T cell selection or thymopoiesis is crucial for the proper functioning of the immune system. This process occurs in the thymus and is comprised of two phases – positive selection and negative selection. Both are equally important for the proper development of thymocytes into mature T cells that are capable of killing foreign pathogens without attacking the body’s own healthy cells, causing autoimmune diseases.

T cell selection ensures that the immune system can effectively defend the body against infections while avoiding harmful attacks on its own tissues. Without proper T cell selection, the immune system would be less capable of recognizing and responding to threats, making the body more susceptible to infections and autoimmune disorders.