Abstracts of Papers Presented at the Third International Complement Workshop, Harvard Medical School, Boston, Massachusetts, June 3–5, 1968

Abstract

Abstract Active C′1s was purified from human serum by euglobulin precipitation, CM-cellulose chromatography, DEAE-cellulose chromatography, and Pevikon electrophoresis. Molecular weight of active C′1s is between 110,000 and 120,000. Highly purified active C′1s contains no C′1q and gives a single precipitin line in the α-globulin region against anti-whole human serum. This line was correlated with hemolytic and esterase activities. Moreover, the hemolytic activity and esterase activity of C′1s were correlated with C′2 and C′4 destructive activities. Although active C′1s forms SAC′4,2a, it does not bind to EAC′4gp at low ionic strength as does C′1a. Furthermore, kinetics of formation of SAC′4,2a with active C′1s exhibit a different pattern from that with C′1a, suggesting that active C′1s transfers from site to site. A convenient spectrophotometric assay system for esterase activity of active C′1s has been developed for these studies using p-tosyl-l-arginine methyl ester (TAMe) as a substrate.