Rolipram and VIP augment IL-10 production in a stimulus- and cell-specific manner. Human-monocyte-derived macrophages and T cells were plated out at a density of 1 × 105 cells per well in a flat-bottomed 96-well plate and pretreated with 10 μM rolipram and indicated concentrations of VIP for 1 hour prior to stimulation. Macrophages were stimulated with (a) 50 ng/ml PMA and 0.5 μg/ml ionomycin or (b) 1 ng/ml LPS, and T cells were stimulated with (c) 10 μg/ml concanavalin A and incubated for 24 hours at 37°C in a 5% CO2humidified atmosphere, after which time supernatants were harvested and assayed for IL-10 by ELISA. Data are mean cytokine levels in pg/ml of triplicate culture supernatants ± SD, showing a representative of n = 3 replicate experiments. **P < 0.01; ***P < 0.001. Iono, ionomycin; LPS, lipopolysaccharide; PMA, phorbol 12-myristate 13-acetate; Rol, rolipram; VIP, vasoactive intestinal peptide.