Induction of HO-1 affects cytokine expression in rat and human DCs. (A) ELISA was used to assess the production of IL-12 p40, IL-6, TNF-α, and IL-10 in the supernatants of rat BMDCs treated or not with SnPP or CoPP for 2 hours, cultured for 16 hours, and then for a further 24 hours in the presence or absence of LPS. Induction of HO-1 inhibited expression of IL-12 p40, TNF-α, and IL-6 in DCs but did not alter IL-10 secretion. Horizontal bars represent the mean of individual values. Statistical significance compared to LPS-treated cells is indicated as ^*P < .001. (B) ELISA was used to assess the production of IL-12 p70 and IL-10 in the supernatants of human DCs treated or not with SnPP or CoPP for 2 hours, cultured for 16 hours, and then for a further 24 hours in the presence or absence of LPS. Induction of HO-1 inhibited expression of IL-12 p70 but did not alter IL-10 secretion. Data presented are mean ± SD of triplicate analysis of one experiment and are representative of 3 independent experiments. Statistical significance compared to LPS-treated cells is indicated as ^*P < .01.