Peripheral-antigen-expressing cells in thymic medulla: factors in self-tolerance and autoimmunity.

The thymus expresses many genes previously thought to be specific for cell types in other organs. Thus, insulin genes are expressed in rare cells of the thymic medulla. Thymus transplantation demonstrates a functional capability of such expression for self-tolerance induction. Correlative studies suggest that impaired thymic expression confers susceptibility to autoimmune disease.