FIG. 4.

With activated endothelial cells, the high level of IL-8 synthesis is further augmented. Cells were incubated with a triplet (A and B) or a doublet (C) of proinflammatory cytokines (as described in the legend to Fig. 2) for 24 h, and TLR-specific ligands then were added for 6 h. (A) In HMEC-1, IL-8 release is 10 times higher than that in resting cells and is further and significantly increased upon challenge with Pam₃Cys, poly(I:C), and LPS. Challenge with imiquimod leads to a significantly reduced level of IL-8 release in HMEC-1. (B) In HDMEC, activation with the cytokine triplet results in an increase of IL-8 formation by a factor of 7.5 (compared to that depicted in Fig. 3B), and no significant modulation of IL-8 production is seen after ligand addition. (C) When cells were incubated only with IL-1β and IFN-γ (1,000 U/ml each), an increase in IL-8 production of controls (column C) is seen that is similar to that described for panel B, but here a significantly increased IL-8 synthesis is seen after the addition of poly(I:C) and LPS (n = 3 to 4).