Intradermal inoculation of plasmids expressing antigens that contain MHC class I-restricted epitopes leads to the induction of specific CD8⁺ cytotoxic T lymphocytes (CTL). The role of in situ transfected antigen-presenting cells (APC) in the priming of specific CTL subsequent to intradermal DNA immunization was investigated using a plasmid (NPV1) expressing the nucleoprotein (NP) of influenza virus that contains a nuclear targeting signal and a dominant class I/K^d-restricted epitope. Inoculation of NPV1 leads to in situ transfection of MHC class II⁺ and class II^– cells, as revealed by the nuclear localization of NP. Between 2 and 3% of MHC class II⁺ and class II^– cells with the ability to migrate out of the epidermis expressed NP. Upon adoptive transfer into naive recipients, class II⁺ migratory cells recovered from the area inoculated with NP-expressing plasmid were significantly superior regarding the ability to prime virus-specific CTL as compared to MHC class II^– cells. Together, these results are consistent with the role of local dendritic cells loaded with antigen in the priming of CTL by intradermal DNA immunization.