Summary
The present investigation was undertaken to explore the effect of platelets, tumor
necrosis factor (TNF) and phorbel ester [phorbol 12-myristate 13-acetate (PMA)] on
lipopolysaccharide (LPS)-induced tissue factor (TF) activity and TF antigen by using
Western blot and ELISA-techniques. LPS was found to induce correlating levels of TF
antigen and the activity in monocytes. TNF and PMA, when used alone, failed to induce
TF activity and the antigen in monocytes, but enhanced the LPS-induced TF activity
and the antigen by 2 to 3-fold. Addition of platelet rich plasma to isolated blood
cells enhanced the LPS-induced TF activity but not the antigen levels in monocytes.
In contrast to whole platelets, platelet lysates enhanced both LPS-induced TF activity
and the antigen. Granulocytes isolated from heparinized plasma incubated for 2 or
24 h with LPS alone or together with PMA, failed to generate TF antigen or the activity.
Although granulocyte preparations isolated from whole blood that was incubated for
24 h with LPS and PMA apparently possessed a significant amount of TF activity and
the antigen, this could be accounted for by trace levels of contaminating monocytes.
Upregulation of LPS-induced TF activity but not the antigen by platelets in the presence
of granulocytes suggests that the increased TF activity could be the result of PS
enrichment of monocytes by fusion or platelets with activated monocytes.
Key words
Tissue factor - granulocytes - monocytes - platelets - LPS