It is important to note that the Rag1 or Rag2 deficiency, or the Foxn1 deficiency of nude mice led to absence of T cells but also affect the other cell types such as loss of B cells in Rag1/2 knockout mice, and impairment of multiple organs beyond T cell deficiency in Foxn1 deficient mice and patients [51,52]. Here, RAG2 is linked to congenital T-cell immunodeficiency.