Tissue factor expression during monocyte-macrophage differentiation.

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 VIIa-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.