CD19 and acute lymphoblastic leukemia: Even though the development of CAR-T cells has been ongoing for almost three decades [16], the first CAR-T therapy targeting CD19 antigen on cancer cells, Kymriah, was approved by the U.S. Food and Drug Administration (FDA) in 2017 for the treatment of children or young adults with B cell precursor Acute Lymphoblastic Leukemia (ALL).