Studies on the mechanism of hypersensitivity phenomena. III. The participation of complement in the formation of anaphylatoxin.

The interaction of fresh rat and guinea pig serum with washed preformed immune aggregates has been studied with respect to the loss in hemolytic potency of the serum, diminution of the C'(3); activity, and appearance of anaphylatoxin. It has been found that the formation of anaphylatoxin, as judged by its effect on capillary permeability and smooth muscle contraction, is coincident with or subsequent to the fixation of all the known C' components. Less anaphylatoxin is formed by aggregates formed with excess antigen than those in equivalence ratio combination.