Development of tissue factor activity in mononuclear cells cultured in vitro

Tissue factor activity was detected in human mononuclear cells cultured with E. coli endotoxin in vitro. The effecient concentration of endotoxin inducing significant tissue factor development was in excess of 10(-3) microgram/ml, and a dose response type relationship was seen between them. The activity developed after culturing for 2 hr and increased up to 6 hr, and thereafter no significant increase was observed. Although the activity was detected both in cell extract and on cell surface, the main activity seemed to exist on the cell surface. No correlation was observed between the synthetic rate of nucleic acid and the rate of development of the activity. Although the activity was detected also in a granulocyte preparation, it was significantly less than that in mononuclear cells. The development of activity was observed when lymphocytes were cultured in RPMI 1640 medium, MEM, and in autologous serum. However, the activity was not observed when cultured in Hanks solution and PBS, in which the main difference from RPMI was the absence of amino acids, and in autologous serum containing sodium citrate which was added for elimination of Ca++ from serum. Moreover, actinomycin D suppressed the development of activity, and the same was noted at low culture temperature. These results suggest that some metabolic change of the cell membrane triggered by endotoxin may induce the development of tissue factor in cells.