Cytokine production and requirements during T-cell development

Cytokines have been presumed to play an important role during T-cell development, but until recently formal proof has been missing. Most cytokine-knockout mice show apparently normal intrathymic T-cell development. The exception to this is IL-7, as both IL-7 and IL-7Rα knockout mice show abnormally low thymic cellularity, making IL-7 the first cytokine shown to be necessary for normal intrathymic T-cell development.