Whether a similar approach can restore TEC functionality in older individuals, in which the residual thymic tissue is limited (121) remains an avenue to be explored. On the other hand, it is highly unlikely that the same approach can mediate beneficial effects in restoring thymic function and the process of T-cell development in patients with intrinsic genetic defects which alter TEC function, for instance as a consequence of FoxN1 deficiency in patients affected by the nude/severe combined immunodeficiency. The gene discussed is FOXN1; the disease is immunodeficiency disease.