Studies on the Role of Ca++ and Mg++ in Complement Fixation and Immune Hemolysis

The role of Ca++ in C′ fixation has been studied by two methods: 1) With a system depleted of divalent cations by passage through a resin, Ca++, but not Mg++, caused a marked enhancement in C′ fixation; 2) With a system containing EDTA as an inhibitory chelating agent, Ca++, but not Mg++, Sr++, or Ba++, restores C′ fixation. Therefore Ca++ is specifically required in C′ fixation.