p53 is expressed in mTECS and promotes the expression of Tnfrsf11a (RANK). Conditional knockout of p53 in TECs results in reduced expression of RANK, a reduction in the overall number of mTECs, tissue-specific autoimmunity, and altered expression of TRAs. p53 is a critical modulator of mTEC homeostasis and the generation of a self-tolerant T-cell repertoire.