For all experiments, cells were seeded into 24-well plates (Nunc) at 10 6 /ml in complete RPMI 1640 except for DCs where GM-CSF (5 ng/ml) was also added. Cells were treated with medium only, rFhGST-S1 (10 mg) or LPS (Alexa; 100 ng/ml) for 18 h. Levels of total prostaglandin (PG), prostaglandin E2 (PGE2) and prostaglandin D2 (PGD2) were measured using the Cayman competitive EIA. The values were calculated using free data analysis software available at www.caymanchem.com/analysis/ eia. Data are presented as the mean 6 SEM following subtraction Sigma Class Glutathione Transferase of F. hepatica www.plosntds.org of medium controls and are representative of two separate experiments. Prior to experimentation, rFhGST-S1 was assessed for endotoxin (i.e. LPS) contamination using the Pyrogene endotoxin detection system (Cambrex).