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When blood clots, elastase is released from granulocytes, which has fibrinolytic properties and which can probably digest fibrin deposits in areas of inflammation where coagulation may occur and granulocytes accumulate (1-4). In addition, this elastase e can inactivate coagulation factor IX (5, 6), fibronectin (7) a2-antiplasmin and C1-inhibitor (8) by proteolytic cleavage . It is therefore probably capable of modifying hemostatic responses particularly in the presence of inflammation .High molecular weight kininogen (HMW kininogen)' promotes blood coagulation (9-12) and can serve as a source of vasoactive polypeptides that can produce some of the components of the inflammatory response . Plasma from persons with an hereditary deficiency of HMW kininogen is severely deficient in coagulant properties attributable to this protein, and contact-initiated generation offibrinolytic activity in this plasma is markedly impaired (9-12) . Nonetheless, individuals with this hereditary deficiency do not have a hemorrhagic or an identifiable thrombotic disorder. Since bradykinin, a vasoactive peptide that can induce vasodilation, enhance vascular permeability, and cause pain, is part of the HMW kininogen molecule and can be released from the kininogen either by plasma kallikrein or plasmin (13-16), it was important to determine if granulocytes, which accumulate in areas of inflammation, could also release kinin as a result ofcleavage of HMW kininogen by granulocyte elastase . The following experiments show that a preparation of granulocyte elastase cleaved purified human HMW kininogen into multiple low molecular weight fragments and destroyed its clot-promoting activity, but did not release kinin from the molecule . Volume 167 June 1988 1895-1907 Materials and Methods Benzamidine and polyacrylamide were obtained from Eastman Kodak Company, Rochester, NY; Polybrene (hexadimethrine bromide) and trisodium EDTA were obtained from Aldrich Chemical Co., Milwaukee, Wl. QAE Sephadex A-50, SP Sephadex C-50, DEAESephadex A-50, and cyanogen bromide-activated Sepharose were all obtained from Pharmacia Fine Chemicals, Piscataway, NJ . DE-23 (diethylaminoethyl cellulose) was obtained

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Antigenic concentration of total kininogen, kinin liberated in vitro, and the antigenic concentration of high molecular weight (HMW) kininogen was measured in 58 different samples of cord blood plasma and in plasma samples from 67 healthy blood donors. Total kininogen and kinin concentration in cord blood plasma was more than twice as low as in pooled plasma of adult persons, and the concentration of HMW‐kininogen in cord blood plasma was close to one‐third of normal. The concentration of total kininogen and of HMW‐kininogen increased with age in adults. All. these findings were highly statistically significant.

Human umbilical vein endothelial cells (HUVECs) produce a property that impairs the generation of coagulant and amidolytic activity initiated when normal human plasma is exposed to glass. This inhibitory property blocks the adsorption of Hageman factor (factor XII) to glass, thereby preventing the activation of Hageman factor, but does not impair the coagulant or amidolytic activity of already activatedHageman factor (factor XIIa). This property in HUVEC lysates could be neutralized by a purified preparation of Hageman factor but not by purified prekaflikrein or high molecular mass kininogen. A partially purified inhibitory fraction from cell lysates exhibited a single homogeneous band in SDS/PAGE of -22.5 kDa. Inhibitory activity was also found in concentrates of conditioned media from HUVECs, which also impaired the binding of Hageman factor to a surface; it may not be identical with that found in cell lysates.Human blood plasma contains several proteins that can regulate the coagulation mechanism, thus helping to maintain the fluidity of the blood in vivo. Hageman factor (HF; coagulation factor XII) can generate coagulant activity and promote the release of vasoactive polypeptides. When HF is activated (factor XIIa) this balance may be upset, but the endothelial lining of blood vessels can facilitate the action of antithrombin III and limit the generation of clot-promoting activity (1-3). In addition, thrombomodulin, a component of endothelial cell membranes (4), can modify the action of thrombin so that it activates protein C and promotes fibrinolysis. In the experiments to be described a property was found in endothelial cells that impairs the activation of HF upon a glass surface, thereby blocking contact activation of the coagulation mechanism. A fraction of endothelial cell lysates that contained this property exhibited a single homogeneous band in SDS/PAGE analysis. The property was also found in conditioned media from endothelial cell cultures and may provide another mechanism for the regulation of clotpromoting activity.MATERIALS AND METHODS Materials. Materials for culturing and harvesting endothelial cells, including type I collagenase, preservative-free heparin (H-3125 at 10,000 units/ml), soybean trypsin inhibitor, and p-nitrophenyl phosphate (PNP), were from Sigma; L-glutamine, Hanks' balanced salt solution (HBSS), NuSerum, and endothelial cell growth supplement were from Collaborative Research. Hepes buffer came from GIBCO; penicillin/streptomycin mixtures were from Flow Laboratories; gentamicin was from Elkins-Sinn (Cherry Hill, NJ); trypsin was from Worthington. D-Prolyl-L-phenylalanyl-Larginine p-nitroanilide dihydrochloride (S-2302), from KabiVitrum (Stockholm) and Helena Laboratories, was dissolved in 0.02 M Tris buffered saline (TBS), pH 7.4, containing 0.15 M sodium chloride. Amidolytic activity was quantified by a minor adaptation of the method of Svendsen et al. (5), as described in the legends for figures and table.Antibodies. Antibodies to purified human HF were produced in a ...