A plasma factor inhibiting prostacyclin-like activity in thrombotic thrombocytopenic purpura.

The plasma from a patient with thrombotic thrombocytopenic purpura contained a low molecular weight dialysable factor which inhibited the synthesis and release or activity of prostacyclin-like activity from vascular tissue. This factor was not an immunoglobulin or complement component. Following fresh plasma infusions the ability of the patient's plasma to stimulate the release of prostacyclin-like activity returned but no clinical improvement occurred.