part of part of epithelial cell epithelial cell of thymus medullary thymic epithelial cell 2010-09-23T03:17:14Z mTEC BTO:0004563 https://cdn.humanatlas.io/digital-objects/2d-ftu/thymus-thymus-lobule/v1.3/assets/2d-ftu-thymus-thymus-lobule.png https://cellxgene.cziscience.com/cellguide/CL_0002365 An epithelial cell of the medullary thymus. This cell type expresses a diverse range of tissue-specific antigens. This promiscuous gene expression is a cell-autonomous property of medullary epithelial cells and is maintained during the entire period of thymic T cell output. Medullary thymic epithelial cells (mTECs) are distinct cells situated in the thymic medulla, a vital organ where T cells mature. mTECs are recognized by their unique appearance, characterized by large, plump cells with abundant cytoplasm and irregularly shaped nuclei. They inhabit a microenvironment closely interacting with various thymic cell types, including conventional dendritic cells and thymocytes. The primary function of mTECs revolves around negative selection of developing T cells, thus preventing autoimmune responses. mTECs allow developing T cells to recognize and be responsive to foreign antigens while remaining tolerant to the body's own tissues. They achieve this through a process called promiscuous gene expression where they express and display a vast array of self-antigens. This process is regulated by a transcriptional regulator called autoimmune regulator (Aire), which contributes to immunological self-tolerance. mTECs themselves have a self-renewing ability and sustain the continuous export of mature T cells. They also express a number of genes that encode for chemokines and other signaling molecules which draw in and retain developing T cells for the process of negative selection. The three-dimensional network formed by these cells provides a physical platform for such selection. Together, mTECs hold a critical place in the maintenance of immune homeostasis, demonstrating the conceptual links that exist between population of stromal cells, thymocytes development, tissue-restricted antigen expression, and negative selection. (This extended description was generated by ChatGPT and reviewed by the CellGuide team, who added references, and by the CL editors, who approved it for inclusion in CL. It may contain information that applies only to some subtypes and species, and so should not be considered definitional.) medulla of thymus