Question

Immediately after positive selection

a. the thymocyte reaches maturity and is exported to the periphery
b. RAG proteins are degraded and are no longer synthesized
c. receptor editing commences to eliminate reactivity against self antigens
d. the developing thymocyte acquires a double-negative phenotype
e. expression of pTα is repressed.

Answer 1

After positive selection in T cell development, negative selection occurs where developing thymocytes that bind to self-antigens are eliminated through apoptosis, contributing to the prevention of an autoimmune response.

Step-by-step explanation:

The student's question pertains to the events that occur immediately after positive selection in T cell development within the thymus. Positive selection ensures that developing thymocytes can bind to major histocompatibility complex (MHC) molecules. After positive selection, the next crucial step is negative selection, where self-reacting thymocytes that bind to self-antigens presented by antigen-presenting cells (APCs) are induced to undergo apoptosis. This process is essential for establishing central tolerance and preventing autoimmunity. Therefore, the correct answer is that receptor editing does not commence; rather, thymocytes that react against self-antigens are removed, and pTα expression is not particularly relevant to this phase of T cell maturation.