Medullary thymic epithelial cells

Specialized cells in the thymus involved in immune tolerance

Overview

Medullary thymic epithelial cells (mTECs) are a specialized type of cell found in the thymus, an organ that plays a crucial role in the development of the immune system. These cells are located in the medulla, the central part of the thymus, and are essential for the process of central tolerance, which prevents the immune system from attacking the body's own tissues.

Structure and Function

Thymic selection process

Medullary thymic epithelial cells are characterized by their unique ability to express a wide array of tissue-specific antigens (TSAs). This expression is regulated by the Autoimmune Regulator (AIRE) gene, which is crucial for the induction of central tolerance. By presenting these antigens to developing T cells, mTECs play a key role in the negative selection of autoreactive T cells, which are T cells that could potentially attack the body's own tissues.

The process of negative selection involves the elimination of T cells that strongly bind to self-antigens presented by mTECs. This ensures that only T cells that are tolerant to the body's own proteins are allowed to mature and enter the peripheral immune system.

Development

Medullary thymic epithelial cells develop from thymic epithelial progenitor cells during the process of thymic organogenesis. The differentiation of these progenitor cells into mTECs is influenced by various signaling pathways, including those mediated by the RANK, CD40, and lymphotoxin receptors. These signals are crucial for the proper development and function of mTECs.

Role in Autoimmunity

Defects in mTEC function or development can lead to autoimmune diseases, where the immune system mistakenly attacks the body's own tissues. For example, mutations in the AIRE gene can result in Autoimmune Polyendocrine Syndrome Type 1 (APS-1), a condition characterized by the failure of central tolerance and the development of multiple autoimmune disorders.

Related Pages

• Thymus
• T cell
• Central tolerance
• Autoimmune Regulator
• Autoimmune disease