SummaryCoagulation studies were performed in 45 cases of nephrotic syndrome without uremia. The most striking features were an increase in the number of thrombocytes, and in the level of fibrinogen, factor V and factor VIII. Thrombin time was usually prolonged and the titre of antithrombin III was increased. No fibrin breakdown products were found in the serum. 13 patients developed thrombotic complications, with eventual death in 5 cases.

A procoagulant activity was found in the immature cells from patients with acute promyelocytic leukaemia. It was demonstrated that this activity was related to tissue factor. The protein component of tissue factor from brain extract was purified by Nemerson's technique and injected into rabbits to obtain anti-TF antibodies. Similar antibodies were produced against the promyelocyte extract. The anti-brain tissue factor antibodies neutralized the tissue factor activity of promyelocyte extract, and antibodies against immature cells were able to neutralize the tissue factor activity of human brain extract. In immunoprecipitation studies a reaction of partial identity appeared between one component of promyelocyte extract and one component of brain tissue factor. The data demonstrated that the promyelocyte procoagulant is antigenically related to brain tissue factor.

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SummaryIn order to investigate the mechanism of thrombin inactivation in the presence of both antithrombin III (AT III) and α 2-macroglobulin (α 2 M), thrombin and the inhibitors have been purified from human material and thrombin inactivation studied using purified reagents either alone or added to defibrinated plasma. Comparison of clotting and amidolytic activities of residual thrombin allowed to measure the amount of thrombin bound to α 2 M. In a purified reagent system as well as in plasma, part of exogenous thrombin is bound to α 2 M. The amount of bound thrombin is related to α 2 M concentration. Conversely, previous plasma α 2 M depletion by immunoabsorption increases the consumption of heparin-cofactor activity by exogenous thrombin. Thus AT III and α 2 M compete for thrombin inactivation. This finding could be of practical interest in clinical situations associating high plasma α 2 M levels and a decrease of AT III concentration.