Final answer:
The false statement about positive selection is that it occurs in the medulla of the thymus; positive selection takes place in the cortex. Cortical epithelial cells interact with double-positive thymocytes, selecting those which can bind to self-MHC class I and II and self-peptides.
Step-by-step explanation:
The false statement about positive selection is that it takes place in the medulla of the thymus. Positive selection actually occurs in the cortex of the thymus. During this process, cortical epithelial cells interact with double-positive thymocytes, which express both CD4 and CD8 markers. These thymocytes that successfully bind with self-MHC class I and II and self-peptides are selected to move further in the T cell maturation process.
Thymocytes that do not bind appropriately with self-MHC are eliminated through apoptosis. This ensures that only those T cells that can recognize foreign antigens presented on the MHC molecules of the body, without attacking the body's own tissues, are allowed to mature and exit the thymus.