Question

Once a thymocyte has productively rearranged a β-chain gene, which of these event(s) can occur subsequently? (Select all that apply.)

a. β binds to pTα and is expressed on the cell surface with the CD3 complex and ζ chain.
b. Rearrangement of β-, γ-, and δ-chain genes ceases as a result of the suppression of expression of RAG-1 and RAG-2.
c. The pre-T cell proliferates and produces a clone of cells all expressing an identical β chain.
d. Expression of CD34 and CD2 gives rise to double-positive thymocytes.
e. α-, γ-, and δ-chain loci rearrange simultaneously.

Answer 1

After a thymocyte successfully rearranges its β-chain gene, it binds with pTα on the surface, the pre-T cell proliferates, and gene rearrangements for β-, γ-, and δ-chains cease due to suppression of RAG-1 and RAG-2.

Step-by-step explanation:

Once a thymocyte has productively rearranged a β-chain gene, several events can occur. These include:

• β binds to pTα and is expressed on the cell surface with the CD3 complex and ζ chain.
• The pre-T cell proliferates, producing a clone of cells all expressing an identical β chain.
• Rearrangement of β-, γ-, and δ-chain genes ceases as a result of the suppression of expression of RAG-1 and RAG-2, which are necessary for the recombination process.

The events lead to the formation of cell populations with specific β-chain sequences. This process is part of the immune system's method to create a diverse repertoire of T cell receptors, necessary for the recognition of a vast array of antigens. The process described is similar to the genetic rearrangement in B cells, where the variable region of their receptors is made up of V, D, and J (heavy chain) or V and J (light chain) segments, providing millions of unique antigen-binding sites.