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PubMed1978

Synthesis of procoagulant antihaemophilic factor in vitro.

The cells which produce the procoagulant part of antihaemophilic factor (factor VIII-C) in normal people have remained unknown. Normal blood leucocytes cultured in vitro with phytohaemagglutinin synthesised a procoagulant with the properties of factor VIII-C. The procoagulant was inhibited by human VIII-C inhibitor and itself absorbed human VIII-C inhibitor--properties which are regarded as specific for factor VIII-C. Unexpectedly, cultured leucocytes from haemophiliacs also synthesised the procoagulant in similar amounts. Possible explanations and implications of these findings are briefly considered.

Anticoagulants↗
PubMed1987

Inhibitors of coagulation in children.

Acquired inhibitors of coagulation factor interaction in nonhemophilic children are usually nonspecific, transient, and unassociated with clinical bleeding. They occur with some frequency and are the most common cause for a prolonged APTT found by routine testing. In children, some association with viral infections and treatment with penicillin has been noted, but their interrelationship with the development of antibodies remains unclear. The exact nature of these antibodies, usually directed against coagulant factor phospholipid, is not clear and multiple antibodies both specific as well as nonspecific may occur. No therapy is generally required. Rarely has the acute development of antibodies directed against specific coagulation factors occurred. The laboratory evaluation of the type of inhibitor is, therefore, most important as specific inhibitors may be associated with life-threatening bleeding situations. Their therapy should probably include attempts at eradication of the inhibitor by immunosuppressive agents or other newer modalities. Unfortunately, little information is available regarding the nature and outcome of specific inhibitors in children. Acquired inhibitors in hemophilic patients occur in about 6 to 10% of patients. Newer approaches to their therapy include activated PCC which have generally improved the outlook for such patients. Treatment regimens involve a knowledge of inhibitor response and the concomitant use of plasmapheresis, high-dose or continuous i.v. Factor VIII, and porcine Factor VIII, followed by activated PCC. The role of immunosuppressive agents and other newer modalities appears promising, however, prospective controlled studies are necessary to evaluate their role in the overall management of such patients.

Autoimmune Diseases↗
PubMed2006

Mechanism of action of recombinant activated factor VII: an update.

Bleeding episodes in patients with hemophilia and inhibitors must be managed using agents that are hemostatically active in the absence of factor VIII or IX. Activated prothrombin complex concentrates have long been used in this context. However, the search for safer and more effective agents has led to the development of recombinant activated factor VII (rFVIIa; NovoSeven, Novo Nordisk, Bagsvaerd, Denmark). This paper presents an update on the mechanism of action of rFVIIa, and describes how pharmacologic doses of this agent enhance thrombin production and thus contribute to the development of a stable, lysis-resistant fibrin plug at the site of vessel damage. This mechanism explains the reported efficacy of rFVIIa in a range of clinical situations characterized by impaired thrombin generation.

Blood Coagulation↗
PubMed1970

Human plasma alpha 2-macroglobulin. An inhibitor of plasma kallikrein.

Activation of plasma kallikrein arginine esterase activity by kaolin resulted in peak activity at 1 min of incubation and a 50% reduction in activity at 5 min in normal plasma, and 30% reduction in the plasma of patients with hereditary angioneurotic edema who lacked the C1 inactivator. The peak esterolytic activity was inhibited by soybean trypsin inhibitor whereas the 5 min activity was resistant to this inhibitor. Acid treatment of normal and hereditary angioneurotic edema plasma destroyed the factor responsible for the fall in esterase activity at 5 min and the factor which rendered the esterase resistant to soybean trypsin inhibitor. Purified alpha(2)-macroglobulin inhibited approximately 50% of the TAMe esterase activity of purified plasma kallikrein without changing its activity toward basic amino acid esters. The interaction between the alpha(2)-macroglobulin and kallikrein resulted in alterations in the gel filtration chromatographic pattern of the TAMe esterase and biologic activity of kallikrein, indicating that kallikrein was bound to the alpha(2)-macroglobulin. The TAMe esterase activity of this complex, isolated by column chromatography, was resistant to C1 inactivator and SBTI. Studies of incubation mixtures of kallikrein, alpha(2)-macroglobulin and C1 inactivator suggested that these inhibitors compete for the enzyme, and that the alpha(2)-macroglobulin partially protects the esterase activity of kallikrein from C1 inactivator. The alpha(2)-macroglobulin isolated from kaolin-activated plasma possessed 240 times the esterolytic activity of the alpha(2)-macroglobulin purified from plasma treated with inhibitors of kallikrein and of its activation. The alpha(2)-macroglobulin blocked the uterine-containing activity and vascular permeability-inducing effects of plasma kallikrein. These studies suggest that the alpha(2)-macroglobulin is a major plasma inhibitor of kallikrein and provide a new example of an interrelationship between the coagulation, fibrinolytic, and kallikrein enzyme systems.

Alpha-Globulins↗
PubMed1981

Hereditary hemorrhagic telangiectasia and disseminated intravascular coagulation: a new clinical syndrome.

In summary, 47 patients with documented HHT and a bleeding problem were referred to San Joaquin Hematology Oncology Medical Group over a 2-year period. Fifty-one percent of patients were noted to have an associated DIC syndrome and of these 24 patients, 19 had acute DIC episodes, six had chronic DIC, six presented with diffuse, recurrent deep venous thrombosis and of these six, three suffered pulmonary emboli. Other defects were also noted and were thought to be coincidental defects. This syndrome should be readily considered and searched for when seeing patients with HHT, especially if significant hemorrhage or thrombosis is present. It should further be appreciated that many patients with HHT and bleeding are candidates for the development of acute or chronic DIC and thus a "mini" Kasabach-Merritt syndrome. When patients with HHT present with undue bleeding, this syndrome should be appreciated, searched for from the clinical and laboratory standpoint and, when found, treated in the appropriate manner with supportive therapy, mini-heparin or antiplatelet therapy as the clinical situation dictates.

Acute Disease↗
PubMed1992

Acquired factor XI inhibitor in chronic lymphocytic leukaemia.

A 71 year old man with chronic lymphocytic leukaemia (CLL) experienced excessive bleeding following transurethral resection of the prostate. Investigations showed a prolonged kaolin cephalin clotting time (KCCT) with low concentrations of factor XI. The prolonged KCCT was largely corrected by mixing with normal plasma but this correction was lost on incubation, confirming the presence of an inhibitor. He was treated with pulsed methylprednisolone and chlorambucil which resulted in the resolution of the bleeding problem and the loss of detectable circulating inhibitor.

Aged↗