IL-25 inhibits the LPS- and PGN-induced secretion of inflammatory cytokines. Blood CD14⁺ cells were isolated from 5 healthy volunteers and preincubated with medium or IL-25 (50 ng/mL) for 30 minutes then either left unstimulated (M = medium) or stimulated with LPS (100 ng/mL) or PGN (10 μg/mL) for a further 48 hours. Cytokine production was assessed by ELISA. LPS/PGN-treated cells versus LPS/PGN + IL-25–treated cells: *P < .01; **P = .03.