CONTACT FACTORS ARE RESPONSIBLE FOR THE THROMBOGENICITY OF PROTHROMBIN COMPLEX

To determine the factors responsible for the thrombogenicity of [human] prothrombin complex (PC), preparagions of PC were prepared from normal plasma and from plasmas deficient in factor XII, factor XI, prekallikrein and high MW kininogen. PC isolated from normal or factor XI deficient plasma was thrombogenic unless the plasma was treated with kaolin prior to the isolation procedure. PC isolated from plasmas deficient in factor XII, prekallikrein or high MW kininogen were not thrombogenic even when the kaolin adsorption step was omitted. Factor XIIa activation of prekallikrein is apparently the initial reaction responsible for the thrombogenicity of PC.