Final answer:
The two-stage thymic selection process for T cells results in clonal deletion, which involves the elimination of self-reactive T cells through apoptosis, ensuring central tolerance and prevention of autoimmune diseases.B. clonal deletion.
Step-by-step explanation:
The two-stage thymic selection process for selecting self-tolerant, antigen-reactive T cells culminates in clonal deletion. This physiological mechanism is responsible for the removal of T cells that are capable of recognizing self-antigens, which is vital for preventing autoimmune diseases.
The initial stage takes place in the thymus cortex and involves positive selection, which selects thymocytes that can properly interact with the Major Histocompatibility Complex (MHC) molecules. Thymocytes that fail to interact properly are not stimulated and thus eliminated through apoptosis. The subsequent stage known as negative selection takes place in both the cortex and medulla, and it ensures the elimination of thymocytes that strongly react to self-antigens to promote central tolerance. This process is also essential for preventing self-reactive T cell maturation and entry into the peripheral bloodstream. The clonal deletion process occurs through apoptosis, distinguishing it from mechanisms like allelic exclusion or somatic hypermutation, which are associated with B cells.