The final stages of T cell development occur in the thymic medulla, after the developing cells become CD4 or CD8 single-positive. One important change that occurs during this final maturation is:
A) The down-regulation of the pre-T-cell receptor $\alpha$ (pre-T$\alpha$) chain protein
B) The up-regulation of genes encoding effector cytokines and cytolytic effector proteins
C) The increased susceptibility to T-cell receptor-induced apoptosis
D) The loss of susceptibility to T-cell receptor-induced apoptosis
E) The up-regulation of signaling proteins required for T cell activation

Question

Quizplus · Accepted Answer

The final maturation stage of CD4 or CD8 single-positive T cells in the thymic medulla is characterized by the loss of susceptibility to T-cell receptor (TCR)-induced apoptosis. This process is important for ensuring that mature T cells do not react to self-antigens when they encounter them in the periphery. A small percentage of T cells undergo apoptosis during this process, which is regulated by signals from both the TCR and the cytokine environment in the thymic medulla. Therefore, option D is the correct choice.

The Final Stages of T Cell Development Occur in the Thymic