THE ACTIVATING EFFECT OF MAGNESIUM AND OTHER CATIONS ON THE HEMOLYTIC FUNCTION OF COMPLEMENT.

1. The evidence presented indicates that Mg(++), or other cation such as Ca(++), Ni(++), or Co(++), is essential for the hemolytic action of C'. Ca(++), Ni(++), and Co(++) are less effective than Mg(++). The hemolytic system usually does not contain sufficient Mg(++) for optimal hemolytic activity so that a marked enhancement can be obtained by addition of extra Mg(++). 2. The enhancing action of tissue fluids can be ascribed to their contribution of Mg(++). 3. Substances which bind Mg(++) and Ca(++) are anticomplementary when added to the usual hemolytic system which contains only a small quantity of Mg(++). This type of anticomplementary effect can be overcome by addition of extra Mg(++). 4. Ca(++) may also be essential to the lytic process but its action is much less pronounced than that of Mg(++).