Complement activation during subsequent stages of canine endotoxin shock.

Changes in total haemolytic complement and levels of C3, C4 and C6 were studied during subsequent stages of lethal endotoxin shock in dogs. Substantial decreases of all parameters were observed. C4 and C6 decreases showed a very similar pattern, indicating activation of complement by the classical pathway in addition to the activation of the alternative pathway known to occur in this pathological condition. The findings emphasize the role of the complement system in the pathophysiology of endotoxin shock and are consistent with the concept that complement activation has prognostic value during endotoxaemia.