Effects of phytosterols on anti-complementary activity.

Several phytosterols, stigmasterol, campesterol and ƒÀ-sitosterol, were shown to have potent anti-complementary activities. Stigmasterol was the most potent. A marked consumption of C4 was observed to have occurred when serum was incubated with these phytosterols, and ƒÀ-sitosterol and stigmasterol showed higher C4 consumption than campesterol. After the incubation of serum with these phytosterols in the absence of Ca2+ ions, cleavage of C3 in the serum was detected by immunoelectrophoresis. Stigmasterol caused greater C3 cleavage than the other two com-