Medullary thymic epithelial cells: deciphering the functional diversity beyond promiscuous gene expression.

Within the thymus, cortical and medullary thymic epithelial cells (cTECs and mTECs, respectively) provide unique microenvironments for the development of T cells that are responsive to diverse foreign antigens while self-tolerant. Essential for tolerance induction, mTECs play a critical role in negative selection and T regulatory cell differentiation. In this article, we review the current knowledge on the functional diversity within mTECs and discuss how these novel subsets contribute to tolerance induction and are integrated in the complex blueprint of mTEC differentiation.