THE INFLUENCE OF CALCIUM IONS ON THE INACTIVATION OF HUMAN COMPLEMENT AND ITS COMPONENTS BY PLASMIN

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Abstract
Ca++ potentiates the inactivation of human complement by streptokinase-aciivated plasmin and chloroform-activated bovine plasmin. The optimum concn. of Ca++ varies between 10-2 [image] and 10-3 [image], decreasing with increasing concns. of streptokinase. The susceptibility of the components of complement to inactivation by plasmin is different in the presence and absence of Ca++. C''2 and C''4 are most readily inactivated by plasmin in the presence of Ca++, while C''l disappears first in the absence of Ca++. A large part of this C''l disappearance is due to spontaneous inactivation. Similarities are pointed out between the influence of Ca++ on the inactivation of the components of complement by antigen-antibody systems and by plasmin.