In acute lymphoblastic leukemia (ALL), nearly half the patients undergoing FDA-approved CD19/CART cell therapy suffered from cytokine release syndrome, which is associated with hyperproduction of cytokines and massive T-cell expansion (hemophagocytic lymphohistiocytosis and macrophage activation syndrome), potentially leading to life-threatening capillary leak with hypoxia and hypotension [40]. This evidence concerns the gene CD19 and macrophage activation syndrome.