During T-cell development in the thymic cortex, what is the outcome of positive selection?
Answer and explanation
Correct answer: C. Immature thymocytes that can recognize self-MHC molecules with moderate affinity survive
Positive selection occurs in the thymic cortex. Double-positive (CD4+ CD8+) thymocytes that express T-cell receptors capable of binding self-MHC molecules on cortical epithelial cells with low-to-moderate affinity receive survival signals (MHC restriction). Those with no affinity die by neglect, and those with dangerously high affinity for self-antigens are eliminated in the thymic medulla during negative selection (central tolerance).
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