Similar to IL-29, IL-28A and IL-28B enhance R848-induced IL-12p40, TNF, and IL-10 production by human monocyte-derived macrophages. Monocyte-derived macrophages were pretreated with IL-28A, IL-28B, and IL-29 (all 100 ng/mL) for 5 hours, and then further stimulated with R848. The levels of IL-12p40, TNF, and IL-10 in the supernatants were determined by ELISA. The values depicted show the means ± SE from 7 independent experiments.