The ability of antisera to guinea-pig C3 to inhibit the Arthus and local Shwartzman reactions was studied. They were found to reduce the non-haemorrhagic component of the active and reversed passive Arthus reactions and to delay the appearance of the haemorrhage in the active Arthus reaction. Cobra venom factor, however, had no effect on the non-haemorrhagic components of these reactions and only delayed the appearance of the haemorrhage of the active Arthus reaction. There appeared to be a correlation between the serum complement level and the time taken for the haemorrhage to appear, and between the circulating platelet count and the extent of the non-haemorrhagic, oedematous component of the reaction. The haemorrhagic component of the local Shwartzman reaction was not affected by decomplementation with cobra venom factor. The ability of the antisera to inhibit the haemorrhage of the Shwartzman reaction was not dependent on lowering the serum complement titre. However, the haemorrhage was inhibited if the circulating platelet count was also reduced to very low numbers. Antiserum to zymosan alone had the same effect as anti-beta1C/beta1A globulin (zymosan) in blocking the reaction, although it did not alter the complement levels or the platelet counts. The possibility of an immunological cross-reactivity between zymosan and endotoxin in this action is discussed.
Animals Antibodies