THE RELATIONSHIP BETWEEN THE BINDING ABILITY AND THE RATE OF ACTIVATION OF THE COMPLEMENT COMPONENT-CL

Abstract

The strength of the bond between Cl [complement component] and Cl binders (as measured by Clq binding ) was correlated with the ability of the binders to activate Cl. The rate of activation of Cl was studied by following the extent of hydrolysis of the Clr and Cls subcomponents, using a purified preparation of [human] Cl labeled with 125I. The rate of activation of Cl was not correlated with the binding strength between Clq and the Cl binders. Immune complexes activate Cl rapidly; glutaraldehyde-aggregated IgG failed to activate faster than the spontaneous activation seen on incubation of Cl alone; the strength of the bond between Clq and the binders was similar in the 2 cases. An interaction other than the binding between Clq and Cl binders probably is necessary for activation of Cl. Cl bound to immune complexes was not activated in the presence of Cl inhibitor, indicating that the inhibitor can prevent the hydrolysis of Clr under the test conditions.