T-cell regeneration: All repertoires are not created equal

The importance of the thymus for T-cell development is a central tenet of modern immunology, but thymic-independent T-cell generation has also been described. Recent human studies have shown that the balance between thymic-dependent and thymic-independent pathways of T-cell regeneration is primarily determined by age, and that thymic-independent pathways are generally inadequate for restoration of host immunocompetence.