Factors influencing the release of procoagulant-tissue factor activity from leukocytes.

Leukocytes stimulated with endotoxin generate a procoagulant (tissue factor) activity. Part of this procoagulant activity is released rapidly into the surrounding milieu, with maximum release occurring within 30 min incubation. Optimal release of procoagulant activity requires the presence of Ca ions in a concentration of 2.5 mM, a pH of 7-8, and a temperature of 37 degrees C. The released procoagulant activity is TFa as determined by the two-stage assay and the ability of an antibody to tissue factor to neutralize the procoagulant activity. The release of TFa is not parallel to LDH release. Release of TFa is inhibited by vinblastine and cytochalasin B.