Although dendritic cell (DC) is unrivalled for the initiation of immune responses, the immuno-modulatory capacity of chemically fixed DC is not thoroughly evaluated. We monitored the tolerogenic capacity of chemically fixed DCs using allogeneic heart transplantation. Bone marrow progenitors were differentiated into immature DCs by in vitro culture with low dose GM-CSF, and CD86 high cells were removed at the end of the culture. chemically fixed DCs were made by the chemical fixation of immature DCs, and were injected intravenously into recipient mice 14 days before allogeneic heart transplantation. Chemically fixed DCs markedly prolonged graft survival in the MHC-I/II mismatch cardiac transplantation (B6 ��� B10.A ; MST 12.5 vs. > 70 days). T cells that encountered chemically fixed DC, revealed the attenuated apoptotic cell death and the inactivated phenotypes after allogeneic heterotropic heart transplantation. After heart transplantation, in vitro allogeneic T cell responses markedly attenuated when chemically fixed DCs were treated. Furthermore, when DCs from IL-10-/- mice were treated, in vitro T cell response were higher than from IL-12-/- mice. We suggest that the maturation-resistant DC may handle the peripheral T cell tolerance, and may have therapeutic potential for allogeneic transplantation.