Question

In the thymus, T-cells are sorted to make sure they bind the

appropriate cell surface molecules and to ensure that they
do not recognize self peptides. Only ______% of immature T cells
that enter the thymus exit as mature T cells capable of
defending the host against intracellular infections.

Answer 1

Only 2% of thymocytes that enter the thymus exit as mature T cells. These cells undergo positive and negative selection to ensure self-tolerance and the aptitude to defend against foreign pathogens.

Step-by-step explanation:

In the thymus, T cells undergo a critical development process to ensure that they can effectively protect the body against intracellular infections without causing harm to the body itself. This process includes positive selection, where T cells must recognize major histocompatibility complex (MHC) molecules, and negative selection, where T cells that strongly bind to self-antigens are eliminated through apoptosis. Only about 2% of immature T cells, known as thymocytes, that enter the thymus will exit as mature T cells capable of defending the host.

Following their exit from the thymus, these mature naïve T cells circulate through the lymphatic system and reside in secondary lymphoid organs awaiting activation by antigen-presenting cells (APCs). This careful curation of T cells is essential for maintaining self-tolerance and preventing autoimmune responses, ensuring that the immune system targets foreign pathogens effectively while preserving the body's own cells.