Question

Thymocytes that are not positively selected

a. undergo genetic reprogramming and differentiate into a different cell type
b. are exported to the periphery, where they are phagocytosed by macrophages
c. make up about 98% of developing thymocytes and die by apoptosis in the thymic cortex
d. are eliminated because of their reactivity with self antigens
e. try out different β chains to acquire reactivity with self-MHC molecules.

Answer 1

Thymocytes that are not positively selected undergo apoptosis in the thymic cortex, which is part of the process known as negative selection, essential for ensuring self-tolerance by eliminating self-reactive T cells.

Step-by-step explanation:

The subject of the question is the process by which thymocytes that are not positively selected are dealt with during T cell development. This process takes place in the thymus and is essential for the development of the immune system. Negative selection plays a critical role in ensuring self-tolerance by eliminating thymocytes that have a high affinity for self-antigens. These self-reactive thymocytes are induced to undergo apoptosis (programmed cell death) in the thymic cortex, preventing them from becoming mature T cells that could potentially cause autoimmune disease.

To answer the student's question, thymocytes that are not positively selected, which make up about 98% of developing thymocytes, die by apoptosis in the thymic cortex. This is a vital component of central tolerance, a process where potential self-reacting T cells are removed before they can enter the bloodstream and cause harm to the body. The remaining thymocytes that survive these selection processes migrate to secondary lymphoid organs where they become mature naïve T cells, ready to encounter antigens presented by APCs.