FIG 2.

Spontaneous activation of the bradykinin-forming pathway in patients with HAE-N compared with patients with HAE type I and control subjects (A) and inhibition of activation by using C1-INH (B). Plasma was diluted 1:2 with HEPES-buffered saline and incubated at room temperature, and kallikrein activity was measured by using a chromogenic substrate (S2302; diaPharma, West Chester Township, Ohio). About half of the samples from patients with HAE-N were activated at 1:2 dilution, and the curves looked similar. Thus a representative profile is shown. For inhibition studies (Fig 2, B), selected plasma samples with spontaneous activation (8 samples, 4 from each group) were incubated in the presence of 100 μg/mL purified C1-INH, and kallikrein activity was measured after 1 hour. FXII, Factor II.