Differential effect of alpha-interferon and gamma-interferon on thromboplastin response in monocytes and endothelial cells.

Recombinant gamma-interferon (r gamma-IFN) has contrasting effects on thromboplastin (TPL) synthesis induced in monocytes (M) and endothelial cells by bacterial lipopolysaccharide (LPS), phorbol ester (TPA), and phytohaemagglutinin (PHA). In human umbilical vein endothelial cells (HUVEC) the induced thromboplastin response was significantly augmented by r gamma-IFN whereas the monocyte response was inhibited. Recombinant alpha-interferon (r alpha-IFN) had no effect on thromboplastin induction in endothelial cells but had a significant inhibitory effect on the TPL response in monocytes when LPS or LPS and cyclosporin A (CS) were used as inducing agents. Cyclosporin A, previously shown to enhance thromboplastin synthesis induced in monocytes, also contributes to a higher level of thromboplastin activity in endothelial cells. Its effect on monocytes was in most cases fully inhibited by r gamma-IFN (and also by r alpha-IFN when tested). gamma-Interferon and alpha-interferon alone had a weak stimulatory effect or none on thromboplastin synthesis in both cell types.