363 Friday 20 July 1979 VII INT. CONGo THROMB. HAEM. Free Communications Time 10.15 0864 COMPARISON OF THE HUMAN ACTIVATORS OF PLASMINOGEN M. Mackie*, N. Booth, B. Bennett, Department of Medicine, ,Aberdeen University, Aberdeen, Scotland. Detailed information is available on the molecular characteristics of plasminogen and plasmin. In contrast, few data have been obtained on the number and nature of agents which activate plasminogen in the body. We describe the purification and characteristics of (1) a plasminogen activator present in venous Dlood after venous occlusion - "circul­ ating activator", (2) a plasminogen activator generated from plasma by contact with kao­ lin - "Hageman factor dependent activator", (3) a plasminogen activator precipitated from plasma by dextran sulphate - "dextran sulphate dependent activator", (4) a plasmin­ ogen activator obtained from cadaveric vascular endothelium - "cadaveric endothelial act­ ivator and (5) a plasminogen activator extracted from human heart tissue - "tissue activ­ ator". The properties of these activators are compared with one another and with urokin­ ase obtained commercially. The physical properties of activators 1-5 appeared similar though on Sephadex G200 the dextran sulphate dependent activator eluted at a position suggesting a larger molecular size than the other activators. The susceptibility of these activators to enzyme inhibitors were identical but differed from that of urokinase. Anti­ sera to urokinase did not inhibit the activity of these activators. Antisera to the cad­ averic endothelial activator did not inhibit urokinase or the Hageman factor dependent activator but did inhibit the activity of activators 1,3,4 and 5. Factor IX: Clinical and Experimental Hungerford Room 09. 00 0865 A RADIOlt+1UNOASSAY FOR FACTOR IX (F. IX) USING STAPH A R.M. Lewis*, H.M. Reisner, R.L. Lundblad, K.S. Chunq and H.R. Roberts, Departments of Pathology and Medicine, University of North Ca \'olina, Chapel Hill, North Carolina, U.S.A. A recently described radioimmunoassay for antibodies to F.IX uses StathYlocOCCUs aureus to specifically precipitate the antibody and bound 125 1 labeled F.IX Lewis et al. Fed. This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited. Proc. 1979). This method has now been extended to allow for the measurementlOf-r.I--X-­ antigen by inhibition of the binding of 125I_F.IX to alloantibodies. Purified F.IX as well as F.IX in plasma can be measured with high sensitivity (plasma dilutions to 1:2560). This assay was used to characterize hemophilia B plasmas as CR~, containing normal levels of F.IX antigen, or CRM-, containing severely reduced levels of F.IX an­ tigen. Classification was in agreement with results obtained by inhibitor neutraliza­ tion using a different alloantiserum. No detectable antigenic differences were observed between normal F.IX, activated normal F.. IX (F.IXa) and two abnormal, highly purified F.IX proteins in this assay. These data indicate the usefulness of the assay for the determination of the antigenic specificity of alloantibodies. .