Administration of anti-CTLA4 blocking antibody (αCTLA4) had no effects in control mice but further and significantly improved ALL inhibition in IFN mice, suggesting an immune contribution to the observed response in IFN mice (IFN vs IFN + αCTLA4 **p < 0.01, IFN vs CTRL + αCTLA4 *p < 0.05, IFN + αCTLA4 vs CTRL + αCTLA4 ****p < 0.0001, CTRL vs CTRL + αCTLA4 n.s., nonparametric rank-based method for longitudinal data in factorial experiments). This evidence concerns the gene CTLA4 and acute lymphoblastic leukemia.