Peripheral leukemic cells from a patient with acute promyelocytic leukemia (APL) were analysed for coagulant activity.
Suspensions of leukocytes were prepared by a modification of the method of Böyum. Washed preparations were disrupted by freezing and thawing six times and homogenized by a Potter-Elvenhjem apparatus 0.34 M sucrose solution.
Lysate of these leukemic cells significantly shortened the recalcification time and activated PTT in normal human plasma. Clot was formed in a time of 49 sec. when 0.1 m
l of lysate (WBC: 150,000/mm
3) was added into prothrombin time system, instead of tissue thromboplastin but not formed when it was added into thrombin time system instead of thrombin. These leukemic cells also shortened clotting time with factor VIII and factor IX deficient plasma, however not with factor II, factor V or factor VII complex deficient plasma. The activity was destroyed almost completely after heating for 120 min. at 56°C and 80°C.
The results suggest that this procoagulant activity has a characteristics of tissue thromboplastin. Approximately 1.5×10
7 leukemic cells has a thromboplastic activity of 0.2 mg of rabbit lung tissue thromboplastin (Lyoplastin). Small amount of sodium heparin could inhibit this activity in vitro.
No significant procoagulant activity was detectable in the leukemic cells from a patient witn AML or CML, or in normal leukocytes.
These data suggest that leukemic cells of APL has a significant quantity of thromboplastic activity and could be involved in the pathogenesis of disseminated intravascular coagulation of this disease.
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