[Blood serum antiplatelet activity in acute leukemia and idiopathic thrombopenia studied with the aid of the platelet factor 3 availability test].

The effect of the activity present in the globulin fraction of the serum of patients with acute leukaemias and thrombocytopenia on the isologous platelets was investigated. This activity caused, due to increased availability of platelet factor 3, an acceleration of the endogenous clotting pathway with resulting shortening of the clotting time in the test of platelet factor 3 availability. This test was done in 44 patients with acute leukaemia and 19 with thrombocytopenia demonstrating a high-grade shortening of the clotting time as compared with that in a group of 30 healthy controls. In some cases of complete remission of acute leukaemia an effect of this activity on the autologous platelets was demonstrated. The antiplatelet activity was inhibited by rabbit serum against human IgG and Fc fragment of the heavy chain in IgG. These results suggest that the activity present in the globulin fraction of the serum may be one of the causes of thrombocytopenia in acute leukaemia.