Presentation of self antigen to regulatory T cells. If self antigen is presented to self-reactive T cells in the absence of CD4⁺CD25⁺ regulatory T cells, self-reactive T cells can expand and induce autoimmunity (upper portion of figure). As little as 6 days of autoantigen presentation to regulatory T cells is sufficient to induce profound suppressive function of these cells, leading to inhibition of autoantigen reactive T cells and thereby preventing disease.