Scurfy mice which lacks functional Foxp3 transcription factor and CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cells, spontaneously develop autoimmune responses against skin, lung, liver and tail. However, many organs/tissues are spared from autoimmune attack. Here, we demonstrate that scurfy mice contain dormant autoimmune T cells that induced new diseases such as sialoadenitis, dacryoadenitis, pancreatitis, gastritis, intestinal inflammation, colitis, and myositis in RAG-1 KO mice. Inflammation in as many as 12 organs/tissues was consistently induced in individual recipients with scurfy lymph node cells containing as few as 1.25 x 10(6) CD4(+) T cells. Moreover, transfer of the multiple organ autoimmune diseases could be suppressed by as little as 0.5 x 10(6) CD4(+)CD25(+) Treg cells, mediated by inhibiting autoimmune T-cell expansion. Our study provides evidence for the presence of a large repertoire of autoimmune lymphocytes against various organs/tissues in scurfy mice as well as Treg cells in B6 mice capable of suppressing the expansion of these autoimmune lymphocytes. Various conditions that control the expression of autoimmune T cells are discussed.