Question at position 25 What usually happens to T cells that recognize self antigens?They develop into CD8 T cellsThey develop into T-helper cellsThey develop into CD4 T cellsThey are destroyedClear my selection

Question

BlackTom AI · Accepted Answer

Negative selection in the thymus eliminates T cells whose T-cell receptors bind self peptide–MHC complexes with high affinity, so self-reactive T cells are destroyed.

Relevant concepts: T cell development occurs in the thymus through stages (double-negative → double-positive → single-positive). Two key selection steps shape the repertoire: positive selection ensures T cells can recognize self MHC (low/moderate affinity), determining CD4 versus CD8 lineage based on MHC class II or class I restriction. Negative selection (central tolerance) removes thymocytes that bind self peptide–MHC too strongly, inducing apoptosis (clonal deletion). The autoimmune regulator (AIRE) allows thymic expression of tissue-specific antigens so many self-reactive clones are exposed and deleted. Peripheral tolerance (anergy, suppression by regulatory T cells) handles any self-reactive cells that escape deletion.

Step-by-step reasoning:
1. Thymocytes expressing TCRs interact with cortical epithelial cells for positive selection; those that bind self-MHC survive and become single-positive (CD4 or CD8) depending on whether they recognize MHC II or I.
2. Surviving thymocytes then encounter antigen-presenting cells displaying self peptides in the medulla. If TCR affinity for self peptide–MHC is high, intracellular apoptotic pathways are triggered.
3. High-affinity self-reactive clones undergo programmed cell death (clonal deletion), preventing them entering the peripheral immune system.
4. If negative selection is incomplete, peripheral mechanisms (anergy, Treg suppression) may still prevent autoimmunity.

Why the correct answer is correct: High-affinity recognition of self antigens during negative selection leads to deletion rather than differentiation into CD4/CD8 subsets. The multiple-choice distractors are incorrect because lineage decisions (CD4 vs CD8 or T-helper phenotype) are based on MHC class recognition and co-receptor expression during positive selection, not on self-reactivity. Therefore the correct choice, “They are destroyed,” matches the process of clonal deletion by negative selection. Final answer confirmed: They are destroyed.

Question at position 25 What usually happens to T cells that recognize self antigens?They develop into CD8 T cellsThey develop into T-helper cellsThey develop into CD4 T cellsThey are destroyedClear my selectionSingle choice

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