Action of Complement in Hereditary Angioneurotic Edema: The Role of C′1-Esterase *

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Abstract
Normal serum inhibitor of the enzyme derived from the first component of complement (C''1 esterase) was undetectable in hereditary angioneurotic edema and this deficiency was apparently inherited as an autosomal dominant trait. The tendency to generate C''l esterase from C''l proesterase was enhanced in serum obtained during attacks of edema and C''4 and C''2 were not measureable. C''3 was not decreased and its electrophoretic mobility was unaltered. Some inactivation of C''4 occurred in vivo even between attacks reflecting activation of C''l esterase. Activation of C''l did not require dissociation of the C''1 macromolecule. C''1 esterase may act to intiate increased vascular permeability during attacks of hereditary angioneurotic edema.