The procoagulant factor of leukaemic promyelocytes: demonstration of immunologic cross reactivity with human brain tissue factor.

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.