Macrophage-colony stimulating factor (M-CSF)-primed monocyte-derived macrophages, plated at a density of 1×105 cells/well, were stimulated by 1 ng/ml LPS in the presence or absence of 10-6M VIP. IL-10 modulation of VIP regulation of TNF-α production was assessed by addition of 10 μg/ml neutralising anti-IL-10 (9D7) or 10 ng/ml IL-10. Results with an isotype-matched control antibody did not differ significantly from the control sample presented in this table. The resulting cultures were incubated for 24 hours at 37°C in a 5% CO2 humidified atmosphere, after which time supernatants were harvested and assayed for TNF-α by ELISA. Data are mean TNF-α levels in pg/ml and percentage suppression by VIP in parentheses of triplicate culture supernatants ± SD, showing a representative of n = 3 experiments. LPS, lipopolysaccharide; TNF-α, tumour necrosis factorα; VIP, vasoactive intestinal peptide.