Effect of TTP-associated cytokines on survival of HUVECs and pulmonary and dermal MVECs. Apoptosis was assessed, as described in the legend to Figure 1, 18 hours after exposure of cells to buffer or various cytokines. IFN-γ, 0.1 ng/mL; TNF-α, 1 ng/mL; and TRAIL, 2 ng/mL.