In vitro activation of C1s in plasma of patients with hereditary angioneurotic oedema.

The serum of patients with hereditary angioneurotic oedema contains small amounts of inhibitor of Cl-esterase (Cl-s) which is usually present in appreciable amounts in the serum of healthy individuals. In the citrated plasma of these patients in remission Cl-s activity was not detectable, but prolonged incubation with various alcohols, detergents, acetone, phenols and metal chelating agents generated the enzyme. Normal plasma did not respond to these reagents. The generation of Cl-s by alcohol and EDTA was inhibited by addition of natural inhibitor of Cl-s but not by soyabean trypsin inhibitor, trasylol and hexadimethrine bromide. Hexadimethrine bromide did not block the generation when experiments were carried out in silicon coated glassware. Incubation with kaolin and kallikrein generated Cl-s in remission plasma. Density gradient centrifugation studies showed that alcohol caused at least partial dissociation of Cl in remission plasma but not in normal plasma. This effect was similar to that of EDTA described in earlier reports. The possible explanations for the findings are discussed.