The attenuating signal was similar to the gain-of-function mutation of IL-7 receptor α chain (IL-7Rα) that led to the dimerization of IL-7Rα in some lymphoblastic leukemias patients.37,38 STAT3 is pivotal in developing terminally differentiated effector CD8+ T cells by facilitating the expression of genes associated with effector functions.39 Consequently, sustained activation of STAT3 may potentially induce terminal differentiation and exhaustion in T cells. This evidence concerns the gene CD8A and acute lymphoblastic leukemia.