Differentiation between formation,in plasma,of anaphylatoxin and of endogenous pyrogen

Summary Two anaphylatoxin-forming agents have been investigated with respect to possible pyrogenic effects: the AT forming fraction of cobra venom and agar.The cobra venom fraction produced fever in rabbits. The pyrogenic principle is, however, not identical with the AT forming enzyme. Unlike the latter the pyrogenic principle is stable in acidic solution and destroyed by periodate. It may be a lipopolysaccharide.Rabbit plasma, incubated with agar caused fever in rabbits. Agar also induced pyrogenic activity in saline after it had been incubated in that medium. The active principle proved to be agaropectin, the water-soluble acidic fraction of agar. Agarose was inert. In contrast, anaphylatoxin formation is induced by agarose, not by agaropectin.In rabbit plasma, agaropectin induces the formation of an endogenous pyrogen. This principle can be separated from the agaropectin by DEAE cellulose chromatography. It is further distinguished from the latter by being heat-labile.Besides being activated by different agents the processes of pyrogen and AT formation differ in their requirement for cations. AT formation is blocked by EDTA but pyrogen formation is not. It is concluded that in spite of similarities and common activation by endotoxins the processes of AT and pyrogen formation are different and independent events.