Abstract
To evaluate the relationship between the tissue factor (TF) pathway and lupus anticoagulant (LA), in the pres ent study, we measured the plasma levels of TF antigen and TF pathway inhibitor (TFPI) antigen in patients positive for LA. Plasma TF and TFPI levels in LA-positive patients were sig nificantly higher than levels in healthy volunteers (p < 0.01). In LA-positive patients, there were no significant differences in plasma TF and TFPI levels between patients with and without thrombosis. In patients with thrombosis, there was no signifi cant difference in the plasma TF level between LA-positive and LA-negative patients; however, the plasma TFPI level in LA- positive patients was significantly lower than that in LA- negative patients (p < 0.01). We also examined the TF pathway in human umbilical venous endothelial cells (HUVEC) incu bated with plasma of LA-positive patients, LA-negative pa tients, and healthy volunteers. TF activity was significantly higher (p < .05) in HUVECs incubated with the plasma of LA-positive patients than in cells incubated with the plasma of the other two groups (p < .01). However, there was no signifi cant difference in TFPI antigen levels among the media of HUVECs incubated with the plasma of all groups. The viability of HUVEC incubated with the plasma of LA-positive patients with thromboses, LA-positive patients without thromboses, and LA-negative patients with thromboses were significantly lower than that of HUVECs incubated with the plasma of healthy volunteers (p < .01). These findings suggest that abnormalities of the TF pathway plays an important role in the mechanism of hypercoagulability in LA-positive patients. LA may affect vas cular endothelial cells causing thrombogenesis.