Figure 1.

Amplification of LPS, LTA and PGN-induced IL-6 production by histamine. HUVEC (1 × 10⁴ cells) were plated on to each of the wells of a 96-well culture plate and allowed to adhere for 18–20 hr. The monolayers were then incubated with the different doses of histamine (0·1–100 μm)(a), and histamine (10 μm) in the presence of LPS (1–1000 ng/ml) (b), LTA (0·1–10 μg/ml) (c), or PGN (1–100 μg/ml)(d). After a 24-hr incubation, IL-6 levels in the culture media were assayed by ELISA. Each value presented is the mean ± SD of quadruplicate determinations. The results presented are representatives of four independent experiments. An asterisk indicates P < 0·01 when compared to the value for the TLR agonist alone.