The p72syk inhibitor piceatannol inhibits LAG-3–induced up-regulation of DC surface molecules and LAG-3–induced down-regulation of antigen uptake by DCs. Peripheral blood monocytes were differentiated into immature DCs with GM-CSF and IL-4 for 7 days. Cells were then treated in the presence of GM-CSF and IL-4 with 10 μg/mL IgG1 or LAG-3Ig or preincubated for 2 hours with the p72syk inhibitor piceatannol prior to treatment with LAG-3Ig. After 24 hours of incubation, surface expression of the indicated markers was analyzed by flow cytometry (A). Cells were incubated with BSA-FITC for 30 minutes at 4°C or 37°C, and the BSA uptake was determined by FACS analysis (B). Results are representative of 3 independent experiments.