CD4 and lymphoproliferative syndrome: Such GA-binding protein (GABP), the Etsfamily transcription factor, has been identified as essential forthe upregulation of IL-7Rα in immature DN thymocytes.67 Forkhead box O (FOXO) 1 transcriptionfactor deficiency resulted in a severe defect in IL-7Rα expression.68FOXO1-deficient mice can developa lethal inflammatory disorder and lead to an elevation in CD4 andCD8 single-positive (SP) thymocyte populations.69,70FOXO3a-deficient mice lead tomild lymphoproliferative syndrome and the formation of inflammatorylesions.