CD19 has been extensively evaluated as a therapeutic target for recurrent or refractory B cell malignancy by chimeric antigen receptor T cell therapy, the single chain antibody sequence (scFv) against CD19 derived from a mouse hybridoma was widely employed. However, the immunogenicity of the mouse scFv sequence might be one of the reasons that CAR-T cells cannot persist in vivo for long. In present study investigators replace the mouse-derived scFv with a a humanized one and evaluate its safety and efficacy.