Activation of rabbit serum protease by dextran sulphate

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. C' fixation, as well as anaphylatoxin production, may be inhibited by chelation of the divalent cations, presumably by interfering with the fixation of C'₁, C'₄, and C'₂. Phlorizin suppresses the utilization of C'₃ in immune hemolysis, C' fixation by antigen-antibody aggregates, and the production of anaphylatoxin. The biological activities associated with the fixation of C' are not manifest unless C'₃ participates in this process at 37°C. It is concluded that the formation of anaphylatoxin may be regarded as a product of C' fixation.

Specific and nonspecific channels leading to proteolysis in antibody preparations

Current ways of fractionating immune sera give rise in the guinea-pig species to an active plasmin that contaminates antibody preparations. The enzyme appears as a free molecule separable from the immunoglobulin. In contrast, when a purified antibody has been obtained through the immunoabsorption process, plasmin activated during the contact between antibody and polymer binds firmly to the immunoglobulin. This phenomenon occurs separately and indistinctly with IgG1 and IgG2. Moreover, the alternate pathway of complement activation could be a tributary to the plasmin system.