Final answer:
Option 1). Thymic selection involves both negative and positive selection processes to ensure only T cells that can distinguish self from non-self mature. It destroys T cells that do not recognize self-MHC molecules, which is essential for preventing autoimmunity. The correct option is that thymic selection destroys T cells that do not recognize self-MHC molecules.
Step-by-step explanation:
T cells that are unable to recognize MHC self-molecules are eliminated by thymic selection. T cells go through a number of selection processes in the thymus during this process, making sure that only cells capable of differentiating between self and non-self molecules are permitted to develop and join the immune response. This guarantees central tolerance, which is necessary to stop autoimmune illnesses.
Stages of Thymic Selection:
Thymocytes, or immature T cells, that express both CD4 and CD8 are positively selected in the thymus cortex due to their capacity to attach to MHC molecules that present foreign antigens. Apoptotic cell death eliminates those that are unable to bind. We call this positive selection. Thymocytes that make it to the medulla must go through an additional selection process. Here, self-antigens are presented by antigen-presenting cells (APCs), and thymocytes that exhibit robust binding to these self-antigens are eliminated by apoptosis. This process, called negative selection, stops self-reactive T cells from maturing and developing into autoimmunity.
In summary, the correct option for the student's question is that thymic selection destroys T cells that do not recognize self-MHC molecules. This is crucial for the development of a safe and effective immune system.