Analysis of tolerance induction using immunosuppresslve dendritic cells in transplantation

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CD4+CD25+ regulatory T cells are selected in the thymus to control autoreactive thymic escapees preventing autoimmunity that can not be achieved by negative selection or deletion alone, thus playing an important role in the maintenance of immunological homeostasis. Not only significant in preventing autoimmunity, CD4+CD25+ regulatory T cells have also been shown to be involved in allograft tolerance in organ transplantation. Recent studies suggest that Foxp3, which encodes Scurfin, a member of the forkhead family of transcriptional regulators, is the key regulatory gene for the development of CD4+CD25+ regulatory T cells. We have formerly introduced two lines of HLA class I transgenic mice valuable to elucidate the role of HLA class I molecules in transplantation biology. Here, using a heterotopic cardiac transplantation model, we show that intrathymic inoculation of donor HLA class I derived synthetic peptide results in elevation of Foxp3 level in graft infiltrating lymphocytes and acceptance of the vascularized allograft. In addition, we demonstrate by adoptive transfer experiments that CD4+CD25+ regulatory T cells obtained following intrathymic inoculation of the synthetic peptide effectively induce graft specific tolerance without preconditioning of the recipient or use of additional immunosuppressive drugs. The study provides evidence suggestive of novel therapeutic option with CD4+CD25+ applicable to clinical transplantation.