Exploring the role of Aire-expressing cells in shaping the thymic Treg repertoire and selection process

Autoimmunity can result from the loss of T-cell tolerance to self-antigens. Central tolerance that takes place in the thymus as well as suppression of conventional T cells by regulatory T cells (Tregs) in the periphery are both important mechanisms that prevent responses to self.  Autoimmune regulator (Aire) is a gene expressed by medullary thymic epithelial cells (mTECs) that is critical for the expression of tissue specific antigens (TSAs) and for thymic deletion of self-reactive T cells. Humans with the monogenic recessive disorder autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED) are defective in Aire expression and suffer from multi-organ autoimmunity. In addition to being critical for thymic deletion of self-reactive T cells, whether mTECs are important in the development of regulatory T cells and shaping the Treg TCR repertoire has not been directly examined. We hypothesize that mTECs are key in shaping the Treg repertoire due to previous studies that have suggested that a TCR specific for self-antigens (self-­reactivity) was the crucial requirement for thymic Treg cell differentiation and mTECs are a source of self-antigen in the thymus.  In order to test our hypothesis, we will utilize a limited TCR rearrangement mouse model that also allows us to deplete mTECS through the use of an Aire-DTR transgene. We will sequence the CDR3 region of the TCR alpha chain with and without depletion of mTECs to look for loss of certain TCR specificities. This approach will allow us to determine the contribution of mTECs to Treg selection.