Question

The pre-TCR:

a. induces proliferation of the thymocyte.
b. induces the production of CD4 and CD8.
c. induces allelic exclusion.
d. A & B
e. A, B & C

Answer 1

The pre-T cell receptor (pre-TCR) is crucial in thymocyte development, causing cell proliferation, induction of CD4 and CD8, and maintaining TCR's specificity through allelic exclusion.

Step-by-step explanation:

Pre-TCR Function and Effects on Thymocytes

The pre-T cell receptor (pre-TCR) plays a pivotal role during the maturation of thymocytes in the thymus. When a thymocyte successfully rearranges the β-chain of its T-cell receptor (TCR), the pre-TCR is expressed on its surface. This expression triggers several crucial processes.

Firstly, the pre-TCR induces proliferation of the thymocyte, which is necessary to expand the pool of cells that will further differentiate into mature T cells. Secondly, signaling through the pre-TCR contributes to the induction of CD4 and CD8 co-receptor expression, which are characteristic of helper and cytotoxic T cells, respectively. Finally, the pre-TCR signals the thymocyte to halt rearrangement of the other TCR-α chain allele, a process known as allelic exclusion, ensuring that each T cell expresses only one type of TCR specificity.

In light of this information, the correct answer to the student's question would be 'e' which encompasses all three actions: inducing proliferation, inducing the production of CD4 and CD8, and inducing allelic exclusion.