Objective To investigate the effects of nuclear factor kappa B decoy oligodeoxynucleotides ( NF-κB decoy ODN) transfection on biological characteristics of mature dendritic cells ( mDCs) in mice. Methods Immature DCs were harvested from Balb / c mice bone marrow, followed by the incubation with antigen OVA and LPS, and mature DCs were evaluated by the expressions of CD11c and MHC-Ⅱ detected by FACS. Mature DCs were transfected with NF-κB decoy ODN and the changes of NF-κB activity after the transfection were detected by EMSA. The expressions of the costimulatory molecules( CD40,CD80 and CD86) on DCs were detected by FACS and the proliferation of T cells was tested by mixed lymphocyte reaction( MLR) . Results The mature DCs were cultured successfully. The NF-κB activity of NF-κB decoy ODN transfected DCs was decreased significantly( P lt; 0. 05) . There was no difference in the expressions of CD40 and CD80, but the expression of CD86 was decreased significantly in NF-κB decoy ODN transfection group( P lt; 0. 05) . MLR test showed that the proliferation of T lymphocyte cells was inhibited by NF-κB decoy ODN transfected DCs, but was stimulated bly by the DCs of other groups. Conclusions Mature DCs transfected with NF-κB decoy ODN could inhibit the proliferation and activation of antigenspecical T cells, which was probably related to the down-regulation of CD86 on DCs. This modified DCs might be a promising vaccine for the treatment of asthma in the future.