The induction of phospho-STAT5 after IL-7 stimulation was decreased in memory CD4+ T cells of some ICL patients, which correlated with a decreased expression of the IL-7Rα receptor chain (R = 0.74, p<0.005) and with lower CD4+ T cell counts (R = 0.69, p<0.005). This evidence concerns the gene CD4 and idiopathic CD4 lymphocytopenia.