CD40L induces tissue factor in human vascular smooth muscle cells in vitro. A: FACS analysis for human TF on vascular SMC, cultured 24 hours before the experiment in IT medium and subsequently for the indicated times with cell-membrane preparations of PMA-activated (50 ng/ml, 12 hours) T lymphocytes (left panels) or recombinant CD40L (10 μg/ml rCD40L; right panels) in the absence or presence of the α-CD40L mAb (α-CD40L, 10 μg/ml). Staining performed with control IgG is shown as lines. B: Lysates of human vascular SMC, previously cultured 24 hours in IT medium, then incubated for 24 hours with the respective concentrations of recombinant human CD40 ligand (rCD40L) in the absence or presence of the α-CD40L mAb (α-CD40L, 10 μg/ml), were analyzed for TF protein expression by ELISA (upper panel). TF activity was analyzed in membrane-preparations of human vascular SMC (lower panel), as described in Materials and Methods. Data shown are representative of three experiments performed with cells of different origins.