By the end of the study, mice receiving untransduced or anti-CD19 CART cells required euthanasia due to tumor progression and two other mice (one in NC group and one in IL-21 group) were sacrificed due to graft-versus-host disease (GVHD)-like symptoms which can be associated with this model system, although their tumors had regressed. This evidence concerns the gene IL21 and graft versus host disease.