Tissue factor (TF) antigen and activity were measured in leukemic cell homo
genates. In leukemic cell homogenate, especially that of acute promyelocyti
c leukemia (APL), both TF antigen and activity were significantly higher th
an these levels in the mononuclear cells obtained from healthy volunteers.
Both TF antigen and activity were significantly higher in myelocytic leukem
ia than in lymphocytic leukemia cells. In leukemic cell homogenates, there
was a close correlation between TF antigen and TF activity. The TF activity
/TF antigen ratio was significantly higher in myelocytic leukemia than in l
ymphocytic leukemia cells. As the TF activity was not increased in lymphocy
tic leukemia cell homogenates to which were added phospholipids, the decrea
se in TF activity in lymphocytic leukemia might not be due to phospholipid
in the leukemic cell membrane. Values for TF activity, TF antigen, and the
TF activity/TF antigen ratio in leukemic cell homogenate from patients with
disseminated intravascular coagulation (DIC) were significantly higher tha
n these in patients without DIG. Therefore, the measurement of TF antigen a
nd activity in leukemic cells could be useful for the prediction of DIG.