The Final Stages of T Cell Development Occur in the Thymic

Multiple Choice

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