Function and physical properties of two distinct forms of the first component of guinea pig complement

Abstract

Both types of partially purified guinea pig C1 (first component of complement), prepared by solubility chromatography at low ionic strength and pH 7·5, are obtained in activated form. In contrast to C1 in whole serum, both produce linear dose response curves. The more soluble of the two, Type A, fails to bind to antigen-antibody complexes, is physically heterogeneous, and is smaller is size than the other, Type B. The evidence suggests that Type A, which cannot be detected in whole serum, arises by degradation during purification.