In the naive state, T cells are thought to require the common-gamma chain cytokines IL-7 and IL-15 for homeostatic survival mechanisms.
[2] The majority of human naive T cells are produced very early in life when the thymus is large and functional.
The subsequent decrease in naive T cell production due to involution of the thymus with age is compensated by so called "peripheral proliferation" or "homeostatic proliferation" of naive T cells which have emigrated from the thymus earlier in life.
Recognition by a naive T cell clone of its cognate antigen results in the initiation of an immune response.
Having adequate numbers of naive T cells is essential for the immune system to continuously respond to unfamiliar pathogens.