Abstract: Objective To observe the functional changes of dendritic cells (DCs) infected in vitro by 3 recombinant adenoviruses encoding Her2/neu extracellular first-receptor domain (Her2-ECDs), full-length extracellular domain (Her2-ECD), and extracellular and transmembrane domain (Her2-TM) proteins (rAdHer2-ECDs, rAdHer2-ECD and rAdHer2-TM, respectively). Methods The expressions of the target proteins were detected with Western blotting. The level of both interleukin (IL)-12 in the supernatant of in vitro cultured DCs infected with recombined adenoviruses and interferon γ(IFN-γ) in the supernatant of the lymphocyte populations co-cultured with DCs were determined by enzyme-linked immunosorbent assay (ELISA). The capacity of the DCs to stimulate allogeneic T lymphocyte proliferation was assessed by mixed lymphocyte reaction, and the activity of cellular toxic T lymphocytes (CTL) were investigated by MTT assay. Results Her2-ECDs, ECD and TM proteins were detected in the transfected DCs. Compared with the untransfected DCs, more abundant IL-12 production was detected in the supernatant of the DCs 5 days after transfection, but the IL-12 level showed no significant difference between the DCs infected with the 3 recombinant adenoviruses. IFN-γ production increased gradually with passage of the time following DC-stimulated lymphocyte proliferation irrespective of infection of the DCs, and only the DCs infected with rAdHer2-TM seemed to result in significant difference in DC-mediated allogeneic T lymphocyte proliferation. The killing of breast cancer cell line with Her2 overexpression was more efficient with infected DCs priming autologous T lymphocyte to generate CTL than with uninfected DCs and those modified by SK-OV-3 cell fragment. CTL activity induced by rAdHer2-TM-infecetd DCs was the strongest, and breast cancer cell-killing activity was more efficient against cell line with Her2/neu-overexpression. Conclusion The DCs infected with the recombinant adenovirus encoding Her2/neu extracellular and transmembrane domains show enhanced anti-tumor effect and induce Her2/neu-specific CTL activity.