What is the underlying genetic defect in APECED? Explain why it leads to a reduction in self-tolerance
What will be an ideal response?
The underlying genetic defect is in a gene encoding a protein called AIRE (autoimmune regulator). This is a transcription factor that, when working normally, causes several hundreds of proteins otherwise expressed only in particular peripheral tissues to be expressed by medullary epithelial cells in the thymus. This induces the negative selection of T cells specific for these proteins and their deletion from the T-cell repertoire. The T cells emerging from the thymus are therefore tolerant to a large number of antigens found primarily on organs and tissues elsewhere in the body. When AIRE is defective and these proteins are not expressed in the thymus, the population of naive T cells that develops will contain T cells reactive against these antigens of peripheral tissues.
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