Complement activation profiles in disease.

Complement is an acute-reacting non-specific effector system. Activation and consumption of individual components of this multicomponent system occur secondarily to specific complement fixing events. The complement system is therefore an indirect and imprecise diagnostic tool and can be used clinically only as a general indicator of the severity of a particular disease or as a monitor of its progress. An exception is the case of the very rare inherited complement deficiencies where examination of the system does become directly diagnostic. The 11 proteins of the classical pathway, three additional ones of the alternative pathway, and three natural inhibitors can be measured either immunochemically using the appropriate specific antibody or functionally by the appropriate haemolytic assay. At present only a limited number of activation and consumption profiles can be considered to be clinically useful.