Hypersensitivity reactions during haemodialysis: role of complement fragments and ethylene oxide antibodies.

IgE-antibodies against ethylene oxide (EtO) and activation of the complement system have been suspected as causative factors for acute hypersensitivity reactions at the onset of haemodialysis. The present study was conducted to determine which of the two mechanisms is mainly responsible for the occurrence of reactions. According to clinical criteria, 13 of the 129 patients studied were identified as having suffered from at least one episode of acute hypersensitivity. Seven of them experienced severe symptoms, including five with elevated circulating serum EtO antibodies. Of the remaining six patients who experienced moderate symptoms, only one had elevated serum EtO antibodies, and of the 114 patients not exhibiting symptoms, two had enhanced serum concentrations of EtO antibodies. In-vivo complement activation was determined during haemodialysis by measurement of both C3adesarg and C5adesarg fragments. No differences in the onset levels and the degree of complement activation were found between patients suffering from severe, moderate, or no hypersensitivity reactions. In-vitro activation of the complement cascade by zymosan, measured in plasma samples obtained from patients prior to dialysis, revealed no differences in the extent of C3adesarg generation. Finally, we determined the activity of the C3a- and C5a-inactivating enzyme, carboxypeptidase N1 (CN1), in plasma samples of patients both with and without hypersensitivity reactions. No difference in the CN1 activity between the two groups of patients was found. These data lead us to conclude that sensitisation to ethylene oxide is responsible for the majority of severe hypersensitivity reactions in haemodialysis patients. However, a small subgroup of patients having anaphylactoid reactions displayed neither elevated serum EtO antibodies with excessive complement activation nor a tendency towards reduced inactivation of anaphylatoxins.