Intradermally injected preparations of purified Cls̄ and polypeptide from plasma of persons with hereditary angioneurotic edema (HANE) induced venular lesions with ultrastructural changes of the endothelium similar to changes induced by histamine (1). Treatment of test animals with an antihistaminic did not block increased vascular permeability about injections of HANE polypeptide or bradykinin. Animals depleted of C3 demonstrated decreased change in vascular permeability about injections of Cls̄, but responses to histamine, bradykinin and HANE polypeptide were not blocked. Patients with HANE excreted larger amounts of histamine in their urine than normals; this increase was most pronounced as an epidsode of edema was subsiding.
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