Tissue factor activity of cultured human lymphocytes

Potent procoagulant activity develops in human lymphocytes during mixed culture, preceding the cell multiplication. This activity has the same characteristics as that of tissue factor. The membrane support of the activity binds factor VII, leading to the formation of factor X activator. The same observation is made when lymphocyte culture is made without antigenic stimulation, demonstrating that "in vitro" culture alone is able to endow lymphocytes with tissue factor activity. The mechanism of this non-specific stimulation remains to be elucitaded.