Immature dendritic cells (iDCs) have been shown to be able to induce peripheral T-cell tolerance through distinct pathways. Here, we investigated the tolerogenic property of recipient iDCs whose maturation was arrested by a dominant negative mutant of inhibitor of nuclear factor kappa-B kinase 2 (dnIKK2) gene. We found that dnIKK2-iDCs presented a typical semi-mature morphology and expressed lower levels of CD80 and CD86, slightly higher MHC-II than untransfected iDCs. The expression of these molecules had no significant change even dnIKK2-iDCs were pulsed by donor antigen. In primary mixed leukocyte reaction (MLR), dnIKK2-iDCs exhibited impaired ability to stimulate allogeneic T-cells, but induced CD4(+)CD25(-) T-cell formation. In co-culture MLR, these CD4(+)CD25(-) T-cells suppressed T-cell alloreaction in an antigen-specific manner. Besides, CD4(+)CD25(-) T-cells inhibited IL-2 and IFN-γ release, whereas promoted IL-10 and TGF-β secretion. These data suggested recipient dnIKK2-iDCs could maintain peripheral tolerance through down-regulating costimulatory molecule expressions and inducing CD4(+)CD25(-) T-cell formation.