The strict control of the T-cell receptor repertoire is essential for prevention of autoimmune diseases. The repertoire of T cells is primarily formed in the thymus through positive and negative selection. The risk of an incomplete removal of autoreactive T cells necessitates additional means to maintain peripheral tolerance. There is increasing evidence that the interferon (IFN)-γ-inducible lysosomal thiol reductase (GILT) allows peripheral tolerance to a melanocyte differentiation antigen by induction of specific regulatory T cells.