5a desArg) in the samples were analyzed. RESULTS The levels of the C5b-9 complex at 60 min were significantly increased when compared with those at 0 min. Functional activities for all three pathways showed different patterns so the same tendency between pathways was not observed. The levels of C3a desArg and C5a desArg at 60 min were markedly increased when compared with those at 0 min. A Spearman's rho test showed a strong positive correlation between functional LP activity and C5a desArg. CONCLUSIONS These findings lead to new insights into the FCA during HD and suggest that functional LP activity has an important role in C5 activation.