Summary
Tissue factor (TF), the high affinity receptor and cofactor of factor VII, is considered
as the main procoagulant in stimulated monocytes and macrophages. We studied the effect
of longterm culture (differentiation) on “spontaneous” and induced (LPS) expression
of TF (mRNA, antigen, cell surface associated Vlla-cofactor activity) in isolated
human monocytes.
TF was expressed transiently in monocytes cultured on Teflon membranes (suspension
monocytes, Mo-S) and on plastic dishes (adherent monocytes, Mo-A), reaching maximal
levels between days 3 and 5. Increased expression of TF was accompanied by increased
stable expression of macrophage specific markers (CD71, the mannose receptor, the
scavenger receptor).
Bacterial lipopolysaccharide (LPS) induced (additional) TF mRNA, antigen, and activity
in both Mo-S and Mo-A. In Mo-S and Mo-A of days 3 to 5, the period in which there
was “spontaneous” expression of TF, TF response to LPS was considerably lower.
It is concluded that during monocyte-macrophage transition, TF is “spontaneously”
and transiently expressed and that with respect to TF induction the responsiveness
of the cells to LPS is maintained.