SummaryTissue 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.

Yeast vectors suitable for high‐level expression of heterologous proteins should combine a high copy number with high mitotic stability. The pMIRY integrative vector system, based upon targeted integration into the yeast rDNA locus, developed in our laboratory satisfies these criteria. However, insertion of a (foreign) gene drastically reduced its mitotic stability of the resulting vector in comparison to its parent. In this paper we have investigated a number of possible reasons for this reduction in stability. The results demonstrate that plasmid size is an important, but not the only, determinant of mitotic stability. Stable maintenance is only observed when the complete plasmid has a size no larger than that of the rDNA unit (9·1 kb). In addition stability depends upon the nature of the rDNA fragment present in the plasmid, required for targeting its integration. On the other hand, it turned out to be irrelevant for mitotic stability whether the heterologous gene was expressed or not. These findings will be important in the design of a pMIRY vector suitable for industrial production of heterologous proteins.