INHIBITION OF EXPRESSION OF MONOCYTE INTERLEUKIN-1 BY INHIBITORS OF HAGEMAN-FACTOR (FACTOR-XII)

In an earlier study, activated species of Hageman factor (factor XII) induced elaboration of interleukin-1 by human monocytes. These observa tions did not address whether Hageman factor participated in endotoxin -induced release of interleukin-1. To examine this question, the relea se of interleukin-1 by endotoxin-stimulated human mononuclear cells wa s measured in the presence of popcorn inhibitor, a specific inhibitor of Hageman factor. In the experiments herein described, popcorn inhibi tor sharply decreased the release of interleukin-1 by human mononuclea r cells that were incubated with endotoxin. This observation suggests that Hageman factor may play a role in the elaboration of interleukin- 1 by human mononuclear cells. Conforming with this view, the addition of antiserum directed against Hageman factor inhibited the release of interleukin-1 from endotoxin-stimulated mononuclear cells.