Type I interferon induction was recently found in recombinant Ad-treated human cells, especially in pDCs [46, 89] and in monocyte-derived DCs in the present study. Moreover, this response was observed also in patients administered with recombinant adenoviral vectors [42, 90] . Since as shown here, IFN-a pre-treatment is capable of increasing susceptibility to LPS of human DCs in vitro, we assume that Ad-induced IFN-ab can induce LPS hypersensitivity in humans in vivo. Undesirable complications mediated by IFN-ab can occur not only during gene therapy, but also in immunocompromised patients where Ads are major pathogens [1] . Our finding that blocking SAPK/ JNK signaling inhibits the IFN-ab response to Ads, is of potential interest for prevention or treatment of the direct and indirect adverse effects of IFN-ab in Ad gene therapy.