Appearance of a substance in acute phase serum which elicits Cx-protein responses.

Seromucoid was isolated from serum of rabbits during the acute inflammatory period following subcutaneous injection of an irritant and at times after whole body irradiation. It produced a Cxprotein response on intravenous injection into normal rabbits, an anamnestic response in immunized rabbits, leucocyte changes characteristic of inflammation, and marked toxicity in rabbits with reticuloendothelial system blockade. Normal seromucoid did not possess these properties.