Foxn1 also promotes the downstream transcription of genesimplicated in thymus organogenesis.73 Inthe absence of Foxn1 expression, the intrathymiclymphopoiesis of affected patients is completely blocked,74,75 leading to severe primary T-cell immunodeficiency,76−78 which is also observed on the Foxn1–/– mice model.79Lyl1 hasbeen recognized as a critical component responsible for orchestratinglymphoid specification in multipotent bone marrow progenitors. Here, FOXN1 is linked to T-cell immunodeficiency.