Task: Class Definition Understanding (ontology: Sciences/Biology)

Which of the following definitions best describes 'cortical thymic epithelial cell'?

A. 2nd digit of the hind autopod.
B. 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.
C. An epithelial cell of the cortical portion of the thymus. Epithelial cells in this region are required for positive selection of CD8-positive T cells.
D. An epithelial cell with a well defined Golgi apparatus that makes up the continuous layer of cells bordering the thymic tissue beneath the capsule.

Answer: An epithelial cell of the cortical portion of the thymus. Epithelial cells in this region are required for positive selection of CD8-positive T cells.