The induction of B7-H3+LAG3+ CD4+ T cells from the bone marrow of pediatric B-ALL patients and their correlation with high cytotoxic granule expression suggests a pivotal role of CD4+ T cells in controlling tumor growth in B-ALL, characterized by high HLA class II expression (47–49). This evidence concerns the gene LAG3 and precursor B-cell acute lymphoblastic leukemia.