DLL4 and congenital T-cell immunodeficiency: Consistent with this finding, our study demonstrated that FCPs triggered the gene expression of FoxN1 as well as FGF-7, IL-7, SDF-1, CCL25, and Dll4, strongly indicating that FCPs could be a promising therapeutical approach to promote thymopoiesis and the reconstitution of T-cell immunity in numerous clinical situations associated with T-cell deficiency.